oc-csl: Implement `csl' citation processor

* etc/csl/chicago-author-date.csl:
* etc/csl/locales-en-US.xml:
* lisp/oc-csl.el (csl): New files.
* etc/Makefile (ETCDIRS): Register new files.

etc/Makefile

@@ -1,4 +1,4 @@
-ETCDIRS = styles schema
+ETCDIRS = styles schema csl
 -include local.mk	# optional local customization
 
 .NOTPARALLEL:	# always run this make serially

etc/csl/chicago-author-date.csl

@@ -0,0 +1,644 @@
+<?xml version="1.0" encoding="utf-8"?>
+<style xmlns="http://purl.org/net/xbiblio/csl" class="in-text" version="1.0" demote-non-dropping-particle="display-and-sort" page-range-format="chicago">
+  <info>
+    <title>Chicago Manual of Style 17th edition (author-date)</title>
+    <id>http://www.zotero.org/styles/chicago-author-date</id>
+    <link href="http://www.zotero.org/styles/chicago-author-date" rel="self"/>
+    <link href="http://www.chicagomanualofstyle.org/tools_citationguide.html" rel="documentation"/>
+    <author>
+      <name>Julian Onions</name>
+      <email>julian.onions@gmail.com</email>
+    </author>
+    <contributor>
+      <name>Sebastian Karcher</name>
+    </contributor>
+    <contributor>
+      <name>Richard Karnesky</name>
+      <email>karnesky+zotero@gmail.com</email>
+      <uri>http://arc.nucapt.northwestern.edu/Richard_Karnesky</uri>
+    </contributor>
+    <contributor>
+      <name>Andrew Dunning</name>
+      <email>andrew.dunning@utoronto.ca</email>
+    </contributor>
+    <category citation-format="author-date"/>
+    <category field="generic-base"/>
+    <summary>The author-date variant of the Chicago style</summary>
+    <updated>2017-10-12T12:00:00+00:00</updated>
+    <rights license="http://creativecommons.org/licenses/by-sa/3.0/">This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 License</rights>
+  </info>
+  <locale xml:lang="en">
+    <terms>
+      <term name="editor" form="verb-short">ed.</term>
+      <term name="container-author" form="verb">by</term>
+      <term name="translator" form="verb-short">trans.</term>
+      <term name="editortranslator" form="verb">
+        <single>edited and translated by</single>
+        <multiple>edited and translated by</multiple>
+      </term>
+      <term name="translator" form="short">trans.</term>
+    </terms>
+  </locale>
+  <macro name="secondary-contributors">
+    <choose>
+      <if type="chapter paper-conference" match="none">
+        <group delimiter=". ">
+          <names variable="editor translator" delimiter=". ">
+            <label form="verb" text-case="capitalize-first" suffix=" "/>
+            <name and="text" delimiter=", "/>
+          </names>
+          <names variable="director" delimiter=". ">
+            <label form="verb" text-case="capitalize-first" suffix=" "/>
+            <name and="text" delimiter=", "/>
+          </names>
+        </group>
+      </if>
+    </choose>
+  </macro>
+  <macro name="container-contributors">
+    <choose>
+      <if type="chapter paper-conference" match="any">
+        <group prefix=", " delimiter=", ">
+          <names variable="container-author" delimiter=", ">
+            <label form="verb" suffix=" "/>
+            <name and="text" delimiter=", "/>
+          </names>
+          <names variable="editor translator" delimiter=", ">
+            <label form="verb" suffix=" "/>
+            <name and="text" delimiter=", "/>
+          </names>
+        </group>
+      </if>
+    </choose>
+  </macro>
+  <macro name="editor">
+    <names variable="editor">
+      <name name-as-sort-order="first" and="text" sort-separator=", " delimiter=", " delimiter-precedes-last="always"/>
+      <label form="short" prefix=", "/>
+    </names>
+  </macro>
+  <macro name="translator">
+    <names variable="translator">
+      <name name-as-sort-order="first" and="text" sort-separator=", " delimiter=", " delimiter-precedes-last="always"/>
+      <label form="short" prefix=", "/>
+    </names>
+  </macro>
+  <macro name="recipient">
+    <choose>
+      <if type="personal_communication">
+        <choose>
+          <if variable="genre">
+            <text variable="genre" text-case="capitalize-first"/>
+          </if>
+          <else>
+            <text term="letter" text-case="capitalize-first"/>
+          </else>
+        </choose>
+      </if>
+    </choose>
+    <names variable="recipient" delimiter=", ">
+      <label form="verb" prefix=" " text-case="lowercase" suffix=" "/>
+      <name and="text" delimiter=", "/>
+    </names>
+  </macro>
+  <macro name="substitute-title">
+    <choose>
+      <if type="article-magazine article-newspaper review review-book" match="any">
+        <text macro="container-title"/>
+      </if>
+    </choose>
+  </macro>
+  <macro name="contributors">
+    <group delimiter=". ">
+      <names variable="author">
+        <name and="text" name-as-sort-order="first" sort-separator=", " delimiter=", " delimiter-precedes-last="always"/>
+        <label form="short" prefix=", "/>
+        <substitute>
+          <names variable="editor"/>
+          <names variable="translator"/>
+          <names variable="director"/>
+          <text macro="substitute-title"/>
+          <text macro="title"/>
+        </substitute>
+      </names>
+      <text macro="recipient"/>
+    </group>
+  </macro>
+  <macro name="contributors-short">
+    <names variable="author">
+      <name form="short" and="text" delimiter=", " initialize-with=". "/>
+      <substitute>
+        <names variable="editor"/>
+        <names variable="translator"/>
+        <names variable="director"/>
+        <text macro="substitute-title"/>
+        <text macro="title"/>
+      </substitute>
+    </names>
+  </macro>
+  <macro name="interviewer">
+    <names variable="interviewer" delimiter=", ">
+      <label form="verb" prefix=" " text-case="capitalize-first" suffix=" "/>
+      <name and="text" delimiter=", "/>
+    </names>
+  </macro>
+  <macro name="archive">
+    <group delimiter=". ">
+      <text variable="archive_location" text-case="capitalize-first"/>
+      <text variable="archive"/>
+      <text variable="archive-place"/>
+    </group>
+  </macro>
+  <macro name="access">
+    <group delimiter=". ">
+      <choose>
+        <if type="graphic report" match="any">
+          <text macro="archive"/>
+        </if>
+        <else-if type="article-journal bill book chapter legal_case legislation motion_picture paper-conference" match="none">
+          <text macro="archive"/>
+        </else-if>
+      </choose>
+      <choose>
+        <if type="webpage post-weblog" match="any">
+          <date variable="issued" form="text"/>
+        </if>
+      </choose>
+      <choose>
+        <if variable="issued" match="none">
+          <group delimiter=" ">
+            <text term="accessed" text-case="capitalize-first"/>
+            <date variable="accessed" form="text"/>
+          </group>
+        </if>
+      </choose>
+      <choose>
+        <if type="legal_case" match="none">
+          <choose>
+            <if variable="DOI">
+              <text variable="DOI" prefix="https://doi.org/"/>
+            </if>
+            <else>
+              <text variable="URL"/>
+            </else>
+          </choose>
+        </if>
+      </choose>
+    </group>
+  </macro>
+  <macro name="title">
+    <choose>
+      <if variable="title" match="none">
+        <choose>
+          <if type="personal_communication" match="none">
+            <text variable="genre" text-case="capitalize-first"/>
+          </if>
+        </choose>
+      </if>
+      <else-if type="bill book graphic legislation motion_picture song" match="any">
+        <text variable="title" text-case="title" font-style="italic"/>
+        <group prefix=" (" suffix=")" delimiter=" ">
+          <text term="version"/>
+          <text variable="version"/>
+        </group>
+      </else-if>
+      <else-if variable="reviewed-author">
+        <choose>
+          <if variable="reviewed-title">
+            <group delimiter=". ">
+              <text variable="title" text-case="title" quotes="true"/>
+              <group delimiter=", ">
+                <text variable="reviewed-title" text-case="title" font-style="italic" prefix="Review of "/>
+                <names variable="reviewed-author">
+                  <label form="verb-short" text-case="lowercase" suffix=" "/>
+                  <name and="text" delimiter=", "/>
+                </names>
+              </group>
+            </group>
+          </if>
+          <else>
+            <group delimiter=", ">
+              <text variable="title" text-case="title" font-style="italic" prefix="Review of "/>
+              <names variable="reviewed-author">
+                <label form="verb-short" text-case="lowercase" suffix=" "/>
+                <name and="text" delimiter=", "/>
+              </names>
+            </group>
+          </else>
+        </choose>
+      </else-if>
+      <else-if type="legal_case interview patent" match="any">
+        <text variable="title"/>
+      </else-if>
+      <else>
+        <text variable="title" text-case="title" quotes="true"/>
+      </else>
+    </choose>
+  </macro>
+  <macro name="edition">
+    <choose>
+      <if type="bill book graphic legal_case legislation motion_picture report song" match="any">
+        <choose>
+          <if is-numeric="edition">
+            <group delimiter=" " prefix=". ">
+              <number variable="edition" form="ordinal"/>
+              <text term="edition" form="short" strip-periods="true"/>
+            </group>
+          </if>
+          <else>
+            <text variable="edition" text-case="capitalize-first" prefix=". "/>
+          </else>
+        </choose>
+      </if>
+      <else-if type="chapter paper-conference" match="any">
+        <choose>
+          <if is-numeric="edition">
+            <group delimiter=" " prefix=", ">
+              <number variable="edition" form="ordinal"/>
+              <text term="edition" form="short"/>
+            </group>
+          </if>
+          <else>
+            <text variable="edition" prefix=", "/>
+          </else>
+        </choose>
+      </else-if>
+    </choose>
+  </macro>
+  <macro name="locators">
+    <choose>
+      <if type="article-journal">
+        <choose>
+          <if variable="volume">
+            <text variable="volume" prefix=" "/>
+            <group prefix=" (" suffix=")">
+              <choose>
+                <if variable="issue">
+                  <text variable="issue"/>
+                </if>
+                <else>
+                  <date variable="issued">
+                    <date-part name="month"/>
+                  </date>
+                </else>
+              </choose>
+            </group>
+          </if>
+          <else-if variable="issue">
+            <group delimiter=" " prefix=", ">
+              <text term="issue" form="short"/>
+              <text variable="issue"/>
+              <date variable="issued" prefix="(" suffix=")">
+                <date-part name="month"/>
+              </date>
+            </group>
+          </else-if>
+          <else>
+            <date variable="issued" prefix=", ">
+              <date-part name="month"/>
+            </date>
+          </else>
+        </choose>
+      </if>
+      <else-if type="legal_case">
+        <text variable="volume" prefix=", "/>
+        <text variable="container-title" prefix=" "/>
+        <text variable="page" prefix=" "/>
+      </else-if>
+      <else-if type="bill book graphic legal_case legislation motion_picture report song" match="any">
+        <group prefix=". " delimiter=". ">
+          <group>
+            <text term="volume" form="short" text-case="capitalize-first" suffix=" "/>
+            <number variable="volume" form="numeric"/>
+          </group>
+          <group>
+            <number variable="number-of-volumes" form="numeric"/>
+            <text term="volume" form="short" prefix=" " plural="true"/>
+          </group>
+        </group>
+      </else-if>
+      <else-if type="chapter paper-conference" match="any">
+        <choose>
+          <if variable="page" match="none">
+            <group prefix=". ">
+              <text term="volume" form="short" text-case="capitalize-first" suffix=" "/>
+              <number variable="volume" form="numeric"/>
+            </group>
+          </if>
+        </choose>
+      </else-if>
+    </choose>
+  </macro>
+  <macro name="locators-chapter">
+    <choose>
+      <if type="chapter paper-conference" match="any">
+        <choose>
+          <if variable="page">
+            <group prefix=", ">
+              <text variable="volume" suffix=":"/>
+              <text variable="page"/>
+            </group>
+          </if>
+        </choose>
+      </if>
+    </choose>
+  </macro>
+  <macro name="locators-article">
+    <choose>
+      <if type="article-newspaper">
+        <group prefix=", " delimiter=", ">
+          <group delimiter=" ">
+            <text variable="edition"/>
+            <text term="edition"/>
+          </group>
+          <group>
+            <text term="section" form="short" suffix=" "/>
+            <text variable="section"/>
+          </group>
+        </group>
+      </if>
+      <else-if type="article-journal">
+        <choose>
+          <if variable="volume issue" match="any">
+            <text variable="page" prefix=":"/>
+          </if>
+          <else>
+            <text variable="page" prefix=", "/>
+          </else>
+        </choose>
+      </else-if>
+    </choose>
+  </macro>
+  <macro name="point-locators">
+    <choose>
+      <if variable="locator">
+        <choose>
+          <if locator="page" match="none">
+            <choose>
+              <if type="bill book graphic legal_case legislation motion_picture report song" match="any">
+                <choose>
+                  <if variable="volume">
+                    <group>
+                      <text term="volume" form="short" suffix=" "/>
+                      <number variable="volume" form="numeric"/>
+                      <label variable="locator" form="short" prefix=", " suffix=" "/>
+                    </group>
+                  </if>
+                  <else>
+                    <label variable="locator" form="short" suffix=" "/>
+                  </else>
+                </choose>
+              </if>
+              <else>
+                <label variable="locator" form="short" suffix=" "/>
+              </else>
+            </choose>
+          </if>
+          <else-if type="bill book graphic legal_case legislation motion_picture report song" match="any">
+            <number variable="volume" form="numeric" suffix=":"/>
+          </else-if>
+        </choose>
+        <text variable="locator"/>
+      </if>
+    </choose>
+  </macro>
+  <macro name="container-prefix">
+    <text term="in" text-case="capitalize-first"/>
+  </macro>
+  <macro name="container-title">
+    <choose>
+      <if type="chapter paper-conference" match="any">
+        <text macro="container-prefix" suffix=" "/>
+      </if>
+    </choose>
+    <choose>
+      <if type="webpage">
+        <text variable="container-title" text-case="title"/>
+      </if>
+      <else-if type="legal_case" match="none">
+	<group delimiter=" ">
+        <text variable="container-title" text-case="title" font-style="italic"/>
+	<choose>
+	  <if type="post-weblog">
+	    <text value="(blog)"/>
+	  </if>
+	</choose>
+	  </group>
+      </else-if>
+    </choose>
+  </macro>
+  <macro name="publisher">
+    <group delimiter=": ">
+      <text variable="publisher-place"/>
+      <text variable="publisher"/>
+    </group>
+  </macro>
+  <macro name="date">
+    <choose>
+      <if variable="issued">
+        <group delimiter=" ">
+          <date variable="original-date" form="text" date-parts="year" prefix="(" suffix=")"/>
+          <date variable="issued">
+            <date-part name="year"/>
+          </date>
+        </group>
+      </if>
+      <else-if variable="status">
+        <text variable="status" text-case="capitalize-first"/>
+      </else-if>
+      <else>
+        <text term="no date" form="short"/>
+      </else>
+    </choose>
+  </macro>
+  <macro name="date-in-text">
+    <choose>
+      <if variable="issued">
+        <group delimiter=" ">
+          <date variable="original-date" form="text" date-parts="year" prefix="[" suffix="]"/>
+          <date variable="issued">
+            <date-part name="year"/>
+          </date>
+        </group>
+      </if>
+      <else-if variable="status">
+        <text variable="status"/>
+      </else-if>
+      <else>
+        <text term="no date" form="short"/>
+      </else>
+    </choose>
+  </macro>
+  <macro name="day-month">
+    <date variable="issued">
+      <date-part name="month"/>
+      <date-part name="day" prefix=" "/>
+    </date>
+  </macro>
+  <macro name="collection-title">
+    <choose>
+      <if match="none" type="article-journal">
+        <choose>
+          <if match="none" is-numeric="collection-number">
+            <group delimiter=", ">
+              <text variable="collection-title" text-case="title"/>
+              <text variable="collection-number"/>
+            </group>
+          </if>
+          <else>
+            <group delimiter=" ">
+              <text variable="collection-title" text-case="title"/>
+              <text variable="collection-number"/>
+            </group>
+          </else>
+        </choose>
+      </if>
+    </choose>
+  </macro>
+  <macro name="collection-title-journal">
+    <choose>
+      <if type="article-journal">
+        <group delimiter=" ">
+          <text variable="collection-title"/>
+          <text variable="collection-number"/>
+        </group>
+      </if>
+    </choose>
+  </macro>
+  <macro name="event">
+    <group>
+      <text term="presented at" suffix=" "/>
+      <text variable="event"/>
+    </group>
+  </macro>
+  <macro name="description">
+    <choose>
+      <if type="interview">
+        <group delimiter=". ">
+          <text macro="interviewer"/>
+          <text variable="medium" text-case="capitalize-first"/>
+        </group>
+      </if>
+      <else-if type="patent">
+        <group delimiter=" " prefix=". ">
+          <text variable="authority"/>
+          <text variable="number"/>
+        </group>
+      </else-if>
+      <else>
+        <text variable="medium" text-case="capitalize-first" prefix=". "/>
+      </else>
+    </choose>
+    <choose>
+      <if variable="title" match="none"/>
+      <else-if type="thesis personal_communication speech" match="any"/>
+      <else>
+        <group delimiter=" " prefix=". ">
+          <text variable="genre" text-case="capitalize-first"/>
+          <choose>
+            <if type="report">
+              <text variable="number"/>
+            </if>
+          </choose>
+        </group>
+      </else>
+    </choose>
+  </macro>
+  <macro name="issue">
+    <choose>
+      <if type="legal_case">
+        <text variable="authority" prefix=". "/>
+      </if>
+      <else-if type="speech">
+        <group prefix=". " delimiter=", ">
+          <group delimiter=" ">
+            <text variable="genre" text-case="capitalize-first"/>
+            <text macro="event"/>
+          </group>
+          <text variable="event-place"/>
+          <text macro="day-month"/>
+        </group>
+      </else-if>
+      <else-if type="article-newspaper article-magazine personal_communication" match="any">
+        <date variable="issued" form="text" prefix=", "/>
+      </else-if>
+      <else-if type="patent">
+        <group delimiter=", " prefix=", ">
+          <group delimiter=" ">
+            <!--Needs Localization-->
+            <text value="filed"/>
+            <date variable="submitted" form="text"/>
+          </group>
+          <group delimiter=" ">
+            <choose>
+              <if variable="issued submitted" match="all">
+                <text term="and"/>
+              </if>
+            </choose>
+            <!--Needs Localization-->
+            <text value="issued"/>
+            <date variable="issued" form="text"/>
+          </group>
+        </group>
+      </else-if>
+      <else>
+        <group prefix=". " delimiter=", ">
+          <choose>
+            <if type="thesis">
+              <text variable="genre" text-case="capitalize-first"/>
+            </if>
+          </choose>
+          <text macro="publisher"/>
+        </group>
+      </else>
+    </choose>
+  </macro>
+  <citation et-al-min="4" et-al-use-first="1" disambiguate-add-year-suffix="true" disambiguate-add-names="true" disambiguate-add-givenname="true" givenname-disambiguation-rule="primary-name" collapse="year">
+    <layout prefix="(" suffix=")" delimiter="; ">
+      <group delimiter=", ">
+        <choose>
+          <if variable="issued accessed" match="any">
+            <group delimiter=" ">
+              <text macro="contributors-short"/>
+              <text macro="date-in-text"/>
+            </group>
+          </if>
+          <!---comma before forthcoming and n.d.-->
+          <else>
+            <group delimiter=", ">
+              <text macro="contributors-short"/>
+              <text macro="date-in-text"/>
+            </group>
+          </else>
+        </choose>
+        <text macro="point-locators"/>
+      </group>
+    </layout>
+  </citation>
+  <bibliography hanging-indent="true" et-al-min="11" et-al-use-first="7" subsequent-author-substitute="&#8212;&#8212;&#8212;" entry-spacing="0">
+    <sort>
+      <key macro="contributors"/>
+      <key variable="issued"/>
+      <key variable="title"/>
+    </sort>
+    <layout suffix=".">
+      <group delimiter=". ">
+        <text macro="contributors"/>
+        <text macro="date"/>
+        <text macro="title"/>
+      </group>
+      <text macro="description"/>
+      <text macro="secondary-contributors" prefix=". "/>
+      <text macro="container-title" prefix=". "/>
+      <text macro="container-contributors"/>
+      <text macro="edition"/>
+      <text macro="locators-chapter"/>
+      <text macro="collection-title-journal" prefix=", " suffix=", "/>
+      <text macro="locators"/>
+      <text macro="collection-title" prefix=". "/>
+      <text macro="issue"/>
+      <text macro="locators-article"/>
+      <text macro="access" prefix=". "/>
+    </layout>
+  </bibliography>
+</style>

etc/csl/locales-en-US.xml

@@ -0,0 +1,348 @@
+<?xml version="1.0" encoding="utf-8"?>
+<locale xmlns="http://purl.org/net/xbiblio/csl" version="1.0" xml:lang="en-US">
+  <info>
+    <rights license="http://creativecommons.org/licenses/by-sa/3.0/">This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 License</rights>
+    <updated>2015-10-10T23:31:02+00:00</updated>
+  </info>
+  <style-options punctuation-in-quote="true"/>
+  <date form="text">
+    <date-part name="month" suffix=" "/>
+    <date-part name="day" suffix=", "/>
+    <date-part name="year"/>
+  </date>
+  <date form="numeric">
+    <date-part name="month" form="numeric-leading-zeros" suffix="/"/>
+    <date-part name="day" form="numeric-leading-zeros" suffix="/"/>
+    <date-part name="year"/>
+  </date>
+  <terms>
+    <term name="accessed">accessed</term>
+    <term name="and">and</term>
+    <term name="and others">and others</term>
+    <term name="anonymous">anonymous</term>
+    <term name="anonymous" form="short">anon.</term>
+    <term name="at">at</term>
+    <term name="available at">available at</term>
+    <term name="by">by</term>
+    <term name="circa">circa</term>
+    <term name="circa" form="short">c.</term>
+    <term name="cited">cited</term>
+    <term name="edition">
+      <single>edition</single>
+      <multiple>editions</multiple>
+    </term>
+    <term name="edition" form="short">ed.</term>
+    <term name="et-al">et al.</term>
+    <term name="forthcoming">forthcoming</term>
+    <term name="from">from</term>
+    <term name="ibid">ibid.</term>
+    <term name="in">in</term>
+    <term name="in press">in press</term>
+    <term name="internet">internet</term>
+    <term name="interview">interview</term>
+    <term name="letter">letter</term>
+    <term name="no date">no date</term>
+    <term name="no date" form="short">n.d.</term>
+    <term name="online">online</term>
+    <term name="presented at">presented at the</term>
+    <term name="reference">
+      <single>reference</single>
+      <multiple>references</multiple>
+    </term>
+    <term name="reference" form="short">
+      <single>ref.</single>
+      <multiple>refs.</multiple>
+    </term>
+    <term name="retrieved">retrieved</term>
+    <term name="scale">scale</term>
+    <term name="version">version</term>
+
+    <!-- ANNO DOMINI; BEFORE CHRIST -->
+    <term name="ad">AD</term>
+    <term name="bc">BC</term>
+
+    <!-- PUNCTUATION -->
+    <term name="open-quote">“</term>
+    <term name="close-quote">”</term>
+    <term name="open-inner-quote">‘</term>
+    <term name="close-inner-quote">’</term>
+    <term name="page-range-delimiter">–</term>
+
+    <!-- ORDINALS -->
+    <term name="ordinal">th</term>
+    <term name="ordinal-01">st</term>
+    <term name="ordinal-02">nd</term>
+    <term name="ordinal-03">rd</term>
+    <term name="ordinal-11">th</term>
+    <term name="ordinal-12">th</term>
+    <term name="ordinal-13">th</term>
+
+    <!-- LONG ORDINALS -->
+    <term name="long-ordinal-01">first</term>
+    <term name="long-ordinal-02">second</term>
+    <term name="long-ordinal-03">third</term>
+    <term name="long-ordinal-04">fourth</term>
+    <term name="long-ordinal-05">fifth</term>
+    <term name="long-ordinal-06">sixth</term>
+    <term name="long-ordinal-07">seventh</term>
+    <term name="long-ordinal-08">eighth</term>
+    <term name="long-ordinal-09">ninth</term>
+    <term name="long-ordinal-10">tenth</term>
+
+    <!-- LONG LOCATOR FORMS -->
+    <term name="book">
+      <single>book</single>
+      <multiple>books</multiple>
+    </term>
+    <term name="chapter">
+      <single>chapter</single>
+      <multiple>chapters</multiple>
+    </term>
+    <term name="column">
+      <single>column</single>
+      <multiple>columns</multiple>
+    </term>
+    <term name="figure">
+      <single>figure</single>
+      <multiple>figures</multiple>
+    </term>
+    <term name="folio">
+      <single>folio</single>
+      <multiple>folios</multiple>
+    </term>
+    <term name="issue">
+      <single>number</single>
+      <multiple>numbers</multiple>
+    </term>
+    <term name="line">
+      <single>line</single>
+      <multiple>lines</multiple>
+    </term>
+    <term name="note">
+      <single>note</single>
+      <multiple>notes</multiple>
+    </term>
+    <term name="opus">
+      <single>opus</single>
+      <multiple>opera</multiple>
+    </term>
+    <term name="page">
+      <single>page</single>
+      <multiple>pages</multiple>
+    </term>
+    <term name="number-of-pages">
+      <single>page</single>
+      <multiple>pages</multiple>
+    </term>
+    <term name="paragraph">
+      <single>paragraph</single>
+      <multiple>paragraphs</multiple>
+    </term>
+    <term name="part">
+      <single>part</single>
+      <multiple>parts</multiple>
+    </term>
+    <term name="section">
+      <single>section</single>
+      <multiple>sections</multiple>
+    </term>
+    <term name="sub verbo">
+      <single>sub verbo</single>
+      <multiple>sub verbis</multiple>
+    </term>
+    <term name="verse">
+      <single>verse</single>
+      <multiple>verses</multiple>
+    </term>
+    <term name="volume">
+      <single>volume</single>
+      <multiple>volumes</multiple>
+    </term>
+
+    <!-- SHORT LOCATOR FORMS -->
+    <term name="book" form="short">
+      <single>bk.</single>
+      <multiple>bks.</multiple>
+    </term>
+    <term name="chapter" form="short">
+      <single>chap.</single>
+      <multiple>chaps.</multiple>
+    </term>
+    <term name="column" form="short">
+      <single>col.</single>
+      <multiple>cols.</multiple>
+    </term>
+    <term name="figure" form="short">
+      <single>fig.</single>
+      <multiple>figs.</multiple>
+    </term>
+    <term name="folio" form="short">
+      <single>fol.</single>
+      <multiple>fols.</multiple>
+    </term>
+    <term name="issue" form="short">
+      <single>no.</single>
+      <multiple>nos.</multiple>
+    </term>
+    <term name="line" form="short">
+      <single>l.</single>
+      <multiple>ll.</multiple>
+    </term>
+    <term name="note" form="short">
+      <single>n.</single>
+      <multiple>nn.</multiple>
+    </term>
+    <term name="opus" form="short">
+      <single>op.</single>
+      <multiple>opp.</multiple>
+    </term>
+    <term name="page" form="short">
+      <single>p.</single>
+      <multiple>pp.</multiple>
+    </term>
+    <term name="number-of-pages" form="short">
+      <single>p.</single>
+      <multiple>pp.</multiple>
+    </term>
+    <term name="paragraph" form="short">
+      <single>para.</single>
+      <multiple>paras.</multiple>
+    </term>
+    <term name="part" form="short">
+      <single>pt.</single>
+      <multiple>pts.</multiple>
+    </term>
+    <term name="section" form="short">
+      <single>sec.</single>
+      <multiple>secs.</multiple>
+    </term>
+    <term name="sub verbo" form="short">
+      <single>s.v.</single>
+      <multiple>s.vv.</multiple>
+    </term>
+    <term name="verse" form="short">
+      <single>v.</single>
+      <multiple>vv.</multiple>
+    </term>
+    <term name="volume" form="short">
+      <single>vol.</single>
+      <multiple>vols.</multiple>
+    </term>
+
+    <!-- SYMBOL LOCATOR FORMS -->
+    <term name="paragraph" form="symbol">
+      <single>¶</single>
+      <multiple>¶¶</multiple>
+    </term>
+    <term name="section" form="symbol">
+      <single>§</single>
+      <multiple>§§</multiple>
+    </term>
+
+    <!-- LONG ROLE FORMS -->
+    <term name="director">
+      <single>director</single>
+      <multiple>directors</multiple>
+    </term>
+    <term name="editor">
+      <single>editor</single>
+      <multiple>editors</multiple>
+    </term>
+    <term name="editorial-director">
+      <single>editor</single>
+      <multiple>editors</multiple>
+    </term>
+    <term name="illustrator">
+      <single>illustrator</single>
+      <multiple>illustrators</multiple>
+    </term>
+    <term name="translator">
+      <single>translator</single>
+      <multiple>translators</multiple>
+    </term>
+    <term name="editortranslator">
+      <single>editor &amp; translator</single>
+      <multiple>editors &amp; translators</multiple>
+    </term>
+
+    <!-- SHORT ROLE FORMS -->
+    <term name="director" form="short">
+      <single>dir.</single>
+      <multiple>dirs.</multiple>
+    </term>
+    <term name="editor" form="short">
+      <single>ed.</single>
+      <multiple>eds.</multiple>
+    </term>
+    <term name="editorial-director" form="short">
+      <single>ed.</single>
+      <multiple>eds.</multiple>
+    </term>
+    <term name="illustrator" form="short">
+      <single>ill.</single>
+      <multiple>ills.</multiple>
+    </term>
+    <term name="translator" form="short">
+      <single>tran.</single>
+      <multiple>trans.</multiple>
+    </term>
+    <term name="editortranslator" form="short">
+      <single>ed. &amp; tran.</single>
+      <multiple>eds. &amp; trans.</multiple>
+    </term>
+
+    <!-- VERB ROLE FORMS -->
+    <term name="container-author" form="verb">by</term>
+    <term name="director" form="verb">directed by</term>
+    <term name="editor" form="verb">edited by</term>
+    <term name="editorial-director" form="verb">edited by</term>
+    <term name="illustrator" form="verb">illustrated by</term>
+    <term name="interviewer" form="verb">interview by</term>
+    <term name="recipient" form="verb">to</term>
+    <term name="reviewed-author" form="verb">by</term>
+    <term name="translator" form="verb">translated by</term>
+    <term name="editortranslator" form="verb">edited &amp; translated by</term>
+
+    <!-- SHORT VERB ROLE FORMS -->
+    <term name="director" form="verb-short">dir. by</term>
+    <term name="editor" form="verb-short">ed. by</term>
+    <term name="editorial-director" form="verb-short">ed. by</term>
+    <term name="illustrator" form="verb-short">illus. by</term>
+    <term name="translator" form="verb-short">trans. by</term>
+    <term name="editortranslator" form="verb-short">ed. &amp; trans. by</term>
+
+    <!-- LONG MONTH FORMS -->
+    <term name="month-01">January</term>
+    <term name="month-02">February</term>
+    <term name="month-03">March</term>
+    <term name="month-04">April</term>
+    <term name="month-05">May</term>
+    <term name="month-06">June</term>
+    <term name="month-07">July</term>
+    <term name="month-08">August</term>
+    <term name="month-09">September</term>
+    <term name="month-10">October</term>
+    <term name="month-11">November</term>
+    <term name="month-12">December</term>
+
+    <!-- SHORT MONTH FORMS -->
+    <term name="month-01" form="short">Jan.</term>
+    <term name="month-02" form="short">Feb.</term>
+    <term name="month-03" form="short">Mar.</term>
+    <term name="month-04" form="short">Apr.</term>
+    <term name="month-05" form="short">May</term>
+    <term name="month-06" form="short">Jun.</term>
+    <term name="month-07" form="short">Jul.</term>
+    <term name="month-08" form="short">Aug.</term>
+    <term name="month-09" form="short">Sep.</term>
+    <term name="month-10" form="short">Oct.</term>
+    <term name="month-11" form="short">Nov.</term>
+    <term name="month-12" form="short">Dec.</term>
+
+    <!-- SEASONS -->
+    <term name="season-01">Spring</term>
+    <term name="season-02">Summer</term>
+    <term name="season-03">Autumn</term>
+    <term name="season-04">Winter</term>
+  </terms>
+</locale>

lisp/oc-csl.el

@@ -0,0 +1,603 @@
+;;; oc-csl.el --- csl citation processor for Org -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2021 Free Software Foundation, Inc.
+
+;; Author: Nicolas Goaziou <mail@nicolasgoaziou.fr>
+
+;; This program is free software; you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; This program is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; This library registers the `csl' citation processor, which provides
+;; the "export" capability for citations.
+
+;; The processor relies on the external Citeproc Emacs library, which must be
+;; available prior to loading this library.
+
+;; By default, citations are rendered in Chicago author-date CSL style.  You can
+;; use another style file by specifying it in `org-cite-export-processors' or
+;; from within the document by adding the file name to "cite_export" keyword
+;;
+;;    #+cite_export: csl /path/to/style-file.csl
+;;    #+cite_export: csl "/path/to/style-file.csl"
+;;
+;; With the variable `org-cite-csl-styles-dir' set appropriately, the
+;; above can even be shortened to
+;;
+;;     #+cite_export: csl style-file.csl
+;;
+;; Styles can be downloaded, for instance, from the Zotero Style Repository
+;; (<https://www.zotero.org/styles>).  Dependent styles (which are not "unique"
+;; in the Zotero Style Repository terminology) are not supported.
+
+;; The processor uses the "en-US" CSL locale file shipped with Org for rendering
+;; localized dates and terms in the references, independently of the language
+;; settings of the Org document.  Additional CSL locales can be made available
+;; by setting `org-cite-csl-locales-dir' to a directory containing the locale
+;; files in question (see <https://github.com/citation-style-language/locales>
+;; for such files).
+
+;; Bibliography is defined with the "bibliography" keyword.  It supports files
+;; with ".bib", ".bibtex", and ".json" extensions.  References are exported using
+;; the "print_bibliography" keyword.
+
+;; The library supports the following citation styles:
+;;
+;; - noauthor (na), including bare (b), caps (c) and bare-caps (bc) variants,
+;; - default style, including bare (b), caps (c) and bare-caps (bc) variants.
+
+;; CSL styles recognize "locator" in citation references' suffix.  For example,
+;; in the citation
+;;
+;;     [cite:see @Tarski-1965 chapter 1, for an example]
+;;
+;; "chapter 1" is the locator.  The whole citation is rendered as
+;;
+;;     (see Tarski 1965, chap. 1 for an example)
+;;
+;; in the default CSL style.
+;;
+;; The locator starts with a locator term, among "bk.", "bks.", "book", "chap.",
+;; "chaps.", "chapter", "col.", "cols.", "column", "figure", "fig.", "figs.",
+;; "folio", "fol.", "fols.", "number", "no.", "nos.", "line", "l.", "ll.",
+;; "note", "n.", "nn.", "opus", "op.", "opp.", "page", "p.", "pp.", "paragraph",
+;; "para.", "paras.", "¶", "¶¶", "§", "§§", "part", "pt.", "pts.", "section",
+;; "sec.", "secs.", "sub verbo", "s.v.", "s.vv.", "verse", "v.", "vv.",
+;; "volume", "vol.", and "vols.".  It ends with the last comma or digit in the
+;; suffix, whichever comes last, or runs till the end of the suffix.
+;;
+;; The part of the suffix before the locator is appended to reference's prefix.
+;; If no locator term is used, but a number is present, then "page" is assumed.
+
+;; This library was heavily inspired by and borrows from András Simonyi's
+;; Citeproc Org (<https://github.com/andras-simonyi/citeproc-org>) library.
+;; Many thanks to him!
+
+;;; Code:
+(require 'bibtex)
+(require 'json)
+(require 'org-cite)
+
+(require 'citeproc nil t)
+(declare-function citeproc-style-cite-note "ext:citeproc")
+(declare-function citeproc-proc-style "ext:citeproc")
+(declare-function citeproc-bt-entry-to-csl "ext:citeproc")
+(declare-function citeproc-locale-getter-from-dir "ext:citeproc")
+(declare-function citeproc-create "ext:citeproc")
+(declare-function citeproc-citation-create "ext:citeproc")
+(declare-function citeproc-append-citations "ext:citeproc")
+(declare-function citeproc-render-citations "ext:citeproc")
+(declare-function citeproc-render-bib "ext:citeproc")
+
+(declare-function org-element-interpret-data "org-element" (data))
+(declare-function org-element-map "org-element" (data types fun &optional info first-match no-recursion with-affiliated))
+(declare-function org-element-property "org-element" (property element))
+(declare-function org-element-put-property "org-element" (element property value))
+
+(declare-function org-export-data "org-export" (data info))
+(declare-function org-export-derived-backend-p "org-export" (backend &rest backends))
+(declare-function org-export-get-footnote-number "org-export" (footnote info &optional data body-first))
+
+
+;;; Customization
+
+;;;; Location of CSL directories
+(defcustom org-cite-csl-locales-dir nil
+  "Directory of CSL locale files.
+If nil then only the fallback en-US locale will be available."
+  :group 'org-cite
+  :package-version '(Org . "9.5")
+  :type '(choice
+          (dir :tag "Locales directory")
+          (const :tag "Use en-US locale only" nil))
+  :safe t)
+
+(defcustom org-cite-csl-styles-dir nil
+  "Directory of CSL style files.
+When non-nil, relative style file names are expanded relatively to this
+directory.  This variable is ignored when style file is absolute."
+  :group 'org-cite
+  :package-version '(Org . "9.5")
+  :type '(choice
+          (dir :tag "Styles directory")
+          (const :tag "Use absolute file names" nil))
+  :safe t)
+
+;;;; Citelinks
+(defcustom org-cite-csl-link-cites t
+  "When non-nil, link cites to references."
+  :group 'org-cite
+  :package-version '(Org . "9.5")
+  :type 'boolean
+  :safe t)
+
+(defcustom org-cite-csl-no-citelinks-backends '(ascii)
+  "List of export back-ends for which cite linking is disabled.
+Cite linking for export back-ends derived from any of the back-ends listed here,
+is also disabled."
+  :group 'org-cite
+  :package-version '(Org . "9.5")
+  :type '(repeat symbol)
+  :safe t)
+
+;;;; Output-specific variables
+(defcustom org-cite-csl-html-hanging-indent "1.5em"
+  "Size of hanging-indent for HTML output in valid CSS units."
+  :group 'org-cite
+  :package-version '(Org . "9.5")
+  :type 'string
+  :safe t)
+
+(defcustom org-cite-csl-html-label-width-per-char "0.6em"
+  "Character width in CSS units for calculating entry label widths.
+Used only when `second-field-align' is activated by the used CSL style."
+  :group 'org-cite
+  :package-version '(Org . "9.5")
+  :type 'string
+  :safe t)
+
+(defcustom org-cite-csl-latex-hanging-indent "1.5em"
+  "Size of hanging-indent for LaTeX output in valid LaTeX units."
+  :group 'org-cite
+  :package-version '(Org . "9.5")
+  :type 'string
+  :safe t)
+
+
+;;; Internal variables
+(defconst org-cite-csl--etc-dir
+  (expand-file-name
+   (concat (file-name-directory (locate-library "oc"))
+           "../etc/csl/"))
+  "Directory \"etc/\" from repository.")
+
+(defconst org-cite-csl--fallback-locales-dir org-cite-csl--etc-dir
+  "Fallback CSL locale files directory.")
+
+(defconst org-cite-csl--fallback-style-file
+  (expand-file-name "chicago-author-date.csl"
+                    org-cite-csl--etc-dir)
+  "Default CSL style file, or nil.
+If nil then the Chicago author-date style is used as a fallback.")
+
+(defconst org-cite-csl--label-alist
+  '(("bk."       . "book")
+    ("bks."      . "book")
+    ("book"      . "book")
+    ("chap."     . "chapter")
+    ("chaps."    . "chapter")
+    ("chapter"   . "chapter")
+    ("col."      . "column")
+    ("cols."     . "column")
+    ("column"    . "column")
+    ("figure"    . "figure")
+    ("fig."      . "figure")
+    ("figs."     . "figure")
+    ("folio"     . "folio")
+    ("fol."      . "folio")
+    ("fols."     . "folio")
+    ("number"    . "number")
+    ("no."       . "number")
+    ("nos."      . "number")
+    ("line"      . "line")
+    ("l."        . "line")
+    ("ll."       . "line")
+    ("note"      . "note")
+    ("n."        . "note")
+    ("nn."       . "note")
+    ("opus"      . "opus")
+    ("op."       . "opus")
+    ("opp."      . "opus")
+    ("page"      . "page")
+    ("p"         . "page")
+    ("p."        . "page")
+    ("pp."       . "page")
+    ("paragraph" . "paragraph")
+    ("para."     . "paragraph")
+    ("paras."    . "paragraph")
+    ("¶"         . "paragraph")
+    ("¶¶"        . "paragraph")
+    ("§"         . "paragraph")
+    ("§§"        . "paragraph")
+    ("part"      . "part")
+    ("pt."       . "part")
+    ("pts."      . "part")
+    ("section"   . "section")
+    ("sec."      . "section")
+    ("secs."     . "section")
+    ("sub verbo" . "sub verbo")
+    ("s.v."      . "sub verbo")
+    ("s.vv."     . "sub verbo")
+    ("verse"     . "verse")
+    ("v."        . "verse")
+    ("vv."       . "verse")
+    ("volume"    . "volume")
+    ("vol."      . "volume")
+    ("vols."     . "volume"))
+  "Alist mapping locator names to locators.")
+
+(defconst org-cite-csl--label-regexp
+  (rx word-start
+      (regexp (regexp-opt (mapcar #'car org-cite-csl--label-alist) t))
+      (0+ digit)
+      (or word-start line-end (any ?\s ?\t)))
+  "Regexp matching a label in a citation reference suffix.
+Label is in match group 1.")
+
+
+;;; Internal functions
+(defun org-cite-csl--barf-without-citeproc ()
+  "Raise an error if Citeproc library is not loaded."
+  (unless (featurep 'citeproc) "Citeproc library is not loaded"))
+
+(defun org-cite-csl--note-style-p (info)
+  "Non-nil when bibliography style implies wrapping citations in footnotes.
+INFO is the export state, as a property list."
+  (citeproc-style-cite-note
+   (citeproc-proc-style
+    (org-cite-csl--processor info))))
+
+(defun org-cite-csl--no-affixes-p (citation info)
+  "Non-nil when CITATION should be exported without affix.
+INFO is the export data, as a property list."
+  (pcase (org-cite-citation-style citation info)
+    (`(,(or "noauthor" "na" `nil) . ,(or "bare" "b" "bare-caps" "bc")) t)
+    (_ nil)))
+
+(defun org-cite-csl--capitalize-p (citation info)
+  "Non-nil when CITATION should be capitalized.
+INFO is the export-data, as a property list."
+  (pcase (org-cite-citation-style citation info)
+    (`(,(or "noauthor" "na" `nil) . ,(or "caps" "c" "bare-caps" "bc")) t)
+    (_ nil)))
+
+(defun org-cite-csl--no-author-p (reference info)
+  "Non-nil when citation REFERENCE should be exported without author.
+INFO is the export data, as a property list."
+  (pcase (org-cite-citation-style (org-element-property :parent reference) info)
+    (`(,(or "noauthor" "na") . ,_) t)
+    (_ nil)))
+
+(defun org-cite-csl--no-citelinks-p (info)
+  "Non-nil when export BACKEND should not create cite-reference links."
+  (or (not org-cite-csl-link-cites)
+      (and org-cite-csl-no-citelinks-backends
+           (apply #'org-export-derived-backend-p
+                  (plist-get info :back-end)
+                  org-cite-csl-no-citelinks-backends))
+      ;; No references are being exported anyway.
+      (not (org-element-map (plist-get info :parse-tree) 'keyword
+             (lambda (k)
+               (equal "PRINT_BIBLIOGRAPHY" (org-element-property :key k)))
+             info t))))
+
+(defun org-cite-csl--output-format (info)
+  "Return expected Citeproc's output format.
+INFO is the export state, as a property list.  The return value is a symbol
+corresponding to one of the output formats supported by Citeproc: `html',
+`latex', or `org'."
+  (let ((backend (plist-get info :back-end)))
+    (cond
+     ((org-export-derived-backend-p backend 'html) 'html)
+     ((org-export-derived-backend-p backend 'latex) 'latex)
+     (t 'org))))
+
+(defun org-cite-csl--style-file (info)
+  "Return style file associated to current export process.
+
+INFO is the export state, as a property list.
+
+When file name is relative, expand it according to `org-cite-csl-styles-dir',
+or raise an error if the variable is unset."
+  (pcase (org-cite-bibliography-style info)
+    ('nil org-cite-csl--fallback-style-file)
+    ((and (pred file-name-absolute-p) file) file)
+    ((and (guard org-cite-csl-styles-dir) file)
+     (expand-file-name file org-cite-csl-styles-dir))
+    (other
+     (user-error "Cannot handle relative style file name" other))))
+
+(defun org-cite-csl--itemgetter (bibliography)
+  "Return Citeproc's \"itemgetter\" function for BIBLIOGRAPHY files.
+The function handles \".bib\", \".bibtex\" and \".json\" files."
+  (let ((cache (make-hash-table :test #'equal)))
+    (dolist (file bibliography)
+      (pcase (file-name-extension file)
+        ("json"
+         (let ((json-array-type 'list)
+               (json-key-type 'symbol))
+           (dolist (item (json-read-file file))
+             (puthash (cdr (assq 'id item)) item cache))))
+        ((and (or "bib" "bibtex") ext)
+         (with-temp-buffer
+	   (insert-file-contents file)
+	   (goto-char (point-min))
+	   (bibtex-set-dialect (if (string= ext "bib") 'biblatex 'BibTeX) t)
+	   (bibtex-map-entries
+	    (lambda (key &rest _)
+              (puthash key
+                       (citeproc-bt-entry-to-csl (bibtex-parse-entry))
+                       cache)))))
+        (ext
+         (user-error "Unknown bibliography extension: %S" ext))))
+    (lambda (itemids)
+      (mapcar (lambda (id)
+                (cons id (gethash id cache)))
+              itemids))))
+
+(defun org-cite-csl--locale-getter ()
+  "Return a locale getter.
+The getter looks for locales in `org-cite-csl-locales-dir' directory.  If it
+cannot find them, it retrieves the default \"en_US\" from
+`org-cite-csl--fallback-locales-dir'."
+  (lambda (loc)
+    (or (and org-cite-csl-locales-dir
+             (ignore-errors
+               (funcall (citeproc-locale-getter-from-dir org-cite-csl-locales-dir)
+                        loc)))
+        (funcall (citeproc-locale-getter-from-dir
+                  org-cite-csl--fallback-locales-dir)
+                 loc))))
+
+(defun org-cite-csl--processor (info)
+  "Return Citeproc processor reading items from current bibliography.
+
+INFO is the export state, as a property list.
+
+Newly created processor is stored as the value of the `:cite-citeproc-processor'
+property in INFO."
+  (or (plist-get info :cite-citeproc-processor)
+      (let* ((bibliography (plist-get info :bibliography))
+             (locale (or (plist-get info :language) "en_US"))
+             (processor
+              (citeproc-create
+               (org-cite-csl--style-file info)
+               (org-cite-csl--itemgetter bibliography)
+               (org-cite-csl--locale-getter)
+               locale)))
+        (plist-put info :cite-citeproc-processor processor)
+        processor)))
+
+(defun org-cite-csl--parse-reference (reference info)
+  "Return Citeproc's structure associated to citation REFERENCE.
+
+INFO is the export state, as a property list.
+
+The result is a association list.  Keys are: `id', `suppress-author', `prefix',
+`suffix', `location', `locator' and `label'."
+  (let (label location-start locator-start location locator prefix suffix)
+    ;; Parse suffix.  Insert it in a temporary buffer to find
+    ;; different parts: pre-label, label, locator, location (label +
+    ;; locator), and suffix.
+    (with-temp-buffer
+      (save-excursion
+        (insert (org-element-interpret-data
+                 (org-element-property :suffix reference))))
+      (cond
+       ((re-search-forward org-cite-csl--label-regexp nil t)
+        (setq location-start (match-beginning 0))
+        (setq label (cdr (assoc (match-string 1) org-cite-csl--label-alist)))
+        (setq locator-start (match-end 1)))
+       ((re-search-forward (rx digit) nil t)
+        (setq location-start (match-beginning 0))
+        (setq label "page")
+        (setq locator-start location-start))
+       (t
+        (setq suffix (org-element-property :suffix reference))))
+      ;; Find locator's end, and suffix, if any. To that effect, look
+      ;; for the last comma or digit after label, whichever comes
+      ;; last.
+      (unless suffix
+        (goto-char (point-max))
+        (let ((re (rx (or "," (group digit)))))
+          (when (re-search-backward re location-start t)
+            (goto-char (or (match-end 1) (match-beginning 0)))
+            (setq location (buffer-substring location-start (point)))
+            (setq locator (org-trim (buffer-substring locator-start (point))))
+            ;; Skip comma in suffix.
+            (setq suffix
+                  (org-cite-parse-objects
+                   (buffer-substring (match-end 0) (point-max))
+                   t)))))
+      (setq prefix
+            (org-cite-concat
+             (org-element-property :prefix reference)
+             (and location-start
+                  (org-cite-parse-objects
+                   (buffer-substring 1 location-start)
+                   t)))))
+    ;; Return value.
+    (let ((export
+           (lambda (data)
+             (org-string-nw-p
+              (org-trim
+               ;; When Citeproc exports to Org syntax, avoid mix and
+               ;; matching output formats by also generating Org
+               ;; syntax for prefix and suffix.
+               (if (eq 'org (org-cite-csl--output-format info))
+                   (org-element-interpret-data data)
+                 (org-export-data data info)))))))
+      `((id . ,(org-element-property :key reference))
+        (prefix . ,(funcall export prefix))
+        (suffix . ,(funcall export suffix))
+        (locator . ,locator)
+        (label . ,label)
+        (location . ,location)
+        (suppress-author . ,(org-cite-csl--no-author-p reference info))))))
+
+(defun org-cite-csl--create-structure (citation info)
+  "Create Citeproc structure for CITATION object.
+INFO is the export state, as a property list."
+  (let* ((cites (mapcar (lambda (r)
+                          (org-cite-csl--parse-reference r info))
+                        (org-cite-get-references citation)))
+         (footnote (org-cite-inside-footnote-p citation)))
+    ;; Global prefix is inserted in front of the prefix of the first
+    ;; reference.
+    (let ((global-prefix (org-element-property :prefix citation)))
+      (when global-prefix
+        (let* ((first (car cites))
+               (prefix (org-element-property :prefix first)))
+          (org-element-put-property
+           first :prefix (org-cite-concat global-prefix prefix)))))
+    ;; Global suffix is appended to the suffix of the last reference.
+    (let ((global-suffix (org-element-property :suffix citation)))
+      (when global-suffix
+        (let* ((last (org-last cites))
+               (suffix (org-element-property :suffix last)))
+          (org-element-put-property
+           last :suffix (org-cite-concat suffix global-suffix)))))
+    ;; Check if CITATION needs wrapping, i.e., it should be wrapped in
+    ;; a footnote, but isn't yet.
+    (when (and (not footnote) (org-cite-csl--note-style-p info))
+      (org-cite-adjust-note citation info)
+      (org-cite-wrap-citation citation info))
+    ;; Return structure.
+    (citeproc-citation-create
+     :note-index (and footnote (org-export-get-footnote-number footnote info))
+     :cites cites
+     :capitalize-first (or footnote (org-cite-csl--capitalize-p citation info))
+     :suppress-affixes (org-cite-csl--no-affixes-p citation info))))
+
+(defun org-cite-csl--rendered-citations (info)
+  "Return the rendered citations as an association list.
+
+INFO is the export state, as a property list.
+
+Return an alist (CITATION . OUTPUT) where CITATION object has been rendered as
+OUTPUT using Citeproc."
+  (or (plist-get info :cite-citeproc-rendered-citations)
+      (let* ((citations (org-cite-list-citations info))
+             (processor (org-cite-csl--processor info))
+             (structures
+              (mapcar (lambda (c) (org-cite-csl--create-structure c info))
+                      citations)))
+        (citeproc-append-citations structures processor)
+        (let* ((rendered
+                (citeproc-render-citations
+                 processor
+                 (org-cite-csl--output-format info)
+                 (org-cite-csl--no-citelinks-p info)))
+               (result (seq-mapn #'cons citations rendered)))
+          (plist-put info :cite-citeproc-rendered-citations result)
+          result))))
+
+
+;;; Export capability
+(defun org-cite-csl-render-citation (citation _style _backend info)
+  "Export CITATION object.
+INFO is the export state, as a property list."
+  (org-cite-csl--barf-without-citeproc)
+  (let ((output (cdr (assq citation (org-cite-csl--rendered-citations info)))))
+    (if (not (eq 'org (org-cite-csl--output-format info)))
+        output
+      ;; Parse Org output to re-export it during the regular export
+      ;; process.
+      (org-cite-parse-objects output))))
+
+(defun org-cite-csl-render-bibliography (_keys _files _style _props _backend info)
+  "Export bibliography.
+INFO is the export state, as a property list."
+  (org-cite-csl--barf-without-citeproc)
+  (pcase-let* ((format (org-cite-csl--output-format info))
+               (`(,output . ,parameters)
+                (citeproc-render-bib
+                 (org-cite-csl--processor info)
+                 format
+                 (org-cite-csl--no-citelinks-p info))))
+    (pcase format
+      ('html
+       (concat
+        (and (cdr (assq 'second-field-align parameters))
+             (let* ((max-offset (cdr (assq 'max-offset parameters)))
+                    (char-width
+                     (string-to-number org-cite-csl-html-label-width-per-char))
+                    (char-width-unit
+                     (progn
+                       (string-match (number-to-string char-width)
+                                     org-cite-csl-html-label-width-per-char)
+                       (substring org-cite-csl-html-label-width-per-char
+                                  (match-end 0)))))
+               (format
+                "<style>.csl-left-margin{float: left; padding-right: 0em;}
+ .csl-right-inline{margin: 0 0 0 %d%s;}</style>"
+                (* max-offset char-width)
+                char-width-unit)))
+        (and (cdr (assq 'hanging-indent parameters))
+             (format
+              "<style>.csl-entry{text-indent: -%s; margin-left: %s;}</style>"
+              org-cite-csl-html-hanging-indent
+              org-cite-csl-html-hanging-indent))
+        output))
+      ('latex
+       (if (cdr (assq 'hanging-indent parameters))
+           (format "\\begin{hangparas}{%s}{1}\n%s\n\\end{hangparas}"
+                   org-cite-csl-latex-hanging-indent
+                   output)
+         output))
+      (_
+       ;; Parse Org output to re-export it during the regular export
+       ;; process.
+       (org-cite-parse-elements output)))))
+
+(defun org-cite-csl-finalizer (output _keys _files _style _backend info)
+  "Add \"hanging\" package if missing from LaTeX output.
+OUTPUT is the export document, as a string.  INFO is the export state, as a
+property list."
+  (org-cite-csl--barf-without-citeproc)
+  (if (not (eq 'latex (org-cite-csl--output-format info)))
+      output
+    (with-temp-buffer
+      (save-excursion (insert output))
+      (when (search-forward "\\begin{document}" nil t)
+        ;; Ensure there is a \usepackage{hanging} somewhere or add one.
+        (goto-char (match-beginning 0))
+        (let ((re (rx "\\usepackage" (opt "[" (*? nonl) "]") "{hanging}")))
+          (unless (re-search-backward re nil t)
+            (insert "\\usepackage{hanging}\n"))))
+      (buffer-string))))
+
+
+;;; Register `csl' processor
+(org-cite-register-processor 'csl
+  :export-citation #'org-cite-csl-render-citation
+  :export-bibliography #'org-cite-csl-render-bibliography
+  :export-finalizer #'org-cite-csl-finalizer
+  :cite-styles
+  '((("noauthor" "na") ("bare" "b") ("bare-caps" "bc") ("caps" "c"))
+    (("nil") ("bare" "b") ("bare-caps" "bc") ("caps" "c"))))
+
+(provide 'org-cite-csl)
+(provide 'oc-csl)
+;;; oc-citeproc.el ends here