org-babel-tangle is collecting blocks by language->session

lisp/org-babel-tangle.el

@@ -38,18 +38,35 @@ language, and the cdr should be a list containing the extension
 and shebang(#!) line to use when writing out the language to
 file.")
 
-(defun org-bable-tangle ()
+(defun org-babel-tangle ()
   "Extract the bodies of all source code blocks form the current
 file into their own source-specific files."
   (interactive)
-  (let (by-lang)
+  (let (blocks)
+    ;; blocks will be two nested association lists, first grouped by
+    ;; language, then by session, the contents of the second a-list
+    ;; will be source-code blocks
     (org-babel-map-source-blocks (buffer-file-name)
-      (let ((link (progn (org-store-link nil) (pop org-stored-links)))
-            (source-name (intern (org-babel-get-src-block-name)))
-            (info (org-babel-get-src-block-info)))
-        ;; once collected these can be added to by-lang and then
-        ;; dropped out to buffers
-        ))))
+      (let* ((link (progn (org-store-link nil) (pop org-stored-links)))
+             (source-name (intern (org-babel-get-src-block-name)))
+             (info (org-babel-get-src-block-info))
+             (lang (first info))
+             (body (second info))
+             (params (third info))
+             (spec (list link source-name params body))
+             (session (cdr (assoc :session params)))
+             by-lang by-session)
+        ;; add the spec for this block to blocks under it's lang and session
+        (setq by-lang (org-babel-alist-pop lang blocks))
+        (setq by-session (org-babel-alist-pop session by-lang))
+        (setq blocks (cons ;; by-language
+                      (cons lang (cons ;; by-session
+                                  (cons session (cons spec by-session)) by-lang))
+                      blocks))))
+    ;; blocks should contain all source-blocks organized by language
+    ;; and session
+    (message "block = %S" blocks)
+    blocks))
 
 (provide 'org-babel-tangle)
 ;;; org-babel-tangle.el ends here

lisp/org-babel.el

@@ -404,6 +404,13 @@ non-nil."
         (dotimes (n size)
           (move-beginning-of-line 1) (insert ": ") (forward-line 1))))))
 
+(defun org-babel-alist-pop (key alist)
+  "Return the `assoc' of KEY in ALIST, and remove all elements of
+ALIST matching KEY with `assq-delete-all'."
+  (let ((results (assoc key alist)))
+    (setq alist (assq-delete-all key alist))
+    results))
+
 (defun org-babel-clean-text-properties (text)
   "Strip all properties from text return."
   (set-text-properties 0 (length text) nil text) text)