Merge pull request #228 from vermiculus/vermiculus/sort-answers

Customizable sorting; Fix #226. Generalization of #225.

4 files changed, 43 insertions, 17 deletions

diff --git a/sx-question-list.el b/sx-question-list.el
index 884f994..92b4c07 100644
--- a/sx-question-list.el
+++ b/sx-question-list.el
@@ -309,11 +309,10 @@ into consideration.
   ;; Add a setter to protect the value.
   :group 'sx-question-list)
 
-(defun sx-question-list--date-more-recent-p (x y)
-  "Non-nil if tabulated-entry X is newer than Y."
-  (sx--<
-   sx-question-list-date-sort-method
-   (car x) (car y) #'>))
+(sx--create-comparator sx-question-list--date-more-recent-p
+  "Non-nil if tabulated-entry A is newer than B."
+  #'> (lambda (x)
+        (cdr (assq sx-question-list-date-sort-method (car x)))))
 
 
 ;;; Keybinds
diff --git a/sx-question-print.el b/sx-question-print.el
index 9a51efb..a25ff52 100644
--- a/sx-question-print.el
+++ b/sx-question-print.el
@@ -153,6 +153,15 @@ replaced with the comment."
   :type 'boolean
   :group 'sx-question-mode)
 
+(defcustom sx-question-mode-answer-sort-function
+  #'sx-answer-higher-score-p
+  "Function used to sort answers in the question buffer."
+  :type '(choice
+          (const :tag "Higher-scoring first" sx-answer-higher-score-p)
+          (const :tag "Newer first"          sx-answer-newer-p)
+          (const :tag "More active first"    sx-answer-more-active-p))
+  :group 'sx-question-mode)
+
 
 ;;; Functions
 ;;;; Printing the general structure
@@ -167,11 +176,7 @@ QUESTION must be a data structure returned by `json-read'."
   (sx-question-mode--print-section question)
   (sx-assoc-let question
     (mapc #'sx-question-mode--print-section
-          (cl-sort .answers
-                   ;; Highest-voted first. @TODO: custom sorting
-                   (lambda (a b)
-                     (> (cdr (assoc 'score a))
-                        (cdr (assoc 'score b)))))))
+          (cl-sort .answers sx-question-list--sort-answer-function)))
   (insert "\n\n                       ")
   (insert-text-button "Write an Answer" :type 'sx-button-answer)
   ;; Go up
diff --git a/sx-question.el b/sx-question.el
index 1adbc24..1e3a02c 100644
--- a/sx-question.el
+++ b/sx-question.el
@@ -187,6 +187,21 @@ If no cache exists for it, initialize one with SITE."
   "Formats TAG for display."
   (concat "[" tag "]"))
 
+
+;;; Question Mode Answer-Sorting Functions
+
+(sx--create-comparator sx-answer-higher-score-p
+  "Return t if answer A has a higher score than answer B."
+  #'> (lambda (x) (cdr (assq 'score x))))
+
+(sx--create-comparator sx-answer-newer-p
+  "Return t if answer A was posted later than answer B."
+  #'> (lambda (x) (cdr (assq 'creation_date x))))
+
+(sx--create-comparator sx-answer-more-active-p
+  "Return t if answer A was updated after answer B."
+  #'> (lambda (x) (cdr (assq 'last_activity_date x))))
+
 (provide 'sx-question)
 ;;; sx-question.el ends here
 
diff --git a/sx.el b/sx.el
index 36ecfca..a385a84 100644
--- a/sx.el
+++ b/sx.el
@@ -259,6 +259,20 @@ whenever BODY evaluates to nil."
        :filter (lambda (&optional _)
                  (when (progn ,@body) ,def)))))
 
+(defmacro sx--create-comparator (name doc compare-func get-func)
+  "Define a new comparator called NAME with documentation DOC.
+COMPARE-FUNC is a function that takes the return value of
+GET-FUNC and performs the actual comparison."
+  (declare (indent 1) (doc-string 2))
+  `(progn
+     ;; In using `defalias', the macro supports both function
+     ;; symbols and lambda expressions.
+     (defun ,name (a b)
+       ,doc
+       (funcall ,compare-func
+                (funcall ,get-func a)
+                (funcall ,get-func b)))))
+
 
 ;;; Printing request data
 (defvar sx--overlays nil
@@ -354,13 +368,6 @@ Run after `sx-init--internal-hook'."
 This is used internally to set initial values for variables such
 as filters.")
 
-(defun sx--< (property x y &optional predicate)
-  "Non-nil if PROPERTY attribute of alist X is less than that of Y.
-With optional argument PREDICATE, use it instead of `<'."
-  (funcall (or predicate #'<)
-           (cdr (assoc property x))
-           (cdr (assoc property y))))
-
 (defmacro sx-init-variable (variable value &optional setter)
   "Set VARIABLE to VALUE using SETTER.
 SETTER should be a function of two arguments.  If SETTER is nil,