;; jao-maildir.el -- Utilities for reading maildirs -*- lexical-binding: t; -*-

;; Copyright (c) 2019, 2020 jao

;; Author: jao <mail@jao.io>
;; Start date: Sun Dec 01, 2019 15:48
;; Keywords: mail

;; This file 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, or (at your option)
;; any later version.

;; This file 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 GNU Emacs; see the file COPYING.  If not, write to
;; the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
;; Boston, MA 02111-1307, USA.

;;; Comentary:

;; Inspecting the contents of maildirs and reporting it.

;;; Code:

(require 'seq)
(require 'jao-minibuffer)

(defvar jao-maildirs nil)
(defvar jao-maildir-counts nil)
(defvar jao-maildir-debug-p nil)
(defvar jao-maildir-echo-p t)
(defvar jao-maildir-tracked-maildirs nil)

(defun jao-maildir--maildir-new (mbox) (expand-file-name "new" mbox))

(defun jao-maildir--maildir-new-count (mbox)
  (- (length (directory-files (jao-maildir--maildir-new mbox))) 2))

(defun jao-maildir--update-counts ()
  (dolist (mbox jao-maildirs)
    (puthash mbox (jao-maildir--maildir-new-count mbox) jao-maildir-counts)))

(defun jao-maildir--init-counts (maildirs)
  (setq jao-maildir-counts (make-hash-table :test 'equal))
  (setq jao-maildirs maildirs)
  (jao-maildir--update-counts)
  (jao-maildir--update-info-string t))

(defvar jao-maildir-tracked-maildirs)
(defvar jao-maildir-info-string "")

(defgroup jao-maildir-faces nil "Faces"
  :group 'faces)

(defface jao-maildir-emph '((t :inherit font-lock-keyword-face))
  "Face used to highlihgt non-boring tracked maildirs"
  :group 'jao-maildir-faces)

(defun jao-maildir--tracked-count (track)
  (let ((rx (car track)))
    (seq-reduce (lambda (c k)
                  (if (string-match-p rx k) (+ c (gethash k jao-maildir-counts 0)) c))
                (hash-table-keys jao-maildir-counts)
                0)))

(defvar jao-maildir--track-strings ())

(defun jao-maildir--update-track-string (mbox)
  (when-let ((track (seq-find (lambda (td)
                                (string-match-p (car td) mbox))
                              jao-maildir-tracked-maildirs)))
    (let* ((label (cadr track))
           (other (assoc-delete-all label jao-maildir--track-strings))
           (cnt (jao-maildir--tracked-count track)))
      (if (> cnt 0)
          (let* ((face (caddr track))
                 (am (format "%s%s" label cnt))
                 (face1 (if (eq t face) 'jao-maildir-emph face))
                 (str (cons label (if face (propertize am 'face face1) am))))
            (setq jao-maildir--track-strings
                  (if face (cons str other) (append other (list str)))))
        (setq jao-maildir--track-strings other)))))

(defun jao-maildir--update-info-string (&optional mbox)
  (cond ((eq mbox t) (seq-do 'jao-maildir--update-track-string jao-maildirs))
        ((stringp mbox) (jao-maildir--update-track-string mbox)))
  (let ((s (mapconcat 'identity (mapcar 'cdr jao-maildir--track-strings) " ")))
    (setq jao-maildir-info-string (if (string-blank-p s) "" (concat s " "))))
  (when jao-maildir-echo-p (jao-minibuffer-refresh)))

(defvar jao-maildir--watches nil)

(defun jao-maildir-cancel-watchers ()
  (dolist (w jao-maildir--watches) (file-notify-rm-watch w))
  (setq jao-maildir--watches nil))

(defun jao-maildir--log-watch (mbox e)
  (when jao-maildir-debug-p
    (message "[%s] watch: %s: %s" (current-time-string) mbox e)))

(defun jao-maildir--watcher (mbox cb)
  (lambda (e)
    (jao-maildir--log-watch e mbox)
    (when (memq (cadr e) '(created deleted))
      (puthash mbox (jao-maildir--maildir-new-count mbox) jao-maildir-counts)
      (jao-maildir--update-info-string mbox)
      (when cb (funcall cb mbox)))))

(defun jao-maildir--setup-watches (cb)
  (jao-maildir-cancel-watchers)
  (setq jao-maildir--watches
        (mapcar (lambda (mbox)
                  (file-notify-add-watch (jao-maildir--maildir-new mbox)
                                         '(change attribute-change)
                                         (jao-maildir--watcher mbox cb)))
                jao-maildirs)))

;;;###autoload
(defun jao-maildir-setup (maildirs mode-line &optional cb)
  (jao-maildir--init-counts maildirs)
  (cond ((eq 'mode-line mode-line)
         (add-to-list 'global-mode-string 'jao-maildir-info-string t))
        (mode-line
         (jao-minibuffer-add-variable 'jao-maildir-info-string)
         (jao-maildir--update-info-string)))
  (jao-maildir--setup-watches cb))


(provide 'jao-maildir)
;;; jao-maildir.el ends here