;;; mm-modeline.el --- Pluggable modeline components  -*- lexical-binding: t; -*-

(defmacro mm-modeline--define-component (name &rest forms)
  (declare (indent 1))
  `(progn
     (defface ,(intern (format "%s-face" name))
       '((t))
       ,(format "Face for the `%s' component." name))
     (defvar-local ,name '(:eval (or ,(macroexp-progn forms) "")))
     (put ',name 'risky-local-variable t)))


;;; Support Icons

(use-package all-the-icons
  :ensure t
  :init
  (defvar mm-all-the-icons-cookie
    (expand-file-name ".all-the-icons-installed-p" mm-cache-directory))
  (unless (file-exists-p mm-all-the-icons-cookie)
    (all-the-icons-install-fonts)
    (make-empty-file mm-all-the-icons-cookie :parents))
  (set-char-table-range char-width-table #xE907 2))


;;; Modeline Components

(mm-modeline--define-component mm-modeline-readonly
  (when buffer-read-only
    (propertize " READONLY" 'face 'mm-modeline-readonly-face)))

(mm-modeline--define-component mm-modeline-buffer-name
  (propertize "%b" 'face 'mm-modeline-buffer-name-face))

(mm-modeline--define-component mm-modeline-buffer-modified
  (when (and (buffer-modified-p)
             (buffer-file-name))
    (propertize " (modified)" 'face 'mm-modeline-buffer-modified-face)))

(defconst mm-modeline-mode-acronyms
  '("css" "csv" "gsp" "html" "json" "mhtml" "scss" "toml" "tsv")
  "List of acronyms in major mode names that should be capitalized.")

(defconst mm-modeline-remap-alist
  '(("Bmenu"   . "BMenu")
    ("Bsdmake" . "BSD Make")
    ("Gmake"   . "GMake")
    ("Imake"   . "IMake")
    ("Js"      . "JavaScript")
    ("Ts Mode" . "Tree-Sitter Mode"))
  "Alist of substrings in major mode names that should be remapped.
Some major modes have substrings that would be better displayed in
another manner.  For example expanding an abbreviation such as ‘Js’ to
its expanded form ‘JavaScript’, or fixing the casing of words with a
prefix such as ‘Gmake’ to ‘GMake’.  This alist maps the original text to
the text it should be mapped to.")

(mm-modeline--define-component mm-modeline-major-mode-name
  (propertize
   (let ((string (thread-last
                   major-mode
                   (symbol-name)
                   (capitalize)
                   (string-replace "-" " ")))
         (case-fold-search nil))
     ;; TODO: Do I need ‘save-match-data’
     (save-match-data
       (dolist (pair mm-modeline-remap-alist)
         (setq string
               (replace-regexp-in-string
                (format "\\<%s\\>" (regexp-quote (car pair)))
                (cdr pair) string)))
       (setq case-fold-search t)
       (if (string-match (regexp-opt mm-modeline-mode-acronyms 'words) string)
           (concat
            (substring string 0 (match-beginning 0))
            (upcase (substring string (match-beginning 0) (match-end 0)))
            (substring string (match-end 0) (length string)))
         string)))
   'face 'mm-modeline-major-mode-name-face))

(mm-modeline--define-component mm-modeline-major-mode-symbol
  (propertize
   (cond
    ((derived-mode-p 'comint-mode)  "$ ")
    ((derived-mode-p 'conf-mode)    "# ")
    ((derived-mode-p 'prog-mode)    "λ ")
    ((derived-mode-p 'special-mode) "❇ ")
    ((derived-mode-p 'text-mode)    "§ ")
    (:default ""))
   'face 'mm-modeline-major-mode-symbol-face))

(mm-modeline--define-component mm-modeline-narrow
  (when (buffer-narrowed-p)
    (propertize
     " Narrow "
     'face 'mm-modeline-narrow-face)))

(mm-modeline--define-component mm-modeline-git-branch
  (when-let ((branch (car (and (featurep 'vc-git)
                               (vc-git-branches)))))
    (concat
     (propertize "\uE907" 'display '(raise 0))
     " "
     (propertize branch 'face 'mm-modeline-git-branch-face)
     " │ ")))


;;; Padding Between Left and Right

(mm-modeline--define-component mm-modeline-left-right-padding
  (let ((length (string-width (format-mode-line mm-modeline-right))))
    (propertize " " 'display `(space :align-to (- right ,length)))))


;;; Configure Modeline

(setopt mode-line-format-right-align 'right-margin)

(setq
 mm-modeline-left (list mm-modeline-narrow
                        mm-modeline-readonly
                        " "
                        mm-modeline-buffer-name
                        mm-modeline-buffer-modified
                        " │ "
                        mm-modeline-major-mode-symbol
                        mm-modeline-major-mode-name
                        mm-modeline-left-right-padding
                        mode-line-end-spaces)
 mm-modeline-right (list mm-modeline-git-branch
                         "%l:%c "))

(setq-default
 mode-line-format
 (list mm-modeline-left mm-modeline-left-right-padding mm-modeline-right))
(provide 'mm-modeline)