;;; ui/ligatures/config.el -*- lexical-binding: t; -*-

(defvar +ligatures-extra-symbols
  '(;; org
    :name          "»"
    :src_block     "»"
    :src_block_end "«"
    :quote         "“"
    :quote_end     "”"
    ;; Functional
    :lambda        "λ"
    :def           "ƒ"
    :composition   "∘"
    :map           "↦"
    ;; Types
    :null          "∅"
    :true          "𝕋"
    :false         "𝔽"
    :int           "ℤ"
    :float         "ℝ"
    :str           "𝕊"
    :bool          "𝔹"
    :list          "𝕃"
    ;; Flow
    :not           "￢"
    :in            "∈"
    :not-in        "∉"
    :and           "∧"
    :or            "∨"
    :for           "∀"
    :some          "∃"
    :return        "⟼"
    :yield         "⟻"
    ;; Other
    :union         "⋃"
    :intersect     "∩"
    :diff          "∖"
    :tuple         "⨂"
    :pipe          "" ;; FIXME: find a non-private char
    :dot           "•")
  "Maps identifiers to symbols, recognized by `set-ligatures'.

This should not contain any symbols from the Unicode Private Area! There is no
universal way of getting the correct symbol as that area varies from font to
font.")

(defvar +ligatures-extra-alist '((t))
  "A map of major modes to symbol lists (for `prettify-symbols-alist').")

(defvar +ligatures-prog-mode-list
  '("|||>" "<|||" "<==>" "<!--" "####" "~~>" "***" "||=" "||>"
    ":::" "::=" "=:=" "===" "==>" "=!=" "=>>" "=<<" "=/=" "!=="
    "!!." ">=>" ">>=" ">>>" ">>-" ">->" "->>" "-->" "---" "-<<"
    "<~~" "<~>" "<*>" "<||" "<|>" "<$>" "<==" "<=>" "<=<" "<->"
    "<--" "<-<" "<<=" "<<-" "<<<" "<+>" "</>" "###" "#_(" "..<"
    "..." "+++" "/==" "///" "_|_" "www" "&&" "^=" "~~" "~@" "~="
    "~>" "~-" "**" "*>" "*/" "||" "|}" "|]" "|=" "|>" "|-" "{|"
    "[|" "]#" "::" ":=" ":>" ":<" "$>" "==" "=>" "!=" "!!" ">:"
    ">=" ">>" ">-" "-~" "-|" "->" "--" "-<" "<~" "<*" "<|" "<:"
    "<$" "<=" "<>" "<-" "<<" "<+" "</" "#{" "#[" "#:" "#=" "#!"
    "##" "#(" "#?" "#_" "%%" ".=" ".-" ".." ".?" "+>" "++" "?:"
    "?=" "?." "??" ";;" "/*" "/=" "/>" "//" "__" "~~" "(*" "*)"
    "\\\\" "://")
  "A list of ligatures to enable in all `prog-mode' buffers.")

(defvar +ligatures-all-modes-list
  '()
  "A list of ligatures to enable in all buffers.")

(defvar +ligatures-in-modes
  '(not special-mode comint-mode eshell-mode term-mode vterm-mode Info-mode
        elfeed-search-mode elfeed-show-mode)
  "List of major modes where ligatures should be enabled.

  If t, enable it everywhere (except `fundamental-mode').
  If the first element is 'not, enable it in any mode besides what is listed.
  If nil, don't enable ligatures anywhere.")

(defvar +ligatures-extras-in-modes t
  "List of major modes where extra ligatures should be enabled.

Extra ligatures are mode-specific substituions, defined in
`+ligatures-extra-symbols' and assigned with `set-ligatures!'. This variable
controls where these are enabled.

  If t, enable it everywhere (except `fundamental-mode').
  If the first element is 'not, enable it in any mode besides what is listed.
  If nil, don't enable these extra ligatures anywhere (though it's more
efficient to remove the `+extra' flag from the :ui ligatures module instead).")

(defvar +ligatures--init-font-hook nil)

(defun +ligatures--correct-symbol-bounds (ligature-alist)
  "Prepend non-breaking spaces to a ligature.

This way `compose-region' (called by `prettify-symbols-mode') will use the
correct width of the symbols instead of the width measured by `char-width'."
  (let ((len (length (car ligature-alist)))
        (acc (list   (cdr ligature-alist))))
    (while (> len 1)
      (setq acc (cons #X00a0 (cons '(Br . Bl) acc))
            len (1- len)))
    (cons (car ligature-alist) acc)))

(defun +ligatures--enable-p (modes)
  "Return t if ligatures should be enabled in this buffer depending on MODES."
  (unless (eq major-mode 'fundamental-mode)
    (or (eq modes t)
        (if (eq (car modes) 'not)
            (not (apply #'derived-mode-p (cdr modes)))
          (apply #'derived-mode-p modes)))))

(defun +ligatures-init-buffer-h ()
  "Set up ligatures for the current buffer.

Extra ligatures are mode-specific substituions, defined in
`+ligatures-extra-symbols', assigned with `set-ligatures!', and made possible
with `prettify-symbols-mode'. This variable controls where these are enabled.
See `+ligatures-extras-in-modes' to control what major modes this function can
and cannot run in."
  (when after-init-time
    (let ((in-mode-p
           (+ligatures--enable-p +ligatures-in-modes))
          (in-mode-extras-p
           (and (modulep! +extra)
                (+ligatures--enable-p +ligatures-extras-in-modes))))
      (when in-mode-p
        ;; If ligature-mode has been installed, there's no
        ;; need to do anything, we activate global-ligature-mode
        ;; later and handle all settings from `set-ligatures!' later.
        (unless (fboundp #'ligature-mode-turn-on)
          (run-hooks '+ligatures--init-font-hook)
          (setq +ligatures--init-font-hook nil)))
      (when in-mode-extras-p
        (prependq! prettify-symbols-alist
                   (alist-get major-mode +ligatures-extra-alist)))
      (when (and (or in-mode-p in-mode-extras-p)
                 prettify-symbols-alist)
        (when prettify-symbols-mode
          (prettify-symbols-mode -1))
        (prettify-symbols-mode +1)))))


;;
;;; Bootstrap

;;;###package prettify-symbols
;; When you get to the right edge, it goes back to how it normally prints
(setq prettify-symbols-unprettify-at-point 'right-edge)

(add-hook! 'doom-init-ui-hook :append
  (defun +ligatures-init-h ()
    (add-hook 'after-change-major-mode-hook #'+ligatures-init-buffer-h)))

(cond
 ;; The emacs-mac build of Emacs appears to have built-in support for ligatures,
 ;; using the same composition-function-table method
 ;; https://bitbucket.org/mituharu/emacs-mac/src/26c8fd9920db9d34ae8f78bceaec714230824dac/lisp/term/mac-win.el?at=master#lines-345:805
 ;; so use that instead if this module is enabled.
 ((if (featurep :system 'macos)
      (fboundp 'mac-auto-operator-composition-mode))
  (add-hook 'doom-init-ui-hook #'mac-auto-operator-composition-mode 'append))

 ;; NOTE: the module does not support Emacs 27 and less, but if we still try to enable ligatures,
 ;; it will end up in catastrophic work-loss errors, so we leave the check here for safety.
 ((and (> emacs-major-version 27)
       (or (featurep 'ns)
           (string-match-p "HARFBUZZ" system-configuration-features))
       (featurep 'composite))           ; Emacs loads `composite' at startup

  (use-package! ligature
    :config
    ;; Enable all `+ligatures-prog-mode-list' ligatures in programming modes
    (ligature-set-ligatures 'prog-mode +ligatures-prog-mode-list)
    (ligature-set-ligatures 't +ligatures-all-modes-list))

  (add-hook! 'doom-init-ui-hook :append
    (defun +ligature-enable-globally-h ()
      "Enables ligature checks globally in all buffers.
You can also do it per mode with `ligature-mode'."
      (global-ligature-mode t)))))