;;; zcomplete.el --- highlight and natural move throw *Completions* buffer -*- lexical-binding: t -*-

;; Copyright (C) 2020 Free Software Foundation, Inc.

;; Author: Jimmy Aguilar Mena <spacibba at aol dot com>
;; Created: Aug 2020 Jimmy Aguilar Mena spacibba@aol.com
;; Keywords: help, abbrev

;; This file is part of GNU Emacs.

;; GNU Emacs 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 of the License, or
;; (at your option) any later version.

;; GNU Emacs 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.  If not, see <https://www.gnu.org/licenses/>.

;;; Commentary:

;; This package has 2 different functionalities:
;; 1) zcomplete-mode: To auto-skip the completion buffers more often
;; 1) zcomplete-highlight-mode: To highlight current candidate

;;; Code:

(require 'simple)
(require 'minibuffer)

;; zcomplete-highlight-mode ==========================================
(defgroup zcomplete nil
  "Highlight candidates in completions buffer."
  :version "28.1"
  :group 'completion)

(defface zcomplete-highlight
  '((t :inherit highlight :extend t))
  "Default face for highlighting the current line in Hl-Line mode."
  :version "28.1"
  :group 'zcomplete)

(defvar zcomplete--overlay nil
  "Overlay to use when `zcomplete-highlight-mode' is enabled.")

(defun zcomplete-highlight--pre-hook ()
  "Highlight current candidate in *Completions* when ``zcomplete-highlight''."
  (when (overlayp zcomplete--overlay)
    (delete-overlay zcomplete--overlay)))

(defun zcomplete-highlight--highlight ()
  "Highlight current candidate if point in a candidate."
  (let* ((point (point))
         (hpoint (or (and (get-text-property point 'mouse-face) point)
                     (and (get-text-property (1- point) 'mouse-face) (1- point)))))
    (when hpoint
      (move-overlay zcomplete--overlay
                    (previous-single-property-change (1+ hpoint) 'mouse-face nil (point-min))
                    (next-single-property-change hpoint 'mouse-face nil (point-max))))))

(defun zcomplete-highlight--setup-hook ()
  "Function to call when enabling the `completion-highlight-mode' mode.
It is called when showing the *Completions* buffer."
  (with-current-buffer "*Completions*"
    (zcomplete-highlight--highlight)
    (add-hook 'pre-command-hook #'zcomplete-highlight--pre-hook nil t)
    (add-hook 'post-command-hook #'zcomplete-highlight--highlight nil t)))

;;;###autoload
(define-minor-mode zcomplete-highlight-mode
  "Completion highlight mode to enable candidates highlight in the minibuffer."
  :global t
  :group 'minibuffer
  (cond
   (zcomplete-highlight-mode
    (setq zcomplete--overlay (make-overlay 0 0))
    (overlay-put zcomplete--overlay 'face 'zcomplete-highlight)
    (add-hook 'completion-setup-hook #'zcomplete-highlight--setup-hook t))
   (t
    (remove-hook 'completion-setup-hook #'zcomplete-highlight--setup-hook)
    (delete-overlay zcomplete--overlay))))

;; zcomplete-mode ====================================================

(defvar-keymap zcomplete-map
  :doc "Keymap used in *Completions* on ``zcomplete-mode''"
  :parent completion-list-mode-map
  "z" nil
  "n" nil
  "p" nil
  "q" nil
  "g" nil
  "h" nil
  "DEL" nil)

(defun zcomplete--try-on-minibuffer ()
  "Try to execute the binding on minibuffer."
  (switch-to-minibuffer)
  (if-let ((command (lookup-key (current-active-maps)
                                (this-single-command-keys))))
      (progn
        (minibuffer-hide-completions)
        (call-interactively command)
        t)
    (switch-to-completions)
    nil))

(defun zcomplete--pre-hook ()
  "Try on minibuffer when the command is not in *Completions* map."
  (when (eq this-command 'undefined)
    (zcomplete--try-on-minibuffer)))

(defun zcomplete--hack (data context signal)
  "Alternative to command-error-default-function.
This will try to execute on minibuffer, else emits the error"
  (unless (and (string= (buffer-name) "*Completions*")
               (zcomplete--try-on-minibuffer))
    (command-error-default-function data context signal)))

(defun zcomplete--setup-hook ()
  "Function to call when enabling the `completion-highlight-mode' mode.
It is called when showing the *Completions* buffer."
  (with-current-buffer "*Completions*"
    (setq-local command-error-function #'zcomplete--hack
                mode-line-format nil)
    (use-local-map zcomplete-map)
    (add-hook 'pre-command-hook #'zcomplete--pre-hook nil t)))

;;;###autoload
(define-minor-mode zcomplete-mode
  "Completion auto-jump to the minibuffer."
  :global t
  :group 'minibuffer
  (if zcomplete-mode
      (add-hook 'completion-setup-hook #'zcomplete--setup-hook t)
    (remove-hook 'completion-setup-hook #'zcomplete--setup-hook)))

(provide 'zcomplete)
;;; zcomplete.el ends here