;;; redvai.el --- Description -*- lexical-binding: t; -*-
;;
;; Copyright (C) 2024 Tristan Druyen
;;
;; Filename: redvai-mini.el
;; Author: Tristan Druyen <tristand@nixos-fw16>
;; Maintainer: Tristan Druyen <tristand@nixos-fw16>
;; Created: Oktober 09, 2024
;; Modified: November 27, 2024
;; Version: 0.0.1
;; Keywords: convenience extensions tools
;; Homepage: https://git.vlt81.de/vault81/redvault-ai
;; Package-Requires: ((emacs "25.0"))
;;
;; This file is not part of GNU Emacs.
;;
;;; Commentary:
;; - only tested on bleeding-edge emacs, might work on older versions
;; - needs to be compiled with dynamic module support
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;
;;; Change log:
;;
;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;
;; This program 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 program 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 this program; see the file COPYING.  If not, write to
;; the Free Software Foundation, Inc., 51 Franklin Street, Fifth
;; Floor, Boston, MA 02110-1301, USA.
;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;
;;; Code:


(require 's)
(require 'cl-lib)

(defface redvai-overlay-face
  '((t :inherit shadow))
  "Face for redvai overlay")

(defun redvai--set-overlay-text (ov completion)
  "Set overlay OV with COMPLETION."
  (save-restriction
    (widen)
    (let* ((suffix-replace-chars (overlay-get ov 'suffix-replace-chars))
           (p-completion (propertize completion 'face 'redvai-overlay-face)))
      (add-text-properties 0 1 '(cursor 1) p-completion)
      (overlay-put ov 'after-string p-completion)
      (overlay-put ov 'display (char-to-string ?\u200B)) ;; \u200B is a zero-width space. Trick to fix the wrong character inserted position.
      (move-overlay ov (point) (+ (point) 1))
      (overlay-put ov 'completion completion))))

(defvar-local redvai--overlay nil
  "Overlay for redvai completion.")


(defconst redvai-completion-map (make-sparse-keymap)
  "Keymap for Redvai completion overlay.")


(defun redvai--get-overlay ()
  "Create or get overlay for redvai."
  (unless (overlayp redvai--overlay)
    (setq redvai--overlay (make-overlay 1 1 nil nil t))
    (overlay-put redvai--overlay 'keymap redvai-completion-map)
    (overlay-put redvai--overlay 'after-string ""))
  redvai--overlay)


(defun redvai--overlay-visible ()
  "Return t if the overlay is visible."
  (and (overlayp redvai--overlay)
       (overlay-buffer redvai--overlay)))

(defun redvai--test-overlay ()
  "Bla"
  (interactive)
  (redvai--set-overlay-text (redvai--get-overlay) "Test123"))

(defun redvai-complete ()
  (interactive)
  ;; TODO call into module
  ;; (redvai--set-overlay-text (redvai--get-overlay) "Test123")
  )


(defun redvai--clear-overlay ()
  (message "%S" "Cleared")
  (when (redvai--overlay-visible)
    (delete-overlay redvai--overlay)))

(defun redvai-dismiss ()
  "Clear overlay."
  (interactive)
  (redvai--clear-overlay))

(defun redvai--current-completion ()
  (substring-no-properties (overlay-get (redvai--get-overlay) 'after-string)))

(defun redvai-accept-completion ()
  "Bla"
  (interactive)
  (when (redvai--overlay-visible)
    (insert (redvai--current-completion))
    (clear-overlay)))

;;; redvai-mode


(defun redvai--self-insert (command)
  "Handle the case where the char just inserted is the start of the completion.
If so, update the overlays and continue. COMMAND is the
command that triggered `post-command-hook'."
  (when (and (eq command 'self-insert-command)
             (redvai--overlay-visible))
    (let* ((ov redvai--overlay)
           (completion (redvai--current-completion)))
      ;; The char just inserted is the next char of completion
      (when (eq last-command-event (elt completion 0))
        (if (= (length completion) 1)
            ;; If there is only one char in the completion, accept it
            (progn
              (overlay-put ov 'completion "")
              (redvai-accept-completion))
          (redvai--set-overlay-text ov (substring completion 1)))))))


(defcustom redvai-idle-delay 0.2
  "Time in seconds to wait before starting completion.
    Complete immediately if set to 0.
    Disable idle completion if set to nil."
  :type '(choice
          (number :tag "Seconds of delay")
          (const :tag "Idle completion disabled" nil))
  :group 'redvai)


(defun redvai--mode-enter ()
  "Set up redvai mode when entering."
  (add-hook 'post-command-hook 'redvai--post-command nil 'local))

(defun redvai--mode-exit ()
  "Clean up redvai mode when exiting."
  (remove-hook 'post-command-hook #'redvai--post-command 'local))

(defun redvai-turn-on-unless-buffer-read-only ()
  "Turn on `redvai-mode' if the buffer is writable."
  (unless buffer-read-only
    (redvai-mode 1)))


(defun redvai--post-command-debounce (buffer)
  "Complete in BUFFER."
  (when (and (buffer-live-p buffer)
             (equal (current-buffer) buffer)
             redvai-mode)
    (redvai-complete)))


(defun redvai--post-command ()
  "Complete in `post-command-hook' hook."
  (when (and this-command
             (not (and (symbolp this-command)
                       (or
                        (s-starts-with-p "redvai-" (symbol-name this-command))
                        (redvai--self-insert this-command)))))
    (redvai-dismiss)
    (when redvai--post-command-timer
      (cancel-timer redvai--post-command-timer))
    (setq redvai--post-command-timer
          (run-with-idle-timer redvai-idle-delay
                               nil
                               'redvai--post-command-debounce
                               (current-buffer)))))

(advice-add 'keyboard-quit :after #'redvai-dismiss)

;;;###autoload
(define-minor-mode redvai-mode
  "Minor mode for Redvai."
  :init-value nil
  :lighter " Redvai"
  (redvai-dismiss)
  (if redvai-mode
      (redvai--mode-enter)
    (redvai--mode-exit)))

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