;;; pancake.el --- Pancake browser interface -*- lexical-binding: t; -*-

;; Copyright (C) 2017 defanor

;; Author: defanor <defanor@uberspace.net>
;; Maintainer: defanor <defanor@uberspace.net>
;; Created: 2017-10-28
;; Keywords: pandoc, web, gopher, browser
;; Homepage: https://defanor.uberspace.net/projects/pancake/
;; Version: 0.1.0

;; This file is not part of GNU Emacs.

;; 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 of the License, 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.  If not, see <http://www.gnu.org/licenses/>.

;;; Commentary:

;; This is a rather simple interface to the pancake browser.

;;; Code:

(require 'seq)

(defgroup pancake nil
  "Pancake browser interface."
  :prefix "pancake-"
  :group 'applications)

(defface pancake-color-black-foreground
  '((((type graphic) (class color) (background dark)) :foreground "grey")
    (((type graphic) (class color) (background light)) :foreground "black")
    (t :foreground "black"))
  "Foreground face for black color."
  :group 'pancake)

(defface pancake-color-red-foreground
  '((((type graphic) (class color) (background dark)) :foreground "light coral")
    (((type graphic) (class color) (background light)) :foreground "dark red")
    (t :foreground "red"))
  "Foreground face for red color."
  :group 'pancake)

(defface pancake-color-green-foreground
  '((((type graphic) (class color) (background dark)) :foreground "light green")
    (((type graphic) (class color) (background light)) :foreground "dark green")
    (t :foreground "green"))
  "Foreground face for green color."
  :group 'pancake)

(defface pancake-color-yellow-foreground
  '((((type graphic) (class color) (background dark)) :foreground "light yellow")
    (((type graphic) (class color) (background light)) :foreground "yellow4")
    (t :foreground "yellow"))
  "Foreground face for yellow color."
  :group 'pancake)

(defface pancake-color-blue-foreground
  '((((type graphic) (class color) (background dark)) :foreground "light blue")
    (((type graphic) (class color) (background light)) :foreground "dark blue")
    (t :foreground "blue"))
  "Foreground face for blue color."
  :group 'pancake)

(defface pancake-color-magenta-foreground
  '((((type graphic) (class color) (background dark)) :foreground "pink")
    (((type graphic) (class color) (background light)) :foreground "magenta4")
    (t :foreground "magenta"))
  "Foreground face for magenta color."
  :group 'pancake)

(defface pancake-color-cyan-foreground
  '((((type graphic) (class color) (background dark)) :foreground "light cyan")
    (((type graphic) (class color) (background light)) :foreground "dark cyan")
    (t :foreground "cyan"))
  "Foreground face for cyan color."
  :group 'pancake)

(defface pancake-color-white-foreground
  '((((type graphic) (class color) (background dark)) :foreground "white")
    (((type graphic) (class color) (background light)) :foreground "grey")
    (t :foreground "white"))
  "Foreground face for white color."
  :group 'pancake)

(defcustom pancake-command '("pancake")
  "A command that runs pancake, along with its arguments"
  :group 'pancake)

(defvar pancake-buffers '()
  "A list of pancake browser buffers, used to find a buffer to
  use by `pancake-browse-url'.")

(defvar pancake-process-output ""
  "Pancake process's stdout collector.")
(make-variable-buffer-local 'pancake-process-output)

(defvar pancake-process-stderr-output ""
  "Pancake process's stderr collector.")
(make-variable-buffer-local 'pancake-process-stderr-output)

(defvar pancake-process nil
  "Pancake browser process.")
(make-variable-buffer-local 'pancake-process)

;;###autoload
(defun pancake ()
  "Run the pancake browser."
  (interactive)
  (let ((p-buf (generate-new-buffer "*pancake*")))
    (display-buffer p-buf)
    (with-current-buffer p-buf
      (pancake-mode)
      (setq pancake-process
            (let ((process-environment
                   (append
                    (list (format "TERM=%s" (if window-system "xterm"
                                              (or (getenv "TERM") "dumb")))
                          (format "INSIDE_EMACS=%s,pancake" emacs-version)
                          (format "COLUMNS=%d" (1- (window-width))))
                    process-environment)))
              (make-process
               :name "pancake"
               :buffer p-buf
               :command pancake-command
               :stderr (make-pipe-process
                        :name "*pancake-stderr*"
                        :filter 'pancake-process-stderr-filter
                        :sentinel 'pancake-process-stderr-sentinel)
               :filter 'pancake-process-filter
               :sentinel 'pancake-process-sentinel)))
      (push p-buf pancake-buffers)
      (read-only-mode 1))))

;;###autoload
(defun pancake-browse-url (url &optional new-session)
  "Browse an URL with pancake, suitable for setting as
`browse-url-browser-function'."
  (when (or new-session (not (consp pancake-buffers)))
    (pancake))
  (with-current-buffer (car pancake-buffers)
    (process-send-string pancake-process (concat url "\n"))
    (display-buffer (current-buffer))))

(defun pancake-translate-color (name attr)
  "Translate pancake colors into emacs faces."
  (intern (concat "pancake-color-"
                  (downcase (symbol-name name))
                  "-"
                  (symbol-name attr))))

(defun pancake-print-elem (element)
  "Translate ELEMENT into a string."
  (if (stringp element)
      element
    (pcase element
      (`(fg (,color) . ,rest)
       (let ((inner (pancake-print-line rest)))
         (add-face-text-property
          0 (length inner) (pancake-translate-color color 'foreground) t inner)
         inner))
      (`(bg (,color) . ,rest)
       (let ((inner (pancake-print-line rest)))
         (add-face-text-property
          0 (length inner) (pancake-translate-color color 'background) t inner)
         inner))
      (`(style Bold . ,rest)
       (let ((inner (pancake-print-line rest)))
         (add-face-text-property 0 (length inner) 'bold t inner)
         inner))
      (`(style Underline . ,rest)
       (let ((inner (pancake-print-line rest)))
         (add-face-text-property 0 (length inner) 'underline t inner)
         inner))
      (`(style Italic . ,rest)
       (let ((inner (pancake-print-line rest)))
         (add-face-text-property 0 (length inner) 'italic t inner)
         inner))
      (_ (format "%S" element)))))


(defun pancake-print-line (line)
  "Translate LINE (a list of elements) into a string"
  (apply 'concat (mapcar 'pancake-print-elem line)))

(defun pancake-line-p (string)
  "Return t if STRING ends with a newline character."
  (char-equal (elt string (- (length string) 1)) ?\n))

(defun pancake-process-filter (proc string)
  "Pancake process filter for stdout."
  (when (buffer-live-p (process-buffer proc))
    (with-current-buffer (process-buffer proc)
      (read-only-mode -1)
      (delete-region (point-min) (point-max))
      (setq pancake-process-output (concat pancake-process-output string))
      (when (pancake-line-p pancake-process-output)
        (dolist (line (read pancake-process-output))
          (insert (pancake-print-line line))
          (newline))
        (goto-char (point-min))
        (setq pancake-process-output ""))
      (read-only-mode 1))))

(defun pancake-process-stderr-filter (proc string)
  "Pancake process filter for stderr."
  (setq pancake-process-stderr-output
        (concat pancake-process-stderr-output string))
  (when (pancake-line-p pancake-process-stderr-output)
    (message "pancake: %s" (string-trim pancake-process-stderr-output))
    (setq pancake-process-stderr-output "")))

(defun pancake-process-sentinel (process event)
  "Pancake process sentinel for stdout."
  (let ((buf (process-buffer process)))
    (when (and (not (process-live-p process))
               (buffer-live-p (process-buffer process)))
      (kill-buffer buf))
    (setq pancake-buffers
          (seq-remove (lambda (x) (eq x buf)) pancake-buffers))))

(defun pancake-process-stderr-sentinel (process event)
  "Pancake process sentinel for stderr."
  (when (and (not (process-live-p process))
             (buffer-live-p (process-buffer process)))
    (kill-buffer (process-buffer process))))

(defun pancake-interrupt ()
  "Send SIGINT to the process."
  (interactive)
  (interrupt-process pancake-process))

(defun pancake-yank ()
  "Insert a string."
  (interactive)
  (funcall (pancake-input (current-kill 0))))

(defun pancake-yank-primary ()
  "Insert a string from the primary selection."
  (interactive)
  (funcall (pancake-input (gui-get-primary-selection))))

(defun pancake-input (string)
  "Pancake input handler: opens minibuffer for input.
Sets the initial contents to STRING, reads the rest, and passes
it to `pancake-process' as input."
  (lambda ()
    (interactive)
    (process-send-string
     pancake-process
     (concat (read-from-minibuffer "" string) "\n"))))

(defvar pancake-mode-map
  (let ((map (make-sparse-keymap))
        (chars (append (list ?? ?. ?/)
                       (number-sequence ?0 ?9)
                       (number-sequence ?a ?z))))
    (dolist (char chars)
      (let ((str (char-to-string char)))
        (define-key map (kbd str) (pancake-input str))))
    (define-key map (kbd "C-y") 'pancake-yank)
    (define-key map (kbd "<mouse-2>") 'pancake-yank-primary)
    (define-key map (kbd "C-c C-c") 'pancake-interrupt)
    map)
  "Keymap for `pancake-mode'.")

(define-derived-mode pancake-mode nil "Pancake"
  "A basic emacs interface to the pancake browser.")

(provide 'pancake)

;;; pancake.el ends here