;;; my-spc.el -- handling spc files -*- lexical-binding: t -*-

;; Copyright (C) 2023 Free Software Foundation.

;; Author: Yuchen Pei <id@ypei.org>
;;         Warren Wilkinson <warrenwilkinson@gmail.com>
;; Maintainer: Yuchen Pei <id@ypei.org>
;; Package-Requires: ((emacs "28"))

;; This file is part of dotted.

;; dotted is free software: you can redistribute it and/or modify it under
;; the terms of the GNU Affero General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.

;; dotted 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 Affero General
;; Public License for more details.

;; You should have received a copy of the GNU Affero General Public
;; License along with dotted.  If not, see <https://www.gnu.org/licenses/>.

;;; Commentary:

;; handling spc files.

;;; Code:

(require 'bindat)

(defconst my-spc--id666-magic-array
  [#x53 #x4e #x45 #x53 #x2d #x53 #x50#x43 #x37 #x30 #x30 #x20 #x53 #x6f #x75 #x6e #x64 #x20 #x46 #x69 #x6c #x65 #x20 #x44 #x61 #x74 #x61 #x20 #x76 #x30 #x2e #x33 #x30]
  "id666 header magic pattern `SNES-SPC700 Sound File Data v0.30'")

(defconst my-spc--id666-header-bindat-spec
  '((file-identifier vec 33)
    (eval (unless (equal last my-spc--id666-magic-array)
            (error "id666 framing mismatch: expected `%s', got `%s'"
                   my-spc--id666-magic-array
                   last)))
    (unused u16)
    (has-id666 u8)
    (revision u8)
    (pc-reg u16)
    (a-reg u8)
    (x-reg u8)
    (y-reg u8)
    (psw-reg u8)
    (sp-reg u8)
    (res-reg u16)
    (song-title strz 32)
    (game-title strz 32)
    (dumper strz 16)
    (comment strz 32)
    (date strz 11)
    (fadeout vec 3)
    (fadeout-length vec 5)
    (artist strz 32))
  "id666 header specification.

Sources:

- URL `https://ocremix.org/info/SPC_Format_Specification'
- URL `https://picard-docs.musicbrainz.org/en/appendices/tag_mapping.html'")

(defun my-spc--decode-id666-header (filename)
  "Read and decode id666 header from FILENAME."
  (with-temp-buffer
    (set-buffer-multibyte nil)
    (insert-file-contents-literally filename nil 0 210)
    (bindat-unpack my-spc--id666-header-bindat-spec
                   (buffer-string))))

(defun my-spc-decode-id666 (filename)
  "Read and decode id666 metadata from FILENAME.
Return metadata in a list of (FIELD . VALUE) cons cells, or nil
in case of errors or if there were no known fields in FILENAME."
  (condition-case nil
      (let ((header (my-spc--decode-id666-header filename)))
        (when (= 26 (bindat-get-field header 'has-id666))
          `(
            (title . ,(bindat-get-field header 'song-title))
            (album . ,(bindat-get-field header 'game-title))
            (artist . ,(bindat-get-field header 'artist))
            (comment . ,(bindat-get-field header 'comment))
            (dumper . ,(bindat-get-field header 'dumper))
            (date . ,(bindat-get-field header 'date))
            (fadeout . ,(bindat-get-field header 'fadeout))
            (fadeout-length . ,(bindat-get-field header 'fadeout))
            (extension . ,(file-name-extension filename))
            (number . ,(replace-regexp-in-string
                        "[^-]+-" ""
                        (file-name-base filename)))
            )))
    (error nil)))

(defun my-spc-format-file-name (file)
  "Format a filename from an spc FILE.

artist/album/title (note).extension"
  (when-let* ((metadata (my-spc-decode-id666 file))
              (artist (alist-get 'artist metadata))
              (album (alist-get 'album metadata))
              (title (alist-get 'title metadata))
              (extension (alist-get 'extension metadata))
              (number (alist-get 'number metadata)))
    (if (or (string-empty-p artist)
            (string-empty-p album)
            (string-empty-p title)
            (string-empty-p extension)
            (string-empty-p number))
        nil
      (format "%s/%s/%s %s.%s" artist album number title extension))))

(defun my-spc-file-rename (dir)
  "Rename all spc files under DIR using dired."
  (let ((pairs
         (seq-filter
          'cdr
          (mapcar
           (lambda (file)
             (cons (expand-file-name file)
                   (format "%s/%s"
                           (expand-file-name my-audio-incoming-dir)
                           (my-spc-format-file-name file))))
           (directory-files-recursively dir "\\`.*\\.spc\\'")))))
    (when (y-or-n-p
           (print
            (format
             "Will do the following renaming: %s\nContinue?"
             (string-join
              (mapcar (lambda (pair)
                        (format "%s -> %s" (car pair) (cdr pair)))
                      pairs)
              "\n"))))
      (mapc
       (lambda (pair)
         (dired-rename-file (car pair) (cdr pair) t))
       pairs))))

(provide 'my-spc)
;;; my-spc.el ends here