;;; test-music-config--append-track-to-m3u-file.el --- Tests for appending tracks to M3U files -*- coding: utf-8; lexical-binding: t; -*-
;;
;; Author: Craig Jennings <c@cjennings.net>
;;
;;; Commentary:
;; Unit tests for cj/music--append-track-to-m3u-file function.
;; Tests the pure, deterministic helper that appends track paths to M3U files.
;;
;; Test organization:
;; - Normal Cases: Standard append operations
;; - Boundary Cases: Edge conditions (unicode, long paths, special chars)
;; - Error Cases: File errors (missing, read-only, directory instead of file)
;;
;;; Code:

(require 'ert)
(require 'testutil-general)

;; Stub missing dependencies before loading music-config
(defvar-keymap cj/custom-keymap
  :doc "Stub keymap for testing")

;; Load production code
(require 'music-config)

;;; Setup & Teardown

(defun test-music-config--append-track-to-m3u-file-setup ()
  "Setup test environment."
  (cj/create-test-base-dir))

(defun test-music-config--append-track-to-m3u-file-teardown ()
  "Clean up test environment."
  (cj/delete-test-base-dir))

;;; Normal Cases

(ert-deftest test-music-config--append-track-to-m3u-file-normal-empty-file-appends-track ()
  "Append to brand new empty M3U file."
  (test-music-config--append-track-to-m3u-file-setup)
  (unwind-protect
      (let* ((m3u-file (cj/create-temp-test-file "test-playlist-"))
             (track-path "/home/user/music/artist/song.mp3"))
        (cj/music--append-track-to-m3u-file track-path m3u-file)
        (with-temp-buffer
          (insert-file-contents m3u-file)
          (should (string= (buffer-string) (concat track-path "\n")))))
    (test-music-config--append-track-to-m3u-file-teardown)))

(ert-deftest test-music-config--append-track-to-m3u-file-normal-existing-with-newline-appends-track ()
  "Append to file with existing content ending with newline."
  (test-music-config--append-track-to-m3u-file-setup)
  (unwind-protect
      (let* ((existing-content "/home/user/music/first.mp3\n")
             (m3u-file (cj/create-temp-test-file-with-content existing-content "test-playlist-"))
             (track-path "/home/user/music/second.mp3"))
        (cj/music--append-track-to-m3u-file track-path m3u-file)
        (with-temp-buffer
          (insert-file-contents m3u-file)
          (should (string= (buffer-string)
                          (concat existing-content track-path "\n")))))
    (test-music-config--append-track-to-m3u-file-teardown)))

(ert-deftest test-music-config--append-track-to-m3u-file-normal-existing-without-newline-appends-track ()
  "Append to file without trailing newline adds leading newline."
  (test-music-config--append-track-to-m3u-file-setup)
  (unwind-protect
      (let* ((existing-content "/home/user/music/first.mp3")
             (m3u-file (cj/create-temp-test-file-with-content existing-content "test-playlist-"))
             (track-path "/home/user/music/second.mp3"))
        (cj/music--append-track-to-m3u-file track-path m3u-file)
        (with-temp-buffer
          (insert-file-contents m3u-file)
          (should (string= (buffer-string)
                          (concat existing-content "\n" track-path "\n")))))
    (test-music-config--append-track-to-m3u-file-teardown)))

(ert-deftest test-music-config--append-track-to-m3u-file-normal-multiple-appends-all-succeed ()
  "Multiple appends to same file all succeed (allows duplicates)."
  (test-music-config--append-track-to-m3u-file-setup)
  (unwind-protect
      (let* ((m3u-file (cj/create-temp-test-file "test-playlist-"))
             (track1 "/home/user/music/track1.mp3")
             (track2 "/home/user/music/track2.mp3")
             (track1-duplicate "/home/user/music/track1.mp3"))
        (cj/music--append-track-to-m3u-file track1 m3u-file)
        (cj/music--append-track-to-m3u-file track2 m3u-file)
        (cj/music--append-track-to-m3u-file track1-duplicate m3u-file)
        (with-temp-buffer
          (insert-file-contents m3u-file)
          (let ((content (buffer-string)))
            (should (string= content
                            (concat track1 "\n" track2 "\n" track1-duplicate "\n"))))))
    (test-music-config--append-track-to-m3u-file-teardown)))

;;; Boundary Cases

(ert-deftest test-music-config--append-track-to-m3u-file-boundary-very-long-path-appends-successfully ()
  "Append very long track path without truncation."
  (test-music-config--append-track-to-m3u-file-setup)
  (unwind-protect
      (let* ((m3u-file (cj/create-temp-test-file "test-playlist-"))
             ;; Create a path that's ~500 chars long
             (track-path (concat "/home/user/music/"
                                (make-string 450 ?a)
                                "/song.mp3")))
        (cj/music--append-track-to-m3u-file track-path m3u-file)
        (with-temp-buffer
          (insert-file-contents m3u-file)
          (should (string= (buffer-string) (concat track-path "\n")))
          (should (= (length (buffer-string)) (1+ (length track-path))))))
    (test-music-config--append-track-to-m3u-file-teardown)))

(ert-deftest test-music-config--append-track-to-m3u-file-boundary-path-with-unicode-appends-successfully ()
  "Append path with unicode characters preserves UTF-8 encoding."
  (test-music-config--append-track-to-m3u-file-setup)
  (unwind-protect
      (let* ((m3u-file (cj/create-temp-test-file "test-playlist-"))
             (track-path "/home/user/music/中文/artist-名前/song🎵.mp3"))
        (cj/music--append-track-to-m3u-file track-path m3u-file)
        (with-temp-buffer
          (insert-file-contents m3u-file)
          (should (string= (buffer-string) (concat track-path "\n")))))
    (test-music-config--append-track-to-m3u-file-teardown)))

(ert-deftest test-music-config--append-track-to-m3u-file-boundary-path-with-spaces-appends-successfully ()
  "Append path with spaces and special characters."
  (test-music-config--append-track-to-m3u-file-setup)
  (unwind-protect
      (let* ((m3u-file (cj/create-temp-test-file "test-playlist-"))
             (track-path "/home/user/music/Artist Name/Album (2024)/01 - Song's Title [Remix].mp3"))
        (cj/music--append-track-to-m3u-file track-path m3u-file)
        (with-temp-buffer
          (insert-file-contents m3u-file)
          (should (string= (buffer-string) (concat track-path "\n")))))
    (test-music-config--append-track-to-m3u-file-teardown)))

(ert-deftest test-music-config--append-track-to-m3u-file-boundary-m3u-with-comments-appends-after ()
  "Append to M3U file containing comments and metadata."
  (test-music-config--append-track-to-m3u-file-setup)
  (unwind-protect
      (let* ((existing-content "#EXTM3U\n#EXTINF:-1,Radio Station\nhttp://stream.url/radio\n")
             (m3u-file (cj/create-temp-test-file-with-content existing-content "test-playlist-"))
             (track-path "/home/user/music/local-track.mp3"))
        (cj/music--append-track-to-m3u-file track-path m3u-file)
        (with-temp-buffer
          (insert-file-contents m3u-file)
          (should (string= (buffer-string)
                          (concat existing-content track-path "\n")))))
    (test-music-config--append-track-to-m3u-file-teardown)))

;;; Error Cases

(ert-deftest test-music-config--append-track-to-m3u-file-error-nonexistent-file-signals-error ()
  "Signal error when M3U file doesn't exist."
  (test-music-config--append-track-to-m3u-file-setup)
  (unwind-protect
      (let* ((m3u-file "/nonexistent/path/to/playlist.m3u")
             (track-path "/home/user/music/song.mp3"))
        (should-error (cj/music--append-track-to-m3u-file track-path m3u-file)
                     :type 'error))
    (test-music-config--append-track-to-m3u-file-teardown)))

(ert-deftest test-music-config--append-track-to-m3u-file-error-readonly-file-signals-error ()
  "Signal error when M3U file is read-only."
  (test-music-config--append-track-to-m3u-file-setup)
  (unwind-protect
      (let* ((m3u-file (cj/create-temp-test-file "test-playlist-"))
             (track-path "/home/user/music/song.mp3"))
        ;; Make file read-only
        (set-file-modes m3u-file #o444)
        (should-error (cj/music--append-track-to-m3u-file track-path m3u-file)
                     :type 'error))
    (test-music-config--append-track-to-m3u-file-teardown)))

(ert-deftest test-music-config--append-track-to-m3u-file-error-directory-not-file-signals-error ()
  "Signal error when path points to directory instead of file."
  (test-music-config--append-track-to-m3u-file-setup)
  (unwind-protect
      (let* ((m3u-dir (cj/create-test-subdirectory "test-playlist-dir"))
             (track-path "/home/user/music/song.mp3"))
        (should-error (cj/music--append-track-to-m3u-file track-path m3u-dir)
                     :type 'error))
    (test-music-config--append-track-to-m3u-file-teardown)))

(provide 'test-music-config--append-track-to-m3u-file)
;;; test-music-config--append-track-to-m3u-file.el ends here