;;; naviel.el --- Navidrome music player client for Emacs -*- lexical-binding: t -*-

;; Author: CdatGoose
;; Version: 0.1
;; Package-Requires: ((emacs "28.1"))
;; Keywords: multimedia, music

;;; Commentary:
;; A Navidrome client for Emacs using the Subsonic API.
;; Plays music via mpv (must be installed on PATH).
;; This project is glued tegether by sheer hope, I don't know elisp and probably never will.


;; Quick setup:
;;   1. ~/.authinfo:  machine your-host login USER password PASS
;;   2. (setq naviel-url "http://host:4533")
;;   3. M-x naviel


(require 'url)
(require 'url-util)
(require 'xml)
(require 'auth-source)
(require 'cl-lib)
(require 'json)

;;; Customisation 

(defgroup naviel nil
  "Naviel music client."
  :group 'multimedia
  :prefix "naviel-")

(defcustom naviel-url "http://localhost:4533"
  "Base URL of the Navidrome server (no trailing slash)."
  :type 'string :group 'naviel)

(defcustom naviel-username nil
  "Username. If nil, looked up from ~/.authinfo."
  :type '(choice (const nil) string) :group 'naviel)

(defcustom naviel-password nil
  "Password. If nil, looked up from ~/.authinfo."
  :type '(choice (const nil) string) :group 'naviel)

(defcustom naviel-client-name "naviel.el"
  "Client identifier sent with every API request."
  :type 'string :group 'naviel)

(defcustom naviel-api-version "1.16.1"
  "Subsonic API version declared in requests."
  :type 'string :group 'naviel)

(defcustom naviel-mpv-executable "mpv"
  "Path to the mpv executable."
  :type 'string :group 'naviel)

(defcustom naviel-volume-step 5
  "Volume increment/decrement step (0-100)."
  :type 'integer :group 'naviel)

(defcustom naviel-seek-step 10
  "Seek step in seconds for the < / > keys."
  :type 'integer :group 'naviel)

(defcustom naviel-position-poll-interval 1.0
  "Seconds between IPC polls for playback position."
  :type 'float :group 'naviel)

;;; Faces 

(defface naviel-header-face       '((t :inherit bold :height 1.15))           "Main header.")
(defface naviel-separator-face    '((t :inherit shadow))                       "Separator lines.")
(defface naviel-artist-face       '((t :inherit font-lock-function-name-face
                                       :weight semi-bold))                     "Artist names.")
(defface naviel-album-face        '((t :inherit font-lock-string-face))        "Album names.")
(defface naviel-song-title-face   '((t :inherit default))                      "Song titles.")
(defface naviel-song-meta-face    '((t :inherit shadow))                       "Song metadata.")
(defface naviel-track-num-face    '((t :inherit shadow))                       "Track numbers.")
(defface naviel-year-face         '((t :inherit shadow))                       "Album years.")
(defface naviel-now-playing-face  '((t :inherit success :weight bold))         "Now-playing text.")
(defface naviel-paused-face       '((t :inherit warning :weight bold))         "Paused indicator.")
(defface naviel-footer-face       '((t :inherit shadow :height 0.85))          "Footer hints.")
(defface naviel-count-face        '((t :inherit shadow))                       "Item counts.")
(defface naviel-breadcrumb-face   '((t :inherit font-lock-comment-face))       "Breadcrumb trail.")
(defface naviel-repeat-face       '((t :inherit font-lock-keyword-face))       "Repeat mode.")
(defface naviel-error-face        '((t :inherit error))                        "In-buffer errors.")
(defface naviel-position-face     '((t :inherit shadow))                       "Playback position.")

;;; Repeat mode

(defvar naviel-repeat-mode 'off
  "Playback repeat mode: \\='off, \\='one, or \\='album.")

(defun naviel-toggle-repeat ()
  "Cycle repeat mode: off → one → album → off."
  (interactive)
  (setq naviel-repeat-mode
        (pcase naviel-repeat-mode ('off 'one) ('one 'album) (_ 'off)))
  (naviel--refresh-footer)
  (message "Repeat: %s" (naviel--repeat-label)))

(defun naviel--repeat-label ()
  (pcase naviel-repeat-mode ('one "one") ('album "all") (_ "off")))

;;; Internal state 

;; mpv process and IPC
(defvar naviel--process         nil  "The mpv OS process.")
(defvar naviel--ipc-process     nil  "Persistent mpv IPC network process.")
(defvar naviel--ipc-buffer      ""   "Accumulated un-parsed IPC bytes.")
(defvar naviel--ipc-request-id  0    "Monotonically increasing request id.")
(defvar naviel--ipc-callbacks   nil  "Alist of (id . callback) for pending IPC requests.")
(defvar naviel--position-timer  nil  "Timer that polls mpv for time-pos.")
(defvar naviel--elapsed         nil  "Elapsed seconds (float or nil).")
(defvar naviel--duration        nil  "Track duration in seconds (float or nil).")

;; Queue / playback
(defvar naviel--queue        '() "Current play queue — list of song plists.")
(defvar naviel--queue-index   0  "Index of the currently playing track.")
(defvar naviel--volume        80 "Current volume 0-100.")
(defvar naviel--paused        nil "Non-nil when paused.")
(defvar naviel--current-song  nil "Plist of the currently playing song.")

;; Browser
(defvar naviel--browser-stack '() "Navigation stack; each entry is a plist.")
(defvar naviel--current-view  nil "Plist describing the rendered view.")

;; Mode line
(defvar naviel--mode-line-timer nil "Timer for mode-line refreshes.")

;;; Authentication 

(defun naviel--credentials ()
  "Return (USER . PASS) from customisation variables or ~/.authinfo."
  (let* ((host (url-host (url-generic-parse-url naviel-url)))
         (user (or naviel-username
                   (plist-get (car (auth-source-search :host host :require '(:user))) :user)))
         (pass (or naviel-password
                   (let* ((entry (car (auth-source-search :host host :require '(:secret))))
                          (s     (plist-get entry :secret)))
                     (when s (if (functionp s) (funcall s) s))))))
    (unless (and user pass)
      (error "naviel: no credentials for %s — set naviel-username/naviel-password or use ~/.authinfo"
             host))
    (cons user pass)))

(defun naviel--auth-params ()
  "Return alist of Subsonic token-auth query parameters."
  (let* ((creds (naviel--credentials))
         (salt  (naviel--random-salt 10))
         (token (md5 (concat (cdr creds) salt))))
    `(("u" . ,(car creds))
      ("t" . ,token)
      ("s" . ,salt)
      ("v" . ,naviel-api-version)
      ("c" . ,naviel-client-name)
      ("f" . "xml"))))

(defun naviel--random-salt (len)
  (let ((chars "abcdefghijklmnopqrstuvwxyz0123456789") (r ""))
    (dotimes (_ len r)
      (setq r (concat r (string (aref chars (random (length chars)))))))))

;;; Async HTTP / API 
;;
;; Every API call is non-blocking.  CALLBACK is called with the parsed
;; result on success, or nil on any error (an in-buffer message is shown).

(defun naviel--build-url (endpoint params)
  (let* ((all (append (naviel--auth-params) params))
         (q (mapconcat
             (lambda (p) (concat (url-hexify-string (car p)) "=" (url-hexify-string (cdr p))))
             all "&")))
    (format "%s/rest/%s?%s" naviel-url endpoint q)))

(defun naviel--request-async (endpoint params parse-fn callback)
  "GET ENDPOINT asynchronously.  Call (CALLBACK (PARSE-FN xml)) on success."
  (let ((url (naviel--build-url endpoint params)))
    (url-retrieve
     url
     (lambda (status)
       (if (plist-get status :error)
           (progn
             (ignore-errors (kill-buffer (current-buffer)))
             (naviel--show-error
              (format "Could not reach %s — is the server running?" naviel-url))
             (funcall callback nil))
         (condition-case err
             (progn
               (goto-char (point-min))
               (re-search-forward "\r?\n\r?\n" nil t)
               (let* ((xml      (xml-parse-region (point) (point-max)))
                      (response (naviel--check-status xml))
                      (result   (funcall parse-fn response)))
                 (kill-buffer (current-buffer))
                 (funcall callback result)))
           (error
            (ignore-errors (kill-buffer (current-buffer)))
            (naviel--show-error (error-message-string err))
            (funcall callback nil)))))
     nil t)))

(defun naviel--check-status (xml)
  (let* ((root     (car xml))
         (response (if (eq (xml-node-name root) 'subsonic-response) root
                     (car (xml-get-children root 'subsonic-response))))
         (status   (xml-get-attribute-or-nil response 'status)))
    (unless response (error "naviel: unexpected XML response structure"))
    (when (string= status "failed")
      (let* ((err  (car (xml-get-children response 'error)))
             (code (xml-get-attribute err 'code))
             (msg  (xml-get-attribute err 'message)))
        (error "naviel API error %s: %s" code msg)))
    response))

(defun naviel--get-child (r tag) (car (xml-get-children r tag)))
(defun naviel--attr (node attr)  (xml-get-attribute node attr))

;;; Error display

(defun naviel--show-error (msg)
  "Display MSG as a friendly in-buffer error (no raw Lisp tracebacks)."
  (with-current-buffer (naviel--browser-buffer)
    (naviel-browser-mode)
    (let ((inhibit-read-only t))
      (erase-buffer)
      (insert (propertize "\n  ✗  naviel error\n\n" 'face 'naviel-error-face))
      (insert (propertize (format "  %s\n\n" msg)   'face 'naviel-error-face))
      (insert (propertize "  Press g to retry, q to quit.\n" 'face 'naviel-footer-face))
      (goto-char (point-min))))
  (pop-to-buffer (naviel--browser-buffer)))

;;; Stream URL

(defun naviel--stream-url (song-id)
  (naviel--build-url "stream" `(("id" . ,song-id))))

;;; mpv IPC
;;
;; naviel--ipc-process is a Unix socket client kept alive for the
;; lifetime of a track.  Its filter accumulates newline-delimited JSON
;; from mpv and dispatches each complete line to naviel--ipc-dispatch.
;;
;; Outgoing commands use naviel--ipc-send, which optionally registers a
;; one-shot callback keyed by request_id so callers can receive results.
;;
;; mpv also emits unsolicited "event" objects; naviel--ipc-handle-event
;; handles the ones we care about (end-file, pause, unpause).

(defun naviel--ipc-socket-path ()
  (expand-file-name "naviel-mpv.sock" temporary-file-directory))

(defun naviel--ipc-connect ()
  "Open a persistent connection to the mpv IPC socket."
  (let ((sock  (naviel--ipc-socket-path))
        (limit (+ (float-time) 1.5)))
    (while (and (not (file-exists-p sock)) (< (float-time) limit))
      (sleep-for 0.05))
    (when (file-exists-p sock)
      (condition-case err
          (setq naviel--ipc-process
                (make-network-process
                 :name     "naviel-ipc"
                 :family   'local
                 :service  sock
                 :filter   #'naviel--ipc-filter
                 :sentinel #'naviel--ipc-sentinel
                 :coding   'utf-8-unix)
                naviel--ipc-buffer "")
        (error (message "naviel: IPC connect failed — %s" (error-message-string err)))))))

(defun naviel--ipc-filter (_proc string)
  "Accumulate STRING and dispatch complete JSON lines."
  (setq naviel--ipc-buffer (concat naviel--ipc-buffer string))
  (let ((start 0))
    (while (string-match "\n" naviel--ipc-buffer start)
      (let* ((end  (match-end 0))
             (line (substring naviel--ipc-buffer start (1- end))))
        (setq start end)
        (naviel--ipc-dispatch line)))
    (setq naviel--ipc-buffer (substring naviel--ipc-buffer start))))

(defun naviel--ipc-sentinel (proc event)
  (when (and (string-match-p "deleted\\|closed\\|failed" event)
             (eq proc naviel--ipc-process))
    (setq naviel--ipc-process nil)))

(defun naviel--ipc-dispatch (json-line)
  "Parse one JSON LINE from mpv and act on it."
  (condition-case nil
      (let* ((obj    (json-read-from-string json-line))
             (event  (cdr (assq 'event      obj)))
             (req-id (cdr (assq 'request_id obj)))
             (data   (cdr (assq 'data       obj)))
             (err    (cdr (assq 'error      obj))))
        ;; One-shot request callbacks.
        (when req-id
          (let ((cb (cdr (assq req-id naviel--ipc-callbacks))))
            (when cb
              (setq naviel--ipc-callbacks (assq-delete-all req-id naviel--ipc-callbacks))
              (when (or (null err) (string= err "success"))
                (funcall cb data)))))
        ;; Unsolicited events.
        (when event (naviel--ipc-handle-event event)))
    (error nil)))

(defun naviel--ipc-handle-event (event)
  "Dispatch mpv EVENT string to the appropriate handler."
  (cond
   ((string= event "end-file") (naviel--next-in-queue))
   ((string= event "pause")    (setq naviel--paused t)   (naviel--refresh-footer))
   ((string= event "unpause")  (setq naviel--paused nil)  (naviel--refresh-footer))))

(defun naviel--ipc-send (command &optional callback)
  "Send COMMAND list to mpv IPC.  Call CALLBACK with the data field if provided."
  (when (and naviel--ipc-process (process-live-p naviel--ipc-process))
    (cl-incf naviel--ipc-request-id)
    (let* ((id  naviel--ipc-request-id)
           (msg (append `(("command" . ,(vconcat command)))
                        (when callback `(("request_id" . ,id)))))
           (json (concat (json-encode msg) "\n")))
      (when callback (push (cons id callback) naviel--ipc-callbacks))
      (condition-case err
          (process-send-string naviel--ipc-process json)
        (error (message "naviel IPC send: %s" (error-message-string err)))))))

;;; Playback position polling

(defun naviel--start-position-timer ()
  (naviel--stop-position-timer)
  (setq naviel--position-timer
        (run-with-timer naviel-position-poll-interval
                        naviel-position-poll-interval
                        #'naviel--poll-position)))

(defun naviel--stop-position-timer ()
  (when naviel--position-timer
    (cancel-timer naviel--position-timer)
    (setq naviel--position-timer nil)))

(defun naviel--poll-position ()
  "Ask mpv for time-pos and duration; update state and refresh footer."
  (when (and naviel--ipc-process (process-live-p naviel--ipc-process))
    (naviel--ipc-send '("get_property" "time-pos")
                      (lambda (v) (setq naviel--elapsed  (and (numberp v) v))
                                  (naviel--refresh-footer)))
    (naviel--ipc-send '("get_property" "duration")
                      (lambda (v) (setq naviel--duration (and (numberp v) v))))))

;;; mpv process management 

(defun naviel--stop ()
  "Stop playback and tear down all mpv-related state."
  (naviel--stop-position-timer)
  (when (and naviel--ipc-process (process-live-p naviel--ipc-process))
    (delete-process naviel--ipc-process))
  (setq naviel--ipc-process nil naviel--ipc-buffer "")
  (when (and naviel--process (process-live-p naviel--process))
    (delete-process naviel--process))
  (let ((sock (naviel--ipc-socket-path)))
    (when (file-exists-p sock) (ignore-errors (delete-file sock))))
  (setq naviel--process     nil
        naviel--paused       nil
        naviel--current-song nil
        naviel--elapsed      nil
        naviel--duration     nil)
  (naviel--refresh-footer))

(defun naviel--play-url (url song-info)
  "Launch mpv on URL and track SONG-INFO as the current song."
  (naviel--stop)
  (setq naviel--current-song song-info
        naviel--paused  nil
        naviel--elapsed nil
        naviel--duration nil)
  (let* ((sock (naviel--ipc-socket-path))
         (proc (start-process "naviel-mpv" nil
                              naviel-mpv-executable
                              "--no-video" "--quiet"
                              (format "--volume=%d"            naviel--volume)
                              (format "--input-ipc-server=%s"  sock)
                              url)))
    (setq naviel--process proc))
  ;; Connect IPC after a brief delay for mpv to initialise.
  (run-with-timer 0.3 nil #'naviel--ipc-connect)
  (run-with-timer 0.6 nil #'naviel--start-position-timer)
  (naviel--refresh-footer)
  (message "♪  %s — %s"
           (plist-get song-info :title)
           (plist-get song-info :artist)))

(defun naviel--toggle-pause ()
  "Toggle pause/resume via IPC — no restart."
  (interactive)
  (if (and naviel--process (process-live-p naviel--process))
      (naviel--ipc-send '("cycle" "pause"))
    (message "naviel: nothing is playing")))

(defun naviel--seek (seconds)
  "Seek SECONDS relative to the current position."
  (if (and naviel--process (process-live-p naviel--process))
      (naviel--ipc-send `("seek" ,seconds "relative"))
    (message "naviel: nothing is playing")))

(defun naviel-seek-forward  () "Seek forward."  (interactive) (naviel--seek    naviel-seek-step))
(defun naviel-seek-backward () "Seek backward." (interactive) (naviel--seek (- naviel-seek-step)))

;;; Queue management

(defun naviel--play-queue-index (idx)
  (setq naviel--queue-index idx)
  (let* ((song (nth idx naviel--queue))
         (url  (naviel--stream-url (plist-get song :id))))
    (naviel--play-url url song)
    (naviel--rerender-current-view)))

(defun naviel--next-in-queue ()
  "Advance to the next track, obeying repeat mode."
  (interactive)
  (pcase naviel-repeat-mode
    ('one   (naviel--play-queue-index naviel--queue-index))
    ('album (naviel--play-queue-index
             (mod (1+ naviel--queue-index) (max 1 (length naviel--queue)))))
    (_      (let ((next (1+ naviel--queue-index)))
              (if (< next (length naviel--queue))
                  (naviel--play-queue-index next)
                (naviel--stop)
                (message "naviel: end of queue"))))))

(defun naviel--prev-in-queue ()
  (interactive)
  (let ((prev (1- naviel--queue-index)))
    (if (>= prev 0) (naviel--play-queue-index prev)
      (message "naviel: at start of queue"))))

(defun naviel--volume-up ()
  (interactive)
  (setq naviel--volume (min 100 (+ naviel--volume naviel-volume-step)))
  (naviel--ipc-send `("set_property" "volume" ,naviel--volume))
  (naviel--refresh-footer)
  (message "Volume: %d%%" naviel--volume))

(defun naviel--volume-down ()
  (interactive)
  (setq naviel--volume (max 0 (- naviel--volume naviel-volume-step)))
  (naviel--ipc-send `("set_property" "volume" ,naviel--volume))
  (naviel--refresh-footer)
  (message "Volume: %d%%" naviel--volume))

;;; API parse helpers 

(defun naviel--parse-artists (response)
  (let (result)
    (dolist (index (xml-get-children (naviel--get-child response 'artists) 'index) result)
      (dolist (a (xml-get-children index 'artist))
        (push `(:id ,(naviel--attr a 'id) :name ,(naviel--attr a 'name)
                :albums ,(naviel--attr a 'albumCount))
              result)))
    (nreverse result)))

(defun naviel--parse-artist-albums (response)
  (let (result)
    (dolist (al (xml-get-children (naviel--get-child response 'artist) 'album) result)
      (push `(:id ,(naviel--attr al 'id) :name ,(naviel--attr al 'name)
               :year ,(naviel--attr al 'year))
            result))
    (nreverse result)))

(defun naviel--parse-album-songs (response)
  (let (result)
    (dolist (s (xml-get-children (naviel--get-child response 'album) 'song) result)
      (push `(:id ,(naviel--attr s 'id) :title ,(naviel--attr s 'title)
               :artist ,(naviel--attr s 'artist) :album ,(naviel--attr s 'album)
               :track ,(naviel--attr s 'track) :duration ,(naviel--attr s 'duration))
            result))
    (nreverse result)))

(defun naviel--parse-search (response)
  (let* ((r3 (naviel--get-child response 'searchResult3))
         artists albums songs)
    (dolist (a  (xml-get-children r3 'artist))
      (push `(:id ,(naviel--attr a 'id) :name ,(naviel--attr a 'name)) artists))
    (dolist (al (xml-get-children r3 'album))
      (push `(:id ,(naviel--attr al 'id) :name ,(naviel--attr al 'name)
               :artist ,(naviel--attr al 'artist)) albums))
    (dolist (s  (xml-get-children r3 'song))
      (push `(:id ,(naviel--attr s 'id) :title ,(naviel--attr s 'title)
               :artist ,(naviel--attr s 'artist) :album ,(naviel--attr s 'album)
               :duration ,(naviel--attr s 'duration)) songs))
    `(:artists ,(nreverse artists) :albums ,(nreverse albums) :songs ,(nreverse songs))))

(defun naviel--parse-random-songs (response)
  (let (result)
    (dolist (s (xml-get-children (naviel--get-child response 'randomSongs) 'song) result)
      (push `(:id ,(naviel--attr s 'id) :title ,(naviel--attr s 'title)
               :artist ,(naviel--attr s 'artist) :album ,(naviel--attr s 'album)
               :duration ,(naviel--attr s 'duration))
            result))
    (nreverse result)))

;;; Async API entry points 

(defun naviel--get-artists       (cb)    (naviel--request-async "getArtists"    '() #'naviel--parse-artists      cb))
(defun naviel--get-artist        (id cb) (naviel--request-async "getArtist"     `(("id" . ,id)) #'naviel--parse-artist-albums cb))
(defun naviel--get-album         (id cb) (naviel--request-async "getAlbum"      `(("id" . ,id)) #'naviel--parse-album-songs   cb))
(defun naviel--search-async      (q  cb) (naviel--request-async "search3"
                                                                 `(("query" . ,q) ("artistCount" . "10")
                                                                   ("albumCount" . "10") ("songCount" . "20"))
                                                                 #'naviel--parse-search cb))
(defun naviel--get-random-songs  (n  cb) (naviel--request-async "getRandomSongs" `(("size" . ,(number-to-string n)))
                                                                 #'naviel--parse-random-songs cb))

;;; Duration / string helpers 

(defun naviel--format-secs (secs)
  "Format SECS (number or nil) as M:SS string."
  (if (and secs (numberp secs) (> secs 0))
      (let* ((s (round secs)) (m (/ s 60)) (ss (% s 60)))
        (format "%d:%02d" m ss))
    "--:--"))

(defun naviel--trunc (s max)
  "Truncate string S to MAX chars, appending … if needed."
  (if (and s (> (length s) max))
      (concat (substring s 0 (- max 1)) "…")
    (or s "")))

;;; Browser buffer

(defun naviel--browser-buffer () (get-buffer-create "*Naviel*"))

(defun naviel--make-breadcrumbs ()
  (if (null naviel--browser-stack) ""
    (propertize
     (concat "  " (mapconcat (lambda (v) (plist-get v :label))
                             (reverse naviel--browser-stack) " › ") "\n")
     'face 'naviel-breadcrumb-face)))

(defun naviel--volume-bar (vol)
  (let* ((w 10) (f (round (* w (/ vol 100.0)))))
    (concat "[" (make-string f ?█) (make-string (- w f) ?░) (format "] %3d%%" vol))))

(defun naviel--now-playing-bar ()
  "Build the persistent footer string."
  (let* ((song  naviel--current-song)
         (elap  (naviel--format-secs naviel--elapsed))
         (dur   (naviel--format-secs
                 (or naviel--duration
                     (when song
                       (let ((d (plist-get song :duration)))
                         (when (and d (not (string= d ""))) (string-to-number d)))))))
         (qlen  (length naviel--queue)))
    (concat
     "\n"
     (propertize (make-string (max 40 (- (window-width) 2)) ?─) 'face 'naviel-separator-face)
     "\n"
     (if song
         (format "  %s%s%s%s\n"
                 (if naviel--paused
                     (propertize "⏸ " 'face 'naviel-paused-face)
                   (propertize "▶ " 'face 'naviel-now-playing-face))
                 (propertize (naviel--trunc (plist-get song :title) 35)  'face 'naviel-now-playing-face)
                 (propertize (concat " — " (naviel--trunc (plist-get song :artist) 25)) 'face 'naviel-song-meta-face)
                 (propertize (format "  %s / %s  [%d/%d]" elap dur (1+ naviel--queue-index) qlen)
                             'face 'naviel-position-face))
       (propertize "  ♪  Nothing playing\n" 'face 'shadow))
     (format "  %s   repeat: %s\n"
             (propertize (format "vol %s" (naviel--volume-bar naviel--volume)) 'face 'naviel-song-meta-face)
             (propertize (naviel--repeat-label) 'face 'naviel-repeat-face))
     (propertize
      "  RET play  SPC pause  n/p skip  [ ] seek  +/- vol  s search  r random  b back  R repeat  ? help"
      'face 'naviel-footer-face)
     "\n")))

(defconst naviel--footer-sep "\0naviel-footer\0"
  "Invisible marker separating body from footer in the browser buffer.")

;;; Core render 

(defun naviel--browser-render (heading items format-fn type &optional section-label)
  "Render the browser buffer and store view state."
  (setq naviel--current-view
        `(:type ,type :items ,items :heading ,heading
          :format-fn ,format-fn :section-label ,section-label))
  (naviel--do-render heading items format-fn type section-label))

(defun naviel--do-render (heading items format-fn type section-label)
  (with-current-buffer (naviel--browser-buffer)
    (naviel-browser-mode)
    (let ((inhibit-read-only t)
          (saved-line (line-number-at-pos)))
      (erase-buffer)
      ;; Header
      (insert (naviel--make-breadcrumbs))
      (insert (propertize (format "  ♪  %s\n" heading) 'face 'naviel-header-face))
      (insert (propertize (make-string (min 72 (window-width)) ?═) 'face 'naviel-separator-face))
      (insert "\n")
      (when section-label
        (insert (propertize (format "\n  %s\n\n" section-label) 'face 'naviel-breadcrumb-face)))
      ;; Body
      (if (null items)
          (insert (propertize "  (no results)\n" 'face 'shadow))
        (let ((idx 0))
          (dolist (item items)
            (let* ((is-playing (and naviel--current-song (eq type 'song)
                                    (= idx naviel--queue-index)
                                    (equal (plist-get item :id)
                                           (plist-get naviel--current-song :id))))
                   (line (funcall format-fn item is-playing)))
              (insert (propertize line
                                  'naviel-item item 'naviel-type type 'naviel-idx idx
                                  'face (when is-playing 'naviel-now-playing-face)))
              (insert "\n"))
            (cl-incf idx))))
      ;; Footer
      (insert (propertize naviel--footer-sep 'invisible t))
      (insert (naviel--now-playing-bar))
      ;; Restore cursor position
      (goto-char (point-min))
      (forward-line (max 0 (- saved-line 1))))))

(defun naviel--rerender-current-view ()
  (when (and naviel--current-view (get-buffer "*Naviel*"))
    (naviel--do-render
     (plist-get naviel--current-view :heading)
     (plist-get naviel--current-view :items)
     (plist-get naviel--current-view :format-fn)
     (plist-get naviel--current-view :type)
     (plist-get naviel--current-view :section-label))))

(defun naviel--refresh-footer ()
  (naviel--rerender-current-view)
  (naviel--update-mode-line))

;;; Format callbacks 

(defun naviel--format-artist (artist _p)
  (format "  %s%s"
          (propertize (naviel--trunc (plist-get artist :name) 52) 'face 'naviel-artist-face)
          (let ((n (plist-get artist :albums)))
            (if (and n (not (string= n "")))
                (propertize (format "  (%s)" n) 'face 'naviel-count-face) ""))))

(defun naviel--format-album (album _p)
  (format "  %s%s"
          (propertize (naviel--trunc (plist-get album :name) 52) 'face 'naviel-album-face)
          (let ((y (plist-get album :year)))
            (if (and y (not (string= y "")))
                (propertize (format "  %s" y) 'face 'naviel-year-face) ""))))

(defun naviel--format-song (song playing)
  (let* ((track  (or (plist-get song :track) ""))
         (title  (naviel--trunc (or (plist-get song :title)  "?") 36))
         (artist (naviel--trunc (or (plist-get song :artist) "")  26))
         (dur    (naviel--format-secs
                  (let ((d (plist-get song :duration)))
                    (when (and d (not (string= d ""))) (string-to-number d))))))
    (format "%s%s  %-36s  %-26s  %s"
            (if playing (propertize "▶ " 'face 'naviel-now-playing-face) "  ")
            (propertize (format "%3s." track) 'face 'naviel-track-num-face)
            (propertize title  'face (if playing 'naviel-now-playing-face 'naviel-song-title-face))
            (propertize artist 'face 'naviel-song-meta-face)
            (propertize dur    'face 'naviel-song-meta-face))))

;;; Render entry points 

(defun naviel--render-artists (artists)
  (naviel--browser-render (format "Artists  (%d)" (length artists))
                          artists #'naviel--format-artist 'artist))

(defun naviel--render-albums (albums name)
  (naviel--browser-render name albums #'naviel--format-album 'album
                          (format "%d album%s" (length albums)
                                  (if (= 1 (length albums)) "" "s"))))

(defun naviel--render-songs (songs context &optional section)
  (naviel--browser-render context songs #'naviel--format-song 'song
                          (or section (format "%d track%s" (length songs)
                                              (if (= 1 (length songs)) "" "s")))))

;;; Browser mode 

(defvar naviel-browser-mode-map
  (let ((m (make-sparse-keymap)))
    (define-key m (kbd "RET") #'naviel--browser-enter)
    (define-key m (kbd "SPC") #'naviel--toggle-pause)
    (define-key m (kbd "n")   #'naviel--next-in-queue)
    (define-key m (kbd "p")   #'naviel--prev-in-queue)
    (define-key m (kbd "+")   #'naviel--volume-up)
    (define-key m (kbd "=")   #'naviel--volume-up)
    (define-key m (kbd "-")   #'naviel--volume-down)
    (define-key m (kbd "[")   #'naviel-seek-backward)
    (define-key m (kbd "]")   #'naviel-seek-forward)
    (define-key m (kbd "s")   #'naviel-search)
    (define-key m (kbd "r")   #'naviel-play-random)
    (define-key m (kbd "b")   #'naviel--browser-back)
    (define-key m (kbd "g")   #'naviel--browser-refresh)
    (define-key m (kbd "q")   #'naviel--browser-quit)
    (define-key m (kbd "?")   #'naviel-help)
    (define-key m (kbd "R")   #'naviel-toggle-repeat)
    m))

(define-derived-mode naviel-browser-mode special-mode "Naviel"
  "Major mode for browsing and controlling Naviel playback."
  (setq buffer-read-only t)
  (setq-local revert-buffer-function #'naviel--browser-refresh)
  (hl-line-mode 1))

(defun naviel--item-at-point ()
  (let ((type (get-text-property (point) 'naviel-type))
        (item (get-text-property (point) 'naviel-item)))
    (when type (cons type item))))

(defun naviel--browser-enter ()
  "Act on the item at point."
  (interactive)
  (let ((entry (naviel--item-at-point)))
    (unless entry (user-error "No item at point"))
    (let ((type (car entry)) (item (cdr entry)))
      (pcase type
        ('artist
         (let ((id (plist-get item :id)) (name (plist-get item :name)))
           (push `(:type artist :data ,id :label ,name) naviel--browser-stack)
           (message "naviel: loading albums…")
           (naviel--get-artist id
                               (lambda (albums)
                                 (if albums (naviel--render-albums albums name)
                                   (pop naviel--browser-stack))))))
        ('album
         (let ((id (plist-get item :id)) (name (plist-get item :name)))
           (push `(:type album :data ,id :label ,name) naviel--browser-stack)
           (message "naviel: loading tracks…")
           (naviel--get-album id
                              (lambda (songs)
                                (if songs
                                    (progn
                                      (setq naviel--queue songs naviel--queue-index 0)
                                      (naviel--render-songs songs name))
                                  (pop naviel--browser-stack))))))
        ('song
         (naviel--play-queue-index (get-text-property (point) 'naviel-idx)))
        (_ (message "naviel: unknown type: %s" type))))))

(defun naviel--browser-back ()
  "Navigate back one level in the browser."
  (interactive)
  (cond
   ((null naviel--browser-stack) (message "naviel: already at top level"))
   ((= 1 (length naviel--browser-stack))
    (setq naviel--browser-stack '())
    (naviel--show-artists))
   (t
    (pop naviel--browser-stack)
    (let* ((frame (car naviel--browser-stack))
           (id    (plist-get frame :data))
           (name  (plist-get frame :label)))
      (naviel--get-artist id (lambda (albums)
                               (when albums (naviel--render-albums albums name))))))))

(defun naviel--browser-refresh (&rest _)
  "Reload current view from the server."
  (interactive)
  (if (null naviel--browser-stack)
      (naviel--show-artists)
    (let* ((frame (car naviel--browser-stack))
           (type  (plist-get frame :type))
           (id    (plist-get frame :data))
           (name  (plist-get frame :label)))
      (pcase type
        ('artist (naviel--get-artist id (lambda (a) (when a (naviel--render-albums a name)))))
        ('album  (naviel--get-album  id (lambda (s) (when s (naviel--render-songs  s name)))))
        (_       (naviel--show-artists))))))

(defun naviel--browser-quit () (interactive) (quit-window))

(defun naviel--show-artists ()
  (message "naviel: loading library…")
  (naviel--get-artists
   (lambda (artists)
     (when artists
       (setq naviel--browser-stack '())
       (naviel--render-artists artists)))))

;;; Mode line 

(defun naviel--mode-line-string ()
  (if naviel--current-song
      (format " ♪%s %s%s"
              (if naviel--paused "⏸" "▶")
              (naviel--trunc (plist-get naviel--current-song :title) 28)
              (if (and naviel--elapsed naviel--duration)
                  (format " %s/%s"
                          (naviel--format-secs naviel--elapsed)
                          (naviel--format-secs naviel--duration))
                ""))
    ""))

(defun naviel--update-mode-line () (force-mode-line-update t))

;;; Public commands 

;;;###autoload
(defun naviel ()
  "Open the Naviel music browser."
  (interactive)
  (unless (executable-find naviel-mpv-executable)
    (error "naviel: mpv not found on PATH"))
  (pop-to-buffer (naviel--browser-buffer))
  (naviel--show-artists))

;;;###autoload
(defun naviel-search (query)
  "Search Naviel for QUERY, displaying artists, albums, and songs."
  (interactive "sSearch Naviel: ")
  (when (string= query "") (user-error "Search query cannot be empty"))
  (message "naviel: searching for \"%s\"…" query)
  (naviel--search-async
   query
   (lambda (results)
     (when results
       (let ((artists (plist-get results :artists))
             (albums  (plist-get results :albums))
             (songs   (plist-get results :songs)))
         (pop-to-buffer (naviel--browser-buffer))
         (naviel-browser-mode)
         (let ((inhibit-read-only t))
           (erase-buffer)
           (insert (propertize (format "  ♪  Search: %s\n" query) 'face 'naviel-header-face))
           (insert (propertize (make-string (min 72 (window-width)) ?═) 'face 'naviel-separator-face))
           (insert "\n")
           (cl-flet ((section (label items type fmt-fn)
                       (when items
                         (insert (propertize (format "\n  %s\n" label) 'face 'naviel-breadcrumb-face))
                         (let ((idx 0))
                           (dolist (item items)
                             (insert (propertize (funcall fmt-fn item nil)
                                                 'naviel-item item 'naviel-type type 'naviel-idx idx))
                             (insert "\n") (cl-incf idx))))))
             (section "Artists" artists 'artist #'naviel--format-artist)
             (section "Albums"  albums  'album  #'naviel--format-album)
             (when songs
               (insert (propertize "\n  Songs\n" 'face 'naviel-breadcrumb-face))
               (setq naviel--queue songs naviel--queue-index 0)
               (let ((idx 0))
                 (dolist (s songs)
                   (insert (propertize
                            (naviel--format-song
                             s (and naviel--current-song
                                    (equal (plist-get s :id)
                                           (plist-get naviel--current-song :id))))
                            'naviel-item s 'naviel-type 'song 'naviel-idx idx))
                   (insert "\n") (cl-incf idx)))
               (message "naviel: %d song%s in queue" (length songs)
                        (if (= 1 (length songs)) "" "s")))
             (when (and (null artists) (null albums) (null songs))
               (insert (propertize "  No results found.\n" 'face 'shadow))))
           (insert (propertize naviel--footer-sep 'invisible t))
           (insert (naviel--now-playing-bar))
           (goto-char (point-min))
           (forward-line 3)))))))

;;;###autoload
(defun naviel-play-random (&optional count)
  "Play COUNT (default 20) random songs."
  (interactive "P")
  (let ((n (if count (prefix-numeric-value count) 20)))
    (message "naviel: fetching %d random tracks…" n)
    (naviel--get-random-songs
     n
     (lambda (songs)
       (when songs
         (setq naviel--queue songs naviel--queue-index 0)
         (pop-to-buffer (naviel--browser-buffer))
         (naviel--render-songs songs (format "Random — %d tracks" n))
         (naviel--play-queue-index 0))))))

;;;###autoload
(defun naviel-stop ()
  "Stop playback."
  (interactive)
  (naviel--stop)
  (message "naviel: stopped"))

;;;###autoload
(defun naviel-help ()
  "Show naviel keybinding help."
  (interactive)
  (with-help-window "*Naviel Help*"
    (princ "Naviel — Navidrome client for Emacs  (v0.3 / Phase 1)\n")
    (princ (make-string 52 ?─)) (princ "\n\n")
    (princ "Navigation\n")
    (princ "  RET    Play item / expand artist or album\n")
    (princ "  b      Go back one level\n")
    (princ "  g      Refresh current view from server\n")
    (princ "  s      Search library\n")
    (princ "  r      Play random  (C-u r for custom count)\n")
    (princ "  q      Quit browser\n\n")
    (princ "Playback\n")
    (princ "  SPC    Toggle pause / resume\n")
    (princ "  n      Next track\n")
    (princ "  p      Previous track\n")
    (princ "  [      Seek backward (naviel-seek-step seconds)\n")
    (princ "  ]      Seek forward  (naviel-seek-step seconds)\n")
    (princ "  +  =   Volume up\n")
    (princ "  -      Volume down\n")
    (princ "  R      Cycle repeat: off → one → all → off\n\n")
    (princ "Customisation\n")
    (princ "  naviel-seek-step               seconds per seek    (default 10)\n")
    (princ "  naviel-volume-step             % per +/- press     (default 5)\n")
    (princ "  naviel-position-poll-interval  IPC poll rate in s  (default 1.0)\n")))

;;; Mode line integration 
(defvar naviel-mode-line-format '(:eval (naviel--mode-line-string)))

;;;###autoload
(define-minor-mode naviel-mode-line-mode
  "Show Naviel playback status in the mode line."
  :global t :lighter nil
  (if naviel-mode-line-mode
      (progn
        (add-to-list 'global-mode-string naviel-mode-line-format)
        (setq naviel--mode-line-timer (run-with-timer 1 1 #'naviel--update-mode-line)))
    (setq global-mode-string (remove naviel-mode-line-format global-mode-string))
    (when naviel--mode-line-timer
      (cancel-timer naviel--mode-line-timer)
      (setq naviel--mode-line-timer nil))))

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