extends Node
## Client for the MusicServer REST API ([code]/api/v1[/code]).
##
## Registered as the [code]MusicServerClient[/code] autoload, so every script can call it
## directly, e.g. [code]MusicServerClient.fetch_song_list(on_done)[/code]. All HTTP traffic
## goes through [member transport]; tests replace it with a fake to answer requests
## without a running server.
##
## Requests need a token, which the client gets with [code]Settings.api_password[/code]
## the first time it is needed and then reuses. When the server answers 401 (the token
## expired, or the server restarted), it gets a new token and sends the request once
## more. Callers never see the token.
##
## JSON objects are handed to [code]on_done[/code] as the classes generated from the
## server's OpenAPI spec (see [code]server/generated/[/code]), lists of them as typed
## Arrays. [code]on_failed[/code] is called with no arguments when a request fails,
## including when no token could be had.

## Path of the API on the server, added between [code]Settings.default_path[/code] and
## each endpoint.
const API_PATH: String = "/api/v1"
## Sent when asking for a token, so the server can tell its clients apart.
const CLIENT_TYPE: String = "godot"

## Sends the actual HTTP requests. Swap it out in tests.
var transport: HttpTransport

var _token: String = ""
# The server the token is for; switching server in the settings needs a new token
var _token_server: String = ""
# [on_token, on_failed] pairs waiting for the token request that is under way
var _token_waiters: Array[Array] = []


func _ready() -> void:
	if transport == null:
		transport = HttpTransport.new(self)


# Queue

## Fetches the songs already in the server playlist as an [code]Array[SongInfo][/code].
func fetch_song_list(on_done: Callable, on_failed: Callable = Callable()) -> void:
	get_json_list("/music/list", SongInfo, on_done, on_failed)


## Downloads a random song as MP3 bytes. With [param low_played] the server prefers
## soundtracks that have been played the least.
func fetch_random_song(
		low_played: bool, on_done: Callable, on_failed: Callable = Callable()) -> void:
	get_bytes("/music/rand/low" if low_played else "/music/rand", on_done, on_failed)


## Downloads a random song as MP3 bytes, picked the way the server did before low played
## mode existed: any soundtrack is as likely as any other.
func fetch_random_song_classic(on_done: Callable, on_failed: Callable = Callable()) -> void:
	get_bytes("/music/rand/classic", on_done, on_failed)


## Adds the most recently fetched random song to the server playlist.
func add_to_queue(on_done: Callable, on_failed: Callable = Callable()) -> void:
	send("/music/addQue", on_done, on_failed)


## Fetches the [SongInfo] of the most recently queued song.
func fetch_song_info(on_done: Callable, on_failed: Callable = Callable()) -> void:
	get_json_object("/music/info", SongInfo, on_done, on_failed)


## Downloads a song from the server playlist as MP3 bytes.
func fetch_song(song_no: int, on_done: Callable, on_failed: Callable = Callable()) -> void:
	get_bytes("/music?song=" + str(song_no), on_done, on_failed)


## Downloads the song after the current one in the server playlist as MP3 bytes.
func fetch_next_song(on_done: Callable, on_failed: Callable = Callable()) -> void:
	get_bytes("/music/next", on_done, on_failed)


## Downloads the song before the current one in the server playlist as MP3 bytes.
func fetch_previous_song(on_done: Callable, on_failed: Callable = Callable()) -> void:
	get_bytes("/music/previous", on_done, on_failed)


## Downloads the sound test song as MP3 bytes.
func fetch_sound_test_song(on_done: Callable, on_failed: Callable = Callable()) -> void:
	get_bytes("/music/soundTest", on_done, on_failed)


## Clears the server playlist.
func reset_playlist(on_done: Callable, on_failed: Callable = Callable()) -> void:
	send("/music/reset", on_done, on_failed)


## Records in the server statistics that a song has been played.
func mark_song_played(song_no: int) -> void:
	send("/music/played?song=" + str(song_no), Callable(), Callable(), HTTPClient.METHOD_PUT)


## Records in the server statistics that the current song has been played.
func mark_current_song_played(on_done: Callable, on_failed: Callable = Callable()) -> void:
	send("/music/addPlayed", on_done, on_failed)


# Soundtracks and songs

## Fetches every soundtrack name, shuffled, as an Array of Strings.
func fetch_all_soundtracks(on_done: Callable, on_failed: Callable = Callable()) -> void:
	get_json("/music/all", on_done, on_failed)


## Fetches every soundtrack name, sorted, as an Array of Strings.
func fetch_all_soundtracks_ordered(on_done: Callable, on_failed: Callable = Callable()) -> void:
	get_json("/music/all/order", on_done, on_failed)


## Fetches every soundtrack as an [code]Array[Soundtrack][/code].
func fetch_soundtracks(on_done: Callable, on_failed: Callable = Callable()) -> void:
	get_json_list("/soundtracks", Soundtrack, on_done, on_failed)


## Fetches a soundtrack and its songs as a [SoundtrackWithSongList].
func fetch_soundtrack(
		uuid: String, on_done: Callable, on_failed: Callable = Callable()) -> void:
	get_json_object("/soundtracks/" + uuid.uri_encode(), SoundtrackWithSongList, on_done,
			on_failed)


## Fetches a song as a [Song].
func fetch_song_by_uuid(
		uuid: String, on_done: Callable, on_failed: Callable = Callable()) -> void:
	get_json_object("/songs/" + uuid.uri_encode(), Song, on_done, on_failed)


## Downloads a song by its UUID as MP3 bytes.
func fetch_song_file(uuid: String, on_done: Callable, on_failed: Callable = Callable()) -> void:
	get_bytes("/songs/%s/file" % uuid.uri_encode(), on_done, on_failed)


# Statistics

## Fetches the play statistics of the whole library as a [StatisticsSummary].
func fetch_statistics_summary(on_done: Callable, on_failed: Callable = Callable()) -> void:
	get_json_object("/statistics/summary", StatisticsSummary, on_done, on_failed)


## Fetches the [param limit] most played soundtracks as an
## [code]Array[SoundtrackWithSongs][/code]. The server allows a limit of 1 to 100.
func fetch_most_played_soundtracks(
		limit: int, on_done: Callable, on_failed: Callable = Callable()) -> void:
	_fetch_soundtrack_statistics("most-played", limit, on_done, on_failed)


## Fetches the [param limit] least played soundtracks as an
## [code]Array[SoundtrackWithSongs][/code].
func fetch_least_played_soundtracks(
		limit: int, on_done: Callable, on_failed: Callable = Callable()) -> void:
	_fetch_soundtrack_statistics("least-played", limit, on_done, on_failed)


## Fetches the [param limit] most recently played soundtracks as an
## [code]Array[SoundtrackWithSongs][/code].
func fetch_last_played_soundtracks(
		limit: int, on_done: Callable, on_failed: Callable = Callable()) -> void:
	_fetch_soundtrack_statistics("last-played", limit, on_done, on_failed)


## Fetches the [param limit] soundtracks that were played longest ago, leaving out those
## never played, as an [code]Array[SoundtrackWithSongs][/code].
func fetch_oldest_played_soundtracks(
		limit: int, on_done: Callable, on_failed: Callable = Callable()) -> void:
	_fetch_soundtrack_statistics("oldest-played", limit, on_done, on_failed)


## Fetches every soundtrack that has never been played as an
## [code]Array[SoundtrackWithSongs][/code].
func fetch_never_played_soundtracks(
		on_done: Callable, on_failed: Callable = Callable()) -> void:
	get_json_list("/statistics/soundtracks/never-played", SoundtrackWithSongs, on_done,
			on_failed)


## Fetches the [param limit] most played songs as an
## [code]Array[SongInfoForStats][/code].
func fetch_most_played_songs(
		limit: int, on_done: Callable, on_failed: Callable = Callable()) -> void:
	get_json_list("/statistics/songs/most-played?limit=%d" % limit, SongInfoForStats,
			on_done, on_failed)


## Fetches the [param limit] least played songs as an
## [code]Array[SongInfoForStats][/code].
func fetch_least_played_songs(
		limit: int, on_done: Callable, on_failed: Callable = Callable()) -> void:
	get_json_list("/statistics/songs/least-played?limit=%d" % limit, SongInfoForStats,
			on_done, on_failed)


# Characters

## Fetches the names of all character images.
func fetch_character_list(on_done: Callable, on_failed: Callable = Callable()) -> void:
	get_json("/character/list", on_done, on_failed)


## Downloads a character image as PNG bytes.
func fetch_character_image(
		character_name: String, on_done: Callable, on_failed: Callable = Callable()) -> void:
	get_bytes("/character?name=" + character_name.uri_encode(), on_done, on_failed)


# Sync

## Starts syncing the server's soundtrack library with its music folder, looking only
## at what changed. The server answers 423 if a sync is already running.
func start_sync(on_done: Callable, on_failed: Callable = Callable()) -> void:
	send("/sync", on_done, on_failed, HTTPClient.METHOD_POST)


## Starts syncing every soundtrack again, changed or not.
func start_full_sync(on_done: Callable, on_failed: Callable = Callable()) -> void:
	send("/sync/full", on_done, on_failed, HTTPClient.METHOD_POST)


## Fetches the sync state: [code]{progress, time_spent}[/code] while running, or the
## sync result once finished.
func fetch_sync_progress(on_done: Callable, on_failed: Callable = Callable()) -> void:
	get_json("/sync/progress", on_done, on_failed)


# Server

## Checks that the server is up, without a token. Calls [param on_done] with its status
## Dictionary.
func fetch_health(on_done: Callable, on_failed: Callable = Callable()) -> void:
	_send_once("/health", HTTPClient.METHOD_GET, "",
			_parse_json.bind("/health", on_done, on_failed), on_failed)


## Fetches the server version and its changes as a [VersionData].
func fetch_version(on_done: Callable, on_failed: Callable = Callable()) -> void:
	get_json_object("/version", VersionData, on_done, on_failed)


## Fetches every server version as an [code]Array[VersionData][/code].
func fetch_version_history(on_done: Callable, on_failed: Callable = Callable()) -> void:
	get_json_list("/version/history", VersionData, on_done, on_failed)


# Game downloads

## Fetches the name of the newest MusicPlayer release.
func fetch_latest_client_version(on_done: Callable, on_failed: Callable = Callable()) -> void:
	get_json("/download", on_done, on_failed)


## Fetches the file names in the newest MusicPlayer release.
func fetch_client_assets(on_done: Callable, on_failed: Callable = Callable()) -> void:
	get_json("/download/list", on_done, on_failed)


## Downloads the newest MusicPlayer for Windows.
func download_client_windows(on_done: Callable, on_failed: Callable = Callable()) -> void:
	get_bytes("/download/windows", on_done, on_failed)


## Downloads the newest MusicPlayer for Linux.
func download_client_linux(on_done: Callable, on_failed: Callable = Callable()) -> void:
	get_bytes("/download/linux", on_done, on_failed)


# Tokens

## Tells the server to forget the token, e.g. when quitting. The next request gets a
## new one.
func delete_token(on_done: Callable = Callable(), on_failed: Callable = Callable()) -> void:
	if _token.is_empty():
		_call_if_valid(on_done)
		return
	var token: String = _token
	clear_token()
	_send_once("/token", HTTPClient.METHOD_DELETE, token, func(_body: PackedByteArray) -> void:
		_call_if_valid(on_done)
	, on_failed)


## Asks the server to remove expired tokens of all clients.
func cleanup_tokens(on_done: Callable, on_failed: Callable = Callable()) -> void:
	send("/token/cleanup", on_done, on_failed, HTTPClient.METHOD_POST)


## Forgets the token without telling the server, so the next request gets a new one.
func clear_token() -> void:
	_token = ""
	_token_server = ""


# Generic requests

## Requests [param path] and calls [param on_done] with the parsed JSON.
## [param on_failed] is called with no arguments if the request fails or the body is
## not valid JSON.
func get_json(path: String, on_done: Callable, on_failed: Callable = Callable()) -> void:
	_request(path, HTTPClient.METHOD_GET, _parse_json.bind(path, on_done, on_failed),
			on_failed)


## Requests [param path], which answers with a JSON object, and calls [param on_done]
## with it read into [param type], one of the generated API classes.
func get_json_object(
		path: String, type: GDScript, on_done: Callable, on_failed: Callable = Callable(),
) -> void:
	get_json(path, func(data: Variant) -> void:
		if !(data is Dictionary):
			push_warning("Expected a JSON object from " + path)
			_call_if_valid(on_failed)
			return
		on_done.call(type.from_dict(data))
	, on_failed)


## Requests [param path], which answers with a JSON array of objects, and calls
## [param on_done] with a typed Array of [param type], one of the generated API classes.
## The server sends [code]null[/code] for an empty list, which gives an empty Array.
func get_json_list(
		path: String, type: GDScript, on_done: Callable, on_failed: Callable = Callable(),
) -> void:
	get_json(path, func(data: Variant) -> void:
		if data == null:
			data = []
		if !(data is Array):
			push_warning("Expected a JSON array from " + path)
			_call_if_valid(on_failed)
			return
		var items: Array = Array([], TYPE_OBJECT, "RefCounted", type)
		for item: Variant in data:
			if item is Dictionary:
				items.append(type.from_dict(item))
		on_done.call(items)
	, on_failed)


## Requests [param path] and calls [param on_done] with the raw response body, or
## [param on_failed] with no arguments if the request fails.
func get_bytes(path: String, on_done: Callable, on_failed: Callable = Callable()) -> void:
	_request(path, HTTPClient.METHOD_GET, on_done, on_failed)


## Requests [param path] and calls [param on_done] with no arguments when it succeeds,
## or [param on_failed] when it fails. Either may be an empty Callable.
func send(
		path: String,
		on_done: Callable,
		on_failed: Callable = Callable(),
		method: int = HTTPClient.METHOD_GET,
) -> void:
	_request(path, method, func(_body: PackedByteArray) -> void:
		_call_if_valid(on_done)
	, on_failed)


func _fetch_soundtrack_statistics(
		list_name: String, limit: int, on_done: Callable, on_failed: Callable) -> void:
	get_json_list("/statistics/soundtracks/%s?limit=%d" % [list_name, limit],
			SoundtrackWithSongs, on_done, on_failed)


func _parse_json(
		body: PackedByteArray, path: String, on_done: Callable, on_failed: Callable) -> void:
	var json: JSON = JSON.new()
	if json.parse(body.get_string_from_utf8()) != OK:
		push_warning("Invalid JSON from %s: %s" % [path, json.get_error_message()])
		_call_if_valid(on_failed)
		return
	on_done.call(json.data)


# Sends the request with the token, and once more with a new token if the server
# answers 401
func _request(
		path: String,
		method: int,
		on_success: Callable,
		on_failed: Callable,
		may_retry: bool = true,
) -> void:
	_with_token(func(token: String) -> void:
		_send(path, method, token, func(response_code: int, body: PackedByteArray) -> void:
			if response_code == 401 && may_retry:
				GameLog.debug("Token refused by the server, getting a new one")
				if _token == token:
					clear_token()
				_request(path, method, on_success, on_failed, false)
				return
			_handle_response(path, response_code, body, on_success, on_failed)
		)
	, on_failed)


# Sends the request once, with [param token] if it is not empty
func _send_once(
		path: String, method: int, token: String, on_success: Callable, on_failed: Callable,
) -> void:
	_send(path, method, token, func(response_code: int, body: PackedByteArray) -> void:
		_handle_response(path, response_code, body, on_success, on_failed)
	)


func _send(
		path: String, method: int, token: String, on_complete: Callable, body: String = "",
) -> void:
	var headers: PackedStringArray = []
	if !token.is_empty():
		headers.append("Authorization: Bearer " + token)
	transport.request(Settings.default_path + API_PATH + path, method, on_complete, headers,
			body)


func _handle_response(
		path: String,
		response_code: int,
		body: PackedByteArray,
		on_success: Callable,
		on_failed: Callable,
) -> void:
	if response_code != 200:
		push_warning("Request to %s failed with response code %d%s"
				% [path, response_code, _error_message(body)])
		_call_if_valid(on_failed)
		return
	on_success.call(body)


# Calls [param on_token] with the token, asking the server for one first if needed.
# Requests made while asking wait for the same token instead of asking again.
func _with_token(on_token: Callable, on_failed: Callable) -> void:
	if _token_server != Settings.default_path:
		clear_token()
	if !_token.is_empty():
		on_token.call(_token)
		return
	_token_waiters.append([on_token, on_failed])
	if _token_waiters.size() == 1:
		_request_token()


func _request_token() -> void:
	var token_request: TokenRequest = TokenRequest.new()
	token_request.password = Settings.api_password
	token_request.client_type = CLIENT_TYPE
	var server: String = Settings.default_path
	_send("/token", HTTPClient.METHOD_POST, "",
			func(response_code: int, body: PackedByteArray) -> void:
				var waiters: Array[Array] = _token_waiters.duplicate()
				_token_waiters.clear()
				var token: String = _read_token(response_code, body)
				if token.is_empty():
					for waiter: Array in waiters:
						_call_if_valid(waiter[1])
					return
				_token = token
				_token_server = server
				for waiter: Array in waiters:
					waiter[0].call(token)
	, JSON.stringify(token_request.to_dict()))


func _read_token(response_code: int, body: PackedByteArray) -> String:
	if response_code != 200:
		push_warning("Could not get an API token, response code %d%s"
				% [response_code, _error_message(body)])
		return ""
	var data: Variant = _parse_or_null(body)
	var token: String = TokenResponse.from_dict(data).token if data is Dictionary else ""
	if token.is_empty():
		push_warning("The server answered without an API token")
	return token


# The server's {"error": "..."} message, for logging
static func _error_message(body: PackedByteArray) -> String:
	var data: Variant = _parse_or_null(body)
	if data is Dictionary && data.has("error"):
		return ": " + ApiError.from_dict(data).error
	return ""


# Error pages are not always JSON, so failing to parse is not worth a warning here
static func _parse_or_null(body: PackedByteArray) -> Variant:
	var json: JSON = JSON.new()
	return json.data if json.parse(body.get_string_from_utf8()) == OK else null


static func _call_if_valid(callback: Callable) -> void:
	if callback.is_valid():
		callback.call()