#!/usr/bin/env python3
"""
API for interacting with the Musik database.
"""
import os
import sqlite3
import multiprocessing

import mutagen
import mutagen.mp3

MUSIC_DIR = "/home/iou1name/music/Music"
MUSIC_EXT = ['flac', 'mp3', 'wav', 'm4a']
DB_LOCK = multiprocessing.Lock()

def db_execute(*args, **kwargs):
	"""
	Opens a connection to the app's database and executes the SQL statements
	passed to this function.
	"""
	with sqlite3.connect('musik.db') as con:
		DB_LOCK.acquire()
		con.row_factory = sqlite3.Row
		cur = con.cursor()
		res = cur.execute(*args, **kwargs)
		DB_LOCK.release()
		return res

def db_execute_many(*args, **kwargs):
	"""
	Same as `db_executei()` except with `cur.executemany()`.
	"""
	with sqlite3.connect('musik.db') as con:
		DB_LOCK.acquire()
		con.row_factory = sqlite3.Row
		cur = con.cursor()
		res = cur.executemany(*args, **kwargs)
		DB_LOCK.release()
		return res

def init_database():
	"""
	Initializes the database.
	"""
	try:
		db_execute("SELECT * FROM tracks LIMIT 1").fetchone()
	except sqlite3.OperationalError:
		DB_LOCK.release()
		db_execute("CREATE TABLE tracks("
			"filepath TEXT PRIMARY KEY,"
			"artist TEXT,"
			"albumartist TEXT,"
			"date TEXT,"
			"album TEXT,"
			"discnumber TEXT,"
			"tracknumber TEXT,"
			"title TEXT,"
			"genre TEXT,"
			"length TEXT,"
			"last_modified INTEGER"
			")"
		)
		build_library(MUSIC_DIR)


def build_library(root_dir):
	"""Walks the music directory and builds a library of tracks."""
	print("Building library")
	filepaths = []
	for dir_name, sub_dirs, files in os.walk(root_dir):
		for file in files:
			if not os.path.splitext(file)[1][1:] in MUSIC_EXT:
				continue
			filepath = os.path.join(root_dir, dir_name, file)
			last_modified = os.path.getmtime(filepath)
			filepaths.append((filepath, last_modified))
	tracks_prev = db_execute("SELECT * FROM tracks")
	tracks_prev = {track['filepath']: track for track in tracks_prev}

	global worker
	def worker(tup):
		"""Worker for multi-processing tracks."""
		filepath, last_modified = tup
		track_prev = tracks_prev.get(filepath)
		if track_prev:
			if track_prev['last_modified'] >= last_modified:
				return tuple(track_prev)
		data = read_track(filepath)
		return data

	with multiprocessing.Pool() as pool:
		mapping = pool.imap(worker, filepaths)
		tracks = []
		prev_percent = 0
		while True:
			try:
				tracks.append(mapping.next())
			except StopIteration:
				break
			percent = round(len(tracks) / len(filepaths) * 100, 2)
			if percent >= prev_percent + 2.5:
				print(f"{percent}%")
				prev_percent = percent
	db_execute("DELETE FROM tracks")
	db_execute_many(
		"INSERT INTO tracks VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)",
		tracks
	)
	print("Done")


def read_track(filepath):
	"""
	Reads the specified file and extracts relevant information from it.
	Returns a tuple.
	"""
	if filepath.endswith("mp3"):
		m = mutagen.mp3.EasyMP3(filepath)
	else:
		m = mutagen.File(filepath)
	artist = m.get('artist', [''])[0]
	if m.get('albumartist'):
		albumartist = m.get('albumartist', [''])[0]
	else:
		albumartist = m.get('artist', [''])[0]
	date = m.get('date', [''])[0]
	album = m.get('album', [''])[0]
	discnumber = m.get('discnumber', [''])[0]
	tracknumber = m.get('tracknumber', [''])[0]
	title = m.get('title', [''])[0]
	genre = m.get('genre', [''])[0]
	length = str(int(m.info.length) // 60) + ":"
	length += str(int(m.info.length) % 60)
	last_modified = os.path.getmtime(filepath)

	d = locals()
	d.pop('m')
	return tuple(d.values())


def get_artist_albums(artist):
	"""
	Returns a list of all albums produced by the specified `artist`.
	"""
	albums = db_execute(
		"SELECT DISTINCT album FROM tracks WHERE albumartist = ? ORDER BY date ASC",
		(artist,)
	).fetchall()
	albums = [row[0] for row in albums]
	return albums

def get_album_tracks(artist, album):
	"""
	Returns a list of all tracks on the `album` produced by `artist`.
	"""
	tracks = db_execute(
		"SELECT discnumber, tracknumber, title FROM tracks "
		"WHERE albumartist = ? AND album = ?"
		"ORDER BY discnumber ASC, tracknumber ASC",
		(artist, album)
	).fetchall()
	tracks = [tuple(row) for row in tracks]
	return tracks

def get_track(artist, album, discnumber, tracknumber):
	"""
	Returns a dictionary containing all information about a specific track.
	"""
	track = db_execute(
		"SELECT * FROM tracks "
		"WHERE albumartist = ? AND album = ? "
		"AND discnumber = ? AND tracknumber = ?",
		(artist, album, discnumber, tracknumber)
	).fetchone()
	return dict(track)

def get_random_track():
	"""
	Returns a random track.
	"""
	track = db_execute(
		"SELECT * FROM tracks ORDER BY random() LIMIT 1"
	).fetchone()
	return dict(track)

def get_all_artists():
	"""
	Returns a list of all artist names.
	"""
	artists = db_execute(
		"SELECT DISTINCT albumartist FROM tracks ORDER BY albumartist ASC"
	)
	artists = [row[0] for row in artists]
	return artists