#!/usr/bin/env python3
"""
Database operations for Scorch.
"""
import os
import multiprocessing
from datetime import datetime, timezone

import asyncpg
import mutagen
import mutagen.mp3

import config

MUSIC_EXT = ['flac', 'mp3']

async 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 = datetime.fromtimestamp(
				os.path.getmtime(filepath), timezone.utc)
			filepaths.append((filepath, last_modified))
	db_pool = await asyncpg.create_pool(**config.db)
	async with db_pool.acquire() as conn:
		tracks_prev = await conn.fetch("SELECT * FROM track")
	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
	async with db_pool.acquire() as conn:
		await conn.execute("DELETE FROM track")
		await conn.executemany(
			"INSERT INTO track VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11)",
			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 = m.info.length
	last_modified = datetime.fromtimestamp(
		os.path.getmtime(filepath), timezone.utc)

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