#!/usr/bin/env python
#
# Copyright © 2018-2019 Nick Bowler
#
# Tool to fetch album art for a release from the Cover Art Archive.
#
# License WTFPL2: Do What The Fuck You Want To Public License, version 2.
# This is free software: you are free to do what the fuck you want to.
# There is NO WARRANTY, to the extent permitted by law.

from pathlib import Path
import musicbrainzngs
import argparse
import tempfile
import urllib
import sys
import os
import re

umask = os.umask(0)
os.umask(umask)

progname = "caa-fetcher"
version = "1"
musicbrainzngs.set_useragent(progname, version)

parser = argparse.ArgumentParser(
    description='Download album artwork from the Cover Art Archive'
)

def errmsg(msg, prog=parser.prog):
    print("%s: %s" % (prog, msg), file=sys.stderr)

# NamedTemporaryFile workalike which allows control of the file mode...
def open_tmp(prefix="tmp", suffix="", dir=".", mode=0o600):
    names = tempfile._get_candidate_names()
    for seq in range(100):
        name = os.path.join(dir, "%s%s%s" % (prefix, next(names), suffix))
        try:
            f = open(name, "x+", mode)
        except FileExistsError:
            continue
        return tempfile._TemporaryFileWrapper(f, name)
    return None

# Given an arbitrary string, return the first substring that looks like an
# mbid, or None if no such substring is found.
def extract_mbid(arg):
    xdigit = r'[0-9abcdefABCDEF]'
    m = re.search(r'{0}{{8}}(-{0}{{4}}){{3}}-{0}{{12}}'.format(xdigit), arg)
    if m:
        return m.group()

class VersionAction(argparse.Action):
    def __init__(self, **kw):
        super().__init__(nargs=0, help="show a version message and exit", **kw)
    def __call__(self, parser, namespace, values, option_string=None):
        print("%s %s" % (progname, version))
        print('''Copyright © 2019 Nick Bowler
License WTFPL2: Do What The Fuck You Want To Public License, version 2.
This is free software: you are free to do what the fuck you want to.
There is NO WARRANTY, to the extent permitted by law.''')
        sys.exit(0)
parser.add_argument('--version', action=VersionAction)

parser.add_argument('-o', '--output-directory', metavar='DIR',
                    help='''downloaded files are written to DIR, which is
                            created if it does not exists.  Default: .''')
parser.add_argument('-r', '--release-mbid', metavar='MBID', required=True)
args = parser.parse_args()

release_mbid = extract_mbid(args.release_mbid)
if release_mbid is None:
    parser.error("invalid release MBID: %s" % (args.release_mbid))

# TODO: allow the naming scheme to be configured...
name_format = "{num:02d}"

try:
    covers = musicbrainzngs.get_image_list(release_mbid)
except musicbrainzngs.ResponseError as e:
    errmsg("error: cannot retrieve image list for release")
    errmsg(e)
    if isinstance(e.cause, urllib.error.HTTPError) and e.cause.code == 404:
        errmsg("is %s a release MBID?" % (release_mbid))
    sys.exit(1)

if len(covers["images"]) == 0:
    print("release has no cover art, nothing to do")
    sys.exit()

if args.output_directory:
    Path(args.output_directory).mkdir(parents=True, exist_ok=True)
    os.chdir(args.output_directory)

failed = False
for c in covers["images"]:
    (_,ext) = os.path.splitext(c["image"])
    outname = (name_format + "{0}").format(ext,
        num = (covers["images"].index(c) + 1)
    )

    if Path(outname).exists():
        print("%s already exists, skipping..." % outname)
        continue

    outfile = open_tmp(suffix=ext, dir=".", mode=0o666)
    rc = os.spawnlp(os.P_WAIT, 'wget', 'wget', '-O', outfile.name, c["image"])
    if rc:
        failed = True

    os.link(outfile.name, outname)
    outfile.close()

if failed:
    sys.exit(1)