import argparse
import bz2
import gzip
import json
import io
import os
from datetime import datetime, timedelta
from typing import Any, Callable, List, Optional, Text
from urllib.request import urlopen

try:
    import zstandard
except ImportError:
    zstandard = None

from .utils import git

from . import log


here = os.path.dirname(__file__)

wpt_root = os.path.abspath(os.path.join(here, os.pardir, os.pardir))
logger = log.get_logger()


def abs_path(path: Text) -> Text:
    return os.path.abspath(os.path.expanduser(path))


def should_download(manifest_path: Text, rebuild_time: timedelta = timedelta(days=5)) -> bool:
    if not os.path.exists(manifest_path):
        return True
    mtime = datetime.fromtimestamp(os.path.getmtime(manifest_path))
    if mtime < datetime.now() - rebuild_time:
        return True
    logger.info("Skipping manifest download because existing file is recent")
    return False


def merge_pr_tags(repo_root: Text, max_count: int = 50) -> List[Text]:
    gitfunc = git(repo_root)
    tags: List[Text] = []
    if gitfunc is None:
        return tags
    for line in gitfunc("log", "--format=%D", "--max-count=%s" % max_count).split("\n"):
        for ref in line.split(", "):
            if ref.startswith("tag: merge_pr_"):
                tags.append(ref[5:])
    return tags


def score_name(name: Text) -> Optional[int]:
    """Score how much we like each filename, lower wins, None rejects"""

    # Accept both ways of naming the manifest asset, even though
    # there's no longer a reason to include the commit sha.
    if name.startswith("MANIFEST-") or name.startswith("MANIFEST."):
        if zstandard and name.endswith("json.zst"):
            return 1
        if name.endswith(".json.bz2"):
            return 2
        if name.endswith(".json.gz"):
            return 3
    return None


def github_url(tags: List[Text]) -> Optional[List[Text]]:
    for tag in tags:
        url = "https://api.github.com/repos/web-platform-tests/wpt/releases/tags/%s" % tag
        try:
            resp = urlopen(url)
        except Exception:
            logger.warning("Fetching %s failed" % url)
            continue

        if resp.code != 200:
            logger.warning("Fetching %s failed; got HTTP status %d" % (url, resp.code))
            continue

        try:
            release = json.load(resp.fp)
        except ValueError:
            logger.warning("Response was not valid JSON")
            return None

        candidates = []
        for item in release["assets"]:
            score = score_name(item["name"])
            if score is not None:
                candidates.append((score, item["browser_download_url"]))

        return [item[1] for item in sorted(candidates)]

    return None


def download_manifest(
        manifest_path: Text,
        tags_func: Callable[[], List[Text]],
        url_func: Callable[[List[Text]], Optional[List[Text]]],
        force: bool = False
) -> bool:
    if not force and not should_download(manifest_path):
        return False

    tags = tags_func()

    urls = url_func(tags)
    if not urls:
        logger.warning("No generated manifest found")
        return False

    for url in urls:
        logger.info("Downloading manifest from %s" % url)
        try:
            resp = urlopen(url)
        except Exception:
            logger.warning("Downloading pregenerated manifest failed")
            continue

        if resp.code != 200:
            logger.warning("Downloading pregenerated manifest failed; got HTTP status %d" %
                           resp.code)
            continue

        if url.endswith(".zst"):
            if not zstandard:
                continue
            try:
                dctx = zstandard.ZstdDecompressor()
                decompressed = dctx.decompress(resp.read())
            except OSError:
                logger.warning("Failed to decompress downloaded file")
                continue
        elif url.endswith(".bz2"):
            try:
                decompressed = bz2.decompress(resp.read())
            except OSError:
                logger.warning("Failed to decompress downloaded file")
                continue
        elif url.endswith(".gz"):
            fileobj = io.BytesIO(resp.read())
            try:
                with gzip.GzipFile(fileobj=fileobj) as gzf:
                    data = gzf.read()
                    decompressed = data
            except OSError:
                logger.warning("Failed to decompress downloaded file")
                continue
        else:
            logger.warning("Unknown file extension: %s" % url)
            continue
        break
    else:
        return False

    try:
        with open(manifest_path, "wb") as f:
            f.write(decompressed)
    except Exception:
        logger.warning("Failed to write manifest")
        return False
    logger.info("Manifest downloaded")
    return True


def create_parser() -> argparse.ArgumentParser:
    parser = argparse.ArgumentParser()
    parser.add_argument(
        "-p", "--path", type=abs_path, help="Path to manifest file.")
    parser.add_argument(
        "--tests-root", type=abs_path, default=wpt_root, help="Path to root of tests.")
    parser.add_argument(
        "--force", action="store_true",
        help="Always download, even if the existing manifest is recent")
    return parser


def download_from_github(path: Text, tests_root: Text, force: bool = False) -> bool:
    return download_manifest(path, lambda: merge_pr_tags(tests_root), github_url,
                             force=force)


def run(**kwargs: Any) -> int:
    if kwargs["path"] is None:
        path = os.path.join(kwargs["tests_root"], "MANIFEST.json")
    else:
        path = kwargs["path"]
    success = download_from_github(path, kwargs["tests_root"], kwargs["force"])
    return 0 if success else 1