#!/usr/bin/env python3
"""
This script is meant to be run by GitHub Actions.
It comes with a Github Action updater.yml to run this script periodically.

Since each app is different, maintainers can adapt its contents to perform
automatic actions when a new upstream release is detected.

You need to enable the action by removing `if ${{ false }}` in updater.yml!
"""

import hashlib
import json
import tomlkit
import logging
import os
import re
from pathlib import Path
from subprocess import run, PIPE
import textwrap
from typing import List, Tuple, Any
import requests
from packaging import version

logging.getLogger().setLevel(logging.INFO)

# ========================================================================== #
# Functions customizable by app maintainer

def get_latest_version(repo: str) -> Tuple[version.Version, Any]:
    """May be customized by maintainers for other forges than Github"""
    api_url = repo.replace("github.com", "api.github.com/repos")
    # May use {api_url}/tags and release["name"] for tag-based upstream
    releases = requests.get(f"{api_url}/releases").json()
    release_info = next(release for release in releases if not release["prerelease"])
    return version.Version(release_info["tag_name"]), release_info

def get_asset_urls_of_release(repo: str, release: Any) -> List[str]:
    """May be customized by maintainers for custom urls"""
    return [
        *[asset["browser_download_url"] for asset in release["assets"]],
        f"{repo}/archive/refs/tags/{release['tag_name']}.tar.gz"
    ]

def handle_asset(asset_url: str):
    """This should be customized by the maintainer according to upstream"""
    logging.info("Handling asset at %s", asset_url)
    if re.match(r".*/cinny-v[0-9\.]+.(tar.gz)$", asset_url):
        write_src_file("app.src", asset_url, "tar.gz")
    else:
        logging.info("Asset ignored")

# ========================================================================== #
# Core generic code of the script

def sha256sum_of_url(url: str) -> str:
    """Compute checksum without saving the file"""
    checksum = hashlib.sha256()
    for chunk in requests.get(url, stream=True).iter_content():
        checksum.update(chunk)
    return checksum.hexdigest()

def write_src_file(name: str, asset_url: str, extension: str,
                   extract: bool = True, subdir: bool = True) -> None:
    """Rewrite conf/app.src"""
    logging.info("Writing %s...", name)

    with open(f"conf/{name}", "w", encoding="utf-8") as conf_file:
        conf_file.write(textwrap.dedent(f"""\
            SOURCE_URL={asset_url}
            SOURCE_SUM={sha256sum_of_url(asset_url)}
            SOURCE_SUM_PRG=sha256sum
            SOURCE_FORMAT={extension}
            SOURCE_IN_SUBDIR={str(subdir).lower()}
            SOURCE_EXTRACT={str(extract).lower()}
        """))

def write_github_env(proceed: bool, new_version: str, branch: str):
    """Those values will be used later in the workflow"""
    if "GITHUB_ENV" not in os.environ:
        logging.warning("GITHUB_ENV is not in the envvars, assuming not in CI")
        return
    with open(os.environ["GITHUB_ENV"], "w", encoding="utf-8") as github_env:
        github_env.write(textwrap.dedent(f"""\
            VERSION={new_version}
            BRANCH={branch}
            PROCEED={str(proceed).lower()}
        """))

def main():
    repository_path = Path(__file__).parent.parent.parent
    manifest_toml = repository_path / "manifest.toml"
    if manifest_toml.exists():
        with open(manifest_toml, "r", encoding="utf-8") as manifest_file:
            manifest = tomlkit.parse(manifest_file.read())
    else:
        with open("manifest.json", "r", encoding="utf-8") as manifest_file:
            manifest = json.load(manifest_file)
    repo = manifest["upstream"]["code"]

    current_version = version.Version(manifest["version"].split("~")[0])
    latest_version, release_info = get_latest_version(repo)
    logging.info("Current version: %s", current_version)
    logging.info("Latest upstream version: %s", latest_version)

    # Proceed only if the retrieved version is greater than the current one
    if latest_version <= current_version:
        logging.warning("No new version available")
        write_github_env(False, "", "")
        return

    # Proceed only if a PR for this new version does not already exist
    branch = f"ci-auto-update-v{latest_version}"
    command = ["git", "ls-remote", "--exit-code", "-h", repo, branch]
    if run(command, stderr=PIPE, stdout=PIPE, check=False).returncode == 0:
        logging.warning("A branch already exists for this update")
        write_github_env(False, "", "")
        return

    assets = get_asset_urls_of_release(repo, release_info)
    logging.info("%d available asset(s)", len(assets))
    for asset in assets:
        handle_asset(asset)

    manifest["version"] = f"{latest_version}~ynh1"
    if manifest_toml.exists():
        with open(manifest_toml, "w", encoding="utf-8") as manifest_file:
            tomlkit.dump(manifest, manifest_file)
    else:
        with open("manifest.json", "w", encoding="utf-8") as manifest_file:
            json.dump(manifest, manifest_file, indent=4, ensure_ascii=False)
            manifest_file.write("\n")

    write_github_env(True, latest_version, branch)


if __name__ == "__main__":
    main()