#!/usr/bin/env python3

"""
Update a Python package expression by passing in the `.nix` file, or the directory containing it.
You can pass in multiple files or paths.

You'll likely want to use
``
  $ ./update-python-libraries ../../pkgs/development/python-modules/**/default.nix
``
to update all non-pinned libraries in that folder.
"""

import argparse
import json
import logging
import os
import re
import requests
from concurrent.futures import ThreadPoolExecutor as Pool
from packaging.version import Version as _Version
from packaging.version import InvalidVersion
from packaging.specifiers import SpecifierSet
from typing import Optional, Any
import collections
import subprocess

INDEX = "https://pypi.io/pypi"
"""url of PyPI"""

EXTENSIONS = ['tar.gz', 'tar.bz2', 'tar', 'zip', '.whl']
"""Permitted file extensions. These are evaluated from left to right and the first occurance is returned."""

PRERELEASES = False

BULK_UPDATE = False

GIT = "git"

NIXPKGS_ROOT = subprocess.check_output(["git", "rev-parse", "--show-toplevel"]).decode('utf-8').strip()

logging.basicConfig(level=logging.INFO)


class Version(_Version, collections.abc.Sequence):

    def __init__(self, version):
        super().__init__(version)
        # We cannot use `str(Version(0.04.21))` because that becomes `0.4.21`
        # https://github.com/avian2/unidecode/issues/13#issuecomment-354538882
        self.raw_version = version

    def __getitem__(self, i):
        return self._version.release[i]

    def __len__(self):
        return len(self._version.release)

    def __iter__(self):
        yield from self._version.release


def _get_values(attribute, text):
    """Match attribute in text and return all matches.

    :returns: List of matches.
    """
    regex = fr'{re.escape(attribute)}\s+=\s+"(.*)";'
    regex = re.compile(regex)
    values = regex.findall(text)
    return values


def _get_attr_value(attr_path: str) -> Optional[Any]:
    try:
        response = subprocess.check_output([
            "nix",
            "--extra-experimental-features", "nix-command",
            "eval",
            "-f", f"{NIXPKGS_ROOT}/default.nix",
            "--json",
            f"{attr_path}"
        ])
        return json.loads(response.decode())
    except (subprocess.CalledProcessError, ValueError):
        return None


def _get_unique_value(attribute, text):
    """Match attribute in text and return unique match.

    :returns: Single match.
    """
    values = _get_values(attribute, text)
    n = len(values)
    if n > 1:
        raise ValueError("found too many values for {}".format(attribute))
    elif n == 1:
        return values[0]
    else:
        raise ValueError("no value found for {}".format(attribute))

def _get_line_and_value(attribute, text, value=None):
    """Match attribute in text. Return the line and the value of the attribute."""
    if value is None:
        regex = rf'({re.escape(attribute)}\s+=\s+\"(.*)\";)'
    else:
        regex = rf'({re.escape(attribute)}\s+=\s+\"({re.escape(value)})\";)'
    regex = re.compile(regex)
    results = regex.findall(text)
    n = len(results)
    if n > 1:
        raise ValueError("found too many values for {}".format(attribute))
    elif n == 1:
        return results[0]
    else:
        raise ValueError("no value found for {}".format(attribute))


def _replace_value(attribute, value, text, oldvalue=None):
    """Search and replace value of attribute in text."""
    if oldvalue is None:
        old_line, old_value = _get_line_and_value(attribute, text)
    else:
        old_line, old_value = _get_line_and_value(attribute, text, oldvalue)
    new_line = old_line.replace(old_value, value)
    new_text = text.replace(old_line, new_line)
    return new_text


def _fetch_page(url):
    r = requests.get(url)
    if r.status_code == requests.codes.ok:
        return r.json()
    else:
        raise ValueError("request for {} failed".format(url))


def _fetch_github(url):
    headers = {}
    token = os.environ.get('GITHUB_API_TOKEN')
    if token:
        headers["Authorization"] = f"token {token}"
    r = requests.get(url, headers=headers)

    if r.status_code == requests.codes.ok:
        return r.json()
    else:
        raise ValueError("request for {} failed".format(url))


def _hash_to_sri(algorithm, value):
    """Convert a hash to its SRI representation"""
    return subprocess.check_output([
        "nix",
        "hash",
        "to-sri",
        "--type", algorithm,
        value
    ]).decode().strip()


def _skip_bulk_update(attr_name: str) -> bool:
    return bool(_get_attr_value(
        f"{attr_name}.skipBulkUpdate"
    ))


SEMVER = {
    'major' : 0,
    'minor' : 1,
    'patch' : 2,
}


def _determine_latest_version(current_version, target, versions):
    """Determine latest version, given `target`.
    """
    current_version = Version(current_version)

    def _parse_versions(versions):
        for v in versions:
            try:
                yield Version(v)
            except InvalidVersion:
                pass

    versions = _parse_versions(versions)

    index = SEMVER[target]

    ceiling = list(current_version[0:index])
    if len(ceiling) == 0:
        ceiling = None
    else:
        ceiling[-1]+=1
        ceiling = Version(".".join(map(str, ceiling)))

    # We do not want prereleases
    versions = SpecifierSet(prereleases=PRERELEASES).filter(versions)

    if ceiling is not None:
        versions = SpecifierSet(f"<{ceiling}").filter(versions)

    return (max(sorted(versions))).raw_version


def _get_latest_version_pypi(package, extension, current_version, target):
    """Get latest version and hash from PyPI."""
    url = "{}/{}/json".format(INDEX, package)
    json = _fetch_page(url)

    versions = json['releases'].keys()
    version = _determine_latest_version(current_version, target, versions)

    try:
        releases = json['releases'][version]
    except KeyError as e:
        raise KeyError('Could not find version {} for {}'.format(version, package)) from e
    for release in releases:
        if release['filename'].endswith(extension):
            # TODO: In case of wheel we need to do further checks!
            sha256 = release['digests']['sha256']
            break
    else:
        sha256 = None
    return version, sha256, None


def _get_latest_version_github(package, extension, current_version, target):
    def strip_prefix(tag):
        return re.sub("^[^0-9]*", "", tag)

    def get_prefix(string):
        matches = re.findall(r"^([^0-9]*)", string)
        return next(iter(matches), "")

    # when invoked as an updateScript, UPDATE_NIX_ATTR_PATH will be set
    # this allows us to work with packages which live outside of python-modules
    attr_path = os.environ.get("UPDATE_NIX_ATTR_PATH", f"python3Packages.{package}")
    try:
        homepage = subprocess.check_output(
            ["nix", "eval", "-f", f"{NIXPKGS_ROOT}/default.nix", "--raw", f"{attr_path}.src.meta.homepage"])\
            .decode('utf-8')
    except Exception as e:
        raise ValueError(f"Unable to determine homepage: {e}")
    owner_repo = homepage[len("https://github.com/"):]  # remove prefix
    owner, repo = owner_repo.split("/")

    url = f"https://api.github.com/repos/{owner}/{repo}/releases"
    all_releases = _fetch_github(url)
    releases = list(filter(lambda x: not x['prerelease'], all_releases))

    if len(releases) == 0:
        raise ValueError(f"{homepage} does not contain any stable releases")

    versions = map(lambda x: strip_prefix(x['tag_name']), releases)
    version = _determine_latest_version(current_version, target, versions)

    release = next(filter(lambda x: strip_prefix(x['tag_name']) == version, releases))
    prefix = get_prefix(release['tag_name'])

    # some attributes require using the fetchgit
    git_fetcher_args = []
    if (_get_attr_value(f"{attr_path}.src.fetchSubmodules")):
        git_fetcher_args.append("--fetch-submodules")
    if (_get_attr_value(f"{attr_path}.src.fetchLFS")):
        git_fetcher_args.append("--fetch-lfs")
    if (_get_attr_value(f"{attr_path}.src.leaveDotGit")):
        git_fetcher_args.append("--leave-dotGit")

    if git_fetcher_args:
        algorithm = "sha256"
        cmd = [
            "nix-prefetch-git",
            f"https://github.com/{owner}/{repo}.git",
            "--hash", algorithm,
            "--rev", f"refs/tags/{release['tag_name']}"
        ]
        cmd.extend(git_fetcher_args)
        response = subprocess.check_output(cmd)
        document = json.loads(response.decode())
        hash = _hash_to_sri(algorithm, document[algorithm])
    else:
        try:
            hash = subprocess.check_output([
                "nix-prefetch-url",
                "--type", "sha256",
                "--unpack",
                f"{release['tarball_url']}"
            ], stderr=subprocess.DEVNULL).decode('utf-8').strip()
        except (subprocess.CalledProcessError, UnicodeError):
            # this may fail if they have both a branch and a tag of the same name, attempt tag name
            tag_url = str(release['tarball_url']).replace("tarball","tarball/refs/tags")
            hash = subprocess.check_output([
                "nix-prefetch-url",
                "--type", "sha256",
                "--unpack",
                tag_url
            ], stderr=subprocess.DEVNULL).decode('utf-8').strip()

    return version, hash, prefix


FETCHERS = {
    'fetchFromGitHub'   :   _get_latest_version_github,
    'fetchPypi'         :   _get_latest_version_pypi,
    'fetchurl'          :   _get_latest_version_pypi,
}


DEFAULT_SETUPTOOLS_EXTENSION = 'tar.gz'


FORMATS = {
    'setuptools'        :   DEFAULT_SETUPTOOLS_EXTENSION,
    'wheel'             :   'whl',
    'pyproject'         :   'tar.gz',
    'flit'              :   'tar.gz'
}

def _determine_fetcher(text):
    # Count occurrences of fetchers.
    nfetchers = sum(text.count('src = {}'.format(fetcher)) for fetcher in FETCHERS.keys())
    if nfetchers == 0:
        raise ValueError("no fetcher.")
    elif nfetchers > 1:
        raise ValueError("multiple fetchers.")
    else:
        # Then we check which fetcher to use.
        for fetcher in FETCHERS.keys():
            if 'src = {}'.format(fetcher) in text:
                return fetcher


def _determine_extension(text, fetcher):
    """Determine what extension is used in the expression.

    If we use:
    - fetchPypi, we check if format is specified.
    - fetchurl, we determine the extension from the url.
    - fetchFromGitHub we simply use `.tar.gz`.
    """
    if fetcher == 'fetchPypi':
        try:
            src_format = _get_unique_value('format', text)
        except ValueError:
            src_format = None   # format was not given

        try:
            extension = _get_unique_value('extension', text)
        except ValueError:
            extension = None    # extension was not given

        if extension is None:
            if src_format is None:
                src_format = 'setuptools'
            elif src_format == 'other':
                raise ValueError("Don't know how to update a format='other' package.")
            extension = FORMATS[src_format]

    elif fetcher == 'fetchurl':
        url = _get_unique_value('url', text)
        extension = os.path.splitext(url)[1]
        if 'pypi' not in url:
            raise ValueError('url does not point to PyPI.')

    elif fetcher == 'fetchFromGitHub':
        extension = "tar.gz"

    return extension


def _update_package(path, target):

    # Read the expression
    with open(path, 'r') as f:
        text = f.read()

    # Determine pname. Many files have more than one pname
    pnames = _get_values('pname', text)

    # Determine version.
    version = _get_unique_value('version', text)

    # First we check how many fetchers are mentioned.
    fetcher = _determine_fetcher(text)

    extension = _determine_extension(text, fetcher)

    # Attempt a fetch using each pname, e.g. backports-zoneinfo vs backports.zoneinfo
    successful_fetch = False
    for pname in pnames:
        if BULK_UPDATE and _skip_bulk_update(f"python3Packages.{pname}"):
            raise ValueError(f"Bulk update skipped for {pname}")
        try:
            new_version, new_sha256, prefix = FETCHERS[fetcher](pname, extension, version, target)
            successful_fetch = True
            break
        except ValueError:
            continue

    if not successful_fetch:
        raise ValueError(f"Unable to find correct package using these pnames: {pnames}")

    if new_version == version:
        logging.info("Path {}: no update available for {}.".format(path, pname))
        return False
    elif Version(new_version) <= Version(version):
        raise ValueError("downgrade for {}.".format(pname))
    if not new_sha256:
        raise ValueError("no file available for {}.".format(pname))

    text = _replace_value('version', new_version, text)

    # hashes from pypi are 16-bit encoded sha256's, normalize it to sri to avoid merge conflicts
    # sri hashes have been the default format since nix 2.4+
    sri_hash = _hash_to_sri("sha256", new_sha256)

    # retrieve the old output hash for a more precise match
    if old_hash := _get_attr_value(f"python3Packages.{pname}.src.outputHash"):
        # fetchers can specify a sha256, or a sri hash
        try:
            text = _replace_value('hash', sri_hash, text, old_hash)
        except ValueError:
            text = _replace_value('sha256', sri_hash, text, old_hash)
    else:
        raise ValueError(f"Unable to retrieve old hash for {pname}")

    if fetcher == 'fetchFromGitHub':
        # in the case of fetchFromGitHub, it's common to see `rev = version;` or `rev = "v${version}";`
        # in which no string value is meant to be substituted. However, we can just overwrite the previous value.
        regex = r'(rev\s+=\s+[^;]*;)'
        regex = re.compile(regex)
        matches = regex.findall(text)
        n = len(matches)

        if n == 0:
            raise ValueError("Unable to find rev value for {}.".format(pname))
        else:
            # forcefully rewrite rev, incase tagging conventions changed for a release
            match = matches[0]
            text = text.replace(match, f'rev = "refs/tags/{prefix}${{version}}";')
            # incase there's no prefix, just rewrite without interpolation
            text = text.replace('"${version}";', 'version;')

    with open(path, 'w') as f:
        f.write(text)

        logging.info("Path {}: updated {} from {} to {}".format(path, pname, version, new_version))

    result = {
        'path'  : path,
        'target': target,
        'pname': pname,
        'old_version'   : version,
        'new_version'   : new_version,
        #'fetcher'       : fetcher,
        }

    return result


def _update(path, target):

    # We need to read and modify a Nix expression.
    if os.path.isdir(path):
        path = os.path.join(path, 'default.nix')

    # If a default.nix does not exist, we quit.
    if not os.path.isfile(path):
        logging.info("Path {}: does not exist.".format(path))
        return False

    # If file is not a Nix expression, we quit.
    if not path.endswith(".nix"):
        logging.info("Path {}: does not end with `.nix`.".format(path))
        return False

    try:
        return _update_package(path, target)
    except ValueError as e:
        logging.warning("Path {}: {}".format(path, e))
        return False


def _commit(path, pname, old_version, new_version, pkgs_prefix="python: ", **kwargs):
    """Commit result.
    """

    msg = f'{pkgs_prefix}{pname}: {old_version} -> {new_version}'

    try:
        subprocess.check_call([GIT, 'add', path])
        subprocess.check_call([GIT, 'commit', '-m', msg])
    except subprocess.CalledProcessError as e:
        subprocess.check_call([GIT, 'checkout', path])
        raise subprocess.CalledProcessError(f'Could not commit {path}') from e

    return True


def main():

    epilog = """
environment variables:
  GITHUB_API_TOKEN\tGitHub API token used when updating github packages
    """
    parser = argparse.ArgumentParser(formatter_class=argparse.RawDescriptionHelpFormatter, epilog=epilog)
    parser.add_argument('package', type=str, nargs='+')
    parser.add_argument('--target', type=str, choices=SEMVER.keys(), default='major')
    parser.add_argument('--commit', action='store_true', help='Create a commit for each package update')
    parser.add_argument('--use-pkgs-prefix', action='store_true', help='Use python3Packages.${pname}: instead of python: ${pname}: when making commits')

    args = parser.parse_args()
    target = args.target

    packages = list(map(os.path.abspath, args.package))

    if len(packages) > 1:
        global BULK_UPDATE
        BULK_UPDATE = True

    logging.info("Updating packages...")

    # Use threads to update packages concurrently
    with Pool() as p:
        results = list(filter(bool, p.map(lambda pkg: _update(pkg, target), packages)))

    logging.info("Finished updating packages.")

    commit_options = {}
    if args.use_pkgs_prefix:
        logging.info("Using python3Packages. prefix for commits")
        commit_options["pkgs_prefix"] = "python3Packages."

    # Commits are created sequentially.
    if args.commit:
        logging.info("Committing updates...")
        # list forces evaluation
        list(map(lambda x: _commit(**x, **commit_options), results))
        logging.info("Finished committing updates")

    count = len(results)
    logging.info("{} package(s) updated".format(count))



if __name__ == '__main__':
    main()
