#! /usr/bin/env nix-shell
#! nix-shell -i python3 -p "python3.withPackages(ps: with ps; [ packaging requests toolz ])" -p git

"""
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/*
``
to update all libraries in that folder.
"""

import argparse
import logging
import os
import re
import requests
import toolz
from concurrent.futures import ThreadPoolExecutor as Pool
from packaging.version import Version as _Version
from packaging.version import InvalidVersion
from packaging.specifiers import SpecifierSet
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

import logging
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 = '{}\s+=\s+"(.*)";'.format(attribute)
    regex = re.compile(regex)
    values = regex.findall(text)
    return values

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):
    """Match attribute in text. Return the line and the value of the attribute."""
    regex = '({}\s+=\s+"(.*)";)'.format(attribute)
    regex = re.compile(regex)
    value = regex.findall(text)
    n = len(value)
    if n > 1:
        raise ValueError("found too many values for {}".format(attribute))
    elif n == 1:
        return value[0]
    else:
        raise ValueError("no value found for {}".format(attribute))


def _replace_value(attribute, value, text):
    """Search and replace value of attribute in text."""
    old_line, old_value = _get_line_and_value(attribute, text)
    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))


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


def _get_latest_version_github(package, extension, current_version, target):
    raise ValueError("updating from GitHub is not yet supported.")


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'
}

def _determine_fetcher(text):
    # Count occurences 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 as e:
            src_format = None   # format was not given

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

        if extension is None:
            if src_format is None:
                src_format = 'setuptools'
            elif src_format == 'flit':
                raise ValueError("Don't know how to update a Flit 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':
        raise ValueError('updating from GitHub is not yet implemented.')

    return extension


def _update_package(path, target):

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

    # Determine pname.
    pname = _get_unique_value('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)

    new_version, new_sha256 = FETCHERS[fetcher](pname, extension, version, target)

    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)
    text = _replace_value('sha256', new_sha256, text)

    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, **kwargs):
    """Commit result.
    """

    msg = f'python: {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():

    parser = argparse.ArgumentParser()
    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')

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

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

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

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

    logging.info("Finished updating packages.")

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

    count = sum(map(bool, results))
    logging.info("{} package(s) updated".format(count))



if __name__ == '__main__':
    main()