#!/usr/bin/env python
"""Simple, on demand git checker"""

import argparse
import errno
import json
import os
import pathlib
import subprocess
import sys

import git


class InvalidGitRepositoryError(Exception):
    """
    InvalidGitRepositoryError

    Raised when invalid repository path is provided
    """


class ValidationError(Exception):
    """ValidationError"""


def eprint(
    *value: object, sep: str | None = ' ', end: str | None = '\n'
) -> None:
    """stdderr print wrapper"""
    print(*value, sep=sep, end=end, file=sys.stderr, flush=True)


class CLIHandler:
    """Helper class used for handleing the growing amount of arguments"""

    def __init__(
        self, args: argparse.Namespace, config_dict: dict[str, list]
    ) -> None:
        """
        :param args: The parsed argparse arguments sent by the caller
        :type args: argparse.Namespace

        :param config_dict: The config file structure
        :type config_dict: dict
        """
        self._args = args
        self._config_dict = config_dict
        self._py_checker = PyChecker(
            tests=self._config_dict['tests'],
            skip=args.skip.split(',') if args.skip else None,
            verbose=args.verbose,
        )
        self._repository_path = pathlib.Path(args.repo_path).absolute()

    def handle_args(self) -> None:
        """Runs the handler"""
        if self._args.python_file:
            self._py_checker.validate_python_file(self._args.python_file)
            return

        repository_handler = GitRepositoryHandler(
            self._repository_path,
            target_extensions=self._config_dict['target_extensions'],
            ignore_dirs=self._config_dict['ignore_dirs'],
        )
        if self._args.all_files:
            selected_files = repository_handler.get_all_target_files()
        else:
            selected_files = repository_handler.get_new_and_modified()

        if not selected_files:
            print('No files selected')
            return

        for target_file in selected_files:
            if self._args.list_only:
                print(target_file)
                continue

            if self._args.verbose:
                print(f'Validating {target_file}:')
            self._py_checker.validate_python_file(target_file)

        return


class GitRepositoryHandler:
    """Handler for the git repository logic"""

    def __init__(
        self,
        repository_path: pathlib.Path,
        target_extensions: list[str],
        ignore_dirs: list[str] | None = None,
    ) -> None:
        """
        Constructs handler for a specific repository path

        It takes `target_extensions` as an input in order to define
        a file as a target. Example ['.py'], ['.cpp', '.cc']

        `ignore_dirs` is used to define a list of directory names to ignore
        (not traverse in) by `get_all_target_files`.

        :param repository_path: Absolute path of the git repository
        :type repository_path: pathlib.Path

        :param target_extensions: A list of file extensions (f.i. ['.py'])
        :type target_extensions: list

        :param ignore_dirs: A list of directory names to ignore when
        :type ignore_dirs: list or None
        """
        self._repository_path = repository_path
        self._target_extensions = target_extensions
        self._ignore_dirs: list[str] = (
            ignore_dirs if ignore_dirs is not None else []
        )

        if not self._repository_path.is_dir():
            raise InvalidGitRepositoryError(
                'Specified path is not a directory'
            )

        try:
            self._git_repository = git.Repo(self._repository_path)
        except git.InvalidGitRepositoryError as err:
            raise InvalidGitRepositoryError(
                'Specified path is pointing to a directory that is not a '
                'Git repository'
            ) from err

    def get_all_target_files(self) -> list[pathlib.Path]:
        """
        Fetches all .py-files

        :return: A list containing the paths of all .py files
        :rtype: list
        """
        all_files_list = []

        for root, _, files in os.walk(self._repository_path):
            if any(idir in root for idir in self._ignore_dirs):
                continue
            all_files_list.extend(
                pathlib.Path(root) / f
                for f in files
                if pathlib.Path(f).suffix.lower() in self._target_extensions
            )

        all_files_list.sort()
        return all_files_list

    def get_new_and_modified(self) -> list[pathlib.Path]:
        """
        Fetches new and modified .py-files using git

        :return: A list of new and modified file paths
        :rtype: list
        """
        modified_files = {
            self._repository_path / pathlib.Path(mfile.a_path)
            for mfile in self._git_repository.index.diff(None)
            if mfile.a_path is not None
            and mfile.a_path.lower().endswith('.py')
        }
        staged_files = {
            self._repository_path / pathlib.Path(sfile.a_path)
            for sfile in self._git_repository.index.diff('HEAD')
            if sfile.a_path is not None
            and sfile.a_path.lower().endswith('.py')
        }
        untracked_files = {
            self._repository_path / pathlib.Path(ufile)
            for ufile in self._git_repository.untracked_files
            if ufile is not None and ufile.lower().endswith('.py')
        }

        return sorted(modified_files | staged_files | untracked_files)


class PyChecker:
    """Implements the checker logic"""

    def __init__(
        self,
        tests: list[dict],
        skip: list[str] | None = None,
        *,
        verbose: bool = False,
    ) -> None:
        """
        :param tests: A list of test dicts
        :type tests: list

        :param skip: A list of test names to skip (default: None)
        :type skip: list or None

        :param verbose: Turn on verbosity (default: False)
        :type verbose: bool
        """
        self._tests = tests
        self._skip = skip if skip is not None else []
        self._verbose = verbose

    def validate_python_file(self, pfile: pathlib.Path) -> None:
        """
        Validates a single .py file against tests

        :param pfile: Python file (absolute path)
        :type pfile: pathlib.Path

        :return: False if validation fails, False otherwise
        :rtype: bool
        """
        for test in self._tests:
            if test['name'] in self._skip:
                if self._verbose:
                    print(f'{pfile} <- {test["name"]} (skipping)')
                continue
            try:
                params = [
                    param.replace('%p', str(pfile)) for param in test['params']
                ]
                if self._verbose:
                    print(f'{pfile} <- {test["name"]} ({" ".join(params)})')
                subprocess.run(params, check=test['check'])
            except subprocess.CalledProcessError as err:
                raise ValidationError(
                    f'{pfile}: {test["name"]} validation failed'
                ) from err


def main(inargs: list[str] | None = None) -> None:
    """Main entry point"""
    parser = argparse.ArgumentParser(
        description='The following options are available'
    )
    parser.add_argument(
        'repo_path',
        metavar='<Git repository path>',
        nargs='?',
        default=pathlib.Path.cwd(),
        help='Git repo path (default: cwd)',
    )
    parser.add_argument(
        '-a',
        '--all-files',
        action='store_true',
        dest='all_files',
        help='Check all files, not only the modified ones',
    )
    parser.add_argument(
        '-c',
        '--config',
        metavar='<file>',
        type=pathlib.Path,
        default=pathlib.Path('~/.pygitchecker.json').expanduser(),
        dest='config_file',
        help='Config file (default: ~/.pygitchecker.json)',
    )
    parser.add_argument(
        '-F',
        '--file',
        metavar='<file>',
        type=str,
        default='',
        dest='python_file',
        help='Validate a particular .py file',
    )
    parser.add_argument(
        '-l',
        '--list-only',
        action='store_true',
        dest='list_only',
        help='Only lists the target files without performing any checks',
    )
    parser.add_argument(
        '-s',
        '--skip',
        metavar='<test1[,test2,test3...]>',
        type=str,
        default='',
        dest='skip',
        help='Skip one or more tests',
    )
    parser.add_argument(
        '-v',
        '--verbose',
        action='store_true',
        dest='verbose',
        help='Verbosity',
    )

    args = parser.parse_args(inargs)

    try:
        with pathlib.Path(args.config_file).open(encoding='utf-8') as fp:
            config_dict = json.load(fp)
    except Exception as exp:
        eprint(f'Unable to parse {args.config_file}: {exp}')
        sys.exit(errno.EIO)

    try:
        cli_handler = CLIHandler(args, config_dict)
        cli_handler.handle_args()
        sys.exit(0)
    except KeyboardInterrupt:
        print('KeyboardInterrupt\n')
        sys.exit(0)
    except InvalidGitRepositoryError as err:
        eprint(f'Invalid Git repository: {err}')
        sys.exit(1)
    except ValidationError as err:
        if args.verbose:
            eprint(f'Validation error: {err}')
        sys.exit(0)


if __name__ == '__main__':
    main()