#!/usr/bin/env python3

import argparse
from hashlib import sha256
import os
import subprocess
import sys


def _main():
    args = _parse_args()
    args.func(args)


def _parse_args():
    parser = argparse.ArgumentParser()
    subparsers = parser.add_subparsers(dest="command", required=True)

    approve_parser = subparsers.add_parser("approve")
    approve_parser.set_defaults(func=_approve)
    approve_parser.add_argument("--all", "-a", action="store_true")

    diff_parser = subparsers.add_parser("diff")
    diff_parser.set_defaults(func=_diff)
    diff_parser.add_argument("code", nargs="?")

    ls_parser = subparsers.add_parser("ls")
    ls_parser.set_defaults(func=_ls)

    reject_parser = subparsers.add_parser("reject")
    reject_parser.set_defaults(func=_reject)
    reject_parser.add_argument("--all", "-a", action="store_true")

    return parser.parse_args()


def _approve(args):
    if args.all:
        for path in _find_actual_paths():
            expected_path = _actual_path_to_expected_path(path)
            print("replace\n    {}\nwith\n    {}".format(expected_path, path), file=sys.stderr)
            os.replace(path, expected_path)
    else:
        raise Exception("not implemented yet")


def _diff(args):
    if args.code is None:
        for actual_path in _find_actual_paths():
            _render_diff(actual_path)
            print()

    else:
        matches = []

        for actual_path in _find_actual_paths():
            name = _path_to_name(actual_path)
            code = _name_to_code(name)
            if code.startswith(args.code):
                matches.append(actual_path)

        if len(matches) == 0:
            raise ValueError(f"could not find {args.code}")
        elif len(matches) > 1:
            raise ValueError(f"multiple matches for {args.code}")
        else:
            actual_path = matches[0]
            _render_diff(actual_path)


def _render_diff(actual_path):
    expected_path = _actual_path_to_expected_path(actual_path)
    name = _path_to_name(actual_path)
    code = _name_to_code(name)
    print("Code:", code)
    print("Name:", name, flush=True)
    subprocess.run(["colordiff", "-u", "--new-file", expected_path, actual_path])


def _ls(args):
    for actual_path in _find_actual_paths():
        name = _path_to_name(actual_path)
        code = _name_to_code(name)
        print("Code:", code)
        print("Name:", name)
        print()


def _reject(args):
    if args.all:
        for path in _find_actual_paths():
            print("delete\n    {}".format(path), file=sys.stderr)
            os.unlink(path)
    else:
        raise Exception("not implemented yet")


def _find_actual_paths():
    for root, dirnames, filenames in os.walk(_snapshots_path()):
        for filename in filenames:
            path = os.path.join(root, filename)
            if _has_extension(path, "actual"):
                yield path


def _snapshots_path():
    return os.path.join(os.path.dirname(__file__), "snapshots")


def _has_extension(path, extension):
    return os.path.splitext(path)[1] == "." + extension


def _actual_path_to_expected_path(actual_path):
    return _replace_extension(actual_path, "expected")


def _replace_extension(path, extension):
    return _remove_extension(path) + "." + extension


def _remove_extension(path):
    return os.path.splitext(path)[0]


def _path_to_name(path):
    return os.path.relpath(os.path.splitext(path)[0], _snapshots_path())


def _name_to_code(name):
    return sha256(name.encode("utf8")).hexdigest()


if __name__ == "__main__":
    _main()