#!/usr/bin/env python
from __future__ import print_function, unicode_literals

import argparse
import logging
import os
import re
import sys


_DESCRIPTION = """\
Migrate arbitrary `.go` sources (mostly) from the v1 to v2 API.
"""
_V2_IMPORT = '"gopkg.in/urfave/cli.v2"'
_MIGRATORS = {}


def main(sysargs=sys.argv[:]):
    parser = argparse.ArgumentParser(
        description=_DESCRIPTION,
        formatter_class=argparse.ArgumentDefaultsHelpFormatter)
    parser.add_argument('path', nargs='*',
                        type=os.path.abspath, default=os.getcwd())
    parser.add_argument('-w', '--write', help='write changes back to file',
                        action='store_true', default=False)
    parser.add_argument('-q', '--quiet', help='quiet down the logging',
                        action='store_true', default=False)
    parser.add_argument('--selftest', help='run internal tests',
                        action='store_true', default=False)

    args = parser.parse_args(sysargs[1:])

    if args.selftest:
        logging.basicConfig(
            level=logging.WARN,
            format='selftest: %(message)s'
        )
        test_migrators()
        return 0

    logging.basicConfig(
        level=(logging.FATAL if args.quiet else logging.INFO),
        format='%(message)s'
    )

    paths = args.path
    if len(paths) == 0:
        paths = ['.']

    for filepath in _find_candidate_files(paths):
        updated_source = _update_filepath(filepath)
        if args.write:
            logging.info('Updating %s', filepath)

            with open(filepath, 'w') as outfile:
                outfile.write(updated_source)
        else:
            logging.info('// Updated %s:', filepath)
            print(updated_source)

    return 0


def _find_candidate_files(paths):
    for path in paths:
        if not os.path.isdir(path):
            yield path
            continue

        for curdir, dirs, files in os.walk(path):
            for i, dirname in enumerate(dirs[:]):
                if dirname.startswith('.'):
                    dirs.pop(i)

            for filename in files:
                if not filename.decode('utf-8').endswith('.go'):
                    continue

                filepath = os.path.join(curdir, filename)
                if not os.access(filepath, os.R_OK | os.W_OK):
                    continue

                yield filepath


def _update_filepath(filepath):
    with open(filepath) as infile:
        return _update_source(infile.read())


def _update_source(source):
    for migrator, func in _MIGRATORS.items():
        logging.info('Running %s migrator', migrator)
        source = func(source)
    return source


def _migrator(func):
    _MIGRATORS[func.__name__.replace('_migrate_', '')] = func
    return func


@_migrator
def _migrate_command_slice(source):
    return re.sub(
        '(?P<prefix>\\[\\])cli\\.Command{',
        _command_slice_repl, source
    )


def _command_slice_repl(match):
    return '{prefix}*cli.Command{{'.format(**match.groupdict())


@_migrator
def _migrate_command_literal(source):
    return re.sub(
        '(?P<prefix>\\s+)cli\\.Command{',
        _command_literal_repl, source
    )


def _command_literal_repl(match):
    return '{prefix}&cli.Command{{'.format(**match.groupdict())


@_migrator
def _migrate_slice_types(source):
    return re.sub(
        '&cli\\.(?P<type>IntSlice|StringSlice){(?P<args>[^}]*)}',
        _slice_type_repl, source, flags=re.DOTALL
    )


def _slice_type_repl(match):
    return 'cli.New{type}({args})'.format(**match.groupdict())


@_migrator
def _migrate_flag_literals(source):
    return re.sub(
        '(?P<prefix>\\s+)cli\\.(?P<type>\\w+)Flag{',
        _flag_literal_repl, source
    )


def _flag_literal_repl(match):
    return '{prefix}&cli.{type}Flag{{'.format(**match.groupdict())


@_migrator
def _migrate_v1_imports(source):
    return re.sub(
        '"(?:github\\.com|gopkg\\.in)/(?:codegangsta|urfave)/cli(?:\\.v1|)"',
        _V2_IMPORT, source
    )


@_migrator
def _migrate_new_exit_error(source):
    return re.sub('cli\\.NewExitError', 'cli.Exit', source)


@_migrator
def _migrate_bool_t_flag(source):
    return re.sub(
        'cli\\.BoolTFlag{(?P<args>[^}]*)}',
        _bool_t_flag_repl, source, flags=re.DOTALL
    )


def _bool_t_flag_repl(match):
    return 'cli.BoolFlag{{Value: true,{args}}}'.format(**match.groupdict())


@_migrator
def _migrate_context_args_index(source):
    return re.sub(
        '\\.Args\\(\\)\\[(?P<index>\\d+)\\]',
        _context_args_index_repl, source
    )


def _context_args_index_repl(match):
    return '.Args().Get({index})'.format(**match.groupdict())


@_migrator
def _migrate_envvar_string(source):
    return re.sub('EnvVar:(?P<ws>\\s+)"(?P<string>[^"]+)"', _envvar_string_repl, source)


def _envvar_string_repl(match):
    return 'EnvVars:{ws}[]string{{{value}}}'.format(
        value=', '.join([
            '"{}"'.format(s) for s in
            re.split('\\s*,\\s*', match.groupdict()['string'])
        ]),
        **match.groupdict()
    )


@_migrator
def _migrate_flag_name_stringly(source):
    return re.sub(
        '(?P<prefix>\\s+)Name:(?P<ws>\\s+)"(?P<string>[^"]+)"',
        _flag_name_stringly_repl, source
    )


def _flag_name_stringly_repl(match):
    revars = dict(match.groupdict())

    string = revars['string']
    parts = list(
        reversed(
            sorted(
                filter(lambda s: len(s.strip()) > 0, [
                    part.strip() for part in string.split(',')
                ]), key=len
            )
        )
    )

    if len(parts) == 1:
        return '{prefix}Name:{ws}"{string}"'.format(**revars)

    return (
        '{prefix}Name:{ws}"{name}", Aliases: []string{{{aliases}}}'
    ).format(
        name=parts[0],
        aliases=', '.join(['"{}"'.format(s) for s in parts[1:]]),
        **revars
    )


def test_migrators():
    import difflib

    for i, (source, expected) in enumerate(_MIGRATOR_TESTS):
        actual = _update_source(source)
        if expected != actual:
            udiff = difflib.unified_diff(
                expected.splitlines(), actual.splitlines(),
                fromfile='a/source.go', tofile='b/source.go', lineterm=''
            )
            for line in udiff:
                print(line)
            raise AssertionError('migrated source does not match expected')
        logging.warn('Test case %d/%d OK', i+1, len(_MIGRATOR_TESTS))


_MIGRATOR_TESTS = (
    ("""
\t\t\t&cli.StringSlice{"a", "b", "c"},
""", """
\t\t\tcli.NewStringSlice("a", "b", "c"),
"""),
    ("""
\t\tcli.IntFlag{
\t\t\tName:  "yep",
\t\t\tValue: 3,
\t\t}
""", """
\t\t&cli.IntFlag{
\t\t\tName:  "yep",
\t\t\tValue: 3,
\t\t}
"""),
    ("""
\t\tapp.Commands = []cli.Command{
\t\t\t{
\t\t\t\tName: "whatebbs",
\t\t\t},
\t\t}
""", """
\t\tapp.Commands = []*cli.Command{
\t\t\t{
\t\t\t\tName: "whatebbs",
\t\t\t},
\t\t}
"""),
    ("""
\t\tapp.Commands = []cli.Command{
\t\t\tcli.Command{
\t\t\t\tName: "whatebbs",
\t\t\t},
\t\t}
""", """
\t\tapp.Commands = []*cli.Command{
\t\t\t&cli.Command{
\t\t\t\tName: "whatebbs",
\t\t\t},
\t\t}
"""),
    ("""
\t"github.com/codegangsta/cli"
\t"github.com/urfave/cli"
\t"gopkg.in/codegangsta/cli"
\t"gopkg.in/codegangsta/cli.v1"
\t"gopkg.in/urfave/cli"
\t"gopkg.in/urfave/cli.v1"
""", """
\t"gopkg.in/urfave/cli.v2"
\t"gopkg.in/urfave/cli.v2"
\t"gopkg.in/urfave/cli.v2"
\t"gopkg.in/urfave/cli.v2"
\t"gopkg.in/urfave/cli.v2"
\t"gopkg.in/urfave/cli.v2"
"""),
    ("""
\t\t\t\treturn cli.NewExitError("foo whatebber", 9)
""", """
\t\t\t\treturn cli.Exit("foo whatebber", 9)
"""),
    ("""
\t\t\tapp.Flags = []cli.Flag{
\t\t\t\tcli.StringFlag{
\t\t\t\t\tName: "aha",
\t\t\t\t},
\t\t\t\tcli.BoolTFlag{
\t\t\t\t\tName: "blurp",
\t\t\t\t},
\t\t\t}
""", """
\t\t\tapp.Flags = []cli.Flag{
\t\t\t\t&cli.StringFlag{
\t\t\t\t\tName: "aha",
\t\t\t\t},
\t\t\t\t&cli.BoolFlag{Value: true,
\t\t\t\t\tName: "blurp",
\t\t\t\t},
\t\t\t}
"""),
    ("""
\t\t\tAction = func(c *cli.Context) error {
\t\t\t\tif c.Args()[4] == "meep" {
\t\t\t\t\treturn nil
\t\t\t\t}
\t\t\t\treturn errors.New("mope")
\t\t\t}
""", """
\t\t\tAction = func(c *cli.Context) error {
\t\t\t\tif c.Args().Get(4) == "meep" {
\t\t\t\t\treturn nil
\t\t\t\t}
\t\t\t\treturn errors.New("mope")
\t\t\t}
"""),
    ("""
\t\tapp.Flags = []cli.Flag{
\t\t\tcli.StringFlag{
\t\t\t\tName:   "toots",
\t\t\t\tEnvVar: "TOOTS,TOOTERS",
\t\t\t},
\t\t}
""", """
\t\tapp.Flags = []cli.Flag{
\t\t\t&cli.StringFlag{
\t\t\t\tName:   "toots",
\t\t\t\tEnvVars: []string{"TOOTS", "TOOTERS"},
\t\t\t},
\t\t}
"""),
    ("""
\t\tapp.Flags = []cli.Flag{
\t\t\tcli.StringFlag{
\t\t\t\tName:   "t, tootles, toots",
\t\t\t},
\t\t}
""", """
\t\tapp.Flags = []cli.Flag{
\t\t\t&cli.StringFlag{
\t\t\t\tName:   "tootles", Aliases: []string{"toots", "t"},
\t\t\t},
\t\t}
""")
)


if __name__ == '__main__':
    sys.exit(main())