#!/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"'
_V1_IMPORT_RE = re.compile(
    '"(?:github\\.com|gopkg\\.in)/(?:codegangsta|urfave)/cli(?:\\.v1|)"',
)
_SLICE_TYPE_RE = re.compile(
    '&cli\\.(?P<type>IntSlice|StringSlice){(?P<args>[^}]*)}',
    flags=re.DOTALL
)
_FLAG_LITERAL_RE = re.compile(
    '(?P<prefix>[^&]?)cli\\.(?P<type>\\w+)Flag{',
)
_COMMAND_SLICE_RE = re.compile(
    '(?P<prefix>\\[\\])cli\\.Command{',
)
_COMMAND_LITERAL_RE = re.compile(
    '(?P<prefix>\\s+)cli\\.Command{',
)

_MIGRATORS = {}


def main(sysargs=sys.argv[:]):
    parser = argparse.ArgumentParser(
        description=_DESCRIPTION,
        formatter_class=argparse.ArgumentDefaultsHelpFormatter)
    parser.add_argument('basedir', nargs='?', metavar='BASEDIR',
                        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'
    )

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

        for filename in files:
            if not filename.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 _COMMAND_SLICE_RE.sub(_command_slice_repl, source)


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


@_migrator
def _migrate_command_literal(source):
    return _COMMAND_LITERAL_RE.sub(_command_literal_repl, source)


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


@_migrator
def _migrate_slice_types(source):
    return _SLICE_TYPE_RE.sub(_slice_type_repl, source)


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


@_migrator
def _migrate_flag_literals(source):
    return _FLAG_LITERAL_RE.sub(_flag_literal_repl, source)


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


@_migrator
def _migrate_v1_imports(source):
    return _V1_IMPORT_RE.sub(_V2_IMPORT, source)


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"
"""
    )
)


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