"""Extract script and region constants from Script.h."""
import csv
import os
import re
import sys

from typing import Iterator, List, Tuple

Item = Tuple[str, int]

def list_enums(filename: str) -> Iterator[Item]:
    """List enum definitions in a file."""
    with open(filename, 'rb') as fp:
        data = fp.read()
    for item in re.finditer(rb'^\s*(\w+)\s*=\s*(\d+)', data, re.MULTILINE):
        name, value = item.groups()
        yield name.decode('ASCII'), int(value)

def index_of(data: List[Item], key: str) -> int:
    for i, (name, _) in enumerate(data):
        if name == key:
            return i
    raise ValueError('missing value: {!r}'.format(key))

def slice(data: List[Item], first: str, last: str) -> List[Item]:
    return data[index_of(data, first):index_of(data, last)+1]

def write_csv(fname: str, data: List[Item]) -> None:
    print('Writing', fname, file=sys.stderr)
    with open(fname, 'w') as fp:
        w = csv.writer(fp)
        w.writerow(['Name', 'Value'])
        for item in data:
            w.writerow(item)

def process_script(filename: str) -> None:
    scripts: List[Item] = []
    regions: List[Item] = []
    for name, value in list_enums(filename):
        if name.startswith('sm'):
            scripts.append((name, value))
        elif name.startswith('ver'):
            regions.append((name, value))
    write_csv('script.csv', slice(scripts, 'smRoman', 'smUninterp'))
    write_csv('region.csv', slice(regions, 'verUS', 'verGreenland'))

def process_textcommon(filename: str) -> None:
    encodings: List[Item] = []
    for name, value in list_enums(filename):
        if name.startswith('kTextEncoding'):
            encodings.append((name, value))
    write_csv('encoding.csv',
              slice(encodings, 'kTextEncodingMacRoman',
                    'kTextEncodingMacKeyboardGlyphs'))

def process(filename: str) -> None:
    name = os.path.basename(filename).lower()
    if name == 'script.h':
        process_script(filename)
    elif name == 'textcommon.h':
        process_textcommon(filename)
    else:
        print('Error: unknown header file:', repr(filename), file=sys.stderr)
        raise SystemExit(1)

def main(argv: List[str]) -> None:
    if not argv:
        sys.stderr.write(
            'Usage: script_gen.py [<file.h>...]\n'
            'This will read Script.h and TextCommon.h\n')
        raise SystemExit(2)
    for arg in argv:
        process(arg)

if __name__ == '__main__':
    main(sys.argv[1:])