#!/usr/bin/env python3

from os import path
from typing import List, Tuple
import argparse


def replace_all(
        replacements: List[Tuple[str, str]],
        lines: List[str],
) -> List[str]:
    '''Runs string replacement on each of lines.

    Only one pattern found in each line will be replaced.
    '''
    result = []
    for l in lines:
        for (needle, replacement) in replacements:
            x = l.replace(needle, replacement)
        result.append(x)
    return result


def main():
    parser = argparse.ArgumentParser(
        prog='generate_file',
        description='Runs line-by-line string substitutions on input files',
        epilog='Output files are named after input files with any .in extension stripped',
    )
    parser.add_argument(
        '--replace',
        '-r',
        help='parameters <A> <B> will replace <A> with <B>',
        required=True,
        nargs=2,
        action='append',
    )
    parser.add_argument(
        '--outdir',
        '-o',
        required=True,
        help='directory to write output to',
    )
    parser.add_argument('inputs', nargs='+', help='files to read in')
    settings = parser.parse_args()

    for infile in settings.inputs:
        base = path.basename(infile)
        if base.endswith('.in'):
            base = base[0:-3]
        if not base:
            raise ValueError(
                'Input file "{}" has an empty basefile name after stripping any ".in" suffix'
                .format(infile))
        outfile = path.join(settings.outdir, base)
        with open(infile, 'r', encoding='utf-8') as reader:
            lines = reader.readlines()
        with open(outfile, 'w', encoding='utf-8') as writer:
            writer.writelines(replace_all(settings.replace, lines))


if __name__ == '__main__':
    main()