#!/usr/bin/env python3
import os
import sys
import argparse
import hashlib
import re

whoami = os.path.basename(sys.argv[0])
BANNER = f'''//
// This file is automatically generated by {whoami}.
// Edits will be automatically overwritten if the build is
// run in maintainer mode.
//'''


def warn(*args, **kwargs):
    print(*args, file=sys.stderr, **kwargs)


class Main:
    SOURCES = [whoami, 'job.yml']
    SUMS = 'job.sums'

    def main(self, args=sys.argv[1:], prog=whoami):
        options = self.parse_args(args, prog)
        self.top(options)

    def parse_args(self, args, prog):
        parser = argparse.ArgumentParser(
            prog=prog,
            description='Generate files for QPDFJob',
        )
        mxg = parser.add_mutually_exclusive_group(required=True)
        mxg.add_argument('--check',
                         help='update checksums if files are not up to date',
                         action='store_true', default=False)
        mxg.add_argument('--generate',
                         help='generate files from sources',
                         action='store_true', default=False)
        return parser.parse_args(args)

    def top(self, options):
        if options.check:
            self.check()
        elif options.generate:
            self.generate()
        else:
            exit(f'{whoami} unknown mode')

    def get_hashes(self):
        hashes = {}
        for i in sorted(self.SOURCES):
            m = hashlib.sha256()
            with open(i, 'rb') as f:
                m.update(f.read())
            hashes[i] = m.hexdigest()
        return hashes

    def check(self):
        hashes = self.get_hashes()
        match = False
        try:
            old_hashes = {}
            with open(self.SUMS, 'r') as f:
                for line in f.readlines():
                    m = re.match(r'^(\S+) (\S+)\s*$', line)
                    if m:
                        old_hashes[m.group(1)] = m.group(2)
            match = old_hashes == hashes
        except Exception:
            pass
        if not match:
            exit(f'{whoami}: auto job inputs have changed')

    def update_hashes(self):
        hashes = self.get_hashes()
        with open(self.SUMS, 'w') as f:
            print(f'# Generated by {whoami}', file=f)
            for k, v in hashes.items():
                print(f'{k} {v}', file=f)

    def generate(self):
        warn(f'{whoami}: regenerating auto job files')

        with open('libqpdf/qpdf/auto_job_decl.hh', 'w') as f:
            print(BANNER, file=f)

        # Update hashes last to ensure that this will be rerun in the
        # event of a failure.
        self.update_hashes()


if __name__ == '__main__':
    try:
        os.chdir(os.path.dirname(os.path.realpath(__file__)))
        Main().main()
    except KeyboardInterrupt:
        exit(130)