#!/usr/bin/env python3

# syntax-highlighting-server.py: create a simple HTTP server to highlight
# source for cgit. improves performance compared to invoking python on every
# request.
#
# Requirements: Python 3, pygments.
#
# Usage: Configure your system to run this at boot. Note that this program is
# not hardened, and it can be trivially DoSed. therefore, do not configure it
# to listen on a public network. Once configured, set your cgit source filter
# to syntax-highlighting-client.sh.

from pygments import highlight
from pygments.formatters import HtmlFormatter
from pygments.lexers import guess_lexer, guess_lexer_for_filename
from pygments.lexers.special import TextLexer
from pygments.util import ClassNotFound

def do_highlight(filename, data, style):
    try:
        lexer = guess_lexer_for_filename(filename, data)
    except ClassNotFound:
        try:
            lexer = guess_lexer(data)
            # SqlLexer always gives 0.01
            if lexer.analyse_text(data) <= 0.01:
                lexer = TextLexer()
        except ClassNotFound:
            lexer = TextLexer()
    formatter = HtmlFormatter(style=style, nobackground=True)
    return ''.join([
        f'<!-- Pygments {pygments.__version__}: {lexer.name} ({lexer.__class__.__name__}) -->',
        '<style>', formatter.get_style_defs('.highlight'), '</style>',
        highlight(data, lexer, formatter)
    ])

def parse_args():
    import argparse
    parser = argparse.ArgumentParser(description='syntax highlighting server',
            formatter_class=argparse.ArgumentDefaultsHelpFormatter)
    parser.add_argument('--host', type=str, default='127.0.0.1',
            help='the host to listen on')
    parser.add_argument('--port', type=int, default=4872,
            help='the port to listen on')
    parser.add_argument('--style', type=str, default='pastie',
            help='pygments formatting style')
    parser.add_argument('--preload', type=bool, default=True,
            help='preload lexers and formatters to reduce fork memory usage')
    return parser.parse_args()

async def handle_highlight(request):
    import asyncio
    from aiohttp import web
    loop = asyncio.get_running_loop()
    text = await request.text()
    result = await loop.run_in_executor(
            request.app['pool'], do_highlight,
            request.query['filename'], text, request.app['style'])
    return web.Response(text=result)

def main():
    args = parse_args()

    from aiohttp import web
    from concurrent.futures import ProcessPoolExecutor

    if args.preload:
        guess_lexer('')

    with ProcessPoolExecutor() as pool:
        app = web.Application()
        app['pool'] = pool
        app['style'] = args.style
        app.add_routes([web.post('/highlight', handle_highlight)])
        web.run_app(app, host=args.host, port=args.port)

if __name__ == '__main__':
    main()