#!/usr/bin/env python3
"""
Build a single self-contained HTML file from the source files.

Usage:
    python3 build.py [output.html]

If output is not given, defaults to 'background-standalone.html'.

What gets inlined:
  - config.js, i18n.js                       (plain <script> swap)
  - vendor/suncalc.js, vendor/clouds3d.js    (plain <script> swap)
  - vendor/stars.json                        (window.__starsData)
  - every theme CSS referenced by window.THEMES
                                             (window.__inlineThemeCss,
                                              so theme switching works
                                              without any files)

The result needs NO sibling files. Note that runtime DATA is still
fetched when the page loads: basemap/elevation tiles (via the nginx
CORS proxies of the Docker image), Overpass road + place data and the
Open-Meteo weather API. Serve the standalone file from the same nginx
(or a warm IndexedDB cache = fully offline) for the full experience;
opened via file:// it still runs sky, clouds and the whole UI, just
without the textured ground.
"""

import json
import os
import re
import sys

ROOT = os.path.dirname(os.path.abspath(__file__))


def read(path):
    with open(os.path.join(ROOT, path), 'r', encoding='utf-8') as f:
        return f.read()


def guard(s):
    # a literal </script> inside an inline block would end it early
    return s.replace('</', '<\\/')


def inline_script(html, tag, body):
    old = '<script src="%s"></script>' % tag
    new = '<script>\n%s\n</script>' % body
    if old not in html:
        raise SystemExit('build.py: expected tag not found: ' + tag)
    return html.replace(old, new, 1)


def parse_themes(config_src):
    m = re.search(r'window\.THEMES\s*=\s*\{(.*?)\}', config_src, re.S)
    if not m:
        raise SystemExit('build.py: window.THEMES not found in config.js')
    return dict(re.findall(r"'([^']+)'\s*:\s*'([^']+\.css)'", m.group(1)))


def main():
    out = sys.argv[1] if len(sys.argv) > 1 else 'background-standalone.html'
    html = read('background.html')

    config_src = read('config.js')
    themes = parse_themes(config_src)

    # embedded data preamble (before clouds3d's own scripts run)
    stars = json.loads(read('vendor/stars.json'))
    theme_css = {name: read(fname) for name, fname in themes.items()}
    embed = (
        '<script>\n'
        'window.__starsData = %s;\n'
        'window.__inlineThemeCss = %s;\n'
        '</script>\n'
        % (json.dumps(stars, separators=(',', ':')),
           json.dumps(theme_css))
    )
    anchor = '<script src="vendor/suncalc.js"></script>'
    html = html.replace(anchor, embed + anchor, 1)

    html = inline_script(html, 'config.js', read('config.js'))
    html = inline_script(html, 'i18n.js', read('i18n.js'))
    html = inline_script(html, 'vendor/suncalc.js', read('vendor/suncalc.js'))
    html = inline_script(html, 'vendor/plane3d.js', read('vendor/plane3d.js'))
    html = inline_script(html, 'vendor/clouds3d.js', read('vendor/clouds3d.js'))

    # the default <link id="theme-css" href="ash.css"> stays but is
    # disabled by the inline-theme loader; keep a guarded fallback anyway
    html = html.replace('<link id="theme-css"', '<!-- standalone: themes embedded -->\n    <link id="theme-css"', 1)

    with open(os.path.join(ROOT, out), 'w', encoding='utf-8') as f:
        f.write(html)

    print('Wrote %s (%d bytes)' % (out, len(html)))
    print('Inlined: config.js, i18n.js, suncalc.js, clouds3d.js,')
    print('         stars.json (%d entries), themes: %s'
          % (len(stars), ', '.join(themes)))


if __name__ == '__main__':
    main()