#!/usr/bin/env python3
"""Bundle the deck into one self-contained HTML file for uploading.

    python3 slides/build.py              # writes slides/dist/hands-on-bgp.html

Everything the page fetches at runtime is inlined: reveal.js and its plugins
(from the vendored copy, so run vendor-reveal.sh first), the stylesheets, the
favicon, our scripts and the Markdown sections. The result opens from any web
server and from disk. Two things still need a network: the IBM Plex fonts
(Google Fonts) and the live DNS and RIPE lookups.
"""
import base64
import os
import re
import sys

HERE = os.path.dirname(os.path.abspath(__file__))
REVEAL = os.path.join(HERE, "reveal.js", "dist")
OUT = os.path.join(HERE, "dist", "hands-on-bgp.html")


def read(*parts):
    with open(os.path.join(HERE, *parts), encoding="utf-8") as f:
        return f.read()


def main():
    if not os.path.isdir(REVEAL):
        sys.exit("reveal.js is not vendored; run slides/vendor-reveal.sh first")
    html = read("index.html")

    # Stylesheets: reveal's first, then ours, as the loader orders them.
    css = "\n".join(read("reveal.js", "dist", p) for p in ["reset.css", "reveal.css", "plugin/highlight/monokai.css"])
    css += "\n" + read("theme.css") + "\n" + read("style.css")
    html = re.sub(r'\s*<link rel="stylesheet" href="theme\.css[^"]*" id="deck-style" />', "", html)
    html = re.sub(r'\s*<link rel="stylesheet" href="style\.css[^"]*" />', f"\n        <style>\n{css}\n        </style>", html, count=1)

    icon = "data:image/svg+xml;base64," + base64.b64encode(read("images", "favicon.svg").encode()).decode()
    html = html.replace('href="images/favicon.svg"', f'href="{icon}"')

    # Sections: the Markdown goes inline in a text/template script.
    def inline_section(m):
        attrs, path = m.group(1), m.group(2)
        text = read(path)
        if "</script" in text.lower():
            sys.exit(f"{path} contains '</script', which cannot be inlined")
        return f'<section data-markdown{attrs}>\n<script type="text/template">\n{text}\n</script>\n</section>'
    html, n = re.subn(r'<section\s+data-markdown="([^"]+)"((?:\s+data-[a-z-]+="[^"]*")*)\s*></section>',
                      lambda m: inline_section(type("M", (), {"group": lambda self, i: (None, m.group(2), m.group(1))[i]})()), html)
    if n == 0:
        sys.exit("no data-markdown sections found in index.html")

    # Our scripts.
    for name in ["dns-lookup.js", "prefix-explorer.js"]:
        html, k = re.subn(rf'<script src="{re.escape(name)}[^"]*"></script>', lambda m: f"<script>\n{read(name)}\n</script>", html)
        if k != 1:
            sys.exit(f"expected one <script src=\"{name}\"> tag")

    # The help overlay and its watchdog exist to explain a page that could
    # not fetch its parts; this one fetches nothing.
    html = re.sub(r'\s*<div id="deck-help" hidden>.*?</div>', "", html, count=1, flags=re.S)
    html = re.sub(r'\s*<!-- A classic script: it still runs.*?</script>', "", html, count=1, flags=re.S)

    # The loader: the module script that picks a reveal.js location and
    # imports it becomes reveal.js itself, its plugins, and the deck setup.
    m = re.search(r'<script type="module">(.*?)</script>', html, flags=re.S)
    if not m:
        sys.exit("loader script not found")
    loader = m.group(1)
    setup_start = loader.index("// BIRD configuration")
    setup = loader[setup_start:]
    setup = setup.replace("await deck.initialize().catch(fail(\"reveal.js failed to start\"));", "deck.initialize().then(() => {")
    setup = setup.replace("plugins: [Markdown, Highlight, Notes],", "plugins: [RevealMarkdown, RevealHighlight, RevealNotes],")
    setup = setup.rstrip() + "\n            });\n"
    libs = "\n".join(read("reveal.js", "dist", p) for p in ["reveal.js", "plugin/markdown.js", "plugin/highlight.js", "plugin/notes.js"])
    html = html[: m.start()] + f"<script>\n{libs}\n</script>\n        <script>\n{setup}        </script>" + html[m.end():]
    if "await " in setup or "import(" in setup:
        sys.exit("loader still contains module-only code")

    html = html.replace("reveal.js is loaded from ./reveal.js/dist if present", "Built by build.py from index.html: everything is inlined. reveal.js was loaded from ./reveal.js/dist if present")

    os.makedirs(os.path.dirname(OUT), exist_ok=True)
    with open(OUT, "w", encoding="utf-8") as f:
        f.write(html)
    print(f"wrote {os.path.relpath(OUT)} ({os.path.getsize(OUT) // 1024} KB, {n} sections)")


if __name__ == "__main__":
    main()