#!/usr/bin/env python3
"""Fail when the static site contains broken or non-portable local references."""

from html.parser import HTMLParser
from pathlib import Path
from urllib.parse import unquote, urlsplit

ROOT = Path(__file__).resolve().parents[1]
SKIP_PREFIXES = ("#", "data:", "mailto:", "tel:", "javascript:")


class PageParser(HTMLParser):
    def __init__(self):
        super().__init__()
        self.references = []
        self.ids = set()
        self.has_viewport = False
        self.has_csp = False

    def handle_starttag(self, tag, attrs):
        values = dict(attrs)
        element_id = values.get("id")
        if element_id:
            self.ids.add(element_id)
        if tag == "meta" and values.get("name", "").lower() == "viewport":
            self.has_viewport = True
        if tag == "meta" and values.get("http-equiv", "").lower() == "content-security-policy":
            self.has_csp = True
        for attribute in ("href", "src", "action"):
            value = values.get(attribute)
            if value:
                self.references.append((tag, attribute, value))


def parse_page(path):
    parser = PageParser()
    parser.feed(path.read_text(encoding="utf-8"))
    return parser


def main():
    pages = sorted(ROOT.glob("*.html"))
    parsed = {page.resolve(): parse_page(page) for page in pages}
    errors = []

    if not (ROOT / "index.html").is_file():
        errors.append("missing GitHub Pages entry point: index.html")

    for page in pages:
        parser = parsed[page.resolve()]
        if not parser.has_viewport:
            errors.append(f"{page.name}: missing viewport metadata")
        if not parser.has_csp:
            errors.append(f"{page.name}: missing Content Security Policy")

        for tag, attribute, raw_value in parser.references:
            value = raw_value.strip()
            if not value or value.startswith(SKIP_PREFIXES):
                continue

            url = urlsplit(value)
            if url.scheme or url.netloc:
                if attribute != "href":
                    errors.append(f"{page.name}: remote dependency in {attribute}: {value}")
                continue
            if url.path.startswith("/"):
                errors.append(f"{page.name}: root-absolute path breaks project Pages: {value}")
                continue

            target = (page.parent / unquote(url.path or page.name)).resolve()
            try:
                target.relative_to(ROOT)
            except ValueError:
                errors.append(f"{page.name}: reference leaves repository: {value}")
                continue
            if not target.exists():
                errors.append(f"{page.name}: missing {tag} {attribute} target: {value}")
                continue

            if url.fragment and target.suffix.lower() == ".html":
                target_parser = parsed.get(target)
                if target_parser is None:
                    target_parser = parse_page(target)
                    parsed[target] = target_parser
                if unquote(url.fragment) not in target_parser.ids:
                    errors.append(f"{page.name}: missing anchor target: {value}")

    if errors:
        print("Site validation failed:")
        for error in errors:
            print(f"- {error}")
        raise SystemExit(1)

    print(f"Site validation passed: {len(pages)} HTML pages checked.")


if __name__ == "__main__":
    main()