#!/usr/bin/env python3
"""Checks a built site (docs/milestones/W1.md): what the pages promise, kept.

Usage: site/tools/check_site.py <built site folder>

- No page loads anything from another origin: no script, stylesheet, image, font, frame or preload
  from elsewhere (links a visitor follows are fine).
- Every page has a title, a description and a language, and every image has an alt attribute.
- Every file a page references on this site exists.
- Every link to another page of the site lands on a page that exists, and so does the #fragment it names.
"""
import html.parser
import os
import re
import sys
import urllib.parse

ROOT = sys.argv[1] if len(sys.argv) > 1 else "public"
HERE = os.path.dirname(os.path.abspath(__file__))
BASE = re.search(r'base_url\s*=\s*"([^"]+)"', open(os.path.join(HERE, "..", "config.toml")).read()).group(1)
HOST = urllib.parse.urlparse(BASE).netloc


class Page(html.parser.HTMLParser):
    def __init__(self):
        super().__init__()
        self.title = False
        self.has_title = False
        self.has_description = False
        self.lang = None
        self.loads = []  # (tag, url) of everything the page fetches by itself
        self.images_without_alt = 0
        self.links = []  # href of every <a>
        self.ids = set()  # every id and name: what a #fragment can name

    def handle_starttag(self, tag, attrs):
        a = dict(attrs)
        for key in ("id", "name"):
            if a.get(key):
                self.ids.add(a[key])
        if tag == "a" and a.get("href"):
            self.links.append(a["href"])
        if tag == "html":
            self.lang = a.get("lang")
        if tag == "title":
            self.title = True
        if tag == "meta" and a.get("name") == "description" and a.get("content"):
            self.has_description = True
        if tag in ("script", "img", "iframe", "frame", "embed", "source", "video", "audio") and a.get("src"):
            self.loads.append((tag, a["src"]))
        if tag == "link" and a.get("href") and a.get("rel", "") in ("stylesheet", "preload", "icon", "modulepreload", "prefetch"):
            self.loads.append(("link " + a["rel"], a["href"]))
        if tag == "img" and "alt" not in a:
            self.images_without_alt += 1

    def handle_data(self, data):
        if self.title and data.strip():
            self.has_title = True

    def handle_endtag(self, tag):
        if tag == "title":
            self.title = False


problems = []
pages = 0
parsed = {}  # path of a page, from the site's root -> its Page
for folder, _, files in os.walk(ROOT):
    for name in files:
        if not name.endswith(".html"):
            continue
        path = os.path.join(folder, name)
        shown = os.path.relpath(path, ROOT)
        p = Page()
        p.feed(open(path, encoding="utf-8").read())
        pages += 1
        parsed["/" + shown.replace(os.sep, "/")] = (p, folder)
        if not p.has_title: problems.append(f"{shown}: no title")
        if not p.has_description: problems.append(f"{shown}: no description")
        if not p.lang: problems.append(f"{shown}: no language")
        if p.images_without_alt: problems.append(f"{shown}: {p.images_without_alt} image(s) without alt")
        for tag, url in p.loads:
            u = urllib.parse.urlparse(url)
            if u.netloc and u.netloc != HOST:
                problems.append(f"{shown}: {tag} loads {url} from another origin")
            elif not u.netloc and not u.scheme:
                target = os.path.join(ROOT, u.path.lstrip("/")) if u.path.startswith("/") else os.path.join(folder, u.path)
                if u.path and not os.path.exists(target):
                    problems.append(f"{shown}: {tag} {url} does not exist")
            elif u.netloc == HOST:
                target = os.path.join(ROOT, u.path.lstrip("/"))
                if not os.path.exists(target):
                    problems.append(f"{shown}: {tag} {url} does not exist")

def page_of(url_path):
    """The built page a path of the site names: /guide/ is /guide/index.html."""
    if url_path.endswith("/"):
        return url_path + "index.html"
    if os.path.isdir(os.path.join(ROOT, url_path.lstrip("/"))):
        return url_path + "/index.html"
    return url_path


for shown_path, (p, folder) in parsed.items():
    for href in p.links:
        u = urllib.parse.urlparse(href)
        if u.scheme in ("mailto", "tel") or (u.netloc and u.netloc != HOST):
            continue
        if not u.path:  # "#fragment": this page
            target = shown_path
        elif u.path.startswith("/"):
            target = page_of(urllib.parse.unquote(u.path))
        else:
            target = page_of(os.path.normpath(os.path.join(os.path.dirname(shown_path), urllib.parse.unquote(u.path))).replace(os.sep, "/"))
        if not os.path.exists(os.path.join(ROOT, target.lstrip("/"))):
            problems.append(f"{shown_path.lstrip('/')}: link {href} goes nowhere")
        elif u.fragment and target in parsed and u.fragment not in parsed[target][0].ids:
            problems.append(f"{shown_path.lstrip('/')}: link {href}: no #{u.fragment} on that page")

if not pages:
    problems.append(f"no pages found in {ROOT}")
for p in problems:
    print("site check:", p)
print(f"site check: {pages} pages, {len(problems)} problem(s)")
sys.exit(1 if problems else 0)