"""Manifest discovery helpers."""

from __future__ import annotations

from dataclasses import dataclass
from typing import Optional
from urllib.parse import urljoin, urlparse

from bs4 import BeautifulSoup

from ..models import Manifest


LINK_REL = "agent-permissions"
DEFAULT_WELL_KNOWN_PATH = "/.well-known/agent-permissions.json"


@dataclass
class ManifestDiscoveryResult:
    manifest_url: Optional[str]
    method: str
    base_url: Optional[str]
    details: dict
    manifest: Optional[Manifest] = None

    def found(self) -> bool:
        return self.manifest_url is not None


def _sanitize_base(url: str) -> str:
    parsed = urlparse(url)
    if not parsed.scheme or not parsed.netloc:
        raise ValueError(f"URL must include scheme and host: {url}")
    return f"{parsed.scheme}://{parsed.netloc}"


def find_manifest_in_html(html: str, base_url: Optional[str] = None) -> ManifestDiscoveryResult:
    """Search HTML markup for a link tag referencing the manifest."""

    soup = BeautifulSoup(html, "html.parser")
    link = soup.find("link", rel=lambda value: value and LINK_REL in value.split())
    if link and link.has_attr("href"):
        href = link["href"]
        manifest_url = urljoin(base_url, href) if base_url else href
        return ManifestDiscoveryResult(
            manifest_url=manifest_url,
            method="html_link_tag",
            base_url=base_url,
            details={"href": href},
        )
    return ManifestDiscoveryResult(
        manifest_url=None,
        method="html_link_tag",
        base_url=base_url,
        details={"reason": "not_found"},
    )


def fallback_well_known(url: str) -> ManifestDiscoveryResult:
    """Return the default /.well-known manifest location for a URL."""

    base = _sanitize_base(url)
    manifest_url = urljoin(base, DEFAULT_WELL_KNOWN_PATH)
    return ManifestDiscoveryResult(
        manifest_url=manifest_url,
        method="default_well_known",
        base_url=base,
        details={},
    )