from __future__ import annotations

import os
import re
import urllib.error
import urllib.request
from datetime import date, datetime, timezone
from pathlib import Path
from typing import Any

import yaml
from jsonschema import Draft202012Validator

from reuse_surface.registry import ROOT

MANIFEST_PATH = ROOT / "registry" / "federation" / "sources.yaml"
SCHEMA_PATH = ROOT / "schemas" / "federation.schema.yaml"
FEDERATED_INDEX_PATH = ROOT / "registry" / "indexes" / "federated.yaml"
CACHE_DIR = ROOT / "registry" / "federation" / "cache"
DEFAULT_CACHE_TTL_SECONDS = 86400
USER_AGENT = "reuse-surface/0.1 federation-compose"


def _expand_path(index_path: str) -> Path:
    return Path(index_path).expanduser()


def load_federation_manifest(path: Path | None = None) -> dict[str, Any]:
    manifest_path = path or MANIFEST_PATH
    with manifest_path.open(encoding="utf-8") as handle:
        manifest = yaml.safe_load(handle)
    schema = yaml.safe_load(SCHEMA_PATH.read_text(encoding="utf-8"))
    validator = Draft202012Validator(schema)
    errors = sorted(validator.iter_errors(manifest), key=lambda err: err.path)
    if errors:
        messages = "; ".join(error.message for error in errors)
        raise ValueError(f"invalid federation manifest: {messages}")
    return manifest


def _resolve_index_path(index_value: str) -> Path:
    path = _expand_path(index_value)
    if not path.is_absolute():
        path = (ROOT / path).resolve()
    return path


def _safe_repo_slug(repo: str) -> str:
    return re.sub(r"[^\w.-]", "_", repo)


def _path_label(path: Path) -> str:
    try:
        return str(path.relative_to(ROOT))
    except ValueError:
        return str(path)


def _cache_root(cache_dir: Path | None = None) -> Path:
    return cache_dir or CACHE_DIR


def _cache_paths(repo: str, cache_dir: Path | None = None) -> tuple[Path, Path]:
    root = _cache_root(cache_dir)
    slug = _safe_repo_slug(repo)
    return root / f"{slug}.yaml", root / f"{slug}.meta.yaml"


def _read_cache_meta(meta_path: Path) -> dict[str, Any] | None:
    if not meta_path.exists():
        return None
    data = yaml.safe_load(meta_path.read_text(encoding="utf-8"))
    return data if isinstance(data, dict) else None


def _cache_is_fresh(meta: dict[str, Any], ttl_seconds: int) -> bool:
    if ttl_seconds <= 0:
        return False
    fetched_at = meta.get("fetched_at")
    if not fetched_at:
        return False
    fetched = datetime.fromisoformat(str(fetched_at))
    if fetched.tzinfo is None:
        fetched = fetched.replace(tzinfo=timezone.utc)
    age = (datetime.now(timezone.utc) - fetched).total_seconds()
    return age < ttl_seconds


def _auth_headers(source: dict[str, Any]) -> dict[str, str]:
    auth_env = source.get("auth_env")
    if not auth_env:
        return {}
    token = os.environ.get(auth_env)
    if not token:
        raise ValueError(
            f"auth env {auth_env} is not set for remote source {source['repo']}"
        )
    header_name = source.get("auth_header", "Authorization")
    if header_name.lower() == "authorization" and not token.lower().startswith(
        ("bearer ", "basic ")
    ):
        token = f"Bearer {token}"
    return {header_name: token}


def fetch_remote_index_text(url: str, source: dict[str, Any]) -> str:
    headers = {"User-Agent": USER_AGENT, **_auth_headers(source)}
    request = urllib.request.Request(url, headers=headers)
    try:
        with urllib.request.urlopen(request, timeout=30) as response:
            return response.read().decode("utf-8")
    except urllib.error.HTTPError as exc:
        raise ConnectionError(
            f"HTTP {exc.code} fetching {url} for {source['repo']}"
        ) from exc
    except urllib.error.URLError as exc:
        raise ConnectionError(
            f"failed to fetch {url} for {source['repo']}: {exc.reason}"
        ) from exc


def _write_remote_cache(
    repo: str, url: str, content: str, cache_dir: Path | None = None
) -> Path:
    root = _cache_root(cache_dir)
    root.mkdir(parents=True, exist_ok=True)
    index_path, meta_path = _cache_paths(repo, cache_dir)
    index_path.write_text(content, encoding="utf-8")
    meta = {
        "fetched_at": datetime.now(timezone.utc).isoformat(),
        "url": url,
        "repo": repo,
    }
    meta_path.write_text(yaml.safe_dump(meta, sort_keys=False), encoding="utf-8")
    return index_path


def resolve_source_index_path(
    source: dict[str, Any],
    *,
    refresh: bool = False,
    cache_dir: Path | None = None,
) -> tuple[Path | None, list[str]]:
    warnings: list[str] = []
    if "index" in source:
        path = _resolve_index_path(source["index"])
        if not path.exists():
            message = f"missing index for {source['repo']}: {path}"
            if source.get("required", False):
                raise FileNotFoundError(message)
            warnings.append(message)
            return None, warnings
        return path, warnings

    url = source["url"]
    ttl_seconds = int(source.get("cache_ttl_seconds", DEFAULT_CACHE_TTL_SECONDS))
    index_path, meta_path = _cache_paths(source["repo"], cache_dir)
    meta = _read_cache_meta(meta_path)
    use_cache = (
        index_path.exists()
        and meta is not None
        and meta.get("url") == url
        and _cache_is_fresh(meta, ttl_seconds)
        and not refresh
    )
    if use_cache:
        return index_path, warnings

    try:
        content = fetch_remote_index_text(url, source)
    except (ConnectionError, ValueError) as exc:
        if index_path.exists():
            warnings.append(
                f"remote fetch failed for {source['repo']}, using stale cache: {exc}"
            )
            return index_path, warnings
        message = f"remote index unavailable for {source['repo']}: {exc}"
        if source.get("required", False):
            raise FileNotFoundError(message) from exc
        warnings.append(message)
        return None, warnings

    return _write_remote_cache(source["repo"], url, content, cache_dir), warnings


def compose_federated_index(
    manifest: dict[str, Any] | None = None,
    *,
    refresh: bool = False,
    cache_dir: Path | None = None,
) -> tuple[dict[str, Any], list[str]]:
    manifest = manifest or load_federation_manifest()
    warnings: list[str] = []
    merged: list[dict[str, Any]] = []
    seen_ids: dict[str, str] = {}
    source_summaries: list[dict[str, Any]] = []

    for source in manifest["sources"]:
        if not source.get("enabled", False):
            continue
        index_path, source_warnings = resolve_source_index_path(
            source, refresh=refresh, cache_dir=cache_dir
        )
        warnings.extend(source_warnings)
        if index_path is None:
            continue
        with index_path.open(encoding="utf-8") as handle:
            index_data = yaml.safe_load(handle)
        count = 0
        for item in index_data.get("capabilities", []):
            cap_id = item["id"]
            if cap_id in seen_ids:
                warnings.append(
                    f"duplicate id {cap_id}: {seen_ids[cap_id]} and {source['repo']}"
                )
            else:
                seen_ids[cap_id] = source["repo"]
            federated_item = dict(item)
            federated_item["source_repo"] = source["repo"]
            if "url" in source:
                federated_item["source_url"] = source["url"]
                federated_item["source_index"] = _path_label(index_path)
            else:
                federated_item["source_index"] = source["index"]
            merged.append(federated_item)
            count += 1
        summary: dict[str, Any] = {
            "repo": source["repo"],
            "count": count,
        }
        if "url" in source:
            summary["url"] = source["url"]
            summary["cache"] = _path_label(index_path)
        else:
            summary["index"] = source["index"]
        source_summaries.append(summary)

    federated = {
        "version": manifest.get("version", 1),
        "updated": date.today().isoformat(),
        "domain": manifest.get("domain"),
        "collision_policy": manifest.get("collision_policy", "warn"),
        "sources": source_summaries,
        "capabilities": sorted(merged, key=lambda item: item["id"]),
    }
    return federated, warnings


def write_federated_index(
    output_path: Path | None = None,
    manifest: dict[str, Any] | None = None,
    *,
    refresh: bool = False,
) -> tuple[Path, list[str]]:
    federated, warnings = compose_federated_index(manifest, refresh=refresh)
    target = output_path or FEDERATED_INDEX_PATH
    target.parent.mkdir(parents=True, exist_ok=True)
    header = (
        "# Composed federated capability index. Regenerate with:\n"
        "# reuse-surface federation compose\n"
    )
    target.write_text(
        header + yaml.safe_dump(federated, sort_keys=False),
        encoding="utf-8",
    )
    return target, warnings