"""The Android OTA feed, read from this repository's Gitea Actions artifacts.

The Gitea repository is private, so the phone cannot read Actions artifacts
itself. This module is the only place that touches the Gitea token: it finds the
newest successful build from the configured branch, reads the small metadata
artifact, and pulls the APK out of the matching artifact zip on demand.

Nothing here trusts the metadata blindly. Every field falls back to what the
Gitea run itself reports, so an older artifact that predates `update.json` still
produces a usable answer instead of a 500.
"""

from __future__ import annotations

import json
import logging
import shutil
import tempfile
import threading
import time
import zipfile
from dataclasses import dataclass, replace
from pathlib import Path
from typing import Any

import httpx

from app.config import EnvSettings, env_settings

log = logging.getLogger(__name__)

METADATA_ARTIFACT = "kadence-update-metadata"
APK_ARTIFACT = "kadence-release-apk"

_METADATA_TTL_SECONDS = 60.0
_HTTP_TIMEOUT = 30.0
_DOWNLOAD_TIMEOUT = 120.0
_MAX_METADATA_BYTES = 1_000_000
_CACHE_DIR = Path(tempfile.gettempdir()) / "kadence-updates"


class UpdateUnavailable(RuntimeError):
    """The feed cannot be built right now."""


class UpdateNotConfigured(UpdateUnavailable):
    """No Gitea token was supplied, so there is nothing to read."""


class UpdateNotFound(UpdateUnavailable):
    """There is no successful artifact for the configured branch."""


@dataclass(frozen=True, slots=True)
class ResolvedUpdate:
    metadata: dict[str, Any]
    apk_artifact_id: int


@dataclass(frozen=True, slots=True)
class Artifact:
    id: int
    name: str
    created_at: str
    size_bytes: int
    expired: bool
    run_id: int
    run_number: int
    branch: str
    commit: str
    conclusion: str


_lock = threading.Lock()
_resolved_cache: tuple[float, ResolvedUpdate] | None = None
_apk_cache: dict[int, Path] = {}


def reset_cache() -> None:
    """Drop the in-process caches. Tests use this between Gitea responses."""
    global _resolved_cache
    with _lock:
        _resolved_cache = None
        _apk_cache.clear()


# ---- Gitea reads -----------------------------------------------------------


def _settings() -> EnvSettings:
    settings = env_settings()
    if not settings.gitea_token:
        raise UpdateNotConfigured(
            "Android updates are not configured: set GITEA_TOKEN on the backend."
        )
    if not settings.gitea_repo or "/" not in settings.gitea_repo:
        raise UpdateNotConfigured("Android updates need GITEA_REPO as owner/repository.")
    return settings


def _client(settings: EnvSettings, *, timeout: float = _HTTP_TIMEOUT) -> httpx.Client:
    return httpx.Client(
        base_url=settings.gitea_url.rstrip("/"),
        headers={
            "Authorization": f"token {settings.gitea_token}",
            "Accept": "application/json",
        },
        timeout=timeout,
        follow_redirects=True,
    )


def _api(settings: EnvSettings, path: str) -> str:
    return f"/api/v1/repos/{settings.gitea_repo}{path}"


def _artifact(raw: Any) -> Artifact | None:
    if not isinstance(raw, dict):
        return None
    run = raw.get("workflow_run")
    run = run if isinstance(run, dict) else {}
    try:
        artifact_id = int(raw.get("id") or 0)
    except (TypeError, ValueError):
        return None
    if artifact_id <= 0:
        return None
    return Artifact(
        id=artifact_id,
        name=str(raw.get("name") or ""),
        created_at=str(raw.get("created_at") or ""),
        size_bytes=int(raw.get("size_in_bytes") or 0),
        expired=bool(raw.get("expired")),
        run_id=int(run.get("id") or 0),
        run_number=int(run.get("run_number") or 0),
        branch=str(run.get("head_branch") or ""),
        commit=str(run.get("head_sha") or ""),
        conclusion=str(run.get("conclusion") or ""),
    )


def _run(client: httpx.Client, settings: EnvSettings, run_id: int) -> dict[str, Any]:
    try:
        response = client.get(_api(settings, f"/actions/runs/{run_id}"))
        response.raise_for_status()
        payload = response.json()
    except (httpx.HTTPError, ValueError) as exc:
        raise UpdateUnavailable(f"Could not read Gitea run {run_id}: {exc}") from exc
    return payload if isinstance(payload, dict) else {}


def _with_run(
    client: httpx.Client,
    settings: EnvSettings,
    artifact: Artifact,
    runs: dict[int, dict[str, Any]],
) -> Artifact:
    """Gitea's artifact list can omit the run's branch, number and conclusion."""
    if artifact.run_number and artifact.branch and artifact.conclusion:
        return artifact
    if not artifact.run_id:
        return artifact
    run = runs.get(artifact.run_id)
    if run is None:
        run = _run(client, settings, artifact.run_id)
        runs[artifact.run_id] = run
    return replace(
        artifact,
        run_number=int(run.get("run_number") or artifact.run_number),
        branch=str(run.get("head_branch") or artifact.branch),
        commit=str(run.get("head_sha") or artifact.commit),
        conclusion=str(run.get("conclusion") or artifact.conclusion),
    )


def _list_artifacts(
    client: httpx.Client,
    settings: EnvSettings,
    name: str,
    runs: dict[int, dict[str, Any]] | None = None,
) -> list[Artifact]:
    try:
        response = client.get(_api(settings, "/actions/artifacts"), params={"name": name})
        response.raise_for_status()
        payload = response.json()
    except (httpx.HTTPError, ValueError) as exc:
        raise UpdateUnavailable(f"Could not read Gitea artifacts: {exc}") from exc

    entries = payload.get("artifacts") if isinstance(payload, dict) else None
    if not isinstance(entries, list):
        return []
    artifacts = [artifact for raw in entries if (artifact := _artifact(raw)) is not None]
    run_cache = runs if runs is not None else {}
    return [_with_run(client, settings, artifact, run_cache) for artifact in artifacts]


def _successful(artifacts: list[Artifact], branch: str) -> list[Artifact]:
    """Newest first, and only successful builds from the requested branch."""
    usable = [
        artifact
        for artifact in artifacts
        if not artifact.expired
        and artifact.conclusion == "success"
        and artifact.branch == branch
    ]
    # `run_number` is the monotonic number Android uses as `versionCode`. The
    # created_at string is the tie-breaker for older Gitea runs that report 0.
    return sorted(usable, key=lambda item: (item.run_number, item.created_at), reverse=True)


def _download_artifact(client: httpx.Client, settings: EnvSettings, artifact: Artifact) -> Path:
    """Download one artifact zip to a temporary file and return its path."""
    _CACHE_DIR.mkdir(parents=True, exist_ok=True)
    target = _CACHE_DIR / f"artifact-{artifact.id}.zip"
    if target.is_file() and target.stat().st_size > 0:
        return target

    temporary = target.with_suffix(".zip.part")
    try:
        with client.stream(
            "GET",
            _api(settings, f"/actions/artifacts/{artifact.id}/zip"),
            timeout=_DOWNLOAD_TIMEOUT,
        ) as response:
            response.raise_for_status()
            with temporary.open("wb") as handle:
                for chunk in response.iter_bytes():
                    handle.write(chunk)
        if temporary.stat().st_size == 0:
            raise UpdateUnavailable("Gitea returned an empty artifact archive.")
        temporary.replace(target)
    except (httpx.HTTPError, OSError) as exc:
        temporary.unlink(missing_ok=True)
        raise UpdateUnavailable(f"Could not download the Gitea artifact: {exc}") from exc
    return target


def _member(zf: zipfile.ZipFile, basename: str) -> zipfile.ZipInfo | None:
    for info in zf.infolist():
        if not info.is_dir() and Path(info.filename).name == basename:
            return info
    return None


def _read_metadata(client: httpx.Client, settings: EnvSettings, artifact: Artifact) -> dict[str, Any]:
    archive = _download_artifact(client, settings, artifact)
    try:
        with zipfile.ZipFile(archive) as zf:
            info = _member(zf, "update.json")
            if info is None:
                raise UpdateUnavailable("The update metadata artifact has no update.json.")
            if info.file_size > _MAX_METADATA_BYTES:
                raise UpdateUnavailable("The update metadata artifact is unexpectedly large.")
            raw = json.loads(zf.read(info).decode("utf-8"))
    except (zipfile.BadZipFile, OSError, UnicodeDecodeError, ValueError) as exc:
        raise UpdateUnavailable(f"Could not read the update metadata: {exc}") from exc
    return raw if isinstance(raw, dict) else {}


def _int(value: Any, fallback: int = 0) -> int:
    try:
        return int(value)
    except (TypeError, ValueError):
        return fallback


def _metadata_from_artifact(raw: dict[str, Any], artifact: Artifact) -> dict[str, Any]:
    run_number = artifact.run_number
    return {
        "version_code": _int(raw.get("version_code"), run_number),
        "version_name": str(
            raw.get("version_name") or f"0.1.0-master.{run_number or artifact.run_id}"
        ),
        "commit": str(raw.get("commit") or artifact.commit),
        "built_at": str(raw.get("built_at") or artifact.created_at),
        "size_bytes": _int(raw.get("size_bytes"), artifact.size_bytes),
        "sha256": str(raw.get("sha256") or ""),
        "signer_sha256": str(raw.get("signer_sha256") or ""),
        "run_number": run_number,
    }


def _derive_metadata(artifact: Artifact) -> dict[str, Any]:
    """For artifacts built before the metadata artifact existed."""
    return _metadata_from_artifact({}, artifact)


def _apk_for_run(artifacts: list[Artifact], update: Artifact) -> Artifact | None:
    for artifact in artifacts:
        if artifact.run_id and artifact.run_id == update.run_id and not artifact.expired:
            return artifact
    # Defensive fallback for an instance that omits workflow_run.id on an
    # artifact but keeps the run number.
    if update.run_number:
        for artifact in artifacts:
            if artifact.run_number == update.run_number and not artifact.expired:
                return artifact
    return None


def _resolve(settings: EnvSettings) -> ResolvedUpdate:
    global _resolved_cache

    now = time.monotonic()
    with _lock:
        cached = _resolved_cache
    if cached is not None and now - cached[0] < _METADATA_TTL_SECONDS:
        return cached[1]

    runs: dict[int, dict[str, Any]] = {}
    with _client(settings) as client:
        metadata_artifacts = _successful(
            _list_artifacts(client, settings, METADATA_ARTIFACT, runs),
            settings.gitea_update_branch,
        )
        apk_artifacts = _list_artifacts(client, settings, APK_ARTIFACT, runs)
        usable_apk = _successful(apk_artifacts, settings.gitea_update_branch)

        resolved: ResolvedUpdate | None = None
        for artifact in metadata_artifacts:
            apk = _apk_for_run(usable_apk, artifact)
            if apk is None:
                continue
            resolved = ResolvedUpdate(
                metadata=_metadata_from_artifact(
                    _read_metadata(client, settings, artifact), artifact
                ),
                apk_artifact_id=apk.id,
            )
            break

        # Before the first build after this feature landed there is no metadata
        # artifact. The run number is the versionCode, so the newest APK
        # artifact is still enough to offer an update.
        if resolved is None and usable_apk:
            newest = usable_apk[0]
            resolved = ResolvedUpdate(
                metadata=_derive_metadata(newest),
                apk_artifact_id=newest.id,
            )

    if resolved is None:
        raise UpdateNotFound(
            f"No successful {settings.gitea_update_branch} build with an APK was found."
        )

    with _lock:
        _resolved_cache = (time.monotonic(), resolved)
    return resolved


def _apk_file(client: httpx.Client, settings: EnvSettings, artifact_id: int) -> Path:
    with _lock:
        cached = _apk_cache.get(artifact_id)
    if cached is not None and cached.is_file() and cached.stat().st_size > 0:
        return cached

    # The artifact list does not carry the APK's own record here, so fetch it by
    # id. The id is enough for both the zip URL and the cache key.
    artifact = Artifact(
        id=artifact_id,
        name=APK_ARTIFACT,
        created_at="",
        size_bytes=0,
        expired=False,
        run_id=0,
        run_number=0,
        branch="",
        commit="",
        conclusion="success",
    )
    archive = _download_artifact(client, settings, artifact)
    _CACHE_DIR.mkdir(parents=True, exist_ok=True)
    target = _CACHE_DIR / f"kadence-{artifact_id}.apk"
    temporary = target.with_suffix(".apk.part")
    try:
        with zipfile.ZipFile(archive) as zf:
            info = _member(zf, "app-release.apk")
            if info is None:
                raise UpdateUnavailable("The APK artifact has no app-release.apk.")
            with zf.open(info) as source, temporary.open("wb") as destination:
                shutil.copyfileobj(source, destination)
        if temporary.stat().st_size == 0:
            raise UpdateUnavailable("The APK inside the artifact is empty.")
        temporary.replace(target)
    except (zipfile.BadZipFile, OSError) as exc:
        temporary.unlink(missing_ok=True)
        raise UpdateUnavailable(f"Could not extract the APK: {exc}") from exc
    except UpdateUnavailable:
        temporary.unlink(missing_ok=True)
        raise

    with _lock:
        _apk_cache[artifact_id] = target
    return target


# ---- the public feed -------------------------------------------------------


def latest_android() -> dict[str, Any]:
    """The newest successful build, as JSON-ready metadata."""
    settings = _settings()
    return _resolve(settings).metadata


def android_apk() -> tuple[Path, dict[str, Any]]:
    """The APK for the newest build, along with its metadata."""
    settings = _settings()
    resolved = _resolve(settings)
    with _client(settings) as client:
        path = _apk_file(client, settings, resolved.apk_artifact_id)
    return path, resolved.metadata