"""Registry orchestrator (ADR-0002 + ADR-0003 + ADR-0004).

The :class:`Registry` is the library-shaped entry point. It combines
``identity`` + ``manifest`` + ``events`` + ``dataplane`` into the six
operations the HTTP API and CLI both consume:

* ``create_package``
* ``ingest_file``
* ``finalize_package``
* ``get_manifest_bytes`` (canonical CBOR or JCS projection)
* ``get_file``
* ``tail_events``

Every mutating operation writes one event and updates the materialised
views inside the same database transaction, so the event log remains the
source of truth (ADR-0002).
"""

from __future__ import annotations

import uuid
from collections.abc import AsyncIterator, Sequence
from datetime import UTC, datetime
from typing import Any
from uuid import UUID

import cbor2
from sqlalchemy import select, text
from sqlalchemy.ext.asyncio import AsyncEngine

from artifactstore.dataplane.spi import DataPlane
from artifactstore.db.schema import (
    artifact_files,
    artifact_packages,
    retention_classes,
    retention_state,
    storage_locations,
)
from artifactstore.db.schema import (
    events as events_t,
)
from artifactstore.events import RegistryViewWriter, make_event, tail, write
from artifactstore.events.model import Event
from artifactstore.identity import ContentAddress
from artifactstore.manifest import (
    MANIFEST_VERSION,
    FileEntry,
    Manifest,
    Package,
    Provenance,
    RetentionSummary,
)
from artifactstore.manifest import (
    StorageReceipt as ManifestStorageReceipt,
)
from artifactstore.manifest import (
    encode as manifest_encode,
)
from artifactstore.manifest import (
    manifest_digest as compute_manifest_digest,
)
from artifactstore.manifest.codec import decode as manifest_decode
from artifactstore.manifest.projection import jcs_projection
from artifactstore.storage.spi import BackendStatus

__all__ = ["Registry"]


class PackageNotFoundError(KeyError):
    """Raised when a package id has no row in artifact_packages."""


class FileNotFoundError(KeyError):
    """Raised when a file id has no row in artifact_files / storage_locations."""


class IllegalPackageStateError(ValueError):
    """Raised when an operation is rejected because of package status."""


class DuplicateRelativePathError(ValueError):
    """Raised when ingest_file would create a duplicate ``relative_path`` in a package."""


class Registry:
    """Library-shaped orchestrator over events, dataplane, and views."""

    def __init__(
        self,
        engine: AsyncEngine,
        dataplane: DataPlane,
        view_writer: RegistryViewWriter | None = None,
    ) -> None:
        self._engine = engine
        self._dataplane = dataplane
        self._view_writer = view_writer or RegistryViewWriter()

    # ---- mutating operations ------------------------------------------------

    async def create_package(
        self,
        *,
        name: str,
        producer: str,
        subject: str,
        retention_class: str,
        actor: str,
        metadata: dict[str, Any] | None = None,
    ) -> UUID:
        """Create a new package; returns its ``UUID``."""
        await self._validate_retention_class(retention_class)
        package_id = uuid.uuid4()
        payload = cbor2.dumps(
            {
                "name": name,
                "producer": producer,
                "subject": subject,
                "retention_class": retention_class,
                "metadata": metadata or {},
            },
            canonical=True,
        )
        event = make_event(
            event_type="v1.package.created",
            subject_kind="package",
            subject_id=package_id,
            actor=actor,
            payload=payload,
        )
        async with self._engine.begin() as conn:
            written = await write(conn, event)
            await self._view_writer.apply(conn, written)
        return package_id

    async def ingest_file(
        self,
        package_id: UUID,
        *,
        relative_path: str,
        media_type: str,
        stream: AsyncIterator[bytes],
        actor: str,
    ) -> UUID:
        """Stream a file into the package; returns the new file id."""
        async with self._engine.connect() as conn:
            pkg_row = (
                await conn.execute(
                    select(artifact_packages).where(artifact_packages.c.id == package_id)
                )
            ).first()
            if pkg_row is None:
                raise PackageNotFoundError(f"package not found: {package_id}")
            if pkg_row.status != "created":
                raise IllegalPackageStateError(
                    f"package {package_id} cannot accept files (status={pkg_row.status})"
                )
            existing = (
                await conn.execute(
                    select(artifact_files).where(
                        artifact_files.c.package_id == package_id,
                        artifact_files.c.relative_path == relative_path,
                    )
                )
            ).first()
            if existing is not None:
                raise DuplicateRelativePathError(
                    f"relative_path {relative_path!r} already exists in package {package_id}"
                )

        ingest = await self._dataplane.ingest_stream(stream)

        file_id = uuid.uuid4()
        storage_location_id = uuid.uuid4()
        payload = cbor2.dumps(
            {
                "file_id": str(file_id),
                "relative_path": relative_path,
                "media_type": media_type,
                "size_bytes": ingest.size_bytes,
                "digest_algorithm": ingest.primary_digest.algorithm,
                "digest_primary_hex": ingest.primary_digest.hex,
                "digest_sha256_hex": ingest.sha256_digest.hex,
                "backend_id": ingest.receipt.backend_id,
                "object_key": ingest.receipt.object_key,
                "storage_location_id": str(storage_location_id),
                "retrieval_tier": "hot",
                "storage_status": "recorded",
            },
            canonical=True,
        )
        event = make_event(
            event_type="v1.file.ingested",
            subject_kind="package",
            subject_id=package_id,
            actor=actor,
            payload=payload,
        )
        async with self._engine.begin() as conn:
            written = await write(conn, event)
            await self._view_writer.apply(conn, written)
        return file_id

    async def finalize_package(self, package_id: UUID, *, actor: str) -> ContentAddress:
        """Finalise a package: build manifest, write it as the
        v1.package.finalized event payload, and update the package's
        terminal state. Returns the manifest's content address."""
        async with self._engine.connect() as conn:
            pkg_row = (
                await conn.execute(
                    select(artifact_packages).where(artifact_packages.c.id == package_id)
                )
            ).first()
            if pkg_row is None:
                raise PackageNotFoundError(f"package not found: {package_id}")
            if pkg_row.status != "created":
                raise IllegalPackageStateError(
                    f"package {package_id} cannot be finalized (status={pkg_row.status})"
                )
            file_rows = (
                await conn.execute(
                    select(artifact_files)
                    .where(artifact_files.c.package_id == package_id)
                    .order_by(artifact_files.c.relative_path)
                )
            ).all()
            file_ids = [r.id for r in file_rows]
            location_rows = (
                (
                    await conn.execute(
                        select(storage_locations)
                        .where(storage_locations.c.artifact_file_id.in_(file_ids))
                        .order_by(storage_locations.c.artifact_file_id)
                    )
                ).all()
                if file_ids
                else []
            )
            retention_row = (
                await conn.execute(
                    select(retention_state).where(retention_state.c.package_id == package_id)
                )
            ).first()

        manifest = _build_manifest(
            pkg_row=pkg_row,
            file_rows=file_rows,
            location_rows=location_rows,
            retention_row=retention_row,
            actor=actor,
        )
        manifest_bytes = manifest_encode(manifest)
        manifest_addr = compute_manifest_digest(manifest)

        event = make_event(
            event_type="v1.package.finalized",
            subject_kind="package",
            subject_id=package_id,
            actor=actor,
            payload=manifest_bytes,
        )
        async with self._engine.begin() as conn:
            written = await write(conn, event)
            await self._view_writer.apply(conn, written)
        return manifest_addr

    # ---- read-only operations ----------------------------------------------

    async def get_manifest_bytes(self, package_id: UUID, *, format: str = "cbor") -> bytes:
        """Return the finalised manifest. ``format`` is ``cbor`` (canonical
        CBOR, the wire form) or ``json`` (the JCS projection)."""
        async with self._engine.connect() as conn:
            row = (
                await conn.execute(
                    select(events_t.c.payload)
                    .where(
                        events_t.c.event_type == "v1.package.finalized",
                        events_t.c.subject_id == package_id,
                    )
                    .order_by(events_t.c.sequence.desc())
                    .limit(1)
                )
            ).first()
        if row is None:
            raise PackageNotFoundError(f"no finalized manifest for package {package_id}")
        payload_bytes: bytes = row.payload
        if format == "cbor":
            return payload_bytes
        if format == "json":
            return jcs_projection(manifest_decode(payload_bytes))
        raise ValueError(f"unknown manifest format: {format!r} (expected 'cbor' or 'json')")

    async def get_file(self, file_id: UUID) -> AsyncIterator[bytes]:
        """Return an async byte iterator for the bytes of a stored file."""
        async with self._engine.connect() as conn:
            row = (
                await conn.execute(
                    select(storage_locations)
                    .where(storage_locations.c.artifact_file_id == file_id)
                    .limit(1)
                )
            ).first()
        if row is None:
            raise FileNotFoundError(f"file not found: {file_id}")
        ca = ContentAddress(row.content_address)
        return await self._dataplane.serve_object(ca)

    def tail_events(
        self,
        *,
        since_sequence: int = 0,
        poll_interval_seconds: float = 0.5,
    ) -> AsyncIterator[Event]:
        """Long-poll the event log; pass-through to :func:`events.tail`."""
        return tail(
            self._engine,
            since_sequence=since_sequence,
            poll_interval_seconds=poll_interval_seconds,
        )

    # ---- health / lifecycle -------------------------------------------------

    async def db_health(self) -> tuple[bool, str]:
        """Probe the database with ``SELECT 1``.

        Returns ``(healthy, detail)``; ``detail`` is "ok" on success and the
        exception message on failure.
        """
        try:
            async with self._engine.connect() as conn:
                await conn.execute(text("SELECT 1"))
        except Exception as exc:
            return False, f"{type(exc).__name__}: {exc}"
        return True, "ok"

    async def backend_health(self) -> BackendStatus:
        """Probe the configured storage backend through the data plane."""
        return await self._dataplane.backend_health()

    async def dispose(self) -> None:
        """Release the engine's connection pool. Idempotent."""
        await self._engine.dispose()

    # ---- internals ----------------------------------------------------------

    async def _validate_retention_class(self, retention_class: str) -> None:
        async with self._engine.connect() as conn:
            row = (
                await conn.execute(
                    select(retention_classes.c.class_id).where(
                        retention_classes.c.class_id == retention_class
                    )
                )
            ).first()
        if row is None:
            raise ValueError(f"unknown retention class: {retention_class!r}")


def _iso(value: datetime | None) -> str | None:
    if value is None:
        return None
    if value.tzinfo is None:
        value = value.replace(tzinfo=UTC)
    return value.isoformat()


def _build_manifest(
    *,
    pkg_row: Any,
    file_rows: Sequence[Any],
    location_rows: Sequence[Any],
    retention_row: Any | None,
    actor: str,
) -> Manifest:
    files_entries = [
        FileEntry(
            id=str(r.id),
            relative_path=r.relative_path,
            media_type=r.media_type,
            size_bytes=r.size_bytes,
            digest_algorithm=r.digest_algorithm,
            digest_primary_hex=r.digest_primary.hex(),
            digest_sha256_hex=r.digest_sha256.hex(),
        )
        for r in file_rows
    ]
    receipts = [
        ManifestStorageReceipt(
            file_id=str(r.artifact_file_id),
            backend_id=r.backend_id,
            content_address=r.content_address,
            retrieval_tier=r.retrieval_tier,
            status=r.status,
        )
        for r in location_rows
    ]
    retention_class = (
        retention_row.effective_class if retention_row is not None else pkg_row.retention_class
    )
    retention_summary = RetentionSummary(
        retention_class=retention_class,
        expires_at=_iso(retention_row.current_expires_at) if retention_row else None,
        active_holds=[],
        last_retention_event_sequence=None,
    )
    finalized_at_iso = datetime.now(UTC).isoformat()
    return Manifest(
        manifest_version=MANIFEST_VERSION,
        package=Package(
            id=str(pkg_row.id),
            name=pkg_row.name,
            producer=pkg_row.producer,
            subject=pkg_row.subject,
            retention_class=pkg_row.retention_class,
            status="finalized",
            created_at=_iso(pkg_row.created_at) or "",
            finalized_at=finalized_at_iso,
            expires_at=_iso(pkg_row.expires_at),
            metadata=dict(pkg_row.metadata) if pkg_row.metadata else {},
            metadata_schema_id=str(pkg_row.metadata_schema_id)
            if pkg_row.metadata_schema_id
            else None,
        ),
        files=files_entries,
        storage_receipts=receipts,
        retention_summary=retention_summary,
        provenance=Provenance(
            source_commits={},
            tool_versions={},
            environment={},
            ingest_actor=actor,
            ingest_timestamps={"finalized_at": finalized_at_iso},
        ),
    )