"""MongoDB client + collection provider.

Every query is (a) tenant-scoped and (b) backed by explicit indexes.
"""

from __future__ import annotations

from contextlib import asynccontextmanager
from typing import AsyncIterator

from motor.motor_asyncio import (
    AsyncIOMotorClient,
    AsyncIOMotorCollection,
    AsyncIOMotorDatabase,
)
from pymongo import IndexModel
import structlog

from ..config import get_settings

log = structlog.get_logger(__name__)


_client: AsyncIOMotorClient | None = None
_db: AsyncIOMotorDatabase | None = None


class MongoCollections(str):
    ORGANIZATIONS = "organizations"
    USERS = "users"
    TEAMS = "teams"
    PROJECTS = "projects"
    ARTIFACTS = "artifacts"
    ARTIFACT_RELATIONSHIPS = "artifact_relationships"
    INTEGRATIONS = "integrations"
    JOBS = "jobs"
    AI_EXECUTIONS = "ai_executions"
    AUDIT_EVENTS = "audit_events"


def get_mongo_client() -> AsyncIOMotorClient:
    global _client
    if _client is None:
        s = get_settings()
        _client = AsyncIOMotorClient(
            s.mongo_uri,
            minPoolSize=s.mongo_min_pool_size,
            maxPoolSize=s.mongo_max_pool_size,
            uuidRepresentation="standard",
            tz_aware=True,
        )
    return _client


def get_mongo_db() -> AsyncIOMotorDatabase:
    global _db
    if _db is None:
        s = get_settings()
        _db = get_mongo_client()[s.mongo_db]
    return _db


def get_collection(name: MongoCollections | str) -> AsyncIOMotorCollection:
    return get_mongo_db()[name]


async def create_indexes() -> None:
    """Create (idempotent) indexes. Called once on service startup.

    Rule of thumb for tenanted data: compound index with ``tenant_id`` first,
    then the most common filter / sort key.
    """

    db = get_mongo_db()

    # --- organizations ---
    await db.organizations.create_indexes(
        [
            IndexModel("slug", unique=True, name="orgs_slug_unique"),
        ]
    )

    # --- users ---
    await db.users.create_indexes(
        [
            IndexModel([("tenant_id", 1), ("email", 1)], unique=True, name="users_tenant_email_unique"),
        ]
    )

    # --- projects ---
    await db.projects.create_indexes(
        [
            IndexModel([("tenant_id", 1), ("key", 1)], unique=True, name="projects_tenant_key_unique"),
            IndexModel([("tenant_id", 1), ("is_active", 1)], name="projects_tenant_active"),
        ]
    )

    # --- artifacts ---
    await db.artifacts.create_indexes(
        [
            IndexModel([("tenant_id", 1), ("project_id", 1)], name="arts_tenant_project"),
            IndexModel([("tenant_id", 1), ("project_id", 1), ("type", 1)], name="arts_tenant_project_type"),
            IndexModel([("tenant_id", 1), ("external_id", 1)], name="arts_tenant_external_id", sparse=True),
            IndexModel([("tenant_id", 1), ("created_at", -1)], name="arts_tenant_created_desc"),
        ]
    )

    # --- artifact_relationships ---
    # Two indexes: one for "where does this artifact point TO", one for "what points TO this artifact"
    await db.artifact_relationships.create_indexes(
        [
            IndexModel([("tenant_id", 1), ("source_artifact_id", 1), ("relationship_type", 1)],
                     name="rels_tenant_source_type"),
            IndexModel([("tenant_id", 1), ("target_artifact_id", 1), ("relationship_type", 1)],
                     name="rels_tenant_target_type"),
            IndexModel([("source_artifact_id", 1), ("target_artifact_id", 1), ("relationship_type", 1)],
                     unique=True, name="rels_unique_edge"),
        ]
    )

    # --- jobs ---
    await db.jobs.create_indexes(
        [
            IndexModel([("tenant_id", 1), ("status", 1), ("priority", -1), ("created_at", 1)],
                     name="jobs_tenant_status_priority"),
            IndexModel([("tenant_id", 1), ("project_id", 1), ("created_at", -1)],
                     name="jobs_tenant_project_created_desc"),
            IndexModel([("correlation_id", 1)], name="jobs_correlation_id", sparse=True),
        ]
    )

    # --- audit_events (append-only, oldest-to-newest scans normal) ---
    await db.audit_events.create_indexes(
        [
            IndexModel([("tenant_id", 1), ("created_at", -1)], name="audit_tenant_created_desc"),
            IndexModel([("tenant_id", 1), ("actor_id", 1), ("created_at", -1)], name="audit_tenant_actor_desc"),
            IndexModel([("correlation_id", 1)], name="audit_correlation_id", sparse=True),
        ]
    )

    # --- ai_executions ---
    await db.ai_executions.create_indexes(
        [
            IndexModel([("tenant_id", 1), ("created_at", -1)], name="aie_tenant_created_desc"),
            IndexModel([("tenant_id", 1), ("job_id", 1)], name="aie_tenant_job", sparse=True),
        ]
    )

    await log.adebug("mongo_indexes_ready")


async def close_mongo() -> None:
    global _client, _db
    if _client is not None:
        _client.close()
    _client = None
    _db = None


@asynccontextmanager
async def mongo_lifespan() -> AsyncIterator[None]:
    """Async lifespan helper for FastAPI startup / shutdown."""
    await create_indexes()
    try:
        yield
    finally:
        await close_mongo()