from __future__ import annotations

import uuid
from datetime import date

from fastapi import APIRouter, Depends, Header, Query, Response
from sqlalchemy import select
from sqlalchemy.orm import Session

from app.api.deps import McpClientContext, get_db, require_mcp_service_token
from app.core.config import get_settings
from app.core.errors import AppError
from app.models.booking import Booking
from app.models.data_quality import DataQualityIssue
from app.models.vehicle import Vehicle
from app.schemas import (
    AttentionVehicleOut,
    McpKnowledgeSearchRequest,
    McpVehicleDetailOut,
    OperationsSummaryOut,
)
from app.services.audit import record_audit_event
from app.services.knowledge import GroundedAnswer, get_knowledge_provider
from app.services.operations import compute_metrics, list_attention_vehicles

router = APIRouter(prefix="/api/v1/integrations/mcp", tags=["mcp"])
settings = get_settings()


def get_correlation_id(
    x_correlation_id: str | None = Header(default=None, alias="X-Correlation-Id"),
) -> str:
    """Preserve the Hub's own inbound correlation ID through MCP client -> Hub -> Fleet
    Ops -> RAGcore -> Fleet Ops Audit; only mint a fresh one when none was supplied or
    it isn't a valid UUID (per the task's own correlation-propagation contract)."""
    if x_correlation_id:
        try:
            return str(uuid.UUID(x_correlation_id))
        except ValueError:
            pass
    return str(uuid.uuid4())


def _audit_service_request(
    db: Session,
    *,
    client_id: str,
    tool: str,
    status_label: str,
    correlation_id: str,
    metadata: dict[str, object] | None = None,
) -> None:
    record_audit_event(
        db,
        actor_type="service",
        actor_label=client_id,
        action="mcp_tool_request",
        entity_type="mcp_tool",
        correlation_id=uuid.UUID(correlation_id),
        metadata={"tool": tool, "status": status_label, **(metadata or {})},
    )
    db.commit()


def _set_trace_headers(response: Response, correlation_id: str, tenant: str) -> None:
    response.headers["X-Correlation-Id"] = correlation_id
    response.headers["X-Tenant-Id"] = tenant
    response.headers["Cache-Control"] = "no-store"


@router.get("/operations-summary", response_model=OperationsSummaryOut)
def operations_summary(
    response: Response,
    db: Session = Depends(get_db),
    client: McpClientContext = Depends(require_mcp_service_token),
    correlation_id: str = Depends(get_correlation_id),
) -> OperationsSummaryOut:
    metrics = compute_metrics(db)
    _set_trace_headers(response, correlation_id, client.tenant)
    _audit_service_request(
        db,
        client_id=client.client_id,
        tool="fleet_ops_get_operations_summary",
        status_label="ok",
        correlation_id=correlation_id,
    )
    return OperationsSummaryOut(tenant=client.tenant, metrics=metrics)


@router.get("/attention-vehicles", response_model=list[AttentionVehicleOut])
def attention_vehicles(
    response: Response,
    minimum_severity: str = Query(default="medium", pattern="^(low|medium|high)$"),
    date_filter: date | None = Query(default=None, alias="date"),
    limit: int = Query(default=20, ge=1, le=50),
    db: Session = Depends(get_db),
    client: McpClientContext = Depends(require_mcp_service_token),
    correlation_id: str = Depends(get_correlation_id),
) -> list[AttentionVehicleOut]:
    results = list_attention_vehicles(
        db, minimum_severity=minimum_severity, on_or_before=date_filter, limit=limit
    )
    _set_trace_headers(response, correlation_id, client.tenant)
    _audit_service_request(
        db,
        client_id=client.client_id,
        tool="fleet_ops_list_attention_vehicles",
        status_label="ok",
        correlation_id=correlation_id,
    )
    return [AttentionVehicleOut(**r) for r in results]


@router.get("/vehicles/{vehicle_ref}", response_model=McpVehicleDetailOut)
def vehicle_details(
    vehicle_ref: str,
    response: Response,
    db: Session = Depends(get_db),
    client: McpClientContext = Depends(require_mcp_service_token),
    correlation_id: str = Depends(get_correlation_id),
) -> McpVehicleDetailOut:
    _set_trace_headers(response, correlation_id, client.tenant)
    vehicle = db.scalar(select(Vehicle).where(Vehicle.public_ref == vehicle_ref))
    if vehicle is None:
        _audit_service_request(
            db,
            client_id=client.client_id,
            tool="fleet_ops_get_vehicle_details",
            status_label="not_found",
            correlation_id=correlation_id,
        )
        raise AppError("VEHICLE_NOT_FOUND", "Vehicle not found.", status_code=404)

    open_issue_count = len(
        db.scalars(
            select(DataQualityIssue.id).where(
                DataQualityIssue.entity_type == "vehicle",
                DataQualityIssue.entity_id == vehicle.id,
                DataQualityIssue.status == "open",
            )
        ).all()
    )
    current_booking = db.scalar(
        select(Booking).where(Booking.vehicle_id == vehicle.id, Booking.status == "active")
    )

    _audit_service_request(
        db,
        client_id=client.client_id,
        tool="fleet_ops_get_vehicle_details",
        status_label="ok",
        correlation_id=correlation_id,
    )
    return McpVehicleDetailOut(
        public_ref=vehicle.public_ref,
        make=vehicle.make,
        model=vehicle.model,
        model_year=vehicle.model_year,
        location=vehicle.location,
        operational_status=vehicle.operational_status,
        odometer_km=vehicle.odometer_km,
        next_service_km=vehicle.next_service_km,
        open_quality_issue_count=open_issue_count,
        current_booking_ref=current_booking.public_ref if current_booking else None,
    )


@router.post("/search-knowledge", response_model=GroundedAnswer)
def search_knowledge(
    body: McpKnowledgeSearchRequest,
    response: Response,
    db: Session = Depends(get_db),
    client: McpClientContext = Depends(require_mcp_service_token),
    correlation_id: str = Depends(get_correlation_id),
) -> GroundedAnswer:
    provider = get_knowledge_provider()
    answer = provider.ask(body.question, correlation_id, language=body.locale)
    source_count_available = len(answer.sources)
    answer.sources = answer.sources[: body.max_sources]
    _set_trace_headers(response, correlation_id, client.tenant)
    response.headers["X-Sources-Available"] = str(source_count_available)
    response.headers["X-Sources-Returned"] = str(len(answer.sources))
    _audit_service_request(
        db,
        client_id=client.client_id,
        tool="fleet_ops_search_knowledge",
        status_label=answer.evidence_state,
        correlation_id=correlation_id,
        metadata={
            "tenant": client.tenant,
            "locale": body.locale,
            "sources_available": source_count_available,
            "sources_returned": len(answer.sources),
        },
    )
    return answer