from __future__ import annotations

from fastapi import APIRouter, Depends, HTTPException, Query
from sqlalchemy import func, select
from sqlalchemy.orm import Session

from app.api.deps import get_db, require_operations_manager
from app.models.booking import Booking
from app.models.customer import Customer
from app.models.data_quality import DataQualityIssue
from app.models.inspection import Inspection
from app.models.vehicle import Vehicle
from app.schemas import (
    ApplyRecommendedStatusRequest,
    ApplyRecommendedStatusResult,
    CurrentUser,
    DataQualityIssueDetailOut,
    DataQualityIssueOut,
    DataQualityIssuePageOut,
    MergeCustomersRequest,
    MergeCustomersResult,
    ProvideFieldsRequest,
    ResolveOdometerRegressionRequest,
    ResolveOverlapRequest,
    ScanResultOut,
    StatusRecommendationOut,
    VehicleStatusFactsOut,
)
from app.services.data_quality import (
    apply_recommended_status,
    defer_issue,
    merge_customers,
    preview_vehicle_status_recommendation,
    provide_missing_fields,
    reject_issue,
    resolve_booking_overlap,
    resolve_odometer_regression,
    run_scan,
)

router = APIRouter(prefix="/api/v1/data-quality", tags=["data-quality"])


def _to_out(issue: DataQualityIssue) -> DataQualityIssueOut:
    return DataQualityIssueOut(
        public_ref=issue.public_ref,
        rule_type=issue.rule_type,
        entity_type=issue.entity_type,
        entity_ref=issue.evidence_json.get("entity_ref", ""),
        severity=issue.severity,
        status=issue.status,
        evidence=issue.evidence_json,
        detected_at=issue.detected_at,
        resolved_at=issue.resolved_at,
    )


@router.get("/issues", response_model=list[DataQualityIssueOut] | DataQualityIssuePageOut)
def list_issues(
    status: str | None = Query(default=None),
    rule_type: str | None = Query(default=None),
    severity: str | None = Query(default=None),
    page: int | None = Query(default=None, ge=1),
    page_size: int = Query(default=25, ge=1, le=25),
    db: Session = Depends(get_db),
    _user: CurrentUser = Depends(require_operations_manager),
) -> list[DataQualityIssueOut] | DataQualityIssuePageOut:
    stmt = select(DataQualityIssue).order_by(DataQualityIssue.detected_at.desc())
    if status:
        stmt = stmt.where(DataQualityIssue.status == status)
    if rule_type:
        stmt = stmt.where(DataQualityIssue.rule_type == rule_type)
    if severity:
        stmt = stmt.where(DataQualityIssue.severity == severity)
    total = db.scalar(select(func.count()).select_from(stmt.subquery())) or 0
    page_number = page or 1
    issues = db.scalars(
        stmt if page is None else stmt.offset((page_number - 1) * page_size).limit(page_size)
    ).all()
    items = [_to_out(i) for i in issues]
    if page is None:
        return items
    total_pages = max(1, (total + page_size - 1) // page_size)
    return DataQualityIssuePageOut(
        items=items,
        page=min(page_number, total_pages),
        page_size=page_size,
        total=total,
        total_pages=total_pages,
    )


# Every public reference in this system carries its entity type in its own prefix
# (CUS-/MO-/BK-/INSP-/DQ-). Related-entity typing is resolved from the reference itself,
# not guessed from the issue's rule_type -- a booking_overlap issue's related refs are
# bookings, not vehicles, and an inline odometer_regression issue's related refs mix a
# booking and an inspection ref in the same list.
_PREFIX_TO_TYPE = {
    "CUS-": "customer",
    "MO-": "vehicle",
    "BK-": "booking",
    "INSP-": "inspection",
}


def _entity_type_for_ref(ref: str) -> str | None:
    for prefix, entity_type in _PREFIX_TO_TYPE.items():
        if ref.startswith(prefix):
            return entity_type
    return None


def _snapshot(entity_type: str, ref: str, db: Session) -> dict | None:
    if entity_type == "customer":
        customer = db.scalar(select(Customer).where(Customer.public_ref == ref))
        if customer is None:
            return None
        return {
            "entity_type": "customer",
            "public_ref": customer.public_ref,
            "first_name": customer.first_name,
            "last_name": customer.last_name,
            "email": customer.email,
            "phone": customer.phone,
            "postal_code": customer.postal_code,
            "city": customer.city,
        }
    if entity_type == "vehicle":
        vehicle = db.scalar(select(Vehicle).where(Vehicle.public_ref == ref))
        if vehicle is None:
            return None
        return {
            "entity_type": "vehicle",
            "public_ref": vehicle.public_ref,
            "registration_number": vehicle.registration_number,
            "make": vehicle.make,
            "model": vehicle.model,
            "location": vehicle.location,
            "operational_status": vehicle.operational_status,
            "odometer_km": vehicle.odometer_km,
        }
    if entity_type == "booking":
        booking = db.scalar(select(Booking).where(Booking.public_ref == ref))
        if booking is None:
            return None
        vehicle = db.get(Vehicle, booking.vehicle_id)
        customer = db.get(Customer, booking.customer_id)
        return {
            "entity_type": "booking",
            "public_ref": booking.public_ref,
            "status": booking.status,
            "starts_at": booking.starts_at.isoformat(),
            "ends_at": booking.ends_at.isoformat(),
            "vehicle_ref": vehicle.public_ref if vehicle else None,
            "customer_ref": customer.public_ref if customer else None,
            "end_odometer_km": booking.end_odometer_km,
        }
    if entity_type == "inspection":
        inspection = db.scalar(select(Inspection).where(Inspection.public_ref == ref))
        if inspection is None:
            return None
        booking = db.get(Booking, inspection.booking_id)
        return {
            "entity_type": "inspection",
            "public_ref": inspection.public_ref,
            "type": inspection.type,
            "odometer_km": inspection.odometer_km,
            "completed_at": inspection.completed_at.isoformat(),
            "booking_ref": booking.public_ref if booking else None,
        }
    return None


@router.get("/issues/{public_ref}", response_model=DataQualityIssueDetailOut)
def get_issue(
    public_ref: str,
    db: Session = Depends(get_db),
    _user: CurrentUser = Depends(require_operations_manager),
) -> DataQualityIssueDetailOut:
    issue = db.scalar(select(DataQualityIssue).where(DataQualityIssue.public_ref == public_ref))
    if issue is None:
        raise HTTPException(status_code=404, detail="Data quality issue not found")
    base = _to_out(issue)
    related_refs = issue.evidence_json.get("related_refs", [])
    related_snapshots = []
    for ref in related_refs:
        entity_type = _entity_type_for_ref(ref)
        if entity_type is None:
            continue
        snap = _snapshot(entity_type, ref, db)
        if snap is not None:
            related_snapshots.append(snap)
    return DataQualityIssueDetailOut(
        **base.model_dump(),
        entity_snapshot=_snapshot(issue.entity_type, base.entity_ref, db),
        related_snapshots=related_snapshots,
    )


@router.post("/issues/{public_ref}/defer", response_model=DataQualityIssueOut)
def defer(
    public_ref: str,
    db: Session = Depends(get_db),
    user: CurrentUser = Depends(require_operations_manager),
) -> DataQualityIssueOut:
    issue = defer_issue(db, public_ref, user)
    return _to_out(issue)


@router.post("/issues/{public_ref}/reject", response_model=DataQualityIssueOut)
def reject(
    public_ref: str,
    db: Session = Depends(get_db),
    user: CurrentUser = Depends(require_operations_manager),
) -> DataQualityIssueOut:
    issue = reject_issue(db, public_ref, user)
    return _to_out(issue)


@router.post("/issues/{public_ref}/merge-customers", response_model=MergeCustomersResult)
def merge(
    public_ref: str,
    body: MergeCustomersRequest,
    db: Session = Depends(get_db),
    user: CurrentUser = Depends(require_operations_manager),
) -> MergeCustomersResult:
    result = merge_customers(db, public_ref, body.survivor_ref, body.field_overrides, user)
    return MergeCustomersResult(**result)


@router.post("/issues/{public_ref}/provide-fields", response_model=DataQualityIssueOut)
def provide_fields(
    public_ref: str,
    body: ProvideFieldsRequest,
    db: Session = Depends(get_db),
    user: CurrentUser = Depends(require_operations_manager),
) -> DataQualityIssueOut:
    issue = provide_missing_fields(db, public_ref, body.fields, user)
    return _to_out(issue)


@router.post(
    "/issues/{public_ref}/resolve-odometer-regression", response_model=DataQualityIssueOut
)
def resolve_odometer(
    public_ref: str,
    body: ResolveOdometerRegressionRequest,
    db: Session = Depends(get_db),
    user: CurrentUser = Depends(require_operations_manager),
) -> DataQualityIssueOut:
    issue = resolve_odometer_regression(db, public_ref, body, user)
    return _to_out(issue)


@router.post("/issues/{public_ref}/resolve-overlap", response_model=DataQualityIssueOut)
def resolve_overlap(
    public_ref: str,
    body: ResolveOverlapRequest,
    db: Session = Depends(get_db),
    user: CurrentUser = Depends(require_operations_manager),
) -> DataQualityIssueOut:
    issue = resolve_booking_overlap(db, public_ref, body.booking_ref, body.note, user)
    return _to_out(issue)


@router.post(
    "/issues/{public_ref}/status-recommendation", response_model=StatusRecommendationOut
)
def status_recommendation(
    public_ref: str,
    db: Session = Depends(get_db),
    user: CurrentUser = Depends(require_operations_manager),
) -> StatusRecommendationOut:
    """Non-mutating preview: computes the recommendation without changing anything,
    resolving no issue and writing no audit event. Safe to call repeatedly."""
    _issue, _vehicle, recommendation, token = preview_vehicle_status_recommendation(db, public_ref)
    return StatusRecommendationOut(
        current_status=recommendation.current_status,
        recommended_status=recommendation.recommended_status,
        recommendation_code=recommendation.recommendation_code,
        safe_to_apply=recommendation.safe_to_apply,
        manual_review_required=recommendation.manual_review_required,
        facts=VehicleStatusFactsOut(**recommendation.facts.as_dict()),
        blocking_reasons=recommendation.blocking_reasons,
        recommendation_token=token,
    )


@router.post(
    "/issues/{public_ref}/apply-recommended-status", response_model=ApplyRecommendedStatusResult
)
def apply_status(
    public_ref: str,
    body: ApplyRecommendedStatusRequest,
    db: Session = Depends(get_db),
    user: CurrentUser = Depends(require_operations_manager),
) -> ApplyRecommendedStatusResult:
    issue, applied_status, reason_code = apply_recommended_status(
        db, public_ref, user, body.recommendation_token
    )
    return ApplyRecommendedStatusResult(
        issue=_to_out(issue), applied_status=applied_status, reason_code=reason_code
    )


@router.post("/scan", response_model=ScanResultOut)
def scan(
    db: Session = Depends(get_db),
    user: CurrentUser = Depends(require_operations_manager),
) -> ScanResultOut:
    result = run_scan(db, actor_label=user.display_name, actor_type="user")
    return ScanResultOut(created=result.created)