"""
FastAPI routes for VVT — Verzeichnis von Verarbeitungstaetigkeiten (Art. 30 DSGVO).

Endpoints:
  GET    /vvt/organization         — Load organization header
  PUT    /vvt/organization         — Save organization header
  GET    /vvt/activities           — List activities (filter: status, business_function)
  POST   /vvt/activities           — Create new activity
  GET    /vvt/activities/{id}      — Get single activity
  PUT    /vvt/activities/{id}      — Update activity
  DELETE /vvt/activities/{id}      — Delete activity
  GET    /vvt/audit-log            — Audit trail (limit, offset)
  GET    /vvt/export               — JSON export of all activities
  GET    /vvt/stats                — Statistics
"""

import csv
import io
import logging
from datetime import datetime, timezone
from typing import Optional, List

from fastapi import APIRouter, Depends, HTTPException, Query, Request
from fastapi.responses import StreamingResponse
from sqlalchemy.orm import Session

from classroom_engine.database import get_db

from ..db.vvt_models import VVTOrganizationDB, VVTActivityDB, VVTAuditLogDB
from .schemas import (
    VVTOrganizationUpdate, VVTOrganizationResponse,
    VVTActivityCreate, VVTActivityUpdate, VVTActivityResponse,
    VVTStatsResponse, VVTAuditLogEntry,
)
from .tenant_utils import get_tenant_id

logger = logging.getLogger(__name__)
router = APIRouter(prefix="/vvt", tags=["compliance-vvt"])


def _log_audit(
    db: Session,
    tenant_id: str,
    action: str,
    entity_type: str,
    entity_id=None,
    changed_by: str = "system",
    old_values=None,
    new_values=None,
):
    entry = VVTAuditLogDB(
        tenant_id=tenant_id,
        action=action,
        entity_type=entity_type,
        entity_id=entity_id,
        changed_by=changed_by,
        old_values=old_values,
        new_values=new_values,
    )
    db.add(entry)


# ============================================================================
# Organization Header
# ============================================================================

@router.get("/organization", response_model=Optional[VVTOrganizationResponse])
async def get_organization(
    tid: str = Depends(get_tenant_id),
    db: Session = Depends(get_db),
):
    """Load the VVT organization header for the given tenant."""
    org = (
        db.query(VVTOrganizationDB)
        .filter(VVTOrganizationDB.tenant_id == tid)
        .order_by(VVTOrganizationDB.created_at)
        .first()
    )
    if not org:
        return None
    return VVTOrganizationResponse(
        id=str(org.id),
        organization_name=org.organization_name,
        industry=org.industry,
        locations=org.locations or [],
        employee_count=org.employee_count,
        dpo_name=org.dpo_name,
        dpo_contact=org.dpo_contact,
        vvt_version=org.vvt_version or '1.0',
        last_review_date=org.last_review_date,
        next_review_date=org.next_review_date,
        review_interval=org.review_interval or 'annual',
        created_at=org.created_at,
        updated_at=org.updated_at,
    )


@router.put("/organization", response_model=VVTOrganizationResponse)
async def upsert_organization(
    request: VVTOrganizationUpdate,
    tid: str = Depends(get_tenant_id),
    db: Session = Depends(get_db),
):
    """Create or update the VVT organization header."""
    org = (
        db.query(VVTOrganizationDB)
        .filter(VVTOrganizationDB.tenant_id == tid)
        .order_by(VVTOrganizationDB.created_at)
        .first()
    )

    if not org:
        data = request.dict(exclude_none=True)
        if 'organization_name' not in data:
            data['organization_name'] = 'Meine Organisation'
        data['tenant_id'] = tid
        org = VVTOrganizationDB(**data)
        db.add(org)
    else:
        for field, value in request.dict(exclude_none=True).items():
            setattr(org, field, value)
        org.updated_at = datetime.utcnow()

    db.commit()
    db.refresh(org)

    return VVTOrganizationResponse(
        id=str(org.id),
        organization_name=org.organization_name,
        industry=org.industry,
        locations=org.locations or [],
        employee_count=org.employee_count,
        dpo_name=org.dpo_name,
        dpo_contact=org.dpo_contact,
        vvt_version=org.vvt_version or '1.0',
        last_review_date=org.last_review_date,
        next_review_date=org.next_review_date,
        review_interval=org.review_interval or 'annual',
        created_at=org.created_at,
        updated_at=org.updated_at,
    )


# ============================================================================
# Activities
# ============================================================================

def _activity_to_response(act: VVTActivityDB) -> VVTActivityResponse:
    return VVTActivityResponse(
        id=str(act.id),
        vvt_id=act.vvt_id,
        name=act.name,
        description=act.description,
        purposes=act.purposes or [],
        legal_bases=act.legal_bases or [],
        data_subject_categories=act.data_subject_categories or [],
        personal_data_categories=act.personal_data_categories or [],
        recipient_categories=act.recipient_categories or [],
        third_country_transfers=act.third_country_transfers or [],
        retention_period=act.retention_period or {},
        tom_description=act.tom_description,
        business_function=act.business_function,
        systems=act.systems or [],
        deployment_model=act.deployment_model,
        data_sources=act.data_sources or [],
        data_flows=act.data_flows or [],
        protection_level=act.protection_level or 'MEDIUM',
        dpia_required=act.dpia_required or False,
        structured_toms=act.structured_toms or {},
        status=act.status or 'DRAFT',
        responsible=act.responsible,
        owner=act.owner,
        last_reviewed_at=act.last_reviewed_at,
        next_review_at=act.next_review_at,
        created_by=act.created_by,
        dsfa_id=str(act.dsfa_id) if act.dsfa_id else None,
        # Library refs
        purpose_refs=act.purpose_refs,
        legal_basis_refs=act.legal_basis_refs,
        data_subject_refs=act.data_subject_refs,
        data_category_refs=act.data_category_refs,
        recipient_refs=act.recipient_refs,
        retention_rule_ref=act.retention_rule_ref,
        transfer_mechanism_refs=act.transfer_mechanism_refs,
        tom_refs=act.tom_refs,
        source_template_id=act.source_template_id,
        risk_score=act.risk_score,
        linked_loeschfristen_ids=act.linked_loeschfristen_ids,
        linked_tom_measure_ids=act.linked_tom_measure_ids,
        art30_completeness=act.art30_completeness,
        created_at=act.created_at,
        updated_at=act.updated_at,
    )


@router.get("/activities", response_model=List[VVTActivityResponse])
async def list_activities(
    status: Optional[str] = Query(None),
    business_function: Optional[str] = Query(None),
    search: Optional[str] = Query(None),
    review_overdue: Optional[bool] = Query(None),
    tid: str = Depends(get_tenant_id),
    db: Session = Depends(get_db),
):
    """List all processing activities with optional filters."""
    query = db.query(VVTActivityDB).filter(VVTActivityDB.tenant_id == tid)

    if status:
        query = query.filter(VVTActivityDB.status == status)
    if business_function:
        query = query.filter(VVTActivityDB.business_function == business_function)
    if review_overdue:
        now = datetime.now(timezone.utc)
        query = query.filter(
            VVTActivityDB.next_review_at.isnot(None),
            VVTActivityDB.next_review_at < now,
        )
    if search:
        term = f"%{search}%"
        query = query.filter(
            (VVTActivityDB.name.ilike(term)) |
            (VVTActivityDB.description.ilike(term)) |
            (VVTActivityDB.vvt_id.ilike(term))
        )

    activities = query.order_by(VVTActivityDB.created_at.desc()).all()
    return [_activity_to_response(a) for a in activities]


@router.post("/activities", response_model=VVTActivityResponse, status_code=201)
async def create_activity(
    request: VVTActivityCreate,
    http_request: Request,
    tid: str = Depends(get_tenant_id),
    db: Session = Depends(get_db),
):
    """Create a new processing activity."""
    # Check for duplicate vvt_id within tenant
    existing = db.query(VVTActivityDB).filter(
        VVTActivityDB.tenant_id == tid,
        VVTActivityDB.vvt_id == request.vvt_id,
    ).first()
    if existing:
        raise HTTPException(
            status_code=409,
            detail=f"Activity with VVT-ID '{request.vvt_id}' already exists"
        )

    data = request.dict()
    data['tenant_id'] = tid
    # Set created_by from X-User-ID header if not provided in body
    if not data.get('created_by'):
        data['created_by'] = http_request.headers.get('X-User-ID', 'system')

    act = VVTActivityDB(**data)
    db.add(act)
    db.flush()  # get ID before audit log

    _log_audit(
        db,
        tenant_id=tid,
        action="CREATE",
        entity_type="activity",
        entity_id=act.id,
        new_values={"vvt_id": act.vvt_id, "name": act.name, "status": act.status},
    )

    db.commit()
    db.refresh(act)
    return _activity_to_response(act)


@router.get("/activities/{activity_id}", response_model=VVTActivityResponse)
async def get_activity(
    activity_id: str,
    tid: str = Depends(get_tenant_id),
    db: Session = Depends(get_db),
):
    """Get a single processing activity by ID."""
    act = db.query(VVTActivityDB).filter(
        VVTActivityDB.id == activity_id,
        VVTActivityDB.tenant_id == tid,
    ).first()
    if not act:
        raise HTTPException(status_code=404, detail=f"Activity {activity_id} not found")
    return _activity_to_response(act)


@router.put("/activities/{activity_id}", response_model=VVTActivityResponse)
async def update_activity(
    activity_id: str,
    request: VVTActivityUpdate,
    tid: str = Depends(get_tenant_id),
    db: Session = Depends(get_db),
):
    """Update a processing activity."""
    act = db.query(VVTActivityDB).filter(
        VVTActivityDB.id == activity_id,
        VVTActivityDB.tenant_id == tid,
    ).first()
    if not act:
        raise HTTPException(status_code=404, detail=f"Activity {activity_id} not found")

    old_values = {"name": act.name, "status": act.status}
    updates = request.dict(exclude_none=True)
    for field, value in updates.items():
        setattr(act, field, value)
    act.updated_at = datetime.utcnow()

    _log_audit(
        db,
        tenant_id=tid,
        action="UPDATE",
        entity_type="activity",
        entity_id=act.id,
        old_values=old_values,
        new_values=updates,
    )

    db.commit()
    db.refresh(act)
    return _activity_to_response(act)


@router.delete("/activities/{activity_id}")
async def delete_activity(
    activity_id: str,
    tid: str = Depends(get_tenant_id),
    db: Session = Depends(get_db),
):
    """Delete a processing activity."""
    act = db.query(VVTActivityDB).filter(
        VVTActivityDB.id == activity_id,
        VVTActivityDB.tenant_id == tid,
    ).first()
    if not act:
        raise HTTPException(status_code=404, detail=f"Activity {activity_id} not found")

    _log_audit(
        db,
        tenant_id=tid,
        action="DELETE",
        entity_type="activity",
        entity_id=act.id,
        old_values={"vvt_id": act.vvt_id, "name": act.name},
    )

    db.delete(act)
    db.commit()
    return {"success": True, "message": f"Activity {activity_id} deleted"}


# ============================================================================
# Art. 30 Completeness Check
# ============================================================================

@router.get("/activities/{activity_id}/completeness")
async def get_activity_completeness(
    activity_id: str,
    tid: str = Depends(get_tenant_id),
    db: Session = Depends(get_db),
):
    """Calculate Art. 30 completeness score for a VVT activity."""
    act = db.query(VVTActivityDB).filter(
        VVTActivityDB.id == activity_id,
        VVTActivityDB.tenant_id == tid,
    ).first()
    if not act:
        raise HTTPException(status_code=404, detail=f"Activity {activity_id} not found")
    return _calculate_completeness(act)


def _calculate_completeness(act: VVTActivityDB) -> dict:
    """Calculate Art. 30 completeness — required fields per DSGVO Art. 30 Abs. 1."""
    missing = []
    warnings = []
    total_checks = 10
    passed = 0

    # 1. Name/Zweck
    if act.name:
        passed += 1
    else:
        missing.append("name")

    # 2. Verarbeitungszwecke
    has_purposes = bool(act.purposes) or bool(act.purpose_refs)
    if has_purposes:
        passed += 1
    else:
        missing.append("purposes")

    # 3. Rechtsgrundlage
    has_legal = bool(act.legal_bases) or bool(act.legal_basis_refs)
    if has_legal:
        passed += 1
    else:
        missing.append("legal_bases")

    # 4. Betroffenenkategorien
    has_subjects = bool(act.data_subject_categories) or bool(act.data_subject_refs)
    if has_subjects:
        passed += 1
    else:
        missing.append("data_subjects")

    # 5. Datenkategorien
    has_categories = bool(act.personal_data_categories) or bool(act.data_category_refs)
    if has_categories:
        passed += 1
    else:
        missing.append("data_categories")

    # 6. Empfaenger
    has_recipients = bool(act.recipient_categories) or bool(act.recipient_refs)
    if has_recipients:
        passed += 1
    else:
        missing.append("recipients")

    # 7. Drittland-Uebermittlung (checked but not strictly required)
    passed += 1  # always passes — no transfer is valid state

    # 8. Loeschfristen
    has_retention = bool(act.retention_period and act.retention_period.get('description')) or bool(act.retention_rule_ref)
    if has_retention:
        passed += 1
    else:
        missing.append("retention_period")

    # 9. TOM-Beschreibung
    has_tom = bool(act.tom_description) or bool(act.tom_refs) or bool(act.structured_toms)
    if has_tom:
        passed += 1
    else:
        missing.append("tom_description")

    # 10. Verantwortlicher
    if act.responsible:
        passed += 1
    else:
        missing.append("responsible")

    # Warnings
    if act.dpia_required and not act.dsfa_id:
        warnings.append("dpia_required_but_no_dsfa_linked")
    if act.third_country_transfers and not act.transfer_mechanism_refs:
        warnings.append("third_country_transfer_without_mechanism")

    score = int((passed / total_checks) * 100)
    return {"score": score, "missing": missing, "warnings": warnings, "passed": passed, "total": total_checks}


# ============================================================================
# Audit Log
# ============================================================================

@router.get("/audit-log", response_model=List[VVTAuditLogEntry])
async def get_audit_log(
    limit: int = Query(50, ge=1, le=500),
    offset: int = Query(0, ge=0),
    tid: str = Depends(get_tenant_id),
    db: Session = Depends(get_db),
):
    """Get the VVT audit trail."""
    entries = (
        db.query(VVTAuditLogDB)
        .filter(VVTAuditLogDB.tenant_id == tid)
        .order_by(VVTAuditLogDB.created_at.desc())
        .offset(offset)
        .limit(limit)
        .all()
    )
    return [
        VVTAuditLogEntry(
            id=str(e.id),
            action=e.action,
            entity_type=e.entity_type,
            entity_id=str(e.entity_id) if e.entity_id else None,
            changed_by=e.changed_by,
            old_values=e.old_values,
            new_values=e.new_values,
            created_at=e.created_at,
        )
        for e in entries
    ]


# ============================================================================
# Export & Stats
# ============================================================================

@router.get("/export")
async def export_activities(
    format: str = Query("json", pattern="^(json|csv)$"),
    tid: str = Depends(get_tenant_id),
    db: Session = Depends(get_db),
):
    """Export all activities as JSON or CSV (semicolon-separated, DE locale)."""
    org = (
        db.query(VVTOrganizationDB)
        .filter(VVTOrganizationDB.tenant_id == tid)
        .order_by(VVTOrganizationDB.created_at)
        .first()
    )
    activities = (
        db.query(VVTActivityDB)
        .filter(VVTActivityDB.tenant_id == tid)
        .order_by(VVTActivityDB.created_at)
        .all()
    )

    _log_audit(
        db,
        tenant_id=tid,
        action="EXPORT",
        entity_type="all_activities",
        new_values={"count": len(activities), "format": format},
    )
    db.commit()

    if format == "csv":
        return _export_csv(activities)

    return {
        "exported_at": datetime.utcnow().isoformat(),
        "organization": {
            "name": org.organization_name if org else "",
            "dpo_name": org.dpo_name if org else "",
            "dpo_contact": org.dpo_contact if org else "",
            "vvt_version": org.vvt_version if org else "1.0",
        } if org else None,
        "activities": [
            {
                "id": str(a.id),
                "vvt_id": a.vvt_id,
                "name": a.name,
                "description": a.description,
                "status": a.status,
                "purposes": a.purposes,
                "legal_bases": a.legal_bases,
                "data_subject_categories": a.data_subject_categories,
                "personal_data_categories": a.personal_data_categories,
                "recipient_categories": a.recipient_categories,
                "third_country_transfers": a.third_country_transfers,
                "retention_period": a.retention_period,
                "dpia_required": a.dpia_required,
                "protection_level": a.protection_level,
                "business_function": a.business_function,
                "responsible": a.responsible,
                "created_by": a.created_by,
                "dsfa_id": str(a.dsfa_id) if a.dsfa_id else None,
                "last_reviewed_at": a.last_reviewed_at.isoformat() if a.last_reviewed_at else None,
                "next_review_at": a.next_review_at.isoformat() if a.next_review_at else None,
                "created_at": a.created_at.isoformat(),
                "updated_at": a.updated_at.isoformat() if a.updated_at else None,
            }
            for a in activities
        ],
    }


def _export_csv(activities: list) -> StreamingResponse:
    """Generate semicolon-separated CSV with UTF-8 BOM for German Excel compatibility."""
    output = io.StringIO()
    # UTF-8 BOM for Excel
    output.write('\ufeff')

    writer = csv.writer(output, delimiter=';', quoting=csv.QUOTE_MINIMAL)
    writer.writerow([
        'ID', 'VVT-ID', 'Name', 'Zweck', 'Rechtsgrundlage',
        'Datenkategorien', 'Betroffene', 'Empfaenger', 'Drittland',
        'Aufbewahrung', 'Status', 'Verantwortlich', 'Erstellt von',
        'Erstellt am',
    ])

    for a in activities:
        writer.writerow([
            str(a.id),
            a.vvt_id,
            a.name,
            '; '.join(a.purposes or []),
            '; '.join(a.legal_bases or []),
            '; '.join(a.personal_data_categories or []),
            '; '.join(a.data_subject_categories or []),
            '; '.join(a.recipient_categories or []),
            'Ja' if a.third_country_transfers else 'Nein',
            str(a.retention_period) if a.retention_period else '',
            a.status or 'DRAFT',
            a.responsible or '',
            a.created_by or 'system',
            a.created_at.strftime('%d.%m.%Y %H:%M') if a.created_at else '',
        ])

    output.seek(0)
    return StreamingResponse(
        iter([output.getvalue()]),
        media_type='text/csv; charset=utf-8',
        headers={
            'Content-Disposition': f'attachment; filename="vvt_export_{datetime.utcnow().strftime("%Y%m%d")}.csv"'
        },
    )


@router.get("/stats", response_model=VVTStatsResponse)
async def get_stats(
    tid: str = Depends(get_tenant_id),
    db: Session = Depends(get_db),
):
    """Get VVT statistics summary."""
    activities = db.query(VVTActivityDB).filter(VVTActivityDB.tenant_id == tid).all()

    by_status: dict = {}
    by_bf: dict = {}
    now = datetime.now(timezone.utc)
    overdue_count = 0

    for a in activities:
        status = a.status or 'DRAFT'
        bf = a.business_function or 'unknown'
        by_status[status] = by_status.get(status, 0) + 1
        by_bf[bf] = by_bf.get(bf, 0) + 1
        if a.next_review_at and a.next_review_at < now:
            overdue_count += 1

    return VVTStatsResponse(
        total=len(activities),
        by_status=by_status,
        by_business_function=by_bf,
        dpia_required_count=sum(1 for a in activities if a.dpia_required),
        third_country_count=sum(1 for a in activities if a.third_country_transfers),
        draft_count=by_status.get('DRAFT', 0),
        approved_count=by_status.get('APPROVED', 0),
        overdue_review_count=overdue_count,
    )


# ============================================================================
# Versioning
# ============================================================================

@router.get("/activities/{activity_id}/versions")
async def list_activity_versions(
    activity_id: str,
    tid: str = Depends(get_tenant_id),
    db: Session = Depends(get_db),
):
    """List all versions for a VVT activity."""
    from .versioning_utils import list_versions
    return list_versions(db, "vvt_activity", activity_id, tid)


@router.get("/activities/{activity_id}/versions/{version_number}")
async def get_activity_version(
    activity_id: str,
    version_number: int,
    tid: str = Depends(get_tenant_id),
    db: Session = Depends(get_db),
):
    """Get a specific VVT activity version with full snapshot."""
    from .versioning_utils import get_version
    v = get_version(db, "vvt_activity", activity_id, version_number, tid)
    if not v:
        raise HTTPException(status_code=404, detail=f"Version {version_number} not found")
    return v