"""
FastAPI routes for Legal Documents — Rechtliche Texte mit Versionierung und Approval-Workflow.

Endpoints:
  GET    /legal-documents/documents                        — Liste aller Dokumente
  POST   /legal-documents/documents                        — Dokument erstellen
  GET    /legal-documents/documents/{id}/versions          — Versionen eines Dokuments
  POST   /legal-documents/versions                         — Neue Version erstellen
  PUT    /legal-documents/versions/{id}                    — Version aktualisieren
  POST   /legal-documents/versions/upload-word             — DOCX → HTML
  POST   /legal-documents/versions/{id}/submit-review      — Status: draft → review
  POST   /legal-documents/versions/{id}/approve            — Status: review → approved
  POST   /legal-documents/versions/{id}/reject             — Status: review → rejected
  POST   /legal-documents/versions/{id}/publish            — Status: approved → published
  GET    /legal-documents/versions/{id}/approval-history   — Approval-Audit-Trail
"""

import logging
from datetime import datetime
from typing import Optional, List, Any, Dict

from fastapi import APIRouter, Depends, HTTPException, Query, UploadFile, File
from pydantic import BaseModel
from sqlalchemy.orm import Session

from classroom_engine.database import get_db
from ..db.legal_document_models import (
    LegalDocumentDB,
    LegalDocumentVersionDB,
    LegalDocumentApprovalDB,
)

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


# ============================================================================
# Pydantic Schemas
# ============================================================================

class DocumentCreate(BaseModel):
    type: str
    name: str
    description: Optional[str] = None
    mandatory: bool = False
    tenant_id: Optional[str] = None


class DocumentResponse(BaseModel):
    id: str
    tenant_id: Optional[str]
    type: str
    name: str
    description: Optional[str]
    mandatory: bool
    created_at: datetime
    updated_at: Optional[datetime]


class VersionCreate(BaseModel):
    document_id: str
    version: str
    language: str = 'de'
    title: str
    content: str
    summary: Optional[str] = None
    created_by: Optional[str] = None


class VersionUpdate(BaseModel):
    title: Optional[str] = None
    content: Optional[str] = None
    summary: Optional[str] = None
    version: Optional[str] = None
    language: Optional[str] = None


class VersionResponse(BaseModel):
    id: str
    document_id: str
    version: str
    language: str
    title: str
    content: str
    summary: Optional[str]
    status: str
    created_by: Optional[str]
    approved_by: Optional[str]
    approved_at: Optional[datetime]
    rejection_reason: Optional[str]
    created_at: datetime
    updated_at: Optional[datetime]


class ApprovalHistoryEntry(BaseModel):
    id: str
    version_id: str
    action: str
    approver: Optional[str]
    comment: Optional[str]
    created_at: datetime


class ActionRequest(BaseModel):
    approver: Optional[str] = None
    comment: Optional[str] = None


# ============================================================================
# Helpers
# ============================================================================

def _doc_to_response(doc: LegalDocumentDB) -> DocumentResponse:
    return DocumentResponse(
        id=str(doc.id),
        tenant_id=doc.tenant_id,
        type=doc.type,
        name=doc.name,
        description=doc.description,
        mandatory=doc.mandatory or False,
        created_at=doc.created_at,
        updated_at=doc.updated_at,
    )


def _version_to_response(v: LegalDocumentVersionDB) -> VersionResponse:
    return VersionResponse(
        id=str(v.id),
        document_id=str(v.document_id),
        version=v.version,
        language=v.language or 'de',
        title=v.title,
        content=v.content,
        summary=v.summary,
        status=v.status or 'draft',
        created_by=v.created_by,
        approved_by=v.approved_by,
        approved_at=v.approved_at,
        rejection_reason=v.rejection_reason,
        created_at=v.created_at,
        updated_at=v.updated_at,
    )


def _log_approval(
    db: Session,
    version_id: Any,
    action: str,
    approver: Optional[str] = None,
    comment: Optional[str] = None,
) -> LegalDocumentApprovalDB:
    entry = LegalDocumentApprovalDB(
        version_id=version_id,
        action=action,
        approver=approver,
        comment=comment,
    )
    db.add(entry)
    return entry


# ============================================================================
# Documents
# ============================================================================

@router.get("/documents", response_model=Dict[str, Any])
async def list_documents(
    tenant_id: Optional[str] = Query(None),
    type: Optional[str] = Query(None),
    db: Session = Depends(get_db),
):
    """List all legal documents, optionally filtered by tenant or type."""
    query = db.query(LegalDocumentDB)
    if tenant_id:
        query = query.filter(LegalDocumentDB.tenant_id == tenant_id)
    if type:
        query = query.filter(LegalDocumentDB.type == type)

    docs = query.order_by(LegalDocumentDB.created_at.desc()).all()
    return {"documents": [_doc_to_response(d).dict() for d in docs]}


@router.post("/documents", response_model=DocumentResponse, status_code=201)
async def create_document(
    request: DocumentCreate,
    db: Session = Depends(get_db),
):
    """Create a new legal document type."""
    doc = LegalDocumentDB(
        tenant_id=request.tenant_id,
        type=request.type,
        name=request.name,
        description=request.description,
        mandatory=request.mandatory,
    )
    db.add(doc)
    db.commit()
    db.refresh(doc)
    return _doc_to_response(doc)


@router.get("/documents/{document_id}", response_model=DocumentResponse)
async def get_document(document_id: str, db: Session = Depends(get_db)):
    """Get a single legal document by ID."""
    doc = db.query(LegalDocumentDB).filter(LegalDocumentDB.id == document_id).first()
    if not doc:
        raise HTTPException(status_code=404, detail=f"Document {document_id} not found")
    return _doc_to_response(doc)


@router.delete("/documents/{document_id}", status_code=204)
async def delete_document(document_id: str, db: Session = Depends(get_db)):
    """Delete a legal document and all its versions."""
    doc = db.query(LegalDocumentDB).filter(LegalDocumentDB.id == document_id).first()
    if not doc:
        raise HTTPException(status_code=404, detail=f"Document {document_id} not found")
    db.delete(doc)
    db.commit()


@router.get("/documents/{document_id}/versions", response_model=List[VersionResponse])
async def list_versions(document_id: str, db: Session = Depends(get_db)):
    """List all versions for a legal document."""
    doc = db.query(LegalDocumentDB).filter(LegalDocumentDB.id == document_id).first()
    if not doc:
        raise HTTPException(status_code=404, detail=f"Document {document_id} not found")

    versions = (
        db.query(LegalDocumentVersionDB)
        .filter(LegalDocumentVersionDB.document_id == document_id)
        .order_by(LegalDocumentVersionDB.created_at.desc())
        .all()
    )
    return [_version_to_response(v) for v in versions]


# ============================================================================
# Versions
# ============================================================================

@router.post("/versions", response_model=VersionResponse, status_code=201)
async def create_version(
    request: VersionCreate,
    db: Session = Depends(get_db),
):
    """Create a new version for a legal document."""
    doc = db.query(LegalDocumentDB).filter(LegalDocumentDB.id == request.document_id).first()
    if not doc:
        raise HTTPException(status_code=404, detail=f"Document {request.document_id} not found")

    version = LegalDocumentVersionDB(
        document_id=request.document_id,
        version=request.version,
        language=request.language,
        title=request.title,
        content=request.content,
        summary=request.summary,
        created_by=request.created_by,
        status='draft',
    )
    db.add(version)
    db.flush()

    _log_approval(db, version.id, action='created', approver=request.created_by)

    db.commit()
    db.refresh(version)
    return _version_to_response(version)


@router.put("/versions/{version_id}", response_model=VersionResponse)
async def update_version(
    version_id: str,
    request: VersionUpdate,
    db: Session = Depends(get_db),
):
    """Update a draft legal document version."""
    version = db.query(LegalDocumentVersionDB).filter(LegalDocumentVersionDB.id == version_id).first()
    if not version:
        raise HTTPException(status_code=404, detail=f"Version {version_id} not found")
    if version.status not in ('draft', 'rejected'):
        raise HTTPException(status_code=400, detail=f"Only draft/rejected versions can be edited (current: {version.status})")

    for field, value in request.dict(exclude_none=True).items():
        setattr(version, field, value)
    version.updated_at = datetime.utcnow()

    db.commit()
    db.refresh(version)
    return _version_to_response(version)


@router.get("/versions/{version_id}", response_model=VersionResponse)
async def get_version(version_id: str, db: Session = Depends(get_db)):
    """Get a single version by ID."""
    v = db.query(LegalDocumentVersionDB).filter(LegalDocumentVersionDB.id == version_id).first()
    if not v:
        raise HTTPException(status_code=404, detail=f"Version {version_id} not found")
    return _version_to_response(v)


@router.post("/versions/upload-word", response_model=Dict[str, Any])
async def upload_word(file: UploadFile = File(...)):
    """Convert DOCX to HTML using mammoth (if available) or return raw text."""
    if not file.filename or not file.filename.lower().endswith('.docx'):
        raise HTTPException(status_code=400, detail="Only .docx files are supported")

    content_bytes = await file.read()
    html_content = ""

    try:
        import mammoth  # type: ignore
        import io
        result = mammoth.convert_to_html(io.BytesIO(content_bytes))
        html_content = result.value
    except ImportError:
        # Fallback: return placeholder if mammoth not installed
        html_content = f"<p>[DOCX-Import: {file.filename}]</p><p>Bitte installieren Sie 'mammoth' fuer DOCX-Konvertierung.</p>"

    return {"html": html_content, "filename": file.filename}


# ============================================================================
# Approval Workflow Actions
# ============================================================================

def _transition(
    db: Session,
    version_id: str,
    from_statuses: List[str],
    to_status: str,
    action: str,
    approver: Optional[str],
    comment: Optional[str],
    extra_updates: Optional[Dict] = None,
) -> VersionResponse:
    version = db.query(LegalDocumentVersionDB).filter(LegalDocumentVersionDB.id == version_id).first()
    if not version:
        raise HTTPException(status_code=404, detail=f"Version {version_id} not found")
    if version.status not in from_statuses:
        raise HTTPException(
            status_code=400,
            detail=f"Cannot perform '{action}' on version with status '{version.status}' (expected: {from_statuses})"
        )

    version.status = to_status
    version.updated_at = datetime.utcnow()
    if extra_updates:
        for k, v in extra_updates.items():
            setattr(version, k, v)

    _log_approval(db, version.id, action=action, approver=approver, comment=comment)

    db.commit()
    db.refresh(version)
    return _version_to_response(version)


@router.post("/versions/{version_id}/submit-review", response_model=VersionResponse)
async def submit_review(
    version_id: str,
    request: ActionRequest,
    db: Session = Depends(get_db),
):
    """Submit a draft version for review."""
    return _transition(db, version_id, ['draft', 'rejected'], 'review', 'submitted', request.approver, request.comment)


@router.post("/versions/{version_id}/approve", response_model=VersionResponse)
async def approve_version(
    version_id: str,
    request: ActionRequest,
    db: Session = Depends(get_db),
):
    """Approve a version under review."""
    return _transition(
        db, version_id, ['review'], 'approved', 'approved',
        request.approver, request.comment,
        extra_updates={'approved_by': request.approver, 'approved_at': datetime.utcnow()}
    )


@router.post("/versions/{version_id}/reject", response_model=VersionResponse)
async def reject_version(
    version_id: str,
    request: ActionRequest,
    db: Session = Depends(get_db),
):
    """Reject a version under review."""
    return _transition(
        db, version_id, ['review'], 'rejected', 'rejected',
        request.approver, request.comment,
        extra_updates={'rejection_reason': request.comment}
    )


@router.post("/versions/{version_id}/publish", response_model=VersionResponse)
async def publish_version(
    version_id: str,
    request: ActionRequest,
    db: Session = Depends(get_db),
):
    """Publish an approved version."""
    return _transition(db, version_id, ['approved'], 'published', 'published', request.approver, request.comment)


# ============================================================================
# Approval History
# ============================================================================

@router.get("/versions/{version_id}/approval-history", response_model=List[ApprovalHistoryEntry])
async def get_approval_history(version_id: str, db: Session = Depends(get_db)):
    """Get the full approval audit trail for a version."""
    version = db.query(LegalDocumentVersionDB).filter(LegalDocumentVersionDB.id == version_id).first()
    if not version:
        raise HTTPException(status_code=404, detail=f"Version {version_id} not found")

    entries = (
        db.query(LegalDocumentApprovalDB)
        .filter(LegalDocumentApprovalDB.version_id == version_id)
        .order_by(LegalDocumentApprovalDB.created_at.asc())
        .all()
    )
    return [
        ApprovalHistoryEntry(
            id=str(e.id),
            version_id=str(e.version_id),
            action=e.action,
            approver=e.approver,
            comment=e.comment,
            created_at=e.created_at,
        )
        for e in entries
    ]