"""Document sharing endpoints."""
from __future__ import annotations

import uuid
from fastapi import APIRouter, Depends, HTTPException, Query, Request, status
from pydantic import BaseModel, field_validator
from sqlalchemy import select
from sqlalchemy.exc import IntegrityError
from sqlalchemy.ext.asyncio import AsyncSession

from db.models import Document, Share, User
from deps.auth import get_regular_user
from deps.db import get_db
from deps.utils import get_client_ip
from services.audit import write_audit_log

router = APIRouter(prefix="/api/shares", tags=["shares"])


class ShareCreate(BaseModel):
    document_id: str
    recipient_handle: str
    permission: str = "view"

    @field_validator("permission")
    @classmethod
    def validate_permission(cls, v: str) -> str:
        if v not in {"view", "edit"}:
            raise ValueError("permission must be 'view' or 'edit'")
        return v


class SharePermissionPatch(BaseModel):
    permission: str

    @field_validator("permission")
    @classmethod
    def validate_permission(cls, v: str) -> str:
        if v not in {"view", "edit"}:
            raise ValueError("permission must be 'view' or 'edit'")
        return v


def _parse_uuid(value: str, detail: str) -> uuid.UUID:
    try:
        return uuid.UUID(value)
    except ValueError:
        raise HTTPException(status_code=404, detail=detail)


async def _get_owned_document(
    session: AsyncSession,
    document_id: str,
    owner_id: uuid.UUID,
) -> Document:
    uid = _parse_uuid(document_id, "Document not found")
    doc = await session.get(Document, uid)
    if doc is None or doc.user_id != owner_id:
        raise HTTPException(status_code=404, detail="Document not found")
    return doc


async def _get_owned_share(
    session: AsyncSession,
    share_id: str,
    owner_id: uuid.UUID,
) -> Share:
    sid = _parse_uuid(share_id, "Share not found")
    share = await session.get(Share, sid)
    if share is None or share.owner_id != owner_id:
        raise HTTPException(status_code=404, detail="Share not found")
    return share


def _share_to_dict(share: Share, recipient: User) -> dict:
    return {
        "id": str(share.id),
        "document_id": str(share.document_id),
        "owner_id": str(share.owner_id),
        "recipient_id": str(share.recipient_id),
        "recipient_handle": recipient.handle,
        "permission": share.permission,
        "created_at": share.created_at.isoformat() if share.created_at else None,
    }


@router.post("", status_code=status.HTTP_201_CREATED)
async def grant_share(
    body: ShareCreate,
    request: Request,
    session: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_regular_user),
) -> dict:
    doc = await _get_owned_document(session, body.document_id, current_user.id)

    # Recipient lookup by exact handle (D-04)
    result = await session.execute(
        select(User).where(User.handle == body.recipient_handle)
    )
    recipient = result.scalar_one_or_none()
    if recipient is None:
        raise HTTPException(status_code=404, detail="User not found")

    # Self-share prevention
    if recipient.id == current_user.id:
        raise HTTPException(status_code=400, detail="Cannot share with yourself")

    # Create the share row
    share = Share(
        document_id=doc.id,
        owner_id=current_user.id,
        recipient_id=recipient.id,
        permission=body.permission,
    )
    session.add(share)

    try:
        await session.flush()
    except IntegrityError:
        await session.rollback()
        raise HTTPException(
            status_code=409, detail="Document already shared with this user"
        )

    # Audit log — write within same transaction (D-14)
    await write_audit_log(
        session=session,
        event_type="share.granted",
        user_id=current_user.id,
        actor_id=current_user.id,
        resource_id=doc.id,
        ip_address=get_client_ip(request),
        metadata_={"recipient_id": str(recipient.id)},
    )

    await session.commit()

    return _share_to_dict(share, recipient)


@router.get("")
async def list_shares(
    document_id: str = Query(...),
    session: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_regular_user),
) -> dict:
    doc = await _get_owned_document(session, document_id, current_user.id)

    stmt = (
        select(Share, User)
        .join(User, User.id == Share.recipient_id)
        .where(Share.document_id == doc.id)
    )
    result = await session.execute(stmt)
    items = [
        {
            "id": str(share.id),
            "recipient_id": str(share.recipient_id),
            "recipient_handle": recipient.handle,
            "permission": share.permission,
            "created_at": share.created_at.isoformat() if share.created_at else None,
        }
        for share, recipient in result.all()
    ]

    return {"items": items}


# CRITICAL: This endpoint MUST be defined BEFORE DELETE /api/shares/{share_id}.
# Defining it after would cause FastAPI to route GET /api/shares/received as
# DELETE with share_id="received" (path parameter conflict).


@router.get("/received")
async def list_shared_with_me(
    session: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_regular_user),
) -> dict:
    stmt = (
        select(Document, User)
        .join(Share, Share.document_id == Document.id)
        .join(User, User.id == Share.owner_id)
        .where(Share.recipient_id == current_user.id)
        .order_by(Document.created_at.desc())
    )
    result = await session.execute(stmt)
    rows = result.all()

    items = [
        {
            "id": str(doc.id),
            "filename": doc.filename,
            "content_type": doc.content_type,
            "size_bytes": doc.size_bytes,
            "created_at": doc.created_at.isoformat() if doc.created_at else None,
            "owner_handle": owner.handle,
        }
        for doc, owner in rows
    ]

    return {"items": items}


@router.patch("/{share_id}", status_code=200)
async def update_share_permission(
    share_id: str,
    body: SharePermissionPatch,
    request: Request,
    session: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_regular_user),
) -> dict:
    share = await _get_owned_share(session, share_id, current_user.id)
    share.permission = body.permission

    await write_audit_log(
        session=session,
        event_type="share.permission_changed",
        user_id=current_user.id,
        actor_id=current_user.id,
        resource_id=share.document_id,
        ip_address=get_client_ip(request),
        metadata_={"share_id": str(share.id), "new_permission": body.permission},
    )
    await session.commit()

    return {"id": str(share.id), "permission": share.permission}


@router.delete("/{share_id}", status_code=status.HTTP_204_NO_CONTENT)
async def revoke_share(
    share_id: str,
    request: Request,
    session: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_regular_user),
) -> None:
    share = await _get_owned_share(session, share_id, current_user.id)
    document_id = share.document_id
    recipient_id = share.recipient_id

    await session.delete(share)

    await write_audit_log(
        session=session,
        event_type="share.revoked",
        user_id=current_user.id,
        actor_id=current_user.id,
        resource_id=document_id,
        ip_address=get_client_ip(request),
        metadata_={"recipient_id": str(recipient_id)},
    )

    await session.commit()