"""DMS Folder-CRUD Routen — extrahiert aus routes.py (BUG-018 God-Object-Split)."""

from __future__ import annotations

import uuid

from fastapi import (
    APIRouter,
    Depends,
    HTTPException,
    Response,
    status,
)
from sqlalchemy import select, update
from sqlalchemy.ext.asyncio import AsyncSession

from app.core.db import get_db
from app.core.visibility import apply_visibility_filter, check_single_entity_access
from app.deps import get_current_user, require_permission, require_workspace_scope
from app.plugins.builtins.dms.common import (
    _parse_uuid,
)
from app.plugins.builtins.dms.models import File as DmsFile
from app.plugins.builtins.dms.models import Folder
from app.plugins.builtins.dms.schemas import FolderCreate, FolderUpdate
from app.plugins.builtins.permissions.contracts import get_contract as get_perms_contract

_perms_contract = get_perms_contract()
Permission = _perms_contract.Permission

router = APIRouter(tags=["dms"])

@router.get("/folders", dependencies=[Depends(require_permission("dms:read"))])
async def list_folders(
    parent_id: str | None = None,
    db: AsyncSession = Depends(get_db),
    current_user: dict = Depends(get_current_user),
    workspace_scope: dict | None = Depends(require_workspace_scope("dms")),
):
    """AC1: GET /api/v1/dms/folders → 200 + folder tree (recursive).

    Phase N3: an active workspace scope (X-Workspace-ID) reduces the tree to
    the folder subtree — pure AND-restriction, never a grant.
    """
    tenant_id = uuid.UUID(current_user["tenant_id"])

    # Fetch all non-deleted folders for tenant with visibility filter
    user_id = uuid.UUID(current_user["user_id"])
    is_system_admin = current_user.get("role") == "admin"
    query = select(Folder).where(
        Folder.tenant_id == tenant_id,
        Folder.deleted_at.is_(None),
    )
    query = await apply_visibility_filter(
        db, query, "dms_folder", Folder, user_id, tenant_id, is_system_admin
    )
    result = await db.execute(query)
    all_folders = result.scalars().all()

    # Phase N3: reduce to the scope subtree (folder_ids dimension)
    if workspace_scope:
        from app.services.workspace_scope_service import expand_folder_scope

        scope_folder_ids = workspace_scope.get("folder_ids")
        if isinstance(scope_folder_ids, list) and scope_folder_ids:
            subtree = await expand_folder_scope(db, Folder, scope_folder_ids)
            allowed = subtree or set()
            all_folders = [f for f in all_folders if f.id in allowed]

    # Build lookup map
    folder_map: dict[uuid.UUID, dict] = {}
    for f in all_folders:
        folder_map[f.id] = {
            "id": str(f.id),
            "name": f.name,
            "parent_id": str(f.parent_id) if f.parent_id else None,
            "created_by": str(f.created_by),
            "deleted_at": None,
            "path": "",
            "children": [],
        }

    # Build path for each folder
    def _build_path(folder_id: uuid.UUID) -> str:
        if folder_id not in folder_map:
            return ""
        f = folder_map[folder_id]
        if f["parent_id"] and uuid.UUID(f["parent_id"]) in folder_map:
            parent_path = _build_path(uuid.UUID(f["parent_id"]))
            return f"{parent_path}/{f['name']}"
        return f["name"]

    for fid in folder_map:
        folder_map[fid]["path"] = _build_path(fid)

    # Build tree
    root_nodes: list[dict] = []
    target_parent: uuid.UUID | None = None
    if parent_id is not None:
        target_parent = _parse_uuid(parent_id, "parent_id")

    for f in all_folders:
        node = folder_map[f.id]
        if f.parent_id is not None and f.parent_id in folder_map:
            folder_map[f.parent_id]["children"].append(node)
        elif f.parent_id is None:
            root_nodes.append(node)

    if target_parent is not None:
        # Return children of specified parent
        parent_node = folder_map.get(target_parent)
        if parent_node is None:
            raise HTTPException(
                404, detail={"detail": "Parent folder not found", "code": "not_found"}
            )
        return parent_node["children"]

    return root_nodes


@router.post("/folders", status_code=status.HTTP_201_CREATED, dependencies=[Depends(require_permission("dms:write"))])
async def create_folder(
    body: FolderCreate,
    db: AsyncSession = Depends(get_db),
    current_user: dict = Depends(get_current_user),
):
    """AC2: POST /api/v1/dms/folders → 201, folder created with path."""
    tenant_id = uuid.UUID(current_user["tenant_id"])
    user_id = uuid.UUID(current_user["user_id"])
    parent_id = _parse_uuid(body.parent_id, "parent_id") if body.parent_id else None

    # Validate parent exists if specified
    if parent_id is not None:
        parent_result = await db.execute(
            select(Folder).where(
                Folder.id == parent_id,
                Folder.tenant_id == tenant_id,
                Folder.deleted_at.is_(None),
            )
        )
        if parent_result.scalar_one_or_none() is None:
            raise HTTPException(
                404, detail={"detail": "Parent folder not found", "code": "not_found"}
            )

    # Check name uniqueness within same parent (non-deleted)
    existing = await db.execute(
        select(Folder).where(
            Folder.tenant_id == tenant_id,
            Folder.name == body.name,
            Folder.parent_id == parent_id if parent_id else Folder.parent_id.is_(None),
            Folder.deleted_at.is_(None),
        )
    )
    if existing.scalar_one_or_none() is not None:
        raise HTTPException(
            409, detail={"detail": "Folder name already exists", "code": "duplicate"}
        )

    # Lifecycle hook: dms.folder.before_create
    from app.core.hooks import do_action
    await do_action("dms.folder.before_create", body, db=db, tenant_id=tenant_id, user_id=user_id)

    folder = Folder(
        tenant_id=tenant_id,
        name=body.name,
        parent_id=parent_id,
        created_by=user_id,
    )
    db.add(folder)
    await db.flush()

    # Lifecycle hook: dms.folder.after_create
    await do_action("dms.folder.after_create", {'id': str(folder.id), 'name': folder.name, 'parent_id': str(folder.parent_id) if folder.parent_id else None}, db=db, tenant_id=tenant_id, user_id=user_id)

    # Build path
    path = body.name
    if parent_id is not None:
        parent_path_result = await db.execute(select(Folder).where(Folder.id == parent_id))
        parent_folder = parent_path_result.scalar_one_or_none()
        if parent_folder:
            # Recursively build path
            path_parts = [body.name]
            current = parent_folder
            while current is not None:
                path_parts.insert(0, current.name)
                if current.parent_id is not None:
                    cur_result = await db.execute(
                        select(Folder).where(Folder.id == current.parent_id)
                    )
                    current = cur_result.scalar_one_or_none()
                else:
                    current = None
            path = "/".join(path_parts)

    return {
        "id": str(folder.id),
        "name": folder.name,
        "parent_id": str(folder.parent_id) if folder.parent_id else None,
        "created_by": str(folder.created_by),
        "deleted_at": None,
        "path": path,
        "children": [],
    }


@router.patch("/folders/{folder_id}", dependencies=[Depends(require_permission("dms:write"))])
async def update_folder(
    folder_id: str,
    body: FolderUpdate,
    db: AsyncSession = Depends(get_db),
    current_user: dict = Depends(get_current_user),
):
    """AC3: PATCH /api/v1/dms/folders/{id} → 200, rename/move."""
    tenant_id = uuid.UUID(current_user["tenant_id"])
    user_id = uuid.UUID(current_user["user_id"])
    is_system_admin = current_user.get("role") == "admin"
    fid = _parse_uuid(folder_id, "folder_id")

    result = await db.execute(
        select(Folder).where(
            Folder.id == fid,
            Folder.tenant_id == tenant_id,
            Folder.deleted_at.is_(None),
        )
    )
    folder = result.scalar_one_or_none()
    if folder is None:
        raise HTTPException(404, detail={"detail": "Folder not found", "code": "not_found"})

    if not await check_single_entity_access(db, "dms_folder", fid, user_id, tenant_id, "write", is_system_admin):
        raise HTTPException(403, detail={"detail": "Access denied", "code": "forbidden"})

    data = body.model_dump(exclude_unset=True)

    if "name" in data and data["name"] is not None:
        # Check uniqueness if name is changing
        new_parent_id = folder.parent_id
        if "parent_id" in data and data["parent_id"] is not None:
            new_parent_id = _parse_uuid(data["parent_id"], "parent_id")

        dup = await db.execute(
            select(Folder).where(
                Folder.tenant_id == tenant_id,
                Folder.name == data["name"],
                Folder.id != fid,
                Folder.parent_id == new_parent_id if new_parent_id else Folder.parent_id.is_(None),
                Folder.deleted_at.is_(None),
            )
        )
        if dup.scalar_one_or_none() is not None:
            raise HTTPException(
                409, detail={"detail": "Folder name already exists", "code": "duplicate"}
            )
        folder.name = data["name"]

    if "parent_id" in data:
        new_parent = _parse_uuid(data["parent_id"], "parent_id") if data["parent_id"] else None
        if new_parent is not None:
            # Validate parent exists and not creating a cycle
            if new_parent == fid:
                raise HTTPException(
                    400, detail={"detail": "Cannot move folder into itself", "code": "invalid_move"}
                )

            parent_result = await db.execute(
                select(Folder).where(
                    Folder.id == new_parent,
                    Folder.tenant_id == tenant_id,
                    Folder.deleted_at.is_(None),
                )
            )
            if parent_result.scalar_one_or_none() is None:
                raise HTTPException(
                    404, detail={"detail": "Parent folder not found", "code": "not_found"}
                )

            # Check for cycle: ensure new_parent is not a descendant of folder
            async def _is_descendant(ancestor_id: uuid.UUID, descendant_id: uuid.UUID) -> bool:
                cur_result = await db.execute(select(Folder).where(Folder.id == descendant_id))
                cur = cur_result.scalar_one_or_none()
                while cur is not None and cur.parent_id is not None:
                    if cur.parent_id == ancestor_id:
                        return True
                    p_result = await db.execute(select(Folder).where(Folder.id == cur.parent_id))
                    cur = p_result.scalar_one_or_none()
                return False

            if await _is_descendant(fid, new_parent):
                raise HTTPException(
                    400,
                    detail={
                        "detail": "Cannot move folder into its own descendant",
                        "code": "invalid_move",
                    },
                )

        folder.parent_id = new_parent

    await db.flush()

    # Build path
    path_parts = [folder.name]
    current_id = folder.parent_id
    while current_id is not None:
        cur_result = await db.execute(select(Folder).where(Folder.id == current_id))
        cur = cur_result.scalar_one_or_none()
        if cur is None:
            break
        path_parts.insert(0, cur.name)
        current_id = cur.parent_id
    path = "/".join(path_parts)

    return {
        "id": str(folder.id),
        "name": folder.name,
        "parent_id": str(folder.parent_id) if folder.parent_id else None,
        "created_by": str(folder.created_by),
        "deleted_at": None,
        "path": path,
        "children": [],
    }


@router.delete("/folders/{folder_id}", status_code=status.HTTP_204_NO_CONTENT, dependencies=[Depends(require_permission("dms:delete"))])
async def delete_folder(
    folder_id: str,
    db: AsyncSession = Depends(get_db),
    current_user: dict = Depends(get_current_user),
):
    """AC4: DELETE /api/v1/dms/folders/{id} → 204, soft-delete with cascade."""
    tenant_id = uuid.UUID(current_user["tenant_id"])
    user_id = uuid.UUID(current_user["user_id"])
    is_system_admin = current_user.get("role") == "admin"
    fid = _parse_uuid(folder_id, "folder_id")

    result = await db.execute(
        select(Folder).where(
            Folder.id == fid,
            Folder.tenant_id == tenant_id,
            Folder.deleted_at.is_(None),
        )
    )
    folder = result.scalar_one_or_none()
    if folder is None:
        raise HTTPException(404, detail={"detail": "Folder not found", "code": "not_found"})

    if not await check_single_entity_access(db, "dms_folder", fid, user_id, tenant_id, "delete", is_system_admin):
        raise HTTPException(403, detail={"detail": "Access denied", "code": "forbidden"})

    # Lifecycle hook: dms.folder.before_delete
    from app.core.hooks import do_action
    await do_action("dms.folder.before_delete", db=db, tenant_id=tenant_id, user_id=user_id, folder_id=str(fid))

    from datetime import UTC, datetime

    now = datetime.now(UTC)

    # Recursively collect all descendant folder IDs
    all_folder_ids: list[uuid.UUID] = [fid]
    queue: list[uuid.UUID] = [fid]
    while queue:
        current_id = queue.pop(0)
        children_result = await db.execute(
            select(Folder).where(
                Folder.parent_id == current_id,
                Folder.tenant_id == tenant_id,
                Folder.deleted_at.is_(None),
            )
        )
        for child in children_result.scalars().all():
            all_folder_ids.append(child.id)
            queue.append(child.id)

    # Soft-delete all folders
    await db.execute(update(Folder).where(Folder.id.in_(all_folder_ids)).values(deleted_at=now))

    # Soft-delete all files in those folders
    await db.execute(
        update(DmsFile)
        .where(
            DmsFile.tenant_id == tenant_id,
            DmsFile.folder_id.in_(all_folder_ids),
            DmsFile.deleted_at.is_(None),
        )
        .values(deleted_at=now)
    )

    await db.flush()

    # Lifecycle hook: dms.folder.after_delete
    from app.core.hooks import do_action
    await do_action("dms.folder.after_delete", db=db, tenant_id=tenant_id, user_id=user_id, folder_id=str(fid))

    return Response(status_code=status.HTTP_204_NO_CONTENT)


# ─── Files ───