resolutionflow/backend/app/api/endpoints/trees.py

from datetime import datetime, timezone
from typing import Annotated, Optional
from uuid import UUID
import secrets
from fastapi import APIRouter, Depends, HTTPException, status, Query, Request
from sqlalchemy.ext.asyncio import AsyncSession
from sqlalchemy import select, func, or_, update
from sqlalchemy.orm import selectinload

from app.core.database import get_db
from app.models.tree import Tree
from app.models.tree_share import TreeShare
from app.models.user import User
from app.models.category import TreeCategory
from app.models.tag import TreeTag, tree_tag_assignments
from app.models.folder import UserFolder, user_folder_trees
from app.schemas.tree import (
    TreeCreate, TreeUpdate, TreeResponse, TreeListResponse, CategoryInfo,
    ForkCreate, ForkInfo, TreeShareCreate, TreeShareResponse,
    TreeVisibilityUpdate, SharedTreeResponse, TreeValidationResponse, ValidationError,
    PinnedFlowResponse, PinnedFlowsListResponse, PinnedFlowReorderRequest
)
from app.models.user_pinned_tree import UserPinnedTree
from app.api.deps import get_current_active_user, require_engineer_or_admin, require_admin, get_service_account_id
from app.core.permissions import can_edit_tree, can_access_tree
from app.core.filters import build_tree_access_filter
from app.core.subscriptions import check_tree_limit
from app.core.audit import log_audit
from app.core.config import settings
from app.core.tree_validation import can_publish_tree
from app.core.step_sync import sync_steps_from_tree, deactivate_synced_steps_for_tree

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


def build_tree_response(tree: Tree, author_map: dict | None = None) -> TreeListResponse:
    """Build TreeListResponse with category_info and tags."""
    category_info = None
    if tree.category_rel:
        category_info = CategoryInfo(
            id=tree.category_rel.id,
            name=tree.category_rel.name,
            slug=tree.category_rel.slug
        )

    author_name = (author_map or {}).get(tree.author_id)

    return TreeListResponse(
        id=tree.id,
        name=tree.name,
        description=tree.description,
        tree_type=tree.tree_type,
        category=tree.category,
        category_id=tree.category_id,
        category_info=category_info,
        tags=tree.tag_names,
        author_id=tree.author_id,
        author_name=author_name,
        account_id=tree.account_id,
        is_active=tree.is_active,
        is_public=tree.is_public,
        is_default=tree.is_default,
        visibility=tree.visibility,
        status=tree.status,
        version=tree.version,
        usage_count=tree.usage_count,
        created_at=tree.created_at,
        updated_at=tree.updated_at
    )


def build_full_tree_response(tree: Tree, parent_tree: Tree = None) -> TreeResponse:
    """Build TreeResponse with all details including category_info, tags, and fork_info."""
    category_info = None
    if tree.category_rel:
        category_info = CategoryInfo(
            id=tree.category_rel.id,
            name=tree.category_rel.name,
            slug=tree.category_rel.slug
        )

    fork_info = None
    if tree.parent_tree_id or tree.fork_depth > 0:
        has_updates = False
        if parent_tree and tree.parent_updated_at:
            has_updates = parent_tree.updated_at > tree.parent_updated_at
        fork_info = ForkInfo(
            parent_tree_id=tree.parent_tree_id,
            root_tree_id=tree.root_tree_id,
            fork_reason=tree.fork_reason,
            fork_depth=tree.fork_depth,
            parent_updated_at=tree.parent_updated_at,
            has_parent_updates=has_updates
        )

    return TreeResponse(
        id=tree.id,
        name=tree.name,
        description=tree.description,
        tree_type=tree.tree_type,
        category=tree.category,
        category_id=tree.category_id,
        category_info=category_info,
        tags=tree.tag_names,
        fork_info=fork_info,
        tree_structure=tree.tree_structure,
        intake_form=tree.intake_form,
        author_id=tree.author_id,
        account_id=tree.account_id,
        is_active=tree.is_active,
        is_public=tree.is_public,
        is_default=tree.is_default,
        status=tree.status,
        version=tree.version,
        usage_count=tree.usage_count,
        created_at=tree.created_at,
        updated_at=tree.updated_at
    )


@router.get("", response_model=list[TreeListResponse])
async def list_trees(
    db: Annotated[AsyncSession, Depends(get_db)],
    current_user: Annotated[User, Depends(get_current_active_user)],
    tree_type: Optional[str] = Query(None, description="Filter by tree type: troubleshooting or procedural"),
    category: Optional[str] = Query(None, description="Filter by legacy category string"),
    category_id: Optional[UUID] = Query(None, description="Filter by category ID"),
    tags: Optional[str] = Query(None, description="Comma-separated tag slugs to filter by"),
    folder_id: Optional[UUID] = Query(None, description="Filter by folder ID (user's folders only)"),
    is_active: Optional[bool] = Query(None, description="Filter by active status"),
    author_id: Optional[UUID] = Query(None, description="Filter by author ID"),
    is_public: Optional[bool] = Query(None, description="Filter by public status"),
    visibility: Optional[str] = Query(None, description="Filter by visibility: private, team, link, public"),
    sort_by: Optional[str] = Query("usage_count", description="Sort order: usage_count, updated_at, created_at, name, name_desc, version"),
    skip: int = Query(0, ge=0),
    limit: int = Query(100, ge=1, le=100)
):
    """List all trees with optional filters.

    New filters:
    - category_id: Filter by category (from tree_categories table)
    - tags: Comma-separated tag slugs (e.g., "citrix,networking")
    - folder_id: Show only trees in a specific folder
    - sort_by: Sort order (usage_count [default], updated_at, created_at, name, name_desc, version)
    """
    query = select(Tree).options(
        selectinload(Tree.category_rel),
        selectinload(Tree.tags)
    )

    # Apply filters
    if tree_type:
        query = query.where(Tree.tree_type == tree_type)
    if category:
        query = query.where(Tree.category == category)
    if category_id:
        query = query.where(Tree.category_id == category_id)
    if is_active is not None:
        query = query.where(Tree.is_active == is_active)
    else:
        # Default to only showing active trees
        query = query.where(Tree.is_active == True)
    if author_id:
        query = query.where(Tree.author_id == author_id)
    if is_public is not None:
        query = query.where(Tree.is_public == is_public)
    if visibility:
        query = query.where(Tree.visibility == visibility)

    # Filter by tags (all specified tags must be present)
    if tags:
        tag_slugs = [t.strip() for t in tags.split(",") if t.strip()]
        for tag_slug in tag_slugs:
            query = query.where(
                Tree.tags.any(TreeTag.slug == tag_slug)
            )

    # Filter by folder
    if folder_id:
        # Verify folder belongs to user
        folder_result = await db.execute(
            select(UserFolder).where(
                UserFolder.id == folder_id,
                UserFolder.user_id == current_user.id
            )
        )
        folder = folder_result.scalar_one_or_none()
        if not folder:
            raise HTTPException(
                status_code=status.HTTP_404_NOT_FOUND,
                detail="Folder not found"
            )
        query = query.where(Tree.folders.any(UserFolder.id == folder_id))

    # Apply access filter
    query = query.where(build_tree_access_filter(current_user))

    # Apply sorting
    if sort_by == "updated_at":
        query = query.order_by(Tree.updated_at.desc())
    elif sort_by == "created_at":
        query = query.order_by(Tree.created_at.desc())
    elif sort_by == "name":
        query = query.order_by(Tree.name.asc())
    elif sort_by == "name_desc":
        query = query.order_by(Tree.name.desc())
    elif sort_by == "version":
        query = query.order_by(Tree.version.desc(), Tree.updated_at.desc())
    else:  # Default to usage_count
        query = query.order_by(Tree.usage_count.desc(), Tree.updated_at.desc())

    query = query.offset(skip).limit(limit)

    result = await db.execute(query)
    trees = result.scalars().unique().all()

    # Fetch author names in one query (avoids N+1)
    author_ids = {t.author_id for t in trees if t.author_id}
    author_map: dict = {}
    if author_ids:
        authors_result = await db.execute(
            select(User.id, User.name, User.email).where(User.id.in_(author_ids))
        )
        for row in authors_result:
            author_map[row.id] = row.name or row.email

    return [build_tree_response(tree, author_map) for tree in trees]


@router.get("/categories", response_model=list[str])
async def list_categories(
    db: Annotated[AsyncSession, Depends(get_db)],
    current_user: Annotated[User, Depends(get_current_active_user)]
):
    """List all unique categories from trees the user can access.

    Note: This returns legacy string categories. For the new category system,
    use the /categories endpoint.
    """
    query = select(Tree.category).where(
        Tree.category.isnot(None),
        Tree.is_active == True,
        build_tree_access_filter(current_user)
    ).distinct()
    result = await db.execute(query)
    categories = [row[0] for row in result.all() if row[0]]
    return sorted(categories)


# --- Pinned Flows Endpoints (must be before /{tree_id} to avoid route shadowing) ---

MAX_PINNED_FLOWS = 15


@router.get("/pinned", response_model=PinnedFlowsListResponse)
async def list_pinned_flows(
    db: Annotated[AsyncSession, Depends(get_db)],
    current_user: Annotated[User, Depends(get_current_active_user)]
):
    """List user's pinned flows, ordered by display_order."""
    result = await db.execute(
        select(UserPinnedTree, Tree)
        .join(Tree, UserPinnedTree.tree_id == Tree.id)
        .options(selectinload(Tree.category_rel))
        .where(
            UserPinnedTree.user_id == current_user.id,
            Tree.is_active == True,
            Tree.deleted_at.is_(None)
        )
        .order_by(UserPinnedTree.display_order, UserPinnedTree.pinned_at)
    )
    rows = result.all()

    items = []
    for pin, tree in rows:
        items.append(PinnedFlowResponse(
            id=pin.id,
            tree_id=tree.id,
            tree_name=tree.name,
            tree_type=tree.tree_type,
            category_emoji=None,
            category_name=tree.category_rel.name if tree.category_rel else None,
            pinned_at=pin.pinned_at,
            display_order=pin.display_order,
        ))

    return PinnedFlowsListResponse(items=items, count=len(items))


@router.patch("/pinned/reorder", response_model=PinnedFlowsListResponse)
async def reorder_pinned_flows(
    reorder_data: PinnedFlowReorderRequest,
    db: Annotated[AsyncSession, Depends(get_db)],
    current_user: Annotated[User, Depends(get_current_active_user)]
):
    """Update display_order for all pinned flows."""
    for item in reorder_data.order:
        await db.execute(
            update(UserPinnedTree)
            .where(
                UserPinnedTree.user_id == current_user.id,
                UserPinnedTree.tree_id == item.tree_id
            )
            .values(display_order=item.display_order)
        )
    await db.commit()

    # Return updated list
    result = await db.execute(
        select(UserPinnedTree, Tree)
        .join(Tree, UserPinnedTree.tree_id == Tree.id)
        .options(selectinload(Tree.category_rel))
        .where(
            UserPinnedTree.user_id == current_user.id,
            Tree.is_active == True,
            Tree.deleted_at.is_(None)
        )
        .order_by(UserPinnedTree.display_order, UserPinnedTree.pinned_at)
    )
    rows = result.all()

    items = []
    for pin, tree in rows:
        items.append(PinnedFlowResponse(
            id=pin.id,
            tree_id=tree.id,
            tree_name=tree.name,
            tree_type=tree.tree_type,
            category_emoji=None,
            category_name=tree.category_rel.name if tree.category_rel else None,
            pinned_at=pin.pinned_at,
            display_order=pin.display_order,
        ))

    return PinnedFlowsListResponse(items=items, count=len(items))


@router.get("/search", response_model=list[TreeListResponse])
async def search_trees(
    db: Annotated[AsyncSession, Depends(get_db)],
    current_user: Annotated[User, Depends(get_current_active_user)],
    q: str = Query(..., min_length=2, description="Search query"),
    limit: int = Query(20, ge=1, le=50)
):
    """Full-text search trees by name and description."""
    # Using PostgreSQL full-text search
    search_vector = func.to_tsvector('english', func.coalesce(Tree.name, '') + ' ' + func.coalesce(Tree.description, ''))
    search_query = func.plainto_tsquery('english', q)

    query = select(Tree).options(
        selectinload(Tree.category_rel),
        selectinload(Tree.tags)
    ).where(
        Tree.is_active == True,
        build_tree_access_filter(current_user),
        search_vector.op('@@')(search_query)
    ).order_by(
        func.ts_rank(search_vector, search_query).desc()
    ).limit(limit)

    result = await db.execute(query)
    trees = result.scalars().unique().all()

    return [build_tree_response(tree) for tree in trees]


@router.get("/{tree_id}", response_model=TreeResponse)
async def get_tree(
    tree_id: UUID,
    db: Annotated[AsyncSession, Depends(get_db)],
    current_user: Annotated[User, Depends(get_current_active_user)]
):
    """Get a specific tree by ID."""
    result = await db.execute(
        select(Tree)
        .options(
            selectinload(Tree.category_rel),
            selectinload(Tree.tags)
        )
        .where(Tree.id == tree_id)
    )
    tree = result.scalar_one_or_none()

    if not tree:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="Tree not found"
        )

    if not tree.is_active or not can_access_tree(current_user, tree):
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="You don't have access to this tree"
        )

    return build_full_tree_response(tree)


@router.post("", response_model=TreeResponse, status_code=status.HTTP_201_CREATED)
async def create_tree(
    tree_data: TreeCreate,
    db: Annotated[AsyncSession, Depends(get_db)],
    current_user: Annotated[User, Depends(require_engineer_or_admin)],
    service_account_id: Annotated[Optional[UUID], Depends(get_service_account_id)],
):
    """Create a new tree (engineers and admins only).

    Supports:
    - category_id: Assign to a category from tree_categories
    - tags: List of tag names to assign (creates new tags if needed)
    - status: draft or published (published requires validation)
    """
    # Validate tree if status is 'published'
    if tree_data.status == 'published':
        # Convert intake_form to dicts for validation
        intake_form_dicts = None
        if tree_data.intake_form:
            intake_form_dicts = [f.model_dump() for f in tree_data.intake_form]
        can_publish, validation_errors = can_publish_tree(
            tree_data.tree_structure,
            tree_data.name,
            tree_data.description,
            tree_type=tree_data.tree_type,
            intake_form=intake_form_dicts,
        )
        if not can_publish:
            raise HTTPException(
                status_code=status.HTTP_422_UNPROCESSABLE_ENTITY,
                detail={
                    "message": "Cannot publish tree with validation errors",
                    "errors": validation_errors
                }
            )

    # Only admins can create default/system trees
    is_default = tree_data.is_default and current_user.is_super_admin

    # Verify category exists if provided
    if tree_data.category_id:
        cat_result = await db.execute(
            select(TreeCategory).where(TreeCategory.id == tree_data.category_id)
        )
        category = cat_result.scalar_one_or_none()
        if not category:
            raise HTTPException(
                status_code=status.HTTP_404_NOT_FOUND,
                detail="Category not found"
            )
        # Check category access
        if category.account_id and category.account_id != current_user.account_id and not current_user.is_super_admin:
            raise HTTPException(
                status_code=status.HTTP_403_FORBIDDEN,
                detail="You don't have access to this category"
            )

    # Convert intake_form Pydantic models to dicts for JSONB storage
    intake_form_data = None
    if tree_data.intake_form:
        intake_form_data = [f.model_dump(exclude_none=True) for f in tree_data.intake_form]

    new_tree = Tree(
        name=tree_data.name,
        description=tree_data.description,
        category=tree_data.category,
        category_id=tree_data.category_id,
        tree_type=tree_data.tree_type,
        tree_structure=tree_data.tree_structure,
        intake_form=intake_form_data,
        author_id=service_account_id if is_default else current_user.id,
        account_id=None if is_default else current_user.account_id,
        is_public=True if is_default else tree_data.is_public,  # Default trees are always public
        is_default=is_default,
        status=tree_data.status
    )
    # Check subscription tree limit
    if not is_default and current_user.account_id:
        can_create, limit, count = await check_tree_limit(current_user.account_id, db)
        if not can_create:
            raise HTTPException(
                status_code=status.HTTP_402_PAYMENT_REQUIRED,
                detail=f"Tree limit reached ({count}/{limit}). Upgrade your plan to create more trees."
            )

    db.add(new_tree)
    await db.flush()  # Get the ID

    # Handle tags
    if tree_data.tags:
        tree_account_id = new_tree.account_id or (current_user.account_id if not current_user.is_super_admin else None)

        # Collect tags to add
        tags_to_add = []
        for tag_name in tree_data.tags:
            slug = TreeTag.slugify(tag_name)

            # Try to find existing tag
            tag_query = select(TreeTag).where(
                TreeTag.slug == slug,
                or_(
                    TreeTag.account_id.is_(None),
                    TreeTag.account_id == tree_account_id
                )
            )
            tag_result = await db.execute(tag_query)
            tag = tag_result.scalar_one_or_none()

            if not tag:
                # Create new tag
                tag = TreeTag(
                    name=tag_name,
                    slug=slug,
                    account_id=tree_account_id,
                    created_by=current_user.id
                )
                db.add(tag)
                await db.flush()

            tags_to_add.append(tag)
            tag.usage_count += 1

        # Use direct SQL insert for the junction table to avoid lazy load issues
        from app.models.tag import tree_tag_assignments
        for tag in tags_to_add:
            await db.execute(
                tree_tag_assignments.insert().values(
                    tree_id=new_tree.id,
                    tag_id=tag.id,
                    assigned_by=current_user.id
                )
            )

    await db.commit()

    # Reload with relationships
    result = await db.execute(
        select(Tree)
        .options(
            selectinload(Tree.category_rel),
            selectinload(Tree.tags)
        )
        .where(Tree.id == new_tree.id)
    )
    tree = result.scalar_one()

    return build_full_tree_response(tree)


@router.put("/{tree_id}", response_model=TreeResponse)
async def update_tree(
    tree_id: UUID,
    tree_data: TreeUpdate,
    db: Annotated[AsyncSession, Depends(get_db)],
    current_user: Annotated[User, Depends(require_engineer_or_admin)],
    service_account_id: Annotated[Optional[UUID], Depends(get_service_account_id)],
):
    """Update an existing tree (engineers and admins only).

    Supports:
    - category_id: Change category assignment
    - tags: Replace all tags on the tree
    - status: Update status (requires validation when publishing)
    """
    result = await db.execute(
        select(Tree)
        .options(
            selectinload(Tree.category_rel),
            selectinload(Tree.tags)
        )
        .where(Tree.id == tree_id)
    )
    tree = result.scalar_one_or_none()

    if not tree:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="Tree not found"
        )

    if not can_edit_tree(current_user, tree):
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="You can only edit your own trees"
        )

    # Extract tags for separate handling
    update_data = tree_data.model_dump(exclude_unset=True)
    tags_data = update_data.pop("tags", None)

    # Validate if transitioning to published status
    if "status" in update_data and update_data["status"] == 'published':
        # Get the final tree structure and name after update
        final_tree_structure = update_data.get("tree_structure", tree.tree_structure)
        final_name = update_data.get("name", tree.name)
        final_description = update_data.get("description", tree.description)
        final_tree_type = update_data.get("tree_type", tree.tree_type)
        final_intake_form = update_data.get("intake_form", tree.intake_form)

        can_publish, validation_errors = can_publish_tree(
            final_tree_structure,
            final_name,
            final_description,
            tree_type=final_tree_type,
            intake_form=final_intake_form,
        )
        if not can_publish:
            raise HTTPException(
                status_code=status.HTTP_422_UNPROCESSABLE_ENTITY,
                detail={
                    "message": "Cannot publish tree with validation errors",
                    "errors": validation_errors
                }
            )

    # Verify new category if provided
    if "category_id" in update_data and update_data["category_id"]:
        cat_result = await db.execute(
            select(TreeCategory).where(TreeCategory.id == update_data["category_id"])
        )
        category = cat_result.scalar_one_or_none()
        if not category:
            raise HTTPException(
                status_code=status.HTTP_404_NOT_FOUND,
                detail="Category not found"
            )
        if category.account_id and category.account_id != current_user.account_id and not current_user.is_super_admin:
            raise HTTPException(
                status_code=status.HTTP_403_FORBIDDEN,
                detail="You don't have access to this category"
            )

    # Update basic fields
    for field, value in update_data.items():
        setattr(tree, field, value)

    # Keep visibility and is_public in sync
    if tree_data.is_public is not None:
        if tree_data.is_public and tree.visibility not in ('public',):
            tree.visibility = 'public'
        elif not tree_data.is_public and tree.visibility == 'public':
            tree.visibility = 'team'  # downgrade from public to team

    # Increment version if tree structure changed
    if "tree_structure" in update_data:
        tree.version += 1

    # Sync steps to step library on publish transition only
    if update_data.get("status") == 'published':
        _structure = update_data.get("tree_structure", tree.tree_structure)
        _type = update_data.get("tree_type", tree.tree_type)
        _is_public = update_data.get("is_public", tree.is_public)
        await sync_steps_from_tree(
            db=db,
            tree_id=tree.id,
            tree_type=_type,
            tree_structure=_structure,
            author_id=tree.author_id,
            account_id=tree.account_id,
            is_public=_is_public,
            service_account_id=service_account_id,
        )

    # Handle tags replacement
    if tags_data is not None:
        from app.models.tag import tree_tag_assignments

        # Decrement usage count for old tags (already eagerly loaded)
        for tag in tree.tags:
            tag.usage_count = max(0, tag.usage_count - 1)

        # Delete existing tag assignments using direct SQL
        await db.execute(
            tree_tag_assignments.delete().where(
                tree_tag_assignments.c.tree_id == tree.id
            )
        )

        # Add new tags
        tree_account_id = tree.account_id or (current_user.account_id if not current_user.is_super_admin else None)
        added_tag_ids = set()

        for tag_name in tags_data:
            slug = TreeTag.slugify(tag_name)

            tag_query = select(TreeTag).where(
                TreeTag.slug == slug,
                or_(
                    TreeTag.account_id.is_(None),
                    TreeTag.account_id == tree_account_id
                )
            )
            tag_result = await db.execute(tag_query)
            tag = tag_result.scalar_one_or_none()

            if not tag:
                tag = TreeTag(
                    name=tag_name,
                    slug=slug,
                    account_id=tree_account_id,
                    created_by=current_user.id
                )
                db.add(tag)
                await db.flush()

            if tag.id not in added_tag_ids:
                await db.execute(
                    tree_tag_assignments.insert().values(
                        tree_id=tree.id,
                        tag_id=tag.id,
                        assigned_by=current_user.id
                    )
                )
                added_tag_ids.add(tag.id)
                tag.usage_count += 1

    await db.commit()

    # Reload with relationships
    result = await db.execute(
        select(Tree)
        .options(
            selectinload(Tree.category_rel),
            selectinload(Tree.tags)
        )
        .where(Tree.id == tree_id)
    )
    tree = result.scalar_one()

    return build_full_tree_response(tree)


@router.delete("/{tree_id}", status_code=status.HTTP_204_NO_CONTENT)
async def delete_tree(
    tree_id: UUID,
    db: Annotated[AsyncSession, Depends(get_db)],
    current_user: Annotated[User, Depends(require_admin)]
):
    """Soft delete a tree (admin only). Sets deleted_at timestamp and is_active=False."""
    result = await db.execute(select(Tree).where(Tree.id == tree_id))
    tree = result.scalar_one_or_none()

    if not tree:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="Tree not found"
        )

    tree.is_active = False
    tree.deleted_at = datetime.now(timezone.utc)
    tree.deleted_by = current_user.id

    # Clean up folder assignments
    await db.execute(
        user_folder_trees.delete().where(user_folder_trees.c.tree_id == tree.id)
    )

    # Decrement usage_count on associated tags (floor at 0)
    tag_ids_result = await db.execute(
        select(tree_tag_assignments.c.tag_id).where(
            tree_tag_assignments.c.tree_id == tree.id
        )
    )
    tag_ids = [row[0] for row in tag_ids_result.fetchall()]
    if tag_ids:
        await db.execute(
            update(TreeTag)
            .where(TreeTag.id.in_(tag_ids))
            .values(usage_count=func.greatest(TreeTag.usage_count - 1, 0))
        )

    # Clean up tag assignments
    await db.execute(
        tree_tag_assignments.delete().where(tree_tag_assignments.c.tree_id == tree.id)
    )

    # Deactivate any synced step library entries before deletion
    # (must happen before db.delete/commit — FK SET NULL would lose the reference)
    await deactivate_synced_steps_for_tree(db, tree.id)

    await log_audit(db, current_user.id, "tree.delete", "tree", tree.id,
                    {"tree_name": tree.name})
    await db.commit()
    return None


# --- Fork Endpoints ---


@router.post("/{tree_id}/fork", response_model=TreeResponse, status_code=status.HTTP_201_CREATED)
async def fork_tree(
    tree_id: UUID,
    fork_data: ForkCreate,
    db: Annotated[AsyncSession, Depends(get_db)],
    current_user: Annotated[User, Depends(require_engineer_or_admin)]
):
    """Fork a tree to create a personal copy.

    Engineers can fork any tree they can access (public, account, or default).
    Fork inherits tree_structure but gets new ownership.
    """
    # Load parent tree
    result = await db.execute(
        select(Tree)
        .options(selectinload(Tree.category_rel), selectinload(Tree.tags))
        .where(Tree.id == tree_id)
    )
    parent = result.scalar_one_or_none()

    if not parent:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="Tree not found"
        )

    if not can_access_tree(current_user, parent):
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="You don't have access to this tree"
        )

    # Check subscription tree limit
    if current_user.account_id:
        can_create, limit, count = await check_tree_limit(current_user.account_id, db)
        if not can_create:
            raise HTTPException(
                status_code=status.HTTP_402_PAYMENT_REQUIRED,
                detail=f"Tree limit reached ({count}/{limit}). Upgrade your plan to create more trees."
            )

    # Build fork
    fork_name = fork_data.name or f"Fork of {parent.name}"
    fork = Tree(
        name=fork_name,
        description=parent.description,
        category=parent.category,
        category_id=parent.category_id,
        tree_type=parent.tree_type,
        tree_structure=parent.tree_structure,
        intake_form=parent.intake_form,
        author_id=current_user.id,
        account_id=current_user.account_id,
        is_public=False,
        is_default=False,
        version=1,
        # Fork tracking
        parent_tree_id=parent.id,
        fork_reason=fork_data.fork_reason,
        parent_updated_at=parent.updated_at,
        # Lineage tracking
        root_tree_id=parent.root_tree_id if parent.root_tree_id else parent.id,
        fork_depth=parent.fork_depth + 1,
    )

    db.add(fork)
    await db.flush()

    await log_audit(db, current_user.id, "tree.fork", "tree", fork.id,
                    {"parent_tree_id": str(parent.id), "parent_name": parent.name,
                     "fork_reason": fork_data.fork_reason})
    await db.commit()

    # Reload with relationships
    result = await db.execute(
        select(Tree)
        .options(selectinload(Tree.category_rel), selectinload(Tree.tags))
        .where(Tree.id == fork.id)
    )
    fork = result.scalar_one()

    return build_full_tree_response(fork, parent_tree=parent)


@router.get("/{tree_id}/forks", response_model=list[TreeListResponse])
async def list_forks(
    tree_id: UUID,
    db: Annotated[AsyncSession, Depends(get_db)],
    current_user: Annotated[User, Depends(get_current_active_user)],
    skip: int = Query(0, ge=0),
    limit: int = Query(50, ge=1, le=100)
):
    """List all direct forks of a tree."""
    # Verify parent exists and user can access it
    parent_result = await db.execute(select(Tree).where(Tree.id == tree_id))
    parent = parent_result.scalar_one_or_none()

    if not parent:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="Tree not found"
        )

    if not can_access_tree(current_user, parent):
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="You don't have access to this tree"
        )

    # Query direct forks, filtered by access
    query = select(Tree).options(
        selectinload(Tree.category_rel),
        selectinload(Tree.tags)
    ).where(
        Tree.parent_tree_id == tree_id,
        Tree.is_active == True,
        build_tree_access_filter(current_user)
    ).order_by(Tree.created_at.desc()).offset(skip).limit(limit)

    result = await db.execute(query)
    forks = result.scalars().unique().all()

    return [build_tree_response(tree) for tree in forks]


@router.get("/{tree_id}/lineage", response_model=list[TreeListResponse])
async def get_tree_lineage(
    tree_id: UUID,
    db: Annotated[AsyncSession, Depends(get_db)],
    current_user: Annotated[User, Depends(get_current_active_user)]
):
    """Get the fork lineage chain from current tree back to root.

    Returns ordered list: [current tree, parent, grandparent, ..., root]
    Limited to 10 levels to prevent infinite loops.
    """
    lineage = []
    current_id = tree_id
    visited = set()
    max_depth = 10

    for _ in range(max_depth):
        if current_id is None or current_id in visited:
            break
        visited.add(current_id)

        result = await db.execute(
            select(Tree)
            .options(selectinload(Tree.category_rel), selectinload(Tree.tags))
            .where(Tree.id == current_id)
        )
        tree = result.scalar_one_or_none()

        if not tree:
            break

        lineage.append(build_tree_response(tree))
        current_id = tree.parent_tree_id

    return lineage


# --- Tree Sharing Endpoints ---


@router.post("/{tree_id}/share", response_model=TreeShareResponse, status_code=status.HTTP_201_CREATED)
async def create_tree_share(
    tree_id: UUID,
    share_data: TreeShareCreate,
    request: Request,
    db: Annotated[AsyncSession, Depends(get_db)],
    current_user: Annotated[User, Depends(get_current_active_user)]
):
    """Generate a share token for a tree.

    Requirements:
    - Tree author can always create shares
    - Account members can share trees with visibility 'team', 'link', or 'public'
    - Super admins can share any tree
    """
    # Load tree
    result = await db.execute(
        select(Tree).where(Tree.id == tree_id, Tree.is_active == True)
    )
    tree = result.scalar_one_or_none()

    if not tree:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="Tree not found"
        )

    # Check permissions
    if not can_access_tree(current_user, tree):
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="You don't have access to this tree"
        )

    # Generate unique share token
    share_token = secrets.token_urlsafe(48)  # 48 bytes -> 64 base64 chars

    # Create share
    tree_share = TreeShare(
        tree_id=tree.id,
        share_token=share_token,
        created_by=current_user.id,
        allow_forking=share_data.allow_forking,
        expires_at=share_data.expires_at
    )

    db.add(tree_share)
    await log_audit(db, current_user.id, "tree.share.create", "tree_share", tree_share.id,
                    {"tree_id": str(tree.id), "tree_name": tree.name, "allow_forking": share_data.allow_forking})
    await db.commit()
    await db.refresh(tree_share)

    # Build share URL
    base_url = str(request.base_url).rstrip('/')
    share_url = f"{base_url}/shared/{share_token}"

    return TreeShareResponse(
        id=tree_share.id,
        tree_id=tree_share.tree_id,
        share_token=tree_share.share_token,
        share_url=share_url,
        allow_forking=tree_share.allow_forking,
        created_by=tree_share.created_by,
        created_at=tree_share.created_at,
        expires_at=tree_share.expires_at
    )


@router.get("/{tree_id}/shares", response_model=list[TreeShareResponse])
async def list_tree_shares(
    tree_id: UUID,
    request: Request,
    db: Annotated[AsyncSession, Depends(get_db)],
    current_user: Annotated[User, Depends(get_current_active_user)]
):
    """List all active shares for a tree."""
    # Verify tree exists and user can access it
    result = await db.execute(
        select(Tree).where(Tree.id == tree_id)
    )
    tree = result.scalar_one_or_none()

    if not tree:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="Tree not found"
        )

    if not can_access_tree(current_user, tree):
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="You don't have access to this tree"
        )

    # Query shares
    shares_result = await db.execute(
        select(TreeShare)
        .where(TreeShare.tree_id == tree_id)
        .order_by(TreeShare.created_at.desc())
    )
    shares = shares_result.scalars().all()

    # Build responses with share URLs
    base_url = str(request.base_url).rstrip('/')
    return [
        TreeShareResponse(
            id=share.id,
            tree_id=share.tree_id,
            share_token=share.share_token,
            share_url=f"{base_url}/shared/{share.share_token}",
            allow_forking=share.allow_forking,
            created_by=share.created_by,
            created_at=share.created_at,
            expires_at=share.expires_at
        )
        for share in shares
    ]


@router.patch("/{tree_id}/visibility", response_model=TreeResponse)
async def update_tree_visibility(
    tree_id: UUID,
    visibility_data: TreeVisibilityUpdate,
    db: Annotated[AsyncSession, Depends(get_db)],
    current_user: Annotated[User, Depends(require_engineer_or_admin)]
):
    """Update tree visibility level.

    Visibility levels:
    - private: Only tree author can access
    - team: Account members can access
    - link: Anyone with a valid share token can access
    - public: All authenticated users can access
    """
    result = await db.execute(
        select(Tree).where(Tree.id == tree_id)
    )
    tree = result.scalar_one_or_none()

    if not tree:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="Tree not found"
        )

    if not can_edit_tree(current_user, tree):
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="You can only edit your own trees"
        )

    # Update visibility
    old_visibility = tree.visibility
    tree.visibility = visibility_data.visibility
    tree.is_public = (visibility_data.visibility == 'public')

    await log_audit(db, current_user.id, "tree.visibility.update", "tree", tree.id,
                    {"tree_name": tree.name, "old_visibility": old_visibility,
                     "new_visibility": visibility_data.visibility})
    await db.commit()

    # Reload with relationships
    result = await db.execute(
        select(Tree)
        .options(
            selectinload(Tree.category_rel),
            selectinload(Tree.tags)
        )
        .where(Tree.id == tree_id)
    )
    tree = result.scalar_one()

    return build_full_tree_response(tree)

# --- Tree Validation Endpoint ---


@router.post("/{tree_id}/can-publish", response_model=TreeValidationResponse)
async def check_tree_can_publish(
    tree_id: UUID,
    db: Annotated[AsyncSession, Depends(get_db)],
    current_user: Annotated[User, Depends(get_current_active_user)]
):
    """Check if a tree can be published (validation endpoint).

    Returns validation status and any errors that would prevent publishing.
    Useful for providing real-time feedback in the UI without attempting to publish.
    """
    result = await db.execute(
        select(Tree).where(Tree.id == tree_id)
    )
    tree = result.scalar_one_or_none()

    if not tree:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="Tree not found"
        )

    if not can_access_tree(current_user, tree):
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="You don't have access to this tree"
        )

    # Validate the tree
    can_publish, validation_errors = can_publish_tree(
        tree.tree_structure,
        tree.name,
        tree.description,
        tree_type=tree.tree_type,
        intake_form=tree.intake_form,
    )

    return TreeValidationResponse(
        can_publish=can_publish,
        errors=[ValidationError(**error) for error in validation_errors]
    )


@router.post("/{tree_id}/pin", response_model=PinnedFlowResponse)
async def pin_flow(
    tree_id: UUID,
    db: Annotated[AsyncSession, Depends(get_db)],
    current_user: Annotated[User, Depends(get_current_active_user)]
):
    """Pin a flow to the user's sidebar."""
    # Check tree exists and user can access it
    tree_result = await db.execute(
        select(Tree)
        .options(selectinload(Tree.category_rel))
        .where(Tree.id == tree_id, Tree.is_active == True)
    )
    tree = tree_result.scalar_one_or_none()
    if not tree:
        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="Tree not found")
    if not can_access_tree(current_user, tree):
        raise HTTPException(status_code=status.HTTP_403_FORBIDDEN, detail="You don't have access to this tree")

    # Check if already pinned (idempotent)
    existing = await db.execute(
        select(UserPinnedTree).where(
            UserPinnedTree.user_id == current_user.id,
            UserPinnedTree.tree_id == tree_id
        )
    )
    pin = existing.scalar_one_or_none()
    if pin:
        return PinnedFlowResponse(
            id=pin.id,
            tree_id=tree.id,
            tree_name=tree.name,
            tree_type=tree.tree_type,
            category_emoji=None,
            category_name=tree.category_rel.name if tree.category_rel else None,
            pinned_at=pin.pinned_at,
            display_order=pin.display_order,
        )

    # Check max pins
    count_result = await db.execute(
        select(func.count(UserPinnedTree.id)).where(
            UserPinnedTree.user_id == current_user.id
        )
    )
    count = count_result.scalar() or 0
    if count >= MAX_PINNED_FLOWS:
        raise HTTPException(
            status_code=status.HTTP_409_CONFLICT,
            detail=f"Maximum of {MAX_PINNED_FLOWS} pinned flows reached"
        )

    # Create pin
    pin = UserPinnedTree(
        user_id=current_user.id,
        tree_id=tree_id,
        display_order=count,  # Append at end
    )
    db.add(pin)
    await db.commit()
    await db.refresh(pin)

    return PinnedFlowResponse(
        id=pin.id,
        tree_id=tree.id,
        tree_name=tree.name,
        tree_type=tree.tree_type,
        category_emoji=None,
        category_name=tree.category_rel.name if tree.category_rel else None,
        pinned_at=pin.pinned_at,
        display_order=pin.display_order,
    )


@router.delete("/{tree_id}/pin")
async def unpin_flow(
    tree_id: UUID,
    db: Annotated[AsyncSession, Depends(get_db)],
    current_user: Annotated[User, Depends(get_current_active_user)]
):
    """Unpin a flow from the user's sidebar."""
    result = await db.execute(
        select(UserPinnedTree).where(
            UserPinnedTree.user_id == current_user.id,
            UserPinnedTree.tree_id == tree_id
        )
    )
    pin = result.scalar_one_or_none()
    if pin:
        await db.delete(pin)
        await db.commit()
    return {"success": True}