-- Migration: Document enhancements for file paths, positions, and kanban type
-- Adds path column for Google Drive-like unique paths
-- Adds position column for file ordering within folders
-- Extends type enum to include 'kanban' for kanban boards as files

-- Add path column (computed from parent hierarchy)
ALTER TABLE documents ADD COLUMN IF NOT EXISTS path TEXT;

-- Add position column for ordering files within a folder
ALTER TABLE documents ADD COLUMN IF NOT EXISTS position INTEGER DEFAULT 0;

-- Update the type constraint to allow 'kanban'
-- First drop the existing constraint if it exists
ALTER TABLE documents DROP CONSTRAINT IF EXISTS documents_type_check;

-- Add new constraint with kanban type
ALTER TABLE documents ADD CONSTRAINT documents_type_check 
  CHECK (type IN ('folder', 'document', 'kanban'));

-- Function to compute and update document path
CREATE OR REPLACE FUNCTION compute_document_path(doc_id UUID)
RETURNS TEXT AS $$
DECLARE
  result TEXT := '';
  current_doc RECORD;
  path_parts TEXT[] := '{}';
BEGIN
  -- Start with the document itself
  SELECT * INTO current_doc FROM documents WHERE id = doc_id;
  
  IF NOT FOUND THEN
    RETURN NULL;
  END IF;
  
  -- Build path from document up to root
  WHILE current_doc IS NOT NULL LOOP
    path_parts := array_prepend(current_doc.name, path_parts);
    
    IF current_doc.parent_id IS NULL THEN
      EXIT;
    END IF;
    
    SELECT * INTO current_doc FROM documents WHERE id = current_doc.parent_id;
  END LOOP;
  
  -- Join with '/' separator
  result := '/' || array_to_string(path_parts, '/');
  
  RETURN result;
END;
$$ LANGUAGE plpgsql;

-- Function to update path on insert/update
CREATE OR REPLACE FUNCTION update_document_path()
RETURNS TRIGGER AS $$
BEGIN
  NEW.path := compute_document_path(NEW.id);
  RETURN NEW;
END;
$$ LANGUAGE plpgsql;

-- Trigger to auto-update path
DROP TRIGGER IF EXISTS documents_path_trigger ON documents;
CREATE TRIGGER documents_path_trigger
  BEFORE INSERT OR UPDATE OF name, parent_id ON documents
  FOR EACH ROW
  EXECUTE FUNCTION update_document_path();

-- Function to get next position in folder
CREATE OR REPLACE FUNCTION get_next_document_position(folder_id UUID)
RETURNS INTEGER AS $$
DECLARE
  max_pos INTEGER;
BEGIN
  SELECT COALESCE(MAX(position), -1) + 1 INTO max_pos
  FROM documents
  WHERE parent_id IS NOT DISTINCT FROM folder_id;
  
  RETURN max_pos;
END;
$$ LANGUAGE plpgsql;

-- Update existing documents to have computed paths
UPDATE documents SET path = compute_document_path(id) WHERE path IS NULL;

-- Update existing documents to have sequential positions within their folders
WITH numbered AS (
  SELECT id, ROW_NUMBER() OVER (PARTITION BY parent_id ORDER BY created_at) - 1 AS new_pos
  FROM documents
  WHERE position IS NULL OR position = 0
)
UPDATE documents d
SET position = n.new_pos
FROM numbered n
WHERE d.id = n.id;

-- Create index on path for faster lookups
CREATE INDEX IF NOT EXISTS idx_documents_path ON documents(path);

-- Create index on parent_id and position for faster ordering
CREATE INDEX IF NOT EXISTS idx_documents_parent_position ON documents(parent_id, position);