Langflow Component Refactoring Skill

Refactor high-complexity React components in the Langflow frontend codebase with the patterns and workflow below.

Complexity Threshold: Components with complexity > 50 (measured manually by counting conditionals, nesting levels, and lines) should be refactored before testing.

Quick Reference

Commands (run from src/frontend/)

cd src/frontend

# Lint with Biome
npm run lint

# Type checking
npm run type-check

# Run tests
npm test

Manual Complexity Assessment

Since Langflow does not have automated complexity analysis tools, assess components manually:

1. Count conditionals: Each if/else, switch/case, ternary, &&/|| chain adds +1.
2. Count nesting levels: Each level of nesting within conditionals or loops adds +1.
3. Count total lines: Target < 300 lines per component file.
4. Count state hooks: More than 5 useState calls suggests hook extraction.
5. Count effects: More than 3 useEffect calls suggests effect consolidation.

Complexity Score Interpretation

Score	Level	Action
0-25	Simple	Ready for testing
26-50	Medium	Consider minor refactoring
51-75	Complex	Refactor before testing
76-100	Very Complex	Must refactor

Core Refactoring Patterns

Pattern 1: Extract Custom Hooks

When: Component has complex state management, multiple useState/useEffect, or business logic mixed with UI.

Langflow Convention: Place hooks in a hooks/ subdirectory or alongside the component as use-<feature>.ts. Langflow uses kebab-case filenames with use- prefix.

// Before: Complex state logic in component
const FlowPage: FC = () => {
  const [nodes, setNodes] = useState<Node[]>([])
  const [edges, setEdges] = useState<Edge[]>([])
  const [buildStatus, setBuildStatus] = useState<BuildStatus>(BuildStatus.IDLE)

  // 50+ lines of state management logic...

  return <div>...</div>
}

// After: Extract to custom hook
// hooks/use-flow-state.ts
export const useFlowState = (flowId: string) => {
  const [nodes, setNodes] = useState<Node[]>([])
  const [edges, setEdges] = useState<Edge[]>([])
  const [buildStatus, setBuildStatus] = useState<BuildStatus>(BuildStatus.IDLE)

  // Related state management logic here

  return { nodes, setNodes, edges, setEdges, buildStatus, setBuildStatus }
}

// Component becomes cleaner
const FlowPage: FC = () => {
  const { nodes, setNodes, edges, setEdges } = useFlowState(flowId)
  return <div>...</div>
}

Langflow Examples:

• src/frontend/src/hooks/use-add-component.ts
• src/frontend/src/hooks/use-unsaved-changes.ts
• src/frontend/src/hooks/use-refresh-model-inputs.ts

Pattern 2: Extract Sub-Components

When: Single component has multiple UI sections, conditional rendering blocks, or repeated patterns.

Langflow Convention: Place sub-components in subdirectories or as separate files in the same directory. UI primitives go in components/ui/, domain components in components/core/, reusable components in components/common/.

// Before: Monolithic JSX with multiple sections
const GenericNode = () => {
  return (
    <div>
      {/* 100 lines of header UI */}
      {/* 100 lines of parameter fields */}
      {/* 100 lines of output handles */}
    </div>
  )
}

// After: Split into focused components
// CustomNodes/GenericNode/
//   generic-node.tsx       (orchestration only — kebab-case, descriptive name)
//   components/
//     node-header.tsx
//     node-parameters.tsx
//     node-outputs.tsx

const GenericNode = () => {
  return (
    <div>
      <NodeHeader nodeData={data} />
      <NodeParameters fields={fields} />
      <NodeOutputs outputs={outputs} />
    </div>
  )
}

Langflow Examples:

• src/frontend/src/CustomNodes/GenericNode/components/
• src/frontend/src/components/core/
• src/frontend/src/components/ui/

Pattern 3: Simplify Conditional Logic

When: Deep nesting (> 3 levels), complex ternaries, or multiple if/else chains.

// Before: Deeply nested conditionals
const getFieldComponent = (field: InputFieldType) => {
  if (field.type === "str") {
    if (field.multiline) {
      return <TextAreaComponent />
    } else if (field.password) {
      return <PasswordInput />
    } else if (field.options?.length) {
      return <Dropdown options={field.options} />
    } else {
      return <InputComponent />
    }
  } else if (field.type === "int") {
    return <IntComponent />
  } else if (field.type === "float") {
    return <FloatComponent />
  }
  return null
}

// After: Use lookup tables + early returns
const FIELD_COMPONENT_MAP: Record<string, FC<FieldProps>> = {
  int: IntComponent,
  float: FloatComponent,
  bool: ToggleComponent,
  code: CodeAreaComponent,
}

const STR_VARIANT_MAP: Record<string, FC<FieldProps>> = {
  multiline: TextAreaComponent,
  password: PasswordInput,
  options: Dropdown,
}

const getFieldComponent = (field: InputFieldType) => {
  if (field.type !== "str") {
    const Component = FIELD_COMPONENT_MAP[field.type]
    return Component ? <Component {...field} /> : null
  }

  const variant = field.multiline ? "multiline"
    : field.password ? "password"
    : field.options?.length ? "options"
    : "default"

  const Component = STR_VARIANT_MAP[variant] ?? InputComponent
  return <Component {...field} />
}

Pattern 4: Extract API/Data Logic

When: Component directly handles API calls, data transformation, or complex async operations.

Langflow Convention:

• This skill is for component decomposition, not query/mutation design.
• When refactoring data fetching, use frontend-query-mutation for query patterns, UseRequestProcessor, cache invalidation, and mutation error handling.
• Do not create thin passthrough useQuery wrappers during refactoring; only extract a custom hook when it truly orchestrates multiple queries/mutations or shared derived state.
• API hooks live in controllers/API/queries/{domain}/.

Langflow Examples:

• src/frontend/src/controllers/API/queries/flows/use-post-add-flow.ts
• src/frontend/src/controllers/API/queries/variables/use-get-global-variables.ts
• src/frontend/src/controllers/API/queries/folders/use-get-folders.ts

Pattern 5: Extract Modal/Dialog Management

When: Component manages multiple modals with complex open/close states.

Langflow Convention: Modals should be extracted with their state management.

// Before: Multiple modal states in component
const FlowToolbar = () => {
  const [showExportModal, setShowExportModal] = useState(false)
  const [showShareModal, setShowShareModal] = useState(false)
  const [showDeleteConfirm, setShowDeleteConfirm] = useState(false)
  const [showApiModal, setShowApiModal] = useState(false)
  // 5+ more modal states...
}

// After: Extract to modal management hook
type ModalType = "export" | "share" | "delete" | "api" | null

const useFlowToolbarModals = () => {
  const [activeModal, setActiveModal] = useState<ModalType>(null)

  const openModal = useCallback((type: ModalType) => setActiveModal(type), [])
  const closeModal = useCallback(() => setActiveModal(null), [])

  return {
    activeModal,
    openModal,
    closeModal,
    isOpen: (type: ModalType) => activeModal === type,
  }
}

Pattern 6: Extract Form Logic

When: Complex form validation, submission handling, or field transformation.

Langflow Convention: Extract form state and validation into hooks.

// Extract form validation and submission
const useFlowSettingsForm = (initialValues: FlowSettings) => {
  const [values, setValues] = useState(initialValues)
  const [errors, setErrors] = useState<Record<string, string>>({})

  const validate = useCallback(() => {
    const newErrors: Record<string, string> = {}
    if (!values.name?.trim()) newErrors.name = "Name is required"
    if (values.endpoint_name && !/^[a-z0-9-]+$/.test(values.endpoint_name)) {
      newErrors.endpoint_name = "Must be lowercase alphanumeric with hyphens"
    }
    setErrors(newErrors)
    return Object.keys(newErrors).length === 0
  }, [values])

  const handleChange = useCallback((field: string, value: any) => {
    setValues((prev) => ({ ...prev, [field]: value }))
  }, [])

  return { values, errors, validate, handleChange }
}

Langflow-Specific Refactoring Guidelines

1. Zustand Store Selectors

When: Component reads many values from a Zustand store, causing unnecessary re-renders.

// Before: Selecting too many values
const Component = () => {
  const flowStore = useFlowStore()
  // Component re-renders on ANY store change
}

// After: Use individual selectors
const Component = () => {
  const nodes = useFlowStore((state) => state.nodes)
  const edges = useFlowStore((state) => state.edges)
  // Component only re-renders when nodes or edges change
}

Langflow Reference: All stores in src/frontend/src/stores/ follow this selector pattern.

2. Custom Node Components

When: Refactoring flow node components (CustomNodes/GenericNode/).

Conventions:

• Keep node logic in custom hooks
• Extract parameter rendering to separate components
• Use the existing components/ subdirectory for sub-components

CustomNodes/GenericNode/
  generic-node.tsx             # Node registration and main render (kebab-case, NOT index.tsx)
  components/
    handle-render.tsx           # Handle rendering
    node-description.tsx        # Node description display
    node-input-field.tsx        # Input field rendering
    node-name.tsx               # Node name display
    node-output-field.tsx       # Output field rendering
    node-status.tsx             # Build status display

3. Flow Canvas Components

When: Refactoring components related to the flow editor canvas.

Conventions:

• @xyflow/react v12 is the canvas library
• Keep canvas event handlers separate from UI rendering
• Use useFlowStore for flow state management
• Use useFlowsManagerStore for multi-flow management

4. API Query Hook Components

When: Refactoring components that consume API data.

Conventions:

• Use existing query hooks from controllers/API/queries/
• Access UseRequestProcessor for new queries/mutations
• Use query key arrays like ["useGetGlobalVariables"] for cache management
• Cache invalidation belongs in mutation onSettled callbacks

Refactoring Workflow

Step 1: Assess Complexity

Manually count:

• Total conditionals (if/else, switch, ternary, &&/||)
• Maximum nesting depth
• Total lines of code
• Number of useState/useEffect hooks
• Number of distinct UI sections

Step 2: Plan

Create a refactoring plan based on detected features:

Detected Feature	Refactoring Action
5+ useState hooks with related state	Extract custom hook
API calls in component body	Extract to query hook
3+ event handlers with logic	Extract event handlers to hook
300+ lines	Split into sub-components
Deep conditional nesting (>3)	Simplify conditional logic
Multiple modal states	Extract modal management

Step 3: Execute Incrementally

1. Extract one piece at a time
2. Run lint, type-check, and tests after each extraction
3. Verify functionality before next step

For each extraction:
  1. Extract code
  2. Run: npm run lint
  3. Run: npm run type-check
  4. Run: npm test
  5. Test functionality manually
  6. PASS? -> Next extraction
     FAIL? -> Fix before continuing

Step 4: Verify

After refactoring, re-assess complexity manually:

• Target complexity < 50
• Target line count < 300
• Target max nesting depth <= 3
• Target max function length < 30 lines

Common Mistakes to Avoid

Over-Engineering

// Too many tiny hooks
const useButtonText = () => useState("Click")
const useButtonDisabled = () => useState(false)
const useButtonLoading = () => useState(false)

// Cohesive hook with related state
const useButtonState = () => {
  const [text, setText] = useState("Click")
  const [disabled, setDisabled] = useState(false)
  const [loading, setLoading] = useState(false)
  return { text, setText, disabled, setDisabled, loading, setLoading }
}

Breaking Existing Patterns

• Follow existing directory structures in components/ui/, components/core/, components/common/
• Maintain naming conventions (kebab-case files, PascalCase components)
• Preserve export patterns for compatibility
• Keep Zustand store selector patterns consistent

Premature Abstraction

• Only extract when there is clear complexity benefit
• Do not create abstractions for single-use code
• Keep refactored code in the same domain area

Bypassing UseRequestProcessor

• Do not call useQuery or useMutation directly for API calls
• Always use the UseRequestProcessor pattern for consistency with retry and invalidation logic
• See frontend-query-mutation skill for API hook patterns

References

Langflow Codebase Examples

• Hook extraction: src/frontend/src/hooks/
• Component splitting: src/frontend/src/CustomNodes/GenericNode/components/
• UI components: src/frontend/src/components/ui/
• Core components: src/frontend/src/components/core/
• Common components: src/frontend/src/components/common/
• API query hooks: src/frontend/src/controllers/API/queries/
• Zustand stores: src/frontend/src/stores/

Related Skills

• frontend-query-mutation - For API query and mutation patterns
• frontend-testing - For testing refactored components