FlowRedux State Management Refactoring

For concrete examples and code samples, see examples.md.

Instructions

When a developer provides Android/KMP code with complex state management, follow these steps:

Phase 1: Comprehensive Feature Analysis (CRITICAL - DO NOT SKIP)

1.1 UI Inventory - Map All Interactive Elements Before any refactoring, create a complete inventory:

• ✅ List every button, toggle, input field, and clickable element
• ✅ Document every menu option, dropdown, dialog, and bottom sheet
• ✅ Identify swipe gestures, long-press actions, and other interactions
• ✅ Note system events (lifecycle, network changes, permissions)

Output: A checklist of ALL user actions this screen supports.

1.2 Data Flow Mapping

• Map all data sources (API, database, cache, shared preferences)
• Trace data transformations and business logic
• Identify all async operations and their dependencies
• Document error scenarios for each data operation

1.3 State Transition Graph Create a comprehensive state diagram showing:

• All possible states the screen can be in
• Triggers for each state transition (user actions, events, responses)
• Invalid state transitions that should be prevented
• Edge cases and race conditions

Output: A complete state machine diagram or table.

Phase 2: Test-Driven Design (TDD Approach)

2.1 Design Test Cases First Before writing ANY implementation code:

• Write test cases for EVERY user action identified in Phase 1
• Write test cases for EVERY state transition
• Write test cases for error scenarios and edge cases
• Write test cases for concurrent actions (e.g., delete while loading)

2.2 Test Case Format

@Test
fun `when [action] in [current state], should transition to [expected state]`() {
    // Given: initial state
    // When: action occurs
    // Then: verify new state
}

2.3 Leverage MVI Observability Use the state machine's deterministic nature:

• Every action → state transition is predictable and testable
• No hidden state or side effects
• Time-travel debugging possible
• Easy to reproduce bugs by replaying actions

Output: Complete test suite BEFORE implementation.

Phase 3: Implement State Machine

3.1 Define Components Based on Analysis

• Create State sealed class covering ALL states from Phase 1
• Create Action sealed class for ALL user actions and events
• Create SideEffect handlers for async operations
• Ensure every test case from Phase 2 is covered

3.2 Implement State Transitions

• Write reducers for each state transition
• Implement side effect handlers with proper error handling
• Ensure all edge cases from test suite are handled

3.3 Verify Against Tests

• Run test suite continuously during implementation
• Use failing tests to discover missing functionality
• Refactor until all tests pass

Phase 4: Bug Detection via Tests

4.1 Test-Driven Bug Finding When bugs are discovered:

• Write a failing test that reproduces the bug
• Fix the state machine to make the test pass
• Verify no regression in existing tests

4.2 Missing Functionality Detection Use test coverage to find:

• Unhandled user actions
• Missing state transitions
• Unhandled error cases
• Race conditions

Phase 5: Code Generation & Documentation

5.1 Generate Complete Implementation

• All State, Action, and SideEffect sealed classes
• Complete state machine with all transitions
• Full test suite with explanations
• Integration guide for ViewModel

5.2 Provide Traceability

• Map each test case back to original requirements
• Document which states/actions handle which UI elements
• Create a state transition reference table

Examples

See examples.md for detailed code examples including:

• Simple list loading (before/after comparison)
• Complex multi-action scenarios (pagination, deletion, sorting)
• Complete test suites
• Common patterns and anti-patterns
• Migration guide

Key Principles

1. Feature-First Analysis: Map ALL UI elements and interactions before coding
2. State Machine Design: Create complete state transition graph upfront
3. Test-Driven Development: Write tests BEFORE implementation
4. MVI Observability: Leverage deterministic state transitions for testing
5. Bug Prevention: Use failing tests to drive bug fixes and find missing features
6. Single Source of Truth: All state in one place
7. Immutability: States are immutable data classes
8. Type Safety: Sealed classes prevent invalid states

Engineering Best Practices

Practice 1: Comprehensive Feature Inventory

Before writing any code:

## Feature Checklist
- [ ] Load videos button
- [ ] Pull to refresh
- [ ] Delete video (with swipe)
- [ ] Undo delete
- [ ] Play video
- [ ] Sort options (date, title)
- [ ] Filter (watched/unwatched)
- [ ] Empty state
- [ ] Error retry
- [ ] Offline mode indicator

Why: Ensures no functionality is missed in refactoring.

Practice 2: State Transition Table

Create before implementation:

| Current State | Action         | Next State      | Side Effect       |
|---------------|----------------|-----------------|-------------------|
| Initial       | Load           | Loading         | Fetch from API    |
| Loading       | Success        | Content         | None              |
| Loading       | Error          | Error           | None              |
| Content       | Refresh        | Refreshing      | Fetch from API    |
| Content       | Delete(id)     | Content         | Delete from DB    |
| Content       | Sort(type)     | Content         | Resort locally    |

Why: Makes state machine design explicit and reviewable.

Practice 3: Test-First Development

Write tests before implementation:

class WatchLaterStateMachineTest {
    @Test
    fun `given Initial, when Load action, should transition to Loading`() {
        val machine = createStateMachine()
        machine.dispatchAction(Action.Load)
        assertEquals(State.Loading, machine.state.value)
    }

    @Test
    fun `given Loading, when data arrives, should transition to Content`() {
        // Test the actual behavior
    }

    @Test
    fun `given Content with items, when Delete action, should remove item optimistically`() {
        // Test optimistic update
    }

    @Test
    fun `given two simultaneous Delete actions, should handle race condition`() {
        // Test edge cases
    }
}

Why: Tests document expected behavior and catch regressions.

Practice 4: Use Tests to Find Missing Features

When reviewing implementation:

// Run test coverage report
// Missing coverage = missing functionality

@Test
fun `when offline and user triggers refresh, should show offline message`() {
    // This test fails? → Feature is missing!
}

@Test  
fun `when deleting last item, should show empty state`() {
    // This test fails? → Edge case not handled!
}

Why: Test-driven approach reveals gaps in requirements.

Common Patterns

Pattern: Retry Logic

See examples.md for detailed pattern implementations.

Pattern: Optimistic Updates

See examples.md for detailed pattern implementations.

Pattern: Side Effect with Error Handling

See examples.md for detailed pattern implementations.

Output Format

For each refactoring request, provide:

1. Feature Analysis:

   • Complete UI element inventory
   • User action checklist
   • System event list

2. Data Flow Diagram:

   • All data sources and destinations
   • Transformation pipeline
   • Error scenarios

3. State Machine Design:

   • State transition table or diagram
   • All states, actions, and side effects listed
   • Edge cases and race conditions identified

4. Test Suite (MUST PROVIDE BEFORE IMPLEMENTATION):

   • Test cases for every user action
   • Test cases for every state transition
   • Test cases for error scenarios
   • Test cases for edge cases and race conditions

5. Implementation Code:

   • All sealed classes (State, Action, SideEffect)
   • Complete state machine implementation
   • Proper error handling and coroutine management

6. Integration Guide:

   • How to use in ViewModel
   • How to collect state in UI
   • Migration steps if needed

7. Test Execution Plan:

   • How to run tests
   • How to use tests to find bugs
   • How to add tests for new features

Workflow Summary

1. Analyze → List ALL features and interactions
            ↓
2. Design  → Create state transition graph
            ↓
3. Test    → Write test cases for EVERYTHING
            ↓
4. Verify  → Check test coverage matches feature list
            ↓
5. Implement → Write state machine to pass tests
            ↓
6. Debug   → Use failing tests to find/fix bugs
            ↓
7. Deliver → Provide complete, tested code

Always prefer clarity and completeness over brevity. Include proper error handling and coroutine scope management. Emphasize the test-driven approach and use of MVI's observability for quality assurance.