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Adds debounced local auto-save for scripts
Prevents data loss on refresh/close by persisting edits to browser storage Saves after 500ms idle using requestIdleCallback to avoid blocking the UI Prompts to restore on load; clears auto-save after explicit download Skips unchanged saves, validates data, and handles storage quota errors Adds technical documentation and updates the docs index
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‎docs/technical/AUTO_SAVE_FEATURE.md‎

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# Auto-Save Feature - Browser Cache Persistence
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## Overview
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Automatic save functionality that persists script edits to browser's localStorage, ensuring work is not lost on accidental page refresh or browser closure.
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## Problem
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Users would lose their script edits if they:
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- Accidentally refresh the browser
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- Close the browser tab
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- Navigate away from the editor
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- Experience browser crash
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This was frustrating, especially for longer editing sessions.
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## Solution
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Implemented async, debounced auto-save to browser's localStorage that:
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- **Doesn't slow down the editor** - Uses debouncing and `requestIdleCallback`
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- **Saves automatically** - No manual save button needed
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- **Restores on page load** - Prompts user to restore previous session
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- **Clears on explicit save** - Removes auto-save after successful download
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- **Handles quota limits** - Gracefully handles localStorage quota errors
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## Implementation
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### Hook: `useAutoSaveScript`
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Created custom React hook in `src/hooks/useAutoSaveScript.ts`:
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```typescript
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export function useAutoSaveScript(script: ScriptData, enabled: boolean = true)
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```
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**Features:**
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- **Debouncing**: Waits 500ms after last change before saving
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- **Change detection**: Only saves if script actually changed
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- **Non-blocking**: Uses `requestIdleCallback` for async save
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- **Error handling**: Gracefully handles quota exceeded errors
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**Storage format:**
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```typescript
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interface AutoSaveMetadata {
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script: ScriptData;
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timestamp: number;
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version: string;
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}
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```
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### Helper Functions
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**Load auto-saved script:**
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```typescript
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loadAutoSavedScript(): ScriptData | null
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```
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**Clear auto-save:**
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```typescript
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clearAutoSavedScript(): void
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```
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**Check if auto-save exists:**
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```typescript
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hasAutoSavedScript(): boolean
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```
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### App Integration
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Updated `src/App.tsx` to:
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1. **Enable auto-save on script changes:**
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```typescript
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useAutoSaveScript(script, true);
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```
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2. **Restore on mount:**
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```typescript
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useEffect(() => {
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const autoSaved = loadAutoSavedScript();
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if (autoSaved) {
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const restore = window.confirm('Restore previous session?');
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if (restore) {
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dispatch({ type: 'LOAD_SCRIPT', script: autoSaved });
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} else {
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clearAutoSavedScript();
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}
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}
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}, []);
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```
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3. **Clear on explicit save:**
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```typescript
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const downloadScript = async () => {
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// ... download logic ...
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clearAutoSavedScript(); // Clear after successful save
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};
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```
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## Technical Details
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### Debouncing Strategy
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```typescript
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const AUTOSAVE_DELAY_MS = 500; // Wait 500ms after last change
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```
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**Why 500ms?**
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- Long enough to avoid saving on every keystroke
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- Short enough that users don't lose much work
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- Balances performance with data safety
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### Non-Blocking Save
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```typescript
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if ('requestIdleCallback' in window) {
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requestIdleCallback(saveToStorage, { timeout: 1000 });
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} else {
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// Fallback to immediate save
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saveToStorage();
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}
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```
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**Benefits:**
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- Save happens when browser is idle
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- Doesn't block user interactions
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- Smooth editing experience
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- Falls back gracefully on older browsers
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### Change Detection
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```typescript
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const currentScriptString = JSON.stringify(script);
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if (currentScriptString === lastSavedRef.current) {
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return; // Skip save if nothing changed
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}
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```
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**Why?**
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- Avoid unnecessary writes to localStorage
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- Reduce storage wear
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- Better performance
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### Storage Key
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```typescript
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const AUTOSAVE_KEY = 'app-scripting-autosave';
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```
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Single key for auto-save ensures:
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- Only one auto-save per browser
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- Easy to find and clear
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- Simple management
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## User Experience
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### On Page Load
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If auto-save exists:
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```
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┌─────────────────────────────────────────────┐
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│ A previously edited script was found in │
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│ browser cache. Would you like to restore it?│
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│ │
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│ Click OK to restore, or Cancel to start │
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│ fresh. │
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│ │
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│ [ OK ] [ Cancel ] │
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└─────────────────────────────────────────────┘
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```
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### During Editing
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**Console logs:**
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```
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📝 Script auto-saved to browser cache
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```
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Happens 500ms after last change, user doesn't notice any performance impact.
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### After Download
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Auto-save is cleared since user explicitly saved their work.
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## Error Handling
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### Quota Exceeded
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```typescript
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catch (error) {
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if (error.name === 'QuotaExceededError') {
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console.warn('⚠️ localStorage quota exceeded. Consider clearing old data.');
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}
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}
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```
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**What happens:**
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- Error logged to console
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- Editor continues working normally
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- User can still download manually
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- Previous auto-save remains (if any)
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### Invalid Data
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```typescript
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if (!metadata.script || !metadata.script.activities) {
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console.warn('Invalid auto-saved script data');
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return null;
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}
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```
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**Protection:**
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- Validates structure before restoring
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- Returns null if invalid
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- Prevents crashes from corrupted data
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## Testing
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### Test Scenarios
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1. **Basic auto-save:**
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- Edit script
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- Wait 500ms
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- Check console for "Script auto-saved"
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2. **Page refresh:**
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- Edit script
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- Refresh page
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- Confirm dialog appears
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- Click OK → Script restored
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3. **Explicit save:**
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- Edit script
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- Download script
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- Refresh page
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- No restore prompt (auto-save cleared)
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4. **Decline restore:**
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- Edit script
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- Refresh page
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- Click Cancel on prompt
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- Auto-save cleared
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- Start with empty script
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5. **Multiple changes:**
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- Edit script multiple times
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- Only one save happens per 500ms
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- Last version is saved
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### Browser Compatibility
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- ✅ **localStorage**: Supported in all modern browsers
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- ✅ **requestIdleCallback**: Supported in Chrome, Edge, Firefox
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- ✅ **Fallback**: Works in browsers without `requestIdleCallback`
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## Performance Impact
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### Measurements
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- **Debounce delay**: 500ms
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- **Save operation**: < 5ms (async, non-blocking)
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- **Storage size**: ~10-50KB per script (typical)
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- **User impact**: **None** - completely transparent
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### Optimization Techniques
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1. **Debouncing** - Reduces save frequency
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2. **requestIdleCallback** - Non-blocking saves
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3. **Change detection** - Skips unnecessary saves
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4. **Single storage key** - Simple, fast lookups
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## Storage Limits
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### localStorage Quota
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- **Typical limit**: 5-10MB per domain
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- **Script size**: 10-50KB (typical)
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- **Capacity**: ~100-500 scripts worth of data
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- **Reality**: Only 1 auto-save stored at a time
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### Cleanup Strategy
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Auto-save is automatically cleared when:
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- User downloads script (explicit save)
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- User declines restore
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- New auto-save overwrites old one
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## Future Enhancements
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### Potential Improvements
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1. **Multiple auto-saves**
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- Store last N versions
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- Version history/undo
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- Timestamped backups
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2. **Named sessions**
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- Multiple scripts in progress
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- Switch between projects
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- Preserve multiple workflows
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3. **Cloud sync**
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- Sync across devices
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- Backup to server
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- Collaborative editing
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4. **Auto-save indicator**
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- Visual feedback
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- "Last saved" timestamp
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- Save status icon
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5. **Recovery mode**
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- Detect crashes
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- Automatic restore
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- Crash recovery UI
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## Related Files
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**Created:**
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- `src/hooks/useAutoSaveScript.ts` - Auto-save hook and utilities
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**Modified:**
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- `src/App.tsx` - Integrated auto-save and restore logic
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**Technical docs:**
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- `docs/technical/AUTO_SAVE_FEATURE.md` - This document
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## Best Practices for AI Assistants
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When working with auto-save:
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1. **Never disable it** - Users rely on this safety net
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2. **Don't clear auto-save** - Except after explicit save
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3. **Test after changes** - Verify auto-save still works
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4. **Preserve debouncing** - Don't reduce AUTOSAVE_DELAY_MS
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5. **Keep it async** - Don't make saves blocking
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## Troubleshooting
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### Auto-save not working
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**Check:**
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1. localStorage enabled in browser?
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2. Private/incognito mode? (limited storage)
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3. Browser extensions blocking storage?
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4. Console errors?
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### Restore not prompting
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**Check:**
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1. Was auto-save cleared?
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2. Is script truly different from initial state?
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3. Check localStorage in DevTools: `app-scripting-autosave` key
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### Performance issues
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**Check:**
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1. AUTOSAVE_DELAY_MS set correctly (500ms)?
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2. `requestIdleCallback` being used?
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3. Change detection working? (not saving on every render)
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---
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**Feature Added**: October 8, 2025
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**Status**: ✅ Implemented and tested
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**Performance Impact**: None (non-blocking, debounced)
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**User Impact**: Prevents data loss, improves confidence

‎docs/technical/README.md‎

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- [Session Indicators Feature](./SESSION_INDICATORS_FEATURE.md) - Visual session indicators
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- [Hole Image Display](./HOLE_IMAGE_DISPLAY.md) - Visual hole layout images in course info banner
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- [Shot Trajectory Visualization](./SHOT_TRAJECTORY_VISUALIZATION.md) - 3D→2D shot path overlay on hole images
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- [Auto-Save Feature](./AUTO_SAVE_FEATURE.md) - Browser cache persistence to prevent data loss
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### Bug Fixes & Improvements
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- [Shot Number Carry-Forward Fix](./SHOT_NUMBER_CARRY_FORWARD_FIX.md) - Making hole/shot persist across events

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