fix(streaming): add LRU cache limit to InitCache

[PascalThuet]

Summary

Implements a bounded LRU (Least Recently Used) cache in InitCache to prevent memory leaks during long playback sessions with multiple periods or stream switches.

Changes

InitCache.js

• Added MAX_CACHE_SIZE = 50 constant
• Implemented LRU eviction when cache exceeds limit
• Added removeStream(streamId) method for explicit cleanup
• Added getStats() method for debugging/testing
• Cache now tracks access order for proper LRU behavior

MediaPlayer.js

• Exposed getInitCache() method for testing access

samples/cache/initcache-test.html

• Comprehensive test page with 3 test modes
• Report generation for test results
• Before/after branch comparison feature

Test Results ✅

Comparison: development vs fix/initcache-lru-limit

Metric	development	This PR
Entries after 100 insertions	100 (unbounded)	50 (capped)
LRU eviction active	❌ NO	✅ YES
Memory leak risk	⚠️ YES	✅ Controlled

Test 3: Cache Overflow (Synthetic) Results

Branch: development (without fix)

Entries Inserted: 100
Max Allowed: 50
Final Entries: 100
LRU Working: ❌ NO
Overall: ❌ SOME TESTS FAILED

Branch: fix/initcache-lru-limit (with fix)

Entries Inserted: 100
Max Allowed: 50
Final Entries: 50
LRU Working: ✅ YES
Overall: ✅ ALL TESTS PASSED

Test Page

A test page is included at samples/cache/initcache-test.html with three test modes:

Test 1: Quality Switch Stress Test

• Cycles through all quality levels 10 times
• Generates many init segment loads
• Verifies cache doesn't grow unbounded

Test 2: Stream Switch Stress Test

• Switches between 3 different streams 5 times each
• Simulates multi-content playback scenarios
• Tests LRU eviction with different stream IDs

Test 3: Cache Overflow Test (Synthetic)

• Directly inserts 100 entries into cache
• Verifies LRU eviction at MAX_CACHE_SIZE limit
• Most direct validation of the fix

How to Run Tests

# 1. Build
npm run build

# 2. Serve
npm run dev

# 3. Open test page
http://localhost:3000/samples/cache/initcache-test.html

# 4. Run any of the 3 tests
# 5. Enter branch name and click "Generate Report"
# 6. Run on different branch and click "Compare Reports"

Design Decisions

1. Cache size of 50: A conservative default that should cover most use cases

   • Typical content has multiple representations per stream
   • 50 entries should cover several recent streams
   • Can be made configurable via Settings if needed

2. LRU vs. TTL: LRU chosen because:

   • Init segments don't expire, they're valid for the stream duration
   • LRU naturally evicts least-used entries
   • No timer overhead

3. removeStream() method: Allows explicit cleanup when a stream ends

   • Can be called by StreamProcessor on stream completion
   • Optional optimization, not required for correctness

Expected Impact

Scenario	Before (development)	After (this PR)
Long multi-period playback	Cache grows unbounded	Cache capped at 50 entries
Memory usage	Grows linearly	Bounded (~50-500KB max)
Smart TV stability	Potential OOM	Stable

Testing Checklist

• Existing unit tests pass
• Build succeeds (lint passes)
• Test page included with 3 test modes
• getStats() method for monitoring
• Before/after comparison validated
• Test with real multi-period content (recommended)
• Memory profiling comparison (recommended)

Breaking Changes

None. Cache behavior is transparent to consumers.

🤖 Generated with Claude Code

Fixes #4932