fix: improve IPTV playlist concurrency safety and XMLTV parsing relia…

[saidai-bhuvanesh]

Overview

This Pull Request introduces critical performance and reliability improvements to the IPTV playlist loading and EPG XMLTV parsing engine in ARVIO. The changes address a silent crash condition during concurrent playlist loads and a complete bypass of backslash escape sanitization during EPG parsing.

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Key Improvements

1. Concurrency Fix for Playlist Loading

• Issue: When multiple playlists are configured, they are fetched concurrently using Kotlin coroutines. The results are aggregated into a Collections.synchronizedList. As each playlist finished, runCatching { onChannelsReady(aggregatedChannels.toList()) } copied the list. However, iterating on a synchronized list is not thread-safe and threw a ConcurrentModificationException when another thread added channels concurrently. This silenced the callback and prevented the UI from receiving channel updates.
• Fix: Wrapped the .toList() copy operation in an explicit synchronized(aggregatedChannels) block in IptvRepository.kt.

2. Optimized Bulk Sanitization for EPG XMLTV Files

• Issue: BackslashEscapeSanitizingInputStream (designed to filter JSON-style backslashes to prevent XML parser crashes) only overrode the single-byte read(). Because XML Pull/SAX parsers read in blocks, this filter was completely bypassed, causing crashes on malformed feeds.
• Fix: Fully implemented read(b: ByteArray, off: Int, len: Int) to perform in-place sanitization directly on the byte buffer in a single pass. A lookahead mechanism handles split backslash boundaries cleanly.

3. Unit Test Verification

• Created a comprehensive test suite in IptvRepositoryOptimizationTest.kt verifying:
  • Bulk block-read sanitization.
  • Byte-by-byte sanitization.
  • Escape sequences split across chunk boundaries.
  • Trailing backslashes at end-of-stream.
  • Stress testing concurrent additions and list copying to guarantee thread safety.

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Verification & Test Results

Both main build variants compile successfully, and the entire test suite passes without regressions:

• PlayDebug compile: BUILD SUCCESSFUL (42 tasks executed/up-to-date)
• SideloadDebug compile: BUILD SUCCESSFUL (42 tasks executed/up-to-date)
• PlayDebug unit tests: BUILD SUCCESSFUL (all tests passed, including the new optimization test suite)