Flat chat messages hierarchy inference

[konard]

Summary

This PR implements a solution for issue #633, providing an algorithm to infer hierarchical chat message structure from a flat list of message IDs.

The implementation demonstrates how to transform a flat sequence like [1, 2, 1, 1] into a hierarchical tree structure where:

• Position 0 (MessageId: 1) → root message
• Position 1 (MessageId: 2) → reply to position 0
• Position 2 (MessageId: 1) → reply to position 1
• Position 3 (MessageId: 1) → reply to position 2

Implementation Details

Core Components

ChatMessageNode Class

• Represents a message node in the hierarchical structure
• Tracks: MessageId, Position (in flat list), Level (depth), Parent, and Children
• Provides PrintHierarchy() method for visualization

Three Algorithm Variants

1. InferHierarchySequential (Recommended - matches issue Flat chat messages hierarchy inference #633 diagram)

   • Each message is a reply to the immediately previous message
   • Creates a linear conversation thread
   • Best matches the expected behavior from the issue diagram

2. InferHierarchy (Alternative approach)

   • Creates siblings when consecutive messages have the same ID
   • Different ID means reply to previous message
   • Useful for certain threading patterns

3. InferHierarchyAlternative (Advanced pattern)

   • Messages reply to the most recent message with a different ID
   • Handles complex back-reference scenarios

Files Modified/Added

• ✅ Platform/Platform.Sandbox/ChatMessageHierarchyInference.cs - Main implementation with all three algorithms
• ✅ Platform/Platform.Sandbox/Program.cs - Added experiment runner to demonstrate functionality
• ✅ experiments/ChatHierarchyTest.cs - Standalone test that validates the implementation

Testing

Automated Testing

• ✅ All CI checks passing
• ✅ Unit test validates the exact structure from issue Flat chat messages hierarchy inference #633 diagram
• ✅ Tested with multiple patterns: sequential chains, same-ID sequences, complex threading

Test Results

Test: [1, 2, 1, 1] (from issue #633 diagram)
=== Hierarchical Structure ===
[0] MessageId: 1 (Level: 0)
  [1] MessageId: 2 (Level: 1)
    [2] MessageId: 1 (Level: 2)
      [3] MessageId: 1 (Level: 3)

✓ Test PASSED: Structure matches expected hierarchy from issue #633

Usage Example

// Create a flat list of message IDs
var flatMessages = new int[] { 1, 2, 1, 1 };

// Infer the hierarchical structure
var hierarchy = ChatMessageHierarchyInference.InferHierarchySequential(flatMessages);

// Print the hierarchy
ChatMessageHierarchyInference.PrintHierarchy(hierarchy);

Additional Examples Tested

The implementation includes comprehensive testing with various patterns:

• Empty arrays
• Single messages
• Consecutive same IDs: [1, 1, 1]
• Complex patterns: [1, 2, 3, 2, 1]
• Advanced threading: [1, 2, 1, 3, 1]

Notes

• The implementation is located in Platform.Sandbox following the repository's pattern for experimental code
• All three algorithms are provided to support different use cases and interpretations of message threading
• The code includes comprehensive XML documentation for all public methods and classes
• Ready for review and feedback

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Fixes #633

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[konard]

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