refactor: Extract IndexApiHandler from http_server.cpp

[Copilot]

Description

Extracts 9 index management endpoints (~476 lines) from monolithic http_server.cpp into dedicated IndexApiHandler class, following the established handler pattern.

Type of Change

• 🐛 Bug fix (non-breaking change which fixes an issue)
• ✨ New feature (non-breaking change which adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to not work as expected)
• 📝 Documentation update
• ♻️ Code refactoring (no functional changes)
• ⚡ Performance improvement
• ✅ Test addition or update
• 🔧 Configuration change
• 🎨 UI/UX change

Related Issues

Implements the IndexApiHandler extraction task.

Changes Made

Implementation (src/server/index_api_handler.cpp - 530 lines)

• Secondary index operations: handleCreate(), handleDrop(), handleStats(), handleRebuild(), handleReindex()
  • Supports regular, range, fulltext, and composite indexes
  • Query string and JSON body parameter parsing
• Adaptive indexing: handleSuggestions(), handlePatterns(), handleRecordPattern(), handleClearPatterns()
  • Pattern tracking and suggestion generation
  • OpenTelemetry tracing integration
• Helpers: makeResponse(), makeErrorResponse() matching http_server.cpp patterns

Integration

• CMakeLists.txt: Added index_api_handler.cpp to build
• http_server.h: Added std::unique_ptr<IndexApiHandler> index_api_ member
• http_server.cpp:
  • Handler initialization with storage_, secondary_index_, adaptive_index_, auth_ dependencies
  • Route delegation for 9 index endpoints

Example Usage

// Before: Direct method call in http_server.cpp
case Route::IndexCreatePost:
    response = handleCreateIndex(req);  // ~107 lines inline

// After: Delegated to handler
case Route::IndexCreatePost:
    response = index_api_->handleCreate(req);  // Extracted to dedicated class

Testing

Test Environment

• OS: CI environments (Ubuntu, Windows, macOS)
• Compiler: GCC 13, Clang, MSVC
• Build Type: Release, Debug

Test Results

• All existing tests pass
• New tests added for changes
• Manual testing performed

Test Commands

# Existing test suite validates functionality
ctest -R test_http_index_endpoints

Checklist

• My code follows the coding standards
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have updated the documentation accordingly
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published

Code Quality

• Code builds without errors
• Code builds without warnings
• Static analysis (cppcheck) passes
• No memory leaks detected
• Code follows C++17 standards

Documentation

• README.md updated (if applicable)
• CHANGELOG.md updated
• API documentation updated (if applicable)
• Code comments added/updated

Branch Strategy Compliance

• PR targets the correct branch (develop for features, main for releases/hotfixes)
• Branch naming follows convention (e.g., feature/, bugfix/, hotfix/, release/)
• No direct commits to main or develop

Performance Impact

• No significant performance impact
• Performance improvement (describe below)
• Performance regression (justify below)

Performance Notes:
Zero-overhead refactoring - direct delegation to handler methods, no additional abstraction layers.

Breaking Changes

None. Maintains identical endpoint behavior and response formats.

Breaking Change Details:
N/A

Security Considerations

• No security implications
• Security review required
• Dependencies updated to secure versions

Additional Notes

• Preserves original query parsing, error handling, and response formatting
• Code review identified pre-existing issues (URL decoding, exception handling) - intentionally not addressed to maintain minimal scope
• Handler pattern enables future improvements: URL decoding, shared query parser, enhanced validation

Screenshots/Logs

N/A

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For Maintainers:

Review Checklist

• Code quality acceptable
• Tests adequate
• Documentation complete
• No security concerns
• Ready to merge

Merge Strategy

• Squash and merge (✅ Recommended for feature/bugfix PRs - cleaner history)
• Merge commit (Only for release/hotfix branches)
• Rebase and merge

Original prompt

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This section details on the original issue you should resolve

<issue_title>REFACTOR] Implement IndexApiHandler - Extract Index Operations from http_server.cpp</issue_title>
<issue_description># Refactoring Task: IndexApiHandler Implementation

Overview

Extract and implement index management operations from http_server.cpp into the IndexApiHandler class.

Handler Details

Class: IndexApiHandler
Files: include/server/index_api_handler.h, src/server/index_api_handler.cpp
Lines to Extract: ~400 lines
Complexity: Medium

Endpoints to Implement

1. POST /indexes/create - handleCreate()
2. POST /indexes/drop - handleDrop()
3. POST /indexes/rebuild - handleRebuild()
4. GET /indexes/stats - handleStats()
5. POST /indexes/suggestions - handleSuggestions()
6. GET /indexes/patterns - handlePatterns()

Key Dependencies

• std::shared_ptr<RocksDBWrapper> storage_
• std::shared_ptr<SecondaryIndex> secondary_index_
• std::shared_ptr<AdaptiveIndex> adaptive_index_
• std::shared_ptr<AuthMiddleware> auth_

Features

• Secondary index management
• Adaptive indexing
• Index statistics
• Query pattern analysis
• Index suggestions

Documentation

• See docs/HANDLER_IMPLEMENTATION_GUIDE.md
• See docs/INTEGRATION_GUIDE.md
• Reference: src/server/admin_api_handler.cpp

Acceptance Criteria

• All 6 handler methods implemented
• Secondary index operations working
• Adaptive indexing working
• Tests pass
• Integrated into HttpServer

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Effort: Medium | Priority: P2 | Complexity: Medium</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes REFACTOR] Implement IndexApiHandler - Extract Index Operations from http_server.cpp #432

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