feat: implement full-text search with q parameter

[GautamGunecha]

Feat: Implement Full-Text Search with q Parameter

Problem

The q parameter for full-text search was documented and expected by users but was not actually implemented in the codebase. When users tried to search with queries like GET /posts?q=title, they received empty results instead of filtered data.

Root Cause

The current filtering logic in src/service.ts only handled:

• Exact matches (item=value)
• Comparison operators (item_gt, item_lt, etc.)
• Special parameters (_embed, _sort, etc.)

The q parameter was treated as a regular field name, which didn't exist in the data, resulting in no matches.

Solution

Implemented comprehensive full-text search functionality:

Features Added

• Case-insensitive search: q=sushi and q=Sushi both work
• Substring matching: q=aliment finds "Alimentação"
• Multi-field search: Searches across all string properties
• Nested object support: Searches within nested objects and arrays
• Backward compatible: Doesn't break existing functionality

Technical Implementation

• Added special handling for q parameter in Service.find() method
• Implemented #searchInItem() and #searchInObject() methods for recursive search
• Search runs before other filters and is excluded from regular query processing
• Added comprehensive test coverage (7 new test cases)

Code Changes

• Modified: src/service.ts - Added search functionality
• Modified: src/service.test.ts - Added test coverage
• Lines changed: +85 insertions, 0 deletions

Testing

• All existing tests pass (87/87)
• Added 7 new test cases for search functionality
• Verified with real-world data:

  # Before fix
  GET /transactions?q=Sushi → []
  
  # After fix  
  GET /transactions?q=Sushi → [{"id": 2, "description": "Sushi", ...}]

Usage Examples

# Search across all string fields
GET /posts?q=title
GET /users?q=john

# Case-insensitive and substring matching
GET /posts?q=json     # finds "JSON Server"
GET /posts?q=server  # finds "JSON Server"

🔗 Related Issues

This fixes the commonly reported issue where users expected the q parameter to work for full-text search but it returned empty results.

Checklist

• Code follows existing style guidelines
• Self-review completed
• Tests added/updated and passing
• Documentation updated (if applicable)
• No breaking changes
• Backward compatible

Impact

• User Experience: Users can now search their data as expected
• Performance: Minimal overhead, search runs before other filters
• Compatibility: No breaking changes to existing functionality
• Testing: Comprehensive test coverage ensures reliability