//! Tests for token-aware read_file limiting.
//!
//! These tests verify that read_file properly limits output based on
//! context window state to prevent blowing out the context.

use std::fs;
use std::path::PathBuf;
use tempfile::TempDir;

/// Helper to create a test file with specified size
fn create_test_file(dir: &TempDir, name: &str, size_bytes: usize) -> PathBuf {
    let path = dir.path().join(name);
    let content: String = "x".repeat(size_bytes);
    fs::write(&path, &content).unwrap();
    path
}

/// Test the helper functions directly
mod helper_tests {
    /// Bytes per token heuristic (must match file_ops.rs)
    const BYTES_PER_TOKEN: f32 = 3.5;

    /// Estimate token count from byte size (must match file_ops.rs)
    fn estimate_tokens_from_bytes(bytes: usize) -> u32 {
        ((bytes as f32 / BYTES_PER_TOKEN) * 1.1).ceil() as u32
    }

    /// Calculate the maximum bytes we should read based on context window state.
    fn calculate_read_limit(file_bytes: usize, total_tokens: u32, used_tokens: u32) -> Option<usize> {
        let file_tokens = estimate_tokens_from_bytes(file_bytes);
        let max_tokens_for_file = (total_tokens as f32 * 0.20) as u32; // 20%
        
        // Tier 1: File is small enough (< 20% of context) - no limit
        if file_tokens < max_tokens_for_file {
            return None;
        }
        
        // Calculate available context
        let available_tokens = total_tokens.saturating_sub(used_tokens);
        let half_available = available_tokens / 2;
        
        // Tier 3: If 20% would exceed half of available, cap at half available
        let effective_max_tokens = if max_tokens_for_file > half_available {
            half_available
        } else {
            // Tier 2: Cap at 20% of total context
            max_tokens_for_file
        };
        
        // Convert tokens back to bytes
        let max_bytes = (effective_max_tokens as f32 * BYTES_PER_TOKEN / 1.1) as usize;
        
        Some(max_bytes)
    }

    #[test]
    fn test_estimate_tokens_from_bytes() {
        // 3500 bytes at 3.5 bytes/token = 1000 tokens, +10% = 1100
        let tokens = estimate_tokens_from_bytes(3500);
        assert_eq!(tokens, 1100);
        
        // Small file
        let tokens = estimate_tokens_from_bytes(100);
        assert!(tokens > 0 && tokens < 50);
    }

    #[test]
    fn test_tier1_small_file_no_limit() {
        // 100k token context, file would be ~1000 tokens (well under 20% = 20k)
        let limit = calculate_read_limit(3500, 100_000, 0);
        assert!(limit.is_none(), "Small file should have no limit");
    }

    #[test]
    fn test_tier2_large_file_capped_at_20_percent() {
        // 100k token context, file would be ~100k tokens (way over 20%)
        // Should cap at 20% = 20k tokens worth of bytes
        let limit = calculate_read_limit(350_000, 100_000, 0);
        assert!(limit.is_some(), "Large file should be limited");
        
        let max_bytes = limit.unwrap();
        // 20% of 100k = 20k tokens, at 3.5 bytes/token / 1.1 = ~63k bytes
        assert!(max_bytes > 50_000 && max_bytes < 70_000, 
            "Expected ~63k bytes, got {}", max_bytes);
    }

    #[test]
    fn test_tier3_context_nearly_full() {
        // 100k token context, already at 70% (30k available)
        // 20% of total = 20k tokens, but half of available = 15k tokens
        // Should cap at 15k tokens worth of bytes
        let limit = calculate_read_limit(350_000, 100_000, 70_000);
        assert!(limit.is_some(), "Large file should be limited");
        
        let max_bytes = limit.unwrap();
        // 15k tokens at 3.5 bytes/token / 1.1 = ~47k bytes
        assert!(max_bytes > 40_000 && max_bytes < 55_000,
            "Expected ~47k bytes when context at 70%, got {}", max_bytes);
    }

    #[test]
    fn test_tier3_context_very_full() {
        // 100k token context, already at 90% (10k available)
        // 20% of total = 20k tokens, but half of available = 5k tokens
        // Should cap at 5k tokens worth of bytes
        let limit = calculate_read_limit(350_000, 100_000, 90_000);
        assert!(limit.is_some(), "Large file should be limited");
        
        let max_bytes = limit.unwrap();
        // 5k tokens at 3.5 bytes/token / 1.1 = ~15.9k bytes
        assert!(max_bytes > 10_000 && max_bytes < 20_000,
            "Expected ~16k bytes when context at 90%, got {}", max_bytes);
    }

    #[test]
    fn test_boundary_exactly_20_percent() {
        // File that's exactly at the 20% boundary
        // 100k context, 20% = 20k tokens
        // 20k tokens at 3.5 bytes/token * 1.1 = ~77k bytes would trigger limit
        
        // Just under - should not limit
        let limit = calculate_read_limit(60_000, 100_000, 0);
        assert!(limit.is_none(), "File just under 20% should not be limited");
        
        // Just over - should limit
        let limit = calculate_read_limit(80_000, 100_000, 0);
        assert!(limit.is_some(), "File just over 20% should be limited");
    }
}

/// Integration-style tests that would test the actual tool execution
/// These are commented out as they require more setup (ToolContext, etc.)
/// but document the expected behavior.
#[cfg(test)]
mod integration_notes {
    // To fully test execute_read_file with token limiting:
    // 1. Create a mock ToolContext with specific context_total_tokens and context_used_tokens
    // 2. Create a large test file
    // 3. Call execute_read_file and verify:
    //    - Output contains truncation warning header
    //    - Content is actually truncated to expected size
    //    - Header shows correct character range and context percentage
}
