context_builder/

token_count.rs

use ignore::DirEntry;
use once_cell::sync::Lazy;
use std::collections::BTreeMap;
use std::fs;
use std::path::Path;
/// Token counting utilities for estimating LLM token usage
use tiktoken_rs::{CoreBPE, cl100k_base};

// Initialize the tokenizer once and reuse it
static TOKENIZER: Lazy<CoreBPE> = Lazy::new(|| cl100k_base().unwrap());

/// Estimates the number of tokens in a text string using a real tokenizer
pub fn estimate_tokens(text: &str) -> usize {
    TOKENIZER.encode_with_special_tokens(text).len()
}

/// Counts the tokens that would be generated for a file
pub fn count_file_tokens(base_path: &Path, entry: &DirEntry, line_numbers: bool) -> usize {
    let file_path = entry.path();
    let relative_path = file_path.strip_prefix(base_path).unwrap_or(file_path);

    // Start with tokens for the file header (path, size, modified time)
    let mut token_count = estimate_tokens(&format!(
        "\n### File: `{}`\n\n- Size: {} bytes\n- Modified: {}\n\n",
        relative_path.display(),
        entry.metadata().map(|m| m.len()).unwrap_or(0),
        "Unknown"
    )); // Using "Unknown" as placeholder for modified time in estimation

    // Add tokens for the code fences
    token_count += estimate_tokens("```\n```");

    // Try to read file content
    if let Ok(content) = fs::read_to_string(file_path) {
        if line_numbers {
            // When line numbers are enabled, we add the line number prefix to each line
            let lines_with_numbers: String = content
                .lines()
                .enumerate()
                .map(|(i, line)| format!("{:>4} | {}\n", i + 1, line))
                .collect();
            token_count += estimate_tokens(&lines_with_numbers);
        } else {
            token_count += estimate_tokens(&content);
        }
    }

    token_count
}

/// Counts the tokens that would be generated for the entire file tree section
pub fn count_tree_tokens(tree: &BTreeMap<String, crate::tree::FileNode>, depth: usize) -> usize {
    let mut token_count = 0;

    // Add tokens for indentation
    let indent = "  ".repeat(depth);

    for (name, node) in tree {
        match node {
            crate::tree::FileNode::File => {
                token_count += estimate_tokens(&format!("{}- 📄 {}\n", indent, name));
            }
            crate::tree::FileNode::Directory(children) => {
                token_count += estimate_tokens(&format!("{}- 📁 {}\n", indent, name));
                token_count += count_tree_tokens(children, depth + 1);
            }
        }
    }

    token_count
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::collections::BTreeMap;

    #[test]
    fn test_estimate_tokens() {
        // Test with a simple string
        let text = "Hello, world!";
        let tokens = estimate_tokens(text);
        // "Hello, world!" is 4 tokens with cl100k_base
        assert_eq!(tokens, 4);

        // Test with code-like content
        let code_text = "fn main() {\n    println!(\"Hello, world!\");\n}";
        let tokens = estimate_tokens(code_text);
        // This specific code snippet is 12 tokens with cl100k_base
        assert_eq!(tokens, 12);
    }

    #[test]
    fn test_count_tree_tokens() {
        // Create a simple tree structure
        let mut tree = BTreeMap::new();
        tree.insert("file1.rs".to_string(), crate::tree::FileNode::File);

        let mut subdir = BTreeMap::new();
        subdir.insert("file2.md".to_string(), crate::tree::FileNode::File);
        tree.insert("src".to_string(), crate::tree::FileNode::Directory(subdir));

        let tokens = count_tree_tokens(&tree, 0);
        // "- 📄 file1.rs\n" -> 8 tokens
        // "- 📁 src\n" -> 6 tokens
        // "  - 📄 file2.md\n" -> 9 tokens
        // Total should be 23 tokens
        assert_eq!(tokens, 23);
    }

    #[test]
    fn test_token_estimation_format_consistency() {
        use tempfile::tempdir;

        let dir = tempdir().unwrap();
        let test_file = dir.path().join("test.rs");
        std::fs::write(&test_file, "fn main() {}\n").unwrap();

        let entry = ignore::WalkBuilder::new(&test_file)
            .build()
            .next()
            .unwrap()
            .unwrap();

        // Estimate tokens for the file
        let estimated_tokens = count_file_tokens(dir.path(), &entry, false);

        // Generate actual markdown content
        let mut actual_content = Vec::new();
        crate::markdown::process_file(dir.path(), &test_file, &mut actual_content, false, None)
            .unwrap();
        let actual_content_str = String::from_utf8(actual_content).unwrap();

        // Count actual tokens
        let actual_tokens = estimate_tokens(&actual_content_str);

        // The estimation should be close to actual (within a reasonable margin)
        // Allow for some variance due to timestamp differences and minor formatting
        let difference = actual_tokens.abs_diff(estimated_tokens);

        // Should be within 10% or 20 tokens difference (whichever is larger)
        let max_allowed_difference = std::cmp::max(actual_tokens / 10, 20);

        assert!(
            difference <= max_allowed_difference,
            "Token estimation {} differs too much from actual {} (difference: {})",
            estimated_tokens,
            actual_tokens,
            difference
        );
    }

    #[test]
    fn test_estimate_tokens_empty_string() {
        let tokens = estimate_tokens("");
        assert_eq!(tokens, 0);
    }

    #[test]
    fn test_estimate_tokens_whitespace_only() {
        let tokens = estimate_tokens("   \n\t  ");
        assert!(tokens > 0); // Whitespace still counts as tokens
    }

    #[test]
    fn test_estimate_tokens_unicode() {
        let tokens = estimate_tokens("Hello 世界! 🌍");
        assert!(tokens > 0);
        // Unicode characters may be encoded as multiple tokens
        assert!(tokens >= 4);
    }

    #[test]
    fn test_count_file_tokens_with_line_numbers() {
        use tempfile::tempdir;

        let dir = tempdir().unwrap();
        let test_file = dir.path().join("test.rs");
        std::fs::write(&test_file, "line 1\nline 2\nline 3").unwrap();

        let entry = ignore::WalkBuilder::new(&test_file)
            .build()
            .next()
            .unwrap()
            .unwrap();

        let tokens_without_line_numbers = count_file_tokens(dir.path(), &entry, false);
        let tokens_with_line_numbers = count_file_tokens(dir.path(), &entry, true);

        // With line numbers should have more tokens due to line number prefixes
        assert!(tokens_with_line_numbers > tokens_without_line_numbers);
    }

    #[test]
    fn test_count_file_tokens_unreadable_file() {
        use tempfile::tempdir;

        let dir = tempdir().unwrap();
        let test_file = dir.path().join("nonexistent.txt");

        // Create a mock DirEntry for a file that doesn't exist
        // This simulates what happens when a file is deleted between discovery and processing
        let walker = ignore::WalkBuilder::new(dir.path());
        let mut found_entry = None;

        // Create the file temporarily to get a DirEntry
        std::fs::write(&test_file, "temp").unwrap();
        for entry in walker.build() {
            if let Ok(entry) = entry
                && entry.path() == test_file
            {
                found_entry = Some(entry);
                break;
            }
        }

        // Now delete the file
        std::fs::remove_file(&test_file).unwrap();

        if let Some(entry) = found_entry {
            let tokens = count_file_tokens(dir.path(), &entry, false);
            // Should still return some tokens for the file header even if content can't be read
            assert!(tokens > 0);
        }
    }

    #[test]
    fn test_count_tree_tokens_empty_tree() {
        let tree = BTreeMap::new();
        let tokens = count_tree_tokens(&tree, 0);
        assert_eq!(tokens, 0);
    }

    #[test]
    fn test_count_tree_tokens_nested_directories() {
        let mut tree = BTreeMap::new();

        // Create deeply nested structure
        let mut level3 = BTreeMap::new();
        level3.insert("deep_file.txt".to_string(), crate::tree::FileNode::File);

        let mut level2 = BTreeMap::new();
        level2.insert(
            "level3".to_string(),
            crate::tree::FileNode::Directory(level3),
        );

        let mut level1 = BTreeMap::new();
        level1.insert(
            "level2".to_string(),
            crate::tree::FileNode::Directory(level2),
        );

        tree.insert(
            "level1".to_string(),
            crate::tree::FileNode::Directory(level1),
        );

        let tokens = count_tree_tokens(&tree, 0);
        assert!(tokens > 0);

        // Should account for indentation at different levels
        let tokens_with_depth = count_tree_tokens(&tree, 2);
        assert!(tokens_with_depth > tokens); // More indentation = more tokens
    }

    #[test]
    fn test_count_tree_tokens_mixed_content() {
        let mut tree = BTreeMap::new();

        // Add files with various name lengths and characters
        tree.insert("a.txt".to_string(), crate::tree::FileNode::File);
        tree.insert(
            "very_long_filename_with_underscores.rs".to_string(),
            crate::tree::FileNode::File,
        );
        tree.insert("файл.txt".to_string(), crate::tree::FileNode::File); // Unicode filename

        let mut subdir = BTreeMap::new();
        subdir.insert("nested.md".to_string(), crate::tree::FileNode::File);
        tree.insert(
            "directory".to_string(),
            crate::tree::FileNode::Directory(subdir),
        );

        let tokens = count_tree_tokens(&tree, 0);
        assert!(tokens > 0);

        // Verify it handles unicode filenames without crashing
        assert!(tokens > 20); // Should be substantial given the content
    }
}