robit_agent/

context.rs

//! Context management — output truncation and history window management.

use async_openai::types::chat::ChatCompletionRequestMessage;
use robit_ai::config::ContextConfig;

// ============================================================================
// Truncation result
// ============================================================================

/// Result of context truncation, used for async compression.
#[derive(Debug)]
pub struct TruncationResult {
    /// Number of conversation rounds removed.
    pub rounds_removed: usize,
    /// Number of individual messages removed.
    pub messages_removed: usize,
    /// The removed messages (for generating summary).
    pub removed_messages: Vec<ChatCompletionRequestMessage>,
    /// Position where summary should be inserted.
    pub insert_position: usize,
    /// Whether compression is needed (token count exceeds threshold).
    pub needs_compression: bool,
}

// ============================================================================
// Tool output truncation (Layer 1)
// ============================================================================

/// Truncate tool output based on line count and byte limits.
pub fn truncate_output(content: &str, max_lines: usize, max_bytes: usize) -> String {
    let lines: Vec<&str> = content.lines().collect();
    let total_lines = lines.len();
    let total_bytes = content.len();

    // Check if truncation is needed
    let line_truncated = total_lines > max_lines;
    let byte_truncated = total_bytes > max_bytes;

    if !line_truncated && !byte_truncated {
        return content.to_string();
    }

    let mut output = String::new();
    let mut byte_count = 0;
    let mut displayed_lines = 0;

    for (i, line) in lines.iter().enumerate() {
        if i >= max_lines {
            break;
        }
        let line_with_newline = if i < total_lines - 1 {
            format!("{}\n", line)
        } else {
            line.to_string()
        };

        if byte_count + line_with_newline.len() > max_bytes {
            break;
        }

        output.push_str(&line_with_newline);
        byte_count += line_with_newline.len();
        displayed_lines += 1;
    }

    if line_truncated {
        output.push_str(&format!(
            "\n... (Output truncated, {} lines total, showing first {}. Use offset/limit to read more)",
            total_lines, displayed_lines
        ));
    } else if byte_truncated {
        output.push_str(&format!(
            "\n... (Output truncated, {} bytes total, showing first {} bytes)",
            total_bytes, byte_count
        ));
    }

    output
}

// ============================================================================
// Token estimation
// ============================================================================

/// Estimate token count for a string.
///
/// Uses a more nuanced heuristic based on character type:
/// - ASCII letters/digits: ~3.5 chars/token (BPE tokenizer average)
/// - CJK characters: ~1.5 chars/token (most CJK chars are 1-2 tokens each)
/// - Whitespace: minimal token cost (usually merged with adjacent tokens)
/// - Punctuation/symbols: ~1 token per char (often individual tokens)
/// - Code (braces, operators): ~1 token per char
///
/// This is still an estimate; apply `token_safety_margin` at the message level.
pub fn estimate_tokens(text: &str) -> usize {
    if text.is_empty() {
        return 0;
    }

    let mut ascii_alnum = 0usize;
    let mut cjk = 0usize;
    let mut whitespace = 0usize;
    let mut other = 0usize; // punctuation, symbols, code characters

    for ch in text.chars() {
        if ch.is_whitespace() {
            whitespace += 1;
        } else if ch.is_ascii_alphanumeric() {
            ascii_alnum += 1;
        } else {
            let cp = ch as u32;
            // CJK Unified Ideographs + extensions + fullwidth forms
            // + Hiragana, Katakana, Hangul, CJK punctuation
            if (0x4E00..=0x9FFF).contains(&cp)
                || (0x3400..=0x4DBF).contains(&cp)
                || (0xF900..=0xFAFF).contains(&cp)
                || (0xFF00..=0xFFEF).contains(&cp)
                || (0x3000..=0x303F).contains(&cp)
                || (0x3040..=0x309F).contains(&cp)
                || (0x30A0..=0x30FF).contains(&cp)
                || (0xAC00..=0xD7AF).contains(&cp)
            {
                cjk += 1;
            } else {
                other += 1;
            }
        }
    }

    // BPE tokenizer averages:
    // - ASCII alphanumeric: ~3.5 chars per token
    // - CJK: ~1.5 chars per token (most are 1 token each, some pairs)
    // - Whitespace: negligible (merged with adjacent tokens)
    // - Other (punctuation/code): ~1 char per token
    let ascii_tokens = (ascii_alnum as f64 / 3.5).ceil() as usize;
    let cjk_tokens = (cjk as f64 / 1.5).ceil() as usize;
    let whitespace_tokens = (whitespace as f64 / 10.0).ceil() as usize;
    let other_tokens = other; // ~1:1

    ascii_tokens + cjk_tokens + whitespace_tokens + other_tokens
}

/// Estimate tokens for a list of messages.
pub fn estimate_messages_tokens(messages: &[ChatCompletionRequestMessage]) -> usize {
    let mut total = 0;
    for msg in messages {
        // Each message has ~4 tokens of overhead (role, delimiters)
        total += 4;
        total += estimate_message_content_tokens(msg);
    }
    total
}

/// Estimate tokens for messages, applying the configured safety margin.
pub fn estimate_messages_tokens_with_margin(
    messages: &[ChatCompletionRequestMessage],
    safety_margin: f32,
) -> usize {
    let raw = estimate_messages_tokens(messages);
    (raw as f32 * safety_margin).ceil() as usize
}

/// Estimate tokens for a single message's content.
fn estimate_message_content_tokens(msg: &ChatCompletionRequestMessage) -> usize {
    match serde_json::to_string(msg) {
        Ok(json) => estimate_tokens(&json),
        Err(_) => 0,
    }
}

// ============================================================================
// Context manager (Layer 2: history truncation)
// ============================================================================

/// Manages the context window, truncating history when approaching token limits.
pub struct ContextManager {
    /// Model's context window size in tokens.
    pub max_tokens: usize,
    /// Ratio of context window to reserve for LLM response (default 0.2 = 20%).
    pub reserve_ratio: f32,
    /// Fraction of max_tokens at which truncation triggers (default 0.7).
    pub truncation_ratio: f32,
    /// Minimum conversation rounds to keep after truncation (default 3).
    pub min_keep_rounds: usize,
    /// Safety multiplier for token estimates (default 1.3).
    pub token_safety_margin: f32,
    /// Max output lines for tool results.
    pub max_output_lines: usize,
    /// Max output bytes for tool results.
    pub max_output_bytes: usize,
    /// Token threshold for triggering compression.
    pub compression_token_threshold: usize,
    /// Whether compression is enabled.
    pub compression_enabled: bool,
    /// Maximum tool calls per turn (default 30).
    pub max_tool_calls_per_turn: usize,
}

impl ContextManager {
    pub fn new(context_window: Option<u64>, config: Option<&ContextConfig>) -> Self {
        let max_tokens = context_window.unwrap_or(65536) as usize;

        let (
            max_output_lines,
            max_output_bytes,
            reserve_ratio,
            truncation_ratio,
            min_keep_rounds,
            token_safety_margin,
            compression_token_threshold,
            compression_enabled,
            max_tool_calls_per_turn,
        ) = match config {
            Some(c) => (
                c.max_output_lines.unwrap_or(500),
                c.max_output_bytes.unwrap_or(51200),
                c.reserve_ratio.unwrap_or(0.2),
                c.truncation_ratio.unwrap_or(0.7),
                c.min_keep_rounds.unwrap_or(3),
                c.token_safety_margin.unwrap_or(1.3),
                c.compression_token_threshold.unwrap_or(5000),
                c.compression_enabled.unwrap_or(true),
                c.max_tool_calls_per_turn.unwrap_or(30),
            ),
            None => (500, 51200, 0.2, 0.7, 3, 1.3, 5000, true, 30),
        };

        Self {
            max_tokens,
            reserve_ratio,
            truncation_ratio,
            min_keep_rounds,
            token_safety_margin,
            max_output_lines,
            max_output_bytes,
            compression_token_threshold,
            compression_enabled,
            max_tool_calls_per_turn,
        }
    }

    /// Maximum tokens at which truncation is triggered.
    /// Uses `truncation_ratio` (default 0.7) to trigger earlier than the
    /// absolute limit, leaving headroom for estimation errors and LLM response.
    pub fn truncation_threshold(&self) -> usize {
        (self.max_tokens as f32 * self.truncation_ratio) as usize
    }

    /// Maximum tokens available for input (total - reserved for response).
    /// Note: this is the absolute upper bound; truncation actually triggers
    /// earlier via `truncation_threshold()`.
    pub fn available_tokens(&self) -> usize {
        (self.max_tokens as f32 * (1.0 - self.reserve_ratio)) as usize
    }

    /// Truncate tool output using the configured limits.
    pub fn truncate_tool_output(&self, content: &str) -> String {
        truncate_output(content, self.max_output_lines, self.max_output_bytes)
    }

    /// Check if history needs truncation and perform it if necessary.
    /// Returns `TruncationResult` with removed messages for async compression.
    ///
    /// Strategy:
    /// 1. Uses `truncation_threshold()` (default 70% of max_tokens) as trigger point
    /// 2. Removes oldest non-system rounds first
    /// 3. Always keeps at least `min_keep_rounds` recent rounds
    /// 4. Applies `token_safety_margin` to estimates to avoid underestimation
    pub fn maybe_truncate(
        &self,
        messages: &mut Vec<ChatCompletionRequestMessage>,
    ) -> TruncationResult {
        let estimated = estimate_messages_tokens_with_margin(messages, self.token_safety_margin);
        let threshold = self.truncation_threshold();

        if estimated <= threshold {
            return TruncationResult {
                rounds_removed: 0,
                messages_removed: 0,
                removed_messages: Vec::new(),
                insert_position: 0,
                needs_compression: false,
            };
        }

        tracing::info!(
            "Context truncation needed: estimated {} tokens (with {:.1}x margin), threshold {} tokens, max {} tokens",
            estimated,
            self.token_safety_margin,
            threshold,
            self.max_tokens
        );

        // Find round boundaries: a round starts with a User message
        let mut round_starts: Vec<usize> = Vec::new();
        for (i, msg) in messages.iter().enumerate() {
            if is_user_message(msg) {
                round_starts.push(i);
            }
        }

        if round_starts.is_empty() {
            return TruncationResult {
                rounds_removed: 0,
                messages_removed: 0,
                removed_messages: Vec::new(),
                insert_position: 0,
                needs_compression: false,
            };
        }

        // Count how many rounds we must keep
        let total_rounds = round_starts.len();
        let must_keep = self.min_keep_rounds.min(total_rounds);

        let mut removed_messages: Vec<ChatCompletionRequestMessage> = Vec::new();
        let mut rounds_removed = 0;
        let mut messages_removed = 0;

        // Remove oldest rounds while:
        // - estimated tokens still exceed threshold
        // - we still have more rounds than must_keep
        while round_starts.len() > must_keep
            && estimate_messages_tokens_with_margin(messages, self.token_safety_margin) > threshold
        {
            let start_idx = round_starts[0];
            let end_idx = if round_starts.len() > 1 {
                round_starts[1]
            } else {
                messages.len()
            };

            // Collect removed messages for potential compression
            if self.compression_enabled {
                removed_messages.extend(messages[start_idx..end_idx].to_vec());
            }

            let count = end_idx - start_idx;
            messages.drain(start_idx..end_idx);

            // Update round_starts indices
            round_starts.remove(0);
            for idx in round_starts.iter_mut() {
                *idx = idx.saturating_sub(count);
            }

            rounds_removed += 1;
            messages_removed += count;
        }

        if rounds_removed == 0 {
            return TruncationResult {
                rounds_removed: 0,
                messages_removed: 0,
                removed_messages: Vec::new(),
                insert_position: 0,
                needs_compression: false,
            };
        }

        // Calculate removed tokens for threshold check
        let removed_tokens = estimate_messages_tokens(&removed_messages);
        let needs_compression =
            self.compression_enabled && removed_tokens >= self.compression_token_threshold;

        // Insert informative notice after system messages
        let system_msg_count = messages
            .iter()
            .take_while(|m| is_system_message(m))
            .count();

        let notice = if needs_compression {
            format!(
                "[Context compressed: {} earlier rounds ({} messages, ~{} tokens) have been summarized. {} most recent rounds preserved.]",
                rounds_removed,
                messages_removed,
                removed_tokens,
                round_starts.len()
            )
        } else {
            format!(
                "[Context truncated: {} earlier rounds ({} messages) removed to stay within token limit. {} most recent rounds preserved.]",
                rounds_removed,
                messages_removed,
                round_starts.len()
            )
        };

        let notice_msg = ChatCompletionRequestMessage::User(
            async_openai::types::chat::ChatCompletionRequestUserMessage {
                content: notice.into(),
                name: Some("system_notice".to_string()),
            }
            .into(),
        );

        messages.insert(system_msg_count, notice_msg);

        tracing::info!(
            "Context truncation: removed {} rounds ({} messages, ~{} tokens), kept {} rounds, needs_compression={}",
            rounds_removed,
            messages_removed,
            removed_tokens,
            round_starts.len(),
            needs_compression
        );

        TruncationResult {
            rounds_removed,
            messages_removed,
            removed_messages,
            insert_position: system_msg_count,
            needs_compression,
        }
    }
}

fn is_user_message(msg: &ChatCompletionRequestMessage) -> bool {
    matches!(msg, ChatCompletionRequestMessage::User(_))
}

fn is_system_message(msg: &ChatCompletionRequestMessage) -> bool {
    matches!(msg, ChatCompletionRequestMessage::System(_))
}

// ============================================================================
// Transcript formatting for summary compression
// ============================================================================

/// Format removed messages into a compact transcript for summary generation.
/// Extracts user messages, assistant text, and tool call names only.
/// Truncates each message to keep the transcript concise.
pub fn format_removed_messages_as_transcript(
    messages: &[ChatCompletionRequestMessage],
) -> String {
    let mut transcript = String::new();

    for msg in messages {
        match msg {
            ChatCompletionRequestMessage::User(user_msg) => {
                let text = match &user_msg.content {
                    async_openai::types::chat::ChatCompletionRequestUserMessageContent::Text(t) => {
                        t.clone()
                    }
                    async_openai::types::chat::ChatCompletionRequestUserMessageContent::Array(parts) => {
                        parts.iter()
                            .filter_map(|p| match p {
                                async_openai::types::chat::ChatCompletionRequestUserMessageContentPart::Text(t) => Some(t.text.as_str()),
                                _ => None,
                            })
                            .collect::<Vec<_>>()
                            .join(" ")
                    }
                };
                let truncated = truncate_str(&text, 200);
                transcript.push_str(&format!("User: {}\n", truncated));
            }
            ChatCompletionRequestMessage::Assistant(assistant_msg) => {
                let content_str = assistant_msg.content.as_ref().map(|c| {
                    match serde_json::to_string(c) {
                        Ok(json) => json.trim_matches('"').to_string(),
                        Err(_) => format!("{:?}", c),
                    }
                }).unwrap_or_default();
                let truncated = truncate_str(&content_str, 300);
                transcript.push_str(&format!("Assistant: {}\n", truncated));
                if let Some(tool_calls) = &assistant_msg.tool_calls {
                    for tc in tool_calls {
                        if let async_openai::types::chat::ChatCompletionMessageToolCalls::Function(f) = tc {
                            transcript.push_str(&format!(
                                "  [Tool: {}({})]\n",
                                f.function.name,
                                truncate_str(&f.function.arguments, 100)
                            ));
                        }
                    }
                }
            }
            ChatCompletionRequestMessage::Tool(tool_msg) => {
                let content_str = match serde_json::to_string(&tool_msg.content) {
                    Ok(json) => json.trim_matches('"').to_string(),
                    Err(_) => format!("{:?}", tool_msg.content),
                };
                let truncated = truncate_str(&content_str, 150);
                transcript.push_str(&format!("  [Result: {}]\n", truncated));
            }
            _ => {}
        }
    }

    if transcript.is_empty() {
        transcript.push_str("(no conversation content)");
    }

    transcript
}

/// Truncate a string to at most `max_chars` characters, adding "..." if truncated.
/// Respects UTF-8 character boundaries.
fn truncate_str(s: &str, max_chars: usize) -> String {
    if s.len() <= max_chars {
        s.to_string()
    } else {
        let mut end = max_chars;
        while end > 0 && !s.is_char_boundary(end) {
            end -= 1;
        }
        format!("{}...", &s[..end])
    }
}

// ============================================================================
// Tests
// ============================================================================

#[cfg(test)]
mod tests {
    use super::*;
    use async_openai::types::chat::ChatCompletionRequestUserMessage;

    fn make_user_message(content: &str) -> ChatCompletionRequestMessage {
        ChatCompletionRequestMessage::User(
            ChatCompletionRequestUserMessage {
                content: content.into(),
                name: None,
            }
            .into(),
        )
    }

    fn make_system_message(content: &str) -> ChatCompletionRequestMessage {
        ChatCompletionRequestMessage::System(
            async_openai::types::chat::ChatCompletionRequestSystemMessage {
                content: content.into(),
                name: None,
            }
            .into(),
        )
    }

    fn make_test_config() -> ContextConfig {
        ContextConfig {
            max_output_lines: Some(500),
            max_output_bytes: Some(51200),
            reserve_ratio: Some(0.2),
            truncation_ratio: Some(0.7),
            min_keep_rounds: Some(3),
            token_safety_margin: Some(1.3),
            compression_token_threshold: Some(5000),
            compression_enabled: Some(true),
            max_tool_calls_per_turn: Some(30),
        }
    }

    // ==========================================================================
    // estimate_tokens tests
    // ==========================================================================

    #[test]
    fn test_estimate_tokens_english() {
        let text = "Hello world, this is a test of the token estimation system.";
        let tokens = estimate_tokens(text);
        assert!(tokens >= 10, "Expected at least 10 tokens, got {}", tokens);
        assert!(tokens <= 30, "Expected at most 30 tokens, got {}", tokens);
    }

    #[test]
    fn test_estimate_tokens_chinese() {
        let chinese = "你好世界，这是一个测试。";
        let tokens = estimate_tokens(chinese);
        assert!(tokens >= 5, "Expected at least 5 tokens, got {}", tokens);
        assert!(tokens <= 15, "Expected at most 15 tokens, got {}", tokens);
    }

    #[test]
    fn test_estimate_tokens_code() {
        let code = "fn main() {\n    println!(\"Hello\");\n}";
        let tokens = estimate_tokens(code);
        assert!(tokens >= 10, "Expected at least 10 tokens, got {}", tokens);
        assert!(tokens <= 40, "Expected at most 40 tokens, got {}", tokens);
    }

    #[test]
    fn test_estimate_tokens_empty() {
        assert_eq!(estimate_tokens(""), 0);
    }

    #[test]
    fn test_estimate_tokens_mixed() {
        let mixed = "Hello 你好 world 世界！fn test() {}";
        let tokens = estimate_tokens(mixed);
        assert!(tokens > 0);
        assert!(tokens <= 40, "Expected at most 40 tokens, got {}", tokens);
    }

    #[test]
    fn test_estimate_messages_tokens_with_margin() {
        let messages = vec![
            make_system_message("You are a helpful assistant"),
            make_user_message("Hello world"),
        ];
        let raw = estimate_messages_tokens(&messages);
        let with_margin = estimate_messages_tokens_with_margin(&messages, 1.3);
        assert!(with_margin > raw);
        // 1.3x margin should be ~30% higher
        let expected = (raw as f32 * 1.3).ceil() as usize;
        assert_eq!(with_margin, expected);
    }

    // ==========================================================================
    // ContextManager tests
    // ==========================================================================

    #[test]
    fn test_truncation_threshold() {
        let config = make_test_config();
        let manager = ContextManager::new(Some(65536), Some(&config));
        // 65536 * 0.7 = 45875
        assert_eq!(manager.truncation_threshold(), 45875);
    }

    #[test]
    fn test_truncation_result_no_truncation() {
        let mut messages = vec![
            make_system_message("You are a helpful assistant"),
            make_user_message("Hello"),
        ];

        let config = make_test_config();
        let manager = ContextManager::new(Some(65536), Some(&config));
        let result = manager.maybe_truncate(&mut messages);

        assert_eq!(result.rounds_removed, 0);
        assert!(!result.needs_compression);
    }

    #[test]
    fn test_truncation_respects_min_keep_rounds() {
        let mut messages = vec![
            make_system_message("You are a helpful assistant"),
        ];

        // Add 10 rounds of large messages
        for i in 0..10 {
            let content = format!("User message {}: {}", i, "x".repeat(2000));
            messages.push(make_user_message(&content));
        }

        let mut config = make_test_config();
        config.min_keep_rounds = Some(3); // Must keep at least 3 rounds

        // Use small context window to force aggressive truncation
        let manager = ContextManager::new(Some(5000), Some(&config));
        let result = manager.maybe_truncate(&mut messages);

        // Should have removed some rounds...
        assert!(
            result.rounds_removed > 0,
            "Should have removed some rounds"
        );
        // ...but should still have at least 3 user rounds + notice
        let user_count = messages
            .iter()
            .filter(|m| matches!(m, ChatCompletionRequestMessage::User(_)))
            .count();
        assert!(
            user_count >= 4,
            "Should have at least 3 user rounds + notice, got {}",
            user_count
        );
    }

    #[test]
    fn test_truncation_early_trigger() {
        let mut messages = vec![
            make_system_message("You are a helpful assistant"),
        ];

        // Add 8 rounds of messages, each ~2000 chars
        for i in 0..8 {
            let content = format!("User message {}: {}", i, "x".repeat(2000));
            messages.push(make_user_message(&content));
        }

        let mut config = make_test_config();
        config.truncation_ratio = Some(0.7);
        config.min_keep_rounds = Some(2);
        config.token_safety_margin = Some(1.3);

        // With 65536 context, truncation threshold = 45875
        // 8 rounds * ~2000 chars each ≈ much less than 45875, so no truncation
        let manager = ContextManager::new(Some(65536), Some(&config));
        let result = manager.maybe_truncate(&mut messages);
        assert_eq!(
            result.rounds_removed, 0,
            "Should not truncate small messages in large window"
        );

        // With 8000 context, truncation threshold = 5600
        let manager2 = ContextManager::new(Some(8000), Some(&config));
        let mut messages2 = messages.clone();
        let result2 = manager2.maybe_truncate(&mut messages2);
        assert!(
            result2.rounds_removed > 0,
            "Should truncate when exceeding small window"
        );
    }

    #[test]
    fn test_token_safety_margin_effect() {
        let mut messages = vec![
            make_system_message("You are a helpful assistant"),
        ];

        for i in 0..10 {
            let content = format!("User message {}: {}", i, "x".repeat(500));
            messages.push(make_user_message(&content));
        }

        // With margin 1.0 (no safety), truncation may not trigger
        let mut config_low = make_test_config();
        config_low.token_safety_margin = Some(1.0);
        config_low.truncation_ratio = Some(0.7);
        config_low.min_keep_rounds = Some(1);

        let mut msgs_low = messages.clone();
        let manager_low = ContextManager::new(Some(8000), Some(&config_low));
        let result_low = manager_low.maybe_truncate(&mut msgs_low);

        // With margin 2.0 (very conservative), truncation more likely triggers
        let mut config_high = make_test_config();
        config_high.token_safety_margin = Some(2.0);
        config_high.truncation_ratio = Some(0.7);
        config_high.min_keep_rounds = Some(1);

        let mut msgs_high = messages.clone();
        let manager_high = ContextManager::new(Some(8000), Some(&config_high));
        let result_high = manager_high.maybe_truncate(&mut msgs_high);

        // Higher margin should result in >= rounds removed
        assert!(
            result_high.rounds_removed >= result_low.rounds_removed,
            "Higher safety margin should trigger at least as much truncation: high={}, low={}",
            result_high.rounds_removed,
            result_low.rounds_removed
        );
    }

    #[test]
    fn test_compression_flag_in_old_tests() {
        let mut messages = vec![
            make_system_message("You are a helpful assistant"),
        ];

        // Add 20 rounds of large messages
        for i in 0..20 {
            let content = format!("User message {}: {}", i, "x".repeat(2000));
            messages.push(make_user_message(&content));
        }

        let mut config = make_test_config();
        config.compression_enabled = Some(false);
        config.compression_token_threshold = Some(1000);
        config.min_keep_rounds = Some(1);

        let manager = ContextManager::new(Some(5000), Some(&config));
        let result = manager.maybe_truncate(&mut messages);

        assert!(result.rounds_removed > 0);
        assert!(
            !result.needs_compression,
            "Should be false when compression disabled"
        );
    }

    #[test]
    fn test_truncate_output() {
        let content = "line1\nline2\nline3\nline4\nline5";
        let truncated = truncate_output(content, 3, 100);
        assert!(truncated.contains("line1"));
        assert!(truncated.contains("line2"));
        assert!(truncated.contains("line3"));
        assert!(!truncated.contains("line4"));
        assert!(truncated.contains("Output truncated"));
    }

    // ==========================================================================
    // Transcript formatting tests
    // ==========================================================================

    #[test]
    fn test_truncate_str_no_truncation() {
        let result = truncate_str("hello", 10);
        assert_eq!(result, "hello");
    }

    #[test]
    fn test_truncate_str_with_truncation() {
        let result = truncate_str("hello world this is long", 10);
        assert_eq!(result, "hello worl...");
    }

    #[test]
    fn test_format_transcript_user_and_assistant() {
        let messages = vec![
            make_user_message("Fix the bug in auth.rs"),
            make_system_message("System message should be skipped"),
        ];

        let transcript = format_removed_messages_as_transcript(&messages);
        assert!(transcript.contains("User: Fix the bug in auth.rs"));
        assert!(!transcript.contains("System message"), "System messages should be skipped");
    }

    #[test]
    fn test_format_transcript_empty() {
        let messages: Vec<ChatCompletionRequestMessage> = vec![];
        let transcript = format_removed_messages_as_transcript(&messages);
        assert!(transcript.contains("no conversation content"));
    }

    #[test]
    fn test_format_transcript_truncates_long_messages() {
        let long_text = "x".repeat(500);
        let messages = vec![
            make_user_message(&long_text),
        ];

        let transcript = format_removed_messages_as_transcript(&messages);
        assert!(transcript.contains("..."));
        // Should not contain the full 500 chars
        assert!(transcript.len() < long_text.len() + 50);
    }
}