opencrabs 0.3.13

//! Agent Context Management
//!
//! Manages conversation context including messages, system brain,
//! and token tracking.

use crate::brain::provider::{ContentBlock, Message, Role};
use crate::brain::tokenizer;
use crate::db::models::Message as DbMessage;
use std::path::PathBuf;
use uuid::Uuid;

/// Agent context for a conversation
#[derive(Debug, Clone)]
pub struct AgentContext {
    /// Session ID
    pub session_id: Uuid,

    /// System brain
    pub system_brain: Option<String>,

    /// Conversation messages
    pub messages: Vec<Message>,

    /// Tracked files in the conversation
    pub tracked_files: Vec<TrackedFile>,

    /// Current token count estimate
    pub token_count: usize,

    /// Maximum context tokens
    pub max_tokens: usize,
}

/// A file tracked in the conversation
#[derive(Debug, Clone)]
pub struct TrackedFile {
    pub id: Uuid,
    pub path: PathBuf,
    pub content: Option<String>,
    pub token_count: usize,
}

impl AgentContext {
    /// Create a new agent context for a session
    pub fn new(session_id: Uuid, max_tokens: usize) -> Self {
        Self {
            session_id,
            system_brain: None,
            messages: Vec::new(),
            tracked_files: Vec::new(),
            token_count: 0,
            max_tokens,
        }
    }

    /// Set the system brain
    pub fn with_system_brain(mut self, prompt: String) -> Self {
        self.token_count += Self::estimate_tokens(&prompt);
        self.system_brain = Some(prompt);
        self
    }

    /// Add a message to the context
    pub fn add_message(&mut self, message: Message) {
        // Estimate tokens for the message
        let tokens = self.estimate_message_tokens(&message);
        self.token_count += tokens;
        self.messages.push(message);
    }

    /// Convert database messages to LLM messages
    pub fn from_db_messages(
        session_id: Uuid,
        db_messages: Vec<DbMessage>,
        max_tokens: usize,
    ) -> Self {
        let mut context = Self::new(session_id, max_tokens);

        for db_msg in db_messages {
            // Skip messages with empty content — Anthropic rejects empty text blocks
            if db_msg.content.is_empty() {
                continue;
            }

            let role = match db_msg.role.as_str() {
                "user" => Role::User,
                "assistant" => Role::Assistant,
                "system" => Role::System,
                _ => Role::User, // Default fallback
            };

            let message = Message {
                role,
                content: vec![ContentBlock::Text {
                    text: db_msg.content,
                }],
            };

            context.add_message(message);
        }

        context
    }

    /// Track a file in the conversation
    pub fn track_file(&mut self, file: TrackedFile) {
        self.token_count += file.token_count;
        self.tracked_files.push(file);
    }

    /// Check if context would exceed limit with additional tokens
    pub fn would_exceed_limit(&self, additional_tokens: usize) -> bool {
        self.token_count + additional_tokens > self.max_tokens
    }

    /// Estimate tokens for a message
    fn estimate_message_tokens(&self, message: &Message) -> usize {
        let mut tokens = 0;

        for content in &message.content {
            match content {
                ContentBlock::Text { text } => {
                    tokens += Self::estimate_tokens(text);
                }
                ContentBlock::ToolUse { name, input, .. } => {
                    tokens += Self::estimate_tokens(name);
                    tokens += Self::estimate_tokens(&input.to_string());
                }
                ContentBlock::ToolResult { content, .. } => {
                    tokens += Self::estimate_tokens(content);
                }
                ContentBlock::Image { .. } => {
                    // Images use a fixed token count (approximate)
                    tokens += 1000;
                }
                ContentBlock::Thinking { thinking, .. } => {
                    tokens += Self::estimate_tokens(thinking);
                }
            }
        }

        // Add overhead for message structure
        tokens + 4
    }

    /// Token estimation using tiktoken cl100k_base BPE encoding.
    /// No more chars/N guessing — this gives real token counts.
    pub fn estimate_tokens(text: &str) -> usize {
        tokenizer::count_tokens(text)
    }

    /// Static version of estimate_message_tokens — usable without a &self reference.
    pub fn estimate_tokens_static(message: &Message) -> usize {
        let mut tokens = 0;
        for content in &message.content {
            match content {
                ContentBlock::Text { text } => {
                    tokens += Self::estimate_tokens(text);
                }
                ContentBlock::ToolUse { name, input, .. } => {
                    tokens += Self::estimate_tokens(name);
                    tokens += Self::estimate_tokens(&input.to_string());
                }
                ContentBlock::ToolResult { content, .. } => {
                    tokens += Self::estimate_tokens(content);
                }
                ContentBlock::Image { .. } => {
                    tokens += 1000;
                }
                ContentBlock::Thinking { thinking, .. } => {
                    tokens += Self::estimate_tokens(thinking);
                }
            }
        }
        tokens + 4
    }

    /// Get the current token usage percentage
    pub fn usage_percentage(&self) -> f64 {
        (self.token_count as f64 / self.max_tokens as f64) * 100.0
    }

    /// Returns true if a message consists entirely of ToolResult blocks.
    /// Such a message is "orphaned" if the preceding assistant(ToolUse) message
    /// was removed, and will cause the API to reject the conversation.
    fn is_orphaned_tool_result_msg(msg: &Message) -> bool {
        msg.role == Role::User
            && !msg.content.is_empty()
            && msg
                .content
                .iter()
                .all(|b| matches!(b, ContentBlock::ToolResult { .. }))
    }

    /// Remove any leading user messages that consist solely of ToolResult blocks.
    /// Called after trimming to prevent orphaned tool results at the start of history.
    fn drop_leading_orphan_tool_results(&mut self) {
        while self
            .messages
            .first()
            .is_some_and(Self::is_orphaned_tool_result_msg)
        {
            let tokens = self.estimate_message_tokens(&self.messages[0]);
            self.token_count = self.token_count.saturating_sub(tokens);
            self.messages.remove(0);
        }
    }

    /// Trim old messages if context is too large
    pub fn trim_to_fit(&mut self, required_space: usize) {
        while self.would_exceed_limit(required_space) && !self.messages.is_empty() {
            // Remove the oldest user/assistant message pair
            if let Some(first_msg) = self.messages.first() {
                let tokens = self.estimate_message_tokens(first_msg);
                self.token_count = self.token_count.saturating_sub(tokens);
                self.messages.remove(0);
            }
        }
        // Removing an assistant(tool_use) exposes an orphaned user(tool_result) — drop it
        self.drop_leading_orphan_tool_results();
    }

    /// Hard-truncate old messages until token count is at or below `target_tokens`.
    /// Keeps at least 2 messages (the most recent pair) to maintain conversation validity.
    pub fn hard_truncate_to(&mut self, target_tokens: usize) {
        while self.token_count > target_tokens && self.messages.len() > 2 {
            let tokens = self.estimate_message_tokens(&self.messages[0]);
            self.token_count = self.token_count.saturating_sub(tokens);
            self.messages.remove(0);
        }
        self.drop_leading_orphan_tool_results();
    }

    /// Compact the context by replacing old messages with a summary.
    ///
    /// Keeps the most recent messages that fit within the token budget
    /// and prepends a summary of everything that was trimmed.
    /// `keep_token_budget` is the max tokens for kept messages (excluding the summary).
    pub fn compact_with_summary(&mut self, summary: String, keep_token_budget: usize) {
        // Walk backwards from end, keeping messages until we hit the budget
        let summary_tokens = Self::estimate_tokens(&summary) + 50; // +50 for the marker text
        let available = keep_token_budget.saturating_sub(summary_tokens);
        let mut running = 0usize;
        let mut keep_count = 0usize;
        for msg in self.messages.iter().rev() {
            let t = self.estimate_message_tokens(msg);
            if running + t > available {
                break;
            }
            running += t;
            keep_count += 1;
        }
        // Keep at least 2 messages (most recent pair) if possible
        keep_count = keep_count.max(2.min(self.messages.len()));
        let mut keep_start = self.messages.len().saturating_sub(keep_count);

        // Advance past any leading orphaned tool_result messages in the kept slice.
        // If the assistant(tool_use) that precedes them is being dropped, they'd be invalid.
        while keep_start < self.messages.len()
            && Self::is_orphaned_tool_result_msg(&self.messages[keep_start])
        {
            keep_start += 1;
        }

        let kept_messages: Vec<Message> = self.messages.drain(keep_start..).collect();

        // Clear all old messages
        self.messages.clear();

        // Prepend the compaction summary as a user message (so the LLM sees the context)
        let summary_msg = Message {
            role: Role::User,
            content: vec![ContentBlock::Text {
                text: format!(
                    "[CONTEXT COMPACTION — The conversation was automatically compacted. \
                     Below is a structured summary of everything before this point.]\n\n{}",
                    summary
                ),
            }],
        };
        self.messages.push(summary_msg);

        // Re-add kept messages
        self.messages.extend(kept_messages);

        // Recalculate token count
        self.token_count = 0;
        if let Some(brain) = &self.system_brain {
            self.token_count += Self::estimate_tokens(brain);
        }
        for msg in &self.messages {
            self.token_count += self.estimate_message_tokens(msg);
        }
    }
}

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

    #[test]
    fn test_context_creation() {
        let session_id = Uuid::new_v4();
        let context = AgentContext::new(session_id, 4096);

        assert_eq!(context.session_id, session_id);
        assert_eq!(context.max_tokens, 4096);
        assert_eq!(context.token_count, 0);
        assert!(context.messages.is_empty());
    }

    #[test]
    fn test_add_message() {
        let session_id = Uuid::new_v4();
        let mut context = AgentContext::new(session_id, 4096);

        let message = Message::user("Hello, how are you?");
        context.add_message(message);

        assert_eq!(context.messages.len(), 1);
        assert!(context.token_count > 0);
    }

    #[test]
    fn test_system_brain() {
        let session_id = Uuid::new_v4();
        let context = AgentContext::new(session_id, 4096)
            .with_system_brain("You are a helpful assistant.".to_string());

        assert!(context.system_brain.is_some());
        assert!(context.token_count > 0);
    }

    #[test]
    fn test_token_estimation() {
        let tokens = AgentContext::estimate_tokens("Hello world");
        assert!(tokens > 0);
        assert!(tokens < 10); // Should be around 2-3 tokens
    }

    #[test]
    fn test_would_exceed_limit() {
        let session_id = Uuid::new_v4();
        let mut context = AgentContext::new(session_id, 100);

        let message = Message::user("Hello");
        context.add_message(message);

        assert!(!context.would_exceed_limit(10));
        assert!(context.would_exceed_limit(1000));
    }

    #[test]
    fn test_usage_percentage() {
        let session_id = Uuid::new_v4();
        let mut context = AgentContext::new(session_id, 100);

        // Add message that uses ~50 tokens
        let long_text = "a".repeat(200); // ~50 tokens
        let message = Message::user(long_text);
        context.add_message(message);

        let usage = context.usage_percentage();
        assert!(usage > 0.0 && usage <= 100.0);
    }

    #[test]
    fn test_trim_to_fit() {
        let session_id = Uuid::new_v4();
        let mut context = AgentContext::new(session_id, 100);

        // Add several messages with longer text to ensure they exceed limit
        for i in 0..5 {
            let long_text = format!(
                "This is a longer message {} that will use more tokens to ensure we actually need to trim",
                i
            );
            let message = Message::user(long_text);
            context.add_message(message);
        }

        let original_count = context.messages.len();
        context.trim_to_fit(10); // Require 10 tokens space, forcing trimming

        // Should have removed some messages
        assert!(context.messages.len() < original_count);
    }

    #[test]
    fn test_compact_with_summary_keeps_recent() {
        let session_id = Uuid::new_v4();
        let mut context = AgentContext::new(session_id, 10000);

        // Add 10 messages
        for i in 0..10 {
            context.add_message(Message::user(format!("Message {}", i)));
        }
        assert_eq!(context.messages.len(), 10);

        // Use 80% of max_tokens as budget — should keep all short messages
        let budget = (10000.0 * 0.80) as usize;
        context.compact_with_summary("Summary of old messages".to_string(), budget);

        // First message should be the compaction summary
        if let Some(ContentBlock::Text { text }) = context.messages[0].content.first() {
            assert!(text.contains("CONTEXT COMPACTION"));
            assert!(text.contains("Summary of old messages"));
        } else {
            panic!("First message should be a text compaction summary");
        }

        // Last kept message should be Message 9
        if let Some(ContentBlock::Text { text }) = context.messages.last().unwrap().content.first()
        {
            assert!(text.contains("Message 9"));
        } else {
            panic!("Last message should be Message 9");
        }
    }

    #[test]
    fn test_compact_with_summary_recalculates_tokens() {
        let session_id = Uuid::new_v4();
        let mut context = AgentContext::new(session_id, 10000);

        // Add many large messages to build up token count
        for i in 0..20 {
            let big_text = format!("Large message {} {}", i, "x".repeat(400));
            context.add_message(Message::user(big_text));
        }

        let tokens_before = context.token_count;
        assert!(tokens_before > 0);

        // Very small budget — should drop most messages
        context.compact_with_summary("Brief summary".to_string(), 500);

        // Token count should be recalculated and less than before
        assert!(context.token_count < tokens_before);
        assert!(context.token_count > 0);
    }

    #[test]
    fn test_compact_with_summary_fewer_messages_than_keep() {
        let session_id = Uuid::new_v4();
        let mut context = AgentContext::new(session_id, 10000);

        // Add only 2 messages — large budget should keep them all
        context.add_message(Message::user("Hello".to_string()));
        context.add_message(Message::user("World".to_string()));

        context.compact_with_summary("Summary".to_string(), 8000);

        // Should have: 1 summary + 2 original = 3
        assert_eq!(context.messages.len(), 3);
    }

    #[test]
    fn test_compact_with_summary_preserves_system_brain_tokens() {
        let session_id = Uuid::new_v4();
        let mut context = AgentContext::new(session_id, 10000)
            .with_system_brain("You are an AI assistant".to_string());

        for i in 0..5 {
            context.add_message(Message::user(format!("Msg {}", i)));
        }

        context.compact_with_summary("Summary".to_string(), 500);

        // Token count should include system brain tokens
        let brain_tokens = AgentContext::estimate_tokens("You are an AI assistant");
        assert!(context.token_count >= brain_tokens);
    }

    #[test]
    fn test_compact_empty_context() {
        let session_id = Uuid::new_v4();
        let mut context = AgentContext::new(session_id, 10000);

        // No messages, compact should still work
        context.compact_with_summary("Summary of nothing".to_string(), 8000);

        // Should have just the summary message
        assert_eq!(context.messages.len(), 1);
    }
}