harn-vm 0.5.4

use std::cell::RefCell;

use super::api::LlmResult;

/// LLM replay mode.
#[derive(Debug, Clone, Copy, PartialEq)]
pub enum LlmReplayMode {
    Off,
    Record,
    Replay,
}

thread_local! {
    static LLM_REPLAY_MODE: RefCell<LlmReplayMode> = const { RefCell::new(LlmReplayMode::Off) };
    static LLM_FIXTURE_DIR: RefCell<String> = const { RefCell::new(String::new()) };
}

/// Set LLM replay mode (record/replay) and fixture directory.
pub fn set_replay_mode(mode: LlmReplayMode, fixture_dir: &str) {
    LLM_REPLAY_MODE.with(|v| *v.borrow_mut() = mode);
    LLM_FIXTURE_DIR.with(|v| *v.borrow_mut() = fixture_dir.to_string());
}

pub(crate) fn get_replay_mode() -> LlmReplayMode {
    LLM_REPLAY_MODE.with(|v| *v.borrow())
}

pub(crate) fn get_fixture_dir() -> String {
    LLM_FIXTURE_DIR.with(|v| v.borrow().clone())
}

/// Hash a request for fixture file naming using canonical JSON serialization.
pub(crate) fn fixture_hash(
    model: &str,
    messages: &[serde_json::Value],
    system: Option<&str>,
) -> String {
    use std::hash::{Hash, Hasher};
    let mut hasher = std::collections::hash_map::DefaultHasher::new();
    model.hash(&mut hasher);
    // Use canonical JSON string (not Debug format) for stable hashing
    serde_json::to_string(messages)
        .unwrap_or_default()
        .hash(&mut hasher);
    system.hash(&mut hasher);
    format!("{:016x}", hasher.finish())
}

pub(crate) fn save_fixture(hash: &str, result: &LlmResult) {
    let dir = get_fixture_dir();
    if dir.is_empty() {
        return;
    }
    let _ = std::fs::create_dir_all(&dir);
    let path = format!("{dir}/{hash}.json");
    let json = serde_json::json!({
        "text": result.text,
        "tool_calls": result.tool_calls,
        "input_tokens": result.input_tokens,
        "output_tokens": result.output_tokens,
        "model": result.model,
        "provider": result.provider,
        "blocks": result.blocks,
    });
    let _ = std::fs::write(
        &path,
        serde_json::to_string_pretty(&json).unwrap_or_default(),
    );
}

pub(crate) fn load_fixture(hash: &str) -> Option<LlmResult> {
    let dir = get_fixture_dir();
    if dir.is_empty() {
        return None;
    }
    let path = format!("{dir}/{hash}.json");
    let content = std::fs::read_to_string(&path).ok()?;
    let json: serde_json::Value = serde_json::from_str(&content).ok()?;
    Some(LlmResult {
        text: json["text"].as_str().unwrap_or("").to_string(),
        tool_calls: json["tool_calls"].as_array().cloned().unwrap_or_default(),
        input_tokens: json["input_tokens"].as_i64().unwrap_or(0),
        output_tokens: json["output_tokens"].as_i64().unwrap_or(0),
        model: json["model"].as_str().unwrap_or("").to_string(),
        provider: json["provider"].as_str().unwrap_or("mock").to_string(),
        thinking: json["thinking"].as_str().map(|s| s.to_string()),
        stop_reason: json["stop_reason"].as_str().map(|s| s.to_string()),
        blocks: json["blocks"].as_array().cloned().unwrap_or_default(),
    })
}

/// Mock LLM provider -- deterministic responses for testing without API keys.
pub(crate) fn mock_llm_response(
    messages: &[serde_json::Value],
    system: Option<&str>,
    native_tools: Option<&[serde_json::Value]>,
) -> LlmResult {
    // Extract the last user message for generating a deterministic response.
    let last_msg = messages
        .last()
        .and_then(|m| m.get("content"))
        .and_then(|c| c.as_str())
        .unwrap_or("");

    // If tools are provided, generate a mock tool call for the first tool.
    if let Some(tools) = native_tools {
        if let Some(first_tool) = tools.first() {
            let tool_name = first_tool
                .get("name")
                .or_else(|| first_tool.get("function").and_then(|f| f.get("name")))
                .and_then(|n| n.as_str())
                .unwrap_or("unknown");
            return LlmResult {
                text: String::new(),
                tool_calls: vec![serde_json::json!({
                    "id": "mock_call_1",
                    "type": "function",
                    "function": {
                        "name": tool_name,
                        "arguments": "{}"
                    }
                })],
                input_tokens: last_msg.len() as i64,
                output_tokens: 20,
                model: "mock".to_string(),
                provider: "mock".to_string(),
                thinking: None,
                stop_reason: None,
                blocks: vec![serde_json::json!({
                    "type": "tool_call",
                    "id": "mock_call_1",
                    "name": tool_name,
                    "arguments": {},
                    "visibility": "internal",
                })],
            };
        }
    }

    // Generate response based on the prompt content.
    // Include ##DONE## if the system prompt mentions it (agent_loop compatibility).
    let done_sentinel = if system.is_some_and(|s| s.contains("##DONE##")) {
        " ##DONE##"
    } else {
        ""
    };

    let response = if last_msg.is_empty() {
        format!("Mock LLM response{done_sentinel}")
    } else {
        let word_count = last_msg.split_whitespace().count();
        format!(
            "Mock response to {word_count}-word prompt: {}{done_sentinel}",
            last_msg.chars().take(100).collect::<String>()
        )
    };

    LlmResult {
        text: response.clone(),
        tool_calls: vec![],
        input_tokens: last_msg.len() as i64,
        output_tokens: 30,
        model: "mock".to_string(),
        provider: "mock".to_string(),
        thinking: None,
        stop_reason: None,
        blocks: vec![serde_json::json!({
            "type": "output_text",
            "text": response,
            "visibility": "public",
        })],
    }
}