// agent.rs — Core agent loop
//
// The simplest possible implementation of the agent pattern:
// send messages + tool definitions to the model, if it responds
// with tool calls then dispatch them and loop, if it responds
// with text then display it and wait for the next prompt.
//
// Uses streaming by default so text tokens appear as they're
// generated. Tool calls are accumulated from stream deltas and
// dispatched after the stream completes.
//
// The DMN (dmn.rs) is the outer loop that decides what prompts
// to send here. This module just handles single turns: prompt
// in, response out, tool calls dispatched.

pub mod api;
pub mod context;
pub mod oneshot;
pub mod tokenizer;
pub mod tools;

use std::sync::Arc;
use anyhow::Result;

use api::ApiClient;
use context::{AstNode, NodeBody, ContextState, Section, Ast, PendingToolCall, ResponseParser, Role};

use crate::mind::log::ConversationLog;

// --- Activity tracking (RAII guards) ---

pub struct ActivityEntry {
    pub id: u64,
    pub label: String,
    pub started: std::time::Instant,
    /// Auto-expires this long after creation (or completion).
    pub expires_at: std::time::Instant,
}

pub struct ActivityGuard {
    agent: Arc<Agent>,
    id: u64,
}

const ACTIVITY_LINGER: std::time::Duration = std::time::Duration::from_secs(5);

impl Drop for ActivityGuard {
    fn drop(&mut self) {
        if let Ok(mut st) = self.agent.state.try_lock() {
            if let Some(entry) = st.activities.iter_mut().find(|a| a.id == self.id) {
                entry.label.push_str(" (complete)");
                entry.expires_at = std::time::Instant::now() + ACTIVITY_LINGER;
            }
        }
    }
}

impl AgentState {
    pub fn push_activity(&mut self, label: impl Into<String>) -> u64 {
        self.expire_activities();
        let id = self.next_activity_id;
        self.next_activity_id += 1;
        self.activities.push(ActivityEntry {
            id, label: label.into(),
            started: std::time::Instant::now(),
            expires_at: std::time::Instant::now() + std::time::Duration::from_secs(3600),
        });
        self.changed.notify_one();
        id
    }

    pub fn notify(&mut self, label: impl Into<String>) {
        self.expire_activities();
        let id = self.next_activity_id;
        self.next_activity_id += 1;
        self.activities.push(ActivityEntry {
            id, label: label.into(),
            started: std::time::Instant::now(),
            expires_at: std::time::Instant::now() + ACTIVITY_LINGER,
        });
        self.changed.notify_one();
    }

    pub fn expire_activities(&mut self) {
        let now = std::time::Instant::now();
        self.activities.retain(|a| a.expires_at > now);
    }
}

pub async fn start_activity(agent: &Arc<Agent>, label: impl Into<String>) -> ActivityGuard {
    let id = agent.state.lock().await.push_activity(label);
    ActivityGuard { agent: agent.clone(), id }
}

/// Result of a single agent turn.
pub struct TurnResult {
    /// The text response (already sent through UI channel).
    #[allow(dead_code)]
    pub text: String,
    /// Whether the model called yield_to_user during this turn.
    pub yield_requested: bool,
    /// Whether any tools (other than yield_to_user) were called.
    pub had_tool_calls: bool,
    /// Number of tool calls that returned errors this turn.
    pub tool_errors: u32,
    /// Model name to switch to after this turn completes.
    pub model_switch: Option<String>,
    /// Agent requested DMN pause (full stop on autonomous behavior).
    pub dmn_pause: bool,
}

/// Accumulated state across tool dispatches within a single turn.
struct DispatchState {
    yield_requested: bool,
    had_tool_calls: bool,
    tool_errors: u32,
    model_switch: Option<String>,
    dmn_pause: bool,
}

impl DispatchState {
    fn new() -> Self {
        Self {
            yield_requested: false, had_tool_calls: false,
            tool_errors: 0, model_switch: None, dmn_pause: false,
        }
    }
}

/// Immutable agent config — shared via Arc, no mutex needed.
pub struct Agent {
    pub client: ApiClient,
    pub app_config: crate::config::AppConfig,
    pub prompt_file: String,
    pub session_id: String,
    pub context: tokio::sync::Mutex<ContextState>,
    pub state: tokio::sync::Mutex<AgentState>,
}

/// Mutable agent state — behind its own mutex.
pub struct AgentState {
    pub tools: Vec<tools::Tool>,
    pub last_prompt_tokens: u32,
    pub reasoning_effort: String,
    pub temperature: f32,
    pub top_p: f32,
    pub top_k: u32,
    pub activities: Vec<ActivityEntry>,
    next_activity_id: u64,
    pub pending_yield: bool,
    pub pending_model_switch: Option<String>,
    pub pending_dmn_pause: bool,
    pub provenance: String,
    pub conversation_log: Option<ConversationLog>,
    pub generation: u64,
    pub memory_scoring_in_flight: bool,
    pub active_tools: tools::ActiveTools,
    pub changed: Arc<tokio::sync::Notify>,
}

impl Agent {
    pub async fn new(
        client: ApiClient,
        system_prompt: String,
        personality: Vec<(String, String)>,
        app_config: crate::config::AppConfig,
        prompt_file: String,
        conversation_log: Option<ConversationLog>,
        active_tools: tools::ActiveTools,
    ) -> Arc<Self> {
        let mut context = ContextState::new();
        context.push(Section::System, AstNode::system_msg(&system_prompt));

        let tool_defs: Vec<String> = tools::tools().iter()
            .map(|t| t.to_json()).collect();
        if !tool_defs.is_empty() {
            let tools_text = format!(
                "# Tools\n\nYou have access to the following functions:\n\n<tools>\n{}\n</tools>\n\n\
                If you choose to call a function ONLY reply in the following format with NO suffix:\n\n\
                <tool_call>\n<function=example_function_name>\n\
                <parameter=example_parameter_1>\nvalue_1\n</parameter>\n\
                </function>\n</tool_call>\n\n\
                IMPORTANT: Function calls MUST follow the specified format.",
                tool_defs.join("\n"),
            );
            context.push(Section::System, AstNode::system_msg(&tools_text));
        }

        for (name, content) in &personality {
            context.push(Section::Identity, AstNode::memory(name, content));
        }

        let session_id = format!("consciousness-{}", chrono::Utc::now().format("%Y%m%d-%H%M%S"));
        let agent = Arc::new(Self {
            client,
            app_config,
            prompt_file,
            session_id,
            context: tokio::sync::Mutex::new(context),
            state: tokio::sync::Mutex::new(AgentState {
                tools: tools::tools(),
                last_prompt_tokens: 0,
                reasoning_effort: "none".to_string(),
                temperature: 0.6,
                top_p: 0.95,
                top_k: 20,
                activities: Vec::new(),
                next_activity_id: 0,
                pending_yield: false,
                pending_model_switch: None,
                pending_dmn_pause: false,
                provenance: "manual".to_string(),
                conversation_log,
                generation: 0,
                memory_scoring_in_flight: false,
                active_tools,
                changed: Arc::new(tokio::sync::Notify::new()),
            }),
        });

        agent.load_startup_journal().await;
        agent
    }

    /// Fork: clones context for KV cache prefix sharing.
    pub async fn fork(self: &Arc<Self>, tools: Vec<tools::Tool>) -> Arc<Self> {
        let ctx = self.context.lock().await.clone();
        let st = self.state.lock().await;
        Arc::new(Self {
            client: self.client.clone(),
            app_config: self.app_config.clone(),
            prompt_file: self.prompt_file.clone(),
            session_id: self.session_id.clone(),
            context: tokio::sync::Mutex::new(ctx),
            state: tokio::sync::Mutex::new(AgentState {
                tools,
                last_prompt_tokens: 0,
                reasoning_effort: "none".to_string(),
                temperature: st.temperature,
                top_p: st.top_p,
                top_k: st.top_k,
                activities: Vec::new(),
                next_activity_id: 0,
                pending_yield: false,
                pending_model_switch: None,
                pending_dmn_pause: false,
                provenance: st.provenance.clone(),
                conversation_log: None,
                generation: 0,
                memory_scoring_in_flight: false,
                active_tools: tools::ActiveTools::new(),
                changed: Arc::new(tokio::sync::Notify::new()),
            }),
        })
    }

    pub async fn assemble_prompt_tokens(&self) -> Vec<u32> {
        let ctx = self.context.lock().await;
        let mut tokens = ctx.token_ids();
        tokens.push(tokenizer::IM_START);
        tokens.extend(tokenizer::encode("assistant\n"));
        tokens
    }

    pub async fn push_node(&self, node: AstNode) {
        let st = self.state.lock().await;
        if let Some(ref log) = st.conversation_log {
            if let Err(e) = log.append_node(&node) {
                eprintln!("warning: failed to log entry: {:#}", e);
            }
        }
        drop(st);
        self.context.lock().await.push(Section::Conversation, node);
        self.state.lock().await.changed.notify_one();
    }

    /// Run the agent turn loop: assemble prompt, stream response,
    /// parse into AST, dispatch tool calls, repeat until text response.
    pub async fn turn(
        agent: Arc<Agent>,
    ) -> Result<TurnResult> {
        // Collect finished background tools
        {
            let finished = agent.state.lock().await.active_tools.take_finished();
            if !finished.is_empty() {
                let mut bg_ds = DispatchState::new();
                for entry in finished {
                    if let Ok((call, output)) = entry.handle.await {
                        Agent::apply_tool_result(&agent, &call, output, &mut bg_ds).await;
                    }
                }
            }
        }

        let mut overflow_retries: u32 = 0;
        let mut empty_retries: u32 = 0;
        let mut ds = DispatchState::new();

        loop {
            let _thinking = start_activity(&agent, "thinking...").await;

            let (rx, _stream_guard) = {
                let prompt_tokens = agent.assemble_prompt_tokens().await;
                let st = agent.state.lock().await;
                agent.client.stream_completion(
                    &prompt_tokens,
                    api::SamplingParams {
                        temperature: st.temperature,
                        top_p: st.top_p,
                        top_k: st.top_k,
                    },
                    None,
                )
            };

            let branch_idx = {
                let mut ctx = agent.context.lock().await;
                let idx = ctx.len(Section::Conversation);
                ctx.push(Section::Conversation,
                    AstNode::branch(Role::Assistant, vec![]));
                idx
            };

            let parser = ResponseParser::new(branch_idx);
            let (mut tool_rx, parser_handle) = parser.run(rx, agent.clone());

            let mut pending_calls: Vec<PendingToolCall> = Vec::new();
            while let Some(call) = tool_rx.recv().await {
                let call_clone = call.clone();
                let agent_handle = agent.clone();
                let handle = tokio::spawn(async move {
                    let args: serde_json::Value =
                        serde_json::from_str(&call_clone.arguments).unwrap_or_default();
                    let output = tools::dispatch_with_agent(
                        &call_clone.name, &args, Some(agent_handle),
                    ).await;
                    (call_clone, output)
                });
                agent.state.lock().await.active_tools.push(tools::ActiveToolCall {
                    id: call.id.clone(),
                    name: call.name.clone(),
                    detail: call.arguments.clone(),
                    started: std::time::Instant::now(),
                    background: false,
                    handle,
                });
                pending_calls.push(call);
            }

            // Check for stream/parse errors
            match parser_handle.await {
                Ok(Err(e)) => {
                    if context::is_context_overflow(&e) && overflow_retries < 2 {
                        overflow_retries += 1;
                        agent.state.lock().await.notify(
                            format!("context overflow — retrying ({}/2)", overflow_retries));
                        agent.compact().await;
                        continue;
                    }
                    return Err(e);
                }
                Err(e) => return Err(anyhow::anyhow!("parser task panicked: {}", e)),
                Ok(Ok(())) => {}
            }

            // Empty response — nudge and retry
            let has_content = {
                let ctx = agent.context.lock().await;
                !ctx.conversation()[branch_idx].children().is_empty()
            };
            if !has_content && pending_calls.is_empty() {
                if empty_retries < 2 {
                    empty_retries += 1;
                    agent.push_node(AstNode::user_msg(
                        "[system] Your previous response was empty. \
                         Please respond with text or use a tool."
                    )).await;
                    continue;
                }
            } else {
                empty_retries = 0;
            }

            // Wait for tool calls to complete
            if !pending_calls.is_empty() {
                ds.had_tool_calls = true;

                let handles = agent.state.lock().await.active_tools.take_foreground();
                for entry in handles {
                    if let Ok((call, output)) = entry.handle.await {
                        Agent::apply_tool_result(&agent, &call, output, &mut ds).await;
                    }
                }
                continue;
            }

            // Text-only response — extract text and return
            let text = {
                let ctx = agent.context.lock().await;
                let children = ctx.conversation()[branch_idx].children();
                children.iter()
                    .filter_map(|c| c.leaf())
                    .filter(|l| matches!(l.body(), NodeBody::Content(_)))
                    .map(|l| l.body().text())
                    .collect::<Vec<_>>()
                    .join("")
            };

            let mut st = agent.state.lock().await;
            if st.pending_yield { ds.yield_requested = true; st.pending_yield = false; }
            if st.pending_model_switch.is_some() { ds.model_switch = st.pending_model_switch.take(); }
            if st.pending_dmn_pause { ds.dmn_pause = true; st.pending_dmn_pause = false; }

            return Ok(TurnResult {
                text,
                yield_requested: ds.yield_requested,
                had_tool_calls: ds.had_tool_calls,
                tool_errors: ds.tool_errors,
                model_switch: ds.model_switch,
                dmn_pause: ds.dmn_pause,
            });
        }
    }

    async fn apply_tool_result(
        agent: &Arc<Agent>,
        call: &PendingToolCall,
        output: String,
        ds: &mut DispatchState,
    ) {
        ds.had_tool_calls = true;
        if output.starts_with("Error:") {
            ds.tool_errors += 1;
        }

        agent.state.lock().await.active_tools.remove(&call.id);

        if call.name == "memory_render" && !output.starts_with("Error:") {
            let args: serde_json::Value =
                serde_json::from_str(&call.arguments).unwrap_or_default();
            if let Some(key) = args.get("key").and_then(|v| v.as_str()) {
                agent.push_node(AstNode::memory(key, &output)).await;
                return;
            }
        }

        agent.push_node(AstNode::tool_result(&output)).await;
    }

    async fn load_startup_journal(&self) {
        let oldest_msg_ts = {
            let st = self.state.lock().await;
            st.conversation_log.as_ref().and_then(|log| log.oldest_timestamp())
        };

        let store = match crate::store::Store::load() {
            Ok(s) => s,
            Err(_) => return,
        };

        let mut journal_nodes: Vec<_> = store.nodes.values()
            .filter(|n| n.node_type == crate::store::NodeType::EpisodicSession)
            .collect();
        journal_nodes.sort_by_key(|n| n.created_at);

        let cutoff_idx = if let Some(cutoff) = oldest_msg_ts {
            let cutoff_ts = cutoff.timestamp();
            let mut idx = journal_nodes.len();
            for (i, node) in journal_nodes.iter().enumerate() {
                if node.created_at >= cutoff_ts {
                    idx = i + 1;
                    break;
                }
            }
            idx
        } else {
            journal_nodes.len()
        };

        let journal_budget = context::context_window() * 15 / 100;
        let mut entries = Vec::new();
        let mut total_tokens = 0;

        for node in journal_nodes[..cutoff_idx].iter().rev() {
            let ts = chrono::DateTime::from_timestamp(node.created_at, 0);
            let ast = AstNode::memory(&node.key, &node.content)
                .with_timestamp(ts.unwrap_or_else(chrono::Utc::now));
            let tok = ast.tokens();
            if total_tokens + tok > journal_budget && !entries.is_empty() {
                break;
            }
            total_tokens += tok;
            entries.push(ast);
        }
        entries.reverse();

        if entries.is_empty() { return; }

        let mut ctx = self.context.lock().await;
        ctx.clear(Section::Journal);
        for entry in entries {
            ctx.push(Section::Journal, entry);
        }
    }

    pub async fn compact(&self) {
        match crate::config::reload_for_model(&self.app_config, &self.prompt_file) {
            Ok((system_prompt, personality)) => {
                let mut ctx = self.context.lock().await;
                ctx.clear(Section::System);
                ctx.push(Section::System, AstNode::system_msg(&system_prompt));
                ctx.clear(Section::Identity);
                for (name, content) in &personality {
                    ctx.push(Section::Identity, AstNode::memory(name, content));
                }
            }
            Err(e) => {
                eprintln!("warning: failed to reload identity: {:#}", e);
            }
        }

        self.load_startup_journal().await;

        let mut st = self.state.lock().await;
        st.generation += 1;
        st.last_prompt_tokens = 0;
    }

    pub async fn restore_from_log(&self) -> bool {
        let nodes = {
            let st = self.state.lock().await;
            match &st.conversation_log {
                Some(log) => match log.read_nodes(64 * 1024 * 1024) {
                    Ok(nodes) if !nodes.is_empty() => nodes,
                    _ => return false,
                },
                None => return false,
            }
        };

        {
            let mut ctx = self.context.lock().await;
            ctx.clear(Section::Conversation);
            for node in nodes {
                ctx.push(Section::Conversation, node);
            }
        }
        self.compact().await;
        let mut st = self.state.lock().await;
        st.last_prompt_tokens = self.context.lock().await.tokens() as u32;
        true
    }

    pub fn model(&self) -> &str {
        &self.client.model
    }
}