// 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 tools::summarize_args;

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,
}

/// RAII guard — marks the activity "(complete)" on drop, starts expiry timer.
pub struct ActivityGuard {
    agent: Arc<tokio::sync::Mutex<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 ag) = self.agent.try_lock() {
            if let Some(entry) = ag.activities.iter_mut().find(|a| a.id == self.id) {
                entry.label.push_str(" (complete)");
                entry.expires_at = std::time::Instant::now() + ACTIVITY_LINGER;
            }
        }
    }
}

impl Agent {
    /// Register an activity, returns its ID. Caller creates the guard.
    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
    }

    /// Push a notification — auto-expires after 5 seconds.
    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();
    }

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

/// Create an activity guard from outside the lock.
pub fn activity_guard(agent: &Arc<tokio::sync::Mutex<Agent>>, id: u64) -> ActivityGuard {
    ActivityGuard { agent: agent.clone(), id }
}

/// Convenience: lock, push activity, unlock, return guard.
pub async fn start_activity(agent: &Arc<tokio::sync::Mutex<Agent>>, label: impl Into<String>) -> ActivityGuard {
    let id = agent.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,
        }
    }
}

pub struct Agent {
    client: ApiClient,
    tools: Vec<tools::Tool>,
    /// Last known prompt token count from the API (tracks context size).
    last_prompt_tokens: u32,
    /// Current reasoning effort level ("none", "low", "high").
    pub reasoning_effort: String,
    /// Sampling parameters — adjustable at runtime from the thalamus screen.
    pub temperature: f32,
    pub top_p: f32,
    pub top_k: u32,
    /// Active activities — RAII guards auto-remove on drop.
    pub activities: Vec<ActivityEntry>,
    next_activity_id: u64,
    /// Control tool flags — set by tool handlers, consumed by turn loop.
    pub pending_yield: bool,
    pub pending_model_switch: Option<String>,
    pub pending_dmn_pause: bool,
    /// Provenance tag for memory operations — identifies who made the change.
    pub provenance: String,
    /// Persistent conversation log — append-only record of all messages.
    pub conversation_log: Option<ConversationLog>,
    pub context: ContextState,
    /// App config — used to reload identity on compaction and model switching.
    pub app_config: crate::config::AppConfig,
    pub prompt_file: String,
    /// Stable session ID for memory-search dedup across turns.
    pub session_id: String,
    /// Incremented on compaction — UI uses this to detect resets.
    pub generation: u64,
    /// Whether incremental memory scoring is currently running.
    pub memory_scoring_in_flight: bool,
    /// Shared active tools — Agent writes, TUI reads.
    pub active_tools: tools::SharedActiveTools,
    /// Fires when agent state changes — UI wakes on this instead of polling.
    pub changed: Arc<tokio::sync::Notify>,
}

impl Agent {
    pub 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::SharedActiveTools,
    ) -> 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 mut agent = Self {
            client,
            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,
            context,
            app_config,
            prompt_file,
            session_id,
            generation: 0,
            memory_scoring_in_flight: false,
            active_tools,
            changed: Arc::new(tokio::sync::Notify::new()),
        };

        agent.load_startup_journal();
        agent
    }

    /// Create a lightweight agent forked from this one's context.
    ///
    /// The forked agent shares the same conversation prefix (system prompt,
    /// personality, journal, entries) for KV cache sharing. The caller
    /// appends the subconscious prompt as a user message and runs the turn.
    pub fn fork(&self, tools: Vec<tools::Tool>) -> Self {

        Self {
            client: self.client.clone(),
            tools,
            last_prompt_tokens: 0,
            reasoning_effort: "none".to_string(),
            temperature: self.temperature,
            top_p: self.top_p,
            top_k: self.top_k,
            activities: Vec::new(),
            next_activity_id: 0,
            pending_yield: false,
            pending_model_switch: None,
            pending_dmn_pause: false,
            provenance: self.provenance.clone(),
            conversation_log: None,
            context: self.context.clone(),
            app_config: self.app_config.clone(),
            prompt_file: self.prompt_file.clone(),
            session_id: self.session_id.clone(),
            generation: 0,
            memory_scoring_in_flight: false,
            active_tools: tools::shared_active_tools(),
            changed: Arc::new(tokio::sync::Notify::new()),
        }
    }

    /// Assemble the full prompt as token IDs.
    /// Context sections + assistant prompt suffix.
    pub fn assemble_prompt_tokens(&self) -> Vec<u32> {
        let mut tokens = self.context.token_ids();
        tokens.push(tokenizer::IM_START);
        tokens.extend(tokenizer::encode("assistant\n"));
        tokens
    }

    /// Push a node into the conversation and log it.
    pub fn push_node(&mut self, node: AstNode) {
        if let Some(ref log) = self.conversation_log {
            if let Err(e) = log.append_node(&node) {
                eprintln!("warning: failed to log entry: {:#}", e);
            }
        }
        self.context.push(Section::Conversation, node);
        self.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<tokio::sync::Mutex<Agent>>,
    ) -> Result<TurnResult> {
        let active_tools = {
            let me = agent.lock().await;
            me.active_tools.clone()
        };

        // Collect finished background tools
        {
            let mut finished = Vec::new();
            {
                let mut tools = active_tools.lock().unwrap();
                let mut i = 0;
                while i < tools.len() {
                    if tools[i].handle.is_finished() {
                        finished.push(tools.remove(i));
                    } else {
                        i += 1;
                    }
                }
            }
            if !finished.is_empty() {
                let mut results = Vec::new();
                for entry in finished {
                    if let Ok((call, output)) = entry.handle.await {
                        results.push((call, output));
                    }
                }
                let mut me = agent.lock().await;
                let mut bg_ds = DispatchState::new();
                for (call, output) in results {
                    me.apply_tool_result(&call, output, &mut bg_ds);
                }
            }
        }

        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;

            // Assemble prompt and start stream (brief lock)
            let (mut rx, _stream_guard) = {
                let me = agent.lock().await;
                let prompt_tokens = me.assemble_prompt_tokens();
                me.client.stream_completion(
                    &prompt_tokens,
                    api::SamplingParams {
                        temperature: me.temperature,
                        top_p: me.top_p,
                        top_k: me.top_k,
                    },
                    None,
                )
            };

            // Create assistant branch and parser (brief lock)
            let branch_idx = {
                let mut me = agent.lock().await;
                let idx = me.context.len(Section::Conversation);
                me.context.push(Section::Conversation,
                    AstNode::branch(Role::Assistant, vec![]));
                idx
            };
            let mut parser = ResponseParser::new(branch_idx);
            let mut pending_calls: Vec<PendingToolCall> = Vec::new();
            let mut had_content = false;
            let mut stream_error: Option<String> = None;

            // Stream loop — no lock held across I/O
            while let Some(event) = rx.recv().await {
                match event {
                    api::StreamToken::Token { text, id: _ } => {
                        had_content = true;
                        let mut me = agent.lock().await;
                        let calls = parser.feed(&text, &mut me.context);
                        for call in calls {
                            // Dispatch tool call immediately
                            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)
                            });
                            active_tools.lock().unwrap().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);
                        }
                    }
                    api::StreamToken::Error(e) => {
                        stream_error = Some(e);
                        break;
                    }
                    api::StreamToken::Done { usage } => {
                        if let Some(u) = usage {
                            agent.lock().await.last_prompt_tokens = u.prompt_tokens;
                        }
                        break;
                    }
                }
            }

            // Flush parser remainder
            {
                let mut me = agent.lock().await;
                parser.finish(&mut me.context);
            }

            // Handle errors
            if let Some(e) = stream_error {
                let err = anyhow::anyhow!("{}", e);
                let mut me = agent.lock().await;
                if context::is_context_overflow(&err) && overflow_retries < 2 {
                    overflow_retries += 1;
                    me.notify(format!("context overflow — retrying ({}/2)", overflow_retries));
                    me.compact();
                    continue;
                }
                if context::is_stream_error(&err) && empty_retries < 2 {
                    empty_retries += 1;
                    me.notify(format!("stream error — retrying ({}/2)", empty_retries));
                    drop(me);
                    tokio::time::sleep(std::time::Duration::from_secs(2)).await;
                    continue;
                }
                return Err(err);
            }

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

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

                // Collect non-background tool handles
                let mut handles = Vec::new();
                {
                    let mut tools_guard = active_tools.lock().unwrap();
                    let mut i = 0;
                    while i < tools_guard.len() {
                        if !tools_guard[i].background {
                            handles.push(tools_guard.remove(i));
                        } else {
                            i += 1;
                        }
                    }
                }

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

            // Text-only response — extract text and return
            let text = {
                let me = agent.lock().await;
                let children = me.context.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 me = agent.lock().await;
            if me.pending_yield { ds.yield_requested = true; me.pending_yield = false; }
            if me.pending_model_switch.is_some() { ds.model_switch = me.pending_model_switch.take(); }
            if me.pending_dmn_pause { ds.dmn_pause = true; me.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,
            });
        }
    }

    /// Dispatch a tool call without holding the agent lock across I/O.
    async fn dispatch_tool_call_unlocked(
        agent: &Arc<tokio::sync::Mutex<Agent>>,
        active_tools: &tools::SharedActiveTools,
        call: &PendingToolCall,
        ds: &mut DispatchState,
    ) {
        let args: serde_json::Value = match serde_json::from_str(&call.arguments) {
            Ok(v) => v,
            Err(e) => {
                let err = format!("Error: malformed tool call arguments: {e}");
                let _act = start_activity(agent, format!("rejected: {} (bad args)", call.name)).await;
                let mut me = agent.lock().await;
                me.apply_tool_result(call, err, ds);
                return;
            }
        };

        let args_summary = summarize_args(&call.name, &args);
        let _calling = start_activity(agent, format!("calling: {}", call.name)).await;

        let call_clone = call.clone();
        let agent_handle = agent.clone();
        let handle = tokio::spawn(async move {
            let output = tools::dispatch_with_agent(&call_clone.name, &args, Some(agent_handle)).await;
            (call_clone, output)
        });
        active_tools.lock().unwrap().push(
            tools::ActiveToolCall {
                id: call.id.clone(),
                name: call.name.clone(),
                detail: args_summary,
                started: std::time::Instant::now(),
                background: false,
                handle,
            }
        );

        let entry = {
            let mut tools = active_tools.lock().unwrap();
            tools.pop().unwrap()
        };
        if let Ok((call, output)) = entry.handle.await {
            let mut me = agent.lock().await;
            me.apply_tool_result(&call, output, ds);
        }
    }

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

        self.active_tools.lock().unwrap().retain(|t| t.id != call.id);

        // Tag memory_render results as Memory nodes for context deduplication
        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()) {
                self.push_node(AstNode::memory(key, &output));
                return;
            }
        }

        self.push_node(AstNode::tool_result(&output));
    }

    pub fn conversation_from(&self, from: usize) -> &[AstNode] {
        let conv = self.context.conversation();
        if from < conv.len() { &conv[from..] } else { &[] }
    }

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

        let oldest_msg_ts = self.conversation_log.as_ref()
            .and_then(|log| log.oldest_timestamp());

        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; }

        self.context.clear(Section::Journal);
        for entry in entries {
            self.context.push(Section::Journal, entry);
        }
    }

    pub fn last_prompt_tokens(&self) -> u32 {
        self.last_prompt_tokens
    }

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

        self.load_startup_journal();

        // TODO: trim_entries — dedup memories, evict to budget
        self.generation += 1;
        self.last_prompt_tokens = 0;
    }

    /// Restore from the conversation log.
    /// Returns true if the log had content to restore.
    pub fn restore_from_log(&mut self) -> bool {
        let nodes = match &self.conversation_log {
            Some(log) => match log.read_nodes(64 * 1024 * 1024) {
                Ok(nodes) if !nodes.is_empty() => nodes,
                _ => return false,
            },
            None => return false,
        };

        self.context.clear(Section::Conversation);
        for node in nodes {
            self.context.push(Section::Conversation, node);
        }
        self.compact();
        self.last_prompt_tokens = self.context.tokens() as u32;
        true
    }

    pub fn swap_client(&mut self, new_client: ApiClient) {
        self.client = new_client;
    }

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

    pub fn conversation(&self) -> &[AstNode] {
        self.context.conversation()
    }

    pub fn client_clone(&self) -> ApiClient {
        self.client.clone()
    }
}