// context.rs — Context window as an AST
//
// The context window is a tree of AstNodes. Each node is either a leaf
// (typed content with cached token IDs) or a branch (role + children).
// The full prompt is a depth-first traversal of the sections in ContextState.
// Streaming responses are parsed into new nodes by the ResponseParser.
//
// Grammar (EBNF):
//
//   context         = section* ;
//   section         = (message | leaf)* ;
//   message         = IM_START role "\n" element* IM_END "\n" ;
//   role            = "system" | "user" | "assistant" ;
//   element         = thinking | tool_call | content ;
//   thinking        = "<think>" TEXT "</think>" ;
//   tool_call       = "<tool_call>\n" tool_xml "\n</tool_call>" ;
//   tool_xml        = "<function=" NAME ">\n" param* "</function>" ;
//   param           = "<parameter=" NAME ">\n" VALUE "\n</parameter>\n" ;
//   content         = TEXT ;
//
// Self-wrapping leaves (not inside a message branch):
//   dmn             = IM_START "dmn\n" TEXT IM_END "\n" ;
//   memory          = IM_START "memory\n" TEXT IM_END "\n" ;
//   tool_result     = IM_START "user\n<tool_response>\n" TEXT "\n</tool_response>" IM_END "\n" ;
//
// Non-visible leaves (not in prompt):
//   log             = TEXT ;
//
// Role is only for branch (interior) nodes. Leaf type is determined by
// the NodeBody variant. Grammar constraints enforced by construction.

use chrono::{DateTime, Utc};
use serde::{Serialize, Deserialize};
use super::tokenizer;

// ---------------------------------------------------------------------------
// Types
// ---------------------------------------------------------------------------

/// Branch roles — maps directly to the grammar's message roles.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
pub enum Role {
    System,
    User,
    Assistant,
}

/// Leaf content — each variant knows how to render itself.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum NodeBody {
    // Children of message branches — rendered without im_start/im_end
    Content(String),
    Thinking(String),
    ToolCall { name: String, arguments: String },

    // Self-wrapping leaves — render their own im_start/im_end
    ToolResult(String),
    Memory { key: String, text: String, score: Option<f64> },
    Dmn(String),

    // Non-visible (0 tokens in prompt)
    Log(String),
}

/// A leaf node: typed content with cached token IDs.
/// Token IDs are not serialized — they're recomputed on deserialization.
#[derive(Debug, Clone, Serialize)]
pub struct NodeLeaf {
    body: NodeBody,
    #[serde(skip)]
    token_ids: Vec<u32>,
    timestamp: Option<DateTime<Utc>>,
}

impl<'de> Deserialize<'de> for NodeLeaf {
    fn deserialize<D: serde::Deserializer<'de>>(deserializer: D) -> Result<Self, D::Error> {
        #[derive(Deserialize)]
        struct Raw {
            body: NodeBody,
            timestamp: Option<DateTime<Utc>>,
        }
        let raw = Raw::deserialize(deserializer)?;
        let token_ids = if raw.body.is_prompt_visible() {
            tokenizer::encode(&raw.body.render())
        } else {
            vec![]
        };
        Ok(NodeLeaf { body: raw.body, token_ids, timestamp: raw.timestamp })
    }
}

/// A node in the context AST.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum AstNode {
    Leaf(NodeLeaf),
    Branch { role: Role, children: Vec<AstNode> },
}

/// The context window: four sections as Vec<AstNode>.
/// All mutation goes through ContextState methods to maintain the invariant
/// that token_ids on every leaf matches its rendered text.
pub struct ContextState {
    system: Vec<AstNode>,
    identity: Vec<AstNode>,
    journal: Vec<AstNode>,
    conversation: Vec<AstNode>,
    pub conversation_log: Option<crate::mind::log::ConversationLog>,
}

impl Clone for ContextState {
    fn clone(&self) -> Self {
        Self {
            system: self.system.clone(),
            identity: self.identity.clone(),
            journal: self.journal.clone(),
            conversation: self.conversation.clone(),
            conversation_log: None, // forked contexts don't log
        }
    }
}

/// Identifies a section for mutation methods.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum Section {
    System,
    Identity,
    Journal,
    Conversation,
}

/// Ephemeral handle for dispatching a tool call. Not persisted in the AST.
#[derive(Debug, Clone)]
pub struct PendingToolCall {
    pub name: String,
    pub arguments: String,
    pub id: String,
}

pub trait Ast {
    fn render(&self) -> String;
    fn token_ids(&self) -> Vec<u32>;
    fn tokens(&self) -> usize;
}

pub struct ResponseParser {
    branch_idx: usize,
    call_counter: u32,
    buf: String,
    content_parts: Vec<String>,
    in_think: bool,
    think_buf: String,
    in_tool_call: bool,
    tool_call_buf: String,
}

impl Role {
    pub fn as_str(&self) -> &'static str {
        match self {
            Self::System    => "system",
            Self::User      => "user",
            Self::Assistant => "assistant",
        }
    }
}

impl NodeBody {
    /// Render this leaf body to text for the prompt.
    fn render_into(&self, out: &mut String) {
        match self {
            Self::Content(text)   => out.push_str(text),
            Self::Thinking(_)     => {},
            Self::Log(_)          => {},
            Self::ToolCall { name, arguments } => {
                out.push_str("<tool_call>\n");
                out.push_str(&format_tool_call_xml(name, arguments));
                out.push_str("\n</tool_call>\n");
            }
            Self::ToolResult(text) => {
                out.push_str("<|im_start|>user\n<tool_response>\n");
                out.push_str(text);
                out.push_str("\n</tool_response><|im_end|>\n");
            }
            Self::Memory { text, .. } => {
                out.push_str("<|im_start|>memory\n");
                out.push_str(text);
                out.push_str("<|im_end|>\n");
            }
            Self::Dmn(text) => {
                out.push_str("<|im_start|>dmn\n");
                out.push_str(text);
                out.push_str("<|im_end|>\n");
            }
        }
    }

    /// Whether this leaf contributes tokens to the prompt.
    fn render(&self) -> String {
        let mut s = String::new();
        self.render_into(&mut s);
        s
    }

    fn is_prompt_visible(&self) -> bool {
        !matches!(self, Self::Thinking(_) | Self::Log(_))
    }

    /// The text content of this leaf (for display, not rendering).
    pub fn text(&self) -> &str {
        match self {
            Self::Content(t) | Self::Thinking(t) | Self::Log(t)
                | Self::ToolResult(t) | Self::Dmn(t) => t,
            Self::ToolCall { name, .. } => name,
            Self::Memory { text, .. } => text,
        }
    }
}

impl NodeLeaf {
    fn new(body: NodeBody) -> Self {
        let token_ids = if body.is_prompt_visible() {
            tokenizer::encode(&body.render())
        } else {
            vec![]
        };
        Self { body, token_ids, timestamp: None }
    }

    pub fn with_timestamp(mut self, ts: DateTime<Utc>) -> Self {
        self.timestamp = Some(ts);
        self
    }

    pub fn body(&self) -> &NodeBody      { &self.body }
    pub fn token_ids(&self) -> &[u32]    { &self.token_ids }
    pub fn tokens(&self) -> usize        { self.token_ids.len() }
    pub fn timestamp(&self) -> Option<DateTime<Utc>> { self.timestamp }
}

impl AstNode {
    // -- Leaf constructors ----------------------------------------------------

    pub fn content(text: impl Into<String>) -> Self {
        Self::Leaf(NodeLeaf::new(NodeBody::Content(text.into())))
    }

    pub fn thinking(text: impl Into<String>) -> Self {
        Self::Leaf(NodeLeaf::new(NodeBody::Thinking(text.into())))
    }

    pub fn tool_call(name: impl Into<String>, arguments: impl Into<String>) -> Self {
        Self::Leaf(NodeLeaf::new(NodeBody::ToolCall {
            name: name.into(),
            arguments: arguments.into(),
        }))
    }

    pub fn tool_result(text: impl Into<String>) -> Self {
        Self::Leaf(NodeLeaf::new(NodeBody::ToolResult(text.into())))
    }

    pub fn memory(key: impl Into<String>, text: impl Into<String>) -> Self {
        Self::Leaf(NodeLeaf::new(NodeBody::Memory {
            key: key.into(),
            text: text.into(),
            score: None,
        }))
    }

    pub fn dmn(text: impl Into<String>) -> Self {
        Self::Leaf(NodeLeaf::new(NodeBody::Dmn(text.into())))
    }

    pub fn log(text: impl Into<String>) -> Self {
        Self::Leaf(NodeLeaf::new(NodeBody::Log(text.into())))
    }

    // -- Branch constructors --------------------------------------------------

    pub fn branch(role: Role, children: Vec<AstNode>) -> Self {
        Self::Branch { role, children }
    }

    pub fn system_msg(text: impl Into<String>) -> Self {
        Self::Branch {
            role: Role::System,
            children: vec![Self::content(text)],
        }
    }

    pub fn user_msg(text: impl Into<String>) -> Self {
        Self::Branch {
            role: Role::User,
            children: vec![Self::content(text)],
        }
    }

    // -- Builder --------------------------------------------------------------

    pub fn with_timestamp(mut self, ts: DateTime<Utc>) -> Self {
        match &mut self {
            Self::Leaf(leaf) => leaf.timestamp = Some(ts),
            Self::Branch { .. } => {}
        }
        self
    }

    pub fn children(&self) -> &[AstNode] {
        match self {
            Self::Branch { children, .. } => children,
            Self::Leaf(_) => &[],
        }
    }

    pub fn leaf(&self) -> Option<&NodeLeaf> {
        match self {
            Self::Leaf(l) => Some(l),
            _ => None,
        }
    }

    /// Short label for the UI.
    pub fn label(&self) -> String {
        let cfg = crate::config::get();
        match self {
            Self::Branch { role, children } => {
                let preview = children.first()
                    .and_then(|c| c.leaf())
                    .map(|l| truncate_preview(l.body.text(), 60))
                    .unwrap_or_default();
                match role {
                    Role::System => "system".into(),
                    Role::User => format!("{}: {}", cfg.user_name, preview),
                    Role::Assistant => format!("{}: {}", cfg.assistant_name, preview),
                }
            }
            Self::Leaf(leaf) => match &leaf.body {
                NodeBody::Content(t) => truncate_preview(t, 60),
                NodeBody::Thinking(t) => format!("thinking: {}", truncate_preview(t, 60)),
                NodeBody::ToolCall { name, .. } => format!("tool_call: {}", name),
                NodeBody::ToolResult(_) => "tool_result".into(),
                NodeBody::Memory { key, score, .. } => match score {
                    Some(s) => format!("mem: {} score:{:.1}", key, s),
                    None => format!("mem: {}", key),
                },
                NodeBody::Dmn(_) => "dmn".into(),
                NodeBody::Log(t) => format!("log: {}", truncate_preview(t, 60)),
            },
        }
    }
}

impl AstNode {
    fn render_into(&self, out: &mut String) {
        match self {
            Self::Leaf(leaf) => leaf.body.render_into(out),
            Self::Branch { role, children } => {
                out.push_str(&format!("<|im_start|>{}\n", role.as_str()));
                for child in children {
                    child.render_into(out);
                }
                out.push_str("<|im_end|>\n");
            }
        }
    }

    fn token_ids_into(&self, out: &mut Vec<u32>) {
        match self {
            Self::Leaf(leaf) => out.extend_from_slice(&leaf.token_ids),
            Self::Branch { role, children } => {
                out.push(tokenizer::IM_START);
                out.extend(tokenizer::encode(&format!("{}\n", role.as_str())));
                for child in children {
                    child.token_ids_into(out);
                }
                out.push(tokenizer::IM_END);
                out.extend(tokenizer::encode("\n"));
            }
        }
    }
}

impl Ast for AstNode {
    fn render(&self) -> String {
        let mut s = String::new();
        self.render_into(&mut s);
        s
    }

    fn token_ids(&self) -> Vec<u32> {
        let mut ids = Vec::new();
        self.token_ids_into(&mut ids);
        ids
    }

    fn tokens(&self) -> usize {
        match self {
            Self::Leaf(leaf) => leaf.tokens(),
            Self::Branch { role, children } => {
                1 + tokenizer::encode(&format!("{}\n", role.as_str())).len()
                    + children.iter().map(|c| c.tokens()).sum::<usize>()
                    + 1 + tokenizer::encode("\n").len()
            }
        }
    }
}

fn truncate_preview(s: &str, max: usize) -> String {
    let preview: String = s.chars().take(max).collect();
    let preview = preview.replace('\n', " ");
    if s.len() > max { format!("{}...", preview) } else { preview }
}

fn format_tool_call_xml(name: &str, args_json: &str) -> String {
    let args: serde_json::Value = serde_json::from_str(args_json)
        .unwrap_or(serde_json::Value::Object(Default::default()));
    let mut xml = format!("<function={}>\n", name);
    if let Some(obj) = args.as_object() {
        for (key, value) in obj {
            let val_str = match value {
                serde_json::Value::String(s) => s.clone(),
                other => other.to_string(),
            };
            xml.push_str(&format!("<parameter={}>\n{}\n</parameter>\n", key, val_str));
        }
    }
    xml.push_str("</function>");
    xml
}

fn normalize_xml_tags(text: &str) -> String {
    let mut result = String::with_capacity(text.len());
    let mut chars = text.chars().peekable();
    while let Some(ch) = chars.next() {
        if ch == '<' {
            let mut tag = String::from('<');
            for inner in chars.by_ref() {
                if inner == '>' {
                    tag.push('>');
                    break;
                } else if inner.is_whitespace() {
                    // Skip whitespace inside tags
                } else {
                    tag.push(inner);
                }
            }
            result.push_str(&tag);
        } else {
            result.push(ch);
        }
    }
    result
}

fn parse_qwen_tag<'a>(s: &'a str, tag: &str) -> Option<(&'a str, &'a str, &'a str)> {
    let open = format!("<{}=", tag);
    let close = format!("</{}>", tag);

    let start = s.find(&open)? + open.len();
    let name_end = start + s[start..].find('>')?;
    let body_start = name_end + 1;
    let body_end = body_start + s[body_start..].find(&close)?;

    Some((
        s[start..name_end].trim(),
        s[body_start..body_end].trim(),
        &s[body_end + close.len()..],
    ))
}

fn parse_tool_call_body(body: &str) -> Option<(String, String)> {
    let normalized = normalize_xml_tags(body);
    let body = normalized.trim();
    parse_xml_tool_call(body)
        .or_else(|| parse_json_tool_call(body))
}

fn parse_xml_tool_call(body: &str) -> Option<(String, String)> {
    let (func_name, func_body, _) = parse_qwen_tag(body, "function")?;
    let mut args = serde_json::Map::new();
    let mut rest = func_body;
    while let Some((key, val, remainder)) = parse_qwen_tag(rest, "parameter") {
        let value = serde_json::from_str(val)
            .unwrap_or(serde_json::Value::String(val.to_string()));
        args.insert(key.to_string(), value);
        rest = remainder;
    }
    Some((func_name.to_string(), serde_json::to_string(&args).unwrap_or_default()))
}

fn parse_json_tool_call(body: &str) -> Option<(String, String)> {
    let v: serde_json::Value = serde_json::from_str(body).ok()?;
    let name = v["name"].as_str()?;
    let arguments = &v["arguments"];
    Some((name.to_string(), serde_json::to_string(arguments).unwrap_or_default()))
}

impl ResponseParser {
    pub fn new(branch_idx: usize) -> Self {
        Self {
            branch_idx,
            call_counter: 0,
            buf: String::new(),
            content_parts: Vec::new(),
            in_think: false,
            think_buf: String::new(),
            in_tool_call: false,
            tool_call_buf: String::new(),
        }
    }

    /// Consume a token stream, parse into the AST, yield tool calls.
    /// Spawns a background task. Returns a tool call receiver and a
    /// join handle that resolves to Ok(()) or the stream error.
    pub fn run(
        self,
        mut stream: tokio::sync::mpsc::UnboundedReceiver<super::api::StreamToken>,
        agent: std::sync::Arc<super::Agent>,
    ) -> (
        tokio::sync::mpsc::UnboundedReceiver<PendingToolCall>,
        tokio::task::JoinHandle<anyhow::Result<()>>,
    ) {
        let (tx, rx) = tokio::sync::mpsc::unbounded_channel();
        let handle = tokio::spawn(async move {
            let mut parser = self;
            let agent_name = agent.state.lock().await.provenance.clone();
            let log_path = format!("/tmp/poc-{}.log", agent_name);
            let mut log_file = std::fs::OpenOptions::new()
                .create(true).append(true).open(&log_path).ok();
            let mut full_text = String::new();
            while let Some(event) = stream.recv().await {
                match event {
                    super::api::StreamToken::Token { text, id } => {
                        full_text.push_str(&text);
                        let mut ctx = agent.context.lock().await;
                        let calls = parser.feed_token(&text, id, &mut ctx);
                        if !calls.is_empty() {
                            if let Some(ref mut f) = log_file {
                                use std::io::Write;
                                for c in &calls {
                                    let end = c.arguments.floor_char_boundary(c.arguments.len().min(200));
                                    let _ = writeln!(f, "tool_call: {} args={}", c.name, &c.arguments[..end]);
                                }
                            }
                        }
                        for call in calls {
                            let _ = tx.send(call);
                        }
                    }
                    super::api::StreamToken::Done { usage } => {
                        if let Some(ref mut f) = log_file {
                            use std::io::Write;
                            let tc_count = full_text.matches("<tool_call>").count();
                            let ctx_tokens = agent.context.lock().await.tokens();
                            let _ = writeln!(f, "done: {} chars, {} <tool_call> tags, ctx: {} tokens",
                                full_text.len(), tc_count, ctx_tokens);
                            if tc_count == 0 && full_text.len() > 0 {
                                let end = full_text.floor_char_boundary(full_text.len().min(2000));
                                let _ = writeln!(f, "full text:\n{}", &full_text[..end]);
                            }
                            for (i, part) in full_text.split("<tool_call>").enumerate() {
                                if i > 0 {
                                    let end = part.floor_char_boundary(part.len().min(200));
                                    let _ = writeln!(f, "tool_call body: {}...", &part[..end]);
                                }
                            }
                        }
                        if let Some(u) = usage {
                            agent.state.lock().await.last_prompt_tokens = u.prompt_tokens;
                        }
                        let mut ctx = agent.context.lock().await;
                        parser.finish(&mut ctx);
                        return Ok(());
                    }
                    super::api::StreamToken::Error(e) => {
                        return Err(anyhow::anyhow!("{}", e));
                    }
                }
            }
            Ok(())
        });
        (rx, handle)
    }

    pub fn feed_token(&mut self, text: &str, _token_id: u32, ctx: &mut ContextState) -> Vec<PendingToolCall> {
        let mut pending = Vec::new();
        self.buf.push_str(text);

        loop {
            if self.in_think {
                match self.buf.find("</think>") {
                    Some(end) => {
                        self.think_buf.push_str(&self.buf[..end]);
                        self.buf = self.buf[end + 8..].to_string();
                        self.in_think = false;
                        let text = std::mem::take(&mut self.think_buf).trim().to_string();
                        if !text.is_empty() {
                            self.push_child(ctx, AstNode::thinking(text));
                        }
                        continue;
                    }
                    None => {
                        let safe = self.buf.len().saturating_sub(8);
                        if safe > 0 {
                            let safe = self.buf.floor_char_boundary(safe);
                            self.think_buf.push_str(&self.buf[..safe]);
                            self.buf = self.buf[safe..].to_string();
                        }
                        break;
                    }
                }
            }

            if self.in_tool_call {
                match self.buf.find("</tool_call>") {
                    Some(end) => {
                        self.tool_call_buf.push_str(&self.buf[..end]);
                        self.buf = self.buf[end + 12..].to_string();
                        self.in_tool_call = false;
                        if let Some((name, args)) = parse_tool_call_body(&self.tool_call_buf) {
                            self.flush_content(ctx);
                            self.push_child(ctx, AstNode::tool_call(&name, &args));
                            self.call_counter += 1;
                            pending.push(PendingToolCall {
                                name,
                                arguments: args,
                                id: format!("call_{}", self.call_counter),
                            });
                        }
                        self.tool_call_buf.clear();
                        continue;
                    }
                    None => {
                        let safe = self.buf.len().saturating_sub(12);
                        if safe > 0 {
                            let safe = self.buf.floor_char_boundary(safe);
                            self.tool_call_buf.push_str(&self.buf[..safe]);
                            self.buf = self.buf[safe..].to_string();
                        }
                        break;
                    }
                }
            }

            let think_pos = self.buf.find("<think>");
            let tool_pos = self.buf.find("<tool_call>");
            let next_tag = match (think_pos, tool_pos) {
                (Some(a), Some(b)) => Some(a.min(b)),
                (Some(a), None) => Some(a),
                (None, Some(b)) => Some(b),
                (None, None) => None,
            };

            match next_tag {
                Some(pos) => {
                    if pos > 0 {
                        self.content_parts.push(self.buf[..pos].to_string());
                    }
                    if self.buf[pos..].starts_with("<think>") {
                        self.buf = self.buf[pos + 7..].to_string();
                        self.flush_content(ctx);
                        self.in_think = true;
                    } else {
                        self.buf = self.buf[pos + 11..].to_string();
                        self.flush_content(ctx);
                        self.in_tool_call = true;
                    }
                    continue;
                }
                None => {
                    let safe = self.buf.len().saturating_sub(11);
                    if safe > 0 {
                        let safe = self.buf.floor_char_boundary(safe);
                        self.content_parts.push(self.buf[..safe].to_string());
                        self.buf = self.buf[safe..].to_string();
                    }
                    break;
                }
            }
        }

        pending
    }

    fn push_child(&self, ctx: &mut ContextState, child: AstNode) {
        ctx.push_child(Section::Conversation, self.branch_idx, child);
    }

    fn flush_content(&mut self, ctx: &mut ContextState) {
        if !self.content_parts.is_empty() {
            let text: String = self.content_parts.drain(..).collect();
            let text = text.trim().to_string();
            if !text.is_empty() {
                self.push_child(ctx, AstNode::content(text));
            }
        }
    }

    pub fn finish(mut self, ctx: &mut ContextState) {
        if !self.buf.is_empty() {
            self.content_parts.push(std::mem::take(&mut self.buf));
        }
        self.flush_content(ctx);
    }
}

impl ContextState {
    pub fn new() -> Self {
        Self {
            system: Vec::new(),
            identity: Vec::new(),
            journal: Vec::new(),
            conversation: Vec::new(),
            conversation_log: None,
        }
    }

    // -- Read access ----------------------------------------------------------

    pub fn system(&self) -> &[AstNode]       { &self.system }
    pub fn identity(&self) -> &[AstNode]     { &self.identity }
    pub fn journal(&self) -> &[AstNode]      { &self.journal }
    pub fn conversation(&self) -> &[AstNode] { &self.conversation }

    fn sections(&self) -> [&Vec<AstNode>; 4] {
        [&self.system, &self.identity, &self.journal, &self.conversation]
    }
}

impl Ast for ContextState {
    fn render(&self) -> String {
        let mut s = String::new();
        for section in self.sections() {
            for node in section {
                s.push_str(&node.render());
            }
        }
        s
    }

    fn token_ids(&self) -> Vec<u32> {
        let mut ids = Vec::new();
        for section in self.sections() {
            for node in section {
                ids.extend(node.token_ids());
            }
        }
        ids
    }

    fn tokens(&self) -> usize {
        self.sections().iter()
            .flat_map(|s| s.iter())
            .map(|n| n.tokens())
            .sum()
    }
}

impl ContextState {
    fn section_mut(&mut self, section: Section) -> &mut Vec<AstNode> {
        match section {
            Section::System       => &mut self.system,
            Section::Identity     => &mut self.identity,
            Section::Journal      => &mut self.journal,
            Section::Conversation => &mut self.conversation,
        }
    }

    pub fn push(&mut self, section: Section, node: AstNode) {
        if section == Section::Conversation {
            if let Some(ref log) = self.conversation_log {
                if let Err(e) = log.append_node(&node) {
                    eprintln!("warning: log: {:#}", e);
                }
            }
        }
        self.section_mut(section).push(node);
    }

    /// Replace the body of a leaf at `index` in `section`.
    /// Re-tokenizes to maintain the invariant.
    pub fn set_message(&mut self, section: Section, index: usize, body: NodeBody) {
        let nodes = self.section_mut(section);
        let node = &mut nodes[index];
        match node {
            AstNode::Leaf(leaf) => {
                let token_ids = if body.is_prompt_visible() {
                    tokenizer::encode(&body.render())
                } else {
                    vec![]
                };
                leaf.body = body;
                leaf.token_ids = token_ids;
            }
            AstNode::Branch { .. } => panic!("set_message on branch node"),
        }
    }

    /// Set the memory score on a Memory leaf at `index` in `section`.
    pub fn set_score(&mut self, section: Section, index: usize, score: Option<f64>) {
        let node = &mut self.section_mut(section)[index];
        match node {
            AstNode::Leaf(leaf) => match &mut leaf.body {
                NodeBody::Memory { score: s, .. } => *s = score,
                _ => panic!("set_score on non-memory node"),
            },
            _ => panic!("set_score on branch node"),
        }
    }

    pub fn del(&mut self, section: Section, index: usize) -> AstNode {
        self.section_mut(section).remove(index)
    }

    pub fn clear(&mut self, section: Section) {
        self.section_mut(section).clear();
    }

    /// Dedup and trim conversation entries to fit within the context budget.
    ///
    /// Phase 1: Drop duplicate memories (keep last) and DMN entries.
    /// Phase 2: While over budget, drop lowest-scored memory (if memories
    ///          are > 50% of conversation tokens) or oldest conversation entry.
    /// Phase 3: Snap to user message boundary at start.
    pub fn trim_conversation(&mut self) {
        let max_tokens = context_budget_tokens();
        let fixed = self.system.iter().map(|n| n.tokens()).sum::<usize>()
            + self.identity.iter().map(|n| n.tokens()).sum::<usize>()
            + self.journal.iter().map(|n| n.tokens()).sum::<usize>();

        // Phase 1: dedup memories by key (keep last), drop DMN
        let mut seen_keys: std::collections::HashMap<String, usize> = std::collections::HashMap::new();
        let mut drop = std::collections::HashSet::new();

        for (i, node) in self.conversation.iter().enumerate() {
            if let AstNode::Leaf(leaf) = node {
                match leaf.body() {
                    NodeBody::Dmn(_) => { drop.insert(i); }
                    NodeBody::Memory { key, .. } => {
                        if let Some(prev) = seen_keys.insert(key.clone(), i) {
                            drop.insert(prev);
                        }
                    }
                    _ => {}
                }
            }
        }

        if !drop.is_empty() {
            let mut i = 0;
            self.conversation.retain(|_| { let keep = !drop.contains(&i); i += 1; keep });
        }

        // Phase 2: while over budget, evict
        loop {
            let total: usize = self.conversation.iter().map(|n| n.tokens()).sum();
            if fixed + total <= max_tokens { break; }
            let mt: usize = self.conversation.iter()
                .filter(|n| matches!(n, AstNode::Leaf(l) if matches!(l.body(), NodeBody::Memory { .. })))
                .map(|n| n.tokens()).sum();
            let ct = total - mt;

            if mt > ct {
                // Memories > 50% — drop lowest-scored
                if let Some(i) = self.lowest_scored_memory() {
                    self.conversation.remove(i);
                    continue;
                }
            }
            // Drop oldest non-memory entry
            if let Some(i) = self.conversation.iter().position(|n|
                !matches!(n, AstNode::Leaf(l) if matches!(l.body(), NodeBody::Memory { .. })))
            {
                self.conversation.remove(i);
            } else {
                break;
            }
        }

        // Phase 3: snap to user message boundary
        while let Some(first) = self.conversation.first() {
            if matches!(first, AstNode::Branch { role: Role::User, .. }) { break; }
            self.conversation.remove(0);
        }
    }

    fn lowest_scored_memory(&self) -> Option<usize> {
        self.conversation.iter().enumerate()
            .filter_map(|(i, n)| {
                if let AstNode::Leaf(l) = n {
                    if let NodeBody::Memory { score: Some(s), .. } = l.body() {
                        return Some((i, *s));
                    }
                }
                None
            })
            .min_by(|(_, a), (_, b)| a.partial_cmp(b).unwrap_or(std::cmp::Ordering::Equal))
            .map(|(i, _)| i)
    }

    /// Push a child node into a branch at `index` in `section`.
    pub fn push_child(&mut self, section: Section, index: usize, child: AstNode) {
        let node = &mut self.section_mut(section)[index];
        match node {
            AstNode::Branch { children, .. } => children.push(child),
            AstNode::Leaf(_) => panic!("push_child on leaf node"),
        }
    }

    /// Number of nodes in a section.
    pub fn len(&self, section: Section) -> usize {
        match section {
            Section::System       => self.system.len(),
            Section::Identity     => self.identity.len(),
            Section::Journal      => self.journal.len(),
            Section::Conversation => self.conversation.len(),
        }
    }
}

pub fn context_window() -> usize {
    crate::config::get().api_context_window
}

pub fn context_budget_tokens() -> usize {
    context_window() * 80 / 100
}

pub fn is_context_overflow(err: &anyhow::Error) -> bool {
    let msg = err.to_string().to_lowercase();
    msg.contains("context length")
        || msg.contains("token limit")
        || msg.contains("too many tokens")
        || msg.contains("maximum context")
        || msg.contains("prompt is too long")
        || msg.contains("request too large")
        || msg.contains("input validation error")
        || msg.contains("content length limit")
        || (msg.contains("400") && msg.contains("tokens"))
}

pub fn is_stream_error(err: &anyhow::Error) -> bool {
    err.to_string().contains("model stream error")
}

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

    // -- Helpers for inspecting parse results ----------------------------------

    fn bodies(nodes: &[AstNode]) -> Vec<&NodeBody> {
        nodes.iter().filter_map(|c| c.leaf()).map(|l| l.body()).collect()
    }

    fn assert_content(body: &NodeBody, expected: &str) {
        match body {
            NodeBody::Content(t) => assert_eq!(t, expected),
            other => panic!("expected Content, got {:?}", other),
        }
    }

    fn assert_thinking(body: &NodeBody, expected: &str) {
        match body {
            NodeBody::Thinking(t) => assert_eq!(t, expected),
            other => panic!("expected Thinking, got {:?}", other),
        }
    }

    fn assert_tool_call<'a>(body: &'a NodeBody, expected_name: &str) -> &'a str {
        match body {
            NodeBody::ToolCall { name, arguments } => {
                assert_eq!(name, expected_name);
                arguments
            }
            other => panic!("expected ToolCall, got {:?}", other),
        }
    }

    // -- XML parsing tests ----------------------------------------------------

    #[test]
    fn test_tool_call_xml_parse_clean() {
        let body = "<function=bash>\n<parameter=command>poc-memory used core-personality</parameter>\n</function>";
        let (name, args) = parse_tool_call_body(body).unwrap();
        assert_eq!(name, "bash");
        let args: serde_json::Value = serde_json::from_str(&args).unwrap();
        assert_eq!(args["command"], "poc-memory used core-personality");
    }

    #[test]
    fn test_tool_call_xml_parse_streamed_whitespace() {
        let body = "<\nfunction\n=\nbash\n>\n<\nparameter\n=\ncommand\n>pwd</\nparameter\n>\n</\nfunction\n>";
        let (name, args) = parse_tool_call_body(body).unwrap();
        assert_eq!(name, "bash");
        let args: serde_json::Value = serde_json::from_str(&args).unwrap();
        assert_eq!(args["command"], "pwd");
    }

    #[test]
    fn test_tool_call_json_parse() {
        let body = r#"{"name": "bash", "arguments": {"command": "ls"}}"#;
        let (name, args) = parse_tool_call_body(body).unwrap();
        assert_eq!(name, "bash");
        let args: serde_json::Value = serde_json::from_str(&args).unwrap();
        assert_eq!(args["command"], "ls");
    }

    #[test]
    fn test_normalize_preserves_content() {
        let text = "<function=bash>\n<parameter=command>echo hello world</parameter>\n</function>";
        let normalized = normalize_xml_tags(text);
        assert_eq!(normalized, text);
    }

    #[test]
    fn test_normalize_strips_tag_internal_whitespace() {
        assert_eq!(normalize_xml_tags("<\nfunction\n=\nbash\n>"), "<function=bash>");
    }

    // -- ResponseParser tests -------------------------------------------------

    /// Set up a ContextState with an assistant branch, run the parser,
    /// return the children that were pushed into the branch.
    fn parse_into_ctx(chunks: &[&str]) -> (ContextState, Vec<PendingToolCall>) {
        let mut ctx = ContextState::new();
        ctx.push(Section::Conversation, AstNode::branch(Role::Assistant, vec![]));
        let mut p = ResponseParser::new(0);
        let mut calls = Vec::new();
        for chunk in chunks {
            // Feed each chunk as a single token (id=0 for tests)
            calls.extend(p.feed_token(chunk, 0, &mut ctx));
        }
        p.finish(&mut ctx);
        (ctx, calls)
    }

    fn assistant_children(ctx: &ContextState) -> &[AstNode] {
        ctx.conversation()[0].children()
    }

    #[test]
    fn test_parser_plain_text() {
        let (ctx, _) = parse_into_ctx(&["hello world"]);
        let b = bodies(assistant_children(&ctx));
        assert_eq!(b.len(), 1);
        assert_content(b[0], "hello world");
    }

    #[test]
    fn test_parser_thinking_then_content() {
        let (ctx, _) = parse_into_ctx(&["<think>reasoning</think>answer"]);
        let b = bodies(assistant_children(&ctx));
        assert_eq!(b.len(), 2);
        assert_thinking(b[0], "reasoning");
        assert_content(b[1], "answer");
    }

    #[test]
    fn test_parser_tool_call() {
        let (ctx, calls) = parse_into_ctx(&[
            "<tool_call>\n<function=bash>\n<parameter=command>ls</parameter>\n</function>\n</tool_call>"
        ]);
        assert_eq!(calls.len(), 1);
        assert_eq!(calls[0].name, "bash");
        let b = bodies(assistant_children(&ctx));
        assert_eq!(b.len(), 1);
        let args = assert_tool_call(b[0], "bash");
        let args: serde_json::Value = serde_json::from_str(args).unwrap();
        assert_eq!(args["command"], "ls");
    }

    #[test]
    fn test_parser_content_then_tool_call_then_content() {
        let (ctx, _) = parse_into_ctx(&[
            "before",
            "<tool_call>\n<function=bash>\n<parameter=command>pwd</parameter>\n</function>\n</tool_call>",
            "after",
        ]);
        let b = bodies(assistant_children(&ctx));
        assert_eq!(b.len(), 3);
        assert_content(b[0], "before");
        assert_tool_call(b[1], "bash");
        assert_content(b[2], "after");
    }

    #[test]
    fn test_parser_incremental_feed() {
        let text = "<think>thought</think>response";
        let mut ctx = ContextState::new();
        ctx.push(Section::Conversation, AstNode::branch(Role::Assistant, vec![]));
        let mut p = ResponseParser::new(0);
        for ch in text.chars() {
            p.feed_token(&ch.to_string(), 0, &mut ctx);
        }
        p.finish(&mut ctx);
        let b = bodies(assistant_children(&ctx));
        assert_eq!(b.len(), 2);
        assert_thinking(b[0], "thought");
        assert_content(b[1], "response");
    }

    #[test]
    fn test_parser_incremental_tool_call() {
        let text = "text<tool_call>\n<function=bash>\n<parameter=command>ls</parameter>\n</function>\n</tool_call>more";
        let mut ctx = ContextState::new();
        ctx.push(Section::Conversation, AstNode::branch(Role::Assistant, vec![]));
        let mut p = ResponseParser::new(0);
        let mut tool_calls = 0;
        for ch in text.chars() {
            tool_calls += p.feed_token(&ch.to_string(), 0, &mut ctx).len();
        }
        p.finish(&mut ctx);
        assert_eq!(tool_calls, 1);
        let b = bodies(assistant_children(&ctx));
        assert_eq!(b.len(), 3);
        assert_content(b[0], "text");
        assert_tool_call(b[1], "bash");
        assert_content(b[2], "more");
    }

    #[test]
    fn test_parser_thinking_tool_call_content() {
        let (ctx, _) = parse_into_ctx(&[
            "<think>let me think</think>",
            "<tool_call>\n<function=read>\n<parameter=path>/etc/hosts</parameter>\n</function>\n</tool_call>",
            "here's what I found",
        ]);
        let b = bodies(assistant_children(&ctx));
        assert_eq!(b.len(), 3);
        assert_thinking(b[0], "let me think");
        assert_tool_call(b[1], "read");
        assert_content(b[2], "here's what I found");
    }

    // -- Round-trip rendering tests -------------------------------------------

    #[test]
    fn test_render_system_msg() {
        let node = AstNode::system_msg("you are helpful");
        assert_eq!(node.render(), "<|im_start|>system\nyou are helpful<|im_end|>\n");
    }

    #[test]
    fn test_render_user_msg() {
        let node = AstNode::user_msg("hello");
        assert_eq!(node.render(), "<|im_start|>user\nhello<|im_end|>\n");
    }

    #[test]
    fn test_render_assistant_with_thinking_and_content() {
        let node = AstNode::branch(Role::Assistant, vec![
            AstNode::thinking("hmm"),
            AstNode::content("answer"),
        ]);
        // Thinking renders as empty, content renders as-is
        assert_eq!(node.render(), "<|im_start|>assistant\nanswer<|im_end|>\n");
    }

    #[test]
    fn test_render_tool_result() {
        let node = AstNode::tool_result("output here");
        assert_eq!(node.render(), "<|im_start|>user\n<tool_response>\noutput here\n</tool_response><|im_end|>\n");
    }

    #[test]
    fn test_render_memory() {
        let node = AstNode::memory("identity", "I am Proof of Concept");
        assert_eq!(node.render(), "<|im_start|>memory\nI am Proof of Concept<|im_end|>\n");
    }

    #[test]
    fn test_render_dmn() {
        let node = AstNode::dmn("subconscious prompt");
        assert_eq!(node.render(), "<|im_start|>dmn\nsubconscious prompt<|im_end|>\n");
    }

    #[test]
    fn test_render_tool_call() {
        let node = AstNode::tool_call("bash", r#"{"command":"ls"}"#);
        let rendered = node.render();
        assert!(rendered.contains("<tool_call>"));
        assert!(rendered.contains("<function=bash>"));
        assert!(rendered.contains("<parameter=command>"));
        assert!(rendered.contains("ls"));
        assert!(rendered.contains("</tool_call>"));
    }

    // -- Tokenizer round-trip tests -------------------------------------------
    // These require the tokenizer file; skipped if not present.

    fn init_tokenizer() -> bool {
        let path = format!("{}/.consciousness/tokenizer-qwen35.json",
            std::env::var("HOME").unwrap_or_default());
        if std::path::Path::new(&path).exists() {
            tokenizer::init(&path);
            true
        } else {
            false
        }
    }

    fn assert_token_invariants(node: &AstNode) {
        assert_eq!(node.tokens(), node.token_ids().len(),
            "tokens() != token_ids().len()");
    }

    #[test]
    fn test_tokenize_roundtrip_leaf_types() {
        if !init_tokenizer() { return; }

        assert_token_invariants(&AstNode::system_msg("you are a helpful assistant"));
        assert_token_invariants(&AstNode::user_msg("what is 2+2?"));
        assert_token_invariants(&AstNode::tool_result("4"));
        assert_token_invariants(&AstNode::memory("identity", "I am Proof of Concept"));
        assert_token_invariants(&AstNode::dmn("check the memory store"));
        assert_token_invariants(&AstNode::tool_call("bash", r#"{"command":"ls -la"}"#));
    }

    #[test]
    fn test_tokenize_roundtrip_assistant_branch() {
        if !init_tokenizer() { return; }

        let node = AstNode::branch(Role::Assistant, vec![
            AstNode::content("here's what I found:\n"),
            AstNode::tool_call("bash", r#"{"command":"pwd"}"#),
            AstNode::content("\nthat's the current directory"),
        ]);
        assert_token_invariants(&node);
    }

    #[test]
    fn test_tokenize_invisible_nodes_are_zero() {
        if !init_tokenizer() { return; }

        assert_eq!(AstNode::thinking("deep thoughts").tokens(), 0);
        assert_eq!(AstNode::log("debug info").tokens(), 0);
    }

    #[test]
    fn test_tokenize_decode_roundtrip() {
        if !init_tokenizer() { return; }

        // Content without special tokens round-trips through decode
        let text = "hello world, this is a test";
        let ids = tokenizer::encode(text);
        let decoded = tokenizer::decode(&ids);
        assert_eq!(decoded, text);
    }

    #[test]
    fn test_tokenize_context_state_matches_concatenation() {
        if !init_tokenizer() { return; }

        let mut ctx = ContextState::new();
        ctx.push(Section::System, AstNode::system_msg("you are helpful"));
        ctx.push(Section::Identity, AstNode::memory("name", "Proof of Concept"));
        ctx.push(Section::Conversation, AstNode::user_msg("hi"));

        assert_eq!(ctx.tokens(), ctx.token_ids().len());
    }

    #[test]
    fn test_parser_roundtrip_through_tokenizer() {
        if !init_tokenizer() { return; }

        let (ctx, _) = parse_into_ctx(&[
            "I'll check that for you",
            "<tool_call>\n<function=bash>\n<parameter=command>ls</parameter>\n</function>\n</tool_call>",
        ]);
        let node = &ctx.conversation()[0];
        assert_token_invariants(node);
        assert!(node.tokens() > 0);
    }
}