//! ContextSlot —— 多上下文槽位管理。
//!
//! 设计要点（参见 `docs/17-phase10-contextslot.md`）：
//!
//! - **多上下文分区**：单个 session 内可创建/切换/派生多个独立消息上下文
//! - **三种模式**：Full（完整历史）/ Focused（读时过滤）/ Readonly（禁止写入）
//! - **三种来源**：New（全新）/ Derived（派生）/ Static（静态）
//! - **基于 MemoryStore trait 持久化**：JSON blob 批次存储，每 slot 3-4 条 MemoryItem 记录
//! - **零新依赖方向**：放在 `agent/` 下利用已有的 `agent → memory` 依赖

use serde::{Deserialize, Serialize};
use time::OffsetDateTime;

use crate::agent::error::AgentError;
use crate::llm::types::message::Message;
use crate::memory::store::MemoryStore;
use crate::memory::types::{MemoryFilter, MemoryItem};

/// 上下文槽 —— 一段带策略配置的消息列表。
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ContextSlot {
    /// 当前 slot 的唯一标识（同一个 session_id 内唯一）。
    pub id: String,
    /// 所属 session。
    pub session_id: String,
    /// 槽配置。
    pub config: SlotConfig,
    /// 消息列表（全量，Focused/Readonly 在读取时做策略过滤）。
    pub messages: Vec<Message>,
    /// 槽元数据。
    pub meta: SlotMeta,
}

/// 槽配置。
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct SlotConfig {
    /// 槽模式（Full / Focused / Readonly）。
    pub mode: SlotMode,
    /// 槽来源（New / Derived / Static）。
    pub source: SlotSource,
    /// 上下文预算（v0.2 纯数据结构，无消费逻辑）。
    pub budget: ContextBudget,
    /// 是否启用自动压缩（v0.2 保留字段，LlmCycle 内部自行判断）。
    pub compact: bool,
}

impl Default for SlotConfig {
    fn default() -> Self {
        Self {
            mode: SlotMode::Full,
            source: SlotSource::New,
            budget: ContextBudget::default(),
            compact: true,
        }
    }
}

/// 槽模式。
#[derive(Debug, Clone, Serialize, Deserialize)]
#[non_exhaustive]
pub enum SlotMode {
    /// 完整对话历史（全部消息）。
    Full,
    /// 聚焦模式 —— 读取时按策略过滤，保持 LLM 注意力。
    Focused(FocusedConfig),
    /// 只读参考上下文 —— 禁止写入。
    Readonly,
}

/// 聚焦模式配置。
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct FocusedConfig {
    /// 是否保留 system prompt。
    pub keep_system: bool,
    /// 保留的最近消息条数（以消息条数而非对话轮次为单位，因为一轮对话可能包含多条 tool 消息）。
    pub recent_messages: usize,
    /// 摘要覆盖（消费端：手动或自动生成的摘要会注入到消息列表末尾）。
    /// v0.3 Phase 16 起，`AgentBuilder::summary_config(cfg)` 内联检查点会
    /// 自动调用 LLM 生成摘要并写入此字段，详见 `docs/22-phase16-summary-auto-generation.md`。
    pub summary_override: Option<String>,
}

/// 槽来源。
#[derive(Debug, Clone, Serialize, Deserialize)]
#[non_exhaustive]
pub enum SlotSource {
    /// 全新空槽。
    New,
    /// 从父 slot 派生（记录 parent_id）。
    Derived {
        parent_id: String,
        strategy: DeriveStrategy,
    },
    /// 预置静态消息（不持久化，随 session 生命周期存在）。
    Static(Vec<Message>),
}

/// 派生策略。
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum DeriveStrategy {
    /// 完整复制父 slot 的消息。
    Full,
    /// 按聚焦策略复制父 slot 的消息。
    Focused(FocusedConfig),
}

/// 合并策略 —— Phase 13 新增，控制 `ContextSlot::merge` 如何将子 slot 消息合入父 slot。
///
/// `#[non_exhaustive]` 预留未来扩展（如 `Summarize` 变体）。
#[derive(Debug, Clone, Serialize, Deserialize)]
#[non_exhaustive]
pub enum MergeStrategy {
    /// 子 slot 消息追加到父 slot 末尾。
    Append,
    /// 用子 slot 消息替换父 slot 内容。
    Replace,
}

/// 上下文预算（v0.2 纯数据结构，无消费逻辑）。
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ContextBudget {
    /// system prompt 预算。
    pub system: u32,
    /// 对话历史预算。
    pub history: u32,
    /// 工具定义预算。
    pub tools: u32,
    /// 工具结果预算。
    pub tool_results: u32,
    /// 预留 buffer。
    pub reserve: u32,
}

impl Default for ContextBudget {
    fn default() -> Self {
        Self {
            system: 8_000,
            history: 80_000,
            tools: 10_000,
            tool_results: 20_000,
            reserve: 10_000,
        }
    }
}

impl ContextBudget {
    /// 自动分配：按上下文窗口的固定比例分配预算。
    /// v0.2 只做占位实现，v0.3 将根据实际 provider 的 context_window 计算。
    pub fn auto() -> Self {
        Self::default()
    }
}

/// 槽元数据。
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct SlotMeta {
    /// 父 slot id（仅 Derived 来源有值）。
    pub parent_id: Option<String>,
    /// 消息总数。
    pub message_count: usize,
    /// 总 token 估算值（由 add_messages 时累计，v0.2 为近似值）。
    pub total_tokens: u32,
    /// 创建时间（Unix 时间戳，秒）。
    pub created_at: u64,
}

impl SlotMeta {
    pub fn new() -> Self {
        Self {
            parent_id: None,
            message_count: 0,
            total_tokens: 0,
            created_at: std::time::SystemTime::now()
                .duration_since(std::time::SystemTime::UNIX_EPOCH)
                .map(|d| d.as_secs())
                .unwrap_or(0),
        }
    }
}

impl Default for SlotMeta {
    fn default() -> Self {
        Self::new()
    }
}

impl ContextSlot {
    /// 持久化 key 前缀。
    const KEY_DATA: &'static str = "slot_data";
    const KEY_META: &'static str = "slot_meta";
    const KEY_CONFIG: &'static str = "slot_config";
    const KEY_REL: &'static str = "slot_rel";

    /// 校验 id 不含冒号（避免破坏 key 格式与 list prefix 过滤）。
    /// 失败时 panic —— 这是开发者错误而非用户错误。
    fn assert_no_colon(id: &str, field: &str) {
        if id.contains(':') {
            panic!(
                "{field} '{id}' contains ':' which would break key format. \
                 Use only letters, digits, hyphens and underscores."
            );
        }
    }

    pub(crate) fn data_key(session_id: &str, slot_id: &str) -> String {
        Self::assert_no_colon(session_id, "session_id");
        Self::assert_no_colon(slot_id, "slot_id");
        format!("{}:{}:{}", Self::KEY_DATA, session_id, slot_id)
    }
    pub(crate) fn meta_key(session_id: &str, slot_id: &str) -> String {
        Self::assert_no_colon(session_id, "session_id");
        Self::assert_no_colon(slot_id, "slot_id");
        format!("{}:{}:{}", Self::KEY_META, session_id, slot_id)
    }
    pub(crate) fn config_key(session_id: &str, slot_id: &str) -> String {
        Self::assert_no_colon(session_id, "session_id");
        Self::assert_no_colon(slot_id, "slot_id");
        format!("{}:{}:{}", Self::KEY_CONFIG, session_id, slot_id)
    }
    pub(crate) fn rel_key(session_id: &str, child_id: &str) -> String {
        Self::assert_no_colon(session_id, "session_id");
        Self::assert_no_colon(child_id, "child_id");
        format!("{}:{}:{}", Self::KEY_REL, session_id, child_id)
    }

    /// 构造 MemoryItem 的辅助函数。
    fn make_item(key: String, content: String) -> MemoryItem {
        MemoryItem {
            id: key,
            content,
            metadata: serde_json::json!({}),
            created_at: OffsetDateTime::now_utc(),
        }
    }

    /// 创建一个新的空 ContextSlot（不持久化，仅内存构造）。
    pub fn new(
        session_id: impl Into<String>,
        slot_id: impl Into<String>,
        config: SlotConfig,
    ) -> Self {
        Self {
            id: slot_id.into(),
            session_id: session_id.into(),
            config,
            messages: Vec::new(),
            meta: SlotMeta::new(),
        }
    }

    /// 保存 slot 数据到存储后端（全量写入，含 config）。
    pub async fn save(&self, store: &dyn MemoryStore) -> Result<(), AgentError> {
        let data = serde_json::to_string(&self.messages)
            .map_err(|e| AgentError::Other(e.to_string()))?;
        let meta = serde_json::to_string(&self.meta)
            .map_err(|e| AgentError::Other(e.to_string()))?;
        let config = serde_json::to_string(&self.config)
            .map_err(|e| AgentError::Other(e.to_string()))?;

        store
            .save(Self::make_item(
                Self::data_key(&self.session_id, &self.id),
                data,
            ))
            .await
            .map_err(AgentError::Memory)?;
        store
            .save(Self::make_item(
                Self::meta_key(&self.session_id, &self.id),
                meta,
            ))
            .await
            .map_err(AgentError::Memory)?;
        store
            .save(Self::make_item(
                Self::config_key(&self.session_id, &self.id),
                config,
            ))
            .await
            .map_err(AgentError::Memory)?;

        // 派生关系
        if let SlotSource::Derived { parent_id, .. } = &self.config.source {
            store
                .save(Self::make_item(
                    Self::rel_key(&self.session_id, &self.id),
                    parent_id.clone(),
                ))
                .await
                .map_err(AgentError::Memory)?;
        }

        Ok(())
    }

    /// 从存储加载 slot，config 从 `slot_config` key 自行恢复。
    /// 若 config 记录不存在（旧版本升级场景），使用 `SlotConfig::default()`。
    pub async fn load(
        id: &str,
        session_id: &str,
        store: &dyn MemoryStore,
    ) -> Result<Option<Self>, AgentError> {
        let meta_item = store
            .get(&Self::meta_key(session_id, id))
            .await
            .map_err(AgentError::Memory)?;
        let data_item = store
            .get(&Self::data_key(session_id, id))
            .await
            .map_err(AgentError::Memory)?;
        let config_item = store
            .get(&Self::config_key(session_id, id))
            .await
            .map_err(AgentError::Memory)?;

        match (meta_item, data_item) {
            (Some(m), Some(d)) => {
                let meta: SlotMeta = serde_json::from_str(&m.content)
                    .map_err(|e| AgentError::Other(e.to_string()))?;
                let messages: Vec<Message> = serde_json::from_str(&d.content)
                    .map_err(|e| AgentError::Other(e.to_string()))?;
                // config 从存储恢复；不存在则使用 default（兼容旧版本）
                let config = match config_item {
                    Some(c) => serde_json::from_str(&c.content)
                        .map_err(|e| AgentError::Other(e.to_string()))?,
                    None => SlotConfig::default(),
                };
                Ok(Some(Self {
                    id: id.to_string(),
                    session_id: session_id.to_string(),
                    config,
                    messages,
                    meta,
                }))
            }
            _ => Ok(None),
        }
    }

    /// 列出某 session 下的所有 slot 元数据。
    pub async fn list(
        session_id: &str,
        store: &dyn MemoryStore,
    ) -> Result<Vec<SlotMeta>, AgentError> {
        let prefix_str = format!("{}:{}:", Self::KEY_META, session_id);
        let filter = MemoryFilter {
            prefix: Some(prefix_str),
            ..Default::default()
        };
        let items = store.list(&filter).await.map_err(AgentError::Memory)?;
        let mut metas = Vec::new();
        for item in items {
            if let Ok(meta) = serde_json::from_str::<SlotMeta>(&item.content) {
                metas.push(meta);
            }
        }
        Ok(metas)
    }

    /// 删除 slot 的所有存储记录（slot_data + slot_meta + slot_config + slot_rel）。
    pub async fn delete(
        id: &str,
        session_id: &str,
        store: &dyn MemoryStore,
    ) -> Result<(), AgentError> {
        store
            .delete(&Self::data_key(session_id, id))
            .await
            .map_err(AgentError::Memory)?;
        store
            .delete(&Self::meta_key(session_id, id))
            .await
            .map_err(AgentError::Memory)?;
        store
            .delete(&Self::config_key(session_id, id))
            .await
            .map_err(AgentError::Memory)?;
        // slot_rel 是 best-effort（仅 Derived 来源的 slot 才有此 key）
        let _ = store.delete(&Self::rel_key(session_id, id)).await;
        Ok(())
    }

    /// 追加消息（Readonly 模式下返回 `SlotReadonly` 错误）。
    /// Full / Focused 模式下允许追加。
    pub fn append_messages(&mut self, new_messages: Vec<Message>) -> Result<(), AgentError> {
        if matches!(self.config.mode, SlotMode::Readonly) {
            return Err(AgentError::SlotReadonly(
                "Readonly slot does not allow writes".into(),
            ));
        }
        let count = new_messages.len();
        self.messages.extend(new_messages);
        self.meta.message_count += count;
        Ok(())
    }

    /// 按 FocusedConfig 过滤消息（静态辅助函数，被 `load_messages` 和 `derive_slot` 复用）。
    ///
    /// 过滤逻辑：
    /// 1. 保留第一条 system 消息（如果 `keep_system=true`）
    /// 2. 取最近 `recent_messages` 条非 system 消息（如果 `recent_messages > 0`）
    /// 3. 追加摘要消息（如果 `summary_override` 存在）
    pub fn filter_focused(messages: &[Message], cfg: &FocusedConfig) -> Vec<Message> {
        let mut result = Vec::new();
        // 保留 system prompt
        if cfg.keep_system
            && let Some(msg) = messages
                .iter()
                .find(|m| matches!(m, Message::System { .. }))
        {
            result.push(msg.clone());
        }
        // 处理 recent_messages=0 边界：上面已处理 system，下面仅取最近 N 条
        if cfg.recent_messages > 0 {
            let recent: Vec<&Message> = messages
                .iter()
                .filter(|m| !matches!(m, Message::System { .. }))
                .collect();
            let start = recent.len().saturating_sub(cfg.recent_messages);
            for msg in recent.iter().skip(start) {
                result.push((*msg).clone());
            }
        }
        // 注入摘要
        if let Some(summary) = &cfg.summary_override {
            result.push(Message::system(format!("[上下文摘要] {}", summary)));
        }
        result
    }

    /// 返回消息列表。Focused 模式下按策略过滤（裁剪到最近 recent_messages 条）。
    pub fn load_messages(&self) -> Vec<Message> {
        match &self.config.mode {
            SlotMode::Focused(cfg) => Self::filter_focused(&self.messages, cfg),
            _ => self.messages.clone(),
        }
    }

    /// 从当前 slot 派生出独立的子 slot（不持久化，调用方负责 `save`）。
    ///
    /// 子 slot 的 `meta` 全新创建（`SlotMeta::new()`），不继承父 slot 的 `message_count`。
    /// 子 slot 的 `source` 标记为 `Derived { parent_id, strategy }`，血缘可追溯。
    pub fn fork(&self, child_id: String, strategy: DeriveStrategy) -> ContextSlot {
        let messages = match &strategy {
            DeriveStrategy::Full => self.messages.clone(),
            DeriveStrategy::Focused(cfg) => Self::filter_focused(&self.messages, cfg),
        };
        tracing::debug!(
            parent_id = %self.id,
            child_id = %child_id,
            ?strategy,
            "ContextSlot::fork"
        );
        ContextSlot {
            id: child_id,
            session_id: self.session_id.clone(),
            config: SlotConfig {
                mode: match &strategy {
                    DeriveStrategy::Full => SlotMode::Full,
                    DeriveStrategy::Focused(cfg) => SlotMode::Focused(cfg.clone()),
                },
                source: SlotSource::Derived {
                    parent_id: self.id.clone(),
                    strategy,
                },
                budget: self.config.budget.clone(),
                compact: self.config.compact,
            },
            messages,
            meta: SlotMeta::new(),
        }
    }

    /// 将子 slot 的消息合并到当前 slot。
    ///
    /// **注意**：本方法仅操作内存数据，不自动持久化。
    /// 调用方需在 merge 后自行调用 `self.save(&store)` 将结果写入后端存储。
    ///
    /// 防御性检查：
    /// - 禁止 self-merge（`self.id == child.id`）
    /// - 禁止跨 session merge
    /// - 禁止合并到 Readonly slot
    pub fn merge(&mut self, child: ContextSlot, strategy: MergeStrategy) -> Result<(), AgentError> {
        if self.id == child.id {
            return Err(AgentError::Config("不能将 slot 合并到自身".into()));
        }
        if self.session_id != child.session_id {
            return Err(AgentError::Config("不能合并不同 session 的 slot".into()));
        }
        if matches!(self.config.mode, SlotMode::Readonly) {
            return Err(AgentError::SlotReadonly("Readonly slot 不允许合并".into()));
        }

        tracing::debug!(
            self_id = %self.id,
            child_id = %child.id,
            ?strategy,
            "ContextSlot::merge"
        );

        match strategy {
            MergeStrategy::Append => {
                let count = child.messages.len();
                self.messages.extend(child.messages);
                self.meta.message_count += count;
            }
            MergeStrategy::Replace => {
                self.messages = child.messages;
                self.meta.message_count = self.messages.len();
            }
        }
        Ok(())
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::memory::store::InMemoryStore;

    fn make_store() -> std::sync::Arc<dyn MemoryStore> {
        std::sync::Arc::new(InMemoryStore::new())
    }

    fn make_slot(id: &str, session: &str) -> ContextSlot {
        ContextSlot::new(session, id, SlotConfig::default())
    }

    /// 提取 `Message` 的第一个 Text block 的内容（用于测试断言）。
    /// 返回 None 表示该消息不含纯文本 block。
    fn extract_text(msg: &Message) -> &str {
        use crate::llm::types::message::ContentBlock;
        let blocks = match msg {
            Message::System { content }
            | Message::User { content }
            | Message::Assistant { content } => content,
            Message::UserImage { .. } => return "",
            Message::ToolResult { content, .. } => content,
        };
        for block in blocks {
            if let ContentBlock::Text { text } = block {
                return text;
            }
        }
        ""
    }

    // ===== 持久化 =====

    #[tokio::test]
    async fn slot_save_load_roundtrip() {
        let store = make_store();
        let mut slot = make_slot("default", "s1");
        slot.append_messages(vec![Message::user_text("hi")]).unwrap();
        slot.append_messages(vec![Message::assistant("hello")]).unwrap();

        slot.save(&*store).await.unwrap();
        let loaded = ContextSlot::load("default", "s1", &*store).await.unwrap();
        let loaded = loaded.expect("slot should exist after save");
        assert_eq!(loaded.id, "default");
        assert_eq!(loaded.session_id, "s1");
        assert_eq!(loaded.messages.len(), 2);
        assert_eq!(loaded.meta.message_count, 2);
    }

    #[tokio::test]
    async fn slot_session_isolation() {
        let store = make_store();
        let mut a = make_slot("main", "sA");
        a.append_messages(vec![Message::user_text("only in A")])
            .unwrap();
        a.save(&*store).await.unwrap();

        let mut b = make_slot("main", "sB");
        b.append_messages(vec![Message::user_text("only in B")])
            .unwrap();
        b.save(&*store).await.unwrap();

        let loaded_a = ContextSlot::load("main", "sA", &*store).await.unwrap().unwrap();
        let loaded_b = ContextSlot::load("main", "sB", &*store).await.unwrap().unwrap();
        assert_eq!(extract_text(&loaded_a.messages[0]), "only in A");
        assert_eq!(extract_text(&loaded_b.messages[0]), "only in B");
    }

    #[tokio::test]
    async fn slot_derived_parent_id_recorded() {
        let store = make_store();
        let slot = ContextSlot::new(
            "s1",
            "child",
            SlotConfig {
                mode: SlotMode::Full,
                source: SlotSource::Derived {
                    parent_id: "default".to_string(),
                    strategy: DeriveStrategy::Full,
                },
                budget: ContextBudget::default(),
                compact: true,
            },
        );
        slot.save(&*store).await.unwrap();

        // rel_key 直接读
        let rel = store
            .get(&ContextSlot::rel_key("s1", "child"))
            .await
            .unwrap()
            .unwrap();
        assert_eq!(rel.content, "default");
    }

    #[tokio::test]
    async fn slot_readonly_rejects_write() {
        let mut slot = make_slot("ro", "s1");
        slot.config.mode = SlotMode::Readonly;
        let result = slot.append_messages(vec![Message::user_text("nope")]);
        assert!(matches!(result, Err(AgentError::SlotReadonly(_))));
        assert!(slot.messages.is_empty());
    }

    #[tokio::test]
    async fn slot_delete_then_load_none() {
        let store = make_store();
        let mut slot = make_slot("to_delete", "s1");
        slot.append_messages(vec![Message::user_text("hi")]).unwrap();
        slot.save(&*store).await.unwrap();

        ContextSlot::delete("to_delete", "s1", &*store).await.unwrap();
        let loaded = ContextSlot::load("to_delete", "s1", &*store).await.unwrap();
        assert!(loaded.is_none());
    }

    #[tokio::test]
    async fn slot_list_multiple() {
        let store = make_store();
        for id in ["alpha", "beta", "gamma"] {
            let mut s = make_slot(id, "sX");
            s.append_messages(vec![Message::user_text(id)]).unwrap();
            s.save(&*store).await.unwrap();
        }
        // 不同 session 不该列出
        let mut s2 = make_slot("alpha", "sY");
        s2.append_messages(vec![Message::user_text("y")]).unwrap();
        s2.save(&*store).await.unwrap();

        let metas = ContextSlot::list("sX", &*store).await.unwrap();
        assert_eq!(metas.len(), 3);
        let metas_y = ContextSlot::list("sY", &*store).await.unwrap();
        assert_eq!(metas_y.len(), 1);
    }

    // ===== Focused 模式 =====

    #[tokio::test]
    async fn slot_focused_recent_messages() {
        let mut slot = make_slot("f", "s1");
        slot.append_messages(vec![Message::system("sys")]).unwrap();
        for i in 0..5 {
            slot.append_messages(vec![Message::user_text(format!("u{i}"))])
                .unwrap();
            slot.append_messages(vec![Message::assistant(format!("a{i}"))])
                .unwrap();
        }
        slot.config.mode = SlotMode::Focused(FocusedConfig {
            keep_system: true,
            recent_messages: 3,
            summary_override: None,
        });

        let loaded = slot.load_messages();
        // system + 最近 3 条 (assistant 4, user 4, assistant 5 实际是按 vec 顺序取最近 3 条非 system)
        let has_sys = loaded.iter().any(|m| matches!(m, Message::System { .. }));
        assert!(has_sys, "system 提示应保留");
        // 最近 3 条非 system 应该是 a4, u4, a5 (按 messages 存储顺序的最后 3 条)
        assert_eq!(loaded.len(), 1 + 3);
    }

    #[tokio::test]
    async fn slot_focused_summary_override() {
        let mut slot = make_slot("f", "s1");
        slot.append_messages(vec![Message::user_text("u")]).unwrap();
        slot.append_messages(vec![Message::assistant("a")]).unwrap();
        slot.config.mode = SlotMode::Focused(FocusedConfig {
            keep_system: false,
            recent_messages: 100,
            summary_override: Some("讨论了 X".to_string()),
        });

        let loaded = slot.load_messages();
        // 2 条原始 + 1 条摘要 system = 3
        assert_eq!(loaded.len(), 3);
        // 最后一条是摘要
        if let Message::System { content } = &loaded[2] {
            let text = format!("{:?}", content);
            assert!(text.contains("上下文摘要"));
            assert!(text.contains("讨论了 X"));
        } else {
            panic!("最后一条应为 system 摘要");
        }
    }

    #[tokio::test]
    async fn slot_focused_zero_messages() {
        let mut slot = make_slot("f", "s1");
        slot.append_messages(vec![Message::system("sys")]).unwrap();
        slot.append_messages(vec![Message::user_text("u")]).unwrap();
        slot.config.mode = SlotMode::Focused(FocusedConfig {
            keep_system: true,
            recent_messages: 0,
            summary_override: None,
        });

        let loaded = slot.load_messages();
        // recent_messages=0 但 keep_system=true 应只含 system
        assert_eq!(loaded.len(), 1);
        assert!(matches!(loaded[0], Message::System { .. }));
    }

    // ===== 边界 =====

    #[tokio::test]
    async fn slot_empty_messages_roundtrip() {
        let store = make_store();
        let slot = make_slot("empty", "s1");
        slot.save(&*store).await.unwrap();
        let loaded = ContextSlot::load("empty", "s1", &*store).await.unwrap().unwrap();
        assert!(loaded.messages.is_empty());
        assert_eq!(loaded.meta.message_count, 0);
    }

    #[tokio::test]
    async fn slot_save_on_readonly_side_effect() {
        let store = make_store();
        let mut slot = make_slot("ro", "s1");
        slot.config.mode = SlotMode::Readonly;
        // save 本身允许（只禁止 append）
        slot.save(&*store).await.unwrap();
        let loaded = ContextSlot::load("ro", "s1", &*store).await.unwrap();
        assert!(loaded.is_some());
    }

    // ===== 派生 (derive_slot 行为) =====

    #[tokio::test]
    async fn derive_full_copies_parent_messages() {
        let mut parent = make_slot("p", "s1");
        for i in 0..3 {
            parent.append_messages(vec![Message::user_text(format!("u{i}"))])
                .unwrap();
        }

        // 模拟 derive_slot 内部 Full 策略
        let child_messages = parent.messages.clone();
        let child = ContextSlot::new(
            "s1",
            "c",
            SlotConfig {
                mode: SlotMode::Full,
                source: SlotSource::Derived {
                    parent_id: "p".to_string(),
                    strategy: DeriveStrategy::Full,
                },
                budget: ContextBudget::default(),
                compact: true,
            },
        );
        let mut child = child;
        child.messages = child_messages;
        let store = make_store();
        child.save(&*store).await.unwrap();

        let loaded = ContextSlot::load("c", "s1", &*store).await.unwrap().unwrap();
        assert_eq!(loaded.messages.len(), 3);
        assert!(matches!(loaded.config.source, SlotSource::Derived { .. }));
    }

    #[tokio::test]
    async fn derive_focused_filters_parent_messages() {
        let mut parent = make_slot("p", "s1");
        parent.append_messages(vec![Message::system("sys")]).unwrap();
        for i in 0..5 {
            parent.append_messages(vec![Message::user_text(format!("u{i}"))])
                .unwrap();
        }

        // 模拟 derive_slot 内部 Focused 策略：按 FocusedConfig 过滤
        let cfg = FocusedConfig {
            keep_system: true,
            recent_messages: 2,
            summary_override: None,
        };
        // 应用 load_messages 同样的过滤
        let mut filtered = Vec::new();
        if cfg.keep_system
            && let Some(m) = parent
                .messages
                .iter()
                .find(|m| matches!(m, Message::System { .. }))
        {
            filtered.push(m.clone());
        }
        if cfg.recent_messages > 0 {
            let recent: Vec<&Message> = parent
                .messages
                .iter()
                .filter(|m| !matches!(m, Message::System { .. }))
                .collect();
            let start = recent.len().saturating_sub(cfg.recent_messages);
            for m in recent.iter().skip(start) {
                filtered.push((*m).clone());
            }
        }

        assert_eq!(filtered.len(), 1 + 2); // system + 2 条
    }

    #[tokio::test]
    async fn derived_slot_loadable_independently() {
        let store = make_store();
        let mut parent = make_slot("p", "s1");
        parent.append_messages(vec![Message::user_text("u")]).unwrap();
        parent.save(&*store).await.unwrap();

        // 派生 child
        let mut child = ContextSlot::new(
            "s1",
            "c",
            SlotConfig {
                mode: SlotMode::Full,
                source: SlotSource::Derived {
                    parent_id: "p".to_string(),
                    strategy: DeriveStrategy::Full,
                },
                budget: ContextBudget::default(),
                compact: true,
            },
        );
        child.append_messages(vec![Message::user_text("derived msg")])
            .unwrap();
        child.save(&*store).await.unwrap();

        // child 可独立加载
        let loaded = ContextSlot::load("c", "s1", &*store).await.unwrap().unwrap();
        assert_eq!(loaded.messages.len(), 1);
        assert_eq!(extract_text(&loaded.messages[0]), "derived msg");
    }

    // ===== delete 保护 (AgentSession 层，但 ContextSlot.delete 不保护；逻辑测试在 session.rs) =====

    #[tokio::test]
    async fn slot_delete_cleans_all_records() {
        let store = make_store();
        let mut slot = ContextSlot::new(
            "s1",
            "x",
            SlotConfig {
                mode: SlotMode::Full,
                source: SlotSource::Derived {
                    parent_id: "p".to_string(),
                    strategy: DeriveStrategy::Full,
                },
                budget: ContextBudget::default(),
                compact: true,
            },
        );
        slot.append_messages(vec![Message::user_text("u")]).unwrap();
        slot.save(&*store).await.unwrap();

        // 确认所有记录存在
        assert!(store.get(&ContextSlot::data_key("s1", "x")).await.unwrap().is_some());
        assert!(store.get(&ContextSlot::meta_key("s1", "x")).await.unwrap().is_some());
        assert!(store.get(&ContextSlot::config_key("s1", "x")).await.unwrap().is_some());
        assert!(store.get(&ContextSlot::rel_key("s1", "x")).await.unwrap().is_some());

        ContextSlot::delete("x", "s1", &*store).await.unwrap();

        // data/meta/config 已删
        assert!(store.get(&ContextSlot::data_key("s1", "x")).await.unwrap().is_none());
        assert!(store.get(&ContextSlot::meta_key("s1", "x")).await.unwrap().is_none());
        assert!(store.get(&ContextSlot::config_key("s1", "x")).await.unwrap().is_none());
    }

    // ===== 基础类型测试 =====

    #[test]
    fn slot_meta_new_sets_zero_message_count() {
        let m = SlotMeta::new();
        assert_eq!(m.message_count, 0);
        assert_eq!(m.total_tokens, 0);
        assert!(m.parent_id.is_none());
    }

    #[test]
    fn context_budget_default_sum_128k() {
        let b = ContextBudget::default();
        assert_eq!(b.system + b.history + b.tools + b.tool_results + b.reserve, 128_000);
    }

    #[test]
    fn slot_config_default_is_full_new() {
        let c = SlotConfig::default();
        assert!(matches!(c.mode, SlotMode::Full));
        assert!(matches!(c.source, SlotSource::New));
        assert!(c.compact);
    }

    #[test]
    fn focused_config_serializes_roundtrip() {
        let cfg = FocusedConfig {
            keep_system: true,
            recent_messages: 5,
            summary_override: Some("sum".into()),
        };
        let json = serde_json::to_string(&cfg).unwrap();
        let back: FocusedConfig = serde_json::from_str(&json).unwrap();
        assert_eq!(back.recent_messages, 5);
        assert_eq!(back.summary_override.as_deref(), Some("sum"));
    }

    // ====== filter_focused 静态方法（被 load_messages 和 derive_slot 复用） ======

    #[test]
    fn filter_focused_keeps_system_and_recent() {
        let mut messages = vec![Message::system("sys")];
        for i in 0..5 {
            messages.push(Message::user_text(format!("u{i}")));
            messages.push(Message::assistant(format!("a{i}")));
        }
        let cfg = FocusedConfig {
            keep_system: true,
            recent_messages: 3,
            summary_override: None,
        };
        let filtered = ContextSlot::filter_focused(&messages, &cfg);
        // system + 3 条最近的非 system 消息
        assert_eq!(filtered.len(), 1 + 3);
        assert!(matches!(filtered[0], Message::System { .. }));
    }

    #[test]
    fn filter_focused_injects_summary() {
        let messages = vec![
            Message::user_text("u"),
            Message::assistant("a"),
        ];
        let cfg = FocusedConfig {
            keep_system: false,
            recent_messages: 100,
            summary_override: Some("讨论了 X".into()),
        };
        let filtered = ContextSlot::filter_focused(&messages, &cfg);
        // 2 条原始 + 1 条摘要 system
        assert_eq!(filtered.len(), 3);
        if let Message::System { content } = &filtered[2] {
            let text = format!("{:?}", content);
            assert!(text.contains("上下文摘要"));
        } else {
            panic!("最后一条应为 system 摘要");
        }
    }

    // ====== Phase 13: fork/merge ======

    #[test]
    fn fork_full_copies_messages() {
        let mut parent = make_slot("p", "s1");
        parent.append_messages(vec![Message::user_text("a")]).unwrap();
        parent.append_messages(vec![Message::assistant("b")]).unwrap();
        let child = parent.fork("c".into(), DeriveStrategy::Full);
        assert_eq!(child.messages.len(), 2);
        assert!(matches!(child.config.mode, SlotMode::Full));
    }

    #[test]
    fn fork_focused_filters_messages() {
        let mut parent = make_slot("p", "s1");
        parent.append_messages(vec![Message::system("sys")]).unwrap();
        for i in 0..5 {
            parent
                .append_messages(vec![Message::user_text(format!("u{i}"))])
                .unwrap();
        }
        let cfg = FocusedConfig {
            keep_system: true,
            recent_messages: 2,
            summary_override: None,
        };
        let child = parent.fork("c".into(), DeriveStrategy::Focused(cfg));
        // system + 最近 2 条非 system
        assert_eq!(child.messages.len(), 1 + 2);
        assert!(matches!(child.config.mode, SlotMode::Focused(_)));
    }

    #[test]
    fn fork_preserves_independence() {
        let mut parent = make_slot("p", "s1");
        parent.append_messages(vec![Message::user_text("a")]).unwrap();
        let mut child = parent.fork("c".into(), DeriveStrategy::Full);
        let child_count_at_fork = child.messages.len();

        // 父 slot 追加
        parent
            .append_messages(vec![Message::user_text("b")])
            .unwrap();
        // 子 slot 追加
        child.append_messages(vec![Message::user_text("c")]).unwrap();

        assert_eq!(parent.messages.len(), 2);
        assert_eq!(child.messages.len(), child_count_at_fork + 1);
        assert_eq!(extract_text(child.messages.last().unwrap()), "c");
    }

    #[test]
    fn fork_sets_derived_source() {
        let mut parent = make_slot("p", "s1");
        parent.append_messages(vec![Message::user_text("a")]).unwrap();
        let child = parent.fork("c".into(), DeriveStrategy::Full);
        match &child.config.source {
            SlotSource::Derived { parent_id, strategy } => {
                assert_eq!(parent_id, "p");
                assert!(matches!(strategy, DeriveStrategy::Full));
            }
            _ => panic!("子 slot source 应为 Derived"),
        }
        // 子 slot 的 meta 全新创建
        assert_eq!(child.meta.message_count, 0);
        assert!(child.meta.parent_id.is_none());
    }

    #[test]
    fn merge_append_appends_messages() {
        let mut parent = make_slot("p", "s1");
        parent.append_messages(vec![Message::user_text("p1")]).unwrap();
        let child = {
            let mut c = parent.fork("c".into(), DeriveStrategy::Full);
            // fork 时 child 继承父的 "p1"；再追加一条 c1
            c.append_messages(vec![Message::user_text("c1")]).unwrap();
            c
        };
        parent
            .merge(child, MergeStrategy::Append)
            .expect("merge ok");
        // Append 追加 child 全部消息到父：1 (p1) + 2 (p1 + c1) = 3
        assert_eq!(parent.messages.len(), 3);
        assert_eq!(parent.meta.message_count, 3);
        assert_eq!(extract_text(&parent.messages[2]), "c1");
    }

    #[test]
    fn merge_replace_replaces_messages() {
        let mut parent = make_slot("p", "s1");
        parent.append_messages(vec![Message::user_text("p1")]).unwrap();
        parent.append_messages(vec![Message::user_text("p2")]).unwrap();
        let child = {
            let mut c = parent.fork("c".into(), DeriveStrategy::Full);
            // 清空 child 再追加
            c.messages.clear();
            c.append_messages(vec![Message::user_text("c-only")])
                .unwrap();
            c
        };
        parent
            .merge(child, MergeStrategy::Replace)
            .expect("merge ok");
        assert_eq!(parent.messages.len(), 1);
        assert_eq!(extract_text(&parent.messages[0]), "c-only");
        assert_eq!(parent.meta.message_count, 1);
    }

    #[test]
    fn merge_self_rejected() {
        let mut slot = make_slot("p", "s1");
        slot.append_messages(vec![Message::user_text("a")]).unwrap();
        let child = slot.fork("p".into(), DeriveStrategy::Full);
        let err = slot.merge(child, MergeStrategy::Append).unwrap_err();
        assert!(matches!(err, AgentError::Config(_)));
    }

    #[test]
    fn merge_readonly_rejected() {
        let mut parent = make_slot("p", "s1");
        parent.config.mode = SlotMode::Readonly;
        let child = ContextSlot::new("s1", "c", SlotConfig::default());
        let err = parent.merge(child, MergeStrategy::Append).unwrap_err();
        assert!(matches!(err, AgentError::SlotReadonly(_)));
    }

    #[test]
    fn merge_cross_session_rejected() {
        let mut parent = make_slot("p", "s1");
        parent.append_messages(vec![Message::user_text("a")]).unwrap();
        let child = ContextSlot::new("OTHER_SESSION", "c", SlotConfig::default());
        let err = parent.merge(child, MergeStrategy::Append).unwrap_err();
        assert!(matches!(err, AgentError::Config(_)));
    }

    // ====== Colon 校验（key 格式保护） ======

    #[test]
    #[should_panic(expected = "session_id 's:1' contains ':'")]
    fn key_constructor_rejects_colon_in_session_id() {
        // 通过 make_slot 间接调用 slot.save 时会触发 data_key -> assert_no_colon
        let store = make_store();
        let slot = ContextSlot::new("s:1", "default", SlotConfig::default());
        let _ = tokio_test_runtime(slot.save(&*store));
    }

    #[test]
    #[should_panic(expected = "slot_id 'a:b' contains ':'")]
    fn key_constructor_rejects_colon_in_slot_id() {
        let store = make_store();
        let slot = ContextSlot::new("s1", "a:b", SlotConfig::default());
        let _ = tokio_test_runtime(slot.save(&*store));
    }

    /// 在同步测试中运行 future 的辅助函数。
    fn tokio_test_runtime<F: std::future::Future>(f: F) -> F::Output {
        tokio::runtime::Builder::new_current_thread()
            .enable_all()
            .build()
            .unwrap()
            .block_on(f)
    }
}