//! 脉络卡数据面(跨会话召回四层架构 L3 用户侧辅助通道):
//! 按 source_project 聚合 published 知识,给前端新会话入口展示「这个项目之前定了什么」。
//!
//! 铁律红线:本通道只喂「用户看的卡」,不进 system、不进消息流——用户点「带入上下文」
//! 才经正常发送路径显式注入(用户决策,非 LLM 自动召回)。

use tauri::State;

use crate::commands::ai::knowledge_inject::resolve_source_project;

/// 单条脉络摘要(字段前端契约,snake_case)
#[derive(serde::Serialize, Clone, Debug)]
pub struct ContextBrief {
    pub title: String,
    pub summary: String,
    pub source_ref: Option<String>,
    pub source_project: Option<String>,
    pub reuse_count: i32,
    /// 知识条目最近更新时间,原样透供前端展示「这条什么时候定的」
    pub updated_at: String,
    /// 可跳转的来源会话 id(自 source_ref 解析,消息级引用经 ai_messages 反查);
    /// 解析不出(无源/引用失效)为 None,前端降级纯文本标题
    pub source_conv: Option<String>,
}

/// 项目脉络分组
#[derive(serde::Serialize, Clone, Debug)]
pub struct ProjectBriefs {
    pub source_project: String,
    /// 是否为当前会话归属项目(仅传 focus_conv 且解析命中时为 true,前端做置顶高亮)
    pub focused: bool,
    pub briefs: Vec<ContextBrief>,
}

/// 单条摘要截断上限(字符):脉络卡是扫一眼的导航,不是全文阅读,超长压到一行半
const BRIEF_SUMMARY_MAX_CHARS: usize = 120;

fn truncate_chars(s: &str, max: usize) -> String {
    if s.chars().count() <= max {
        return s.to_string();
    }
    let mut out: String = s.chars().take(max).collect();
    out.push('…');
    out
}

/// source_ref 溯源引用的三种形态:对话级 `conv:{id}` 直接可跳;
/// 消息级 `conv_msg:{msg_id}` 须查 ai_messages 反查会话;其余(空/异形)不可跳。
enum SourceConvRef {
    Conv(String),
    Msg(String),
    None,
}

fn parse_source_conv(source_ref: Option<&str>) -> SourceConvRef {
    let Some(r) = source_ref else {
        return SourceConvRef::None;
    };
    if let Some(id) = r.strip_prefix("conv:") {
        if id.is_empty() {
            return SourceConvRef::None;
        }
        return SourceConvRef::Conv(id.to_string());
    }
    if let Some(id) = r.strip_prefix("conv_msg:") {
        if id.is_empty() {
            return SourceConvRef::None;
        }
        return SourceConvRef::Msg(id.to_string());
    }
    SourceConvRef::None
}

/// 回填 source_conv:对话级引用直接取 id,消息级引用批量反查 ai_messages(一条 IN 查询,
/// 引用失效/表查不到保持 None,前端降级纯文本)。
async fn fill_source_convs(db: &df_storage::db::Database, groups: &mut [ProjectBriefs]) {
    for g in groups.iter_mut() {
        for b in g.briefs.iter_mut() {
            if let SourceConvRef::Conv(id) = parse_source_conv(b.source_ref.as_deref()) {
                b.source_conv = Some(id);
            }
        }
    }
    let msg_ids: Vec<String> = groups
        .iter()
        .flat_map(|g| g.briefs.iter())
        .filter_map(|b| match parse_source_conv(b.source_ref.as_deref()) {
            SourceConvRef::Msg(id) => Some(id),
            _ => None,
        })
        .collect::<std::collections::HashSet<_>>()
        .into_iter()
        .collect();
    if msg_ids.is_empty() {
        return;
    }
    let conn = db.conn();
    let guard = conn.lock().await;
    let Ok(mut stmt) = guard.prepare("SELECT conversation_id FROM ai_messages WHERE id = ?1")
    else {
        return;
    };
    let mut found: std::collections::HashMap<String, String> = std::collections::HashMap::new();
    for id in &msg_ids {
        if let Ok(rows) = stmt.query_map([id], |row| row.get::<_, String>(0)) {
            for conv_id in rows.flatten() {
                found.insert(id.clone(), conv_id);
            }
        }
    }
    drop(stmt);
    for g in groups.iter_mut() {
        for b in g.briefs.iter_mut() {
            if b.source_conv.is_some() {
                continue;
            }
            if let SourceConvRef::Msg(id) = parse_source_conv(b.source_ref.as_deref()) {
                b.source_conv = found.get(&id).cloned();
            }
        }
    }
}

/// 聚合纯函数:published 记录 → 按项目分组脉络。无归属项目(source_project None)的知识
/// 不入脉络卡(无分组锚点,注入侧 top-3 已覆盖全局知识);每组按 reuse_count 降序(唯一
/// 客观信号),组间按组内最高复用数降序(活跃项目排前);`focus_project` 命中的组置顶
/// (当前会话归属项目优先展示),未命中/不传时顺序与置顶逻辑不存在时完全一致。
fn aggregate_briefs(
    records: Vec<df_storage::models::KnowledgeRecord>,
    per_project: usize,
    focus_project: Option<&str>,
) -> Vec<ProjectBriefs> {
    use std::collections::HashMap;
    let mut groups: HashMap<String, Vec<ContextBrief>> = HashMap::new();
    for r in records {
        let Some(proj) = r.source_project.clone() else {
            continue;
        };
        let brief = ContextBrief {
            title: truncate_chars(&r.title, 60),
            summary: truncate_chars(&r.content, BRIEF_SUMMARY_MAX_CHARS),
            source_ref: r.source_ref,
            source_project: Some(proj.clone()),
            reuse_count: r.reuse_count,
            updated_at: r.updated_at,
            source_conv: None,
        };
        groups.entry(proj).or_default().push(brief);
    }
    let mut out: Vec<ProjectBriefs> = groups
        .into_iter()
        .map(|(source_project, mut briefs)| {
            briefs.sort_by(|a, b| b.reuse_count.cmp(&a.reuse_count));
            briefs.truncate(per_project);
            let focused = focus_project == Some(source_project.as_str());
            ProjectBriefs { source_project, focused, briefs }
        })
        .collect();
    out.sort_by(|a, b| {
        let top = |g: &ProjectBriefs| g.briefs.first().map(|b| b.reuse_count).unwrap_or(0);
        top(b).cmp(&top(a))
    });
    if let Some(focus) = focus_project {
        if let Some(pos) = out.iter().position(|g| g.source_project == focus) {
            let focused_group = out.remove(pos);
            out.insert(0, focused_group);
        }
    }
    out
}

/// 脉络卡数据:published 知识按 source_project 聚合(每项目取复用最高的 `per_project` 条)。
/// `focus_conv` 传当前会话 id 时解析其归属项目,命中组置顶并带 `focused` 标记;解析失败/
/// 无归属时与不传该参数行为完全一致(软排序只调顺序,不报错不缩面)。
/// 纯读侧,无状态无副作用;knowledge 表空/无归属项目时返空(前端不渲染卡)。
#[tauri::command]
pub async fn ai_context_briefs(
    state: State<'_, crate::AppState>,
    per_project: Option<usize>,
    focus_conv: Option<String>,
) -> Result<Vec<ProjectBriefs>, String> {
    let records = state
        .knowledge
        .list_by_status("published")
        .await
        .map_err(|e| e.to_string())?;
    let focus_project = match focus_conv.as_deref() {
        Some(conv_id) => resolve_source_project(&state.db, conv_id, &[]).await,
        None => None,
    };
    let mut out = aggregate_briefs(records, per_project.unwrap_or(5), focus_project.as_deref());
    fill_source_convs(&state.db, &mut out).await;
    Ok(out)
}

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

    fn rec(title: &str, content: &str, project: Option<&str>, reuse: i32) -> df_storage::models::KnowledgeRecord {
        df_storage::models::KnowledgeRecord {
            id: format!("k-{title}"),
            kind: "pitfall".into(),
            title: title.into(),
            content: content.into(),
            tags: None,
            status: "published".into(),
            confidence: Some("high".into()),
            reuse_count: reuse,
            verified: true,
            source_project: project.map(Into::into),
            source_ref: Some("conv:test".into()),
            reasoning: None,
            embedding_status: None,
            created_at: "1700000000".into(),
            updated_at: "1700000000".into(),
        }
    }

    #[test]
    fn briefs_group_by_project_and_sort_by_reuse() {
        let recs = vec![
            rec("甲项目低复用", "c1", Some("proj-a"), 1),
            rec("甲项目高复用", "c2", Some("proj-a"), 9),
            rec("乙项目", "c3", Some("proj-b"), 3),
            rec("无归属不入卡", "c4", None, 99),
        ];
        let out = aggregate_briefs(recs, 5, None);
        assert_eq!(out.len(), 2, "两项目分组,无归属剔除: {out:?}");
        assert_eq!(out[0].source_project, "proj-a", "组间按最高复用降序");
        assert_eq!(out[0].briefs[0].title, "甲项目高复用", "组内按复用降序");
        assert!(out.iter().all(|g| !g.focused), "无 focus 时任何组不带置顶标记");
        assert!(out.iter().all(|g| g.briefs.iter().all(|b| b.source_project.is_some())));
    }

    #[test]
    fn briefs_truncate_per_project_and_summary() {
        let recs: Vec<_> = (0..8)
            .map(|i| rec(&format!("条{i}"), &"长".repeat(200), Some("proj"), i))
            .collect();
        let out = aggregate_briefs(recs, 3, None);
        assert_eq!(out[0].briefs.len(), 3, "每项目截断到 per_project");
        assert!(out[0].briefs[0].summary.chars().count() <= BRIEF_SUMMARY_MAX_CHARS + 1);
    }

    #[test]
    fn focus_project_group_moves_to_front() {
        let recs = vec![
            rec("乙高复用", "c1", Some("proj-b"), 9),
            rec("甲低复用", "c2", Some("proj-a"), 1),
        ];
        let out = aggregate_briefs(recs, 5, Some("proj-a"));
        assert_eq!(out[0].source_project, "proj-a", "会话归属项目组置顶(复用更低也排前): {out:?}");
        assert!(out[0].focused, "命中组带 focused 标记");
        assert!(!out[1].focused, "非命中组保持 focused=false");
    }

    fn group_order(groups: &[ProjectBriefs]) -> Vec<&str> {
        groups.iter().map(|g| g.source_project.as_str()).collect()
    }

    #[test]
    fn focus_unmatched_project_keeps_order() {
        let recs = vec![
            rec("乙高复用", "c1", Some("proj-b"), 9),
            rec("甲低复用", "c2", Some("proj-a"), 1),
        ];
        let plain = aggregate_briefs(recs.clone(), 5, None);
        let unmatched = aggregate_briefs(recs, 5, Some("proj-x"));
        assert_eq!(group_order(&plain), group_order(&unmatched), "解析无归属/未知项目时顺序不变");
        assert!(unmatched.iter().all(|g| !g.focused), "无命中组不误标记");
    }

    #[test]
    fn brief_carries_updated_at() {
        let mut r = rec("条目", "c", Some("proj"), 1);
        r.updated_at = "1777777777".into();
        let out = aggregate_briefs(vec![r], 5, None);
        assert_eq!(out[0].briefs[0].updated_at, "1777777777", "updated_at 原样透传");
    }

    #[test]
    fn source_ref_parses_to_conv_msg_or_none() {
        assert!(matches!(
            parse_source_conv(Some("conv:abc-1")),
            SourceConvRef::Conv(id) if id == "abc-1"
        ));
        assert!(matches!(
            parse_source_conv(Some("conv_msg:msg_123_4")),
            SourceConvRef::Msg(id) if id == "msg_123_4"
        ));
        assert!(matches!(parse_source_conv(Some("conv:")), SourceConvRef::None));
        assert!(matches!(parse_source_conv(Some("weird:x")), SourceConvRef::None));
        assert!(matches!(parse_source_conv(None), SourceConvRef::None));
    }

    #[tokio::test]
    async fn fill_source_convs_resolves_both_ref_kinds() {
        let db = df_storage::db::Database::open_in_memory()
            .await
            .expect("内存库");
        {
            let conn = db.conn();
            let guard = conn.lock().await;
            guard
                .execute(
                    "CREATE TABLE IF NOT EXISTS ai_messages (id TEXT PRIMARY KEY, conversation_id TEXT NOT NULL)",
                    [],
                )
                .expect("建表");
            guard
                .execute(
                    "INSERT INTO ai_messages (id, conversation_id, seq, role, created_at) VALUES \
                     ('msg_1_0', 'conv-a', 1, 'assistant', '0'), ('msg_2_0', 'conv-b', 2, 'assistant', '0')",
                    [],
                )
                .expect("造数");
        }
        let mut groups = vec![ProjectBriefs {
            source_project: "proj".into(),
            focused: false,
            briefs: vec![
                ContextBrief {
                    title: "对话级".into(),
                    summary: "s".into(),
                    source_ref: Some("conv:conv-a".into()),
                    source_project: Some("proj".into()),
                    reuse_count: 2,
                    updated_at: "1".into(),
                    source_conv: None,
                },
                ContextBrief {
                    title: "消息级".into(),
                    summary: "s".into(),
                    source_ref: Some("conv_msg:msg_2_0".into()),
                    source_project: Some("proj".into()),
                    reuse_count: 1,
                    updated_at: "1".into(),
                    source_conv: None,
                },
                ContextBrief {
                    title: "失效引用".into(),
                    summary: "s".into(),
                    source_ref: Some("conv_msg:msg_gone".into()),
                    source_project: Some("proj".into()),
                    reuse_count: 0,
                    updated_at: "1".into(),
                    source_conv: None,
                },
            ],
        }];
        fill_source_convs(&db, &mut groups).await;
        let briefs = &groups[0].briefs;
        assert_eq!(briefs[0].source_conv.as_deref(), Some("conv-a"), "对话级直接取 id");
        assert_eq!(briefs[1].source_conv.as_deref(), Some("conv-b"), "消息级反查回填");
        assert_eq!(briefs[2].source_conv, None, "失效引用降级 None");
    }
}