// Package mcp 实现 MCP 协议网关，把工具注册到 NATS 并响应调用。
package mcp

import (
	"context"
	"encoding/json"
	"fmt"
	"log"
	"strings"

	sharedbus "github.com/sundynix/sundynix-shared/bus"
	"github.com/sundynix/sundynix-shared/contract"

	"github.com/sundynix/sundynix-mcp-go/internal/history"
	"github.com/sundynix/sundynix-mcp-go/internal/memory"
	"github.com/sundynix/sundynix-mcp-go/internal/rag"
	"github.com/sundynix/sundynix-mcp-go/internal/search"
)

// Gateway 暴露 MCP 协议端点，经共享 bus 订阅 sundynix.tools.go.* 响应调用。
type Gateway struct {
	bus     *sharedbus.Bus
	search  *search.Hybrid
	memory  *memory.Store
	history *history.Store
	rag     *rag.Engine
}

func NewGateway(b *sharedbus.Bus, s *search.Hybrid, m *memory.Store, h *history.Store, r *rag.Engine) *Gateway {
	return &Gateway{bus: b, search: s, memory: m, history: h, rag: r}
}

// Serve 以队列组通配订阅 sundynix.tools.go.>，按工具名分发并阻塞。
func (g *Gateway) Serve(ctx context.Context) error {
	unsub, err := g.bus.ServeTool(contract.SubjectToolsGoAll, contract.QueueToolsGo, g.dispatch)
	if err != nil {
		return err
	}
	defer func() { _ = unsub() }()
	log.Printf("[mcp_go] tools ready on %s (queue=%s): wiki_search, kb_ingest, memory_get, memory_upsert, history_get, history_append, echo",
		contract.SubjectToolsGoAll, contract.QueueToolsGo)
	<-ctx.Done()
	return ctx.Err()
}

// dispatch 按 ToolCall.Tool 路由到具体工具实现。
func (g *Gateway) dispatch(ctx context.Context, call *contract.ToolCall) *contract.ToolResult {
	log.Printf("[mcp_go] tool=%s task=%s args=%v", call.Tool, call.TaskID, call.Args)
	switch call.Tool {
	case "wiki_search":
		return g.wikiSearch(ctx, call)
	case "kb_ingest":
		return g.kbIngest(ctx, call)
	case "memory_get":
		return g.memoryGet(ctx, call)
	case "memory_upsert":
		return g.memoryUpsert(ctx, call)
	case "history_get":
		return g.historyGet(ctx, call)
	case "history_append":
		return g.historyAppend(ctx, call)
	case "echo":
		return &contract.ToolResult{OK: true, Content: fmt.Sprint(call.Args["text"])}
	default:
		return &contract.ToolResult{OK: false, Error: "unknown tool: " + call.Tool}
	}
}

// memoryGet 召回某用户的常驻画像（已渲染为可注入 prompt 的多行文本）。
func (g *Gateway) memoryGet(ctx context.Context, call *contract.ToolCall) *contract.ToolResult {
	uid, _ := call.Args["user_id"].(string)
	profile, err := g.memory.Get(ctx, uid)
	if err != nil {
		return &contract.ToolResult{OK: false, Error: "memory_get: " + err.Error()}
	}
	return &contract.ToolResult{OK: true, Content: profile}
}

// historyGet 召回某会话最近多轮历史，Content 为 JSON 数组 [{role,content},...]（正序）。
func (g *Gateway) historyGet(ctx context.Context, call *contract.ToolCall) *contract.ToolResult {
	session, _ := call.Args["session_id"].(string)
	turns, err := g.history.Get(ctx, session)
	if err != nil {
		return &contract.ToolResult{OK: false, Error: "history_get: " + err.Error()}
	}
	data, _ := json.Marshal(turns)
	return &contract.ToolResult{OK: true, Content: string(data)}
}

// historyAppend 追加一条会话消息（session_id + role + content）。
func (g *Gateway) historyAppend(ctx context.Context, call *contract.ToolCall) *contract.ToolResult {
	session, _ := call.Args["session_id"].(string)
	role, _ := call.Args["role"].(string)
	content, _ := call.Args["content"].(string)
	if session == "" || role == "" {
		return &contract.ToolResult{OK: false, Error: "history_append: session_id 和 role 必填"}
	}
	if err := g.history.Append(ctx, session, role, content); err != nil {
		return &contract.ToolResult{OK: false, Error: "history_append: " + err.Error()}
	}
	return &contract.ToolResult{OK: true}
}

// memoryUpsert 写入/更新一条画像偏好（user_id + key + value）。
func (g *Gateway) memoryUpsert(ctx context.Context, call *contract.ToolCall) *contract.ToolResult {
	uid, _ := call.Args["user_id"].(string)
	key, _ := call.Args["key"].(string)
	val, _ := call.Args["value"].(string)
	if uid == "" || key == "" {
		return &contract.ToolResult{OK: false, Error: "memory_upsert: user_id 和 key 必填"}
	}
	if err := g.memory.Upsert(ctx, uid, key, val); err != nil {
		return &contract.ToolResult{OK: false, Error: "memory_upsert: " + err.Error()}
	}
	return &contract.ToolResult{OK: true, Content: fmt.Sprintf("已记住 %s 的「%s」", uid, key)}
}

// wikiSearch 经 RAG 引擎做向量检索（embedding + Milvus）。
// RAG 未就绪时降级返回空命中（不阻断图执行）。
func (g *Gateway) wikiSearch(ctx context.Context, call *contract.ToolCall) *contract.ToolResult {
	q, _ := call.Args["q"].(string)
	kb, _ := call.Args["kb"].(string)
	topK := 5
	if v, ok := call.Args["topK"].(float64); ok && v > 0 {
		topK = int(v)
	}
	if !g.rag.Ready() {
		return &contract.ToolResult{OK: true, Content: "[wiki_search] RAG 未配置（需 embedding + Milvus），无召回"}
	}
	hits, err := g.rag.Search(ctx, kb, q, topK)
	if err != nil {
		return &contract.ToolResult{OK: false, Error: "wiki_search: " + err.Error()}
	}
	var b strings.Builder
	fmt.Fprintf(&b, "[wiki_search] 命中 %d 条（Milvus 向量检索）：\n", len(hits))
	for i, h := range hits {
		fmt.Fprintf(&b, "%d. (%.3f) %s\n", i+1, h.Score, h.Text)
	}
	return &contract.ToolResult{OK: true, Content: strings.TrimRight(b.String(), "\n")}
}

// kbIngest 把文本入库（切块→embedding→Milvus）。
func (g *Gateway) kbIngest(ctx context.Context, call *contract.ToolCall) *contract.ToolResult {
	kb, _ := call.Args["kb"].(string)
	text, _ := call.Args["text"].(string)
	if text == "" {
		return &contract.ToolResult{OK: false, Error: "kb_ingest: text 必填"}
	}
	n, err := g.rag.Ingest(ctx, kb, text)
	if err != nil {
		return &contract.ToolResult{OK: false, Error: "kb_ingest: " + err.Error()}
	}
	return &contract.ToolResult{OK: true, Content: fmt.Sprintf("已入库 %d 块到知识库 %q", n, kb)}
}