package migu

import (
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"strings"

	"yunyan/lego/sys/log"
	"yunyan/sys/migu"

	"github.com/google/uuid"
)

// handleChat 处理普通聊天接口 POST /chat（支持流式 SSE 与非流式 JSON）
//
// @Summary      咪咕灵犀聊天
// @Description  普通聊天接口，内部对接咪咕灵犀。
// @Description  stream=false：返回完整 JSON（ChatResponse），结构化音乐卡片在 cards 字段；
// @Description  stream=true：返回 SSE 流，每帧一个 ChatChunk（音乐卡片在 card 字段），结束以 data: [DONE]。
// @Description  鉴权：服务端配置了 ApiKey 时需带请求头 Authorization: Bearer <key>。
// @Tags         Migu
// @Accept       json
// @Produce      json
// @Produce      text/event-stream
// @Param        body  body      ChatRequest   true  "聊天请求"
// @Success      200   {object}  ChatResponse  "非流式完整响应；流式时为 SSE 流（data: {ChatChunk} ... data: [DONE]）"
// @Failure      400   {object}  map[string]string  "参数错误"
// @Failure      401   {object}  map[string]string  "鉴权失败"
// @Router       /chat [post]
func (this *Migu) handleChat(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		writeError(w, http.StatusMethodNotAllowed, "method not allowed")
		return
	}

	// 入站鉴权（配置了 ApiKey 才校验）
	if this.options.ApiKey != "" {
		token := strings.TrimSpace(strings.TrimPrefix(r.Header.Get("Authorization"), "Bearer"))
		if token != this.options.ApiKey {
			writeError(w, http.StatusUnauthorized, "invalid api key")
			return
		}
	}

	body, err := io.ReadAll(r.Body)
	if err != nil {
		writeError(w, http.StatusBadRequest, "read body failed: "+err.Error())
		return
	}
	var req ChatRequest
	if err = json.Unmarshal(body, &req); err != nil {
		writeError(w, http.StatusBadRequest, "invalid json: "+err.Error())
		return
	}
	if strings.TrimSpace(req.Message) == "" {
		writeError(w, http.StatusBadRequest, "message is required")
		return
	}

	// deviceId / sessionId 来源：请求体优先，其次请求头
	deviceId := req.DeviceId
	if deviceId == "" {
		deviceId = r.Header.Get("X-Device-Id")
	}
	sessionId := req.SessionId
	if sessionId == "" {
		sessionId = r.Header.Get("X-Session-Id")
	}

	miguReq := buildMiguRequest(&req, deviceId, sessionId)

	// 统一从咪咕流式拉取
	ch := make(chan *migu.StreamResp, 8)
	go func() {
		if e := migu.Chat(context.Background(), miguReq, ch); e != nil {
			log.Errorf("migu lingxi chat err: %v", e)
		}
	}()

	if req.Stream {
		this.streamResponse(w, r, miguReq, ch)
	} else {
		this.jsonResponse(w, miguReq, ch)
	}
}

// buildMiguRequest 把聊天请求转换成咪咕灵犀请求
func buildMiguRequest(req *ChatRequest, deviceId, sessionId string) *migu.Request {
	mr := &migu.Request{
		ReqId:    uuid.NewString(),
		DeviceId: deviceId,
		Messages: []migu.Message{{Role: "user", Content: req.Message}},
		Stream:   true,
	}
	if len(req.History) > 0 {
		history := make([]migu.Message, 0, len(req.History))
		for _, m := range req.History {
			history = append(history, migu.Message{Role: m.Role, Content: m.Content})
		}
		mr.History = history
	}
	// 咪咕要求 session 必填：未携带 sessionId 时用 reqId 兜底，保证字段存在
	if sessionId == "" {
		sessionId = mr.ReqId
	}
	mr.Session = &migu.Session{SessionId: sessionId}
	return mr
}

// streamResponse 把咪咕流式数据逐帧转换为 SSE（data: {ChatChunk}）写回客户端
func (this *Migu) streamResponse(w http.ResponseWriter, r *http.Request, mr *migu.Request, ch chan *migu.StreamResp) {
	flusher, ok := w.(http.Flusher)
	if !ok {
		writeError(w, http.StatusInternalServerError, "streaming unsupported")
		return
	}
	w.Header().Set("Content-Type", "text/event-stream")
	w.Header().Set("Cache-Control", "no-cache")
	w.Header().Set("Connection", "keep-alive")
	w.Header().Set("X-Accel-Buffering", "no")
	w.WriteHeader(http.StatusOK)

	ctx := r.Context()
	for {
		select {
		case <-ctx.Done():
			return
		case sr, alive := <-ch:
			if !alive {
				fmt.Fprint(w, "data: [DONE]\n\n")
				flusher.Flush()
				return
			}
			chunk := convertChunk(sr)
			if chunk == nil {
				continue
			}
			data, _ := json.Marshal(chunk)
			fmt.Fprintf(w, "data: %s\n\n", data)
			flusher.Flush()
		}
	}
}

// jsonResponse 累积咪咕流式数据，聚合为一个完整的结构化响应
func (this *Migu) jsonResponse(w http.ResponseWriter, mr *migu.Request, ch chan *migu.StreamResp) {
	resp := ChatResponse{
		ReqId:     mr.ReqId,
		SessionId: mr.Session.SessionId,
	}
	var contentBuf, reasoningBuf strings.Builder
	for sr := range ch {
		chunk := convertChunk(sr)
		if chunk == nil {
			continue
		}
		reasoningBuf.WriteString(chunk.Reasoning)
		contentBuf.WriteString(chunk.Content)
		if chunk.Card != nil {
			resp.Cards = append(resp.Cards, *chunk.Card)
		}
		resp.RecommendPrompts = append(resp.RecommendPrompts, chunk.RecommendPrompts...)
		if chunk.FinishReason != "" {
			resp.FinishReason = chunk.FinishReason
		}
	}
	resp.Reasoning = reasoningBuf.String()
	resp.Content = contentBuf.String()

	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(http.StatusOK)
	_ = json.NewEncoder(w).Encode(resp)
}