package handler

import (
	"net/http"
	"strings"

	"dbview/service/internal/common/response"
	"dbview/service/internal/modules/mcp_ai/api"
	"dbview/service/internal/modules/mcp_ai/service"

	"github.com/gin-gonic/gin"
)

// Handler 提供 AI 聊天接口的 HTTP 处理器。
type Handler struct {
	svc *service.AIService
}

// NewHandler 创建 Handler。
func NewHandler(svc *service.AIService) *Handler {
	return &Handler{svc: svc}
}

// Chat 提供 POST /ai/chat 接口。
// 支持三种模式：
// - sync（默认）：同步返回完整文本。
// - stream：SSE 流式返回（同一路径，header 设为 text/event-stream）。
// - async：创建后台任务立即返回 task_id/request_id。
func (h *Handler) Chat(c *gin.Context) {
	var req api.ChatRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, response.Response{Code: 1, Msg: "参数错误", Error: err.Error()})
		return
	}

	mode := strings.ToLower(strings.TrimSpace(req.Mode))
	if mode == "" {
		mode = "sync"
	}

	ctx := c.Request.Context()

	switch mode {
	case "async":
		taskObj, requestID, err := h.svc.StartChatTask(ctx, req.SessionID, req.Prompt, req.System, req.Model, req.ConfigID, req.RequestID, req.TimeoutMs)
		if err != nil {
			c.JSON(http.StatusBadRequest, response.Response{Code: 2, Msg: "创建任务失败", Error: err.Error()})
			return
		}
		c.JSON(http.StatusOK, response.Response{Code: 0, Msg: "ok", Data: api.ChatResponse{Mode: "async", TaskID: taskObj.ID, RequestID: requestID}})
		return

	case "stream":
		c.Writer.Header().Set("Content-Type", "text/event-stream")
		c.Writer.Header().Set("Cache-Control", "no-cache")
		c.Writer.Header().Set("Connection", "keep-alive")

		flusher, ok := c.Writer.(http.Flusher)
		if !ok {
			c.JSON(http.StatusInternalServerError, response.Response{Code: 2, Msg: "AI 调用失败", Error: "stream not supported"})
			return
		}

		resultCh := make(chan struct {
			text string
			err  error
		}, 1)

		go func() {
			text, err := h.svc.Chat(ctx, req.SessionID, req.Prompt, req.System, req.Model, req.ConfigID, req.RequestID, req.TimeoutMs)
			resultCh <- struct {
				text string
				err  error
			}{text: text, err: err}
		}()

		c.SSEvent("start", gin.H{"request_id": req.RequestID})
		flusher.Flush()
		select {
		case <-ctx.Done():
			c.SSEvent("error", gin.H{"error": ctx.Err().Error()})
			flusher.Flush()
			return
		case res := <-resultCh:
			if res.err != nil {
				c.SSEvent("error", gin.H{"error": res.err.Error()})
				flusher.Flush()
				return
			}
			c.SSEvent("message", gin.H{"text": res.text})
			flusher.Flush()
			c.SSEvent("done", gin.H{"request_id": req.RequestID})
			flusher.Flush()
		}
		return

	default:
		text, err := h.svc.Chat(ctx, req.SessionID, req.Prompt, req.System, req.Model, req.ConfigID, req.RequestID, req.TimeoutMs)
		if err != nil {
			c.JSON(http.StatusInternalServerError, response.Response{Code: 2, Msg: "AI 调用失败", Error: err.Error()})
			return
		}
		c.JSON(http.StatusOK, response.Response{Code: 0, Msg: "ok", Data: api.ChatResponse{Mode: "sync", Text: text, RequestID: req.RequestID}})
	}
}

// CancelChat 提供 POST /ai/chat/cancel 接口，取消指定聊天请求。
func (h *Handler) CancelChat(c *gin.Context) {
	var req api.CancelChatRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, response.Response{Code: 1, Msg: "参数错误", Error: err.Error()})
		return
	}

	if req.RequestID == "" && req.SessionID == "" {
		c.JSON(http.StatusBadRequest, response.Response{Code: 1, Msg: "参数错误", Error: "request_id 或 session_id 必填其一"})
		return
	}

	if err := h.svc.CancelChat(req.RequestID, req.SessionID); err != nil {
		c.JSON(http.StatusBadRequest, response.Response{Code: 2, Msg: "取消失败", Error: err.Error()})
		return
	}

	c.JSON(http.StatusOK, response.Response{Code: 0, Msg: "ok"})
}

// History 提供 POST /ai/history 接口，查询指定 session 的消息历史，按时间正序返回。
func (h *Handler) History(c *gin.Context) {
	var req api.HistoryRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, response.Response{Code: 1, Msg: "参数错误", Error: err.Error()})
		return
	}

	msgs, err := h.svc.ListHistory(c.Request.Context(), req.SessionID, req.Limit, req.Offset)
	if err != nil {
		c.JSON(http.StatusInternalServerError, response.Response{Code: 2, Msg: "获取历史失败", Error: err.Error()})
		return
	}

	c.JSON(http.StatusOK, response.Response{Code: 0, Msg: "ok", Data: api.HistoryResponse{Messages: msgs}})
}

// DeleteHistory 提供 POST /ai/history/delete 接口，删除指定 session 的全部历史。
func (h *Handler) DeleteHistory(c *gin.Context) {
	var req api.DeleteHistoryRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, response.Response{Code: 1, Msg: "参数错误", Error: err.Error()})
		return
	}

	if err := h.svc.DeleteHistory(c.Request.Context(), req.SessionID); err != nil {
		c.JSON(http.StatusInternalServerError, response.Response{Code: 2, Msg: "删除历史失败", Error: err.Error()})
		return
	}

	c.JSON(http.StatusOK, response.Response{Code: 0, Msg: "ok"})
}

// GetConfig 提供 POST /ai/config/get 接口，返回当前 AI 配置。
func (h *Handler) GetConfig(c *gin.Context) {
	cfg, err := h.svc.GetConfig(c.Request.Context())
	if err != nil {
		c.JSON(http.StatusInternalServerError, response.Response{Code: 2, Msg: "获取 AI 配置失败", Error: err.Error()})
		return
	}

	c.JSON(http.StatusOK, response.Response{Code: 0, Msg: "ok", Data: api.ConfigResponse{AISettings: *cfg}})
}

// ListConfigs 提供 POST /ai/config/list 接口，返回全部 AI 配置记录。
func (h *Handler) ListConfigs(c *gin.Context) {
	items, err := h.svc.ListConfigs(c.Request.Context())
	if err != nil {
		c.JSON(http.StatusInternalServerError, response.Response{Code: 2, Msg: "获取 AI 配置列表失败", Error: err.Error()})
		return
	}

	c.JSON(http.StatusOK, response.Response{Code: 0, Msg: "ok", Data: api.ConfigListResponse{Items: items}})
}

// UpdateConfig 提供 POST /ai/config/update 接口，允许用户覆盖 AI 配置。
func (h *Handler) UpdateConfig(c *gin.Context) {
	var req api.UpdateConfigRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, response.Response{Code: 1, Msg: "参数错误", Error: err.Error()})
		return
	}

	updated, err := h.svc.UpdateConfig(c.Request.Context(), req.AISettings)
	if err != nil {
		c.JSON(http.StatusInternalServerError, response.Response{Code: 2, Msg: "更新 AI 配置失败", Error: err.Error()})
		return
	}

	c.JSON(http.StatusOK, response.Response{Code: 0, Msg: "ok", Data: api.ConfigResponse{AISettings: *updated}})
}

// CreateConfig 提供 POST /ai/config/create 接口，创建/覆盖 AI 配置。
func (h *Handler) CreateConfig(c *gin.Context) {
	var req api.CreateConfigRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, response.Response{Code: 1, Msg: "参数错误", Error: err.Error()})
		return
	}

	created, err := h.svc.CreateConfig(c.Request.Context(), req.AISettings)
	if err != nil {
		c.JSON(http.StatusInternalServerError, response.Response{Code: 2, Msg: "创建 AI 配置失败", Error: err.Error()})
		return
	}

	c.JSON(http.StatusOK, response.Response{Code: 0, Msg: "ok", Data: api.ConfigResponse{AISettings: *created}})
}

// DeleteConfig 提供 POST /ai/config/delete 接口，删除指定 AI 配置（默认 default）。
func (h *Handler) DeleteConfig(c *gin.Context) {
	var req api.DeleteConfigRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, response.Response{Code: 1, Msg: "参数错误", Error: err.Error()})
		return
	}

	if err := h.svc.DeleteConfig(c.Request.Context(), req.ID); err != nil {
		c.JSON(http.StatusInternalServerError, response.Response{Code: 2, Msg: "删除 AI 配置失败", Error: err.Error()})
		return
	}

	c.JSON(http.StatusOK, response.Response{Code: 0, Msg: "ok"})
}