package services

import (
	"github.com/libaxuan/cursor2api-go/models"
	"github.com/libaxuan/cursor2api-go/utils"
	"encoding/json"
	"strings"
	"time"

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

type responseMessageState struct {
	id          string
	outputIndex int
	contentIdx  int
	text        strings.Builder
}

// StreamResponse streams a Responses API SSE stream from the Cursor generator.
func StreamResponse(c *gin.Context, chatGenerator <-chan interface{}, req *models.ResponseRequest, adapter *ResponseToolAdapter, responseID string) {
	c.Header("Content-Type", "text/event-stream")
	c.Header("Cache-Control", "no-cache")
	c.Header("Connection", "keep-alive")
	c.Header("Access-Control-Allow-Origin", "*")

	if strings.TrimSpace(responseID) == "" {
		responseID = utils.GenerateResponseID()
	}
	createdAt := time.Now().Unix()
	sequence := 0

	outputItems := make([]interface{}, 0, 4)
	outputText := strings.Builder{}
	nextOutputIndex := 0
	var usage *models.ResponseUsage
	var currentMsg *responseMessageState

	sendEvent := func(event string, payload map[string]interface{}) {
		sequence++
		payload["type"] = event
		payload["sequence_number"] = sequence
		if data, err := json.Marshal(payload); err == nil {
			if err := utils.WriteSSEEvent(c.Writer, event, string(data)); err != nil {
				logrus.WithError(err).Warn("failed to write response SSE event")
			}
		}
	}

	base := NewResponseFromRequest(req, responseID, createdAt, "in_progress", []interface{}{}, "", nil, nil)
	sendEvent("response.created", map[string]interface{}{"response": base})
	sendEvent("response.in_progress", map[string]interface{}{"response": base})

	openMessage := func() {
		if currentMsg != nil {
			return
		}
		msgID := utils.GenerateResponseItemID("msg_")
		idx := nextOutputIndex
		nextOutputIndex++
		currentMsg = &responseMessageState{
			id:          msgID,
			outputIndex: idx,
			contentIdx:  0,
		}

		item := models.ResponseOutputMessage{
			ID:      msgID,
			Type:    "message",
			Status:  "in_progress",
			Role:    "assistant",
			Content: []models.ResponseOutputTextContent{},
		}
		sendEvent("response.output_item.added", map[string]interface{}{
			"output_index": idx,
			"item":         item,
		})

		part := models.ResponseOutputTextContent{
			Type:        "output_text",
			Text:        "",
			Annotations: []interface{}{},
		}
		sendEvent("response.content_part.added", map[string]interface{}{
			"output_index":  idx,
			"content_index": currentMsg.contentIdx,
			"part":          part,
		})
	}

	closeMessage := func() {
		if currentMsg == nil {
			return
		}
		text := currentMsg.text.String()
		part := models.ResponseOutputTextContent{
			Type:        "output_text",
			Text:        text,
			Annotations: []interface{}{},
		}

		sendEvent("response.output_text.done", map[string]interface{}{
			"output_index":  currentMsg.outputIndex,
			"content_index": currentMsg.contentIdx,
			"text":          text,
		})
		sendEvent("response.content_part.done", map[string]interface{}{
			"output_index":  currentMsg.outputIndex,
			"content_index": currentMsg.contentIdx,
			"part":          part,
		})

		item := models.ResponseOutputMessage{
			ID:      currentMsg.id,
			Type:    "message",
			Status:  "completed",
			Role:    "assistant",
			Content: []models.ResponseOutputTextContent{part},
		}

		sendEvent("response.output_item.done", map[string]interface{}{
			"output_index": currentMsg.outputIndex,
			"item":         item,
		})

		outputItems = append(outputItems, item)
		currentMsg = nil
	}

	emitToolCall := func(toolCall models.ToolCall) {
		closeMessage()
		item := buildResponseToolCallItem(toolCall, adapter)
		idx := nextOutputIndex
		nextOutputIndex++

		added := withOutputItemStatus(item, "in_progress")
		sendEvent("response.output_item.added", map[string]interface{}{
			"output_index": idx,
			"item":         added,
		})

		if callInfo, ok := getFunctionCallInfo(item); ok {
			sendEvent("response.function_call_arguments.delta", map[string]interface{}{
				"output_index": idx,
				"item_id":      callInfo.ID,
				"delta":        callInfo.Arguments,
			})
			sendEvent("response.function_call_arguments.done", map[string]interface{}{
				"output_index": idx,
				"item_id":      callInfo.ID,
				"arguments":    callInfo.Arguments,
				"name":         callInfo.Name,
			})
		}

		done := withOutputItemStatus(item, "completed")
		sendEvent("response.output_item.done", map[string]interface{}{
			"output_index": idx,
			"item":         done,
		})

		outputItems = append(outputItems, done)
	}

	ctx := c.Request.Context()
	for {
		select {
		case <-ctx.Done():
			logrus.Debug("client disconnected during responses streaming")
			return
		case data, ok := <-chatGenerator:
			if !ok {
				closeMessage()
				completedAt := time.Now().Unix()
				final := NewResponseFromRequest(req, responseID, createdAt, "completed", outputItems, outputText.String(), usage, &completedAt)
				sendEvent("response.completed", map[string]interface{}{"response": final})
				return
			}

			switch v := data.(type) {
			case models.AssistantEvent:
				switch v.Kind {
				case models.AssistantEventText:
					if v.Text != "" {
						openMessage()
						currentMsg.text.WriteString(v.Text)
						outputText.WriteString(v.Text)
						sendEvent("response.output_text.delta", map[string]interface{}{
							"output_index":  currentMsg.outputIndex,
							"content_index": currentMsg.contentIdx,
							"delta":         v.Text,
						})
					}
				case models.AssistantEventToolCall:
					if v.ToolCall != nil {
						emitToolCall(*v.ToolCall)
					}
				}
			case string:
				if v != "" {
					openMessage()
					currentMsg.text.WriteString(v)
					outputText.WriteString(v)
					sendEvent("response.output_text.delta", map[string]interface{}{
						"output_index":  currentMsg.outputIndex,
						"content_index": currentMsg.contentIdx,
						"delta":         v,
					})
				}
			case models.Usage:
				usage = BuildResponseUsage(v)
			case error:
				logrus.WithError(v).Error("responses stream generator error")
				return
			default:
				continue
			}
		}
	}
}

type functionCallInfo struct {
	ID        string
	Name      string
	Arguments string
}

func getFunctionCallInfo(item interface{}) (*functionCallInfo, bool) {
	switch v := item.(type) {
	case models.ResponseFunctionCall:
		return &functionCallInfo{ID: v.ID, Name: v.Name, Arguments: v.Arguments}, true
	default:
		return nil, false
	}
}

func withOutputItemStatus(item interface{}, status string) interface{} {
	switch v := item.(type) {
	case models.ResponseOutputMessage:
		v.Status = status
		return v
	case models.ResponseFunctionCall:
		v.Status = status
		return v
	case models.ResponseApplyPatchCall:
		v.Status = status
		return v
	case models.ResponseShellCall:
		v.Status = status
		return v
	case models.ResponseLocalShellCall:
		v.Status = status
		return v
	default:
		return item
	}
}