package v1

import (
	"encoding/csv"
	"fmt"
	"net/http"
	"time"

	"github.com/gin-gonic/gin"
	"github.com/gochat/gochat/internal/service"
	"github.com/gochat/gochat/pkg/response"
)

// CsatMetricsHandler handles dedicated CSAT metrics and CSV download endpoints.
// Reference: Chatwoot csat_report controller — enterprise metrics dashboard + export
type CsatMetricsHandler struct {
	svc *service.CsatMetricsService
}

// NewCsatMetricsHandler creates a new CsatMetricsHandler.
func NewCsatMetricsHandler(svc *service.CsatMetricsService) *CsatMetricsHandler {
	return &CsatMetricsHandler{svc: svc}
}

// Metrics returns aggregated CSAT metrics (average rating, response rate, trend).
// GET /api/v1/accounts/:account_id/csat_survey_responses/metrics?since=...&until=...
func (h *CsatMetricsHandler) Metrics(c *gin.Context) {
	accountID := getAccountID(c)
	if accountID == 0 {
		response.AbortWithStatusError(c, http.StatusBadRequest, response.ErrBadRequest, "account_id is required")
		return
	}

	since, until := parseSinceUntilQuery(c)

	report, err := h.svc.GetMetrics(c.Request.Context(), accountID, since, until)
	if err != nil {
		handleServiceError(c, err)
		return
	}

	response.OK(c, report)
}

// Download generates a CSV file of CSAT responses and streams it back.
// GET /api/v1/accounts/:account_id/csat_survey_responses/download?since=...&until=...
func (h *CsatMetricsHandler) Download(c *gin.Context) {
	accountID := getAccountID(c)
	if accountID == 0 {
		response.AbortWithStatusError(c, http.StatusBadRequest, response.ErrBadRequest, "account_id is required")
		return
	}

	since, until := parseSinceUntilQuery(c)

	rows, err := h.svc.ExportCSV(c.Request.Context(), accountID, since, until)
	if err != nil {
		handleServiceError(c, err)
		return
	}

	// Set CSV response headers
	filename := fmt.Sprintf("csat_metrics_account_%d.csv", accountID)
	c.Header("Content-Type", "text/csv")
	c.Header("Content-Disposition", fmt.Sprintf("attachment; filename=\"%s\"", filename))

	// Write CSV header + rows directly to the response writer
	writer := csv.NewWriter(c.Writer)

	// CSV header row
	header := []string{"conversation_id", "contact_id", "assigned_agent_id", "rating", "feedback_message", "created_at"}
	if err := writer.Write(header); err != nil {
		response.AbortWithStatusError(c, http.StatusInternalServerError, response.ErrInternal, "failed to write CSV header")
		return
	}

	// CSV data rows
	for _, row := range rows {
		record := []string{
			row.ConversationID,
			row.ContactID,
			row.AssignedAgentID,
			row.Rating,
			row.FeedbackMessage,
			row.CreatedAt,
		}
		if err := writer.Write(record); err != nil {
			response.AbortWithStatusError(c, http.StatusInternalServerError, response.ErrInternal, "failed to write CSV row")
			return
		}
	}

	writer.Flush()
	if err := writer.Error(); err != nil {
		response.AbortWithStatusError(c, http.StatusInternalServerError, response.ErrInternal, "CSV flush error")
		return
	}
}

// parseSinceUntilQuery extracts optional since/until time.Time pointers from query params.
func parseSinceUntilQuery(c *gin.Context) (*time.Time, *time.Time) {
	var since, until *time.Time

	if v := c.Query("since"); v != "" {
		t, err := time.Parse(time.RFC3339, v)
		if err == nil {
			since = &t
		}
	}

	if v := c.Query("until"); v != "" {
		t, err := time.Parse(time.RFC3339, v)
		if err == nil {
			until = &t
		}
	}

	return since, until
}

// RegisterCsatMetricsRoutes registers CSAT metrics routes on the given router group.
// Reference: Chatwoot GET /csat_survey_responses/metrics + /csat_survey_responses/download
func RegisterCsatMetricsRoutes(g *gin.RouterGroup, h *CsatMetricsHandler) {
	responses := g.Group("/csat_survey_responses")
	{
		responses.GET("/metrics", h.Metrics)
		responses.GET("/download", h.Download)
	}
}