package v1

import (
	"encoding/csv"
	"net/http"
	"strconv"
	"strings"
	"time"

	"github.com/gin-gonic/gin"

	"github.com/gochat/gochat/internal/service"
	applogger "github.com/gochat/gochat/pkg/logger"
	"github.com/gochat/gochat/pkg/response"
)

// AnalyticsHandler handles reporting/analytics API endpoints.
// Reference: Chatwoot app/controllers/api/v1/reports_controller.rb
type AnalyticsHandler struct {
	svc *service.AnalyticsService
}

func NewAnalyticsHandler(svc *service.AnalyticsService) *AnalyticsHandler {
	return &AnalyticsHandler{svc: svc}
}

// Index returns metric time-series for the overview charts.
// GET /api/v2/accounts/:account_id/reports?metric=...&since=...&until=...
func (h *AnalyticsHandler) Index(c *gin.Context) {
	accountID, ok := parseAccountID(c)
	if !ok {
		return
	}
	since, until, ok := parseDateRange(c)
	if !ok {
		return
	}
	metric := c.Query("metric")
	if metric == "" {
		response.AbortWithStatusError(c, http.StatusUnprocessableEntity, response.ErrBadRequest, "metric parameter is required")
		return
	}
	id := uint(0)
	if rawID := c.Query("id"); rawID != "" {
		parsed, err := strconv.ParseUint(rawID, 10, 64)
		if err != nil {
			response.AbortWithStatusError(c, http.StatusBadRequest, response.ErrBadRequest, "invalid id")
			return
		}
		id = uint(parsed)
	}
	businessHours := c.Query("business_hours") == "true" || c.Query("business_hours") == "1"
	timezoneOffset, ok := parseReportTimezoneOffset(c)
	if !ok {
		return
	}
	result, err := h.svc.GetTimeseries(c.Request.Context(), accountID, metric, since, until, c.DefaultQuery("type", "account"), id, c.Query("group_by"), timezoneOffset, businessHours)
	if err != nil {
		applogger.L().Errorf("Timeseries report: %v", err)
		response.AbortWithStatusError(c, http.StatusInternalServerError, response.ErrInternal, "failed to generate report")
		return
	}
	c.JSON(http.StatusOK, result)
}

// Drilldown lists the raw records behind one report chart bucket.
// GET /api/v2/accounts/:account_id/reports/drilldown
func (h *AnalyticsHandler) Drilldown(c *gin.Context) {
	accountID, ok := parseAccountID(c)
	if !ok {
		return
	}
	metric := c.Query("metric")
	bucketRaw := c.Query("bucket_timestamp")
	if metric == "" || bucketRaw == "" || c.Query("since") == "" || c.Query("until") == "" {
		c.Status(http.StatusUnprocessableEntity)
		return
	}
	since, until, ok := parseDateRange(c)
	if !ok {
		return
	}
	bucket, err := parseChatwootReportTime(bucketRaw)
	if err != nil {
		c.Status(http.StatusUnprocessableEntity)
		return
	}
	dimensionType := c.DefaultQuery("type", "account")
	if dimensionType != "account" && dimensionType != "inbox" && dimensionType != "agent" && dimensionType != "label" && dimensionType != "team" {
		c.Status(http.StatusUnprocessableEntity)
		return
	}
	id, ok := parseOptionalReportID(c)
	if !ok {
		return
	}
	if dimensionType != "account" && id == 0 {
		c.Status(http.StatusUnprocessableEntity)
		return
	}
	groupBy := c.DefaultQuery("group_by", "day")
	if groupBy != "hour" && groupBy != "day" && groupBy != "week" && groupBy != "month" && groupBy != "year" {
		c.Status(http.StatusUnprocessableEntity)
		return
	}
	offset, ok := parseReportTimezoneOffset(c)
	if !ok {
		return
	}
	page, _ := strconv.Atoi(c.DefaultQuery("page", "1"))
	perPage, _ := strconv.Atoi(c.DefaultQuery("per_page", "25"))
	result, err := h.svc.GetDrilldown(c.Request.Context(), accountID, service.ReportDrilldownParams{Metric: metric, DimensionType: dimensionType, DimensionID: id, GroupBy: groupBy, Since: since, Until: until, BucketTimestamp: bucket, TimezoneOffset: offset, BusinessHours: parseReportBusinessHours(c), Page: page, PerPage: perPage})
	if err != nil {
		if strings.Contains(err.Error(), "unsupported") || strings.Contains(err.Error(), "invalid bucket") {
			c.Status(http.StatusUnprocessableEntity)
			return
		}
		handleServiceError(c, err)
		return
	}
	c.JSON(http.StatusOK, result)
}

// parseAccountID extracts account_id from URL params.
func parseAccountID(c *gin.Context) (uint, bool) {
	id := getAccountID(c)
	if id == 0 {
		response.AbortWithStatusError(c, http.StatusBadRequest, response.ErrBadRequest, "invalid account_id")
		return 0, false
	}
	return id, true
}

// parseDateRange extracts since/unsince from query params.
func parseDateRange(c *gin.Context) (since, until time.Time, ok bool) {
	sinceStr := c.Query("since")
	untilStr := c.Query("until")

	if sinceStr == "" || untilStr == "" {
		response.AbortWithStatusError(c, http.StatusBadRequest, response.ErrBadRequest, "since and until query params are required")
		return time.Time{}, time.Time{}, false
	}

	since, err := parseChatwootReportTime(sinceStr)
	if err != nil {
		response.AbortWithStatusError(c, http.StatusBadRequest, response.ErrBadRequest, "invalid since date format")
		return time.Time{}, time.Time{}, false
	}

	until, err = parseChatwootReportTime(untilStr)
	if err != nil {
		response.AbortWithStatusError(c, http.StatusBadRequest, response.ErrBadRequest, "invalid until date format")
		return time.Time{}, time.Time{}, false
	}

	return since, until, true
}

func parseChatwootReportTime(value string) (time.Time, error) {
	if unixSeconds, err := strconv.ParseInt(value, 10, 64); err == nil {
		return time.Unix(unixSeconds, 0).UTC(), nil
	}

	return time.Parse(time.RFC3339, value)
}

func parseReportBusinessHours(c *gin.Context) bool {
	return c.Query("business_hours") == "true" || c.Query("business_hours") == "1"
}

func parseReportTimezoneOffset(c *gin.Context) (float64, bool) {
	if raw := c.Query("timezone_offset"); raw != "" {
		parsed, err := strconv.ParseFloat(raw, 64)
		if err != nil {
			response.AbortWithStatusError(c, http.StatusBadRequest, response.ErrBadRequest, "invalid timezone_offset")
			return 0, false
		}
		return parsed, true
	}
	return 0, true
}

func parseOptionalReportID(c *gin.Context) (uint, bool) {
	if rawID := c.Query("id"); rawID != "" {
		parsed, err := strconv.ParseUint(rawID, 10, 64)
		if err != nil {
			response.AbortWithStatusError(c, http.StatusBadRequest, response.ErrBadRequest, "invalid id")
			return 0, false
		}
		return uint(parsed), true
	}
	return 0, true
}

func parseConversationTrafficRange(c *gin.Context) (time.Time, time.Time, float64, bool) {
	timezoneOffset, ok := parseReportTimezoneOffset(c)
	if !ok {
		return time.Time{}, time.Time{}, 0, false
	}

	if c.Query("since") != "" || c.Query("until") != "" {
		since, until, ok := parseDateRange(c)
		return since, until, timezoneOffset, ok
	}

	daysBefore := 6
	if raw := c.Query("days_before"); raw != "" {
		parsed, err := strconv.Atoi(raw)
		if err != nil {
			response.AbortWithStatusError(c, http.StatusBadRequest, response.ErrBadRequest, "invalid days_before")
			return time.Time{}, time.Time{}, 0, false
		}
		daysBefore = parsed
	}

	loc := fixedOffsetLocation(timezoneOffset)
	now := time.Now().In(loc)
	untilLocal := time.Date(now.Year(), now.Month(), now.Day(), 0, 0, 0, 0, loc)
	sinceLocal := untilLocal.AddDate(0, 0, -daysBefore)
	return sinceLocal.UTC(), untilLocal.UTC(), timezoneOffset, true
}

func fixedOffsetLocation(offsetHours float64) *time.Location {
	seconds := int(offsetHours * 3600)
	return time.FixedZone(reportTimezoneName(offsetHours), seconds)
}

func reportTimezoneName(offsetHours float64) string {
	if offsetHours == 0 {
		return "UTC"
	}
	sign := "+"
	if offsetHours < 0 {
		sign = "-"
		offsetHours = -offsetHours
	}
	totalMinutes := int(offsetHours*60 + 0.5)
	return "UTC" + sign + twoDigit(totalMinutes/60) + ":" + twoDigit(totalMinutes%60)
}

func twoDigit(value int) string {
	if value < 10 {
		return "0" + strconv.Itoa(value)
	}
	return strconv.Itoa(value)
}

func writeReportCSV(c *gin.Context, filename string, since, until time.Time, headers []string, rows [][]string) {
	c.Header("Content-Type", "text/csv")
	c.Header("Content-Disposition", "attachment; filename="+filename+".csv")
	writer := csv.NewWriter(c.Writer)
	_ = writer.Write([]string{"Reporting period " + since.Format("2006-01-02") + " to " + until.Format("2006-01-02")})
	_ = writer.Write([]string{})
	_ = writer.Write(headers)
	for _, row := range rows {
		_ = writer.Write(row)
	}
	writer.Flush()
}

func writeConversationTrafficCSV(c *gin.Context, timezoneOffset float64, rows [][]string) {
	c.Header("Content-Type", "text/csv")
	c.Header("Content-Disposition", "attachment; filename=conversation_traffic_reports.csv")
	writer := csv.NewWriter(c.Writer)
	_ = writer.Write([]string{"Timezone", reportTimezoneName(timezoneOffset)})
	_ = writer.Write([]string{})
	for _, row := range rows {
		_ = writer.Write(row)
	}
	writer.Flush()
}

// Summary returns account-level aggregated metrics.
// GET /api/v1/accounts/:account_id/reports/summary
func (h *AnalyticsHandler) Summary(c *gin.Context) {
	accountID, ok := parseAccountID(c)
	if !ok {
		return
	}
	since, until, ok := parseDateRange(c)
	if !ok {
		return
	}
	if _, ok := parseReportTimezoneOffset(c); !ok {
		return
	}
	id, ok := parseOptionalReportID(c)
	if !ok {
		return
	}

	result, err := h.svc.GetReportSummary(c.Request.Context(), accountID, since, until, c.DefaultQuery("type", "account"), id, parseReportBusinessHours(c))
	if err != nil {
		applogger.L().Errorf("Summary report: %v", err)
		response.AbortWithStatusError(c, http.StatusInternalServerError, response.ErrInternal, "failed to generate summary report")
		return
	}

	c.JSON(http.StatusOK, result)
}

// AgentMetrics returns metrics grouped by agent.
// GET /api/v1/accounts/:account_id/reports/agents
func (h *AnalyticsHandler) AgentMetrics(c *gin.Context) {
	accountID, ok := parseAccountID(c)
	if !ok {
		return
	}
	since, until, ok := parseDateRange(c)
	if !ok {
		return
	}

	result, err := h.svc.GetAgentReportCSVRows(c.Request.Context(), accountID, since, until, parseReportBusinessHours(c))
	if err != nil {
		applogger.L().Errorf("Agent metrics report: %v", err)
		response.AbortWithStatusError(c, http.StatusInternalServerError, response.ErrInternal, "failed to generate agent metrics")
		return
	}

	writeReportCSV(c, "agents_report", since, until, []string{
		"Agent name",
		"Assigned conversations",
		"Avg first response time",
		"Avg resolution time",
		"Avg customer waiting time",
		"Resolution Count",
	}, result)
}

// InboxMetrics returns metrics grouped by inbox.
// GET /api/v1/accounts/:account_id/reports/inboxes
func (h *AnalyticsHandler) InboxMetrics(c *gin.Context) {
	accountID, ok := parseAccountID(c)
	if !ok {
		return
	}
	since, until, ok := parseDateRange(c)
	if !ok {
		return
	}

	result, err := h.svc.GetInboxReportCSVRows(c.Request.Context(), accountID, since, until, parseReportBusinessHours(c))
	if err != nil {
		applogger.L().Errorf("Inbox metrics report: %v", err)
		response.AbortWithStatusError(c, http.StatusInternalServerError, response.ErrInternal, "failed to generate inbox metrics")
		return
	}

	writeReportCSV(c, "inboxes_report", since, until, []string{
		"Inbox name",
		"Inbox type",
		"No. of conversations",
		"Avg first response time",
		"Avg resolution time",
	}, result)
}

// LabelMetrics returns metrics grouped by label.
// GET /api/v1/accounts/:account_id/reports/labels
func (h *AnalyticsHandler) LabelMetrics(c *gin.Context) {
	accountID, ok := parseAccountID(c)
	if !ok {
		return
	}
	since, until, ok := parseDateRange(c)
	if !ok {
		return
	}

	result, err := h.svc.GetLabelReportCSVRows(c.Request.Context(), accountID, since, until, parseReportBusinessHours(c))
	if err != nil {
		applogger.L().Errorf("Label metrics report: %v", err)
		response.AbortWithStatusError(c, http.StatusInternalServerError, response.ErrInternal, "failed to generate label metrics")
		return
	}

	writeReportCSV(c, "labels_report", since, until, []string{
		"Label",
		"No. of conversations",
		"Avg first response time",
		"Avg resolution time",
		"Avg reply time",
		"Resolution Count",
	}, result)
}

// TeamMetrics returns metrics grouped by team.
// GET /api/v1/accounts/:account_id/reports/teams
func (h *AnalyticsHandler) TeamMetrics(c *gin.Context) {
	accountID, ok := parseAccountID(c)
	if !ok {
		return
	}
	since, until, ok := parseDateRange(c)
	if !ok {
		return
	}

	result, err := h.svc.GetTeamReportCSVRows(c.Request.Context(), accountID, since, until, parseReportBusinessHours(c))
	if err != nil {
		applogger.L().Errorf("Team metrics report: %v", err)
		response.AbortWithStatusError(c, http.StatusInternalServerError, response.ErrInternal, "failed to generate team metrics")
		return
	}

	writeReportCSV(c, "teams_report", since, until, []string{
		"Team name",
		"Conversations count",
		"Avg first response time",
		"Avg resolution time",
		"Avg customer waiting time",
		"Resolution Count",
	}, result)
}

// ConversationTraffic returns daily conversation traffic time-series.
// GET /api/v1/accounts/:account_id/reports/conversation_traffic
func (h *AnalyticsHandler) ConversationTraffic(c *gin.Context) {
	accountID, ok := parseAccountID(c)
	if !ok {
		return
	}
	since, until, timezoneOffset, ok := parseConversationTrafficRange(c)
	if !ok {
		return
	}

	result, err := h.svc.GetConversationTrafficCSVRows(c.Request.Context(), accountID, since, until, timezoneOffset)
	if err != nil {
		applogger.L().Errorf("Conversation traffic report: %v", err)
		response.AbortWithStatusError(c, http.StatusInternalServerError, response.ErrInternal, "failed to generate conversation traffic")
		return
	}

	writeConversationTrafficCSV(c, timezoneOffset, result)
}

// BotSummary returns bot-level summary metrics.
// GET /api/v1/accounts/:account_id/reports/bot_summary
// Reference: Chatwoot reports#bot_summary
func (h *AnalyticsHandler) BotSummary(c *gin.Context) {
	accountID, ok := parseAccountID(c)
	if !ok {
		return
	}
	since, until, ok := parseDateRange(c)
	if !ok {
		return
	}
	id, ok := parseOptionalReportID(c)
	if !ok {
		return
	}

	result, err := h.svc.GetBotSummary(c.Request.Context(), accountID, since, until, c.DefaultQuery("type", "account"), id)
	if err != nil {
		applogger.L().Errorf("Bot summary report: %v", err)
		response.AbortWithStatusError(c, http.StatusInternalServerError, response.ErrInternal, "failed to generate bot summary")
		return
	}

	c.JSON(http.StatusOK, result)
}

// Conversations returns conversation metrics filtered by type.
// GET /api/v1/accounts/:account_id/reports/conversations
// Reference: Chatwoot reports#conversations — requires params[:type], returns 422 if missing
func (h *AnalyticsHandler) Conversations(c *gin.Context) {
	accountID, ok := parseAccountID(c)
	if !ok {
		return
	}

	reportType := c.Query("type")
	if reportType == "" {
		// Reference: Chatwoot returns head :unprocessable_entity if type is blank
		c.Status(http.StatusUnprocessableEntity)
		return
	}
	page := 1
	if rawPage := c.Query("page"); rawPage != "" {
		if parsed, err := strconv.Atoi(rawPage); err == nil && parsed > 0 {
			page = parsed
		}
	}

	result, err := h.svc.GetConversationsByType(c.Request.Context(), accountID, reportType, page)
	if err != nil {
		applogger.L().Errorf("Conversations report: %v", err)
		response.AbortWithStatusError(c, http.StatusInternalServerError, response.ErrInternal, "failed to generate conversations report")
		return
	}

	c.JSON(http.StatusOK, result)
}

// ConversationsSummary returns conversation summary report.
// GET /api/v1/accounts/:account_id/reports/conversations_summary
// Reference: Chatwoot reports#conversations_summary
func (h *AnalyticsHandler) ConversationsSummary(c *gin.Context) {
	accountID, ok := parseAccountID(c)
	if !ok {
		return
	}
	since, until, ok := parseDateRange(c)
	if !ok {
		return
	}

	result, err := h.svc.GetConversationsSummaryCSVRows(c.Request.Context(), accountID, since, until, parseReportBusinessHours(c))
	if err != nil {
		applogger.L().Errorf("Conversations summary report: %v", err)
		response.AbortWithStatusError(c, http.StatusInternalServerError, response.ErrInternal, "failed to generate conversations summary")
		return
	}

	writeReportCSV(c, "conversations_summary_report", since, until, []string{
		"Conversations",
		"Messages received",
		"Messages sent",
		"Avg first response time",
		"Avg resolution time",
		"Resolution count",
		"Avg customer waiting time",
	}, result)
}

// BotMetrics returns bot metrics.
// GET /api/v1/accounts/:account_id/reports/bot_metrics
// Reference: Chatwoot reports#bot_metrics
func (h *AnalyticsHandler) BotMetrics(c *gin.Context) {
	accountID, ok := parseAccountID(c)
	if !ok {
		return
	}
	since, until, ok := parseDateRange(c)
	if !ok {
		return
	}

	result, err := h.svc.GetBotMetrics(c.Request.Context(), accountID, since, until)
	if err != nil {
		applogger.L().Errorf("Bot metrics report: %v", err)
		response.AbortWithStatusError(c, http.StatusInternalServerError, response.ErrInternal, "failed to generate bot metrics")
		return
	}

	c.JSON(http.StatusOK, result)
}

// InboxLabelMatrix returns inbox-label matrix data.
// GET /api/v1/accounts/:account_id/reports/inbox_label_matrix
// Reference: Chatwoot reports#inbox_label_matrix
func (h *AnalyticsHandler) InboxLabelMatrix(c *gin.Context) {
	accountID, ok := parseAccountID(c)
	if !ok {
		return
	}
	filter, ok := parseInboxLabelMatrixFilter(c)
	if !ok {
		return
	}

	result, err := h.svc.GetInboxLabelMatrix(c.Request.Context(), accountID, filter)
	if err != nil {
		applogger.L().Errorf("Inbox label matrix report: %v", err)
		response.AbortWithStatusError(c, http.StatusInternalServerError, response.ErrInternal, "failed to generate inbox label matrix")
		return
	}

	c.JSON(http.StatusOK, result)
}

func parseInboxLabelMatrixFilter(c *gin.Context) (service.InboxLabelMatrixFilter, bool) {
	filter := service.InboxLabelMatrixFilter{
		InboxIDs: parseReportUintList(c, "inbox_ids"),
		LabelIDs: parseReportUintList(c, "label_ids"),
	}
	sinceRaw := c.Query("since")
	untilRaw := c.Query("until")
	if sinceRaw == "" || untilRaw == "" {
		return filter, true
	}
	since, err := parseChatwootReportTime(sinceRaw)
	if err != nil {
		response.AbortWithStatusError(c, http.StatusBadRequest, response.ErrBadRequest, "invalid since date format")
		return service.InboxLabelMatrixFilter{}, false
	}
	until, err := parseChatwootReportTime(untilRaw)
	if err != nil {
		response.AbortWithStatusError(c, http.StatusBadRequest, response.ErrBadRequest, "invalid until date format")
		return service.InboxLabelMatrixFilter{}, false
	}
	filter.Since = since
	filter.Until = until
	return filter, true
}

func parseReportUintList(c *gin.Context, key string) []uint {
	values := append([]string{}, c.QueryArray(key)...)
	values = append(values, c.QueryArray(key+"[]")...)
	ids := make([]uint, 0, len(values))
	for _, value := range values {
		for _, part := range strings.Split(value, ",") {
			part = strings.TrimSpace(part)
			if part == "" {
				continue
			}
			parsed, err := strconv.ParseUint(part, 10, 64)
			if err == nil && parsed > 0 {
				ids = append(ids, uint(parsed))
			}
		}
	}
	return ids
}

// FirstResponseTimeDistribution returns first response time distribution.
// GET /api/v1/accounts/:account_id/reports/first_response_time_distribution
// Reference: Chatwoot reports#first_response_time_distribution
func (h *AnalyticsHandler) FirstResponseTimeDistribution(c *gin.Context) {
	accountID, ok := parseAccountID(c)
	if !ok {
		return
	}
	since, until, ok := parseOptionalReportDateRange(c)
	if !ok {
		return
	}

	result, err := h.svc.GetFirstResponseTimeDistribution(c.Request.Context(), accountID, since, until)
	if err != nil {
		applogger.L().Errorf("First response time distribution report: %v", err)
		response.AbortWithStatusError(c, http.StatusInternalServerError, response.ErrInternal, "failed to generate first response time distribution")
		return
	}

	c.JSON(http.StatusOK, result)
}

func parseOptionalReportDateRange(c *gin.Context) (since, until time.Time, ok bool) {
	sinceRaw := c.Query("since")
	untilRaw := c.Query("until")
	if sinceRaw == "" || untilRaw == "" {
		return time.Time{}, time.Time{}, true
	}
	since, err := parseChatwootReportTime(sinceRaw)
	if err != nil {
		response.AbortWithStatusError(c, http.StatusBadRequest, response.ErrBadRequest, "invalid since date format")
		return time.Time{}, time.Time{}, false
	}
	until, err = parseChatwootReportTime(untilRaw)
	if err != nil {
		response.AbortWithStatusError(c, http.StatusBadRequest, response.ErrBadRequest, "invalid until date format")
		return time.Time{}, time.Time{}, false
	}
	return since, until, true
}

// OutgoingMessagesCount returns outgoing message count metrics.
// GET /api/v1/accounts/:account_id/reports/outgoing_messages_count
// Reference: Chatwoot reports#outgoing_messages_count
func (h *AnalyticsHandler) OutgoingMessagesCount(c *gin.Context) {
	accountID, ok := parseAccountID(c)
	if !ok {
		return
	}
	since, until, ok := parseDateRange(c)
	if !ok {
		return
	}
	groupBy := c.Query("group_by")
	if groupBy != "agent" && groupBy != "team" && groupBy != "inbox" && groupBy != "label" {
		c.Status(http.StatusUnprocessableEntity)
		return
	}

	result, err := h.svc.GetOutgoingMessagesCountGrouped(c.Request.Context(), accountID, since, until, groupBy)
	if err != nil {
		applogger.L().Errorf("Outgoing messages count report: %v", err)
		response.AbortWithStatusError(c, http.StatusInternalServerError, response.ErrInternal, "failed to generate outgoing messages count")
		return
	}

	c.JSON(http.StatusOK, result)
}