package handlers

import (
	"net/http"
	"strconv"
	"time"

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

// AnalyticsHandler handles analytics-related HTTP requests
type AnalyticsHandler struct{}

// NewAnalyticsHandler creates a new analytics handler
func NewAnalyticsHandler() *AnalyticsHandler {
	return &AnalyticsHandler{}
}

// ChurnPrediction represents a churn prediction response
type ChurnPrediction struct {
	ProfileID          string    `json:"profile_id"`
	RiskLevel          string    `json:"risk_level"`
	RiskScore          float64   `json:"risk_score"`
	PredictedChurnDate string    `json:"predicted_churn_date,omitempty"`
	Reasons            []string  `json:"reasons"`
	Recommendations    []string  `json:"recommendations"`
	LastUpdated        time.Time `json:"last_updated"`
}

// ChurnMetrics represents churn metrics
type ChurnMetrics struct {
	Period             string           `json:"period"`
	TotalSubscribers   int64            `json:"total_subscribers"`
	ChurnedSubscribers int64            `json:"churned_subscribers"`
	ChurnRate          float64          `json:"churn_rate_pct"`
	MonthlyChurnRate   float64          `json:"monthly_churn_rate_pct"`
	AnnualChurnRate    float64          `json:"annual_churn_rate_pct"`
	AverageTenureDays  float64          `json:"average_tenure_days"`
	RiskDistribution   map[string]int64 `json:"risk_distribution"`
	GeneratedAt        time.Time        `json:"generated_at"`
}

// PredictChurn predicts churn for a profile
func (h *AnalyticsHandler) PredictChurn(c *gin.Context) {
	var req struct {
		ProfileID string `json:"profile_id" binding:"required"`
	}
	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
		return
	}

	// Simulated churn prediction
	prediction := ChurnPrediction{
		ProfileID:          req.ProfileID,
		RiskLevel:          "medium",
		RiskScore:          45.5,
		PredictedChurnDate: time.Now().AddDate(0, 2, 0).Format("2006-01-02"),
		Reasons: []string{
			"Decreased usage over last 30 days",
			"No recent plan upgrades",
			"Support tickets increased",
		},
		Recommendations: []string{
			"Offer loyalty discount",
			"Proactive customer outreach",
			"Personalized plan recommendation",
		},
		LastUpdated: time.Now(),
	}

	c.JSON(http.StatusOK, prediction)
}

// GetAtRiskCustomers returns customers at risk of churning
func (h *AnalyticsHandler) GetAtRiskCustomers(c *gin.Context) {
	riskLevel := c.DefaultQuery("risk_level", "high")
	limitStr := c.DefaultQuery("limit", "100")
	limit, _ := strconv.Atoi(limitStr)
	if limit > 1000 {
		limit = 1000
	}

	// Simulated at-risk customers
	customers := make([]ChurnPrediction, 0)
	for i := 0; i < min(limit, 10); i++ {
		customers = append(customers, ChurnPrediction{
			ProfileID:          "profile-" + strconv.Itoa(i+1),
			RiskLevel:          riskLevel,
			RiskScore:          70.0 + float64(i)*2,
			PredictedChurnDate: time.Now().AddDate(0, 0, 30+i*7).Format("2006-01-02"),
			Reasons:            []string{"Low engagement", "Billing issues"},
			Recommendations:    []string{"Retention offer", "Account review"},
			LastUpdated:        time.Now(),
		})
	}

	c.JSON(http.StatusOK, customers)
}

// MarketMetrics represents market analytics
type MarketMetrics struct {
	Period          string         `json:"period"`
	TotalMarketSize int64          `json:"total_market_size"`
	OurSubscribers  int64          `json:"our_subscribers"`
	MarketShare     float64        `json:"market_share_pct"`
	GrowthRate      float64        `json:"growth_rate_pct"`
	ByCountry       map[string]any `json:"by_country"`
	GeneratedAt     time.Time      `json:"generated_at"`
}

// GetMarketMetrics returns market penetration metrics
func (h *AnalyticsHandler) GetMarketMetrics(c *gin.Context) {
	period := c.DefaultQuery("period", "monthly")

	metrics := MarketMetrics{
		Period:          period,
		TotalMarketSize: 5500000000, // Global mobile subscribers ~5.5B
		OurSubscribers:  150000,
		MarketShare:     0.0027,
		GrowthRate:      12.5,
		ByCountry: map[string]any{
			"US": map[string]any{
				"market_size": 330000000,
				"our_subs":    45000,
				"penetration": 0.014,
				"growth_rate": 8.5,
			},
			"UK": map[string]any{
				"market_size": 67000000,
				"our_subs":    25000,
				"penetration": 0.037,
				"growth_rate": 15.2,
			},
			"DE": map[string]any{
				"market_size": 83000000,
				"our_subs":    30000,
				"penetration": 0.036,
				"growth_rate": 11.8,
			},
		},
		GeneratedAt: time.Now(),
	}

	c.JSON(http.StatusOK, metrics)
}

// MaintenanceMetrics represents predictive maintenance metrics
type MaintenanceMetrics struct {
	Period                 string    `json:"period"`
	TotalAssets            int64     `json:"total_assets"`
	HealthyAssets          int64     `json:"healthy_assets"`
	AssetsNeedingAttention int64     `json:"assets_needing_attention"`
	Uptime                 float64   `json:"uptime_pct"`
	MeanTimeToFailure      float64   `json:"mean_time_to_failure_hours"`
	MeanTimeToRepair       float64   `json:"mean_time_to_repair_hours"`
	GeneratedAt            time.Time `json:"generated_at"`
}

// PricingMetrics represents pricing optimization metrics
type PricingMetrics struct {
	Period           string    `json:"period"`
	TotalRevenue     float64   `json:"total_revenue"`
	ARPU             float64   `json:"arpu"`
	PriceElasticity  float64   `json:"price_elasticity"`
	CompetitiveIndex float64   `json:"competitive_index"`
	OptimizationROI  float64   `json:"optimization_roi_pct"`
	GeneratedAt      time.Time `json:"generated_at"`
}