package handlers

import (
	"errors"
	"fmt"
	"strconv"
	"strings"
	"time"

	"Yimaru-Backend/internal/domain"
	"Yimaru-Backend/internal/services/chapa"

	"github.com/gofiber/fiber/v2"
)

type adminPaymentRes struct {
	ID             int64   `json:"id"`
	UserID         int64   `json:"user_id"`
	PlanID         *int64  `json:"plan_id,omitempty"`
	SubscriptionID *int64  `json:"subscription_id,omitempty"`
	SessionID      *string `json:"session_id,omitempty"`
	TransactionID  *string `json:"transaction_id,omitempty"`
	Nonce          string  `json:"nonce"`
	Amount         float64 `json:"amount"`
	Currency       string  `json:"currency"`
	PaymentMethod  *string `json:"payment_method,omitempty"`
	Status         string  `json:"status"`
	PaymentURL     *string `json:"payment_url,omitempty"`
	PlanName       *string `json:"plan_name,omitempty"`
	PlanCategory   *string `json:"plan_category,omitempty"`
	UserEmail      *string `json:"user_email,omitempty"`
	UserFirstName  *string `json:"user_first_name,omitempty"`
	UserLastName   *string `json:"user_last_name,omitempty"`
	PaidAt         *string `json:"paid_at,omitempty"`
	ExpiresAt      *string `json:"expires_at,omitempty"`
	CreatedAt      string  `json:"created_at"`
	UpdatedAt      *string `json:"updated_at,omitempty"`
}

type listAdminPaymentsRes struct {
	Payments   []adminPaymentRes `json:"payments"`
	TotalCount int64             `json:"total_count"`
	Limit      int32             `json:"limit"`
	Offset     int32             `json:"offset"`
}

// ListAdminPayments godoc
// @Summary List all payments (admin)
// @Description Returns paginated payments across Chapa and ArifPay with optional filters
// @Tags payments
// @Produce json
// @Param user_id query int false "Filter by learner user ID"
// @Param plan_id query int false "Filter by subscription plan ID"
// @Param subscription_id query int false "Filter by user subscription ID"
// @Param status query string false "Payment status (PENDING, PROCESSING, SUCCESS, FAILED, CANCELLED, EXPIRED)"
// @Param provider query string false "Payment provider (CHAPA, ARIFPAY)"
// @Param payment_method query string false "Alias for provider"
// @Param currency query string false "Currency code (e.g. ETB)"
// @Param plan_category query string false "Plan category (LEARN_ENGLISH, IELTS, DUOLINGO)"
// @Param reference query string false "Search session_id, nonce, or transaction_id"
// @Param created_from query string false "Created at from (RFC3339 or YYYY-MM-DD)"
// @Param created_to query string false "Created at to (exclusive, RFC3339 or YYYY-MM-DD)"
// @Param paid_from query string false "Paid at from (RFC3339 or YYYY-MM-DD)"
// @Param paid_to query string false "Paid at to (exclusive, RFC3339 or YYYY-MM-DD)"
// @Param min_amount query number false "Minimum amount"
// @Param max_amount query number false "Maximum amount"
// @Param limit query int false "Page size" default(20)
// @Param offset query int false "Page offset" default(0)
// @Success 200 {object} domain.Response
// @Failure 400 {object} domain.ErrorResponse
// @Router /api/v1/admin/payments [get]
func (h *Handler) ListAdminPayments(c *fiber.Ctx) error {
	filter, err := parsePaymentListFilter(c)
	if err != nil {
		return c.Status(fiber.StatusBadRequest).JSON(domain.ErrorResponse{
			Message: "Invalid query parameters",
			Error:   err.Error(),
		})
	}

	page, err := h.chapaSvc.ListPaymentsAdmin(c.Context(), filter)
	if err != nil {
		return c.Status(fiber.StatusInternalServerError).JSON(domain.ErrorResponse{
			Message: "Failed to list payments",
			Error:   err.Error(),
		})
	}

	out := make([]adminPaymentRes, len(page.Items))
	for i := range page.Items {
		out[i] = adminPaymentToRes(&page.Items[i])
	}

	return c.JSON(domain.Response{
		Message: "Payments retrieved successfully",
		Data: listAdminPaymentsRes{
			Payments:   out,
			TotalCount: page.Total,
			Limit:      page.Limit,
			Offset:     page.Offset,
		},
	})
}

// GetAdminPayment godoc
// @Summary Get payment by ID (admin)
// @Description Returns any payment record by ID without learner ownership restriction
// @Tags payments
// @Produce json
// @Param id path int true "Payment ID"
// @Success 200 {object} domain.Response
// @Failure 404 {object} domain.ErrorResponse
// @Router /api/v1/admin/payments/{id} [get]
func (h *Handler) GetAdminPayment(c *fiber.Ctx) error {
	id, err := strconv.ParseInt(c.Params("id"), 10, 64)
	if err != nil {
		return c.Status(fiber.StatusBadRequest).JSON(domain.ErrorResponse{
			Message: "Invalid payment ID",
		})
	}

	payment, err := h.chapaSvc.GetPaymentAdminByID(c.Context(), id)
	if err != nil {
		if errors.Is(err, chapa.ErrPaymentNotFound) {
			return c.Status(fiber.StatusNotFound).JSON(domain.ErrorResponse{
				Message: "Payment not found",
			})
		}
		return c.Status(fiber.StatusInternalServerError).JSON(domain.ErrorResponse{
			Message: "Failed to get payment",
			Error:   err.Error(),
		})
	}

	return c.JSON(domain.Response{
		Message: "Payment retrieved successfully",
		Data:    adminPaymentToRes(payment),
	})
}

func parsePaymentListFilter(c *fiber.Ctx) (domain.PaymentListFilter, error) {
	limit, err := strconv.Atoi(c.Query("limit", "20"))
	if err != nil || limit < 1 {
		return domain.PaymentListFilter{}, fmt.Errorf("invalid limit")
	}
	if limit > 100 {
		limit = 100
	}
	offset, err := strconv.Atoi(c.Query("offset", "0"))
	if err != nil || offset < 0 {
		return domain.PaymentListFilter{}, fmt.Errorf("invalid offset")
	}

	filter := domain.PaymentListFilter{
		Limit:  int32(limit),
		Offset: int32(offset),
	}

	if v := strings.TrimSpace(c.Query("user_id")); v != "" {
		id, err := strconv.ParseInt(v, 10, 64)
		if err != nil {
			return domain.PaymentListFilter{}, fmt.Errorf("invalid user_id")
		}
		filter.UserID = &id
	}
	if v := strings.TrimSpace(c.Query("plan_id")); v != "" {
		id, err := strconv.ParseInt(v, 10, 64)
		if err != nil {
			return domain.PaymentListFilter{}, fmt.Errorf("invalid plan_id")
		}
		filter.PlanID = &id
	}
	if v := strings.TrimSpace(c.Query("subscription_id")); v != "" {
		id, err := strconv.ParseInt(v, 10, 64)
		if err != nil {
			return domain.PaymentListFilter{}, fmt.Errorf("invalid subscription_id")
		}
		filter.SubscriptionID = &id
	}
	if v := strings.TrimSpace(c.Query("status")); v != "" {
		status := strings.ToUpper(v)
		if !isValidPaymentStatus(status) {
			return domain.PaymentListFilter{}, fmt.Errorf("invalid status")
		}
		filter.Status = &status
	}
	provider := firstNonEmpty(strings.TrimSpace(c.Query("provider")), strings.TrimSpace(c.Query("payment_method")))
	if provider != "" {
		p, err := domain.ParsePaymentProvider(provider)
		if err != nil {
			return domain.PaymentListFilter{}, err
		}
		method := string(p)
		filter.PaymentMethod = &method
	}
	if v := strings.TrimSpace(c.Query("currency")); v != "" {
		cur := strings.ToUpper(v)
		filter.Currency = &cur
	}
	if v := strings.TrimSpace(c.Query("plan_category")); v != "" {
		cat := strings.ToUpper(v)
		if cat != string(domain.SubscriptionCategoryLearnEnglish) &&
			cat != string(domain.SubscriptionCategoryIELTS) &&
			cat != string(domain.SubscriptionCategoryDuolingo) {
			return domain.PaymentListFilter{}, fmt.Errorf("invalid plan_category")
		}
		filter.PlanCategory = &cat
	}
	if v := strings.TrimSpace(c.Query("reference")); v != "" {
		filter.Reference = &v
	}

	for _, pair := range []struct {
		q    string
		dest **time.Time
	}{
		{"created_from", &filter.CreatedFrom},
		{"created_to", &filter.CreatedTo},
		{"paid_from", &filter.PaidFrom},
		{"paid_to", &filter.PaidTo},
	} {
		if v := strings.TrimSpace(c.Query(pair.q)); v != "" {
			t, err := parseQueryTime(v)
			if err != nil {
				return domain.PaymentListFilter{}, fmt.Errorf("invalid %s", pair.q)
			}
			*pair.dest = &t
		}
	}

	if v := strings.TrimSpace(c.Query("min_amount")); v != "" {
		amount, err := strconv.ParseFloat(v, 64)
		if err != nil {
			return domain.PaymentListFilter{}, fmt.Errorf("invalid min_amount")
		}
		filter.MinAmount = &amount
	}
	if v := strings.TrimSpace(c.Query("max_amount")); v != "" {
		amount, err := strconv.ParseFloat(v, 64)
		if err != nil {
			return domain.PaymentListFilter{}, fmt.Errorf("invalid max_amount")
		}
		filter.MaxAmount = &amount
	}

	return filter, nil
}

func isValidPaymentStatus(status string) bool {
	switch status {
	case string(domain.PaymentStatusPending),
		string(domain.PaymentStatusProcessing),
		string(domain.PaymentStatusSuccess),
		string(domain.PaymentStatusFailed),
		string(domain.PaymentStatusCancelled),
		string(domain.PaymentStatusExpired):
		return true
	default:
		return false
	}
}

func parseQueryTime(raw string) (time.Time, error) {
	if t, err := time.Parse(time.RFC3339, raw); err == nil {
		return t.UTC(), nil
	}
	if t, err := time.Parse("2006-01-02", raw); err == nil {
		return t.UTC(), nil
	}
	return time.Time{}, fmt.Errorf("unsupported time format")
}

func adminPaymentToRes(p *domain.Payment) adminPaymentRes {
	res := adminPaymentRes{
		ID:             p.ID,
		UserID:         p.UserID,
		PlanID:         p.PlanID,
		SubscriptionID: p.SubscriptionID,
		SessionID:      p.SessionID,
		TransactionID:  p.TransactionID,
		Nonce:          p.Nonce,
		Amount:         p.Amount,
		Currency:       p.Currency,
		PaymentMethod:  p.PaymentMethod,
		Status:         p.Status,
		PaymentURL:     p.PaymentURL,
		PlanName:       p.PlanName,
		PlanCategory:   p.PlanCategory,
		UserEmail:      p.UserEmail,
		UserFirstName:  p.UserFirstName,
		UserLastName:   p.UserLastName,
		CreatedAt:      p.CreatedAt.Format(time.RFC3339),
	}
	if p.PaidAt != nil {
		t := p.PaidAt.Format(time.RFC3339)
		res.PaidAt = &t
	}
	if p.ExpiresAt != nil {
		t := p.ExpiresAt.Format(time.RFC3339)
		res.ExpiresAt = &t
	}
	if p.UpdatedAt != nil {
		t := p.UpdatedAt.Format(time.RFC3339)
		res.UpdatedAt = &t
	}
	return res
}