package orders

import (
	"errors"
	"net/http"

	"github.com/gin-gonic/gin"
	"github.com/google/uuid"

	"backend/internal/modules/pricing"
	"backend/internal/modules/products"
)

type Handler struct {
	service *Service
}

func NewHandler(service *Service) *Handler {
	return &Handler{service: service}
}

type itemRequest struct {
	ProductID   uuid.UUID `json:"product_id" binding:"required"`
	PriceTierID uuid.UUID `json:"price_tier_id" binding:"required"`
	Multiplier  int64     `json:"multiplier" binding:"required,gte=1"`
}

type createRequest struct {
	CustomerName  string        `json:"customer_name" binding:"required"`
	CustomerEmail string        `json:"customer_email" binding:"required,email"`
	CustomerPhone string        `json:"customer_phone"`
	Notes         string        `json:"notes"`
	Items         []itemRequest `json:"items" binding:"required,min=1,dive"`
}

type orderItemResponse struct {
	ProductID      *uuid.UUID `json:"product_id,omitempty"`
	ProductName    string     `json:"product_name"`
	UnitSymbol     string     `json:"unit_symbol"`
	TierQuantity   float64    `json:"tier_quantity"`
	Multiplier     int64      `json:"multiplier"`
	UnitPriceCents int64      `json:"unit_price_cents"`
	TotalCents     int64      `json:"total_cents"`
}

type orderResponse struct {
	ID            uuid.UUID           `json:"id"`
	CustomerName  string              `json:"customer_name"`
	CustomerEmail string              `json:"customer_email"`
	CustomerPhone string              `json:"customer_phone"`
	Status        string              `json:"status"`
	TotalCents    int64               `json:"total_cents"`
	Notes         string              `json:"notes"`
	Items         []orderItemResponse `json:"items,omitempty"`
}

func toResponse(order *Order, items []*OrderItem) orderResponse {
	resp := orderResponse{
		ID:            order.ID,
		CustomerName:  order.CustomerName,
		CustomerEmail: order.CustomerEmail,
		CustomerPhone: order.CustomerPhone,
		Status:        order.Status,
		TotalCents:    order.TotalCents,
		Notes:         order.Notes,
	}
	for _, item := range items {
		resp.Items = append(resp.Items, orderItemResponse{
			ProductID:      item.ProductID,
			ProductName:    item.ProductName,
			UnitSymbol:     item.UnitSymbol,
			TierQuantity:   item.TierQuantity,
			Multiplier:     item.Multiplier,
			UnitPriceCents: item.UnitPriceCents,
			TotalCents:     item.TotalCents,
		})
	}
	return resp
}

// Create is public: a visitor (connected or not, per spec section 17) can
// place an order without an account.
func (h *Handler) Create(c *gin.Context) {
	var req createRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "validation error", "details": err.Error()})
		return
	}

	items := make([]ItemInput, 0, len(req.Items))
	for _, item := range req.Items {
		items = append(items, ItemInput{
			ProductID:   item.ProductID,
			PriceTierID: item.PriceTierID,
			Multiplier:  item.Multiplier,
		})
	}

	order, orderItems, err := h.service.Create(c.Request.Context(), CreateInput{
		CustomerName:  req.CustomerName,
		CustomerEmail: req.CustomerEmail,
		CustomerPhone: req.CustomerPhone,
		Notes:         req.Notes,
		Items:         items,
	})
	if err != nil {
		h.respondCreateError(c, err)
		return
	}
	c.JSON(http.StatusCreated, toResponse(order, orderItems))
}

func (h *Handler) respondCreateError(c *gin.Context, err error) {
	switch {
	case errors.Is(err, ErrEmptyOrder), errors.Is(err, ErrProductMismatch):
		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
	case errors.Is(err, pricing.ErrNotFound):
		c.JSON(http.StatusBadRequest, gin.H{"error": "unknown price tier"})
	case errors.Is(err, products.ErrNotFound):
		c.JSON(http.StatusBadRequest, gin.H{"error": "unknown product"})
	default:
		c.JSON(http.StatusInternalServerError, gin.H{"error": "failed to create order"})
	}
}

func (h *Handler) ListAdmin(c *gin.Context) {
	list, err := h.service.List(c.Request.Context(), c.Query("status"))
	if err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"error": "failed to list orders"})
		return
	}
	resp := make([]orderResponse, 0, len(list))
	for _, order := range list {
		resp = append(resp, toResponse(order, nil))
	}
	c.JSON(http.StatusOK, gin.H{"orders": resp})
}

func (h *Handler) GetAdmin(c *gin.Context) {
	id, err := uuid.Parse(c.Param("id"))
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid id"})
		return
	}
	order, items, err := h.service.Get(c.Request.Context(), id)
	if err != nil {
		if errors.Is(err, ErrNotFound) {
			c.JSON(http.StatusNotFound, gin.H{"error": "order not found"})
			return
		}
		c.JSON(http.StatusInternalServerError, gin.H{"error": "failed to load order"})
		return
	}
	c.JSON(http.StatusOK, toResponse(order, items))
}

type updateStatusRequest struct {
	Status string `json:"status" binding:"required"`
}

func (h *Handler) UpdateStatus(c *gin.Context) {
	id, err := uuid.Parse(c.Param("id"))
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid id"})
		return
	}
	var req updateStatusRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "validation error", "details": err.Error()})
		return
	}
	order, err := h.service.UpdateStatus(c.Request.Context(), id, req.Status)
	if err != nil {
		switch {
		case errors.Is(err, ErrNotFound):
			c.JSON(http.StatusNotFound, gin.H{"error": "order not found"})
		case errors.Is(err, ErrInvalidStatus):
			c.JSON(http.StatusBadRequest, gin.H{"error": "invalid status"})
		default:
			c.JSON(http.StatusInternalServerError, gin.H{"error": "failed to update order status"})
		}
		return
	}
	c.JSON(http.StatusOK, toResponse(order, nil))
}