package pricing

import (
	"errors"
	"net/http"

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

type Handler struct {
	service *Service
}

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

type tierResponse struct {
	ID         uuid.UUID `json:"id"`
	ProductID  uuid.UUID `json:"product_id"`
	UnitID     uuid.UUID `json:"unit_id"`
	Quantity   float64   `json:"quantity"`
	PriceCents int64     `json:"price_cents"`
	Position   int       `json:"position"`
}

func toResponse(t *PriceTier) tierResponse {
	return tierResponse{
		ID:         t.ID,
		ProductID:  t.ProductID,
		UnitID:     t.UnitID,
		Quantity:   t.Quantity,
		PriceCents: t.PriceCents,
		Position:   t.Position,
	}
}

func (h *Handler) ListByProduct(c *gin.Context) {
	productID, err := uuid.Parse(c.Param("id"))
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid product id"})
		return
	}
	list, err := h.service.ListByProduct(c.Request.Context(), productID)
	if err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"error": "failed to list price tiers"})
		return
	}
	resp := make([]tierResponse, 0, len(list))
	for _, t := range list {
		resp = append(resp, toResponse(t))
	}
	c.JSON(http.StatusOK, gin.H{"price_tiers": resp})
}

type upsertRequest struct {
	UnitID     uuid.UUID `json:"unit_id" binding:"required"`
	Quantity   float64   `json:"quantity" binding:"required,gt=0"`
	PriceCents int64     `json:"price_cents" binding:"gte=0"`
	Position   int       `json:"position"`
}

func (h *Handler) Create(c *gin.Context) {
	productID, err := uuid.Parse(c.Param("id"))
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid product id"})
		return
	}
	var req upsertRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "validation error", "details": err.Error()})
		return
	}
	t, err := h.service.Create(c.Request.Context(), productID, req.UnitID, req.Quantity, req.PriceCents, req.Position)
	if err != nil {
		if errors.Is(err, ErrInvalidReference) {
			c.JSON(http.StatusBadRequest, gin.H{"error": "product or unit does not exist"})
			return
		}
		c.JSON(http.StatusInternalServerError, gin.H{"error": "failed to create price tier"})
		return
	}
	c.JSON(http.StatusCreated, toResponse(t))
}

func (h *Handler) Update(c *gin.Context) {
	id, err := uuid.Parse(c.Param("tierId"))
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid id"})
		return
	}
	var req upsertRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "validation error", "details": err.Error()})
		return
	}
	t, err := h.service.Update(c.Request.Context(), id, req.UnitID, req.Quantity, req.PriceCents, req.Position)
	if err != nil {
		switch {
		case errors.Is(err, ErrNotFound):
			c.JSON(http.StatusNotFound, gin.H{"error": "price tier not found"})
		case errors.Is(err, ErrInvalidReference):
			c.JSON(http.StatusBadRequest, gin.H{"error": "product or unit does not exist"})
		default:
			c.JSON(http.StatusInternalServerError, gin.H{"error": "failed to update price tier"})
		}
		return
	}
	c.JSON(http.StatusOK, toResponse(t))
}

func (h *Handler) Delete(c *gin.Context) {
	id, err := uuid.Parse(c.Param("tierId"))
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid id"})
		return
	}
	if err := h.service.Delete(c.Request.Context(), id); err != nil {
		if errors.Is(err, ErrNotFound) {
			c.JSON(http.StatusNotFound, gin.H{"error": "price tier not found"})
			return
		}
		c.JSON(http.StatusInternalServerError, gin.H{"error": "failed to delete price tier"})
		return
	}
	c.Status(http.StatusNoContent)
}