package units

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 unitResponse struct {
	ID     uuid.UUID `json:"id"`
	Name   string    `json:"name"`
	Symbol string    `json:"symbol"`
}

func toResponse(u *Unit) unitResponse {
	return unitResponse{ID: u.ID, Name: u.Name, Symbol: u.Symbol}
}

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

type upsertRequest struct {
	Name   string `json:"name" binding:"required"`
	Symbol string `json:"symbol" binding:"required"`
}

func (h *Handler) Create(c *gin.Context) {
	var req upsertRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "validation error", "details": err.Error()})
		return
	}
	u, err := h.service.Create(c.Request.Context(), req.Name, req.Symbol)
	if err != nil {
		if errors.Is(err, ErrSymbolTaken) {
			c.JSON(http.StatusConflict, gin.H{"error": "symbol already in use"})
			return
		}
		c.JSON(http.StatusInternalServerError, gin.H{"error": "failed to create unit"})
		return
	}
	c.JSON(http.StatusCreated, toResponse(u))
}

func (h *Handler) Update(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 upsertRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "validation error", "details": err.Error()})
		return
	}
	u, err := h.service.Update(c.Request.Context(), id, req.Name, req.Symbol)
	if err != nil {
		switch {
		case errors.Is(err, ErrNotFound):
			c.JSON(http.StatusNotFound, gin.H{"error": "unit not found"})
		case errors.Is(err, ErrSymbolTaken):
			c.JSON(http.StatusConflict, gin.H{"error": "symbol already in use"})
		default:
			c.JSON(http.StatusInternalServerError, gin.H{"error": "failed to update unit"})
		}
		return
	}
	c.JSON(http.StatusOK, toResponse(u))
}

func (h *Handler) Delete(c *gin.Context) {
	id, err := uuid.Parse(c.Param("id"))
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid id"})
		return
	}
	if err := h.service.Delete(c.Request.Context(), id); err != nil {
		switch {
		case errors.Is(err, ErrNotFound):
			c.JSON(http.StatusNotFound, gin.H{"error": "unit not found"})
		case errors.Is(err, ErrInUse):
			c.JSON(http.StatusConflict, gin.H{"error": "unit is used by existing price tiers"})
		default:
			c.JSON(http.StatusInternalServerError, gin.H{"error": "failed to delete unit"})
		}
		return
	}
	c.Status(http.StatusNoContent)
}