package handler

import (
	"io"
	"strconv"

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

	"apskel-pos-be/internal/appcontext"
	"apskel-pos-be/internal/constants"
	"apskel-pos-be/internal/contract"
	"apskel-pos-be/internal/logger"
	"apskel-pos-be/internal/service"
	"apskel-pos-be/internal/util"
)

// loyaltySettingsBodyLimit caps a settings body; a real one is well under 2 KB.
const loyaltySettingsBodyLimit = 64 << 10

// LoyaltySettingsHandler serves the loyalty settings (docs/prd-point-coin.md F1, F2).
type LoyaltySettingsHandler struct {
	loyaltySettingsService service.LoyaltySettingsService
}

func NewLoyaltySettingsHandler(loyaltySettingsService service.LoyaltySettingsService) *LoyaltySettingsHandler {
	return &LoyaltySettingsHandler{loyaltySettingsService: loyaltySettingsService}
}

func (h *LoyaltySettingsHandler) GetOutletSettings(c *gin.Context) {
	ctx := c.Request.Context()
	outletID, ok := parseUUIDParam(c, "outlet_id", "LoyaltySettingsHandler::GetOutletSettings")
	if !ok {
		return
	}
	response := h.loyaltySettingsService.GetOutletSettings(ctx, appcontext.FromGinContext(ctx), outletID)
	if response.HasErrors() {
		logger.FromContext(ctx).WithError(response.GetErrors()[0]).Error("LoyaltySettingsHandler::GetOutletSettings -> service call failed")
	}
	util.HandleResponse(c.Writer, c.Request, response, "LoyaltySettingsHandler::GetOutletSettings")
}

func (h *LoyaltySettingsHandler) UpdateOutletSettings(c *gin.Context) {
	ctx := c.Request.Context()
	outletID, ok := parseUUIDParam(c, "outlet_id", "LoyaltySettingsHandler::UpdateOutletSettings")
	if !ok {
		return
	}
	body, err := io.ReadAll(io.LimitReader(c.Request.Body, loyaltySettingsBodyLimit))
	if err != nil {
		util.HandleResponse(c.Writer, c.Request, contract.BuildErrorResponse([]*contract.ResponseError{
			contract.NewResponseError(constants.MalformedFieldErrorCode, constants.RequestEntity, "unable to read request body"),
		}), "LoyaltySettingsHandler::UpdateOutletSettings")
		return
	}
	response := h.loyaltySettingsService.UpdateOutletSettings(ctx, appcontext.FromGinContext(ctx), outletID, body)
	if response.HasErrors() {
		logger.FromContext(ctx).WithError(response.GetErrors()[0]).Error("LoyaltySettingsHandler::UpdateOutletSettings -> service call failed")
	}
	util.HandleResponse(c.Writer, c.Request, response, "LoyaltySettingsHandler::UpdateOutletSettings")
}

// parseUUIDParam reads a UUID path parameter, answering 400 itself when it is not one.
func parseUUIDParam(c *gin.Context, name, method string) (uuid.UUID, bool) {
	id, err := uuid.Parse(c.Param(name))
	if err != nil {
		util.HandleResponse(c.Writer, c.Request, contract.BuildErrorResponse([]*contract.ResponseError{
			contract.NewResponseError(constants.MalformedFieldErrorCode, constants.RequestEntity, "Invalid "+name),
		}), method)
		return uuid.Nil, false
	}
	return id, true
}

func (h *LoyaltySettingsHandler) GetOrganizationSettings(c *gin.Context) {
	ctx := c.Request.Context()
	util.HandleResponse(c.Writer, c.Request, h.loyaltySettingsService.GetOrganizationSettings(ctx, appcontext.FromGinContext(ctx)), "LoyaltySettingsHandler::GetOrganizationSettings")
}

// UpdateOrganizationSettings is PUT /marketing/loyalty-settings. With ?dry_run=true it
// saves nothing and returns what would change and what the balances in circulation
// would be worth, for the warning the dashboard shows before saving (F2).
func (h *LoyaltySettingsHandler) UpdateOrganizationSettings(c *gin.Context) {
	ctx := c.Request.Context()
	body, err := io.ReadAll(io.LimitReader(c.Request.Body, loyaltySettingsBodyLimit))
	if err != nil {
		util.HandleResponse(c.Writer, c.Request, contract.BuildErrorResponse([]*contract.ResponseError{
			contract.NewResponseError(constants.MalformedFieldErrorCode, constants.RequestEntity, "unable to read request body"),
		}), "LoyaltySettingsHandler::UpdateOrganizationSettings")
		return
	}
	response := h.loyaltySettingsService.UpdateOrganizationSettings(ctx, appcontext.FromGinContext(ctx), body, c.Query("dry_run") == "true")
	if response.HasErrors() {
		logger.FromContext(ctx).WithError(response.GetErrors()[0]).Error("LoyaltySettingsHandler::UpdateOrganizationSettings -> service call failed")
	}
	util.HandleResponse(c.Writer, c.Request, response, "LoyaltySettingsHandler::UpdateOrganizationSettings")
}

// ListHistory is GET /marketing/loyalty-settings/history, optionally for one outlet
// (?outlet_id=).
func (h *LoyaltySettingsHandler) ListHistory(c *gin.Context) {
	ctx := c.Request.Context()
	var outletID *uuid.UUID
	if raw := c.Query("outlet_id"); raw != "" {
		id, err := uuid.Parse(raw)
		if err != nil {
			util.HandleResponse(c.Writer, c.Request, contract.BuildErrorResponse([]*contract.ResponseError{
				contract.NewResponseError(constants.MalformedFieldErrorCode, constants.RequestEntity, "Invalid outlet_id"),
			}), "LoyaltySettingsHandler::ListHistory")
			return
		}
		outletID = &id
	}
	page, _ := strconv.Atoi(c.DefaultQuery("page", "1"))
	limit, _ := strconv.Atoi(c.DefaultQuery("limit", "20"))
	util.HandleResponse(c.Writer, c.Request, h.loyaltySettingsService.ListHistory(ctx, appcontext.FromGinContext(ctx), outletID, page, limit), "LoyaltySettingsHandler::ListHistory")
}