package inventory

import (
	"context"
	"fmt"
	"net/http"
)

// StockReader abstracts the inventory getter for badge rendering.
type StockReader interface {
	GetInventory(ctx context.Context, sku SKU, locationID LocationID) (int64, error)
}

// BadgeHandler returns an http.HandlerFunc that renders an HTML stock badge fragment.
func BadgeHandler(reader StockReader) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		sku := r.URL.Query().Get("sku")
		if sku == "" {
			http.Error(w, "missing sku parameter", http.StatusBadRequest)
			return
		}

		locationID := LocationID(r.URL.Query().Get("location_id"))
		if locationID == "" {
			locationID = LocationID(r.URL.Query().Get("country"))
		}
		if locationID == "" {
			locationID = "se"
		}

		w.Header().Set("Content-Type", "text/html; charset=utf-8")
		w.Header().Set("Cache-Control", "private, max-age=5")

		qty, err := reader.GetInventory(r.Context(), SKU(sku), locationID)
		if err != nil {
			w.WriteHeader(http.StatusOK)
			w.Write([]byte(`<span class="stock-badge stock-unknown" data-sku="` + sku + `">Availability unavailable</span>`))
			return
		}

		var htmlSnippet string
		switch {
		case qty > 10:
			htmlSnippet = fmt.Sprintf(`<span class="stock-badge stock-in-stock" data-sku="%s">✓ In stock</span>`, sku)
		case qty > 0:
			htmlSnippet = fmt.Sprintf(`<span class="stock-badge stock-low-stock" data-sku="%s">⚡ Only %d left!</span>`, sku, qty)
		default:
			htmlSnippet = fmt.Sprintf(`<span class="stock-badge stock-out-of-stock" data-sku="%s">✕ Out of stock</span>`, sku)
		}

		w.WriteHeader(http.StatusOK)
		w.Write([]byte(htmlSnippet))
	}
}