package models

import (
	"encoding/json"
	"testing"
)

/*
A missing string must reach a client as "", never as an absent key.

`unitvalue` and `productunit` were both `omitempty`, and on this platform
`unitvalue` is empty for every product — measured 2026-09-02 on R mart: 24
products, 0 with both fields, 7 with a unit and no value. So the key vanished
from the JSON, a client read `undefined`, and joining it to the unit rendered
the literal text "null kg" on a shopper's screen.

The same applies to money: a price of 0 is a real answer ("this has no price
set"), and a client that receives no key at all cannot tell that from a field
it forgot to request.
*/

func fieldsOf(t *testing.T, v any) map[string]any {
	t.Helper()
	raw, err := json.Marshal(v)
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	var out map[string]any
	if err := json.Unmarshal(raw, &out); err != nil {
		t.Fatalf("unmarshal: %v", err)
	}
	return out
}

func TestAnEmptyUnitIsSentAsEmptyNotOmitted(t *testing.T) {
	got := fieldsOf(t, Products{Productid: 1})
	for _, key := range []string{"unitvalue", "productunit"} {
		if _, present := got[key]; !present {
			t.Errorf("%q was omitted; a client reads that as null and renders it", key)
		}
	}
}

func TestAZeroPriceIsSentAsZeroNotOmitted(t *testing.T) {
	got := fieldsOf(t, Products{Productid: 1})
	if _, present := got["retailprice"]; !present {
		t.Error("retailprice was omitted; 0 is a real answer and must be visible")
	}
}

func TestAVariantAlwaysCarriesItsPriceAndUnit(t *testing.T) {
	got := fieldsOf(t, Productvariant{Variantid: 1})
	for _, key := range []string{"price", "variantprice", "variantunitvalue", "variantproductunit"} {
		if _, present := got[key]; !present {
			t.Errorf("variant option omitted %q", key)
		}
	}
}

func TestAProductWithNoVariantsSendsAnEmptyListNotNull(t *testing.T) {
	// The case that lets an order proceed: [] means "order this one directly".
	// A JSON null would force every client to null-check before counting.
	got := fieldsOf(t, Products{Productid: 1, Variantoptions: []Productvariant{}})
	list, ok := got["variantoptions"].([]any)
	if !ok {
		t.Fatalf("variantoptions was %T, want a list", got["variantoptions"])
	}
	if len(list) != 0 {
		t.Errorf("expected an empty list, got %d", len(list))
	}
}