package processor

import (
	"math/rand"
	"testing"

	"github.com/google/uuid"
	"github.com/stretchr/testify/assert"

	"apskel-pos-be/internal/constants"
	"apskel-pos-be/internal/repository"
)

func TestSplitVoucherCost(t *testing.T) {
	october := uuid.New()
	// RFC §7.6: Rp10.000 voucher for 8.000 EnakPoint, 6.000 from an EnakGame reward
	// and 2.000 from shopping.
	parts := SplitVoucherCost(10_000, []repository.RedemptionPointSource{
		{Points: 2_000, SourceType: constants.WalletTxTypeEarn},
		{Points: 6_000, SourceType: constants.WalletTxTypeGameReward, BudgetID: &october},
	})
	assert.EqualValues(t, 2_500, parts[0].Cost)
	assert.EqualValues(t, 7_500, parts[1].Cost)

	// Not evenly divisible: the remainder goes to the largest part, the first of equals.
	parts = SplitVoucherCost(10_000, []repository.RedemptionPointSource{{Points: 3}, {Points: 3}, {Points: 3}})
	assert.Equal(t, []int64{3_334, 3_333, 3_333}, []int64{parts[0].Cost, parts[1].Cost, parts[2].Cost})
	parts = SplitVoucherCost(100, []repository.RedemptionPointSource{{Points: 1}, {Points: 5}, {Points: 1}})
	assert.Equal(t, []int64{14, 72, 14}, []int64{parts[0].Cost, parts[1].Cost, parts[2].Cost})

	// No overflow on large numbers.
	parts = SplitVoucherCost(9_000_000_000_000, []repository.RedemptionPointSource{{Points: 3_000_000_000_000}, {Points: 6_000_000_000_000}})
	assert.Equal(t, []int64{3_000_000_000_000, 6_000_000_000_000}, []int64{parts[0].Cost, parts[1].Cost})

	assert.Empty(t, SplitVoucherCost(10, nil))

	// Whatever the numbers, the parts add up to the face value and none is negative.
	rng := rand.New(rand.NewSource(7))
	for i := 0; i < 2_000; i++ {
		face := rng.Int63n(1_000_000) + 1
		sources := make([]repository.RedemptionPointSource, rng.Intn(5)+1)
		for j := range sources {
			sources[j].Points = rng.Int63n(10_000) + 1
		}
		var sum int64
		for _, p := range SplitVoucherCost(face, sources) {
			assert.GreaterOrEqual(t, p.Cost, int64(0))
			sum += p.Cost
		}
		assert.Equal(t, face, sum)
	}
}