Reapply "feat(loyalty): EnakPoint & EnakCoin" (#32)

This reverts commit 4e24f9bbb0.

internal/processor/point_payment_processor_test.go

@@ -0,0 +1,39 @@
+package processor
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestComputePointPaymentLimits(t *testing.T) {
+	for name, c := range map[string]struct {
+		total, paid, paidWithPoints float64
+		percent, value, balance     int64
+		wantRemaining, wantMax      int64
+	}{
+		// The F9 example: Rp 87.550 left, 50.000 EnakPoint, 100%, Rp 1 a point.
+		"PRD example":                           {87550, 0, 0, 100, 1, 50000, 8755000, 50000},
+		"balance covers it all":                 {87550, 0, 0, 100, 1, 100000, 8755000, 87550},
+		"part already paid":                     {100000, 30000, 0, 100, 1, 100000, 7000000, 70000},
+		"capped by percent":                     {100000, 0, 0, 50, 1, 100000, 10000000, 50000},
+		"percent counts EnakPoint already used": {100000, 20000, 20000, 50, 1, 100000, 8000000, 30000},
+		"percent cap already used":              {100000, 50000, 50000, 50, 1, 100000, 5000000, 0},
+		"point worth more than Rp 1":            {87550, 0, 0, 100, 100, 1000, 8755000, 875},
+		"nothing left":                          {50000, 50000, 0, 100, 1, 100000, 0, 0},
+		"overpaid":                              {50000, 60000, 0, 100, 1, 100000, 0, 0},
+		"no balance":                            {50000, 0, 0, 100, 1, 0, 5000000, 0},
+		"cents left over":                       {10000.50, 0, 0, 100, 1, 100000, 1000050, 10000},
+	} {
+		got := computePointPaymentLimits(c.total, c.paid, c.paidWithPoints, c.percent, c.value, c.balance)
+		assert.Equal(t, c.wantRemaining, got.RemainingCents, name)
+		assert.Equal(t, c.wantMax, got.MaxPoints, name)
+		assert.LessOrEqual(t, got.MaxPoints*c.value*100, got.RemainingCents, "%s: never more than what is left", name)
+	}
+}
+
+func TestFormatRupiah(t *testing.T) {
+	for n, want := range map[int64]string{0: "0", 999: "999", 1000: "1.000", 50000: "50.000", 1234567: "1.234.567"} {
+		assert.Equal(t, want, formatRupiah(n))
+	}
+}