Add IntWithCommas utility function and corresponding tests

internal/util/numutil/int_with_commas.go

@@ -0,0 +1,18 @@
+package numutil
+
+import "fmt"
+
+// IntWithCommas returns a string representation of an integer with commas.
+//
+// Example:
+//
+//	12345 -> "12,345"
+func IntWithCommas[T int | int32 | int64 | uint | uint32 | uint64](i T) string {
+	if i < 0 {
+		return "-" + IntWithCommas(-i)
+	}
+	if i < 1000 {
+		return fmt.Sprintf("%d", i)
+	}
+	return IntWithCommas(i/1000) + "," + fmt.Sprintf("%03d", i%1000)
+}

internal/util/numutil/int_with_commas_test.go

@@ -0,0 +1,109 @@
+package numutil
+
+import (
+	"math"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestIntWithCommas(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    int64
+		expected string
+	}{
+		{
+			name:     "zero",
+			input:    0,
+			expected: "0",
+		},
+		{
+			name:     "single digit",
+			input:    5,
+			expected: "5",
+		},
+		{
+			name:     "two digits",
+			input:    42,
+			expected: "42",
+		},
+		{
+			name:     "three digits",
+			input:    999,
+			expected: "999",
+		},
+		{
+			name:     "four digits",
+			input:    1000,
+			expected: "1,000",
+		},
+		{
+			name:     "five digits",
+			input:    12345,
+			expected: "12,345",
+		},
+		{
+			name:     "six digits",
+			input:    123456,
+			expected: "123,456",
+		},
+		{
+			name:     "seven digits",
+			input:    1234567,
+			expected: "1,234,567",
+		},
+		{
+			name:     "eight digits",
+			input:    12345678,
+			expected: "12,345,678",
+		},
+		{
+			name:     "nine digits",
+			input:    123456789,
+			expected: "123,456,789",
+		},
+		{
+			name:     "ten digits",
+			input:    1234567890,
+			expected: "1,234,567,890",
+		},
+		{
+			name:     "large number",
+			input:    1234567890123456789,
+			expected: "1,234,567,890,123,456,789",
+		},
+		{
+			name:     "negative small",
+			input:    -42,
+			expected: "-42",
+		},
+		{
+			name:     "negative large",
+			input:    -12345678,
+			expected: "-12,345,678",
+		},
+		{
+			name:     "edge case 999999",
+			input:    999999,
+			expected: "999,999",
+		},
+		{
+			name:     "edge case -1000",
+			input:    -1000,
+			expected: "-1,000",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			assert.Equal(t, tt.expected, IntWithCommas(tt.input))
+			if tt.input < math.MaxInt {
+				assert.Equal(t, tt.expected, IntWithCommas(int(tt.input)))
+			}
+			if tt.input < math.MaxInt32 {
+				assert.Equal(t, tt.expected, IntWithCommas(int32(tt.input)))
+			}
+		})
+	}
+}