package s3

import "testing"

// TestUploadPartSize checks that an upload too large for 10,000 parts of the
// configured size gets parts just large enough to fit in 10,000.
func TestUploadPartSize(t *testing.T) {
	t.Parallel()

	const mib = 1024 * 1024

	tests := []struct {
		name       string
		configured int64
		size       int64
		want       int64
	}{
		{
			name:       "an upload that fits keeps the configured size",
			configured: 5 * mib,
			size:       10 * 1024 * mib,
			want:       5 * mib,
		},
		{
			name:       "exactly 10,000 parts keeps the configured size",
			configured: 6 * mib,
			size:       10_000 * 6 * mib,
			want:       6 * mib,
		},
		{
			name:       "one byte more than 10,000 parts adds a byte to each",
			configured: 6 * mib,
			size:       10_000*6*mib + 1,
			want:       6*mib + 1,
		},
		{
			name:       "zero means the SDK default of 5MiB",
			configured: 0,
			size:       1,
			want:       5 * mib,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			t.Parallel()

			got := uploadPartSize(tt.configured, tt.size)
			if got != tt.want {
				t.Errorf("uploadPartSize(%d, %d) = %d, want %d",
					tt.configured, tt.size, got, tt.want)
			}
		})
	}
}