package util

import "testing"

func TestTruncateString(t *testing.T) {
	tests := []struct {
		name     string
		input    string
		max      int
		expected string
	}{
		{"shorter than the limit", "abc", 5, "abc"},
		{"exactly at the limit", "abc", 3, "abc"},
		{"longer than the limit", "abcdef", 3, "abc"},
		{"max of one", "abc", 1, "a"},
		{"max of zero", "abc", 0, ""},
		{"negative max", "abc", -1, ""},
		{"empty string", "", 3, ""},
		{"multi-byte characters kept whole", "héllo", 3, "hél"},
		{"multi-byte characters below the limit", "héllo", 99, "héllo"},
		{"characters outside the basic plane", "a😀b", 2, "a😀"},
	}

	for _, test := range tests {
		t.Run(test.name, func(t *testing.T) {
			got := TruncateString(test.input, test.max)
			if got != test.expected {
				t.Errorf("expected %q got %q", test.expected, got)
			}
		})
	}
}

func TestTruncateStringCountsCharactersNotBytes(t *testing.T) {
	// Each of these characters is two bytes long, so a byte-based cut at
	// three would leave half a character behind.
	got := TruncateString("äöü", 3)
	if got != "äöü" {
		t.Errorf("expected %q got %q", "äöü", got)
	}
}