package entry

import "testing"

func formatDiff(lines []DiffLine) string {
	out := ""
	for _, l := range lines {
		switch l.Op {
		case DiffEqual:
			out += "  " + l.Text + "\n"
		case DiffRemove:
			out += "- " + l.Text + "\n"
		case DiffAdd:
			out += "+ " + l.Text + "\n"
		}
	}
	return out
}

func TestDiffLinesIdentical(t *testing.T) {
	lines := DiffLines("a\nb\nc", "a\nb\nc")
	for _, l := range lines {
		if l.Op != DiffEqual {
			t.Errorf("Op = %v bei identischem Text, erwartet DiffEqual", l.Op)
		}
	}
	if len(lines) != 3 {
		t.Errorf("%d Zeilen, erwartet 3", len(lines))
	}
}

func TestDiffLinesChangeInMiddle(t *testing.T) {
	old := "Zeile 1\nZeile 2\nZeile 3"
	newer := "Zeile 1\nGeändert\nZeile 3"

	got := formatDiff(DiffLines(old, newer))
	want := "  Zeile 1\n- Zeile 2\n+ Geändert\n  Zeile 3\n"
	if got != want {
		t.Errorf("DiffLines =\n%s\nerwartet:\n%s", got, want)
	}
}

func TestDiffLinesPureAddition(t *testing.T) {
	lines := DiffLines("a\nb", "a\nb\nc")
	if len(lines) != 3 || lines[2].Op != DiffAdd || lines[2].Text != "c" {
		t.Errorf("DiffLines = %+v, erwartet [gleich gleich +c]", lines)
	}
}

func TestDiffLinesEmptyOldContent(t *testing.T) {
	lines := DiffLines("", "neu")
	if len(lines) != 1 || lines[0].Op != DiffAdd || lines[0].Text != "neu" {
		t.Errorf("DiffLines(\"\", \"neu\") = %+v, erwartet [+neu]", lines)
	}
}

func TestDiffLinesFallsBackForHugeInput(t *testing.T) {
	// Erzwingt den grobDiff-Pfad ohne wirklich riesige Strings zu bauen: die
	// Grenze fällt auf Zeilenanzahl, nicht Textlänge.
	oldUpper := make([]byte, 0, 2200*2)
	newUpper := make([]byte, 0, 2200*2)
	for i := 0; i < 2200; i++ {
		oldUpper = append(oldUpper, 'a', '\n')
		newUpper = append(newUpper, 'b', '\n')
	}

	lines := DiffLines(string(oldUpper), string(newUpper))
	for _, l := range lines {
		if l.Op == DiffEqual {
			t.Fatal("grobDiff sollte keine DiffEqual-Zeilen liefern")
		}
	}
}