package logbuf

import (
	"fmt"
	"testing"
)

func TestRingKeepsMostRecent(t *testing.T) {
	w := New(3)
	for i := 0; i < 5; i++ {
		fmt.Fprintf(w, "line %d\n", i)
	}
	got := w.Lines(0)
	want := []string{"line 2", "line 3", "line 4"}
	if len(got) != len(want) {
		t.Fatalf("got %d lines, want %d: %v", len(got), len(want), got)
	}
	for i := range want {
		if got[i] != want[i] {
			t.Errorf("line %d = %q, want %q", i, got[i], want[i])
		}
	}
}

func TestLinesN(t *testing.T) {
	w := New(10)
	for i := 0; i < 5; i++ {
		fmt.Fprintf(w, "l%d\n", i)
	}
	if got := w.Lines(2); len(got) != 2 || got[0] != "l3" || got[1] != "l4" {
		t.Errorf("Lines(2) = %v, want [l3 l4]", got)
	}
	if got := w.Lines(100); len(got) != 5 {
		t.Errorf("Lines(100) = %d lines, want all 5", len(got))
	}
}

func TestMultilineAndBlankWrite(t *testing.T) {
	w := New(10)
	if _, err := w.Write([]byte("a\nb\n\nc\n")); err != nil {
		t.Fatal(err)
	}
	got := w.Lines(0)
	want := []string{"a", "b", "c"} // blank line dropped
	if len(got) != len(want) {
		t.Fatalf("got %v, want %v", got, want)
	}
}