package claude

import (
	"os"
	"path/filepath"
	"strings"
	"testing"
)

func TestTailLastNLines_NewestFirst(t *testing.T) {
	dir := t.TempDir()
	p := filepath.Join(dir, "history.jsonl")

	var b strings.Builder
	for i := 1; i <= 5; i++ {
		b.WriteString("line")
		b.WriteString([]string{"1", "2", "3", "4", "5"}[i-1])
		b.WriteString("\n")
	}
	if err := os.WriteFile(p, []byte(b.String()), 0o600); err != nil {
		t.Fatalf("write: %v", err)
	}

	lines, err := TailLastNLines(p, 2)
	if err != nil {
		t.Fatalf("TailLastNLines: %v", err)
	}
	if len(lines) != 2 {
		t.Fatalf("len=%d", len(lines))
	}
	if lines[0] != "line5" || lines[1] != "line4" {
		t.Fatalf("got=%v", lines)
	}
}