package storager

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

func TestMergePartFile(t *testing.T) {
	tempDir := t.TempDir()
	partDir := filepath.Join(tempDir, "parts")
	if err := os.MkdirAll(partDir, 0o755); err != nil {
		t.Fatal(err)
	}

	parts := map[string][]byte{
		"1":  []byte("first-"),
		"2":  []byte("second-"),
		"10": []byte("tenth"),
	}
	for name, content := range parts {
		if err := os.WriteFile(filepath.Join(partDir, name), content, 0o644); err != nil {
			t.Fatal(err)
		}
	}

	destination := filepath.Join(tempDir, "merged.bin")
	if err := os.WriteFile(destination, []byte("stale-data"), 0o644); err != nil {
		t.Fatal(err)
	}
	if err := MergePartFile(partDir, destination); err != nil {
		t.Fatalf("合并分片失败: %v", err)
	}

	actual, err := os.ReadFile(destination)
	if err != nil {
		t.Fatal(err)
	}
	expected := []byte("first-second-tenth")
	if !bytes.Equal(actual, expected) {
		t.Fatalf("合并内容不符 expected=%q actual=%q", expected, actual)
	}
}

func TestMergePartFileRejectsEmptyDirectory(t *testing.T) {
	partDir := t.TempDir()
	err := MergePartFile(partDir, filepath.Join(t.TempDir(), "merged.bin"))
	if err == nil {
		t.Fatal("空分片目录应返回错误")
	}
}