package storage

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

	"github.com/veggiedefender/torrent-client/internal/torrentfile"
)

func TestPieceReader(t *testing.T) {
	tempDir := t.TempDir()

	file1 := filepath.Join(tempDir, "file1.txt")
	file2 := filepath.Join(tempDir, "file2.txt")

	data1 := []byte("hello ") // 6 bytes
	data2 := []byte("world!") // 6 bytes
	
	if err := os.WriteFile(file1, data1, 0644); err != nil {
		t.Fatal(err)
	}
	if err := os.WriteFile(file2, data2, 0644); err != nil {
		t.Fatal(err)
	}

	files := []torrentfile.File{
		{Path: "file1.txt", Length: 6},
		{Path: "file2.txt", Length: 6},
	}

	pr := NewPieceReader(files, 4, 12, tempDir)

	// Test reading from first file only
	// Piece 0, begin 0, length 4 -> "hell"
	b, err := pr.ReadBlock(0, 0, 4)
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	if !bytes.Equal(b, []byte("hell")) {
		t.Errorf("expected 'hell', got %q", b)
	}

	// Test reading across files
	// Piece 1, begin 0, length 4 -> absolute offset 4 -> "o wo"
	b, err = pr.ReadBlock(1, 0, 4)
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	if !bytes.Equal(b, []byte("o wo")) {
		t.Errorf("expected 'o wo', got %q", b)
	}

	// Test reading at the end
	// Piece 2, begin 0, length 4 -> absolute offset 8 -> "rld!"
	b, err = pr.ReadBlock(2, 0, 4)
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	if !bytes.Equal(b, []byte("rld!")) {
		t.Errorf("expected 'rld!', got %q", b)
	}

	// Test reading out of bounds
	_, err = pr.ReadBlock(2, 2, 4)
	if err == nil {
		t.Errorf("expected error when reading out of bounds")
	}
}