//go:build linux || freebsd
// +build linux freebsd

package ftp

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

	"codeberg.org/petrbalvin/goget/internal/output"
)

// TestSaveFTPResume verifies the helper persists partial FTP progress
// to a .goget.meta sidecar and that the sidecar is suitable for a
// subsequent goget --resume invocation. The function is called from
// Client.DownloadFile when ctx is cancelled mid-transfer; without a
// working sidecar the user's interrupted download cannot be continued.
func TestSaveFTPResume(t *testing.T) {
	tmp := t.TempDir()
	out := filepath.Join(tmp, "file.bin")

	// 1. First call records partial progress.
	if err := saveFTPResume("ftp://example.com/file.bin", out, 4096, 1<<20); err != nil {
		t.Fatalf("saveFTPResume: %v", err)
	}
	meta, err := output.LoadResumeMetadata(out)
	if err != nil {
		t.Fatalf("LoadResumeMetadata: %v", err)
	}
	if meta == nil {
		t.Fatal("expected resume metadata, got nil")
	}
	if meta.URL != "ftp://example.com/file.bin" {
		t.Errorf("URL = %q, want ftp://example.com/file.bin", meta.URL)
	}
	if meta.Downloaded != 4096 {
		t.Errorf("Downloaded = %d, want 4096", meta.Downloaded)
	}
	if meta.Total != 1<<20 {
		t.Errorf("Total = %d, want %d", meta.Total, 1<<20)
	}

	// 2. Second call overwrites the sidecar with a later snapshot.
	if err := saveFTPResume("ftp://example.com/file.bin", out, 8192, 1<<20); err != nil {
		t.Fatalf("saveFTPResume (2): %v", err)
	}
	meta2, _ := output.LoadResumeMetadata(out)
	if meta2 == nil || meta2.Downloaded != 8192 {
		t.Errorf("second call did not update sidecar: %+v", meta2)
	}

	// 3. Zero-byte save is a no-op (no point persisting a sidecar
	// for an empty transfer).
	out2 := filepath.Join(tmp, "empty.bin")
	if err := saveFTPResume("ftp://x", out2, 0, 100); err != nil {
		t.Errorf("zero-byte save returned error: %v", err)
	}
	if _, err := os.Stat(out2 + output.ResumeMetaFileSuffix); !os.IsNotExist(err) {
		t.Errorf("expected no sidecar for zero-byte save, got one")
	}
}