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

package output

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

// TestCloseAtomicSuccess verifies the happy path: temp file is renamed to
// the final destination and no temp file remains.
func TestCloseAtomicSuccess(t *testing.T) {
	dir := tempDir(t)
	outputPath := filepath.Join(dir, "output.txt")

	w, err := NewWriter(&WriterConfig{
		Output: outputPath,
		Atomic: true,
	})
	if err != nil {
		t.Fatalf("NewWriter: %v", err)
	}

	payload := []byte("hello world")
	if _, err := w.Write(payload); err != nil {
		t.Fatalf("Write: %v", err)
	}

	if err := w.Close(); err != nil {
		t.Fatalf("Close: %v", err)
	}

	got, err := os.ReadFile(outputPath)
	if err != nil {
		t.Fatalf("ReadFile: %v", err)
	}
	if string(got) != string(payload) {
		t.Errorf("payload = %q, want %q", got, payload)
	}

	// No leftover temp files in the directory.
	entries, err := os.ReadDir(dir)
	if err != nil {
		t.Fatalf("ReadDir: %v", err)
	}
	for _, e := range entries {
		if strings.Contains(e.Name(), ".tmp.") {
			t.Errorf("temp file %q should have been renamed away", e.Name())
		}
	}
}

// TestCloseKeepsTempOnRenameError is a regression guard for the BACKLOG
// entry "Atomic write data loss on cross-filesystem rename". The previous
// implementation called os.Remove(tempPath) on any rename error, deleting
// the only copy of the downloaded data. After the fix, the temp file must
// remain on disk so the user can recover the partial download manually.
//
// We force a rename error by pre-creating the destination as a directory —
// os.Rename will refuse to overwrite a non-empty directory with a file.
func TestCloseKeepsTempOnRenameError(t *testing.T) {
	dir := tempDir(t)
	outputPath := filepath.Join(dir, "output.txt")

	// Block the rename by making the target path a directory.
	if err := os.Mkdir(outputPath, 0755); err != nil {
		t.Fatalf("mkdir: %v", err)
	}

	w, err := NewWriter(&WriterConfig{
		Output: outputPath,
		Atomic: true,
	})
	if err != nil {
		t.Fatalf("NewWriter: %v", err)
	}

	payload := []byte("recoverable download data")
	if _, err := w.Write(payload); err != nil {
		t.Fatalf("Write: %v", err)
	}

	tempPath := w.tempFile.Name()

	if err := w.Close(); err == nil {
		t.Fatal("expected Close() to return an error when target is a directory")
	}

	// The temp file MUST still exist — the data must be recoverable.
	if _, err := os.Stat(tempPath); err != nil {
		t.Errorf("temp file %q should still exist after Close error, got: %v", tempPath, err)
	}

	// And it should still hold the full payload.
	got, err := os.ReadFile(tempPath)
	if err != nil {
		t.Fatalf("ReadFile(temp): %v", err)
	}
	if string(got) != string(payload) {
		t.Errorf("temp file payload = %q, want %q", got, payload)
	}
}

// TestCopyFileAndRemove covers the EXDEV fallback helper directly. We do
// not have an easy way to mount two different filesystems in a unit test,
// so we just verify the copy + remove behaviour on the same filesystem.
func TestCopyFileAndRemove(t *testing.T) {
	dir := tempDir(t)
	src := filepath.Join(dir, "src.tmp")
	dst := filepath.Join(dir, "dst.bin")

	payload := []byte("cross-fs fallback payload")
	if err := os.WriteFile(src, payload, 0644); err != nil {
		t.Fatalf("WriteFile(src): %v", err)
	}

	if err := copyFileAndRemove(src, dst); err != nil {
		t.Fatalf("copyFileAndRemove: %v", err)
	}

	got, err := os.ReadFile(dst)
	if err != nil {
		t.Fatalf("ReadFile(dst): %v", err)
	}
	if string(got) != string(payload) {
		t.Errorf("dst = %q, want %q", got, payload)
	}

	if _, err := os.Stat(src); !os.IsNotExist(err) {
		t.Errorf("src should be removed, got stat err = %v", err)
	}
}

// TestCopyFileAndRemoveOverwritesExisting verifies the fallback truncates
// any existing file at the destination (matching os.Rename semantics).
func TestCopyFileAndRemoveOverwritesExisting(t *testing.T) {
	dir := tempDir(t)
	src := filepath.Join(dir, "src.tmp")
	dst := filepath.Join(dir, "dst.bin")

	if err := os.WriteFile(src, []byte("new"), 0644); err != nil {
		t.Fatalf("WriteFile(src): %v", err)
	}
	if err := os.WriteFile(dst, []byte("OLD CONTENT"), 0644); err != nil {
		t.Fatalf("WriteFile(dst): %v", err)
	}

	if err := copyFileAndRemove(src, dst); err != nil {
		t.Fatalf("copyFileAndRemove: %v", err)
	}

	got, err := os.ReadFile(dst)
	if err != nil {
		t.Fatalf("ReadFile(dst): %v", err)
	}
	if string(got) != "new" {
		t.Errorf("dst = %q, want %q", got, "new")
	}
}

// TestNewWriterCreateDirsMissingParent verifies the curl --create-dirs
// equivalent: when CreateDirs is true and the parent directory of Output
// does not exist, NewWriter must create the full chain via MkdirAll and
// successfully write the file. This is the happy path for "goget
// --output ./data/archives/file.zip" against a fresh tree.
func TestNewWriterCreateDirsMissingParent(t *testing.T) {
	dir := tempDir(t)
	outputPath := filepath.Join(dir, "deeply", "nested", "subdir", "file.dat")

	w, err := NewWriter(&WriterConfig{
		Output:     outputPath,
		Atomic:     true,
		CreateDirs: true,
	})
	if err != nil {
		t.Fatalf("NewWriter: %v", err)
	}

	payload := []byte("created in a fresh dir tree")
	if _, err := w.Write(payload); err != nil {
		t.Fatalf("Write: %v", err)
	}
	if err := w.Close(); err != nil {
		t.Fatalf("Close: %v", err)
	}

	got, err := os.ReadFile(outputPath)
	if err != nil {
		t.Fatalf("ReadFile: %v", err)
	}
	if string(got) != string(payload) {
		t.Errorf("payload = %q, want %q", got, payload)
	}
}

// TestNewWriterCreateDirsDisabledLeavesError confirms that without
// CreateDirs the writer still surfaces the underlying "parent dir missing"
// error — CreateDirs is opt-in, not a silent behaviour change for existing
// users.
func TestNewWriterCreateDirsDisabledLeavesError(t *testing.T) {
	dir := tempDir(t)
	outputPath := filepath.Join(dir, "missing", "file.dat")

	_, err := NewWriter(&WriterConfig{
		Output:     outputPath,
		Atomic:     true,
		CreateDirs: false,
	})
	if err == nil {
		t.Fatal("expected NewWriter to fail when parent dir is missing and CreateDirs=false")
	}
}

// TestNewWriterCreateDirsIgnoredForStdout makes sure the - / stdout path is
// untouched by the new flag: nothing to create, no spurious error.
func TestNewWriterCreateDirsIgnoredForStdout(t *testing.T) {
	w, err := NewWriter(&WriterConfig{
		Output:     "-",
		Atomic:     false,
		CreateDirs: true,
	})
	if err != nil {
		t.Fatalf("NewWriter: %v", err)
	}
	if w.file != os.Stdout {
		t.Errorf("expected writer to point at stdout, got %v", w.file)
	}
	w.Close()
}