package fileops

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

func TestPromoteDirectoryCopiesNestedRegularTree(t *testing.T) {
	root := t.TempDir()
	src := filepath.Join(root, "source")
	dst := filepath.Join(root, "promoted")
	mustWriteFile(t, filepath.Join(src, "z-last.txt"), []byte("last"), 0o777)
	mustWriteFile(t, filepath.Join(src, "nested", "binary.dat"), []byte{0, 1, 2, 0xff}, 0o600)
	mustWriteFile(t, filepath.Join(src, "a-first.txt"), []byte("first"), 0o400)
	if err := os.Mkdir(filepath.Join(src, "empty"), 0o700); err != nil {
		t.Fatalf("Mkdir(empty) error = %v", err)
	}

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

	wantLayout := []string{".", "a-first.txt", "empty", "nested", "nested/binary.dat", "z-last.txt"}
	if got := treeLayout(t, dst); !reflect.DeepEqual(got, wantLayout) {
		t.Fatalf("promoted layout = %#v, want %#v", got, wantLayout)
	}
	assertFileBytes(t, filepath.Join(dst, "a-first.txt"), []byte("first"))
	assertFileBytes(t, filepath.Join(dst, "nested", "binary.dat"), []byte{0, 1, 2, 0xff})
	assertFileBytes(t, filepath.Join(dst, "z-last.txt"), []byte("last"))

	for _, path := range []string{dst, filepath.Join(dst, "nested"), filepath.Join(dst, "empty")} {
		info, err := os.Stat(path)
		if err != nil {
			t.Fatalf("Stat(%q) error = %v", path, err)
		}
		if got := info.Mode().Perm(); got != promotedDirectoryMode {
			t.Fatalf("directory mode for %q = %o, want %o", path, got, promotedDirectoryMode)
		}
	}
	for _, path := range []string{filepath.Join(dst, "a-first.txt"), filepath.Join(dst, "nested", "binary.dat"), filepath.Join(dst, "z-last.txt")} {
		info, err := os.Stat(path)
		if err != nil {
			t.Fatalf("Stat(%q) error = %v", path, err)
		}
		if got := info.Mode().Perm(); got != promotedFileMode {
			t.Fatalf("file mode for %q = %o, want %o", path, got, promotedFileMode)
		}
	}

	assertFileBytes(t, filepath.Join(src, "nested", "binary.dat"), []byte{0, 1, 2, 0xff})
	assertNoMatchingTempDirectories(t, root, ".promoted.tmp-")
}

func TestPromoteDirectoryRejectsInvalidPaths(t *testing.T) {
	root := t.TempDir()
	src := filepath.Join(root, "source")
	if err := os.Mkdir(src, 0o755); err != nil {
		t.Fatalf("Mkdir(source) error = %v", err)
	}

	tests := []struct {
		name string
		src  string
		dst  string
	}{
		{name: "empty source", src: "", dst: filepath.Join(root, "out-a")},
		{name: "empty destination", src: src, dst: " "},
	}
	for _, test := range tests {
		t.Run(test.name, func(t *testing.T) {
			if err := PromoteDirectory(test.src, test.dst); err == nil {
				t.Fatal("PromoteDirectory() error = nil, want path validation failure")
			}
		})
	}
}

func TestPromoteDirectoryRejectsExistingDestination(t *testing.T) {
	root := t.TempDir()
	src := filepath.Join(root, "source")
	dst := filepath.Join(root, "destination")
	mustWriteFile(t, filepath.Join(src, "value.txt"), []byte("source"), 0o644)
	mustWriteFile(t, filepath.Join(dst, "value.txt"), []byte("existing"), 0o644)

	err := PromoteDirectory(src, dst)
	if err == nil || !strings.Contains(err.Error(), "already exists") {
		t.Fatalf("PromoteDirectory() error = %v, want existing destination error", err)
	}
	assertFileBytes(t, filepath.Join(dst, "value.txt"), []byte("existing"))
	assertFileBytes(t, filepath.Join(src, "value.txt"), []byte("source"))
	assertNoMatchingTempDirectories(t, root, ".destination.tmp-")
}

func TestPromoteDirectoryRejectsNonDirectorySource(t *testing.T) {
	root := t.TempDir()
	src := filepath.Join(root, "source.txt")
	dst := filepath.Join(root, "destination")
	mustWriteFile(t, src, []byte("source"), 0o644)

	if err := PromoteDirectory(src, dst); err == nil {
		t.Fatal("PromoteDirectory() error = nil, want non-directory source error")
	}
	assertFileBytes(t, src, []byte("source"))
	if _, err := os.Lstat(dst); !os.IsNotExist(err) {
		t.Fatalf("Lstat(destination) error = %v, want not exist", err)
	}
}

func TestPromoteDirectoryRejectsSymlinksWithoutFollowingThem(t *testing.T) {
	root := t.TempDir()
	externalFile := filepath.Join(root, "external.txt")
	externalDirectory := filepath.Join(root, "external-directory")
	mustWriteFile(t, externalFile, []byte("outside"), 0o644)
	mustWriteFile(t, filepath.Join(externalDirectory, "secret.txt"), []byte("secret"), 0o644)

	tests := []struct {
		name   string
		target string
		link   string
	}{
		{name: "file", target: externalFile, link: "file-link"},
		{name: "directory", target: externalDirectory, link: "directory-link"},
		{name: "escaping", target: filepath.Join("..", "external.txt"), link: "escaping-link"},
	}
	for _, test := range tests {
		t.Run(test.name, func(t *testing.T) {
			src := filepath.Join(root, "source-"+test.name)
			dst := filepath.Join(root, "destination-"+test.name)
			if err := os.Mkdir(src, 0o755); err != nil {
				t.Fatalf("Mkdir(source) error = %v", err)
			}
			if err := os.Symlink(test.target, filepath.Join(src, test.link)); err != nil {
				t.Skipf("Symlink() unavailable: %v", err)
			}

			if err := PromoteDirectory(src, dst); err == nil {
				t.Fatal("PromoteDirectory() error = nil, want symlink rejection")
			}
			linkInfo, err := os.Lstat(filepath.Join(src, test.link))
			if err != nil || linkInfo.Mode()&os.ModeSymlink == 0 {
				t.Fatalf("source symlink was not preserved: info=%v err=%v", linkInfo, err)
			}
			if _, err := os.Lstat(dst); !os.IsNotExist(err) {
				t.Fatalf("Lstat(destination) error = %v, want not exist", err)
			}
			assertNoMatchingTempDirectories(t, root, ".destination-"+test.name+".tmp-")
		})
	}
	assertFileBytes(t, externalFile, []byte("outside"))
	assertFileBytes(t, filepath.Join(externalDirectory, "secret.txt"), []byte("secret"))
}

func TestPromoteDirectoryDoesNotReplaceDestinationCreatedBeforeInstall(t *testing.T) {
	root := t.TempDir()
	src := filepath.Join(root, "source")
	dst := filepath.Join(root, "destination")
	mustWriteFile(t, filepath.Join(src, "value.txt"), []byte("source"), 0o644)

	err := promoteDirectory(src, dst, func(temporary, destination string) error {
		if err := os.Mkdir(destination, 0o755); err != nil {
			t.Fatalf("Mkdir(concurrent destination) error = %v", err)
		}
		mustWriteFile(t, filepath.Join(destination, "value.txt"), []byte("concurrent"), 0o644)
		return renameDirectoryNoReplace(temporary, destination)
	})
	if err == nil {
		t.Fatal("promoteDirectory() error = nil, want no-replace install failure")
	}
	assertFileBytes(t, filepath.Join(dst, "value.txt"), []byte("concurrent"))
	assertFileBytes(t, filepath.Join(src, "value.txt"), []byte("source"))
	assertNoMatchingTempDirectories(t, root, ".destination.tmp-")
}

func TestPromoteDirectoryRejectsDestinationInsideSource(t *testing.T) {
	root := t.TempDir()
	src := filepath.Join(root, "source")
	dst := filepath.Join(src, "nested", "destination")
	if err := os.MkdirAll(filepath.Dir(dst), 0o755); err != nil {
		t.Fatalf("MkdirAll(destination parent) error = %v", err)
	}

	if err := PromoteDirectory(src, dst); err == nil {
		t.Fatal("PromoteDirectory() error = nil, want nested destination rejection")
	}
	if _, err := os.Lstat(dst); !os.IsNotExist(err) {
		t.Fatalf("Lstat(destination) error = %v, want not exist", err)
	}
}

func mustWriteFile(t *testing.T, path string, data []byte, mode os.FileMode) {
	t.Helper()
	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
		t.Fatalf("MkdirAll(%q) error = %v", filepath.Dir(path), err)
	}
	if err := os.WriteFile(path, data, mode); err != nil {
		t.Fatalf("WriteFile(%q) error = %v", path, err)
	}
}

func assertFileBytes(t *testing.T, path string, want []byte) {
	t.Helper()
	got, err := os.ReadFile(path)
	if err != nil {
		t.Fatalf("ReadFile(%q) error = %v", path, err)
	}
	if !bytes.Equal(got, want) {
		t.Fatalf("ReadFile(%q) = %v, want %v", path, got, want)
	}
}

func treeLayout(t *testing.T, root string) []string {
	t.Helper()
	var layout []string
	err := filepath.WalkDir(root, func(path string, _ os.DirEntry, err error) error {
		if err != nil {
			return err
		}
		relative, err := filepath.Rel(root, path)
		if err != nil {
			return err
		}
		layout = append(layout, filepath.ToSlash(relative))
		return nil
	})
	if err != nil {
		t.Fatalf("WalkDir(%q) error = %v", root, err)
	}
	return layout
}

func assertNoMatchingTempDirectories(t *testing.T, parent, prefix string) {
	t.Helper()
	entries, err := os.ReadDir(parent)
	if err != nil {
		t.Fatalf("ReadDir(%q) error = %v", parent, err)
	}
	for _, entry := range entries {
		if strings.HasPrefix(entry.Name(), prefix) {
			t.Fatalf("unexpected temporary directory residue: %s", filepath.Join(parent, entry.Name()))
		}
	}
}