package filesystem

import (
	"archive/tar"
	"archive/zip"
	"compress/gzip"
	"context"
	"fmt"
	"io"
	iofs "io/fs"
	"os"
	"path"
	"path/filepath"
	"reflect"
	"strings"
	"sync/atomic"
	"time"

	"emperror.dev/errors"
	gzip2 "github.com/klauspost/compress/gzip"
	zip2 "github.com/klauspost/compress/zip"
	"github.com/mholt/archiver/v4"
)

// CompressFiles compresses all the files matching the given paths in the
// specified directory. This function also supports passing nested paths to only
// compress certain files and folders when working in a larger directory. This
// effectively creates a local backup, but rather than ignoring specific files
// and folders, it takes an allow-list of files and folders.
//
// All paths are relative to the dir that is passed in as the first argument,
// and the compressed file will be placed at that location named
// `archive-{date}.tar.gz`.
func (fs *Filesystem) CompressFiles(dir string, paths []string) (os.FileInfo, error) {
	cleanedRootDir, err := fs.SafePath(dir)
	if err != nil {
		return nil, err
	}

	// Take all the paths passed in and merge them together with the root directory we've gotten.
	for i, p := range paths {
		paths[i] = filepath.Join(cleanedRootDir, p)
	}

	cleaned, err := fs.ParallelSafePath(paths)
	if err != nil {
		return nil, err
	}

	a := &Archive{BasePath: cleanedRootDir, Files: cleaned}
	d := path.Join(
		cleanedRootDir,
		fmt.Sprintf("archive-%s.tar.gz", strings.ReplaceAll(time.Now().Format(time.RFC3339), ":", "")),
	)

	if err := a.Create(context.Background(), d); err != nil {
		return nil, err
	}

	f, err := os.Stat(d)
	if err != nil {
		_ = os.Remove(d)
		return nil, err
	}

	if err := fs.HasSpaceFor(f.Size()); err != nil {
		_ = os.Remove(d)
		return nil, err
	}

	fs.addDisk(f.Size())

	return f, nil
}

// SpaceAvailableForDecompression looks through a given archive and determines
// if decompressing it would put the server over its allocated disk space limit.
func (fs *Filesystem) SpaceAvailableForDecompression(ctx context.Context, dir string, file string) error {
	// Don't waste time trying to determine this if we know the server will have the space for
	// it since there is no limit.
	if fs.MaxDisk() <= 0 {
		return nil
	}

	source, err := fs.SafePath(filepath.Join(dir, file))
	if err != nil {
		return err
	}

	// Get the cached size in a parallel process so that if it is not cached we are not
	// waiting an unnecessary amount of time on this call.
	dirSize, err := fs.DiskUsage(false)

	fsys, err := archiver.FileSystem(source)
	if err != nil {
		if errors.Is(err, archiver.ErrNoMatch) {
			return newFilesystemError(ErrCodeUnknownArchive, err)
		}
		return err
	}

	var size int64
	return iofs.WalkDir(fsys, ".", func(path string, d iofs.DirEntry, err error) error {
		if err != nil {
			return err
		}

		select {
		case <-ctx.Done():
			// Stop walking if the context is canceled.
			return ctx.Err()
		default:
			info, err := d.Info()
			if err != nil {
				return err
			}
			if atomic.AddInt64(&size, info.Size())+dirSize > fs.MaxDisk() {
				return newFilesystemError(ErrCodeDiskSpace, nil)
			}
			return nil
		}
	})
}

// DecompressFile will decompress a file in a given directory by using the
// archiver tool to infer the file type and go from there. This will walk over
// all the files within the given archive and ensure that there is not a
// zip-slip attack being attempted by validating that the final path is within
// the server data directory.
func (fs *Filesystem) DecompressFile(ctx context.Context, dir string, file string) error {
	source, err := fs.SafePath(filepath.Join(dir, file))
	if err != nil {
		return err
	}
	return fs.DecompressFileUnsafe(ctx, dir, source)
}

// DecompressFileUnsafe will decompress any file on the local disk without checking
// if it is owned by the server.  The file will be SAFELY decompressed and extracted
// into the server's directory.
func (fs *Filesystem) DecompressFileUnsafe(ctx context.Context, dir string, file string) error {
	// Ensure that the archive actually exists on the system.
	if _, err := os.Stat(file); err != nil {
		return errors.WithStack(err)
	}

	f, err := os.Open(file)
	if err != nil {
		return err
	}
	// TODO: defer file close?

	// Identify the type of archive we are dealing with.
	format, input, err := archiver.Identify(filepath.Base(file), f)
	if err != nil {
		if errors.Is(err, archiver.ErrNoMatch) {
			return newFilesystemError(ErrCodeUnknownArchive, err)
		}
		return err
	}

	return fs.extractStream(ctx, extractStreamOptions{
		Directory: dir,
		Format:    format,
		Reader:    input,
	})
}

// ExtractStreamUnsafe .
func (fs *Filesystem) ExtractStreamUnsafe(ctx context.Context, dir string, r io.Reader) error {
	format, input, err := archiver.Identify("archive.tar.gz", r)
	if err != nil {
		if errors.Is(err, archiver.ErrNoMatch) {
			return newFilesystemError(ErrCodeUnknownArchive, err)
		}
		return err
	}

	return fs.extractStream(ctx, extractStreamOptions{
		Directory: dir,
		Format:    format,
		Reader:    input,
	})
}

type extractStreamOptions struct {
	// The directory to extract the archive to.
	Directory string
	// File name of the archive.
	FileName string
	// Format of the archive.
	Format archiver.Format
	// Reader for the archive.
	Reader io.Reader
}

func (fs *Filesystem) extractStream(ctx context.Context, opts extractStreamOptions) error {
	// Decompress and extract archive
	if ex, ok := opts.Format.(archiver.Extractor); ok {
		return ex.Extract(ctx, opts.Reader, nil, func(ctx context.Context, f archiver.File) error {
			if f.IsDir() {
				return nil
			}
			p := filepath.Join(opts.Directory, ExtractNameFromArchive(f))
			// If it is ignored, just don't do anything with the file and skip over it.
			if err := fs.IsIgnored(p); err != nil {
				return nil
			}
			r, err := f.Open()
			if err != nil {
				return err
			}
			defer r.Close()
			if err := fs.Writefile(p, r); err != nil {
				return wrapError(err, opts.FileName)
			}
			// Update the file permissions to the one set in the archive.
			if err := fs.Chmod(p, f.Mode()); err != nil {
				return wrapError(err, opts.FileName)
			}
			// Update the file modification time to the one set in the archive.
			if err := fs.Chtimes(p, f.ModTime(), f.ModTime()); err != nil {
				return wrapError(err, opts.FileName)
			}
			return nil
		})
	}
	return nil
}

// ExtractNameFromArchive looks at an archive file to try and determine the name
// for a given element in an archive. Because of... who knows why, each file type
// uses different methods to determine the file name.
//
// If there is a archiver.File#Sys() value present we will try to use the name
// present in there, otherwise falling back to archiver.File#Name() if all else
// fails. Without this logic present, some archive types such as zip/tars/etc.
// will write all of the files to the base directory, rather than the nested
// directory that is expected.
//
// For files like ".rar" types, there is no f.Sys() value present, and the value
// of archiver.File#Name() will be what you need.
func ExtractNameFromArchive(f archiver.File) string {
	sys := f.Sys()
	// Some archive types won't have a value returned when you call f.Sys() on them,
	// such as ".rar" archives for example. In those cases the only thing you can do
	// is hope that "f.Name()" is actually correct for them.
	if sys == nil {
		return f.Name()
	}
	switch s := sys.(type) {
	case *zip.FileHeader:
		return s.Name
	case *zip2.FileHeader:
		return s.Name
	case *tar.Header:
		return s.Name
	case *gzip.Header:
		return s.Name
	case *gzip2.Header:
		return s.Name
	default:
		// At this point we cannot figure out what type of archive this might be so
		// just try to find the name field in the struct. If it is found return it.
		field := reflect.Indirect(reflect.ValueOf(sys)).FieldByName("Name")
		if field.IsValid() {
			return field.String()
		}
		// Fallback to the basename of the file at this point. There is nothing we can really
		// do to try and figure out what the underlying directory of the file is supposed to
		// be since it didn't implement a name field.
		return f.Name()
	}
}