package filesystem

import (
	"archive/tar"
	"archive/zip"
	"compress/gzip"
	"fmt"
	"os"
	"path/filepath"
	"reflect"
	"strings"
	"sync/atomic"

	"emperror.dev/errors"
	"github.com/mholt/archiver/v3"
)

// 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(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)

	var size int64
	// Walk over the archive and figure out just how large the final output would be from unarchiving it.
	err = archiver.Walk(source, func(f archiver.File) error {
		if atomic.AddInt64(&size, f.Size())+dirSize > fs.MaxDisk() {
			return &Error{code: ErrCodeDiskSpace}
		}
		return nil
	})
	if err != nil {
		if strings.HasPrefix(err.Error(), "format ") {
			return &Error{code: ErrCodeUnknownArchive}
		}
		return err
	}
	return err
}

// 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 of 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(dir string, file string) error {
	source, err := fs.SafePath(filepath.Join(dir, file))
	if err != nil {
		return err
	}
	// Ensure that the source archive actually exists on the system.
	if _, err := os.Stat(source); err != nil {
		return err
	}

	// Walk over all of the files spinning up an additional go-routine for each file we've encountered
	// and then extract that file from the archive and write it to the disk. If any part of this process
	// encounters an error the entire process will be stopped.
	err = archiver.Walk(source, func(f archiver.File) error {
		// Don't waste time with directories, we don't need to create them if they have no contents, and
		// we will ensure the directory exists when opening the file for writing anyways.
		if f.IsDir() {
			return nil
		}

		var name string
		switch s := f.Sys().(type) {
		case *tar.Header:
			name = s.Name
		case *gzip.Header:
			name = s.Name
		case *zip.FileHeader:
			name = s.Name
		default:
			return &Error{
				code:     ErrCodeUnknownError,
				resolved: filepath.Join(dir, f.Name()),
				err:      errors.New(fmt.Sprintf("could not parse underlying data source with type: %s", reflect.TypeOf(s).String())),
			}
		}

		p := filepath.Join(dir, name)
		// 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
		}
		if err := fs.Writefile(p, f); err != nil {
			return &Error{code: ErrCodeUnknownError, err: err, resolved: source}
		}
		return nil
	})
	if err != nil {
		if strings.HasPrefix(err.Error(), "format ") {
			return &Error{code: ErrCodeUnknownArchive}
		}
		return err
	}
	return nil
}