//go:build !windows && !darwin && !android && !ios && !js

package wastebasket

import (
	"fmt"
	"io/fs"
	"os"
	"os/user"
	"path/filepath"
	"strings"
	"sync"
	"time"

	"github.com/Bios-Marcel/wastebasket/internal"
)

var (
	// cachedInformation makes sure we don't constantly check for the
	// directory and which drive it is on again.
	cachedInformation = &cache{
		init: &sync.Once{},
	}
)

type cache struct {
	// path is the path to the trash dir, for example
	//   /home/marcel/.local/share/Trash.
	path string
	// topdir is the closes mountpoint of `path`.
	topdir string

	init *sync.Once
	err  error
}

func getCache() (*cache, error) {
	cachedInformation.init.Do(func() {
		var homeTrashDir string
		// On some big distros, such as Ubuntu for example, this variable isn't
		// set. Instead, we will fallback to what Ubuntu does for now.
		if dataHome := os.Getenv("XDG_DATA_HOME"); dataHome == "" {
			homeDir, err := os.UserHomeDir()
			if err != nil {
				cachedInformation.err = err
				return
			}

			homeTrashDir = filepath.Join(homeDir, ".local", "share", "Trash")
		} else {
			homeTrashDir = filepath.Join(dataHome, "Trash")
		}

		cachedInformation.path = homeTrashDir

		mounts, err := internal.Mounts()
		if err != nil {
			cachedInformation.err = err
		} else {
			homeTopdir, err := topdir(mounts, cachedInformation.path)
			if err != nil {
				cachedInformation.err = err
			} else {
				cachedInformation.err = nil
				cachedInformation.topdir = homeTopdir
			}
		}

	})

	return cachedInformation, cachedInformation.err
}

func topdir(potentialTopdirs []string, path string) (string, error) {
	var matchingDir string
	for _, dir := range potentialTopdirs {
		// Technically mounts can be nested, so we can have more than one
		// match, but want the deepest possible match.
		if strings.HasPrefix(path, dir) && len(dir) > len(matchingDir) {
			matchingDir = dir
		}
	}

	return matchingDir, nil
}

func Trash(paths ...string) error {
	// RFC3339 defined in the time package contains the timezone offset, which
	// isn't defined by the spec and causes issues in some trash tools, such
	// as trash-cli.
	deletionDate := time.Now().Format("2006-01-02T15:04:05")
	cache, err := getCache()
	if err != nil {
		return fmt.Errorf("error determining user trash directory: %w", err)
	}

	mounts, err := internal.Mounts()
	if err != nil {
		return err
	}

	for _, absPath := range paths {
		var err error
		absPath, err = filepath.Abs(absPath)
		if err != nil {
			return err
		}

		pathTopdir, err := topdir(mounts, absPath)
		if err != nil {
			return err
		}

		// We only support absolute filenames in the home trash. For
		// topdirs, we use relative paths. This allows us to move a
		// mount, while still keeping trash files recoverable.
		var pathForTrashInfo string

		var trashDir, filesDir, infoDir string
		// Deleting accross partitions / mounts
		if cache.topdir != pathTopdir {
			// While getTopDir won't return an empty string with its current
			// impl, this can change in the future, so beteter be safe than
			// sorry.
			if pathTopdir != "" {
				var uid string
				if currentUser, err := user.Current(); err != nil {
					return err
				} else {
					uid = currentUser.Uid
				}

				trashDir = filepath.Join(pathTopdir, ".Trash")

				var useFallbackTopdirTrash bool
				if trashDirStat, err := os.Stat(trashDir); err != nil {
					if !os.IsNotExist(err) {
						return err
					}
					useFallbackTopdirTrash = true
				} else {
					if trashDirStat.Mode()&fs.ModeSticky != 0 {
						// If the topdir trash directory contains a trash for all
						// users, it needs to have the sticky bit set. This is only
						// required for .Trash though, not for .Trash-$uid.
						useFallbackTopdirTrash = true
					} else if trashDirStat.Mode()&os.ModeSymlink != 0 {
						// Symlinks must not be used as per spec.
						useFallbackTopdirTrash = true
					}
				}

				pathForTrashInfo, err = filepath.Rel(pathTopdir, absPath)
				if err != nil {
					return err
				}

				if !useFallbackTopdirTrash {
					filesDir = filepath.Join(trashDir, uid, "files")
					infoDir = filepath.Join(trashDir, uid, "info")
				} else {
					// If .Trash doesn't exist, we need to check for .Trash-$uid
					// and create it if it doesn't exist. The spec however
					// doesn't indicate that we should do the same with .Trash.
					trashDir = filepath.Join(pathTopdir, ".Trash-"+uid)
					filesDir = filepath.Join(trashDir, "files")
					infoDir = filepath.Join(trashDir, "info")
				}

			}
		}

		if trashDir == "" {
			// Fallback to home trash.
			trashDir = cache.path
			filesDir = filepath.Join(trashDir, "files")
			infoDir = filepath.Join(trashDir, "info")

			// Hometrash supports both relative and absolute paths.
			if trashParent := filepath.Dir(trashDir); strings.HasPrefix(absPath, trashParent) {
				relPath, err := filepath.Rel(trashParent, absPath)
				if err != nil {
					return err
				}
				pathForTrashInfo = relPath
			} else {
				pathForTrashInfo = absPath
			}
		}

		if err := os.MkdirAll(filesDir, 0700); err != nil && !os.IsExist(err) {
			return fmt.Errorf("error creating directory '%s': %w", filesDir, err)
		}
		if err := os.MkdirAll(infoDir, 0700); err != nil && !os.IsExist(err) {
			return fmt.Errorf("error creating directory '%s': %w", infoDir, err)
		}

		baseName := filepath.Base(absPath)
		trashedFilePath := filepath.Join(filesDir, baseName)
		trashedFileInfoPath := filepath.Join(infoDir, baseName) + ".trashinfo"

		// We need to check whether the trash already contains a file with this
		// name, since deleted files from different directories often have the
		// same name. An example would be .gitignore files, they always have
		// the same basename and therefore always the same trash path.
		// We simply count up in this case. Since we've got the info file, we
		// can map back to the original name later on.

		var infoFileHandle *os.File
		if exists, err := internal.FileExists(trashedFilePath); err != nil {
			return err
		} else if !exists {
			// We save ourselves the FileExists check, as we can combine it
			// with the opening of the file handle. This is a performance
			// optimisation.
			infoFileHandle, err = os.OpenFile(trashedFileInfoPath, os.O_EXCL|os.O_CREATE|os.O_WRONLY, 0600)
			if err != nil {
				if !os.IsExist(err) {
					return err
				}
			}

			// While we close manually later, we want to prevent a leak.
			defer infoFileHandle.Close()
		}

		// If there isn't a valid info file handle yet, it means that one
		// of the two file names were already in use, requiring us to find
		// two unique filenames eiter way.
		if infoFileHandle == nil {
			extension := filepath.Ext(baseName)
			baseNameNoExtension := strings.TrimSuffix(baseName, extension)
			for i := uint64(1); i != 0; i = i + 1 {
				newBaseName := fmt.Sprintf("%s.%d%s", baseNameNoExtension, i, extension)

				// The names of both files must always be the same, putting
				// aside the .trashinfo extension.
				trashedFilePath = filepath.Join(filesDir, newBaseName)
				if exists, err := internal.FileExists(trashedFilePath); err != nil || exists {
					continue
				}
				infoFileHandle, err = os.OpenFile(filepath.Join(infoDir, newBaseName+".trashinfo"), os.O_EXCL|os.O_CREATE|os.O_WRONLY, 0600)
				if err != nil {
					if os.IsExist(err) {
						continue
					}
					return err
				}

				defer infoFileHandle.Close()

				// We found a valid name, where neither the file itself, nor
				// the trashinfo file exist.
				break
			}
		}

		if err := os.Rename(absPath, trashedFilePath); err != nil {
			// We save ourselvse the exists check at the start of the loop, as
			// deleting non existing files probably does not happen that often.
			if os.IsNotExist(err) {
				// Since we already create the info file, we will have to manually delete it again.
				name := infoFileHandle.Name()
				infoFileHandle.Close()
				// We ignore the error here, it isn't super important
				os.Remove(name)
				continue
			}

			// All special treatment failed, return original os.Rename error
			return err
		}

		if _, err = infoFileHandle.WriteString(fmt.Sprintf("[Trash Info]\nPath=%s\nDeletionDate=%s\n", internal.EscapeUrl(pathForTrashInfo), deletionDate)); err != nil {
			return err
		}
	}

	return nil
}

func Empty() error {
	cache, err := getCache()
	if err != nil {
		return err
	}

	if err := internal.RemoveAllIfExists(cache.path); err != nil {
		return err
	}

	mounts, err := internal.Mounts()
	if err != nil {
		return err
	}

	currentUser, err := user.Current()
	if err != nil {
		return err
	}
	uid := currentUser.Uid

	for _, mount := range mounts {
		if err := internal.RemoveAllIfExists(filepath.Join(mount, ".Trash", uid)); err != nil && !os.IsPermission(err) {
			return err
		}
		if err := internal.RemoveAllIfExists(filepath.Join(mount, fmt.Sprintf(".Trash-%s", uid))); err != nil && !os.IsPermission(err) {
			return err
		}
	}

	return nil
}