package common

import (
	"fmt"
	"os"
	"path"
	"sync"
	"time"

	"github.com/drakkan/sftpgo/v2/dataprovider"
	"github.com/drakkan/sftpgo/v2/logger"
	"github.com/drakkan/sftpgo/v2/util"
)

var (
	// RetentionChecks is the list of active quota scans
	RetentionChecks ActiveRetentionChecks
)

// ActiveRetentionChecks holds the active quota scans
type ActiveRetentionChecks struct {
	sync.RWMutex
	Checks []RetentionCheck
}

// Get returns the active retention checks
func (c *ActiveRetentionChecks) Get() []RetentionCheck {
	c.RLock()
	defer c.RUnlock()

	checks := make([]RetentionCheck, 0, len(c.Checks))
	for _, check := range c.Checks {
		foldersCopy := make([]FolderRetention, len(check.Folders))
		copy(foldersCopy, check.Folders)
		checks = append(checks, RetentionCheck{
			Username:  check.Username,
			StartTime: check.StartTime,
			Folders:   foldersCopy,
		})
	}
	return checks
}

// Add a new retention check, returns nil if a retention check for the given
// username is already active. The returned result can be used to start the check
func (c *ActiveRetentionChecks) Add(check RetentionCheck, user *dataprovider.User) *RetentionCheck {
	c.Lock()
	defer c.Unlock()

	for _, val := range c.Checks {
		if val.Username == user.Username {
			return nil
		}
	}
	// we silently ignore file patterns
	user.Filters.FilePatterns = nil
	conn := NewBaseConnection("", "", "", "", *user)
	conn.ID = fmt.Sprintf("retention_check_%v", user.Username)
	check.Username = user.Username
	check.StartTime = util.GetTimeAsMsSinceEpoch(time.Now())
	check.conn = conn
	check.updateUserPermissions()
	c.Checks = append(c.Checks, check)

	return &check
}

// remove a user from the ones with active retention checks
// and returns true if the user is removed
func (c *ActiveRetentionChecks) remove(username string) bool {
	c.Lock()
	defer c.Unlock()

	for idx, check := range c.Checks {
		if check.Username == username {
			lastIdx := len(c.Checks) - 1
			c.Checks[idx] = c.Checks[lastIdx]
			c.Checks = c.Checks[:lastIdx]
			return true
		}
	}

	return false
}

// FolderRetention defines the retention policy for the specified directory path
type FolderRetention struct {
	// Path is the exposed virtual directory path, if no other specific retention is defined,
	// the retention applies for sub directories too. For example if retention is defined
	// for the paths "/" and "/sub" then the retention for "/" is applied for any file outside
	// the "/sub" directory
	Path string `json:"path"`
	// Retention time in hours. 0 means exclude this path
	Retention int `json:"retention"`
	// DeleteEmptyDirs defines if empty directories will be deleted.
	// The user need the delete permission
	DeleteEmptyDirs bool `json:"delete_empty_dirs,omitempty"`
	// IgnoreUserPermissions defines if delete files even if the user does not have the delete permission.
	// The default is "false" which means that files will be skipped if the user does not have the permission
	// to delete them. This applies to sub directories too.
	IgnoreUserPermissions bool `json:"ignore_user_permissions,omitempty"`
}

func (f *FolderRetention) isValid() error {
	f.Path = path.Clean(f.Path)
	if !path.IsAbs(f.Path) {
		return util.NewValidationError(fmt.Sprintf("folder retention: invalid path %#v, please specify an absolute POSIX path",
			f.Path))
	}
	if f.Retention < 0 {
		return util.NewValidationError(fmt.Sprintf("invalid folder retention %v, it must be greater or equal to zero",
			f.Retention))
	}
	return nil
}

// RetentionCheck defines an active retention check
type RetentionCheck struct {
	// Username to which the retention check refers
	Username string `json:"username"`
	// retention check start time as unix timestamp in milliseconds
	StartTime int64 `json:"start_time"`
	// affected folders
	Folders []FolderRetention `json:"folders"`
	// Cleanup results
	conn *BaseConnection
}

// Validate returns an error if the specified folders are not valid
func (c *RetentionCheck) Validate() error {
	folderPaths := make(map[string]bool)
	nothingToDo := true
	for idx := range c.Folders {
		f := &c.Folders[idx]
		if err := f.isValid(); err != nil {
			return err
		}
		if f.Retention > 0 {
			nothingToDo = false
		}
		if _, ok := folderPaths[f.Path]; ok {
			return util.NewValidationError(fmt.Sprintf("duplicated folder path %#v", f.Path))
		}
		folderPaths[f.Path] = true
	}
	if nothingToDo {
		return util.NewValidationError("nothing to delete!")
	}
	return nil
}

func (c *RetentionCheck) updateUserPermissions() {
	for _, folder := range c.Folders {
		if folder.IgnoreUserPermissions {
			c.conn.User.Permissions[folder.Path] = []string{dataprovider.PermAny}
		}
	}
}

func (c *RetentionCheck) getFolderRetention(folderPath string) (FolderRetention, error) {
	dirsForPath := util.GetDirsForVirtualPath(folderPath)
	for _, dirPath := range dirsForPath {
		for _, folder := range c.Folders {
			if folder.Path == dirPath {
				return folder, nil
			}
		}
	}

	return FolderRetention{}, fmt.Errorf("unable to find folder retention for %#v", folderPath)
}

func (c *RetentionCheck) removeFile(virtualPath string, info os.FileInfo) error {
	fs, fsPath, err := c.conn.GetFsAndResolvedPath(virtualPath)
	if err != nil {
		return err
	}
	return c.conn.RemoveFile(fs, fsPath, virtualPath, info)
}

func (c *RetentionCheck) cleanupFolder(folderPath string) error {
	cleanupPerms := []string{dataprovider.PermListItems, dataprovider.PermDelete}
	if !c.conn.User.HasPerms(cleanupPerms, folderPath) {
		c.conn.Log(logger.LevelInfo, "user %#v does not have permissions to check retention on %#v, retention check skipped",
			c.conn.User, folderPath)
		return nil
	}

	folderRetention, err := c.getFolderRetention(folderPath)
	if err != nil {
		c.conn.Log(logger.LevelError, "unable to get folder retention for path %#v", folderPath)
		return err
	}
	if folderRetention.Retention == 0 {
		c.conn.Log(logger.LevelDebug, "retention check skipped for folder %#v, retention is set to 0", folderPath)
		return nil
	}
	c.conn.Log(logger.LevelDebug, "start retention check for folder %#v, retention: %v hours, delete empty dirs? %v, ignore user perms? %v",
		folderPath, folderRetention.Retention, folderRetention.DeleteEmptyDirs, folderRetention.IgnoreUserPermissions)
	files, err := c.conn.ListDir(folderPath)
	if err != nil {
		if err == c.conn.GetNotExistError() {
			c.conn.Log(logger.LevelDebug, "folder %#v does not exist, retention check skipped", folderPath)
			return nil
		}
		c.conn.Log(logger.LevelWarn, "unable to list directory %#v", folderPath)
		return err
	}
	deletedFiles := 0
	deletedSize := int64(0)
	for _, info := range files {
		virtualPath := path.Join(folderPath, info.Name())
		if info.IsDir() {
			if err := c.cleanupFolder(virtualPath); err != nil {
				c.conn.Log(logger.LevelWarn, "unable to cleanup folder %#v: %v", virtualPath, err)
				return err
			}
		} else {
			retentionTime := info.ModTime().Add(time.Duration(folderRetention.Retention) * time.Hour)
			if retentionTime.Before(time.Now()) {
				if err := c.removeFile(virtualPath, info); err != nil {
					c.conn.Log(logger.LevelWarn, "unable to remove file %#v, retention %v: %v",
						virtualPath, retentionTime, err)
					return err
				}
				c.conn.Log(logger.LevelDebug, "removed file %#v, modification time: %v, retention: %v hours, retention time: %v",
					virtualPath, info.ModTime(), folderRetention.Retention, retentionTime)
				deletedFiles++
				deletedSize += info.Size()
			}
		}
	}

	if folderRetention.DeleteEmptyDirs {
		c.checkEmptyDirRemoval(folderPath)
	}
	c.conn.Log(logger.LevelDebug, "retention check completed for folder %#v, deleted files: %v, deleted size: %v bytes",
		folderPath, deletedFiles, deletedSize)

	return nil
}

func (c *RetentionCheck) checkEmptyDirRemoval(folderPath string) {
	if folderPath != "/" && c.conn.User.HasPerm(dataprovider.PermDelete, path.Dir(folderPath)) {
		files, err := c.conn.ListDir(folderPath)
		if err == nil && len(files) == 0 {
			err = c.conn.RemoveDir(folderPath)
			c.conn.Log(logger.LevelDebug, "tryed to remove empty dir %#v, error: %v", folderPath, err)
		}
	}
}

// Start starts the retention check
func (c *RetentionCheck) Start() {
	c.conn.Log(logger.LevelInfo, "retention check started")
	defer RetentionChecks.remove(c.conn.User.Username)
	defer c.conn.CloseFS() //nolint:errcheck

	for _, folder := range c.Folders {
		if folder.Retention > 0 {
			if err := c.cleanupFolder(folder.Path); err != nil {
				c.conn.Log(logger.LevelWarn, "retention check failed, unable to cleanup folder %#v", folder.Path)
				return
			}
		}
	}

	c.conn.Log(logger.LevelInfo, "retention check completed")
}