package main

import (
	"github.com/emersion/go-imap/v2"
	"github.com/emersion/go-imap/v2/imapserver"
	"github.com/google/uuid"
)

// UserSession represents a session tied to a specific user.
//
// UserSession implements imapserver.Session. Typically, a UserSession pointer
// is embedded into a larger struct which overrides Login.
type UserSession struct {
	// immutable
	*User
	*EntryPoint

	// may be nil
	*MailboxView
}

var _ imapserver.SessionIMAP4rev2 = (*EntryPoint)(nil)
var _ imapserver.Session = (*EntryPoint)(nil)

type EntryPoint struct {
	*UserSession
	*Server
}

func (sess *EntryPoint) Login(_, token string) (err error) {
	sess.UserSession = &UserSession{
		EntryPoint: sess,
	}
	sess.UserSession.User, err = sess.Server.user(token)
	sess.UserSession.User.sessionMutex.Lock()
	sess.UserSession.User.sessions[sess.UserSession] = struct{}{}
	sess.UserSession.User.sessionMutex.Unlock()
	return err
}

func (sess *EntryPoint) loginRaw(sub uuid.UUID) (err error) {
	sess.UserSession = &UserSession{
		EntryPoint: sess,
	}
	sess.UserSession.User, err = sess.Server.userRaw(sub)
	return err
}

func (sess *UserSession) Append(mboxName string, r imap.LiteralReader, options *imap.AppendOptions) (*imap.AppendData, error) {
	mbox, err := sess.User.mailbox(mboxName)
	if err != nil {
		return nil, err
	}
	view := mbox.NewView()
	defer func() {
		err := view.close()
		if err != nil {
			log("Failed to close view: "+err.Error()+", resource leaks may occur", 1)
		}
	}()
	return view.appendBuffer(r, r.Size(), options)
}

func (sess *UserSession) Close() error {
	if sess == nil || sess.MailboxView == nil {
		return nil
	}
	if sess.User != nil {
		err := sess.Unselect()
		if err != nil {
			return err
		}

		sess.User.sessionMutex.Lock()
		delete(sess.User.sessions, sess)
		if len(sess.User.sessions) == 0 {
			sess.Server.userMutex.Lock()
			delete(sess.server.users, sess.User.sub)
			sess.Server.userMutex.Unlock()
		}
		sess.User.sessionMutex.Unlock()
	}
	return nil
}

func (sess *UserSession) Select(name string, _ *imap.SelectOptions) (*imap.SelectData, error) {
	mbox, err := sess.User.mailbox(name)
	if err != nil {
		return nil, err
	}
	mbox.sessionMutex.Lock()
	mbox.sessions[sess] = struct{}{}
	mbox.sessionMutex.Unlock()
	sess.MailboxView = mbox.NewView()
	return mbox.selectData()
}

func (sess *UserSession) Unselect() error {
	sess.Mailbox.sessionMutex.Lock()
	defer sess.Mailbox.sessionMutex.Unlock()
	delete(sess.Mailbox.sessions, sess)
	if len(sess.Mailbox.sessions) == 0 {
		sess.User.sessionMutex.Lock()
		delete(sess.mailboxes, sess.name)
		sess.User.sessionMutex.Unlock()
	}
	err := sess.close()
	if err != nil {
		return err
	}
	sess.MailboxView = nil
	return nil
}

func (sess *UserSession) Copy(numSet imap.NumSet, destName string) (*imap.CopyData, error) {
	dest, err := sess.mailbox(destName)
	if err != nil {
		return nil, &imap.Error{
			Type: imap.StatusResponseTypeNo,
			Code: imap.ResponseCodeTryCreate,
			Text: "No such mailbox",
		}
	} else if sess.MailboxView != nil && dest == sess.Mailbox {
		return nil, &imap.Error{
			Type: imap.StatusResponseTypeNo,
			Text: "Source and destination mailboxes are identical",
		}
	}

	destView := dest.NewView()
	defer func() {
		err := destView.close()
		if err != nil {
			log("Failed to close view: "+err.Error()+", resource leaks may occur", 1)
		}
	}()

	var sourceUIDs, destUIDs imap.UIDSet
	err = sess.forEach(numSet, func(seqNum uint32, msg *message) error {
		var appendData *imap.AppendData
		appendData, err = destView.copyMsg(msg)
		if err != nil {
			return err
		}
		sourceUIDs.AddNum(msg.uid)
		destUIDs.AddNum(appendData.UID)
		return nil
	})
	if err != nil {
		return nil, err
	}

	return &imap.CopyData{
		UIDValidity: dest.UIDValidity,
		SourceUIDs:  sourceUIDs,
		DestUIDs:    destUIDs,
	}, nil
}

func (sess *UserSession) Move(w *imapserver.MoveWriter, numSet imap.NumSet, destName string) error {
	dest, err := sess.mailbox(destName)
	if err != nil {
		return &imap.Error{
			Type: imap.StatusResponseTypeNo,
			Code: imap.ResponseCodeTryCreate,
			Text: "No such mailbox",
		}
	} else if sess.MailboxView != nil && dest == sess.Mailbox {
		return &imap.Error{
			Type: imap.StatusResponseTypeNo,
			Text: "Source and destination mailboxes are identical",
		}
	}

	destView := dest.NewView()
	defer func() {
		err := destView.close()
		if err != nil {
			log("Failed to close view: "+err.Error()+", resource leaks may occur", 1)
		}
	}()

	var sourceUIDs, destUIDs imap.UIDSet
	err = sess.forEach(numSet, func(seqNum uint32, msg *message) error {
		var appendData *imap.AppendData
		appendData, err = destView.copyMsg(msg)
		if err != nil {
			return err
		}
		sourceUIDs.AddNum(msg.uid)
		destUIDs.AddNum(appendData.UID)
		return nil
	})
	if err != nil {
		return err
	}

	if len(sourceUIDs) != 0 && len(destUIDs) != 0 {
		err = w.WriteCopyData(&imap.CopyData{
			UIDValidity: dest.UIDValidity,
			SourceUIDs:  sourceUIDs,
			DestUIDs:    destUIDs,
		})
		if err != nil {
			return err
		}
	}

	err = sess.Expunge((*imapserver.ExpungeWriter)(w), &sourceUIDs)
	if err != nil {
		return err
	}

	return nil
}

func (sess *UserSession) Poll(w *imapserver.UpdateWriter, allowExpunge bool) error {
	if sess.MailboxView == nil {
		return nil
	}
	return sess.MailboxView.Poll(w, allowExpunge)
}

func (sess *UserSession) Idle(w *imapserver.UpdateWriter, stop <-chan struct{}) error {
	if sess.MailboxView == nil {
		return nil // TODO
	}
	return sess.MailboxView.Idle(w, stop)
}