// Copyright (c) 2022 Proton AG
//
// This file is part of Proton Mail Bridge.
//
// Proton Mail Bridge is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Proton Mail Bridge is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Proton Mail Bridge. If not, see <https://www.gnu.org/licenses/>.

package store

import (
	"bytes"
	"encoding/json"
	"io"
	"net/mail"
	"net/textproto"
	"strings"

	"github.com/ProtonMail/gopenpgp/v2/crypto"
	"github.com/ProtonMail/proton-bridge/v2/internal/store/cache"
	"github.com/ProtonMail/proton-bridge/v2/pkg/pmapi"
	"github.com/pkg/errors"
	"github.com/sirupsen/logrus"
	bolt "go.etcd.io/bbolt"
)

// CreateDraft creates draft with attachments.
// If `attachedPublicKey` is passed, it's added to attachments.
// Both draft and attachments are encrypted with passed `kr` key.
func (store *Store) CreateDraft(
	kr *crypto.KeyRing,
	message *pmapi.Message,
	attachmentReaders []io.Reader,
	attachedPublicKey,
	attachedPublicKeyName string,
	parentID string,
) (*pmapi.Message, []*pmapi.Attachment, error) {
	attachments := store.prepareDraftAttachments(message, attachmentReaders, attachedPublicKey, attachedPublicKeyName)

	if err := encryptDraft(kr, message, attachments); err != nil {
		return nil, nil, errors.Wrap(err, "failed to encrypt draft")
	}

	if ok, err := store.checkDraftTotalSize(message, attachments); err != nil {
		return nil, nil, err
	} else if !ok {
		return nil, nil, errors.New("message is too large")
	}

	draftAction := store.getDraftAction(message)
	draft, err := store.client().CreateDraft(exposeContextForSMTP(), message, parentID, draftAction)
	if err != nil {
		return nil, nil, errors.Wrap(err, "failed to create draft")
	}

	// Do poll only when call to API succeeded.
	defer store.eventLoop.pollNow()

	createdAttachments := []*pmapi.Attachment{}
	for _, att := range attachments {
		att.attachment.MessageID = draft.ID

		createdAttachment, err := store.client().CreateAttachment(exposeContextForSMTP(), att.attachment, att.encReader, att.sigReader)
		if err != nil {
			return nil, nil, errors.Wrap(err, "failed to create attachment")
		}
		createdAttachments = append(createdAttachments, createdAttachment)
	}

	return draft, createdAttachments, nil
}

type draftAttachment struct {
	attachment *pmapi.Attachment
	reader     io.Reader
	sigReader  io.Reader
	encReader  io.Reader
}

func (store *Store) prepareDraftAttachments(
	message *pmapi.Message,
	attachmentReaders []io.Reader,
	attachedPublicKey,
	attachedPublicKeyName string,
) []*draftAttachment {
	attachments := []*draftAttachment{}
	for idx, attachment := range message.Attachments {
		attachments = append(attachments, &draftAttachment{
			attachment: attachment,
			reader:     attachmentReaders[idx],
		})
	}

	message.Attachments = nil

	if attachedPublicKey != "" {
		publicKeyAttachment := &pmapi.Attachment{
			Name:     attachedPublicKeyName + ".asc",
			MIMEType: "application/pgp-keys",
			Header:   textproto.MIMEHeader{},
		}
		attachments = append(attachments, &draftAttachment{
			attachment: publicKeyAttachment,
			reader:     strings.NewReader(attachedPublicKey),
		})
	}

	return attachments
}

func encryptDraft(kr *crypto.KeyRing, message *pmapi.Message, attachments []*draftAttachment) error {
	// Since this is a draft, we don't need to sign it.
	if err := message.Encrypt(kr, nil); err != nil {
		return errors.Wrap(err, "failed to encrypt message")
	}

	for _, att := range attachments {
		attachment := att.attachment
		attachmentBody, err := io.ReadAll(att.reader)
		if err != nil {
			return errors.Wrap(err, "failed to read attachment")
		}

		r := bytes.NewReader(attachmentBody)
		sigReader, err := attachment.DetachedSign(kr, r)
		if err != nil {
			return errors.Wrap(err, "failed to sign attachment")
		}
		att.sigReader = sigReader

		r = bytes.NewReader(attachmentBody)
		encReader, err := attachment.Encrypt(kr, r)
		if err != nil {
			return errors.Wrap(err, "failed to encrypt attachment")
		}
		att.encReader = encReader

		att.reader = nil
	}
	return nil
}

func (store *Store) checkDraftTotalSize(message *pmapi.Message, attachments []*draftAttachment) (bool, error) {
	maxUpload, err := store.GetMaxUpload()
	if err != nil {
		return false, err
	}

	var attSize int64
	for _, att := range attachments {
		b, err := io.ReadAll(att.encReader)
		if err != nil {
			return false, err
		}
		attSize += int64(len(b))
		att.encReader = bytes.NewBuffer(b)
	}

	return int64(len(message.Body))+attSize <= maxUpload, nil
}

func (store *Store) getDraftAction(message *pmapi.Message) int {
	// If not a reply, must be a forward.
	if len(message.Header["In-Reply-To"]) == 0 {
		return pmapi.DraftActionForward
	}
	return pmapi.DraftActionReply
}

// SendMessage sends the message.
func (store *Store) SendMessage(messageID string, req *pmapi.SendMessageReq) error {
	defer store.eventLoop.pollNow()
	_, _, err := store.client().SendMessage(exposeContextForSMTP(), messageID, req)
	return err
}

// getAllMessageIDs returns all API IDs of messages in the local database.
func (store *Store) getAllMessageIDs() (apiIDs []string, err error) {
	err = store.db.View(func(tx *bolt.Tx) error {
		b := tx.Bucket(metadataBucket)
		return b.ForEach(func(k, v []byte) error {
			apiIDs = append(apiIDs, string(k))
			return nil
		})
	})
	return
}

// getMessageFromDB returns pmapi struct of message by API ID.
func (store *Store) getMessageFromDB(apiID string) (msg *pmapi.Message, err error) {
	err = store.db.View(func(tx *bolt.Tx) error {
		msg, err = store.txGetMessage(tx, apiID)
		return err
	})

	return
}

func (store *Store) txGetMessage(tx *bolt.Tx, apiID string) (*pmapi.Message, error) {
	return store.txGetMessageFromBucket(tx.Bucket(metadataBucket), apiID)
}

func (store *Store) txGetMessageFromBucket(b *bolt.Bucket, apiID string) (*pmapi.Message, error) {
	msgb := b.Get([]byte(apiID))
	if msgb == nil {
		return nil, ErrNoSuchAPIID
	}
	msg := &pmapi.Message{}
	if err := json.Unmarshal(msgb, msg); err != nil {
		return nil, err
	}
	return msg, nil
}

func (store *Store) txPutMessage(metaBucket *bolt.Bucket, onlyMeta *pmapi.Message) error {
	b, err := json.Marshal(onlyMeta)
	if err != nil {
		return errors.Wrap(err, "cannot marshall metadata")
	}
	err = metaBucket.Put([]byte(onlyMeta.ID), b)
	if err != nil {
		return errors.Wrap(err, "cannot add to metadata bucket")
	}
	return nil
}

// createOrUpdateMessageEvent is helper to create only one message with
// createOrUpdateMessagesEvent.
func (store *Store) createOrUpdateMessageEvent(msg *pmapi.Message) error {
	return store.createOrUpdateMessagesEvent([]*pmapi.Message{msg})
}

// createOrUpdateMessagesEvent tries to create or update messages in database.
// This function is optimised for insertion of many messages at once.
// It calls createLabelsIfMissing if needed.
func (store *Store) createOrUpdateMessagesEvent(msgs []*pmapi.Message) error { //nolint:funlen
	store.log.WithField("msgs", msgs).Trace("Creating or updating messages in the store")

	// Strip non meta first to reduce memory (no need to keep all old msg ID data during update).
	err := store.db.View(func(tx *bolt.Tx) error {
		b := tx.Bucket(metadataBucket)
		for _, msg := range msgs {
			clearNonMetadata(msg)
			txUpdateMetadataFromDB(b, msg, store.log)
		}
		return nil
	})
	if err != nil {
		return err
	}

	affectedLabels := map[string]bool{}
	for _, m := range msgs {
		for _, l := range m.LabelIDs {
			affectedLabels[l] = true
		}
	}
	if err = store.createLabelsIfMissing(affectedLabels); err != nil {
		return err
	}

	// Updating metadata and mailboxes is not atomic, but this is OK.
	// The worst case scenario is we have metadata but not updated mailboxes
	// which is OK as without information in mailboxes IMAP we will never ask
	// for metadata. Also, when doing the operation again, it will simply
	// update the metadata.
	// The reason to split is efficiency--it's more memory efficient.

	// Update metadata.
	err = store.db.Update(func(tx *bolt.Tx) error {
		metaBucket := tx.Bucket(metadataBucket)
		for _, msg := range msgs {
			err := store.txPutMessage(metaBucket, msg)
			if err != nil {
				return err
			}
		}
		return nil
	})
	if err != nil {
		return err
	}

	// Update mailboxes.
	err = store.db.Update(func(tx *bolt.Tx) error {
		for _, a := range store.addresses {
			if err := a.txCreateOrUpdateMessages(tx, msgs); err != nil {
				store.log.WithError(err).Error("cannot update maiboxes")
				return errors.Wrap(err, "cannot add to mailboxes bucket")
			}
		}
		return nil
	})
	if err != nil {
		return err
	}

	// Notify the cacher that it should start caching messages.
	if cache.IsOnDiskCache(store.cache) {
		for _, msg := range msgs {
			store.msgCachePool.newJob(msg.ID)
		}
	}

	return nil
}

// clearNonMetadata to not allow to store decrypted or encrypted data i.e. body
// and attachments.
func clearNonMetadata(onlyMeta *pmapi.Message) {
	onlyMeta.Body = ""
	onlyMeta.Attachments = nil
}

// txUpdateMetadataFromDB changes the the onlyMeta data.
// If there is stored message in metaBucket the size, header and MIMEType are
// not changed if already set. To change these:
// * size must be updated by Message.SetSize
// * contentType and header must be updated by bodystructure.
func txUpdateMetadataFromDB(metaBucket *bolt.Bucket, onlyMeta *pmapi.Message, log *logrus.Entry) {
	msgb := metaBucket.Get([]byte(onlyMeta.ID))
	if msgb == nil {
		return
	}

	// It is faster to unmarshal only the needed items.
	stored := &struct {
		Size     int64
		Header   string
		MIMEType string
	}{}
	if err := json.Unmarshal(msgb, stored); err != nil {
		log.WithError(err).
			Error("Fail to unmarshal from DB, metadata will be overwritten")
		return
	}

	// Keep content type.
	onlyMeta.MIMEType = stored.MIMEType
	if stored.Header != "" && stored.Header != "(No Header)" {
		tmpMsg, err := mail.ReadMessage(
			strings.NewReader(stored.Header + "\r\n\r\n"),
		)
		if err == nil {
			onlyMeta.Header = tmpMsg.Header
		} else {
			log.WithError(err).
				Error("Fail to parse, the header will be overwritten")
		}
	}
}

// deleteMessageEvent is helper to delete only one message with deleteMessagesEvent.
func (store *Store) deleteMessageEvent(apiID string) error {
	return store.deleteMessagesEvent([]string{apiID})
}

// deleteMessagesEvent deletes the message from metadata and all mailbox buckets.
func (store *Store) deleteMessagesEvent(apiIDs []string) error {
	for _, messageID := range apiIDs {
		if err := store.cache.Rem(store.UserID(), messageID); err != nil {
			logrus.WithError(err).Error("Failed to remove message from cache")
		}
	}

	return store.db.Update(func(tx *bolt.Tx) error {
		for _, apiID := range apiIDs {
			if err := tx.Bucket(metadataBucket).Delete([]byte(apiID)); err != nil {
				return err
			}

			for _, a := range store.addresses {
				if err := a.txDeleteMessage(tx, apiID); err != nil {
					return err
				}
			}
		}
		return nil
	})
}

func (store *Store) isMessageADraft(apiID string) bool {
	msg, err := store.getMessageFromDB(apiID)
	if err != nil {
		store.log.WithError(err).Warn("Cannot decide wheather message is draff")
		return false
	}

	return msg.IsDraft()
}