/*
Copyright 2020 Bruno Windels <bruno@windels.cloud>

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

import {SortedArray} from "../../../observable/list/SortedArray.js";
import {ConnectionError} from "../../error.js";
import {PendingEvent} from "./PendingEvent.js";
import {makeTxnId} from "../../common.js";

export class SendQueue {
    constructor({roomId, storage, hsApi, pendingEvents}) {
        pendingEvents = pendingEvents || [];
        this._roomId = roomId;
        this._storage = storage;
        this._hsApi = hsApi;
        this._pendingEvents = new SortedArray((a, b) => a.queueIndex - b.queueIndex);
        this._pendingEvents.setManyUnsorted(pendingEvents.map(data => this._createPendingEvent(data)));
        this._isSending = false;
        this._offline = false;
        this._roomEncryption = null;
    }

    _createPendingEvent(data, attachments = null) {
        const pendingEvent = new PendingEvent({
            data,
            remove: () => this._removeEvent(pendingEvent),
            emitUpdate: () => this._pendingEvents.set(pendingEvent),
            attachments
        });
        return pendingEvent;
    }

    enableEncryption(roomEncryption) {
        this._roomEncryption = roomEncryption;
    }

    _sendLoop(log) {
        this._isSending = true;
        this._sendLoopLogItem = log.runDetached("send queue flush", async log => {
            try {
                for (let i = 0; i < this._pendingEvents.length; i += 1) {
                    await log.wrap("send event", async log => {
                        const pendingEvent = this._pendingEvents.get(i);
                        log.set("id", pendingEvent.queueIndex);
                        try {
                            await this._sendEvent(pendingEvent, log);
                        } catch(err) {
                            if (err instanceof ConnectionError) {
                                this._offline = true;
                                log.set("offline", true);
                            } else {
                                log.catch(err);
                                pendingEvent.setError(err);
                            }
                        }
                    });
                }
            } finally {
                this._isSending = false;
                this._sendLoopLogItem = null;
            }
        });
    }

    async _sendEvent(pendingEvent, log) {
        if (pendingEvent.needsUpload) {
            await log.wrap("upload attachments", log => pendingEvent.uploadAttachments(this._hsApi, log));
            await this._tryUpdateEvent(pendingEvent);
        }
        if (pendingEvent.needsEncryption) {
            pendingEvent.setEncrypting();
            const {type, content} = await log.wrap("encrypt", log => this._roomEncryption.encrypt(
                pendingEvent.eventType, pendingEvent.content, this._hsApi, log));
            pendingEvent.setEncrypted(type, content);
            await this._tryUpdateEvent(pendingEvent);
        }
        if (pendingEvent.needsSending) {
            await pendingEvent.send(this._hsApi, log);
            
            await this._tryUpdateEvent(pendingEvent);
        }
    }

    removeRemoteEchos(events, txn) {
        const removed = [];
        for (const event of events) {
            const txnId = event.unsigned && event.unsigned.transaction_id;
            let idx;
            if (txnId) {
                idx = this._pendingEvents.array.findIndex(pe => pe.txnId === txnId);
            } else {
                idx = this._pendingEvents.array.findIndex(pe => pe.remoteId === event.event_id);
            }
            if (idx !== -1) {
                const pendingEvent = this._pendingEvents.get(idx);
                txn.pendingEvents.remove(pendingEvent.roomId, pendingEvent.queueIndex);
                removed.push(pendingEvent);
            }
        }
        return removed;
    }

    async _removeEvent(pendingEvent) {
        const idx = this._pendingEvents.array.indexOf(pendingEvent);
        if (idx !== -1) {
            const txn = this._storage.readWriteTxn([this._storage.storeNames.pendingEvents]);
            try {
                txn.pendingEvents.remove(pendingEvent.roomId, pendingEvent.queueIndex);
            } catch (err) {
                txn.abort();
            }
            await txn.complete();
            this._pendingEvents.remove(idx);
        }
        pendingEvent.dispose();
    }

    emitRemovals(pendingEvents) {
        for (const pendingEvent of pendingEvents) {
            const idx = this._pendingEvents.array.indexOf(pendingEvent);
            if (idx !== -1) {
                this._pendingEvents.remove(idx);
            }
            pendingEvent.dispose();
        }
    }

    resumeSending(parentLog) {
        this._offline = false;
        if (this._pendingEvents.length) {
            parentLog.wrap("resumeSending", log => {
                log.set("id", this._roomId);
                log.set("pendingEvents", this._pendingEvents.length);
                if (!this._isSending) {
                    this._sendLoop(log);
                }
                if (this._sendLoopLogItem) {
                    log.refDetached(this._sendLoopLogItem);
                }
            });
        }
    }

    async enqueueEvent(eventType, content, attachments, log) {
        const pendingEvent = await this._createAndStoreEvent(eventType, content, attachments);
        this._pendingEvents.set(pendingEvent);
        log.set("queueIndex", pendingEvent.queueIndex);
        log.set("pendingEvents", this._pendingEvents.length);
        if (!this._isSending && !this._offline) {
            this._sendLoop(log);
        }
        if (this._sendLoopLogItem) {
            log.refDetached(this._sendLoopLogItem);
        }
    }

    get pendingEvents() {
        return this._pendingEvents;
    }

    async _tryUpdateEvent(pendingEvent) {
        const txn = this._storage.readWriteTxn([this._storage.storeNames.pendingEvents]);
        try {
            // pendingEvent might have been removed already here
            // by a racing remote echo, so check first so we don't recreate it
            if (await txn.pendingEvents.exists(pendingEvent.roomId, pendingEvent.queueIndex)) {
                txn.pendingEvents.update(pendingEvent.data);
            }
        } catch (err) {
            txn.abort();
            throw err;
        }
        await txn.complete();
    }

    async _createAndStoreEvent(eventType, content, attachments) {
        const txn = this._storage.readWriteTxn([this._storage.storeNames.pendingEvents]);
        let pendingEvent;
        try {
            const pendingEventsStore = txn.pendingEvents;
            const maxQueueIndex = await pendingEventsStore.getMaxQueueIndex(this._roomId) || 0;
            const queueIndex = maxQueueIndex + 1;
            pendingEvent = this._createPendingEvent({
                roomId: this._roomId,
                queueIndex,
                eventType,
                content,
                txnId: makeTxnId(),
                needsEncryption: !!this._roomEncryption,
                needsUpload: !!attachments
            }, attachments);
            pendingEventsStore.add(pendingEvent.data);
        } catch (err) {
            txn.abort();
            throw err;
        }
        await txn.complete();
        return pendingEvent;
    }

    dispose() {
        for (const pe of this._pendingEvents) {
            pe.dispose();
        }
    }
}