const MessageContainer = require('../tl/core/MessageContainer');
const TLMessage = require('../tl/core/TLMessage');
const BinaryWriter = require('./BinaryWriter');

const USE_INVOKE_AFTER_WITH = new Set([
    'messages.SendMessage', 'messages.SendMedia', 'messages.SendMultiMedia',
    'messages.ForwardMessages', 'messages.SendInlineBotResult',
]);

class MessagePacker {
    constructor(state, logger) {
        this._state = state;
        this._queue = [];
        this._pendingStates = [];
        this._ready = new Promise(((resolve) => {
            this.setReady = resolve;
        }));
        this._log = logger;
    }

    values() {
        return this._queue;
    }

    clear() {
        this._queue = [];
        this.append(undefined);
    }

    append(state, setReady = true, atStart = false) {
        // We need to check if there is already a `USE_INVOKE_AFTER_WITH` request
        if (state && USE_INVOKE_AFTER_WITH.has(state.request.className)) {
            if (atStart) {
                // Assign `after` for the previously first `USE_INVOKE_AFTER_WITH` request
                for (let i = 0; i < this._queue.length; i++) {
                    if (USE_INVOKE_AFTER_WITH.has(this._queue[i]?.request.className)) {
                        this._queue[i].after = state;
                        break;
                    }
                }
            } else {
                // Assign after for the previous `USE_INVOKE_AFTER_WITH` request
                for (let i = this._queue.length - 1; i >= 0; i--) {
                    if (USE_INVOKE_AFTER_WITH.has(this._queue[i]?.request.className)) {
                        state.after = this._queue[i];
                        break;
                    }
                }
            }
        }

        if (atStart) {
            this._queue.unshift(state);
        } else {
            this._queue.push(state);
        }

        if (setReady) {
            this.setReady(true);
        }

        // 1658238041=MsgsAck, we don't care about MsgsAck here because they never resolve anyway.
        if (state && state.request.CONSTRUCTOR_ID !== 1658238041) {
            this._pendingStates.push(state);
            state.promise
                // Using finally causes triggering `unhandledrejection` event
                .catch(() => {
                })
                .finally(() => {
                    this._pendingStates = this._pendingStates.filter((s) => s !== state);
                });
        }
    }

    prepend(states) {
        states.reverse().forEach((state) => {
            this.append(state, false, true);
        });

        this.setReady(true);
    }

    extend(states) {
        states.forEach((state) => {
            this.append(state, false);
        });
        this.setReady(true);
    }

    async getBeacon(state) {
        const buffer = new BinaryWriter(Buffer.alloc(0));
        const size = state.data.length + TLMessage.SIZE_OVERHEAD;
        if (size <= MessageContainer.MAXIMUM_SIZE) {
            let afterId;
            if (state.after) {
                afterId = state.after.msgId;
            }
            state.msgId = await this._state.writeDataAsMessage(
                buffer, state.data, state.request.classType === 'request', afterId,
            );
            this._log.debug(`Assigned msgId = ${state.msgId} to ${state.request.className
            || state.request.constructor.name}`);

            return buffer.getValue();
        }
        this._log.warn(`Message payload for ${state.request.className
        || state.request.constructor.name} is too long ${state.data.length} and cannot be sent`);
        state.reject('Request Payload is too big');

        return undefined;
    }

    async wait() {
        if (!this._queue.length) {
            this._ready = new Promise(((resolve) => {
                this.setReady = resolve;
            }));
            await this._ready;
        }
    }

    async get() {
        if (!this._queue[this._queue.length - 1]) {
            this._queue = this._queue.filter(Boolean);
            return undefined;
        }
        let data;
        let buffer = new BinaryWriter(Buffer.alloc(0));

        const batch = [];
        let size = 0;

        while (this._queue.length && batch.length <= MessageContainer.MAXIMUM_LENGTH) {
            const state = this._queue.shift();
            if (!state) {
                continue;
            }

            if (state.abortSignal?.aborted) {
                state.reject(new Error('Request aborted'));
                continue;
            }

            size += state.data.length + TLMessage.SIZE_OVERHEAD;
            if (size <= MessageContainer.MAXIMUM_SIZE) {
                let afterId;
                if (state.after) {
                    afterId = state.after.msgId;
                }
                state.msgId = await this._state.writeDataAsMessage(
                    buffer, state.data, state.request.classType === 'request', afterId,
                );
                this._log.debug(`Assigned msgId = ${state.msgId} to ${state.request.className
                || state.request.constructor.name}`);
                batch.push(state);
                continue;
            }

            if (batch.length) {
                this._queue.unshift(state);
                break;
            }

            this._log.warn(`Message payload for ${state.request.className
            || state.request.constructor.name} is too long ${state.data.length} and cannot be sent`);
            state.reject('Request Payload is too big');
            size = 0;
        }
        if (!batch.length) {
            return undefined;
        }
        if (batch.length > 1) {
            const b = Buffer.alloc(8);
            b.writeUInt32LE(MessageContainer.CONSTRUCTOR_ID, 0);
            b.writeInt32LE(batch.length, 4);
            data = Buffer.concat([b, buffer.getValue()]);
            buffer = new BinaryWriter(Buffer.alloc(0));
            const containerId = await this._state.writeDataAsMessage(
                buffer, data, false,
            );
            for (const s of batch) {
                s.containerId = containerId;
            }
        }

        data = buffer.getValue();
        return {
            batch,
            data,
        };
    }
}

module.exports = MessagePacker;