"use strict";
var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
    return new (P || (P = Promise))(function (resolve, reject) {
        function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
        function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
        step((generator = generator.apply(thisArg, _arguments || [])).next());
    });
};
Object.defineProperty(exports, "__esModule", { value: true });
const assert = require("assert");
class Deferred {
    constructor() {
        this.promise = new Promise((resolve, reject) => {
            this.reject = reject;
            this.resolve = resolve;
        });
    }
}
/**
 * Error message
 */
exports.endOfStream = 'End-Of-Stream';
class StreamReader {
    constructor(s) {
        this.s = s;
        this.endOfStream = false;
        /**
         * Store peeked data
         * @type {Array}
         */
        this.peekQueue = [];
        if (!s.read || !s.once) {
            throw new Error('Expected an instance of stream.Readable');
        }
        this.s.once('end', () => this.reject(new Error(exports.endOfStream)));
        this.s.once('error', err => this.reject(err));
        this.s.once('close', () => this.reject(new Error('Stream closed')));
    }
    /**
     * Read ahead (peek) from stream. Subsequent read or peeks will return the same data
     * @param buffer Buffer to store data read from stream in
     * @param offset Offset buffer
     * @param length Number of bytes to read
     * @param position Source offset
     * @returns {any}
     */
    peek(buffer, offset, length) {
        return __awaiter(this, void 0, void 0, function* () {
            const bytesRead = yield this.read(buffer, offset, length);
            this.peekQueue.push(buffer.slice(offset, offset + bytesRead)); // Put read data back to peek buffer
            return bytesRead;
        });
    }
    /**
     * Read chunk from stream
     * @param buffer Target buffer to store data read from stream in
     * @param offset Offset of target buffer
     * @param length Number of bytes to read
     * @returns {any}
     */
    read(buffer, offset, length) {
        return __awaiter(this, void 0, void 0, function* () {
            if (length === 0) {
                return 0;
            }
            if (this.peekQueue.length === 0 && this.endOfStream) {
                throw new Error(exports.endOfStream);
            }
            let remaining = length;
            let bytesRead = 0;
            // consume peeked data first
            while (this.peekQueue.length > 0 && remaining > 0) {
                const peekData = this.peekQueue.pop(); // Front of queue
                const lenCopy = Math.min(peekData.length, remaining);
                peekData.copy(buffer, offset + bytesRead, 0, lenCopy);
                bytesRead += lenCopy;
                remaining -= lenCopy;
                if (lenCopy < peekData.length) {
                    // remainder back to queue
                    this.peekQueue.push(peekData.slice(lenCopy));
                }
            }
            // continue reading from stream if required
            if (remaining > 0 && !this.endOfStream) {
                bytesRead += yield this._read(buffer, offset + bytesRead, remaining);
            }
            return bytesRead;
        });
    }
    /**
     * Read chunk from stream
     * @param buffer Buffer to store data read from stream in
     * @param offset Offset buffer
     * @param length Number of bytes to read
     * @returns {any}
     */
    _read(buffer, offset, length) {
        return __awaiter(this, void 0, void 0, function* () {
            assert.ok(!this.request, 'Concurrent read operation?');
            const readBuffer = this.s.read(length);
            if (readBuffer) {
                readBuffer.copy(buffer, offset);
                return readBuffer.length;
            }
            else {
                this.request = {
                    buffer,
                    offset,
                    length,
                    deferred: new Deferred()
                };
                this.s.once('readable', () => {
                    this.tryRead();
                });
                return this.request.deferred.promise.then(n => {
                    this.request = null;
                    return n;
                }).catch(err => {
                    this.request = null;
                    throw err;
                });
            }
        });
    }
    tryRead() {
        const readBuffer = this.s.read(this.request.length);
        if (readBuffer) {
            readBuffer.copy(this.request.buffer, this.request.offset);
            this.request.deferred.resolve(readBuffer.length);
        }
        else {
            this.s.once('readable', () => {
                this.tryRead();
            });
        }
    }
    reject(err) {
        this.endOfStream = true;
        if (this.request) {
            this.request.deferred.reject(err);
            this.request = null;
        }
    }
}
exports.StreamReader = StreamReader;