/**
 * @file Misc utility functions.
 * @author Johan Nordberg <code@johan-nordberg.com>
 * @license
 * Copyright (c) 2017 Johan Nordberg. All Rights Reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 *  1. Redistribution of source code must retain the above copyright notice, this
 *     list of conditions and the following disclaimer.
 *
 *  2. Redistribution in binary form must reproduce the above copyright notice,
 *     this list of conditions and the following disclaimer in the documentation
 *     and/or other materials provided with the distribution.
 *
 *  3. Neither the name of the copyright holder nor the names of its contributors
 *     may be used to endorse or promote products derived from this software without
 *     specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
 * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * You acknowledge that this software is not designed, licensed or intended for use
 * in the design, construction, operation or maintenance of any military facility.
 */

import {EventEmitter} from 'events'
import {PassThrough} from 'stream'
import {VError} from 'verror'

const fetch = global['fetch'] // tslint:disable-line:no-string-literal

/**
 * Return a promise that will resove when a specific event is emitted.
 */
export function waitForEvent<T>(emitter: EventEmitter, eventName: string|symbol): Promise<T> {
    return new Promise((resolve, reject) => {
        emitter.once(eventName, resolve)
    })
}

/**
 * Sleep for N milliseconds.
 */
export function sleep(ms: number): Promise<void> {
    return new Promise<void>((resolve) => {
        setTimeout(resolve, ms)
    })
}

/**
 * Return a stream that emits iterator values.
 */
export function iteratorStream<T>(iterator: AsyncIterableIterator<T>): NodeJS.ReadableStream {
    const stream = new PassThrough({objectMode: true})
    const iterate = async () => {
        for await (const item of iterator) {
            if (!stream.write(item)) {
                await waitForEvent(stream, 'drain')
            }
        }
    }
    iterate().then(() => {
        stream.end()
    }).catch((error) => {
        stream.emit('error', error)
        stream.end()
    })
    return stream
}

/**
 * Return a deep copy of a JSON-serializable object.
 */
export function copy<T>(object: T): T {
    return JSON.parse(JSON.stringify(object))
}

/**
 * Fetch API wrapper that retries until timeout is reached.
 */
export async function retryingFetch(url: string, opts: any, timeout: number,
                                    backoff: (tries: number) => number,
                                    fetchTimeout?: (tries: number) => number) {
    const start = Date.now()
    let tries = 0
    do {
        try {
            if (fetchTimeout) {
                opts.timeout = fetchTimeout(tries)
            }
            const response = await fetch(url, opts)
            if (!response.ok) {
                throw new Error(`HTTP ${ response.status }: ${ response.statusText }`)
            }
            return await response.json()
        } catch (error) {
            if (timeout !== 0 && Date.now() - start > timeout) {
                throw error
            }
            await sleep(backoff(tries++))
        }
    } while (true)
}
