import { app, BrowserWindow } from 'electron';
import * as fs from 'fs';
import * as os from 'os';
import * as path from 'path';

import { ChildProcess, ExecException, execFile } from 'child_process';
import * as util from 'util';
import { IScreenSnippet } from '../common/api-interface';
import { isDevEnv, isLinux, isMac, isWindowsOS } from '../common/env';
import { i18n } from '../common/i18n';
import { logger } from '../common/logger';
import { updateAlwaysOnTop } from './window-actions';
import { windowHandler } from './window-handler';
import { windowExists } from './window-utils';

const readFile = util.promisify(fs.readFile);

class ScreenSnippet {
    private readonly tempDir: string;
    private readonly captureUtil: string;
    private outputFileName: string | undefined;
    private captureUtilArgs: ReadonlyArray<string> | undefined;
    private child: ChildProcess | undefined;
    private focusedWindow: BrowserWindow | null = null;
    private shouldUpdateAlwaysOnTop: boolean = false;

    constructor() {
        this.tempDir = os.tmpdir();
        this.captureUtil = isMac ? '/usr/sbin/screencapture' : isDevEnv
            ? path.join(__dirname,
                '../../../node_modules/screen-snippet/ScreenSnippet.exe')
            : path.join(path.dirname(app.getPath('exe')), 'ScreenSnippet.exe');

        if (isLinux) {
            this.captureUtil = '/usr/bin/gnome-screenshot';
        }
    }

    /**
     * Captures a user selected portion of the monitor and returns jpeg image
     * encoded in base64 format.
     *
     * @param webContents {Electron.webContents}
     */
    public async capture(webContents: Electron.webContents) {
        const mainWindow = windowHandler.getMainWindow();
        if (mainWindow && windowExists(mainWindow) && isWindowsOS) {
            this.shouldUpdateAlwaysOnTop = mainWindow.isAlwaysOnTop();
            if (this.shouldUpdateAlwaysOnTop) {
                await updateAlwaysOnTop(false, false, false);
            }
        }
        logger.info(`screen-snippet-handler: Starting screen capture!`);
        this.outputFileName = path.join(this.tempDir, 'symphonyImage-' + Date.now() + '.png');
        this.captureUtilArgs = isMac
            ? [ '-i', '-s', '-t', 'png', this.outputFileName ]
            : [ this.outputFileName, i18n.getLocale() ];
        this.focusedWindow = BrowserWindow.getFocusedWindow();

        if (isLinux) {
            this.captureUtilArgs = ['-a', '-f', this.outputFileName];
        }
        logger.info(`screen-snippet-handler: Capturing snippet with file ${this.outputFileName} and args ${this.captureUtilArgs}!`);

        // only allow one screen capture at a time.
        if (this.child) {
            logger.info(`screen-snippet-handler: Child screen capture exists, killing it and keeping only 1 instance!`);
            this.killChildProcess();
        }
        try {
            await this.execCmd(this.captureUtil, this.captureUtilArgs);
            const { message, data, type }: IScreenSnippet = await this.convertFileToData();
            logger.info(`screen-snippet-handler: Snippet captured! Sending data to SFE`);
            webContents.send('screen-snippet-data', { message, data, type });
            await this.verifyAndUpdateAlwaysOnTop();
        } catch (error) {
            await this.verifyAndUpdateAlwaysOnTop();
            logger.error(`screen-snippet-handler: screen capture failed with error: ${error}!`);
        }
    }

    /**
     * Cancels a screen capture and closes the snippet window
     */
    public async cancelCapture() {
        if (!isWindowsOS) {
            return;
        }
        logger.info(`screen-snippet-handler: Cancel screen capture!`);
        this.focusedWindow = BrowserWindow.getFocusedWindow();

        try {
            await this.execCmd(this.captureUtil, []);
            await this.verifyAndUpdateAlwaysOnTop();
        } catch (error) {
            await this.verifyAndUpdateAlwaysOnTop();
            logger.error(`screen-snippet-handler: screen capture cancel failed with error: ${error}!`);
        }
    }

    /**
     * Kills the child process when the application is reloaded
     */
    public killChildProcess(): void {
        if (this.child && typeof this.child.kill === 'function') {
            this.child.kill();
        }
    }

    /**
     * Executes the given command via a child process
     *
     * Windows: uses custom built windows screen capture tool
     * Mac OSX: uses built-in screencapture tool which has been
     * available since OSX ver 10.2.
     *
     * @param captureUtil {string}
     * @param captureUtilArgs {captureUtilArgs}
     * @example execCmd('-i -s', '/user/desktop/symphonyImage-1544025391698.png')
     */
    private execCmd(captureUtil: string, captureUtilArgs: ReadonlyArray<string>): Promise<ChildProcess> {
        logger.info(`screen-snippet-handlers: execCmd ${captureUtil} ${captureUtilArgs}`);
        return new Promise<ChildProcess>((resolve, reject) => {
            return this.child = execFile(captureUtil, captureUtilArgs, (error: ExecException | null) => {
                if (error && error.killed) {
                    // processs was killed, just resolve with no data.
                    return reject(error);
                }
                resolve();
            });
        });
    }

    /**
     * Converts the temporary stored file into base64
     * and removes the temp file
     *
     * @return Promise<IScreenSnippet> { message, data, type }
     */
    private async convertFileToData(): Promise<IScreenSnippet> {
        try {
            if (!this.outputFileName) {
                logger.info(`screen-snippet-handler: screen capture failed! output file doesn't exist!`);
                return { message: 'output file name is required', type: 'ERROR' };
            }
            const data = await readFile(this.outputFileName);
            if (!data) {
                logger.info(`screen-snippet-handler: screen capture failed! data doesn't exist!`);
                return { message: `no file data provided`, type: 'ERROR' };
            }
            // convert binary data to base64 encoded string
            const output = Buffer.from(data).toString('base64');
            return { message: 'success', data: output, type: 'image/png;base64' };
        } catch (error) {
            // no such file exists or user likely aborted
            // creating snippet. also include any error when
            // creating child process.
            return error && error.code === 'ENOENT'
                ? { message: `file does not exist`, type: 'ERROR' }
                : { message: `${error}`, type: 'ERROR' };
        } finally {
            if (this.focusedWindow && windowExists(this.focusedWindow)) {
                    logger.info(`screen-snippet-handler: cleaning up temp snippet file: ${this.outputFileName}!`);
                    if (removeErr) {
                        logger.error(`screen-snippet-handler: error removing temp snippet file: ${this.outputFileName}, err: ${removeErr}`);
                    }
                });
            }
        }
    }

    /**
     * Verify and updates always on top
     */
    private async verifyAndUpdateAlwaysOnTop(): Promise<void> {
        if (this.shouldUpdateAlwaysOnTop) {
            await updateAlwaysOnTop(true, false, false);
            this.shouldUpdateAlwaysOnTop = false;
        }
    }
}

const screenSnippet = new ScreenSnippet();

export { screenSnippet };
                this.focusedWindow.moveTop();
            }
            // remove tmp file (async)
            if (this.outputFileName) {
                fs.unlink(this.outputFileName, (removeErr) => {