// *****************************************************************************
// Copyright (C) 2017 TypeFox and others.
//
// This program and the accompanying materials are made available under the
// terms of the Eclipse Public License v. 2.0 which is available at
// http://www.eclipse.org/legal/epl-2.0.
//
// This Source Code may also be made available under the following Secondary
// Licenses when the conditions for such availability set forth in the Eclipse
// Public License v. 2.0 are satisfied: GNU General Public License, version 2
// with the GNU Classpath Exception which is available at
// https://www.gnu.org/software/classpath/license.html.
//
// SPDX-License-Identifier: EPL-2.0 OR GPL-2.0-only WITH Classpath-exception-2.0
// *****************************************************************************

import cp = require('child_process');
import fs = require('fs-extra');
import path = require('path');
import os = require('os');

export type RebuildTarget = 'electron' | 'browser' | 'browser-only';

const EXIT_SIGNALS: NodeJS.Signals[] = ['SIGINT', 'SIGTERM'];

interface ExitToken {
    getLastSignal(): NodeJS.Signals | undefined
    onSignal(callback: (signal: NodeJS.Signals) => void): void
}

type NodeABI = string | number;

export const DEFAULT_MODULES = [
    'node-pty',
    'native-keymap',
    'find-git-repositories',
    'drivelist',
    'keytar',
    'ssh2',
    'cpu-features'
];

export interface RebuildOptions {
    /**
     * What modules to rebuild.
     */
    modules?: string[]
    /**
     * Folder where the module cache will be created/read from.
     */
    cacheRoot?: string
    /**
     * In the event that `node-abi` doesn't recognize the current Electron version,
     * you can specify the Node ABI to rebuild for.
     */
    forceAbi?: NodeABI
}

/**
 * @param target What to rebuild for.
 * @param options
 */
export function rebuild(target: RebuildTarget, options: RebuildOptions = {}): void {
    const {
        modules = DEFAULT_MODULES,
        cacheRoot = process.cwd(),
        forceAbi,
    } = options;
    const cache = path.resolve(cacheRoot, '.browser_modules');
    const cacheExists = folderExists(cache);
    guardExit(async token => {
        if (target === 'electron' && !cacheExists) {
            process.exitCode = await rebuildElectronModules(cache, modules, forceAbi, token);
        } else if (target === 'browser' && cacheExists) {
            process.exitCode = await revertBrowserModules(cache, modules);
        } else {
            console.log(`native node modules are already rebuilt for ${target}`);
        }
    }).catch(errorOrSignal => {
        if (typeof errorOrSignal === 'string' && errorOrSignal in os.constants.signals) {
            process.kill(process.pid, errorOrSignal);
        } else {
            throw errorOrSignal;
        }
    });
}

function folderExists(folder: string): boolean {
    if (fs.existsSync(folder)) {
        if (fs.statSync(folder).isDirectory()) {
            return true;
        } else {
            throw new Error(`"${folder}" exists but it is not a directory`);
        }
    }
    return false;
}

/**
 * Schema for `<browserModuleCache>/modules.json`.
 */
interface ModulesJson {
    [moduleName: string]: ModuleBackup
}
interface ModuleBackup {
    originalLocation: string
}

async function rebuildElectronModules(browserModuleCache: string, modules: string[], forceAbi: NodeABI | undefined, token: ExitToken): Promise<number> {
    const modulesJsonPath = path.join(browserModuleCache, 'modules.json');
    const modulesJson: ModulesJson = await fs.access(modulesJsonPath).then(
        () => fs.readJson(modulesJsonPath),
        () => ({})
    );
    let success = true;
    // Backup already built browser modules.
    await Promise.all(modules.map(async module => {
        let modulePath;
        try {
            modulePath = require.resolve(`${module}/package.json`, {
                paths: [process.cwd()],
            });
        } catch (_) {
            console.debug(`Module not found: ${module}`);
            return; // Skip current module.
        }
        const src = path.dirname(modulePath);
        const dest = path.join(browserModuleCache, module);
        try {
            await fs.remove(dest);
            await fs.copy(src, dest, { overwrite: true });
            modulesJson[module] = {
                originalLocation: src,
            };
            console.debug(`Processed "${module}"`);
        } catch (error) {
            console.error(`Error while doing a backup for "${module}": ${error}`);
            success = false;
        }
    }));
    if (Object.keys(modulesJson).length === 0) {
        console.debug('No module to rebuild.');
        return 0;
    }
    // Update manifest tracking the backups' original locations.
    await fs.writeJson(modulesJsonPath, modulesJson, { spaces: 2 });
    // If we failed to process a module then exit now.
    if (!success) {
        return 1;
    }
    const todo = modules.map(m => {
        // electron-rebuild ignores the module namespace...
        const slash = m.indexOf('/');
        return m.startsWith('@') && slash !== -1
            ? m.substring(slash + 1)
            : m;
    });
    let exitCode: number | undefined;
    try {
        if (process.env.THEIA_REBUILD_NO_WORKAROUND) {
            exitCode = await runElectronRebuild(todo, forceAbi, token);
        } else {
            exitCode = await electronRebuildExtraModulesWorkaround(process.cwd(), todo, () => runElectronRebuild(todo, forceAbi, token), token);
        }
    } catch (error) {
        console.error(error);
    } finally {
        // If code is undefined or different from zero we need to revert back to the browser modules.
        if (exitCode !== 0) {
            await revertBrowserModules(browserModuleCache, modules);
        }
        return exitCode ?? 1;
    }
}

async function revertBrowserModules(browserModuleCache: string, modules: string[]): Promise<number> {
    let exitCode = 0;
    const modulesJsonPath = path.join(browserModuleCache, 'modules.json');
    const modulesJson: ModulesJson = await fs.readJson(modulesJsonPath);
    await Promise.all(Object.entries(modulesJson).map(async ([moduleName, entry]) => {
        if (!modules.includes(moduleName)) {
            return; // Skip modules that weren't requested.
        }
        const src = path.join(browserModuleCache, moduleName);
        if (!await fs.pathExists(src)) {
            delete modulesJson[moduleName];
            console.error(`Missing backup for ${moduleName}!`);
            exitCode = 1;
            return;
        }
        const dest = entry.originalLocation;
        try {
            await fs.remove(dest);
            await fs.copy(src, dest, { overwrite: false });
            await fs.remove(src);
            delete modulesJson[moduleName];
            console.debug(`Reverted "${moduleName}"`);
        } catch (error) {
            console.error(`Error while reverting "${moduleName}": ${error}`);
            exitCode = 1;
        }
    }));
    if (Object.keys(modulesJson).length === 0) {
        // We restored everything, so we can delete the cache.
        await fs.remove(browserModuleCache);
    } else {
        // Some things were not restored, so we update the manifest.
        await fs.writeJson(modulesJsonPath, modulesJson, { spaces: 2 });
    }
    return exitCode;
}

async function runElectronRebuild(modules: string[], forceAbi: NodeABI | undefined, token: ExitToken): Promise<number> {
    const todo = modules.join(',');
    return new Promise(async (resolve, reject) => {
        let command = `npx --no-install electron-rebuild -f -w=${todo} -o=${todo}`;
        if (forceAbi) {
            command += ` --force-abi ${forceAbi}`;
        }
        const electronRebuild = cp.spawn(command, {
            stdio: 'inherit',
            shell: true,
        });
        token.onSignal(signal => electronRebuild.kill(signal));
        electronRebuild.on('error', reject);
        electronRebuild.on('close', (code, signal) => {
            if (signal) {
                reject(new Error(`electron-rebuild exited with "${signal}"`));
            } else {
                resolve(code!);
            }
        });
    });
}

/**
 * `electron-rebuild` is supposed to accept a list of modules to build, even when not part of the dependencies.
 * But there is a bug that causes `electron-rebuild` to not correctly process this list of modules.
 *
 * This workaround will temporarily modify the current package.json file.
 *
 * PR with fix: https://github.com/electron/electron-rebuild/pull/888
 *
 * TODO: Remove this workaround.
 */
async function electronRebuildExtraModulesWorkaround<T>(cwd: string, extraModules: string[], run: (token: ExitToken) => Promise<T>, token: ExitToken): Promise<T> {
    const packageJsonPath = path.resolve(cwd, 'package.json');
    if (await fs.pathExists(packageJsonPath)) {
        // package.json exists: We back it up before modifying it then revert it.
        const packageJsonCopyPath = `${packageJsonPath}.copy`;
        const packageJson = await fs.readJson(packageJsonPath);
        await fs.copy(packageJsonPath, packageJsonCopyPath);
        await throwIfSignal(token, async () => {
            await fs.unlink(packageJsonCopyPath);
        });
        if (typeof packageJson.dependencies !== 'object') {
            packageJson.dependencies = {};
        }
        for (const extraModule of extraModules) {
            if (!packageJson.dependencies[extraModule]) {
                packageJson.dependencies[extraModule] = '*';
            }
        }
        try {
            await fs.writeJson(packageJsonPath, packageJson, { spaces: 2 });
            await throwIfSignal(token);
            return await run(token);
        } finally {
            await fs.move(packageJsonCopyPath, packageJsonPath, { overwrite: true });
        }
    } else {
        // package.json does not exist: We create one then remove it.
        const packageJson = {
            name: 'theia-rebuild-workaround',
            version: '0.0.0',
            dependencies: {} as Record<string, string>,
        };
        for (const extraModule of extraModules) {
            packageJson.dependencies[extraModule] = '*';
        }
        try {
            await fs.writeJson(packageJsonPath, packageJson);
            await throwIfSignal(token);
            return await run(token);
        } finally {
            await fs.unlink(packageJsonPath);
        }
    }
}

/**
 * Temporarily install hooks to **try** to prevent the process from exiting while `run` is running.
 *
 * Note that it is still possible to kill the process and prevent cleanup logic (e.g. SIGKILL, computer forced shutdown, etc).
 */
async function guardExit<T>(run: (token: ExitToken) => Promise<T>): Promise<T> {
    const token = new ExitTokenImpl();
    const signalListener = (signal: NodeJS.Signals) => token._emitSignal(signal);
    for (const signal of EXIT_SIGNALS) {
        process.on(signal, signalListener);
    }
    try {
        return await run(token);
    } finally {
        for (const signal of EXIT_SIGNALS) {
            // FIXME we have a type clash here between Node, Electron and Mocha.
            // Typescript is resolving here to Electron's Process interface which extends the NodeJS.EventEmitter interface
            // However instead of the actual NodeJS.EventEmitter interface it resolves to an empty stub of Mocha
            // Therefore it can't find the correct "off" signature and throws an error
            // By casting to the NodeJS.EventEmitter ourselves, we short circuit the resolving and it succeeds
            (process as NodeJS.EventEmitter).off(signal, signalListener);
        }
    }
}

class ExitTokenImpl implements ExitToken {

    protected _listeners = new Set<(signal: NodeJS.Signals) => void>();
    protected _lastSignal?: NodeJS.Signals;

    onSignal(callback: (signal: NodeJS.Signals) => void): void {
        this._listeners.add(callback);
    }

    getLastSignal(): NodeJS.Signals | undefined {
        return this._lastSignal;
    }

    _emitSignal(signal: NodeJS.Signals): void {
        this._lastSignal = signal;
        for (const listener of this._listeners) {
            listener(signal);
        }
    }
}

/**
 * Throw `signal` if one was received, runs `cleanup` before doing so.
 */
async function throwIfSignal(token: ExitToken, cleanup?: () => Promise<void>): Promise<void> {
    if (token.getLastSignal()) {
        try {
            await cleanup?.();
        } finally {
            // eslint-disable-next-line no-throw-literal
            throw token.getLastSignal()!;
        }
    }
}