/*---------------------------------------------------------
 * Copyright 2020 The Go Authors. All rights reserved.
 * Licensed under the MIT License. See LICENSE in the project root for license information.
 *--------------------------------------------------------*/

'use strict';

import cp = require('child_process');
import fs = require('fs');
import os = require('os');
import path = require('path');
import { promisify } from 'util';
import vscode = require('vscode');
import WebRequest = require('web-request');
import { toolInstallationEnvironment } from './goEnv';
import { outputChannel } from './goStatus';
import { getFromWorkspaceState, updateWorkspaceState } from './stateUtils';
import { getBinPath, getGoVersion, getTempFilePath, rmdirRecursive } from './util';
import { correctBinname, getBinPathFromEnvVar, getCurrentGoRoot, pathExists } from './utils/goPath';

export class GoEnvironmentOption {
	public static fromQuickPickItem({ description, label }: vscode.QuickPickItem): GoEnvironmentOption {
		return new GoEnvironmentOption(description, label);
	}

	constructor(public binpath: string, public label: string) {}

	public toQuickPickItem(): vscode.QuickPickItem {
		return {
			label: this.label,
			description: this.binpath,
		};
	}
}

// statusbar item for switching the Go environment
let goEnvStatusbarItem: vscode.StatusBarItem;
let terminalCreationListener: vscode.Disposable;

/**
 * Initialize the status bar item with current Go binary
 */
export async function initGoStatusBar() {
	if (!goEnvStatusbarItem) {
		goEnvStatusbarItem = vscode.window.createStatusBarItem(vscode.StatusBarAlignment.Left, 50);
	}
	// set Go version and command
	const version = await getGoVersion();
	const goOption = new GoEnvironmentOption(version.binaryPath, formatGoVersion(version.format()));

	hideGoStatusBar();
	goEnvStatusbarItem.text = goOption.label;
	goEnvStatusbarItem.command = 'go.environment.choose';
	showGoStatusBar();
}

/**
 * disable the Go environment status bar item
 */
export function disposeGoStatusBar() {
	if (!!goEnvStatusbarItem) {
		goEnvStatusbarItem.dispose();
	}
	if (!!terminalCreationListener) {
		terminalCreationListener.dispose();
	}
}

/**
 * Show the Go Environment statusbar item on the statusbar
 */
export function showGoStatusBar() {
	if (!!goEnvStatusbarItem) {
		goEnvStatusbarItem.show();
	}
}

/**
 * Hide the Go Environment statusbar item from the statusbar
 */
export function hideGoStatusBar() {
	if (!!goEnvStatusbarItem) {
		goEnvStatusbarItem.hide();
	}
}

let environmentVariableCollection: vscode.EnvironmentVariableCollection;
export function setEnvironmentVariableCollection(env: vscode.EnvironmentVariableCollection) {
	environmentVariableCollection = env;
}

/**
 * Present a command palette menu to the user to select their go binary
 */
export async function chooseGoEnvironment() {
	if (!goEnvStatusbarItem) {
		return;
	}

	// if there is no workspace, show GOROOT with message
	if (!vscode.workspace.name) {
		vscode.window.showInformationMessage(`GOROOT: ${getCurrentGoRoot()}. Switching Go version is not yet supported in single-file mode.`);
		return;
	}

	// fetch default go and uninstalled go versions
	let defaultOption: GoEnvironmentOption;
	let uninstalledOptions: GoEnvironmentOption[];
	let goSDKOptions: GoEnvironmentOption[];
	try {
		[defaultOption, uninstalledOptions, goSDKOptions] = await Promise.all([
			getDefaultGoOption(),
			fetchDownloadableGoVersions(),
			getSDKGoOptions()
		]);
	} catch (e) {
		vscode.window.showErrorMessage(e.message);
		return;
	}

	// create quick pick items
	const uninstalledQuickPicks = uninstalledOptions.map((op) => op.toQuickPickItem());
	const defaultQuickPick = defaultOption.toQuickPickItem();
	const goSDKQuickPicks = goSDKOptions.map((op) => op.toQuickPickItem());

	// dedup options by eliminating duplicate paths (description)
	const clearOption: vscode.QuickPickItem = { label: 'Clear selection' };
	const options = [clearOption, defaultQuickPick, ...goSDKQuickPicks, ...uninstalledQuickPicks]
		.reduce((opts, nextOption) => {
			if (opts.find((op) => op.description === nextOption.description || op.label === nextOption.label)) {
				return opts;
			}
			return [...opts, nextOption];
		}, [] as vscode.QuickPickItem[]);

	// get user's selection, return if none was made
	const selection = await vscode.window.showQuickPick<vscode.QuickPickItem>(options);
	if (!selection) {
		return;
	}

	// update currently selected go
	try {
		const changed = await setSelectedGo(GoEnvironmentOption.fromQuickPickItem(selection));
		if (changed) {
			vscode.window.showInformationMessage(`Switched to ${selection.label}`);
		}
	} catch (e) {
		vscode.window.showErrorMessage(e.message);
	}
}

/**
 * update the selected go path and label in the workspace state
 */
export async function setSelectedGo(goOption: GoEnvironmentOption, promptReload = true): Promise<boolean> {
	if (!goOption) {
		return false;
	}

	// if the selected go version is not installed, install it
	if (goOption.binpath?.startsWith('go get')) {
		// start a loading indicator
		await downloadGo(goOption);
	} else if (goOption.label === 'Clear selection') {
		if (!getSelectedGo()) {
			return false;  // do nothing.
		}
		await updateWorkspaceState('selectedGo', undefined);
		// TODO: goEnvStatusbarItem?
	} else {
		// check that the given binary is not already at the beginning of the PATH
		const go = await getGoVersion();
		if (!!go && (go.binaryPath === goOption.binpath || 'Go ' + go.format() === goOption.label)) {
			return false;
		}
		await updateWorkspaceState('selectedGo', goOption);
	}
	// prompt the user to reload the window.
	// promptReload defaults to true and should only be false for tests.
	if (promptReload) {
		const choice = await vscode.window.showInformationMessage('Please reload the window to finish applying Go version changes.', 'Reload Window');
		if (choice === 'Reload Window') {
			await vscode.commands.executeCommand('workbench.action.reloadWindow');
		}
	}
	goEnvStatusbarItem.text = 'Go: reload required';
	goEnvStatusbarItem.command = 'workbench.action.reloadWindow';

	return true;
}

// downloadGo downloads the specified go version available in dl.golang.org.
async function downloadGo(goOption: GoEnvironmentOption) {
	const execFile = promisify(cp.execFile);
	await vscode.window.withProgress({
		title: `Downloading ${goOption.label}`,
		location: vscode.ProgressLocation.Notification,
	}, async () => {
		outputChannel.show();
		outputChannel.clear();

		outputChannel.appendLine('Finding Go executable for downloading');
		const goExecutable = getBinPath('go');
		if (!goExecutable) {
			outputChannel.appendLine('Could not find Go executable.');
			throw new Error('Could not find Go tool.');
		}

		// TODO(bcloud) dedup repeated logic below which comes from
		// https://github.com/golang/vscode-go/blob/bc23fa854192d04200c8e4f74dca18d2c3021b46/src/goInstallTools.ts#L184
		// Install tools in a temporary directory, to avoid altering go.mod files.
		const mkdtemp = promisify(fs.mkdtemp);
		const toolsTmpDir = await mkdtemp(getTempFilePath('go-tools-'));
		let tmpGoModFile: string;

		// Write a temporary go.mod file to avoid version conflicts.
		tmpGoModFile = path.join(toolsTmpDir, 'go.mod');
		const writeFile = promisify(fs.writeFile);
		await writeFile(tmpGoModFile, 'module tools');

		// use the current go executable to download the new version
		const env = {
			...toolInstallationEnvironment(),
			GO111MODULE: 'on',
		};
		const [, ...args] = goOption.binpath.split(' ');
		outputChannel.appendLine(`Running ${goExecutable} ${args.join(' ')}`);
		try {
			await execFile(goExecutable, args, {
				env,
				cwd: toolsTmpDir,
			});
		} catch (getErr) {
			outputChannel.appendLine(`Error finding Go: ${getErr}`);
			throw new Error('Could not find Go version.');
		}

		// run `goX.X download`
		const newExecutableName = args[1].split('/')[2];
		const goXExecutable = getBinPath(newExecutableName);
		outputChannel.appendLine(`Running: ${goXExecutable} download`);
		try {
			await execFile(goXExecutable, ['download'], { env });
		} catch (downloadErr) {
			outputChannel.appendLine(`Error finishing installation: ${downloadErr}`);
			throw new Error('Could not download Go version.');
		}

		outputChannel.appendLine('Finding newly downloaded Go');
		const sdkPath = path.join(os.homedir(), 'sdk');
		if (!await pathExists(sdkPath)) {
			outputChannel.appendLine(`SDK path does not exist: ${sdkPath}`);
			throw new Error(`SDK path does not exist: ${sdkPath}`);
		}

		const readdir = promisify(fs.readdir);
		const subdirs = await readdir(sdkPath);
		const dir = subdirs.find((subdir) => subdir === newExecutableName);
		if (!dir) {
			outputChannel.appendLine('Could not find newly downloaded Go');
			throw new Error('Could not install Go version.');
		}

		const binpath = path.join(sdkPath, dir, 'bin', correctBinname('go'));
		const newOption = new GoEnvironmentOption(binpath, goOption.label);
		await updateWorkspaceState('selectedGo', newOption);

		// remove tmp directories
		outputChannel.appendLine('Cleaning up...');
		rmdirRecursive(toolsTmpDir);
		outputChannel.appendLine('Success!');
	});
}

// PATH value cached before addGoRuntimeBaseToPath modified.
let defaultPathEnv = '';

// addGoRuntimeBaseToPATH adds the given path to the front of the PATH environment variable.
// It removes duplicates.
// TODO: can we avoid changing PATH but utilize toolExecutionEnv?
export function addGoRuntimeBaseToPATH(newGoRuntimeBase: string) {
	if (!newGoRuntimeBase) {
		return;
	}

	let pathEnvVar: string;
	if (process.env.hasOwnProperty('PATH')) {
		pathEnvVar = 'PATH';
	} else if (process.platform === 'win32' && process.env.hasOwnProperty('Path')) {
		pathEnvVar = 'Path';
	} else {
		return;
	}

	if (!defaultPathEnv) {  // cache the default value
		defaultPathEnv = <string>process.env[pathEnvVar];
	}

	// calling this multiple times will override the previous value.
	// environmentVariableCollection.clear();
	if (process.platform !== 'darwin') {
		environmentVariableCollection?.prepend(pathEnvVar, newGoRuntimeBase + path.delimiter);
	} else if (!terminalCreationListener) {
		// We don't use EnvironmentVariableCollection on mac
		// because this gets confusing for users. Instead we send the
		// shell command to change the PATH env var,
		// following the suggestion to workaround described in
		// https://github.com/microsoft/vscode/issues/99878#issuecomment-642808852
		const terminalShellArgs = <string[]>(vscode.workspace.getConfiguration('terminal.integrated').get('shellArgs') || []);
		// User explicitly chose to run the login shell. So, don't mess with their config.
		if (!terminalShellArgs.includes('-l') && !terminalShellArgs.includes('--login')) {
			for (const term of vscode.window.terminals) {
				updateIntegratedTerminal(term);
			}
			terminalCreationListener = vscode.window.onDidOpenTerminal(updateIntegratedTerminal);
		}
	}

	let pathVars = defaultPathEnv.split(path.delimiter);
	pathVars = pathVars.filter((p) => p !== newGoRuntimeBase);
	pathVars.unshift(newGoRuntimeBase);
	process.env[pathEnvVar] = pathVars.join(path.delimiter);
}

/**
 * update the PATH variable in the given terminal to default to the currently selected Go
 */
export async function updateIntegratedTerminal(terminal: vscode.Terminal): Promise<void> {
	if (!terminal) { return; }
	const gorootBin = path.join(getCurrentGoRoot(), 'bin');
	const defaultGoRuntimeBin = path.dirname(getBinPathFromEnvVar('go', defaultPathEnv, false));
	if (gorootBin === defaultGoRuntimeBin) {
		return;
	}

	// append the goroot to the beginning of the PATH so it takes precedence
	// TODO: add support for more terminal names
	// this assumes all non-windows shells are bash-like.
	if (terminal.name.toLowerCase() === 'cmd') {
		terminal.sendText(`set PATH=${gorootBin};%Path%`, true);
		terminal.sendText('cls');
	} else if (['powershell', 'pwsh'].includes(terminal.name.toLowerCase())) {
		terminal.sendText(`$env:Path="${gorootBin};$env:Path"`, true);
		terminal.sendText('clear');
	} else if (terminal.name.toLowerCase() === 'fish') {
		terminal.sendText(`set -gx PATH ${gorootBin} $PATH`);
		terminal.sendText('clear');
	} else if (['bash', 'sh', 'zsh', 'ksh'].includes(terminal.name.toLowerCase())) {
		terminal.sendText(`export PATH=${gorootBin}:$PATH`, true);
		terminal.sendText('clear');
	}
}

/**
 * retreive the current selected Go from the workspace state
 */
export function getSelectedGo(): GoEnvironmentOption {
	return getFromWorkspaceState('selectedGo');
}

/**
 * return reference to the statusbar item
 */
export function getGoEnvironmentStatusbarItem(): vscode.StatusBarItem {
	return goEnvStatusbarItem;
}

export function formatGoVersion(version: string): string {
	const versionWords = version.split(' ');
	if (versionWords[0] === 'devel') {
		// Go devel +hash
		return `Go ${versionWords[0]} ${versionWords[4]}`;
	} else if (versionWords.length > 0) {
		// some other version format
		return `Go ${version.substr(0, 8)}`;
	} else {
		// default semantic version format
		return `Go ${versionWords[0]}`;
	}
}

async function getSDKGoOptions(): Promise<GoEnvironmentOption[]> {
	// get list of Go versions
	const sdkPath = path.join(os.homedir(), 'sdk');

	if (!await pathExists(sdkPath)) {
		return [];
	}
	const readdir = promisify(fs.readdir);
	const subdirs = await readdir(sdkPath);
	// the dir happens to be the version, which will be used as the label
	// the path is assembled and used as the description
	return subdirs.map((dir: string) =>
		new GoEnvironmentOption(
			path.join(sdkPath, dir, 'bin', 'go'),
			dir.replace('go', 'Go '),
		)
	);
}

export async function getDefaultGoOption(): Promise<GoEnvironmentOption> {
	// make goroot default to go.goroot
	const goroot = getCurrentGoRoot();
	if (!goroot) {
		throw new Error('No Go command could be found.');
	}

	// set Go version and command
	const version = await getGoVersion();
	return new GoEnvironmentOption(
		path.join(goroot, 'bin', 'go'),
		formatGoVersion(version.format()),
	);
}

/**
 * make a web request to get versions of Go
 */
interface GoVersionWebResult {
	version: string;
	stable: boolean;
	files: {
		filename: string;
		os: string;
		arch: string;
		version: string;
		sha256: string;
		size: number;
		kind: string;
	}[];
}
async function fetchDownloadableGoVersions(): Promise<GoEnvironmentOption[]> {
	// fetch information about what Go versions are available to install
	const webResults = await WebRequest.json<GoVersionWebResult[]>('https://golang.org/dl/?mode=json');
	if (!webResults) {
		return [];
	}

	// turn the web result into GoEnvironmentOption model
	return webResults.reduce((opts, result: GoVersionWebResult) => {
		// TODO: allow downloading from different sites
		const dlPath = `go get golang.org/dl/${result.version}`;
		const label = result.version.replace('go', 'Go ');
		return [...opts, new GoEnvironmentOption(dlPath, label)];
	}, []);
}