/*---------------------------------------------------------
 * Copyright (C) Microsoft Corporation. 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 deepEqual = require('deep-equal');
import moment = require('moment');
import path = require('path');
import semver = require('semver');
import util = require('util');
import vscode = require('vscode');
import {
	Command,
	HandleDiagnosticsSignature,
	LanguageClient,
	ProvideCompletionItemsSignature,
	ProvideDocumentLinksSignature,
	RevealOutputChannelOn
} from 'vscode-languageclient';
import WebRequest = require('web-request');
import { promptForMissingTool, promptForUpdatingTool } from './goInstallTools';
import { getToolFromToolPath } from './goPath';
import { getTool, Tool } from './goTools';
import { getBinPath, getCurrentGoPath, getGoConfig, getToolsEnvVars } from './util';

interface LanguageServerConfig {
	serverName: string;
	path: string;
	enabled: boolean;
	flags: string[];
	env: any;
	features: {
		diagnostics: boolean;
		documentLink: boolean;
	};
	checkForUpdates: boolean;
}

// Global variables used for management of the language client.
// They are global so that the server can be easily restarted with
// new configurations.
let languageClient: LanguageClient;
let languageServerDisposable: vscode.Disposable;
let latestConfig: LanguageServerConfig;
let serverOutputChannel: vscode.OutputChannel;

// startLanguageServer starts the language server (if enabled), returning
// true on success.
export async function registerLanguageFeatures(ctx: vscode.ExtensionContext): Promise<boolean> {
	// Subscribe to notifications for changes to the configuration of the language server.
	ctx.subscriptions.push(vscode.workspace.onDidChangeConfiguration((e) => watchLanguageServerConfiguration(e)));

	const config = parseLanguageServerConfig();
	if (!config.enabled) {
		return false;
	}

	// Support a command to restart the language server, if it's enabled.
	ctx.subscriptions.push(vscode.commands.registerCommand('go.languageserver.restart', () => {
		return startLanguageServer(ctx, parseLanguageServerConfig());
	}));

	// If the language server is gopls, we can check if the user needs to
	// update their gopls version.
	if (config.serverName === 'gopls') {
		const tool = getTool(config.serverName);
		if (!tool) {
			return false;
		}
		const versionToUpdate = await shouldUpdateLanguageServer(tool, config.path, config.checkForUpdates);
		if (versionToUpdate) {
			promptForUpdatingTool(tool.name, versionToUpdate);
		}
	}

	// This function handles the case when the server isn't started yet,
	// so we can call it to start the language server.
	return startLanguageServer(ctx, config);
}

async function startLanguageServer(ctx: vscode.ExtensionContext, config: LanguageServerConfig): Promise<boolean> {
	// If the client has already been started, make sure to clear existing
	// diagnostics and stop it.
	if (languageClient) {
		if (languageClient.diagnostics) {
			languageClient.diagnostics.clear();
		}
		await languageClient.stop();
		if (languageServerDisposable) {
			languageServerDisposable.dispose();
		}
	}

	// Check if we should recreate the language client. This may be necessary
	// if the user has changed settings in their config.
	if (!deepEqual(latestConfig, config)) {
		// Track the latest config used to start the language server.
		latestConfig = config;

		// If the user has not enabled or installed the language server, return.
		if (!config.enabled || !config.path) {
			return false;
		}
		buildLanguageClient(config);
	}

	languageServerDisposable = languageClient.start();
	ctx.subscriptions.push(languageServerDisposable);

	return true;
}

function buildLanguageClient(config: LanguageServerConfig) {
	// Reuse the same output channel for each instance of the server.
	if (!serverOutputChannel) {
		serverOutputChannel = vscode.window.createOutputChannel(config.serverName);
	}
	languageClient = new LanguageClient(
		config.serverName,
		{
			command: config.path,
			args: ['-mode=stdio', ...config.flags],
			options: { env: config.env },
		},
		{
			initializationOptions: {},
			documentSelector: ['go', 'go.mod', 'go.sum'],
			uriConverters: {
				// Apply file:/// scheme to all file paths.
				code2Protocol: (uri: vscode.Uri): string =>
					(uri.scheme ? uri : uri.with({ scheme: 'file' })).toString(),
				protocol2Code: (uri: string) => vscode.Uri.parse(uri)
			},
			outputChannel: serverOutputChannel,
			revealOutputChannelOn: RevealOutputChannelOn.Never,
			middleware: {
				handleDiagnostics: (
					uri: vscode.Uri,
					diagnostics: vscode.Diagnostic[],
					next: HandleDiagnosticsSignature
				) => {
					if (!config.features.diagnostics) {
						return null;
					}
					return next(uri, diagnostics);
				},
				provideDocumentLinks: (
					document: vscode.TextDocument,
					token: vscode.CancellationToken,
					next: ProvideDocumentLinksSignature
				) => {
					if (!config.features.documentLink) {
						return null;
					}
					return next(document, token);
				},
				provideCompletionItem: (
					document: vscode.TextDocument,
					position: vscode.Position,
					context: vscode.CompletionContext,
					token: vscode.CancellationToken,
					next: ProvideCompletionItemsSignature
				) => {
					// TODO(hyangah): when v1.42+ api is available, we can simplify
					// language-specific configuration lookup using the new
					// ConfigurationScope.
					//    const paramHintsEnabled = vscode.workspace.getConfiguration(
					//          'editor.parameterHints',
					//          { languageId: 'go', uri: document.uri });

					const editorParamHintsEnabled = vscode.workspace.getConfiguration(
						'editor.parameterHints',
						document.uri
					)['enabled'];
					const goParamHintsEnabled = vscode.workspace.getConfiguration('[go]', document.uri)[
						'editor.parameterHints.enabled'
					];

					let paramHintsEnabled: boolean = false;
					if (typeof goParamHintsEnabled === 'undefined') {
						paramHintsEnabled = editorParamHintsEnabled;
					} else {
						paramHintsEnabled = goParamHintsEnabled;
					}
					let cmd: Command;
					if (paramHintsEnabled) {
						cmd = { title: 'triggerParameterHints', command: 'editor.action.triggerParameterHints' };
					}

					function configureCommands(
						r: vscode.CompletionItem[] | vscode.CompletionList | null | undefined
					): vscode.CompletionItem[] | vscode.CompletionList | null | undefined {
						if (r) {
							(Array.isArray(r) ? r : r.items).forEach((i: vscode.CompletionItem) => {
								i.command = cmd;
							});
						}
						return r;
					}
					const ret = next(document, position, context, token);

					const isThenable = <T>(obj: vscode.ProviderResult<T>): obj is Thenable<T> =>
						obj && (<any>obj)['then'];
					if (isThenable<vscode.CompletionItem[] | vscode.CompletionList | null | undefined>(ret)) {
						return ret.then(configureCommands);
					}
					return configureCommands(ret);
				}
			}
		}
	);
	languageClient.onReady().then(() => {
		const capabilities = languageClient.initializeResult && languageClient.initializeResult.capabilities;
		if (!capabilities) {
			return vscode.window.showErrorMessage(
				'The language server is not able to serve any features at the moment.'
			);
		}
	});
}

function watchLanguageServerConfiguration(e: vscode.ConfigurationChangeEvent) {
	if (!e.affectsConfiguration('go')) {
		return;
	}

	const config = parseLanguageServerConfig();
	let reloadMessage: string;

	// If the user has disabled or enabled the language server.
	if (e.affectsConfiguration('go.useLanguageServer')) {
		if (config.enabled) {
			reloadMessage = 'Reload VS Code window to enable the use of language server';
		} else {
			reloadMessage = 'Reload VS Code window to disable the use of language server';
		}
	}

	if (
		e.affectsConfiguration('go.languageServerFlags') ||
		e.affectsConfiguration('go.languageServerExperimentalFeatures')
	) {
		reloadMessage = 'Reload VS Code window for the changes in language server settings to take effect';
	}

	// If there was a change in the configuration of the language server,
	// then ask the user to reload VS Code.
	if (reloadMessage) {
		vscode.window.showInformationMessage(reloadMessage, 'Reload').then((selected) => {
			if (selected === 'Reload') {
				vscode.commands.executeCommand('workbench.action.reloadWindow');
			}
		});
	}
}

export function parseLanguageServerConfig(): LanguageServerConfig {
	const goConfig = getGoConfig();
	const toolsEnv = getToolsEnvVars();
	const languageServerPath = getLanguageServerToolPath();
	const languageServerName = getToolFromToolPath(languageServerPath);
	return {
		serverName: languageServerName,
		path: languageServerPath,
		enabled: goConfig['useLanguageServer'],
		flags: goConfig['languageServerFlags'] || [],
		features: {
			// TODO: We should have configs that match these names.
			// Ultimately, we should have a centralized language server config rather than separate fields.
			diagnostics: goConfig['languageServerExperimentalFeatures']['diagnostics'],
			documentLink: goConfig['languageServerExperimentalFeatures']['documentLink']
		},
		env: toolsEnv,
		checkForUpdates: goConfig['useGoProxyToCheckForToolUpdates']
	};
}

/**
 *
 * If the user has enabled the language server, return the absolute path to the
 * correct binary. If the required tool is not available, prompt the user to
 * install it. Only gopls is officially supported.
 */
export function getLanguageServerToolPath(): string {
	// If language server is not enabled, return
	const goConfig = getGoConfig();
	if (!goConfig['useLanguageServer']) {
		return;
	}

	// Check that all workspace folders are configured with the same GOPATH.
	if (!allFoldersHaveSameGopath()) {
		vscode.window.showInformationMessage(
			'The Go language server is currently not supported in a multi-root set-up with different GOPATHs.'
		);
		return;
	}
	// Get the path to gopls (getBinPath checks for alternate tools).
	const goplsBinaryPath = getBinPath('gopls');
	if (path.isAbsolute(goplsBinaryPath)) {
		return goplsBinaryPath;
	}
	const alternateTools = goConfig['alternateTools'];
	if (alternateTools) {
		// The user's alternate language server was not found.
		const goplsAlternate = alternateTools['gopls'];
		if (goplsAlternate) {
			vscode.window.showErrorMessage(
				`Cannot find the alternate tool ${goplsAlternate} configured for gopls.
Please install it and reload this VS Code window.`
			);
			return;
		}
		// Check if the user has the deprecated "go-langserver" setting.
		// Suggest deleting it if the alternate tool is gopls.
		if (alternateTools['go-langserver']) {
			vscode.window.showErrorMessage(`Support for "go-langserver" has been deprecated.
The recommended language server is gopls. Delete the alternate tool setting for "go-langserver" to use gopls, or change "go-langserver" to "gopls" in your settings.json and reload the VS Code window.`);
			return;
		}
	}

	// Prompt the user to install gopls.
	promptForMissingTool('gopls');
}

function allFoldersHaveSameGopath(): boolean {
	if (!vscode.workspace.workspaceFolders || vscode.workspace.workspaceFolders.length <= 1) {
		return true;
	}
	const tempGopath = getCurrentGoPath(vscode.workspace.workspaceFolders[0].uri);
	return vscode.workspace.workspaceFolders.find((x) => tempGopath !== getCurrentGoPath(x.uri)) ? false : true;
}

const acceptGoplsPrerelease = false;
const defaultLatestVersion = semver.coerce('0.4.0');
const defaultLatestVersionTime = moment('2020-04-08', 'YYYY-MM-DD');
async function shouldUpdateLanguageServer(
	tool: Tool,
	languageServerToolPath: string,
	makeProxyCall: boolean
): Promise<semver.SemVer> {
	// Only support updating gopls for now.
	if (tool.name !== 'gopls') {
		return null;
	}

	// First, run the "gopls version" command and parse its results.
	const usersVersion = await goplsVersion(languageServerToolPath);

	// We might have a developer version. Don't make the user update.
	if (usersVersion === '(devel)') {
		return null;
	}

	// Get the latest gopls version.
	let latestVersion = makeProxyCall ? await latestGopls(tool) : defaultLatestVersion;

	// If we failed to get the gopls version, pick the one we know to be latest at the time of this extension's last update
	if (!latestVersion) {
		latestVersion = defaultLatestVersion;
	}

	// If "gopls" is so old that it doesn't have the "gopls version" command,
	// or its version doesn't match our expectations, usersVersion will be empty.
	// Suggest the latestVersion.
	if (!usersVersion) {
		return latestVersion;
	}

	// The user may have downloaded golang.org/x/tools/gopls@master,
	// which means that they have a pseudoversion.
	const usersTime = parsePseudoversionTimestamp(usersVersion);
	// If the user has a pseudoversion, get the timestamp for the latest gopls version and compare.
	if (usersTime) {
		let latestTime = makeProxyCall ? await goplsVersionTimestamp(tool, latestVersion) : defaultLatestVersionTime;
		if (!latestTime) {
			latestTime = defaultLatestVersionTime;
		}
		return usersTime.isBefore(latestTime) ? latestVersion : null;
	}

	// If the user's version does not contain a timestamp,
	// default to a semver comparison of the two versions.
	return semver.lt(usersVersion, latestVersion) ? latestVersion : null;
}

// Copied from src/cmd/go/internal/modfetch.
const pseudoVersionRE = /^v[0-9]+\.(0\.0-|\d+\.\d+-([^+]*\.)?0\.)\d{14}-[A-Za-z0-9]+(\+incompatible)?$/;

// parsePseudoVersion reports whether v is a pseudo-version.
// The timestamp is the center component, and it has the format "YYYYMMDDHHmmss".

function parsePseudoversionTimestamp(version: string): moment.Moment {
	const split = version.split('-');
	if (split.length < 2) {
		return null;
	}
	if (!semver.valid(version)) {
		return null;
	}
	if (!pseudoVersionRE.test(version)) {
		return null;
	}
	const sv = semver.coerce(version);
	if (!sv) {
		return null;
	}
	// Copied from src/cmd/go/internal/modfetch.go.
	const build = sv.build.join('.');
	const buildIndex = version.lastIndexOf(build);
	if (buildIndex >= 0) {
		version = version.substring(0, buildIndex);
	}
	const lastDashIndex = version.lastIndexOf('-');
	version = version.substring(0, lastDashIndex);
	const firstDashIndex = version.lastIndexOf('-');
	const dotIndex = version.lastIndexOf('.');
	let timestamp: string;
	if (dotIndex > firstDashIndex) {
		// "vX.Y.Z-pre.0" or "vX.Y.(Z+1)-0"
		timestamp = version.substring(dotIndex + 1);
	} else {
		// "vX.0.0"
		timestamp = version.substring(firstDashIndex + 1);
	}
	return moment.utc(timestamp, 'YYYYMMDDHHmmss');
}

async function goplsVersionTimestamp(tool: Tool, version: semver.SemVer): Promise<moment.Moment> {
	const data = await goProxyRequest(tool, `v${version.format()}.info`);
	if (!data) {
		return null;
	}
	const time = moment(data['Time']);
	return time;
}

async function latestGopls(tool: Tool): Promise<semver.SemVer> {
	// If the user has a version of gopls that we understand,
	// ask the proxy for the latest version, and if the user's version is older,
	// prompt them to update.
	const data = await goProxyRequest(tool, 'list');
	if (!data) {
		return null;
	}
	// Coerce the versions into SemVers so that they can be sorted correctly.
	const versions = [];
	for (const version of data.trim().split('\n')) {
		const parsed = semver.parse(version, {
			includePrerelease: true,
			loose: true
		});
		if (parsed) {
			versions.push(parsed);
		}
	}
	if (versions.length === 0) {
		return null;
	}
	versions.sort(semver.rcompare);

	if (acceptGoplsPrerelease) {
		return versions[0]; // The first one (newest one).
	}
	// The first version in the sorted list without a prerelease tag.
	return versions.find((version) => !version.prerelease || !version.prerelease.length);
}

async function goplsVersion(goplsPath: string): Promise<string> {
	const env = getToolsEnvVars();
	const execFile = util.promisify(cp.execFile);
	let output: any;
	try {
		const { stdout } = await execFile(goplsPath, ['version'], { env });
		output = stdout;
	} catch (e) {
		// The "gopls version" command is not supported, or something else went wrong.
		// TODO: Should we propagate this error?
		return null;
	}

	const lines = <string>output.trim().split('\n');
	switch (lines.length) {
		case 0:
			// No results, should update.
			// Worth doing anything here?
			return null;
		case 1:
			// Built in $GOPATH mode. Should update.
			// TODO: Should we check the Go version here?
			// Do we even allow users to enable gopls if their Go version is too low?
			return null;
		case 2:
			// We might actually have a parseable version.
			break;
		default:
			return null;
	}

	// The second line should be the sum line.
	// It should look something like this:
	//
	//    golang.org/x/tools/gopls@v0.1.3 h1:CB5ECiPysqZrwxcyRjN+exyZpY0gODTZvNiqQi3lpeo=
	//
	// TODO: We should use a regex to match this, but for now, we split on the @ symbol.
	// The reasoning for this is that gopls still has a golang.org/x/tools/cmd/gopls binary,
	// so users may have a developer version that looks like "golang.org/x/tools@(devel)".
	const moduleVersion = lines[1].trim().split(' ')[0];

	// Get the relevant portion, that is:
	//
	//    golang.org/x/tools/gopls@v0.1.3
	//
	const split = moduleVersion.trim().split('@');
	if (split.length < 2) {
		return null;
	}
	// The version comes after the @ symbol:
	//
	//    v0.1.3
	//
	return split[1];
}

async function goProxyRequest(tool: Tool, endpoint: string): Promise<any> {
	const proxies = goProxy();
	// Try each URL set in the user's GOPROXY environment variable.
	// If none is set, don't make the request.
	for (const proxy of proxies) {
		if (proxy === 'direct') {
			continue;
		}
		const url = `${proxy}/${tool.importPath}/@v/${endpoint}`;
		let data: string;
		try {
			data = await WebRequest.json<string>(url, {
				throwResponseError: true
			});
		} catch (e) {
			return null;
		}
		return data;
	}
	return null;
}

function goProxy(): string[] {
	const output: string = process.env['GOPROXY'];
	if (!output || !output.trim()) {
		return [];
	}
	const split = output.trim().split(',');
	return split;
}