// tools/lsp/vscode-extension/extension.js — El Language VSCode extension
//
// Launches el-lsp as a child process (stdin/stdout Language Server Protocol)
// and connects VSCode's language client to it.
//
// Prerequisites:
//   - el-lsp binary built at ../dist/el-lsp  (run tools/lsp/build.sh first)
//   - npm install  (installs vscode-languageclient)
//
// Install for development:
//   1. Open the vscode-extension/ folder in VSCode
//   2. Press F5 — Extension Development Host launches
//   3. Open any .el file — the LSP activates
//
// To package as a .vsix:
//   npm install -g @vscode/vsce
//   cd tools/lsp/vscode-extension && vsce package

'use strict';

const path = require('path');
const { workspace, window, ExtensionContext } = require('vscode');
const {
    LanguageClient,
    TransportKind,
} = require('vscode-languageclient/node');

let client;

/**
 * activate — called when a .el file is first opened.
 * Resolves the el-lsp binary path and starts the language client.
 *
 * @param {ExtensionContext} context
 */
function activate(context) {
    // Resolve el-lsp binary path.
    // Default: ../dist/el-lsp relative to this extension root.
    // Override with the "el.lspPath" workspace setting.
    const config = workspace.getConfiguration('el');
    const defaultLspPath = path.join(context.extensionPath, '..', 'dist', 'el-lsp');
    const serverPath = config.get('lspPath', defaultLspPath);

    // ServerOptions: run el-lsp as a child process over stdin/stdout.
    const serverOptions = {
        run: {
            command: serverPath,
            transport: TransportKind.stdio,
        },
        debug: {
            command: serverPath,
            transport: TransportKind.stdio,
            // In debug mode you could add --verbose or redirect stderr to a
            // log file for inspection.  For now debug == run.
        },
    };

    // ClientOptions: handle all files with language id "el".
    const clientOptions = {
        documentSelector: [
            { scheme: 'file', language: 'el' },
            { scheme: 'untitled', language: 'el' },
        ],
        synchronize: {
            // Re-send full document on save (matches textDocumentSync: 1).
            fileEvents: workspace.createFileSystemWatcher('**/*.el'),
        },
        // Output channel for LSP messages (visible in Output → El Language Server).
        outputChannelName: 'El Language Server',
    };

    client = new LanguageClient(
        'el-language-server',
        'El Language Server',
        serverOptions,
        clientOptions
    );

    // Start the client (and the server as its child process).
    client.start();

    // Notify user on activation.
    window.showInformationMessage('El Language Server started.');
}

/**
 * deactivate — called when the extension is unloaded.
 * Stops the language client (sends LSP shutdown + exit).
 */
function deactivate() {
    if (!client) {
        return undefined;
    }
    return client.stop();
}

module.exports = { activate, deactivate };