extension.js

const vscode = require('vscode');
const fs = require('fs');
const path = require('path');

function activate(context) {
    console.log("Extension 'simple-fits-viewer' is now active!");
    context.subscriptions.push(
        vscode.window.registerCustomEditorProvider('fitFileViewer', new FITSFileEditor(context))
    );
}

class FITSFileDocument {
    constructor(uri) {
        this.uri = uri;
    }
}

class FITSFileEditor {
    constructor(context) {
        this.context = context;
    }

    openCustomDocument(uri, openContext, token) {
        return new FITSFileDocument(uri);
    }

    async resolveCustomEditor(document, webviewPanel, token) {

        // Set up the webview content
        webviewPanel.webview.options = {
            enableScripts: true,
            localResourceRoots: [
                vscode.Uri.file(path.dirname(document.uri.fsPath))
            ]
        };

        // Function to update webview content
        const updateWebview = () => {
            try {
                // Step 1: Update the webview content
                webviewPanel.webview.html = this.getWebviewContent();

                // Step 2: Send data to webview (SLOW?)
                webviewPanel.webview.onDidReceiveMessage(
                    message => {
                        if (message.command === 'ready') {
                            // Convert the document URI to a webview URI
                            const fitsFileUri = webviewPanel.webview.asWebviewUri(document.uri);

                            // Send the data to the webview
                            webviewPanel.webview.postMessage({
                                command: 'loadData',
                                fileUri: fitsFileUri.toString()
                            });
                        }
                    },
                    undefined,
                    this.context.subscriptions
                );

            } catch (error) {
                console.log(error);
                vscode.window.showErrorMessage(`Error reading FITS file: ${error.message}`);
            }
        };

        // Initial update
        updateWebview();

        // Handle document changes
        const changeDocumentSubscription = vscode.workspace.onDidChangeTextDocument(event => {
            if (event.document.uri.toString() === document.uri.toString()) {
                updateWebview();
            }
        });

        // Clean up subscription when panel is disposed
        webviewPanel.onDidDispose(() => {
            changeDocumentSubscription.dispose();
        });
    }

    getWebviewContent() {
        const filePath = path.join(__dirname, 'webview.html');
        let content = fs.readFileSync(filePath, 'utf8');

        // Attach utils.js
        const utilsPath = path.join(__dirname, 'utils.js');
        const utilsContent = fs.readFileSync(utilsPath, 'utf8');

        // Attach styles.css
        const stylePath = path.join(__dirname, 'style.css');
        const styleContent = fs.readFileSync(stylePath, 'utf8');

        // Inject utils.js and styles.css content into the webview HTML
        content = content.replace('</body>', `<script>${utilsContent}</script><style>${styleContent}</style></body>`);
        return content;
    }
}

exports.activate = activate;

function deactivate() { }

module.exports = {
    activate,
    deactivate
}