// Copyright (c) Microsoft. All rights reserved.
using System.Reflection;
using PuppeteerSharp;
namespace Utilities;
///
/// Renders Mermaid diagrams to images using Puppeteer-Sharp.
///
public static class MermaidRenderer
{
///
/// Generates a Mermaid diagram image from the provided Mermaid code.
///
///
///
///
///
public static async Task GenerateMermaidImageAsync(string mermaidCode, string filenameOrPath)
{
// Ensure the filename has the correct .png extension
if (!filenameOrPath.EndsWith(".png", StringComparison.OrdinalIgnoreCase))
{
throw new ArgumentException("The filename must have a .png extension.", nameof(filenameOrPath));
}
string outputFilePath;
// Check if the user provided an absolute path
if (Path.IsPathRooted(filenameOrPath))
{
// Use the provided absolute path
outputFilePath = filenameOrPath;
// Ensure the directory exists
string directoryPath = Path.GetDirectoryName(outputFilePath)
?? throw new InvalidOperationException("Could not determine the directory path.");
if (!Directory.Exists(directoryPath))
{
throw new DirectoryNotFoundException($"The directory '{directoryPath}' does not exist.");
}
}
else
{
// Use the assembly's directory for relative paths
string? assemblyPath = Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location);
if (assemblyPath == null)
{
throw new InvalidOperationException("Could not determine the assembly path.");
}
string outputPath = Path.Combine(assemblyPath, "output");
Directory.CreateDirectory(outputPath); // Ensure output directory exists
outputFilePath = Path.Combine(outputPath, filenameOrPath);
}
// Download Chromium if it hasn't been installed yet
BrowserFetcher browserFetcher = new();
browserFetcher.Browser = SupportedBrowser.Chrome;
await browserFetcher.DownloadAsync();
// Define the HTML template with Mermaid.js CDN
string htmlContent = $@"
{mermaidCode}
";
// Create a temporary HTML file with the Mermaid code
string tempHtmlFile = Path.Combine(Path.GetTempPath(), "mermaid_temp.html");
try
{
await File.WriteAllTextAsync(tempHtmlFile, htmlContent);
// Launch Puppeteer-Sharp with a headless browser to render the Mermaid diagram
using (var browser = await Puppeteer.LaunchAsync(new LaunchOptions { Headless = true }))
using (var page = await browser.NewPageAsync())
{
await page.GoToAsync($"file://{tempHtmlFile}");
await page.WaitForSelectorAsync(".mermaid"); // Wait for Mermaid to render
await page.ScreenshotAsync(outputFilePath, new ScreenshotOptions { FullPage = true });
}
}
catch (IOException ex)
{
throw new IOException("An error occurred while accessing the file.", ex);
}
catch (Exception ex) // Catch any other exceptions that might occur
{
throw new InvalidOperationException(
"An unexpected error occurred during the Mermaid diagram rendering.", ex);
}
finally
{
// Clean up the temporary HTML file
if (File.Exists(tempHtmlFile))
{
File.Delete(tempHtmlFile);
}
}
return outputFilePath;
}
}