Add image generation

HomeApi/Handlers/ImageGeneration.cs

@@ -0,0 +1,75 @@
+using System.Reflection;
+using HomeApi.Models;
+using HomeApi.Models.Configuration;
+using MediatR;
+using Microsoft.AspNetCore.Http.HttpResults;
+using Microsoft.Extensions.Options;
+using PuppeteerSharp;
+using RazorLight;
+
+namespace HomeApi.Handlers;
+
+public static class ImageGeneration
+{
+    public record Command : IRequest<Stream>;
+
+    public class Handler : IRequestHandler<Command, Stream>
+    {
+        private readonly ILogger<Handler> _logger;
+        private readonly IWebHostEnvironment _env;
+        private readonly IMediator _mediator;
+        public Handler(
+            IOptions<ApiConfiguration> apiConfiguration,
+            ILogger<Handler> logger, IWebHostEnvironment env, IMediator mediator)
+        {
+            _logger = logger;
+            _env = env;
+            _mediator = mediator;
+        }
+
+        public async Task<Stream> Handle(Command request, CancellationToken cancellationToken)
+        {
+            var weather = await _mediator.Send(new Weather.Command(), cancellationToken);
+            var departureBoard = await _mediator.Send(new DepartureBoard.Command(), cancellationToken);
+            
+            var model = new Image
+            {
+                Weather = weather,
+                TimeTable = departureBoard
+            };
+            
+            if(weather is null)
+                throw new Exception("Weather data not found");
+            
+            var engine = new RazorLightEngineBuilder().SetOperatingAssembly(Assembly.GetExecutingAssembly())
+                .UseEmbeddedResourcesProject(typeof(ImageGeneration)).UseMemoryCachingProvider().Build();
+            var path = Path.Combine(_env.WebRootPath, "index.cshtml");
+            
+            var template = await File.ReadAllTextAsync(path);
+
+            var result = await engine.CompileRenderStringAsync("templateKey", template, model);
+
+            return await CreateImage(result);
+        }
+
+        private static async Task<Stream> CreateImage(string htmlContent)
+        {
+            var browserFetcher = new BrowserFetcher();
+            await browserFetcher.DownloadAsync();
+            var browser = await Puppeteer.LaunchAsync(new LaunchOptions
+            {
+                Headless = true,
+                Args = ["--disable-gpu"]
+            });
+            var page = await browser.NewPageAsync();
+            await page.SetViewportAsync(new ViewPortOptions
+            {
+                Width = 800,
+                Height = 480
+            });
+            await page.SetContentAsync(htmlContent, new NavigationOptions { WaitUntil = new[] { WaitUntilNavigation.Networkidle0 } });
+            var stream = await page.ScreenshotStreamAsync(new ScreenshotOptions { Type = ScreenshotType.Png });
+            return stream;
+        }
+    }
+}