From e8e3c4cba8ffa0056e984c113cfbb75319e00022 Mon Sep 17 00:00:00 2001
From: Jake Mannens <jake@asger.xyz>
Date: Fri, 20 Sep 2024 16:21:09 +1000
Subject: v0.4-rc1

---
 PagerHandler.cs | 125 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 125 insertions(+)
 create mode 100644 PagerHandler.cs

(limited to 'PagerHandler.cs')

diff --git a/PagerHandler.cs b/PagerHandler.cs
new file mode 100644
index 0000000..8520064
--- /dev/null
+++ b/PagerHandler.cs
@@ -0,0 +1,125 @@
+using System.Reflection;
+
+namespace PagerParser;
+
+[AttributeUsage(AttributeTargets.Class, AllowMultiple = true, Inherited = false)]
+public class PagerHandlerAttribute : Attribute {}
+
+public interface IPagerHandler {
+    public void OnConfiguring(
+        ILogger logger,
+        IConfiguration config,
+        IServiceProvider serviceProvider);
+
+    public Task StartAsync(CancellationToken ct);
+    public Task StopAsync(CancellationToken ct);
+
+    public Task HandleMessageAsync(
+        PagerMessage message,
+        ParsedPagerMessage? parsedMessage);
+}
+
+public interface IRootPagerHandler {
+    public Task HandleMessageAsync(
+        PagerMessage message,
+        ParsedPagerMessage? parsedMessage);
+}
+
+public class RootPagerHandler : IRootPagerHandler, IHostedService {
+    private readonly HandlerEntry[] handlers;
+
+    private readonly ILogger<RootPagerHandler> logger;
+
+    public RootPagerHandler(IServiceProvider serviceProvider) {
+        handlers = typeof(RootPagerHandler).Assembly.GetTypes()
+            .Where(t => t.IsClass)
+            .Where(t => t.IsAssignableTo(typeof(IPagerHandler)))
+            .Where(t => t.GetCustomAttributes<PagerHandlerAttribute>().Any())
+            .Select(t => Activator.CreateInstance(t))
+            .Cast<IPagerHandler>()
+            .Select(h => new HandlerEntry(h))
+            .ToArray();
+
+        var config = serviceProvider.GetRequiredService<IConfiguration>();
+
+        logger = serviceProvider.GetRequiredService<ILogger<RootPagerHandler>>();
+
+        foreach(var entry in handlers) {
+            var name       = entry.Handler.GetType().Name;
+            var loggerType = typeof(ILogger<>).MakeGenericType(entry.GetType());
+            var logger     = serviceProvider.GetRequiredService(loggerType);
+            try {
+                this.logger.LogDebug($"Configuring page handler: {name}");
+                entry.Handler.OnConfiguring((ILogger) logger, config, serviceProvider);
+            } catch {
+                // TODO: include exceptions in log on failure
+                this.logger.LogWarning($"Failed to configure page handler: {name}");
+                entry.State = HandlerState.Failed;
+            }
+        }
+    }
+
+    public async Task StartAsync(CancellationToken ct) {
+        logger.LogInformation("Root pager handler service starting...");
+        await Task.WhenAll(
+            handlers.Select(async e => {
+                var name = e.Handler.GetType().Name;
+                if(e.State != HandlerState.Stopped)
+                    return;
+                logger.LogDebug($"Starting page handler: {name}");
+                try {
+                    await e.Handler.StartAsync(ct);
+                    e.State = HandlerState.Started;
+                } catch {
+                    logger.LogWarning($"Failed to start page handler: {name}");
+                    e.State = HandlerState.Failed;
+                }
+            }).ToArray());
+    }
+
+    public async Task StopAsync(CancellationToken ct) {
+        logger.LogInformation("Root pager handler service stopping...");
+        await Task.WhenAll(
+            handlers.Select(async e => {
+                var name = e.Handler.GetType().Name;
+                if(e.State != HandlerState.Started)
+                    return;
+                logger.LogDebug($"Stopping page handler: {name}");
+                try {
+                    await e.Handler.StopAsync(ct);
+                    e.State = HandlerState.Stopped;
+                } catch {
+                    logger.LogWarning($"Failed to stop page handler: {name}");
+                    e.State = HandlerState.Failed;
+                }
+            }).ToArray());
+    }
+
+    public async Task HandleMessageAsync(PagerMessage m, ParsedPagerMessage? pm) {
+        await Task.WhenAll(
+            handlers
+                .Where(e => e.State == HandlerState.Started)
+                .Select(async e => {
+                    var name = e.Handler.GetType().Name;
+                    try {
+                        await e.Handler.HandleMessageAsync(m, pm);
+                    } catch {
+                        logger.LogWarning($"Page handler {name} failed to handle pager message");
+                    }
+                }).ToArray());
+    }
+
+    private record HandlerEntry {
+        public IPagerHandler Handler { get; set; }
+        public HandlerState  State   { get; set; } = HandlerState.Stopped;
+
+        public HandlerEntry(IPagerHandler handler) =>
+            Handler = handler;
+    }
+
+    private enum HandlerState {
+        Stopped,
+        Started,
+        Failed
+    }
+}
-- 
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