Slack slash command

Package.resolved

@@ -1,12 +1,21 @@
 {
   "pins" : [
+    {
+      "identity" : "cryptoswift",
+      "kind" : "remoteSourceControl",
+      "location" : "https://github.com/GoodNotes/CryptoSwift.git",
+      "state" : {
+        "branch" : "swiftwasm-support",
+        "revision" : "a8bc733bc578312b1a507da3417f92d311e3143d"
+      }
+    },
     {
       "identity" : "swift-compute-runtime",
       "kind" : "remoteSourceControl",
       "location" : "https://github.com/AndrewBarba/swift-compute-runtime",
       "state" : {
         "branch" : "main",
-        "revision" : "8c84156b144fc44ce758ea7745f9d0c902520904"
+        "revision" : "184a97d61249cb274491e2bde455667bc521ca47"
       }
     }
   ],

Package.swift

@@ -9,6 +9,7 @@ let package = Package(
     ],
     dependencies: [
          .package(url: "https://github.com/AndrewBarba/swift-compute-runtime", branch: "main"),
+         .package(url: "https://github.com/GoodNotes/CryptoSwift.git", branch: "swiftwasm-support"),
     ],
     targets: [
         .executableTarget(
@@ -22,6 +23,13 @@ let package = Package(
         .executableTarget(
             name: "Rest",
             dependencies: [.product(name: "Compute", package: "swift-compute-runtime")]
-        )
+        ),
+        .executableTarget(
+            name: "SlackCommand",
+            dependencies: [
+                .product(name: "Compute", package: "swift-compute-runtime"),
+                .product(name: "CryptoSwift", package: "CryptoSwift"),
+            ]
+        ),
     ]
 )

Sources/SlackCommand/File.swift

@@ -0,0 +1,88 @@
+import Compute
+import Foundation
+import CryptoSwift
+
+extension String: Error {}
+
+struct MessagePayload: Codable {
+    var text: String?
+    var responseType: String?
+}
+
+@main
+struct App {
+    static func main() async throws {
+        try await onIncomingRequest(router.run)
+    }
+
+    static let router = Router()
+        .get("/status") { req, res in
+            try await res.status(.ok).send("OK")
+        }
+
+        .post("/webhook") { req, res in
+            let signature = req.headers.get("X-Slack-Signature")
+            let timestamp = req.headers.get("X-Slack-Request-Timestamp")
+            let version = "v0" // slack version number is always "v0" right now
+
+            print("X-Slack-Request-Timestamp -> \(timestamp ?? "")")
+
+            let env = try Compute.Dictionary(name: "env")
+            let secret = env.get("SLACK_SIGNING_SECRET")
+            let rawBody = try await req.body.text()
+
+            func validateSignature(payload: [UInt8]) async throws -> Bool {
+               guard let secret = secret else {
+                 // noop for development
+                 return false
+               }
+               let hmac = try HMAC(key: secret, variant: .sha2(.sha256))
+               let expected = try "\(version)=" + hmac.authenticate(payload).toHexString()
+
+               print("[validateSignature] expected -> \(expected)")
+               print("[validateSignature] signature -> \(signature ?? "")")
+               return signature == expected
+            }
+
+            let payload = "\(version):\(timestamp!):\(rawBody)"
+
+            guard try await validateSignature(payload: payload.bytes) else {
+                return try await res.status(.unauthorised).send("Invalid request")
+            }
+
+            let formDict = try await req.body.formValues()
+
+            guard let slackWebhookURL = formDict["response_url"] else {
+                return try await res.status(.badRequest).send("Missing response_url")
+            }
+
+            guard let userName = formDict["user_name"] else {
+                return try await res.status(.badRequest).send("Missing user_name")
+            }
+
+            print("slackWebhookURL -> \(slackWebhookURL)")
+            print("userName -> \(userName)")
+
+            let response = try await fetch(
+                slackWebhookURL,
+                .options(
+                    method: .post,
+                    body: .json([
+                        "text": "Hello, \(userName.capitalized)",
+                        "response_type": "in_channel"
+                    ])
+                )
+            )
+
+            try await res.status(.ok).send()
+        }
+
+        .get("/test") { req, res in
+            let messageBody = MessagePayload(text: "Test", responseType: "ephemeral")
+            let encoder = JSONEncoder()
+            encoder.keyEncodingStrategy = .convertToSnakeCase
+            let encodedMessageBody = try encoder.encode(messageBody)
+            try await res.status(.ok).send(messageBody, encoder: encoder)
+        }
+
+}