NostrScript

NostrScript is a WebAssembly implementation that interacts with Damus.
It enables dynamic scripting that can be used to power custom list views,
enabling pluggable algorithms.

The web has JavaScript, Damus has NostrScript. NostrScripts can be
written in any language that compiles to WASM.

This commit adds a WASM interpreter I've written as a mostly-single C
file for portability and embeddability. In the future we could
JIT-compile these for optimal performance if NostrScripts get large and
complicated. For now an interpreter is simple enough for algorithm list
view plugins.

Changelog-Added: Add initial NostrScript implementation
Signed-off-by: William Casarin <jb55@jb55.com>

damusTests/NostrScriptTests.swift

@@ -0,0 +1,83 @@
+//
+//  NostrScriptTests.swift
+//  damusTests
+//
+//  Created by William Casarin on 2023-06-02.
+//
+
+import XCTest
+@testable import damus
+
+final class NostrScriptTests: XCTestCase {
+
+    override func setUpWithError() throws {
+        // Put setup code here. This method is called before the invocation of each test method in the class.
+    }
+
+    override func tearDownWithError() throws {
+        // Put teardown code here. This method is called after the invocation of each test method in the class.
+    }
+    
+    func loadTestWasm() throws -> Data {
+        let bundle = Bundle(for: type(of: self))
+        guard let fileURL = bundle.url(forResource: "primal", withExtension: "wasm") else {
+            throw CocoaError(.fileReadNoSuchFile)
+        }
+        
+        return try Data(contentsOf: fileURL)
+    }
+
+    func test_nostrscript() throws {
+        var data = try loadTestWasm().bytes
+        let pool = RelayPool()
+        let script = NostrScript(pool: pool)
+        
+        let load_err = script.load(wasm: &data)
+        XCTAssertNil(load_err)
+        
+        let res = script.run()
+        switch res {
+        case .finished: XCTAssert(false)
+        case .runtime_err: XCTAssert(false)
+        case .suspend:
+            XCTAssertEqual(script.waiting_on, .event("sidebar_trending"))
+            break
+        }
+        
+        let resume_expected = XCTestExpectation(description: "we got ")
+        pool.register_handler(sub_id: "sidebar_trending") { (relay_id, conn) in
+            if script.runstate?.exited == true {
+                pool.disconnect()
+                resume_expected.fulfill()
+                return
+            }
+            
+            guard case .nostr_event(let resp) = conn else {
+                return
+            }
+            
+            let with: NScriptResumeWith = .event(resp)
+            guard let res = script.resume(with: with) else {
+                return
+            }
+            
+            switch res {
+            case .finished: break
+            case .runtime_err: XCTAssert(false)
+            case .suspend: break
+            }
+        }
+        
+        pool.connect(to: ["wss://cache3.primal.net/cache15"])
+        
+        self.wait(for: [resume_expected], timeout: 10.0)
+    }
+
+    func testPerformanceExample() throws {
+        // This is an example of a performance test case.
+        self.measure {
+            // Put the code you want to measure the time of here.
+        }
+    }
+
+}