chroma/cmd/chromad/static/chroma.js

// chroma.js - TinyGo WASM runtime initialization for Chroma syntax highlighter

// Import wasm_exec.js so that it initialises the Go WASM runtime.
import "./wasm_exec.js";

class ChromaWASM {
  constructor() {
    this.go = null;
    this.wasm = null;
    this.ready = false;
    this.readyPromise = this.init();
  }

  async init() {
    try {
      // Create a new Go instance
      this.go = new Go();

      // Load the WASM module
      const wasmResponse = await fetch("./static/chroma.wasm");
      if (!wasmResponse.ok) {
        throw new Error(`Failed to fetch chroma.wasm: ${wasmResponse.status}`);
      }

      const wasmBytes = await wasmResponse.arrayBuffer();
      const wasmModule = await WebAssembly.instantiate(
        wasmBytes,
        this.go.importObject,
      );

      this.wasm = wasmModule.instance;

      // Run the Go program
      this.go.run(this.wasm);

      this.ready = true;
      console.log("Chroma WASM module initialized successfully");
    } catch (error) {
      console.error("Failed to initialize Chroma WASM module:", error);
      throw error;
    }
  }

  async waitForReady() {
    await this.readyPromise;
    if (!this.ready) {
      throw new Error("Chroma WASM module failed to initialize");
    }
  }

  async highlight(source, lexer, formatter, withClasses) {
    await this.waitForReady();

    if (typeof window.highlight !== "function") {
      throw new Error("highlight function not available from WASM module");
    }

    try {
      return window.highlight(source, lexer, formatter, withClasses);
    } catch (error) {
      console.error("Error calling highlight function:", error);
      throw error;
    }
  }
}

export function isWasmSupported() {
  try {
    if (
      typeof WebAssembly === "object" &&
      typeof WebAssembly.instantiate === "function"
    ) {
      // The smallest possible WebAssembly module (magic number + version)
      const module = new WebAssembly.Module(
        Uint8Array.of(0x0, 0x61, 0x73, 0x6d, 0x01, 0x00, 0x00, 0x00),
      );
      if (module instanceof WebAssembly.Module) {
        // Try to instantiate the module to ensure it's truly runnable
        return new WebAssembly.Instance(module) instanceof WebAssembly.Instance;
      }
    }
  } catch (e) {
    // An error occurred (e.g., due to CSP or other restrictions)
  }
  return false;
}

// Create global instance, null if WASM is not supported.
export const chroma = isWasmSupported() ? new ChromaWASM() : null;