Add build time math rendering

While very useful on its own (and combined with the passthrough render hooks), this also serves as a proof of concept of using WASI (WebAssembly System Interface) modules in Hugo.

This will be marked _experimental_ in the documentation. Not because it will be removed or changed in a dramatic way, but we need to think a little more how to best set up/configure similar services, define where these WASM files gets stored, maybe we can allow user provided WASM files plugins via Hugo Modules mounts etc.

See these issues for more context:

* https://github.com/gohugoio/hugo/issues/12736
* https://github.com/gohugoio/hugo/issues/12737

See #11927

internal/warpc/js/.gitignore

@@ -0,0 +1,2 @@
+node_modules/
+package-lock.json

internal/warpc/js/common.js

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+// Read JSONL from stdin.
+export function readInput(handle) {
+	const buffSize = 1024;
+	let currentLine = [];
+	const buffer = new Uint8Array(buffSize);
+
+	// Read all the available bytes
+	while (true) {
+		// Stdin file descriptor
+		const fd = 0;
+		let bytesRead = 0;
+		try {
+			bytesRead = Javy.IO.readSync(fd, buffer);
+		} catch (e) {
+			// IO.readSync fails with os error 29 when stdin closes.
+			if (e.message.includes('os error 29')) {
+				break;
+			}
+			throw new Error('Error reading from stdin');
+		}
+
+		if (bytesRead < 0) {
+			throw new Error('Error reading from stdin');
+			break;
+		}
+
+		if (bytesRead === 0) {
+			break;
+		}
+
+		currentLine = [...currentLine, ...buffer.subarray(0, bytesRead)];
+
+		// Split array into chunks by newline.
+		let i = 0;
+		for (let j = 0; i < currentLine.length; i++) {
+			if (currentLine[i] === 10) {
+				const chunk = currentLine.splice(j, i + 1);
+				const arr = new Uint8Array(chunk);
+				const json = JSON.parse(new TextDecoder().decode(arr));
+				handle(json);
+				j = i + 1;
+			}
+		}
+		// Remove processed data.
+		currentLine = currentLine.slice(i);
+	}
+}
+
+// Write JSONL to stdout
+export function writeOutput(output) {
+	const encodedOutput = new TextEncoder().encode(JSON.stringify(output) + '\n');
+	const buffer = new Uint8Array(encodedOutput);
+	// Stdout file descriptor
+	const fd = 1;
+	Javy.IO.writeSync(fd, buffer);
+}

internal/warpc/js/greet.bundle.js

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+(()=>{function i(r){let e=[],a=new Uint8Array(1024);for(;;){let n=0;try{n=Javy.IO.readSync(0,a)}catch(o){if(o.message.includes("os error 29"))break;throw new Error("Error reading from stdin")}if(n<0)throw new Error("Error reading from stdin");if(n===0)break;e=[...e,...a.subarray(0,n)];let t=0;for(let o=0;t<e.length;t++)if(e[t]===10){let f=e.splice(o,t+1),s=new Uint8Array(f),u=JSON.parse(new TextDecoder().decode(s));r(u),o=t+1}e=e.slice(t)}}function d(r){let c=new TextEncoder().encode(JSON.stringify(r)+`
+`),e=new Uint8Array(c);Javy.IO.writeSync(1,e)}var l=function(r){d({header:r.header,data:{greeting:"Hello "+r.data.name+"!"}})};console.log("Greet module loaded");i(l);})();

internal/warpc/js/greet.js

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+import { readInput, writeOutput } from './common';
+
+const greet = function (input) {
+	writeOutput({ header: input.header, data: { greeting: 'Hello ' + input.data.name + '!' } });
+};
+
+console.log('Greet module loaded');
+
+readInput(greet);

internal/warpc/js/package.json

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+{
+  "name": "js",
+  "version": "1.0.0",
+  "main": "greet.js",
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "author": "",
+  "license": "ISC",
+  "description": "",
+  "devDependencies": {
+    "katex": "^0.16.11"
+  }
+}

internal/warpc/js/renderkatex.js

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+import { readInput, writeOutput } from './common';
+import katex from 'katex';
+
+const render = function (input) {
+	const data = input.data;
+	const expression = data.expression;
+	const options = data.options;
+	writeOutput({ header: input.header, data: { output: katex.renderToString(expression, options) } });
+};
+
+readInput(render);