Add a cli to the package

Ref #51

README.md

@@ -10,6 +10,24 @@ The CLASS web application is available at https://classmodel.github.io/class-web
 
 For more information on CLASS, see https://classmodel.github.io/.
 
+## Command line usage
+
+The class model can be run from the command line.
+The argument is the config file that should adhere to the [JSON schema](./packages/class/src/config.json).
+
+```shell
+pnpx --package=@classmodel/class class config.json
+# Outputs h variable for each timestep
+```
+
+(in development use `pnpx tsx src/cli.ts ./config.json`)
+
+To use the reference configuration of a experiment downloaded from the web application use.
+
+```shell
+jq .reference < ~/Downloads/class-MyExperiment.json  > config.json
+```
+
 ## Developers
 
 This repository is a so-called monorepo, where multiple packages and application

packages/class/package.json

@@ -3,6 +3,7 @@
   "version": "0.0.3",
   "exports": {
     "./class": "./src/class.ts",
+    "./cli": "./src/cli.ts",
     "./config": "./src/config.ts",
     "./config.json": "./src/config.json",
     "./runner": "./src/runner.ts",
@@ -24,6 +25,9 @@
   "dependencies": {
     "ajv": "^8.17.1"
   },
+  "bin": {
+    "class": "./src/cli.ts"
+  },
   "engines": {
     "node": ">=20.16.0"
   }

packages/class/src/cli.ts

@@ -0,0 +1,27 @@
+#!/usr/bin/env node
+
+import fs from "node:fs";
+import { runClass } from "./runner";
+import { parse } from "./validate";
+
+function main() {
+  const args = process.argv.slice(2);
+  if (args.length === 0) {
+    console.error("Usage: class <config-file.json>");
+    process.exit(1);
+  }
+
+  try {
+    const configFile = args[0];
+    const configAsString = fs.readFileSync(configFile, "utf-8");
+    const rawConfig = JSON.parse(configAsString);
+    const config = parse(rawConfig);
+    const output = runClass(config);
+    console.log(JSON.stringify(output, null, 2));
+  } catch (error) {
+    console.error("Error running class:", error);
+    process.exit(1);
+  }
+}
+
+main();