feat: add command line to convert files (#24)

Co-authored-by: Tremper, Diego (ESI) <diego.tremper@adp.com>

README.md

@@ -62,6 +62,21 @@ If set to `false`, converts the provided schema in place. If `true`, clones the
 
 If set to `true`, all local and remote references (http/https and file) $refs will be dereferenced. Defaults to `false`.
 
+## Command Line
+
+```sh
+Usage:
+    json-schema-to-openapi-schema <command> [options] <file>
+
+Commands:
+    convert                 Converts JSON Schema Draft 04 to OpenAPI 3.0 Schema Object
+
+Options:
+    -h, --help              Show help for any command
+    -v, --version           Output the CLI version number
+    -d, --dereference       If set all local and remote references (http/https and file) $refs will be dereferenced
+```
+
 ## Why?
 
 OpenAPI is often described as an extension of JSON Schema, but both specs have changed over time and grown independently. OpenAPI v2 was based on JSON Schema draft v4 with a long list of deviations, but OpenAPI v3 shrank that list, upping their support to draft v4 and making the list of discrepancies shorter. This has been solved for OpenAPI v3.1, but for those using OpenAPI v3.0, you can use this tool to solve [the divergence](https://apisyouwonthate.com/blog/openapi-and-json-schema-divergence).

bin/help-text.json

@@ -0,0 +1,26 @@
+{
+  "default": [
+    "Usage:",
+    "    json-schema-to-openapi-schema <command> [options] <file>",
+    "",
+    "Commands:",
+    "    convert                 Converts JSON Schema Draft 04 to OpenAPI 3.0 Schema Object",
+    "",
+    "Options:",
+    "    -h, --help              Show help for any command",
+    "    -v, --version           Output the CLI version number",
+    "    -d, --dereference       If set all local and remote references (http/https and file) $refs will be dereferenced",
+    ""
+  ],
+  "convert": [
+    "Converts JSON Schema Draft 04 to OpenAPI 3.0 Schema Object.",
+    "Returns a non-zero exit code if conversion fails.",
+    "",
+    "Usage:",
+    "    json-schema-to-openapi-schema convert [options] <file>",
+    "",
+    "Options:",
+    "    -d, --dereference       If set all local and remote references (http/https and file) $refs will be dereferenced",
+    ""
+  ]
+}

bin/json-schema-to-openapi-schema.js

@@ -0,0 +1,117 @@
+#!/usr/bin/env node
+"use strict";
+
+const yargs = require("yargs");
+const chalk = require("chalk");
+const converter = require("..");
+const helpText = require("./help-text.json");
+const fs = require('fs');
+const readFileAsync = require('util').promisify(fs.readFile);
+
+(function main () {
+  let args = parseArgs();
+  let command = args.command;
+  let file = args.file;
+  let options = args.options;
+
+  if (options.help) {
+    // Show help text and exit
+    console.log(getHelpText(command));
+    process.exit(0);
+  }
+  else if (command === "convert" && file) {
+    // Convert the JSON Schema file
+    convert(file, options);
+  }
+  else {
+    // Invalid args.  Show help text and exit with non-zero
+    console.error("Error: Invalid arguments\n");
+    console.error(getHelpText(command));
+    process.exit(1);
+  }
+}());
+
+
+/**
+ * Parses the command-line arguments
+ *
+ * @returns {object} - The parsed arguments
+ */
+function parseArgs () {
+  // Configure the argument parser
+  yargs
+    .option("d", {
+      alias: "dereference",
+      type: "boolean",
+      default: false,
+    })
+    .option("h", {
+      alias: "help",
+      type: "boolean",
+    });
+
+  // Show the version number on "--version" or "-v"
+  yargs
+    .version()
+    .alias("v", "version");
+
+  // Disable the default "--help" behavior
+  yargs.help(false);
+
+  // Parse the command-line arguments
+  let args = yargs.argv;
+
+  // Normalize the parsed arguments
+  let parsed = {
+    command: args._[0],
+    file: args._[1],
+    options: {
+      dereference: args.dereference,
+      help: args.help,
+    }
+  };
+
+  return parsed;
+}
+
+
+/**
+ * Convert an JSON Schema to OpenAPI schema
+ *
+ * @param {string} file - The path of the file to convert
+ * @param {object} options - Conversion options
+ */
+async function convert (file, options) {
+  try {
+    const schema = await readFileAsync(file, 'utf8');
+    const converted = await converter(JSON.parse(schema), options)
+    console.log(JSON.stringify(converted));
+  }
+  catch (error) {
+    errorHandler(error);
+  }
+}
+
+
+/**
+ * Returns the help text for the specified command
+ *
+ * @param {string} [commandName] - The command to show help text for
+ * @returns {string} - the help text
+ */
+function getHelpText (commandName) {
+  let lines = helpText[commandName] || helpText.default;
+  return lines.join("\n");
+}
+
+
+/**
+ * Writes error information to stderr and exits with a non-zero code
+ *
+ * @param {Error} err
+ */
+function errorHandler (err) {
+  let errorMessage = process.env.DEBUG ? err.stack : err.message;
+  console.error(chalk.red(errorMessage));
+  process.exit(1);
+}