feat: format command to convert asyncapi document to multiple format

.prettierrc

@@ -0,0 +1,3 @@
+{
+    "singleQuote": true
+}

src/commands/format.ts

@@ -0,0 +1,121 @@
+/* eslint-disable @typescript-eslint/ban-ts-comment */
+import { promises as fPromises } from 'fs';
+import { Args } from '@oclif/core';
+import Command from '../core/base';
+
+import {
+  convertToJSON,
+  convertToYaml,
+  load,
+  retrieveFileFormat,
+} from '../core/models/SpecificationFile';
+import { SpecificationWrongFileFormat } from '../core/errors/specification-file';
+import { cyan, green } from 'picocolors';
+import {
+  convertFormatFlags,
+  fileFormat,
+} from '../core/flags/format.flags';
+
+export default class Convert extends Command {
+  static specFile: any;
+  static metricsMetadata: any = {};
+  static description =
+    'Convert asyncapi documents from any format to yaml, yml or JSON';
+
+  static flags = convertFormatFlags();
+
+  static args = {
+    'spec-file': Args.string({
+      description: 'spec path, url, or context-name',
+      required: false,
+    }),
+  };
+
+  async run() {
+    const { args, flags } = await this.parse(Convert);
+    const filePath = args['spec-file'];
+    const outputFileFormat = flags['format'] as fileFormat;
+    let convertedFile;
+    try {
+      this.specFile = await load(filePath);
+      // eslint-disable-next-line sonarjs/no-duplicate-string
+      this.metricsMetadata.to_version = flags['target-version'];
+
+      const ff = retrieveFileFormat(this.specFile.text());
+      const isSpecFileJson = ff == 'json';
+      const isSpecFileYaml = ff == 'yaml';
+
+      if (!isSpecFileJson && !isSpecFileYaml) {
+        throw new SpecificationWrongFileFormat(filePath);
+      }
+
+      convertedFile = this.handleConversion(
+        isSpecFileJson,
+        isSpecFileYaml,
+        outputFileFormat,
+      );
+
+      if (!convertedFile) return;
+      await this.handleOutput(flags.output, convertedFile, outputFileFormat);
+    } catch (err) {
+      this.error(err as Error);
+    }
+  }
+
+  private handleConversion(
+    isSpecFileJson: boolean,
+    isSpecFileYaml: boolean,
+    outputFileFormat: fileFormat,
+  ): string | undefined {
+    const text = this.specFile?.text();
+    if (isSpecFileJson && text) {
+      if (outputFileFormat == 'json') {
+        throw new Error(`Your document is already a ${cyan('JSON')}`);
+      }
+      return convertToYaml(text);
+    }
+    if (isSpecFileYaml && text) {
+      if (outputFileFormat == 'yaml' || outputFileFormat == 'yml') {
+        throw new Error(`Your document is already a ${cyan('YAML')}`);
+      }
+      return convertToJSON(text);
+    }
+  }
+
+  private async handleOutput(
+    outputPath: string | undefined,
+    formattedFile: string,
+    outputFileFormat: fileFormat,
+  ) {
+    if (outputPath) {
+      outputPath = this.removeExtensionFromOutputPath(outputPath);
+      try {
+        const finalFileName = `${outputPath}.${outputFileFormat}`;
+        await fPromises.writeFile(finalFileName, formattedFile, {
+          encoding: 'utf8',
+        });
+        this.log(`converted to ${outputFileFormat} at ${green(finalFileName)}`);
+      } catch (err) {}
+    } else {
+      this.log(formattedFile);
+    }
+  }
+
+  private removeExtensionFromOutputPath(filename: string): string {
+    // Removes the extension from a filename if it is .json, .yaml, or .yml
+    // this is so that we can remove the provided extension name in the -o flag and
+    // apply our own extension name according to the content of the file
+    const validExtensions = ['json', 'yaml', 'yml'];
+
+    const parts = filename.split('.');
+
+    if (parts.length > 1) {
+      const extension = parts.pop()?.toLowerCase();
+      if (extension && validExtensions.includes(extension)) {
+        return parts.join('.');
+      }
+    }
+
+    return filename;
+  }
+}

src/core/errors/specification-file.ts

@@ -17,6 +17,13 @@ export class SpecificationFileNotFound extends SpecificationFileError {
   }
 }
 
+export class SpecificationWrongFileFormat extends SpecificationFileError {
+  constructor(filePath?: string) {
+    super();
+    this.message = `File ${filePath} is not of correct format.`;
+  }
+}
+
 export class SpecificationURLNotFound extends SpecificationFileError {
   constructor(URL: string) {
     super();

src/core/flags/format.flags.ts

@@ -0,0 +1,22 @@
+import { Flags } from '@oclif/core';
+
+export type fileFormat = 'yaml' | 'yml' | 'json';
+
+const availFileFormats: fileFormat[] = ['yaml', 'yml', 'json'];
+
+export const convertFormatFlags = () => {
+  return {
+    help: Flags.help({ char: 'h' }),
+    output: Flags.string({
+      char: 'o',
+      description: 'path to the file where the result is saved',
+    }),
+    format: Flags.string({
+      char: 'f',
+      description: 'Specify the format to convert to',
+      options: availFileFormats,
+      required: true,
+      default: 'json',
+    }),
+  };
+};

src/core/models/SpecificationFile.ts

@@ -6,6 +6,7 @@ import yaml from 'js-yaml';
 import { loadContext } from './Context';
 import { ErrorLoadingSpec } from '../errors/specification-file';
 import { MissingContextFileError } from '../errors/context-error';
+import { fileFormat } from 'core/flags/format.flags';
 
 const { readFile, lstat } = fs;
 const allowedFileNames: string[] = [
@@ -222,3 +223,39 @@ async function detectSpecFile(): Promise<string | undefined> {
   }));
   return existingFileNames.find(filename => filename !== undefined);
 }
+
+export function retrieveFileFormat(content: string): fileFormat | undefined {
+  try {
+    if (content.trimStart()[0] === '{') {
+      JSON.parse(content);
+      return 'json';
+    }
+    // below yaml.load is not a definitive way to determine if a file is yaml or not.
+    // it is able to load .txt text files also.
+    yaml.load(content);
+    return 'yaml';
+  } catch (err) {
+    return undefined;
+  }
+}
+
+export function convertToYaml(spec: string) {
+  try {
+    // JS object -> YAML string
+    const jsonContent = yaml.load(spec);
+    return yaml.dump(jsonContent);
+  } catch (err) {
+    console.error(err);
+  }
+}
+
+export function convertToJSON(spec: string) {
+  try {
+    // JSON or YAML String -> JS object
+    const jsonContent = yaml.load(spec);
+    // JS Object -> pretty JSON string
+    return JSON.stringify(jsonContent, null, 2);
+  } catch (err) {
+    console.error(err);
+  }
+}