From 62903ac7ead847fabd61769b219f86f9d55e5920 Mon Sep 17 00:00:00 2001
From: Gaurav Saini <gauravharyana01@gmail.com>
Date: Sat, 25 Jan 2025 22:09:14 +0530
Subject: [PATCH] introduced preview command Signed-off-by: Gourav
 <gourav.saini.phe22@iitbhu.ac.in>

---
 src/commands/start/preview.ts         | 151 ++++++++++++++++++++++++++
 src/core/flags/start/preview.flags.ts |   8 ++
 2 files changed, 159 insertions(+)
 create mode 100644 src/commands/start/preview.ts
 create mode 100644 src/core/flags/start/preview.flags.ts

diff --git a/src/commands/start/preview.ts b/src/commands/start/preview.ts
new file mode 100644
index 00000000000..dae176ff985
--- /dev/null
+++ b/src/commands/start/preview.ts
@@ -0,0 +1,151 @@
+import Command from '../../core/base';
+import { start as startStudio } from '../../core/models/Studio';
+import { load } from '../../core/models/SpecificationFile';
+import bundle from '@asyncapi/bundler';
+import path from 'path';
+import fs from 'fs';
+import { Args } from '@oclif/core';
+import chokidar from 'chokidar';
+import { previewFlags } from '../../core/flags/start/preview.flags';
+import * as yaml from 'js-yaml';
+import { NO_CONTEXTS_SAVED } from '../../core/errors/context-error';
+
+interface LocalRef {
+    filePath: string;
+    pointer: string | null;
+}
+
+class StartPreview extends Command {
+  static description =
+    'Starts Studio in preview mode with local reference files bundled and hot reloading enabled.';
+
+  static examples = [
+    'asyncapi start preview',
+    'asyncapi start preview ./asyncapi.yaml',
+    'asyncapi start preview CONTEXT_NAME'
+  ];
+
+  static flags = previewFlags();
+
+  static args = {
+    'spec-file': Args.string({
+      description: 'spec path, url, or context-name',
+      required: false,
+    }),
+  };
+
+  parseRef(ref: string): LocalRef {
+    const [filePath, pointer] = ref.split('#');
+    return {
+      filePath: filePath || '',
+      pointer: pointer || null,
+    };
+  }
+
+  findLocalRefFiles(obj: any, basePath: string, files: Set<string>): void {
+    if (typeof obj === 'object' && obj !== null) {
+      for (const [key, value] of Object.entries(obj)) {
+        if (
+          key === '$ref' &&
+                    typeof value === 'string' &&
+                    (value.startsWith('.') || value.startsWith('./') || value.startsWith('../'))
+        ) {
+          const { filePath } = this.parseRef(value);
+          const resolvedPath = path.resolve(basePath, filePath);
+
+          if (fs.existsSync(resolvedPath)) {
+            files.add(resolvedPath);
+            const referencedFile = yaml.load(
+              fs.readFileSync(resolvedPath, 'utf8')
+            );
+            this.findLocalRefFiles(referencedFile, path.dirname(resolvedPath), files);
+          } else {
+            this.error(`Missing local reference: ${value}`);
+          }
+        } else {
+          this.findLocalRefFiles(value, basePath, files);
+        }
+      }
+    } else if (Array.isArray(obj)) {
+      for (const item of obj) {
+        this.findLocalRefFiles(item, basePath, files);
+      }
+    }
+  }
+
+  async updateBundledFile(
+    AsyncAPIFile: string,
+    outputFormat: string,
+    bundledFilePath: string
+  ) {
+    try {
+      const document = await bundle(AsyncAPIFile);
+      const fileContent =
+                outputFormat === '.yaml' || outputFormat === '.yml'
+                  ? document.yml()
+                  : JSON.stringify(document.json());
+      fs.writeFileSync(bundledFilePath, fileContent, { encoding: 'utf-8' });
+    } catch (error: any) {
+      throw new Error(`Error bundling files: ${error.message}`);
+    }
+  }
+
+  async run() {
+    const { args, flags } = await this.parse(StartPreview);
+    const port = flags.port;
+    const filePath = args['spec-file'];
+
+    this.specFile = await load(filePath);
+    this.metricsMetadata.port = port;
+
+    const AsyncAPIFile = this.specFile.getFilePath();
+
+    if (!AsyncAPIFile) {
+      this.error(NO_CONTEXTS_SAVED);
+    }
+
+    const outputFormat = path.extname(AsyncAPIFile);
+    if (!outputFormat) {
+      this.error(
+        'Unable to determine file format from the provided AsyncAPI file.'
+      );
+    }
+
+    const bundledFilePath = `./asyncapi-bundled${outputFormat}`;
+    const basePath = path.dirname(path.resolve(AsyncAPIFile));
+    const filesToWatch = new Set<string>();
+
+    filesToWatch.add(this.specFile.getFilePath()!);
+    const asyncapiDocument = yaml.load(
+      fs.readFileSync(this.specFile.getFilePath()!, 'utf8')
+    );
+    this.findLocalRefFiles(asyncapiDocument, basePath, filesToWatch);
+
+    const watcher = chokidar.watch(Array.from(filesToWatch), {
+      persistent: true,
+    });
+
+    await this.updateBundledFile(
+      AsyncAPIFile,
+      outputFormat,
+      bundledFilePath
+    );
+
+    watcher.on('change', async (changedPath) => {
+      this.log(`File changed: ${changedPath}`);
+      try {
+        await this.updateBundledFile(
+          AsyncAPIFile,
+          outputFormat,
+          bundledFilePath
+        );
+      } catch (error: any) {
+        this.error(`Error updating bundled file: ${error.message}`);
+      }
+    });
+
+    startStudio(bundledFilePath, port);
+  }
+}
+
+export default StartPreview;
diff --git a/src/core/flags/start/preview.flags.ts b/src/core/flags/start/preview.flags.ts
new file mode 100644
index 00000000000..06118c9d95c
--- /dev/null
+++ b/src/core/flags/start/preview.flags.ts
@@ -0,0 +1,8 @@
+import { Flags } from '@oclif/core';
+
+export const previewFlags = () => {
+  return {
+    help: Flags.help({ char: 'h' ,description: 'Show CLI help'}),
+    port: Flags.integer({ char: 'p', description: 'port in which to start Studio' }),
+  };
+};