feat: initial Transmute app — universal client-side file converter

Full-stack client-side file converter with Next.js 15 static export.
Supports images (Canvas API), documents (mammoth/pdf-lib/jspdf),
audio/video (ffmpeg.wasm), and data formats (papaparse/yaml/xml).
Dark industrial UI with Space Grotesk + JetBrains Mono, animated
drop zone, glassmorphism file cards, progress rings, and ZIP downloads.
Zero server dependencies — files never leave the browser.

src/lib/converters/dataConverter.ts

@@ -0,0 +1,114 @@
+import Papa from 'papaparse';
+import yaml from 'js-yaml';
+import { XMLParser, XMLBuilder } from 'fast-xml-parser';
+import { ConversionResult } from '@/types';
+import { buildOutputFilename, getMimeType } from '@/lib/utils';
+import { getExtension } from '@/lib/fileDetector';
+
+async function readFileAsText(file: File): Promise<string> {
+  return new Promise((resolve, reject) => {
+    const reader = new FileReader();
+    reader.onload = (e) => resolve(e.target?.result as string);
+    reader.onerror = () => reject(new Error('Failed to read file'));
+    reader.readAsText(file);
+  });
+}
+
+function csvToJson(text: string): object[] {
+  const result = Papa.parse(text, { header: true, skipEmptyLines: true });
+  return result.data as object[];
+}
+
+function jsonToCsv(data: unknown): string {
+  const arr = Array.isArray(data) ? data : [data];
+  return Papa.unparse(arr);
+}
+
+function tsvToJson(text: string): object[] {
+  const result = Papa.parse(text, { header: true, skipEmptyLines: true, delimiter: '\t' });
+  return result.data as object[];
+}
+
+function jsonToTsv(data: unknown): string {
+  const arr = Array.isArray(data) ? data : [data];
+  return Papa.unparse(arr, { delimiter: '\t' });
+}
+
+function xmlToJson(text: string): unknown {
+  const parser = new XMLParser({ ignoreAttributes: false });
+  return parser.parse(text);
+}
+
+function jsonToXml(data: unknown): string {
+  const builder = new XMLBuilder({ ignoreAttributes: false, format: true });
+  return builder.build(typeof data === 'string' ? JSON.parse(data) : data);
+}
+
+function jsonToYaml(data: unknown): string {
+  return yaml.dump(typeof data === 'string' ? JSON.parse(data) : data);
+}
+
+function yamlToJson(text: string): unknown {
+  return yaml.load(text);
+}
+
+async function toIntermediate(file: File, ext: string): Promise<unknown> {
+  const text = await readFileAsText(file);
+
+  switch (ext) {
+    case 'json':
+      return JSON.parse(text);
+    case 'csv':
+      return csvToJson(text);
+    case 'tsv':
+      return tsvToJson(text);
+    case 'xml':
+      return xmlToJson(text);
+    case 'yaml':
+    case 'yml':
+      return yamlToJson(text);
+    default:
+      throw new Error(`Unsupported source format: ${ext}`);
+  }
+}
+
+function fromIntermediate(data: unknown, targetFormat: string): string {
+  switch (targetFormat) {
+    case 'json':
+      return JSON.stringify(data, null, 2);
+    case 'csv':
+      return jsonToCsv(data);
+    case 'tsv':
+      return jsonToTsv(data);
+    case 'xml':
+      return jsonToXml(data);
+    case 'yaml':
+    case 'yml':
+      return jsonToYaml(data);
+    default:
+      throw new Error(`Unsupported target format: ${targetFormat}`);
+  }
+}
+
+export async function convertData(
+  file: File,
+  targetFormat: string,
+  onProgress?: (progress: number) => void
+): Promise<ConversionResult> {
+  onProgress?.(20);
+
+  const ext = getExtension(file.name);
+  const intermediate = await toIntermediate(file, ext);
+  onProgress?.(60);
+
+  const output = fromIntermediate(intermediate, targetFormat);
+  onProgress?.(90);
+
+  const blob = new Blob([output], { type: getMimeType(targetFormat) });
+  onProgress?.(100);
+
+  return {
+    blob,
+    filename: buildOutputFilename(file.name, targetFormat),
+  };
+}