Initial scaffold: spec, architecture playbook, and M0 skeleton

src/core/format-detection.test.ts

@@ -0,0 +1,53 @@
+import { describe, it, expect } from 'vitest';
+import { detectFormat, detectFormatFromUrl } from './format-detection';
+
+describe('detectFormat', () => {
+  it('detects a JSON array of objects with high confidence', () => {
+    expect(detectFormat('[{"a":1},{"a":2}]')).toEqual({ format: 'json', confidence: 'high' });
+  });
+
+  it('detects a single JSON object as json', () => {
+    expect(detectFormat('{"a":1}')).toEqual({ format: 'json', confidence: 'high' });
+  });
+
+  it('detects a TopoJSON topology object', () => {
+    const topo = JSON.stringify({ type: 'Topology', objects: {}, arcs: [] });
+    expect(detectFormat(topo)).toEqual({ format: 'topojson', confidence: 'high' });
+  });
+
+  it('detects CSV from a comma-separated header + row with medium confidence', () => {
+    expect(detectFormat('a,b,c\n1,2,3')).toEqual({ format: 'csv', confidence: 'medium' });
+  });
+
+  it('detects TSV from a tab-separated header + row with medium confidence', () => {
+    expect(detectFormat('a\tb\tc\n1\t2\t3')).toEqual({ format: 'tsv', confidence: 'medium' });
+  });
+
+  it('prefers TSV over CSV when both delimiters appear in the header', () => {
+    expect(detectFormat('a\tb,c\n1\t2,3').format).toBe('tsv');
+  });
+
+  it('returns low confidence / null for unrecognized input', () => {
+    expect(detectFormat('just a sentence')).toEqual({ format: null, confidence: 'low' });
+  });
+
+  it('returns low confidence / null for empty input', () => {
+    expect(detectFormat('   ')).toEqual({ format: null, confidence: 'low' });
+  });
+});
+
+describe('detectFormatFromUrl', () => {
+  it.each([
+    ['https://example.com/data.csv', 'csv'],
+    ['https://example.com/data.tsv', 'tsv'],
+    ['https://example.com/data.json', 'json'],
+    ['https://example.com/world.topojson', 'topojson'],
+    ['https://example.com/data.csv?v=2', 'csv'],
+  ])('infers format from %s', (url, expected) => {
+    expect(detectFormatFromUrl(url)).toBe(expected);
+  });
+
+  it('returns null when no known extension is present', () => {
+    expect(detectFormatFromUrl('https://example.com/data')).toBeNull();
+  });
+});