// The render script's only pure logic: the IHDR sanity check that catches
// Chrome's occasional blank- or partial-render misfires.
import { describe, expect, it } from 'vitest'

// @ts-expect-error plain-node script, no type declarations
import { pngSize } from '../../scripts/render-icons.mjs'

function fakePng(width: number, height: number): Uint8Array {
  const bytes = new Uint8Array(24)
  bytes.set([0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a])
  const dv = new DataView(bytes.buffer)
  dv.setUint32(16, width)
  dv.setUint32(20, height)
  return bytes
}

describe('pngSize', () => {
  it('reads IHDR dimensions', () => {
    expect(pngSize(fakePng(128, 128))).toEqual({ width: 128, height: 128 })
    expect(pngSize(fakePng(16, 32))).toEqual({ width: 16, height: 32 })
  })

  it('rejects non-PNG bytes', () => {
    expect(() => pngSize(new TextEncoder().encode('<svg xmlns="..."/>'))).toThrow('not a PNG')
    expect(() => pngSize(new Uint8Array(0))).toThrow('not a PNG')
  })
})