import { describe, expect, it } from 'vitest'
import { encodePng } from '@/lib/services/swf/nitro-builder'
import { cropRgba, decodePng } from './png-decode'

describe('png-decode', () => {
  it('round-trips an RGBA image through encodePng → decodePng', () => {
    const w = 3
    const h = 2
    const rgba = Buffer.from([
      // row 0
      255, 0, 0, 255, 0, 255, 0, 255, 0, 0, 255, 255,
      // row 1
      10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120,
    ])
    const png = encodePng(w, h, rgba)
    const dec = decodePng(png)
    expect(dec.width).toBe(w)
    expect(dec.height).toBe(h)
    expect(Buffer.compare(dec.rgba, rgba)).toBe(0)
  })

  it('decodes a larger gradient losslessly', () => {
    const w = 16
    const h = 16
    const rgba = Buffer.alloc(w * h * 4)
    for (let i = 0; i < w * h; i++) {
      rgba[i * 4] = i % 256
      rgba[i * 4 + 1] = (i * 3) % 256
      rgba[i * 4 + 2] = (i * 7) % 256
      rgba[i * 4 + 3] = 255
    }
    const dec = decodePng(encodePng(w, h, rgba))
    expect(Buffer.compare(dec.rgba, rgba)).toBe(0)
  })

  it('crops a sub-region', () => {
    // 2x2 sheet, crop the bottom-right 1x1 pixel
    const sheet = Buffer.from([1, 1, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4])
    const cropped = cropRgba(sheet, 2, 1, 1, 1, 1)
    expect([...cropped]).toEqual([4, 4, 4, 4])
  })

  it('rejects non-PNG input', () => {
    expect(() => decodePng(Buffer.from([1, 2, 3, 4, 5, 6, 7, 8]))).toThrow('not a PNG')
  })
})