import { Lut, RGBTuple } from '../typings'

const defaultDomainMin: RGBTuple = [0, 0, 0]
const defaultDomainMax: RGBTuple = [1, 1, 1]

const parseTuple = (...rest: string[]) => {
  const rgbTuple = rest.map(Number)
  if (rgbTuple.length !== 3) throw new Error(`RGB tuple has ${rgbTuple.length}`)
  return rgbTuple as RGBTuple
}

export const parseCubeLut = (data: Uint8Array): Lut => {
  const lines = new TextDecoder().decode(data).split('\n')
  const lut: Partial<Lut> & { domain: Lut['domain']; data: Lut['data'] } = {
    domain: {
      min: defaultDomainMin,
      max: defaultDomainMax
    },
    data: []
  }
  for (let i = 0; i < lines.length; i++) {
    try {
      const line = lines[i]
      // Skip comments and empty lines
      if (line[0] === '#' || line === '') continue

      const [identifier, ...rest] = line.split(' ')
      switch (identifier) {
        case 'TITLE':
          lut.title = line.slice(7, -1)
          break
        case 'LUT_3D_SIZE' || 'LUT_1D_SIZE':
          lut.type = identifier === 'LUT_3D_SIZE' ? '3d' : '1d'
          if (!rest[0]) throw new Error('Lut file does not specify size')
          lut.size = Number(rest[0])
          break
        case 'DOMAIN_MIN':
          lut.domain.min = parseTuple(...rest)
          break
        case 'DOMAIN_MAX':
          lut.domain.max = parseTuple(...rest)
          break
        default:
          // We have data, parse it
          lut.data.push(parseTuple(identifier, ...rest))
          break
      }
    } catch (err) {
      throw new Error(`failed parsing cube lut at line ${i}: ${err}`)
    }
  }

  if (!lut.type) throw new Error('Lut file missing dimension')
  if (lut.data.length === 0) throw new Error('Lut has no data')
  return lut as Lut
}