/*eslint new-cap:0*/
var dtype = require('dtype')

module.exports = flattenVertexData

function flattenVertexData (data, output, offset) {
  if (!data) throw new TypeError('must specify data as first parameter')
  offset = +(offset || 0) | 0

  if (Array.isArray(data) && (data[0] && typeof data[0][0] === 'number')) {
    var dim = data[0].length
    var length = data.length * dim
    var i, j, k, l

    // no output specified, create a new typed array
    if (!output || typeof output === 'string') {
      output = new (dtype(output || 'float32'))(length + offset)
    }

    var dstLength = output.length - offset
    if (length !== dstLength) {
      throw new Error('source length ' + length + ' (' + dim + 'x' + data.length + ')' +
        ' does not match destination length ' + dstLength)
    }

    for (i = 0, k = offset; i < data.length; i++) {
      for (j = 0; j < dim; j++) {
        output[k++] = data[i][j] === null ? NaN : data[i][j]
      }
    }
  } else {
    if (!output || typeof output === 'string') {
      // no output, create a new one
      var Ctor = dtype(output || 'float32')

      // handle arrays separately due to possible nulls
      if (Array.isArray(data) || output === 'array') {
        output = new Ctor(data.length + offset)
        for (i = 0, k = offset, l = output.length; k < l; k++, i++) {
          output[k] = data[i] === null ? NaN : data[i]
        }
      } else {
        if (offset === 0) {
          output = new Ctor(data)
        } else {
          output = new Ctor(data.length + offset)

          output.set(data, offset)
        }
      }
    } else {
      // store output in existing array
      output.set(data, offset)
    }
  }

  return output
}