import { LinkedField, LinkedType } from './linkTypeMap'
import { startsWith } from 'lodash'

export const getFieldFromPath = (root: LinkedType | undefined, path: string[]) => {
  let current: LinkedField | undefined

  if (!root) throw new Error('root type is not provided')

  if (path.length === 0) throw new Error(`path is empty`)

  path.forEach(f => {
    const type = current ? current.type : root

    if (!type.fields) throw new Error(`type \`${type.name}\` does not have fields`)

    const possibleTypes = Object.keys(type.fields)
      .filter(i => startsWith(i, 'on_'))
      .reduce(
        (types, fieldName) => {
          const field = type.fields && type.fields[fieldName]
          if (field) types.push(field.type)
          return types
        },
        [type],
      )

    let field: LinkedField | null = null

    possibleTypes.forEach(type => {
      const found = type.fields && type.fields[f]
      if (found) field = found
    })

    if (!field) throw new Error(`type \`${type.name}\` does not have a field \`${f}\``)

    current = field
  })

  return <LinkedField>current
}