import { hierarchy } from 'd3-hierarchy'

function flatten (arr, accumulator = []) {
  return arr.reduce((acc, child) => {
    acc.push(child)
    return child.children ? flatten(child.children, acc) : acc
  }, accumulator)
}

function getLinked (text) {
  const types = ['siblings', 'children', 'parents']
  return types.reduce((acc, type) => {
    // Handle `null` and `undefined`
    if (text[type]) {
      text[type].forEach((item, i) => {
        item.linkType = type
      })
      return [...acc, ...text[type]]
    }
    return acc
  }, [])
}

export function toSingleManyData (rawData) {
  rawData.isOrigin = true
  const h = hierarchy(rawData, d => getLinked(d))
  h.each(node => {
    if (node.parent && node.children) {
      const id = node.parent.data.id
      node.children = node.children.filter(child => child.data.id !== id)
    }
  })

  const nodes = h.descendants()
  const links = h.links()
  nodes.forEach(node => {
    Object.assign(node.data, {
      type: node.data.type.toLowerCase()
    })
  })
  return { nodes, links }
}


export function toManyManyData (rawData) {
  rawData.isOrigin = true
  const h = hierarchy(rawData, d => getLinked(d))
  h.each(node => {
    if (node.parent && node.children) {
      const id = node.parent.data.id
      // Remove reference of parent in child's children.
      node.children = node.children.filter(child => child.data.id !== id)
    }
  })

  const links = []
  const nodes = flatten(h.descendants()).reduce((nodes, node) => {
    const sameNode = nodes.find(n => node.data.id === n.data.id)
    if (sameNode) {
      if (!node.children) return nodes
      node.children.forEach(child => {
        if (!sameNode.children.find(c => child.data.id === c.data.id)) {
          sameNode.children.push(child)
        }
      })
    } else {
      if (!node.children) node.children = []
      nodes.push(node)
    }
    return nodes
  }, []).map(({ data, children, depth }) => {
    if (children) {
      children.forEach(child => {
        links.push({ source: data.id, target: child.data.id, linkType: child.data.linkType })
      })
    }
    return {
      id: data.id,
      data: {
        ...data,
        type: data.type.toLowerCase()
      }
    }
  })
  return { nodes, links }
}