substance/model/_compareCoordinates.js

Substance is a JavaScript library for web-based content editing. It provides building blocks for realizing custom text editors and web-based publishing system. It is developed to power our online editing platform [Substance](http://substance.io).

export default function compareCoordinates (doc, containerPath, coor1, coor2) {
  // First compare coordinates via their xpath if they have differing paths
  if (!coor1.hasSamePath(coor2)) {
    const address1 = _getContainerAddress(doc, containerPath, coor1)
    const address2 = _getContainerAddress(doc, containerPath, coor2)
    const L = Math.min(address1.length, address2.length)
    for (let level = 0; level < L; level++) {
      const p1 = address1[level]
      const p2 = address2[level]
      if (p1 < p2) return -1
      if (p1 > p2) return 1
    }
    if (address1.length === address2.length) {
      return Math.sign(coor1.offset - coor2.offset)
    } else {
      // TODO: how should we compare these?
      console.error('FIXME: unexpected case in compareCoordinates()')
      return 0
    }
  } else {
    return Math.sign(coor1.offset - coor2.offset)
  }
}

function _getContainerAddress (doc, containerPath, coor) {
  const containerId = containerPath[0]
  const nodeId = coor.path[0]
  const node = doc.get(nodeId)
  let xpath = node.getXpath()
  const address = []
  while (xpath) {
    if (xpath.id === containerId) return address
    address.unshift(xpath.pos || 0)
    xpath = xpath.prev
  }
}