const separateTree = require('./separate-root');
const VALID_DIRECTIONS = [
  'LR', // left to right
  'RL', // right to left
  'TB', // top to bottom
  'BT', // bottom to top
  'H', // horizontal
  'V' // vertical
];
const HORIZONTAL_DIRECTIONS = [
  'LR',
  'RL',
  'H'
];
const isHorizontal = direction => HORIZONTAL_DIRECTIONS.indexOf(direction) > -1;
const DEFAULT_DIRECTION = VALID_DIRECTIONS[0];

module.exports = (root, options, layoutAlgrithm) => {
  const direction = options.direction || DEFAULT_DIRECTION;
  options.isHorizontal = isHorizontal(direction);
  if (direction && VALID_DIRECTIONS.indexOf(direction) === -1) {
    throw new TypeError(`Invalid direction: ${direction}`);
  }

  if (direction === VALID_DIRECTIONS[0]) {
    // LR
    layoutAlgrithm(root, options);
  } else if (direction === VALID_DIRECTIONS[1]) {
    // RL
    layoutAlgrithm(root, options);
    root.right2left();
  } else if (direction === VALID_DIRECTIONS[2]) {
    // TB
    layoutAlgrithm(root, options);
  } else if (direction === VALID_DIRECTIONS[3]) {
    // BT
    layoutAlgrithm(root, options);
    root.bottom2top();
  } else if (direction === VALID_DIRECTIONS[4] || direction === VALID_DIRECTIONS[5]) {
    // H or V
    // separate into left and right trees
    const { left, right } = separateTree(root, options);
    // do layout for left and right trees
    layoutAlgrithm(left, options);
    layoutAlgrithm(right, options);
    options.isHorizontal ? (left.right2left()) : (left.bottom2top());
    // combine left and right trees
    right.translate(left.x - right.x, left.y - right.y);
    // translate root
    root.x = left.x;
    root.y = right.y;
    const bb = root.getBoundingBox();
    if (options.isHorizontal) {
      if (bb.top < 0) {
        root.translate(0, -bb.top);
      }
    } else {
      if (bb.left < 0) {
        root.translate(-bb.left, 0);
      }
    }
  }
  root.translate(-(root.x + root.width / 2 + root.hgap), -(root.y + root.height / 2 + root.vgap));
  return root;
};