// A search utility for arbitrary (new) tileUpdates.
// Provides `add` functionality, which auto-checks adjacency with other blocks. Subsequently, it searches them
// Provides `del` functionality, which should be used with auto-deletion

const bs = require('binary-search');
const Space = require('../space');
const comb = require('../utils/comb')
const getdims = require('../utils/getdims');
const vec = require('../utils/vec');

function getComp(index){
  return (element,needle) => (element[index] - needle[index] || element[1-index] - needle[1-index])
}

function tileToChar(coord){
  let cofactor = [8,16];
  return [coord[0]*cofactor[0], coord[1]*cofactor[1]];
}

function Search(searchBlock){ // searchBlock should be a Space object.
  this.tiles = {};     // Object which stores Spaces.
  this.sort = [[],[]]; // Vertically/horizontally sorted list of tiles for fast addition, deletion, and searching

  this.add = function(loc, space){ // loc should be [tileY,tileX] and space Space.
    this.tiles[loc] = space;
    this.tiles[loc].loc = vec.tileToChar(loc);
    let inds = Array(2); // Records horizontal and vertical indices for insertion. Then actually inserts the item.
    [0,1].forEach( ind => { // ind chooses y-or-x
      inds[ind] = -bs(this.sort[ind], loc, getComp(ind))-1;
      if (inds[ind] < 0) throw "loc should not be a part of the list";
      this.sort[ind].splice(inds[ind], 0, loc);
    });
    let block = this.block(loc, inds);
    let searchspace = new Space();
    block.forEach( (tile) => {
      searchspace.comb( this.tiles[tile], comb.add );
    });
    coords = searchspace.search(searchBlock); // According to space docs, [] on failure and a character location on success
    return vec.add(coords, searchspace.loc);
  }
  
  this.block = function(loc,inds,exclude){
    if (! exclude) exclude = new Set(); // If not given, replace.
    let adjacent = new Set([loc]);
    exclude.add(loc);
    [0,1].forEach( ind => {
      // inds[ind] is address, so check neighbors on sort[ind] (up, then down)
      // until sort[ind][inds[ind]][ind] != sort[ind][otherind][ind].
      // on each, if sort[ind][otherind][1-ind] == sort[ind][inds[ind]][1-ind],
      // add to adjacent and search it with exclude=adjacent. Add that to adjacent
      let sort = this.sort[ind];
      let chkind = inds[ind];
      [-1, 1].forEach( sgn => {
        let curind = chkind + sgn;
        while (sort[curind] && sort[chkind][ind] == sort[curind][ind]){
          if (! exclude.has(sort[curind])){
            adjacent.add(...this.block(sort[curind], [curind, bs(sort, sort[curind], getComp(1-ind))], adjacent));
          }
          curind += sgn;
        }
      });
    });
    return adjacent;
  }

  this.del = function(loc){
    delete this.tiles[loc];
    [0, 1].forEach( ind => {
      let theind = bs(this.sort[ind], loc, getComp(ind));
      if (theind < 0) throw "loc must already be a part of the list";
      this.sort[ind].splice(bs(this.sort[ind], loc, getComp(ind)), 1);
    })
  }

  this.has = function(loc){
    if (bs(this.sort[0], loc, getComp(0)) < 0) return false; // Could use ind = 1 just as well, but doesn't really matter
    // bs returns negative if not found.
    else return true;
  }
}

module.exports = Search;