import * as visuals from "./visuals.js";

function get_json(url) {
  var request = new XMLHttpRequest();
  request.open("get", url, false);
  request.send(null);
  return JSON.parse(request.responseText);
}

class Backend {
  constructor() {
    this.config = this.getConfig();
  }
  getConfig() {
    return new Configuration(
      get_json("http://localhost:3000/get_state/").map((p) => {
        let piece = new Piece();
        Object.assign(piece, p);
        return piece;
      })
    );
  }
  makeMove(move) {
    this.config = this.config.makeMove(move);
    return this.config.clone();
  }
  getAvailableMoves(position) {
    return [];
  }
}

class Chess {
  constructor() {
    this.backend = new Backend();
    this.configVis = null;
    this.canvas = new visuals.Canvas();
    this.moveSource = null;
    this.canMoveTo = [];
    this.syncBackend();
    document.onclick = (ev) => this.click(ev);
  }
  syncBackend() {
    let config = this.backend.getConfig();
    if (this.configVis !== null) {
      this.configVis.undraw();
    }
    this.configVis = new visuals.ConfigVis(config.pieces);
    this.configVis.draw(this.canvas);
  }
  showAvailableMoves(canMoveTo) {}
  click(ev) {
    if (this.moveSource === null) {
      this._firstClick(ev);
    } else {
      this._secondClick(ev);
    }
  }
  _firstClick(ev) {
    let rcA = this.canvas.screenCoordsToRowCol(ev.clientX, ev.clientY);
    if (rcA === null) return;
    let positionA = visuals.rowColToBoardIndex(...rcA);
    this.showAvailableMoves(this.backend.getAvailableMoves(positionA));
    this.moveSource = positionA;
  }
  _secondClick(ev) {
    let rcB = this.canvas.screenCoordsToRowCol(ev.clientX, ev.clientY);
    if (rcB !== null) {
      let move = {
        from: this.moveSource,
        to: visuals.rowColToBoardIndex(...rcB),
      };
      this.backend.makeMove(move);
      this.syncBackend();
    }
    this.moveSource = null;
  }
}

class Move {
  constructor(kind, from, to) {
    this.kind = kind;
    this.from = from;
    this.to = to;
  }
}

class Piece {
  constructor(who, color, position) {
    this.who = who;
    this.color = color;
    this.position = position;
  }
  clone() {
    return new Piece(this.who, this.color, this.position);
  }
  moveTo(position) {
    return new Piece(this.who, this.color, position);
  }
}

class Configuration {
  constructor(pieces) {
    this.pieces = pieces;
  }
  clone() {
    let pieces = [];
    for (let piece of this.pieces) {
      pieces.push(piece.clone());
    }
    return new Configuration(pieces);
  }
  getAt(position) {
    return this.pieces.find((piece) => piece.position === position) || null;
  }
  dropAt(position) {
    return new Configuration(
      this.pieces.filter((piece) => piece.position !== position)
    );
  }
  makeMove(move) {
    const pieceToMove = this.getAt(move.from);
    if (pieceToMove === null) return this;
    else
      return new Configuration([
        ...this.dropAt(move.from).dropAt(move.to).pieces,
        pieceToMove.moveTo(move.to),
      ]);
  }
}

new Chess();