/**
 * A simple wavefront OBJ parser.
 *
 * Inspired by
 *    https://webglfundamentals.org/webgl/lessons/webgl-load-obj.html
 *
 * @param {*} handleVert
 * @param {*} handleFace
 *
 * @author Ikaros Kappler
 * @date 2021-04-21
 * @version 0.0.1
 */

type VertHandler = (x: number, y: number, z: number) => void;
type FaceHandler = (a: number, b: number, c: number) => void;

export class OBJParser {
  private handleVert: VertHandler;
  private handleFace: FaceHandler;

  constructor(handleVert: VertHandler, handleFace: FaceHandler) {
    this.handleVert = handleVert;
    this.handleFace = handleFace;
  }

  private _seekEOL(byteView: Int8Array, curPosition: number) {
    // Seek line break character (13)
    while (curPosition < byteView.length && byteView[curPosition] !== 13 && byteView[curPosition] !== 10) {
      curPosition++;
    }
    return curPosition;
  }

  private _handleLine(line: string, lineNo: number) {
    if (line === "" || line.startsWith("#")) {
      return;
    }

    var split = line.split(/\s+/g);
    if (split[0] === "v") {
      // Parse string of form
      // 'v x y z'
      if (split.length < 4) {
        console.warn("Parse error in line " + lineNo + ": too few arguments", line);
        return;
      }
      // Assume all params are proper numbers.
      this.handleVert(Number(split[1]), Number(split[2]), Number(split[3]));
    } else if (split[0] === "f") {
      // Parse string of form
      // 'f vA vB vC' or 'f vA/tA vB/tB vC/tC' or 'f vA/tA/nA vB/tB/nB vC/tC/nC'
      if (split.length < 4) {
        console.warn("Parse error in line " + lineNo + ": too few arguments", line);
        return;
      }
      // Split each face argument into parts (vert-index/texture-coordindate/normal)
      var faceParams = [];
      for (var i = 1; i < 4; i++) {
        var faceSplit = split[i].split("/");
        faceParams.push(Number(faceSplit[0]));
      }
      this.handleFace(faceParams[0], faceParams[1], faceParams[2]);
    }
  }

  parse(arrayBuffer: ArrayBuffer) {
    const byteView: Int8Array = new Int8Array(arrayBuffer);
    var curStart: number = 0;
    var curEnd: number = 0;
    var lineNo: number = 0;
    do {
      curEnd = this._seekEOL(byteView, curStart);
      var lineBuffer = byteView.slice(curStart, curEnd); // .toString();
      var line = String.fromCharCode.apply(null, lineBuffer);
      this._handleLine(line.trim(), lineNo);
      curStart = curEnd + 1;
      lineNo++;
    } while (curEnd < arrayBuffer.byteLength);
  }
}