import EtudeError from "../error/EtudeError";
import Exceptional from "../util/Exceptional";
import MathUtil from "../util/MathUtil";

export default class Degree {
  public static size = 0;
  private static _values: Degree[] = [];

  public static TONIC = new Degree();
  public static SUPERTONIC = new Degree();
  public static MEDIANT = new Degree();
  public static SUBDOMINANT = new Degree();
  public static DOMINANT = new Degree();
  public static SUBMEDIANT = new Degree();
  public static LEADING_TONE = new Degree();

  private constructor() {
    ++Degree.size;
    Degree._values.push(this);
  }

  public static values(startingDegree: Degree = Degree.TONIC): Degree[] {
    let degrees = Degree._values.slice();
    MathUtil.rotate(degrees, startingDegree.getValue() - 1);
    return degrees;
  }

  public ordinal(): number {
    return Degree._values.indexOf(this);
  }

  public static valueOf(degreeString: string): Degree {
    let degree = Degree[degreeString];
    if (degree instanceof Degree) {
      return degree;
    }
    throw EtudeError.forInvalid(Degree, degreeString);
  }

  public static isValid(value: number): boolean {
    return 1 <= value && value <= Degree.size;
  }

  public static fromValue(value: number): Exceptional<Degree> {
    return Exceptional
      .of(value)
      .filter(Degree.isValid, EtudeError.forInvalid(Degree, value, "out of range"))
      .map(i => Degree.values()[i - 1]);
  }

  public getValue(): number {
    return this.ordinal() + 1;
  }

  public toString(): string {
    return Object.keys(Degree).find(d => Degree[d] === this);
  }
}