import { Budget } from "./budget";
import Currency from "./currency/currency";

class BalanceToBudgetRatio {
  toString(): string {
    return this._ratio?.toFixed(2) ?? "";
  }

  public readonly recommendedAction: "arrears" | "save" | "spend" | null;
  public readonly normalisedRatio: number | null;

  private constructor(
    private readonly _ratio: number | null,
    private readonly _normalisationFactor: number,
  ) {
    if (this._ratio === null) {
      this.normalisedRatio = null;
      this.recommendedAction = null;
      return;
    }

    this.normalisedRatio = this._ratio * this._normalisationFactor;

    if (this._ratio < 0) {
      this.recommendedAction = "arrears";
    } else if (this._ratio >= 1) {
      this.recommendedAction = "spend";
    } else {
      this.recommendedAction = "save";
    }
  }

  static new(balance: Currency, budget: Budget | null) {
    if (budget === null || budget.quantity === 0 || budget.quantity === -0) {
      return null;
    }

    return new BalanceToBudgetRatio(
      balance.valueOf() / budget.quantity.valueOf(),
      1,
    );
  }

  static makeNormaliser(
    ...balanceToBudgetRatios: (BalanceToBudgetRatio | null)[]
  ): (r: BalanceToBudgetRatio | null) => BalanceToBudgetRatio {
    const validRatios = balanceToBudgetRatios.filter(
      (r) =>
        r &&
        r._ratio &&
        !isNaN(r._ratio) &&
        Infinity > r._ratio &&
        -Infinity < r._ratio,
    );

    const maxAbsRatio = Math.max(
      ...validRatios.map((r) => Math.abs(r?._ratio ?? 0)),
    );

    const normalisationFactor = 1 / maxAbsRatio;
    return (r) =>
      new BalanceToBudgetRatio(r?._ratio ?? null, normalisationFactor);
  }

  static compare(
    lhs: BalanceToBudgetRatio | null,
    rhs: BalanceToBudgetRatio | null,
  ): number {
    if (lhs === null || lhs._ratio === null) {
      if (rhs === null || rhs._ratio === null) {
        return 0;
      }
      return 1;
    }
    if (rhs === null || rhs._ratio === null) {
      return -1;
    }

    return rhs._ratio - lhs._ratio;
  }
}

export { BalanceToBudgetRatio };