import { TimeUnit } from "./types.ts";

const SIMPLE_DURATION_RE = /^(-?\d+(?:\.\d+)?)([mhdw])$/i;

export class Duration {
  public readonly value: number;
  public readonly unit: TimeUnit;

  constructor(value: number, unit: TimeUnit) {
    this.value = value;
    this.unit = unit;
  }

  static from(value: number, unit: TimeUnit): Duration {
    return new Duration(value, unit);
  }

  static parseSimple(raw: string | null | undefined): Duration | null {
    if (!raw) {
      return null;
    }

    const match = SIMPLE_DURATION_RE.exec(raw.trim());
    if (!match) {
      return null;
    }

    const valuePart = match[1];
    const unitPart = match[2];
    if (!valuePart || !unitPart) {
      return null;
    }

    const value = Number(valuePart);
    const unit = unitPart.toLowerCase();
    switch (unit) {
      case "m":
        return new Duration(value, TimeUnit.Minutes);
      case "h":
        return new Duration(value, TimeUnit.Hours);
      case "d":
        return new Duration(value, TimeUnit.Days);
      case "w":
        return new Duration(value, TimeUnit.Weeks);
      default:
        return null;
    }
  }

  static fromIso8601(raw: string | null | undefined): Duration | null {
    if (!raw) {
      return null;
    }

    const text = raw.trim();
    const match =
      /^P(?:(\d+(?:\.\d+)?)W)?(?:(\d+(?:\.\d+)?)D)?(?:T(?:(\d+(?:\.\d+)?)H)?(?:(\d+(?:\.\d+)?)M)?(?:(\d+(?:\.\d+)?)S)?)?$/i.exec(
        text,
      );

    if (!match) {
      return null;
    }

    const weeks = Number(match[1] ?? 0);
    const days = Number(match[2] ?? 0);
    const hours = Number(match[3] ?? 0);
    const minutes = Number(match[4] ?? 0);
    const seconds = Number(match[5] ?? 0);

    if (weeks) {
      return new Duration(weeks, TimeUnit.Weeks);
    }
    if (days) {
      return new Duration(days, TimeUnit.Days);
    }
    if (hours) {
      return new Duration(hours, TimeUnit.Hours);
    }
    if (minutes) {
      return new Duration(minutes, TimeUnit.Minutes);
    }
    if (seconds) {
      return new Duration(seconds / 60, TimeUnit.Minutes);
    }
    return new Duration(0, TimeUnit.Minutes);
  }

  toIso8601(): string {
    switch (this.unit) {
      case TimeUnit.Weeks:
        return `P${String(this.value)}W`;
      case TimeUnit.Days:
        return `P${String(this.value)}D`;
      case TimeUnit.Hours:
        return `PT${String(this.value)}H0M0S`;
      case TimeUnit.Minutes:
        return `PT0H${String(this.value)}M0S`;
      case TimeUnit.Months:
        return `P${String(this.value)}M`;
      case TimeUnit.Percent:
        return `PT${String(this.value)}M0S`;
    }
  }

  toSimpleString(): string {
    const value = Number.isInteger(this.value)
      ? this.value.toFixed(1)
      : String(this.value);
    switch (this.unit) {
      case TimeUnit.Minutes:
        return `${value}m`;
      case TimeUnit.Hours:
        return `${value}h`;
      case TimeUnit.Days:
        return `${value}d`;
      case TimeUnit.Weeks:
        return `${value}w`;
      case TimeUnit.Months:
        return `${value}mo`;
      case TimeUnit.Percent:
        return `${value}%`;
    }
  }
}