import { DomainError } from '@/shared/exceptions'

export class Month {
  constructor(public readonly value: string) {
    if (!/^\d{4}-\d{2}$/.test(value)) {
      throw new DomainError('月份格式错误，应为YYYY-MM')
    }
  }

  static current(): Month {
    const now = new Date()
    const year = now.getFullYear()
    const month = String(now.getMonth() + 1).padStart(2, '0')
    return new Month(`${year}-${month}`)
  }

  static create(value: string): Month {
    return new Month(value)
  }

  static fromDate(date: Date): Month {
    const year = date.getFullYear()
    const month = String(date.getMonth() + 1).padStart(2, '0')
    return new Month(`${year}-${month}`)
  }

  next(): Month {
    const [year, month] = this.value.split('-').map(Number)
    const nextMonth = month === 12 ? 1 : month + 1
    const nextYear = month === 12 ? year + 1 : year
    return new Month(`${nextYear}-${String(nextMonth).padStart(2, '0')}`)
  }

  previous(): Month {
    const [year, month] = this.value.split('-').map(Number)
    const prevMonth = month === 1 ? 12 : month - 1
    const prevYear = month === 1 ? year - 1 : year
    return new Month(`${prevYear}-${String(prevMonth).padStart(2, '0')}`)
  }

  equals(other: Month): boolean {
    return this.value === other.value
  }

  isAfter(other: Month): boolean {
    return this.value > other.value
  }

  isBefore(other: Month): boolean {
    return this.value < other.value
  }

  toString(): string {
    return this.value
  }

  getYear(): number {
    return parseInt(this.value.split('-')[0])
  }

  getMonth(): number {
    return parseInt(this.value.split('-')[1])
  }
}