import { startOfYear, endOfYear, startOfMonth, endOfMonth, addYears } from 'date-fns'

const MONTHS: Record<string, number> = {
  JAN: 0, FEB: 1, MAR: 2, APR: 3, MAY: 4, JUN: 5,
  JUL: 6, AUG: 7, SEP: 8, OCT: 9, NOV: 10, DEC: 11,
}

export function parseDateRangeFromTitle(
  title: string,
  referenceYear: number = new Date().getFullYear()
): { start: Date; end: Date } | null {
  const match = title.match(/^\[([^\]]+)\]/)
  if (!match) return null

  const tag = match[1].toUpperCase()
  const baseDate = new Date(referenceYear, 0, 1)

  const yearMatch = tag.match(/^(\d+)YR$/)
  if (yearMatch) {
    const years = parseInt(yearMatch[1])
    return { start: startOfYear(baseDate), end: endOfYear(addYears(baseDate, years - 1)) }
  }

  if (tag === 'H1') return { start: new Date(referenceYear, 0, 1), end: new Date(referenceYear, 5, 30) }
  if (tag === 'H2') return { start: new Date(referenceYear, 6, 1), end: new Date(referenceYear, 11, 31) }

  const quarterMatch = tag.match(/^Q([1-4])$/)
  if (quarterMatch) {
    const q = parseInt(quarterMatch[1])
    const startMonth = (q - 1) * 3
    return { start: new Date(referenceYear, startMonth, 1), end: endOfMonth(new Date(referenceYear, startMonth + 2, 1)) }
  }

  if (tag in MONTHS) {
    const month = MONTHS[tag]
    return { start: startOfMonth(new Date(referenceYear, month, 1)), end: endOfMonth(new Date(referenceYear, month, 1)) }
  }

  const weekMatch = tag.match(/^W(\d+)$/)
  if (weekMatch) {
    const week = parseInt(weekMatch[1])
    const start = new Date(referenceYear, 0, 1 + (week - 1) * 7)
    const end = new Date(start)
    end.setDate(end.getDate() + 6)
    return { start, end }
  }

  return null
}

export function getHierarchyLevel(title: string): number {
  const match = title.match(/^\[([^\]]+)\]/)
  if (!match) return 0
  const tag = match[1].toUpperCase()
  if (/^\d+YR$/.test(tag)) return 100 + parseInt(tag)
  if (/^H[12]$/.test(tag)) return 50
  if (/^Q[1-4]$/.test(tag)) return 40
  if (tag in MONTHS) return 30
  if (/^W\d+$/.test(tag)) return 20
  return 10
}