; SPDX-License-Identifier: MIT


Import "DateMath.rgr"

; Parse and validate ISO date strings without host locale APIs.
class IsoDateParse {

  sfn isDigit:boolean (ch:int) {
    return (ch >= 48 && ch <= 57)
  }

  sfn toIsoDateOnly:string (value:string) {
    if ((strlen value) < 10) {
      return ""
    }
    def candidate:string (substring value 0 10)
    if ((charAt candidate 4) != 45) {
      return ""
    }
    if ((charAt candidate 7) != 45) {
      return ""
    }
    def i:int 0
    while (i < 10) {
      if (i == 4 || i == 7) {
        i = i + 1
        continue
      }
      if ((IsoDateParse.isDigit((charAt candidate i))) == false) {
        return ""
      }
      i = i + 1
    }
    return candidate
  }

  sfn datePartsToISO:string (year:int month:int day:int) {
    if (year <= 0 || month <= 0 || day <= 0) {
      return ""
    }
    return (DateMath.formatIso(year month day))
  }

  sfn isoDateToYear:int (iso:string) {
    def p:DateParts (DateParts.fromIso(iso))
    return p.year
  }

  sfn isoDateToMonth:int (iso:string) {
    def p:DateParts (DateParts.fromIso(iso))
    return p.month
  }

  sfn isoDateToDay:int (iso:string) {
    def p:DateParts (DateParts.fromIso(iso))
    return p.day
  }
}