import Foundation
extension ISO8601DateFormatter {
/// Attempts to parse a date string using common ISO 8601 variants,
/// falling back to local-time parsing when no timezone is present.
/// - Parameters:
/// - dateString: The string representation of the date.
/// - Returns: A `Date` object if parsing is successful with any format, otherwise `nil`.
static func lenientDate(fromISO8601String dateString: String) -> Date? {
let formatter = ISO8601DateFormatter()
let optionsToTry: [ISO8601DateFormatter.Options] = [
// `yyyy-MM-dd'T'HH:mm:ss.SSSZ`, `yyyy-MM-dd'T'HH:mm:ss.SSSZZZZZ`
[.withInternetDateTime, .withFractionalSeconds],
// `yyyy-MM-dd'T'HH:mm:ssZ`, `yyyy-MM-dd'T'HH:mm:ssZZZZZ`
[.withInternetDateTime],
// `yyyy-MM-dd'T'HH:mm:ss.SSS` (no timezone)
[.withFullDate, .withFullTime, .withFractionalSeconds],
// `yyyy-MM-dd'T'HH:mm:ss` (no timezone)
[.withFullDate, .withFullTime],
// `yyyy-MM-dd HH:mm:ss.SSSZZZZZ`
[.withFullDate, .withFullTime, .withSpaceBetweenDateAndTime, .withFractionalSeconds],
// `yyyy-MM-dd HH:mm:ssZZZZZ`
[.withFullDate, .withFullTime, .withSpaceBetweenDateAndTime],
]
for options in optionsToTry {
formatter.formatOptions = options
if let date = formatter.date(from: dateString) {
return date
}
}
// If the string already includes a timezone, don't guess with local-time parsing.
let hasTimeZoneInfo =
dateString.range(
of: #"([Zz]|[+-]\d{2}(:?\d{2})?)$"#,
options: .regularExpression
) != nil
guard !hasTimeZoneInfo else {
return nil
}
// Fall back to local-time parsing for timezone-less inputs.
let fallbackFormats = [
"yyyy-MM-dd'T'HH:mm:ss.SSS",
"yyyy-MM-dd'T'HH:mm:ss",
"yyyy-MM-dd HH:mm:ss.SSS",
"yyyy-MM-dd HH:mm:ss",
"yyyy-MM-dd",
]
let fallbackFormatter = DateFormatter()
fallbackFormatter.locale = Locale(identifier: "en_US_POSIX")
fallbackFormatter.timeZone = TimeZone.current
for format in fallbackFormats {
fallbackFormatter.dateFormat = format
if let date = fallbackFormatter.date(from: dateString) {
return date
}
}
return nil
}
/// Attempts to parse a date string using common ISO 8601 variants,
/// falling back to local-time parsing when no timezone is present.
/// - Parameters:
/// - dateString: The string representation of the date.
/// - Returns: A tuple containing the `Date` object and a boolean indicating if the date is date-only.
static func parsedLenientISO8601Date(
fromISO8601String dateString: String
) -> (date: Date, isDateOnly: Bool)? {
let isDateOnly = isDateOnlyISO8601String(dateString)
guard let date = lenientDate(fromISO8601String: dateString) else {
return nil
}
return (date, isDateOnly)
}
/// Checks if a date string is a date-only ISO 8601 string.
/// - Parameters:
/// - dateString: The string representation of the date.
/// - Returns: A boolean indicating if the date is date-only.
static func isDateOnlyISO8601String(_ dateString: String) -> Bool {
dateString.range(of: #"^\d{4}-\d{2}-\d{2}$"#, options: .regularExpression) != nil
}
}
extension Calendar {
/// Normalizes a start date to ensure it is a date-only date.
/// - Parameters:
/// - date: The date to normalize.
/// - isDateOnly: A boolean indicating if the date is date-only.
/// - Returns: The normalized date.
func normalizedStartDate(from date: Date, isDateOnly: Bool) -> Date {
isDateOnly ? startOfDay(for: date) : date
}
/// Normalizes an end date to ensure it is a date-only date.
/// - Parameters:
/// - date: The date to normalize.
/// - isDateOnly: A boolean indicating if the date is date-only.
/// - Returns: The normalized date.
func normalizedEndDate(from date: Date, isDateOnly: Bool) -> Date {
guard isDateOnly else { return date }
let startOfDay = startOfDay(for: date)
return self.date(byAdding: .day, value: 1, to: startOfDay) ?? startOfDay
}
}
