subRipTimingLine

subrip_timing_line.swift

func subRipTimingLine(start: TimeInterval, duration: TimeInterval) -> String {
	"\(timeIntervalToSubRipFormattedTimestamp(start)) --> \(timeIntervalToSubRipFormattedTimestamp(start + duration))"
}

private let subRipTimeIntervalFormatter: DateComponentsFormatter = {
	let formatter = DateComponentsFormatter()
	formatter.zeroFormattingBehavior = .pad
	formatter.allowedUnits = [.hour, .minute, .second] // (1)
	return formatter
}()

func timeIntervalToSubRipFormattedTimestamp(_ time: TimeInterval) -> String {
	let millisecondsDigits = 3

	let milliseconds = "\(Int((time.truncatingRemainder(dividingBy: 1) * 1_000).rounded()))" // (2)
		.prefix(millisecondsDigits)

	let millisecondsZeroPadding = Array(
		repeating: "0",
		count: millisecondsDigits - milliseconds.count
	)
	.joined()

	return subRipTimeIntervalFormatter.string(from: time)! +
		",\(millisecondsZeroPadding + milliseconds)"
}