// Sources/SwiftProtobuf/TimeUtils.swift - Generally useful time/calendar functions

//

// Copyright (c) 2014 - 2017 Apple Inc. and the project authors

// Licensed under Apache License v2.0 with Runtime Library Exception

//

// See LICENSE.txt for license information:

// https://github.com/apple/swift-protobuf/blob/main/LICENSE.txt

//

// -----------------------------------------------------------------------------

///

/// Generally useful time/calendar functions and constants

///

// -----------------------------------------------------------------------------

let minutesPerDay: Int32 = 1440

let minutesPerHour: Int32 = 60

let secondsPerDay: Int32 = 86400

let secondsPerHour: Int32 = 3600

let secondsPerMinute: Int32 = 60

let nanosPerSecond: Int32 = 1_000_000_000

let attosPerNanosecond: Int64 = 1_000_000_000

internal func timeOfDayFromSecondsSince1970(seconds: Int64) -> (hh: Int32, mm: Int32, ss: Int32) {

    let secondsSinceMidnight = Int32(mod(seconds, Int64(secondsPerDay)))

    let ss = mod(secondsSinceMidnight, secondsPerMinute)

    let mm = mod(div(secondsSinceMidnight, secondsPerMinute), minutesPerHour)

    let hh = Int32(div(secondsSinceMidnight, secondsPerHour))

    return (hh: hh, mm: mm, ss: ss)

}

internal func julianDayNumberFromSecondsSince1970(seconds: Int64) -> Int64 {

    // January 1, 1970 is Julian Day Number 2440588.

    // See http://aa.usno.navy.mil/faq/docs/JD_Formula.php

    div(seconds + 2_440_588 * Int64(secondsPerDay), Int64(secondsPerDay))

}

internal func gregorianDateFromSecondsSince1970(seconds: Int64) -> (YY: Int32, MM: Int32, DD: Int32) {

    // The following implements Richards' algorithm (see the Wikipedia article

    // for "Julian day").

    // If you touch this code, please test it exhaustively by playing with

    // Test_Timestamp.testJSON_range.

    let JJ = julianDayNumberFromSecondsSince1970(seconds: seconds)

    let f = JJ + 1401 + div(div(4 * JJ + 274277, 146097) * 3, 4) - 38

    let e = 4 * f + 3

    let g = Int64(div(mod(e, 1461), 4))

    let h = 5 * g + 2

    let DD = div(mod(h, 153), 5) + 1

    let MM = mod(div(h, 153) + 2, 12) + 1

    let YY = div(e, 1461) - 4716 + div(12 + 2 - MM, 12)

    return (YY: Int32(YY), MM: Int32(MM), DD: Int32(DD))

}

internal func nanosToString(nanos: Int32) -> String {

    if nanos == 0 {

        return ""

    } else if nanos % 1_000_000 == 0 {

        return ".\(threeDigit(abs(nanos) / 1_000_000))"

    } else if nanos % 1000 == 0 {

        return ".\(sixDigit(abs(nanos) / 1000))"

    } else {

        return ".\(nineDigit(abs(nanos)))"

    }

}