import { EastFunction, TimeUnit } from '../functions';
import { DateTimeType, FloatType, IntegerType, NullType, Nullable, StringType } from '../types';
import { Expression } from './core';
/**
 * Construct a datetime value from a string, with optional format.
 *
 * @param value the string {@link Expression} to parse
 * @param format the format string (by default it expects ISO-8601, e.g. 'YYYY-MM-DDThh:mm:ss.sssZ')
 *
 * @category Expression
 *
 * @example
 * ```typescript
 *  // ...
 *  // parse the date from the US-formated date string
 *  Date: ToDateTime('DateString', 'M-D-YYYY'),
 *  // ...
 * ```
 */
export declare function ToDateTime(value: EastFunction<StringType>, format?: string): EastFunction<Nullable<DateTimeType>>;
/**
 * Find the duration between datetimes `start` and `stop`, in the given time `unit`. Note:
 * returns a negative number if `stop` is prior to `start` (and that the ordering of
 * arguments is reversed compared to {@link Subtract}).
 *
 * @param start the {@link Expression} for the initial datetime
 * @param stop the {@link Expression} for the final datetime
 * @param unit the {@link TimeUnit} to calculate the answer in ('millisecond', 'second', 'minute', 'hour', 'day' or 'week')
 *
 * @category Expression
 *
 * @example
 * ```typescript
 *  // ...
 *  // return the length of a shift in hours
 *  ShiftHours: Duration(
 *      Variable('ShiftStart', DateTimeType),
 *      Variable('ShiftStop', DateTimeType),
 *      'hour'
 *  ),
 *  // ...
 * ```
 */
export declare function Duration<T extends DateTimeType, U extends DateTimeType>(start: EastFunction<T>, stop: EastFunction<U>, unit: TimeUnit): EastFunction<T extends NullType ? Nullable<FloatType> : U extends NullType ? Nullable<FloatType> : FloatType>;
/**
 * Add the `duration` (in the given time `unit`) to `datetime`.
 *
 * @category Expression
 *
 * @param datetime the {@link Expression} for the initial datetime
 * @param duration the {@link Expression} for duration
 * @param unit the {@link TimeUnit} of `duration` ('millisecond', 'second', 'minute', 'hour', 'day' or 'week')
 *
 * @example
 * ```typescript
 *  // ...
 *  // return the date payment is due for an invoice according to the invoice terms
 *  DueDate: AddDuration(
 *      Variable('PurchaseDate', DateTimeType),
 *      Variable('InvoiceTermDays', FloatType),
 *      'day'
 *  ),
 *  // ...
 * ```
 */
export declare function AddDuration<T extends DateTimeType, U extends FloatType>(datetime: EastFunction<T>, duration: Expression<U>, unit: TimeUnit): EastFunction<T extends NullType ? Nullable<DateTimeType> : U extends NullType ? Nullable<DateTimeType> : DateTimeType>;
export declare function AddDuration<T extends DateTimeType, U extends IntegerType>(datetime: EastFunction<T>, duration: Expression<U>, unit: TimeUnit): EastFunction<T extends NullType ? Nullable<DateTimeType> : U extends NullType ? Nullable<DateTimeType> : DateTimeType>;
/**
 * Subtract the `duration` (in the given time `unit`) from `datetime`.
 *
 * @category Expression
 *
 * @param datetime the {@link Expression} for the initial datetime
 * @param duration the {@link Expression} for duration
 * @param unit the {@link TimeUnit} of `duration` ('millisecond', 'second', 'minute', 'hour', 'day' or 'week')
 *
 * @example
 * ```typescript
 *  // ...
 *  // return the date payment is due for an invoice according to the invoice terms
 *  DueDate: SubtractDuration(
 *      Variable('PurchaseDate', DateTimeType),
 *      Variable('InvoiceTermDays', FloatType),
 *      'day'
 *  ),
 *  // ...
 * ```
 */
export declare function SubtractDuration<T extends DateTimeType, U extends FloatType>(datetime: EastFunction<T>, duration: Expression<U>, unit: TimeUnit): EastFunction<T extends NullType ? Nullable<DateTimeType> : U extends NullType ? Nullable<DateTimeType> : DateTimeType>;
export declare function SubtractDuration<T extends DateTimeType, U extends IntegerType>(datetime: EastFunction<T>, duration: Expression<U>, unit: TimeUnit): EastFunction<T extends NullType ? Nullable<DateTimeType> : U extends NullType ? Nullable<DateTimeType> : DateTimeType>;
/**
 * Convert the `datetime` from `input_timezone` to `output_timezone`.
 *
 * Note: all datetimes in East are plain (or "naive") datetimes and conversion should take
 * place using this function. Absolute durations should be calculated in UTC
 * (zone 'Etc/UTC') to account for e.g. day-light-saving changeovers. The list of IANA
 * timezone strings can be found at https://en.wikipedia.org/wiki/List_of_tz_database_time_zones.
 *
 * @param datetime the {@link Expression} for the input datetime
 * @param input_timezone the {@link Expression} for the input's timezone (as an IANA timezone string)
 * @param output_timezone the {@link Expression} for the output's timezone (as an IANA timezone string)
 *
 * @category Expression
 *
 * @example
 * ```typescript
 *  // ...
 *  // convert the UTC time into Sydney, Australia time
 *  LocalTime: ConvertTimeZone(
 *      Variable('UtcTime', DateTimeType),
 *      'Etc/UTC',
 *      'Australia/Sydney'
 *  ),
 *  // ...
 * ```
 */
export declare function TimeZoneConvert<T extends DateTimeType>(datetime: EastFunction<T>, input_timezone: EastFunction<StringType & {
    nullable?: never;
}> | string, output_timezone: EastFunction<StringType & {
    nullable?: never;
}> | string): EastFunction<T>;
/**
 * Return the number of whole milliseconds elapsed since the start of the second (0 - 999).
 *
 * @param datetime the {@link Expression} for datetime
 *
 * @category Expression
 */
export declare function Millisecond<T extends DateTimeType>(datetime: EastFunction<T>): EastFunction<T extends NullType ? Nullable<IntegerType> : IntegerType>;
/**
 * Return the number of whole seconds elapsed since the start of the minute (0 - 59).
 *
 * @param datetime the {@link Expression} for datetime
 *
 * @category Expression
 */
export declare function Second<T extends DateTimeType>(datetime: EastFunction<T>): EastFunction<T extends NullType ? Nullable<IntegerType> : IntegerType>;
/**
 * Return the number of whole minutes elapsed since the start of the hour (0 - 59).
 *
 * @param datetime the {@link Expression} for datetime
 *
 * @category Expression
 */
export declare function Minute<T extends DateTimeType>(datetime: EastFunction<T>): EastFunction<T extends NullType ? Nullable<IntegerType> : IntegerType>;
/**
 * Return the number of whole hours elapsed since the start of the day (0 - 23).
 *
 * @param datetime the {@link Expression} for datetime
 *
 * @category Expression
 */
export declare function Hour<T extends DateTimeType>(datetime: EastFunction<T>): EastFunction<T extends NullType ? Nullable<IntegerType> : IntegerType>;
/**
 * Return the number of whole days elapsed since the start of the week (Monday = 0, ..., Sunday = 6).
 *
 * @param datetime the {@link Expression} for datetime
 *
 * @category Expression
 */
export declare function DayOfWeek<T extends DateTimeType>(datetime: EastFunction<T>): EastFunction<T extends NullType ? Nullable<IntegerType> : IntegerType>;
/**
 * Return the day number of the month (1 - 31).
 *
 * @param datetime the {@link Expression} for datetime
 *
 * @category Expression
 */
export declare function DayOfMonth<T extends DateTimeType>(datetime: EastFunction<T>): EastFunction<T extends NullType ? Nullable<IntegerType> : IntegerType>;
/**
 * Return the month number of the year (January = 1, ..., December = 12).
 *
 * @param datetime the {@link Expression} for datetime
 *
 * @category Expression
 */
export declare function Month<T extends DateTimeType>(datetime: EastFunction<T>): EastFunction<T extends NullType ? Nullable<IntegerType> : IntegerType>;
/**
 * Return the number of whole years since 0AD.
 *
 * @param datetime the {@link Expression} for datetime
 *
 * @category Expression
 */
export declare function Year<T extends DateTimeType>(datetime: EastFunction<T>): EastFunction<T extends NullType ? Nullable<IntegerType> : IntegerType>;