added interface description to the readme

README.md

@@ -1 +1,100 @@
 # @nrd/fua.module.scheduler
+
+## Interface
+
+```ts
+type IdentifierString = string
+type DateValue = number
+type DateString = string
+type CronString = string
+
+type DateOption = DateValue | DateString | Date
+type ScheduleOption = CronString | DateOption | null
+
+type CronDate = Date | {
+    addYear(): void,
+    addMonth(): void,
+    addDay(): void,
+    addHour(): void,
+    addMinute(): void,
+    addSecond(): void,
+    subtractYear(): void,
+    subtractMonth(): void,
+    subtractDay(): void,
+    subtractHour(): void,
+    subtractMinute(): void,
+    subtractSecond(): void,
+    toDate(): Date,
+    isLastDayOfMonth(): boolean,
+    isLastWeekdayOfMonth(): boolean
+}
+
+type CronExpression = {
+    next(): CronDate,
+    prev(): CronDate,
+    hasNext(): boolean,
+    hasPrev(): boolean,
+    iterate(steps: number, callback?: Function): Array<CronDate>,
+    reset(newDate?: number | string | Date): void,
+    stringify(includeSeconds?: boolean): string
+}
+
+declare class Schedule {
+    constructor(id: IdentifierString, schedule: ScheduleOption): this
+
+    /** The 'id' of the schedule represents the event that will be triggered for the scheduler. */
+    id: IdentifierString
+
+    /** A getter to the time this schedule will trigger next in epoch milliseconds. */
+    nextTime: DateValue
+
+    /** A getter to the time this schedule has triggered last in epoch milliseconds. */
+    lastTime: DateValue
+
+    /** An indicator whether the schedule has been destroyed or not. A destroyed schedule cannot be recovered. */
+    destroyed: boolean
+
+    /** The trigger method is usually called by the scheduler but can be called manually. */
+    trigger(): this
+
+    /** The 'trigger' event occurs when the trigger function is called. */
+    onTrigger(callback: Function): this
+
+    on(event: 'trigger' | 'update' | 'destroy', callback: Function): this
+    once(event: 'trigger' | 'update' | 'destroy', callback: Function): this
+    off(event: 'trigger' | 'update' | 'destroy', callback: Function): this
+
+    /** A generic json representation for the current schedule state. */
+    toJSON(): { id: IdentifierString, manual?: boolean, onetime?: boolean, recurring?: boolean, lastTime?: DateValue, nextTime?: DateValue, destroyed?: boolean }
+}
+
+declare class Scheduler {
+    constructor(schedules?: { [key: IdentifierString]: ScheduleOption }): this
+
+    /** A method to check whether a specific 'id' is already scheduled. */
+    isScheduled(scheduleId: IdentifierString): boolean
+
+    /** A method to check whether an object is a schedule from this scheduler. */
+    isSchedule(schedule: Schedule): boolean
+
+    /** A method to retrieve an existing schedule. */
+    getSchedule(scheduleId: IdentifierString): Schedule | null
+
+    /** A method to create a new schedule. Depending on the input argument the schedule is recurring or triggered once. */
+    createSchedule(scheduleId: IdentifierString, scheduleTime: ScheduleOption): Schedule
+
+    /** A method to append a schedule that has been created outside the scheduler. */
+    appendSchedule(schedule: Schedule): Schedule
+
+    /** A method to remove a recurring schedule or a one time schedule that has not been triggered yet. */
+    removeSchedule(scheduleId: IdentifierString): this
+
+    on(event: IdentifierString, callback: (schedule: Schedule) => any): this
+    once(event: IdentifierString, callback: (schedule: Schedule) => any): this
+    off(event: IdentifierString, callback: (schedule: Schedule) => any): this
+}
+
+declare function isCronString(value: unknown): value is CronString
+
+declare function parseCronExpression(value: CronString): CronExpression
+```