refactor(autoscaling): introduce Schedule classes for scaling

packages/@aws-cdk/aws-applicationautoscaling/lib/schedule.ts

@@ -0,0 +1,157 @@
+/**
+ * Schedule for scheduled scaling actions
+ */
+export abstract class Schedule {
+  /**
+   * Construct a schedule from a literal schedule expression
+   *
+   * @param expression The expression to use. Must be in a format that Application AutoScaling will recognize
+   */
+  public static expression(expression: string): Schedule {
+    return new LiteralSchedule(expression);
+  }
+
+  /**
+   * Construct a schedule from an interval and a time unit
+   */
+  public static rate(interval: number, unit: TimeUnit): Schedule {
+    const unitStr = interval !== 1 ? `${unit}s` : unit;
+
+    return new LiteralSchedule(`rate(${interval} ${unitStr})`);
+  }
+
+  /**
+   * Construct a Schedule from a moment in time
+   */
+  public static at(moment: Date) {
+    return new LiteralSchedule(`at(${formatISO(moment)})`);
+  }
+
+  /**
+   * Create a schedule from a set of cron fields
+   */
+  public static cron(options: CronOptions): Schedule {
+    if (options.weekDay !== undefined && options.day !== undefined) {
+      throw new Error(`Cannot supply both 'day' and 'weekDay', use at most one`);
+    }
+
+    const minute = fallback(options.minute, '*');
+    const hour = fallback(options.hour, '*');
+    const month = fallback(options.month, '*');
+    const year = fallback(options.year, '*');
+
+    // Weekday defaults to '?' if not supplied. If it is supplied, day must become '?'
+    const day = fallback(options.day, options.weekDay !== undefined ? '?' : '*');
+    const weekDay = fallback(options.weekDay, '?');
+
+    return new LiteralSchedule(`cron(${minute} ${hour} ${day} ${month} ${weekDay} ${year})`);
+  }
+
+  /**
+   * Retrieve the expression for this schedule
+   */
+  public abstract readonly expressionString: string;
+
+  protected constructor() {
+  }
+}
+
+/**
+ * What unit to interpret the rate in
+ */
+export enum TimeUnit {
+  /**
+   * The rate is in minutes
+   */
+  Minute = 'minute',
+
+  /**
+   * The rate is in hours
+   */
+  Hour = 'hour',
+
+  /**
+   * The rate is in days
+   */
+  Day = 'day'
+}
+
+/**
+ * Options to configure a cron expression
+ *
+ * All fields are strings so you can use complex expresions. Absence of
+ * a field implies '*' or '?', whichever one is appropriate.
+ *
+ * @see https://docs.aws.amazon.com/AmazonCloudWatch/latest/events/ScheduledEvents.html#CronExpressions
+ */
+export interface CronOptions {
+  /**
+   * The minute to run this rule at
+   *
+   * @default - Every minute
+   */
+  readonly minute?: string;
+
+  /**
+   * The hour to run this rule at
+   *
+   * @default - Every hour
+   */
+  readonly hour?: string;
+
+  /**
+   * The day of the month to run this rule at
+   *
+   * @default - Every day of the month
+   */
+  readonly day?: string;
+
+  /**
+   * The month to run this rule at
+   *
+   * @default - Every month
+   */
+  readonly month?: string;
+
+  /**
+   * The year to run this rule at
+   *
+   * @default - Every year
+   */
+  readonly year?: string;
+
+  /**
+   * The day of the week to run this rule at
+   *
+   * @default - Any day of the week
+   */
+  readonly weekDay?: string;
+}
+
+class LiteralSchedule extends Schedule {
+  constructor(public readonly expressionString: string) {
+    super();
+  }
+}
+
+function fallback<T>(x: T | undefined, def: T): T {
+  return x === undefined ? def : x;
+}
+
+function formatISO(date?: Date) {
+  if (!date) { return undefined; }
+
+  return date.getUTCFullYear() +
+    '-' + pad(date.getUTCMonth() + 1) +
+    '-' + pad(date.getUTCDate()) +
+    'T' + pad(date.getUTCHours()) +
+    ':' + pad(date.getUTCMinutes()) +
+    ':' + pad(date.getUTCSeconds());
+
+  function pad(num: number) {
+    if (num < 10) {
+      return '0' + num;
+    }
+    return num;
+  }
+}

packages/@aws-cdk/aws-autoscaling/lib/schedule.ts

@@ -0,0 +1,96 @@
+/**
+ * Schedule for scheduled scaling actions
+ */
+export abstract class Schedule {
+  /**
+   * Construct a schedule from a literal schedule expression
+   *
+   * @param expression The expression to use. Must be in a format that AutoScaling will recognize
+   * @see http://crontab.org/
+   */
+  public static expression(expression: string): Schedule {
+    return new LiteralSchedule(expression);
+  }
+
+  /**
+   * Create a schedule from a set of cron fields
+   */
+  public static cron(options: CronOptions): Schedule {
+    if (options.weekDay !== undefined && options.day !== undefined) {
+      throw new Error(`Cannot supply both 'day' and 'weekDay', use at most one`);
+    }
+
+    const minute = fallback(options.minute, '*');
+    const hour = fallback(options.hour, '*');
+    const month = fallback(options.month, '*');
+
+    // Weekday defaults to '?' if not supplied. If it is supplied, day must become '?'
+    const day = fallback(options.day, options.weekDay !== undefined ? '?' : '*');
+    const weekDay = fallback(options.weekDay, '?');
+
+    return new LiteralSchedule(`${minute} ${hour} ${day} ${month} ${weekDay}`);
+  }
+
+  /**
+   * Retrieve the expression for this schedule
+   */
+  public abstract readonly expressionString: string;
+
+  protected constructor() {
+  }
+}
+
+/**
+ * Options to configure a cron expression
+ *
+ * All fields are strings so you can use complex expresions. Absence of
+ * a field implies '*' or '?', whichever one is appropriate.
+ *
+ * @see http://crontab.org/
+ */
+export interface CronOptions {
+  /**
+   * The minute to run this rule at
+   *
+   * @default - Every minute
+   */
+  readonly minute?: string;
+
+  /**
+   * The hour to run this rule at
+   *
+   * @default - Every hour
+   */
+  readonly hour?: string;
+
+  /**
+   * The day of the month to run this rule at
+   *
+   * @default - Every day of the month
+   */
+  readonly day?: string;
+
+  /**
+   * The month to run this rule at
+   *
+   * @default - Every month
+   */
+  readonly month?: string;
+
+  /**
+   * The day of the week to run this rule at
+   *
+   * @default - Any day of the week
+   */
+  readonly weekDay?: string;
+}
+
+class LiteralSchedule extends Schedule {
+  constructor(public readonly expressionString: string) {
+    super();
+  }
+}
+
+function fallback<T>(x: T | undefined, def: T): T {
+  return x === undefined ? def : x;
+}