/// <reference types="node" />

/**
 * contains all of your service's dependencies and provides scheduling
 * options for checking those dependencies
 */
interface Copacetic extends NodeJS.EventEmitter {
  /**
   * The name of your service. This is output in the express
   * middleware when verbose is true
   */
  name: string,

  /**
   * Whether dependencies are currently being polled
   */

  isPolling: boolean,

  /**
   * True when there are no hard dependency failures
   */
  isHealthy: boolean,

  /**
   * When true, 'check' and 'waitFor' will return an instance
   * of Copacetic, if false a promise will be returned. It should
   * be noted that polling is unaffected by this field, and will
   * always return the Copacetic instance in use.
   */
  eventEmitterMode: boolean,

  /**
   * Health information on all registered services
   */
  healthInfo: Array<copacetic.Health>,

  /**
   * A full health report
   */
  healthReport: {
    isHealthy: boolean,
    name: string,
    dependencies: Array<copacetic.Health>
  }

  /**
   * Returns a registered dependency
   * Examples:
   *
   *  // With a name
   *  copacetic.getDependency('database')
   *
   *  // With a dependency
   *  copacetic.getDependency(dep)
   */
  getDependency (dependency: copacetic.Dependency|string): copacetic.Dependency,

  /**
   * Checks if a dependency exists
   * Examples:
   *
   *  // With a name
   *  copacetic.isDependencyRegistered('database')
   *
   *  // With a dependency
   *  copacetic.isDependencyRegistered(dep)
   */
  isDependencyRegistered (dependency: copacetic.Dependency|string): copacetic.Dependency,

  /**
   * Adds a dependency to a copacetic instance
   * Examples:
   *
   * copacetic.registerDependency({ name: 'database', url: 'memes.com' })
   *
   * copacetic.registerDependency({ name: 'cache', strategy: { type: 'redis' } })
   *
   * copacetic
   *  .registerDependency
   *  ({ name: 'service', strategy: { type: 'redis', adapter } })
   */
  registerDependency (options: copacetic.DependencyOptions): Copacetic,

  /**
   * Removes a dependency from a copacetic instance
   * Examples:
   *
   *  // With a name
   *  copacetic.deregisterDependency('database')
   *
   *  // With a dependency
   *  copacetic.deregisterDependency(dep)
   */
  deregisterDependency (dependency: copacetic.Dependency|string): Copacetic,

  /**
   * Polls the health of all registered dependencies
   */
  pollAll (options: {
    /**
     * The rate at which dependencies will be polled, of the format
     * '5 seconds', '1m minute 20 seconds' etc.
     */
    interval?: string,

    /**
     * check the health of dependencies in sequence, or parallel
     */
    parallel?: boolean,

    /**
     * Schedule the next check as soon as a poll starts, or wait
     */
    schedule?: string
  }): Copacetic,

  /**
   * Polls the health of a single dependency
   * Example:
   *
   *  copacetic.poll({
   *    name: 'database',
   *    interval: '1 minute 30 seconds',
   *    parallel: false
   *  })
   */
  poll (options: {
    /*
     * The name used when registering the dependency
     */
    name: string,

    /**
     * The rate at which dependencies will be polled, of the format
     * '5 seconds', '1m minute 20 seconds' etc.
     */
    interval?: string,

    /**
     * Check the health of dependencies in sequence, or parallel
     */
    parallel?: boolean,

    /**
     * Schedule the next check as soon as a poll starts, or wait
     */
    schedule?: string
  }): Copacetic,

  /**
   * Polls the health of a set of dependencies
   * Example:
   *
   *  copacetic.poll({
   *    dependencies: [
   *      { name: 'database', retries: 2 },
   *      { name: 'cache' }
   *    ],
   *    interval: '1 minute 30 seconds'
   *    parallel: false
   *  })
   */
  poll (options: {
    /**
     * The dependencies to be health checked
     */
    dependencies: Array<
      {
        /*
         * The name used when registering the dependency
         */
        name: string,
        /*
         * The number of times to retry a health check, before marking as unhealthy
         */
        retries?: number,
        /*
         * The maximum interval of time to wait when retrying
         */
        maxDelay?: number
      }
    >,
    /**
     * The rate at which dependencies will be polled, of the format
     * '5 seconds', '1m minute 20 seconds' etc.
     */
    interval?: string,
    /**
     * Check the health of dependencies in sequence, or parallel
     */
    parallel?: boolean,
    /**
     * Schedule the next check as soon as a poll starts, or wait
     */
    schedule?: string
  }): Copacetic,


  /**
   * stops polling dependencies
   */
  stop (): void,

  /**
   * Checks the health of all registered dependencies
   * Example:
   *
   *  copacetic.checkAll(false)
   */
  checkAll (
    /**
     * Check the health of dependencies in sequence, or parallel
     */
    parallel: boolean
  ): Copacetic | Promise<Array<copacetic.Health>>,

  /**
   * Checks the health of a single dependency
   * Example:
   *  // when in event emitter mode
   *  copacetic.check({ name: 'database' }).on('healthy', () => {})
   *  copacetic.check({ name: 'cache', retries: 2 }).on('healthy', () => {})
   *
   *  // when in promise mode
   *  copacetic.check<Promise<Copacetic.Health>>({ name: 'database' })
   *  .then((res) => { ... })
   */
  check<R = Copacetic> (options: {
    /*s
     * The name used when registering the dependency
     */
    name: string,

    /*
     * The number of times to retry a health check, before marking as unhealthy
     */
    retries?: number,

    /*
     * The maximum interval of time to wait when retrying
     */
    maxDelay?: number
  }): R,

  /**
   * Checks the health of a set of dependencies
   * Example:
   *  // when in event emitter mode
   *  copacetic.check({
   *    dependencies: [
   *      { name: 'database', retries: 2 },
   *      { name: 'cache' }
   *    ],
   *    parallel: false
   *  })
   *  .on('healthy', (health: Copacetic.Health) => { ... })
   *  .on('unhealthy', (health: Copacetic.Health) => { ... })
   *
   *  // when in promise mode
   *  copacetic.check<Promise<Array<Copacetic.Health>>>({ dependencies })
   *  .then((res) => { ... })
   *
   */
  check<R = Copacetic> (options: {
    /**
     * The dependencies to be health checked
     */
    dependencies: Array<
      {
        /*
         * The name used when registering the dependency
         */
        name: string,
        /*
         * The number of times to retry a health check, before marking as unhealthy
         */
        retries?: number,
        /*
         * The maximum interval of time to wait when retrying
         */
        maxDelay?: number
      }
    >,

    /**
     * Check the health of dependencies in sequence, or parallel
     */
    parallel?: boolean
  }): R,

  /**
   * If in cluster mode and this instance has been attached to it, ask the master process for health information of the full cluster
   */
  checkCluster: function () :Promise<Copacetic.healthReport>

  /**
   * Waits for a single dependency to become healthy
   * Example:
   *  // when in event emitter mode
   *  copacetic.waitFor({ name: 'database' })
   *  .on('healthy', (health: Copacetic.Health) => { ... })
   *
   *  // when in promise mode
   *  copacetic.waitFor<Copacetic.Health>({ name: 'database' })
   *  .then((res) => { ... })
   */
  waitFor<R = Copacetic> (options: {
    /*
     *the name used when registering the dependency
     */
    name: string,

    /*
     * The maximum interval of time to wait when retrying
     */
    maxDelay?: number
  }): R

  /**
   * Waits for a set of dependencies to become healthy
   * Example:
   *  // when in event emitter mode
   *  copacetic.waitFor({
   *    dependencies: [
   *      { name: 'database', maxDelay: '10 seconds' },
   *      { name: 'cache' }
   *    ],
   *    parallel: false
   *  })
   *  .on('healthy', (health: Copacetic.Health) => { ... })
   *
   *  // when in promise mode
   *  copacetic.waitFor<Array<Copacetic.Health>>({
   *    dependencies: []
   *  }).then((res) => { ... })
   *
   */
  waitFor<R = Copacetic> (options: {
    /**
     * The dependencies to be health checked
     */
    dependencies: Array<
      {
        /*
         * The name used when registering the dependency
         */
        name: string,
        /*
         * The maximum interval of time to wait when retrying
         */
        maxDelay?: number
      }
    >,

    /**
     * Check the health of dependencies in sequence, or parallel
     */
    parallel?: boolean
  }): R,

  on (event: string | symbol, listener: Function): this,

  /**
   * Register an event listener for the 'health' event. Used when checking
   * the health of a single dependency, i.e. copacetic.check({ name: '' })
   */
  on (
    event: 'health',
    listener: (payload: Array<copacetic.Health>, stop: Function) => void
  ): this,

  /**
   * Register an event listener for 'healthy' event. used when checking
   * the health of multiple dependencies, i.e. copacetic.check({ dependencies })
   */
  on (
    event: 'healthy',
    listener: (payload: copacetic.Health , stop: Function) => void
  ): this,

  /**
   * Register an event listener for 'unhealthy' event. used when checking
   * the health of multiple dependencies, i.e. copacetic.check({ dependencies })
   */
  on (
    event: 'unhealthy',
    listener: (payload: copacetic.Health, stop: Function) => void
  ): this,
}


declare function Copacetic (
  /**
   * The name of your service. This is output in the express
   * middleware when verbose is true
   */
  name?: string,
  /**
   * By default when using check/checkAll/waitFor events are emitted.
   * If eventEmitterMode is set to false then promises will be returned
   * instead. poll/pollAll remain unaffected by this, and will always
   * return an event emitter.
   */
  eventEmitterMode?: boolean
): Copacetic

declare namespace Copacetic {
  /**
   * holds information about the health of a dependency, and executes strategies for
   * checking a dependency's health
   */
  interface Dependency {
    /**
     * The identifier used for the dependency
     */
    name: string,

    /**
     * The relationship between a service and dependency
     */
    level: dependencyLevel,

    /**
     * Whether the dependency passed a health check
     */
    healthy: boolean,

    /**
     * The method used for checking a dependencies health
     */
    healthStrategy: HealthStrategy,

    /**
     * How a health strategy will delay itself before executing again
     */
    backoffStrategy: BackoffStrategy,

    /**
     * The description of a dependency's health
     */
    healthSummary: Health,

    /**
     * sets a dependency's status to healthy
     */
    onHealthy (): void,

    /**
     * sets a dependency's status to unhealthy
     */
    onUnhealthy (): void,

    /**
     * performs any cleanup needed
     */
    cleanup (): void,

    check (
      /**
       * The number of times a dependency's health will be checked
       * before giving up
       */
      retries?: number,

      /*
       * The maximum interval of time to wait when retrying
       */
      maxDelay?: number
    ): Promise<Health>,
  }

  /**
   * The description of a dependency's health
   */
   export interface Health {
    /**
     * The name of the dependency that this health report belongs to
     */
    name: string,

    /**
     * Whether the dependency passed a health check
     */
    healthy: boolean,

    /**
     * The relationship between a service and dependency
     */
    level: dependencyLevel,

    /**
     * The last time the dependency was health checked
     */
    lastChecked: Date
  }

  /**
   * A method for checking a dependencies health
   */
  export interface HealthStrategy {
    new (
      /**
       * How long to wait until giving up. of the format
       * '5 seconds', '1m minute 20 seconds' etc.
       */
      timeout: string
    ) : HealthStrategy

    /**
     * Check a dependency's health
     * Example:
     *
     * dependency
     *  .check('my-resource', '5 seconds')
     *  .then(() => { ... do something now it's healthy })
     *  .then(() => { ... handle degraded state })
     */
    check (
      /**
       * The resource accessed when checking the health of a dependency
       */
      url: string,

      /**
       * How long to wait until giving up. of the format
       * '5 seconds', '1m minute 20 seconds' etc.
       */
      timeout: string
    ) : Promise<boolean>

    /**
     * Perform any cleanup operation, if needed, when a dependency
     * is no longer in used
     * Example:
     *
     * dependency
     *  .cleanup()
     *  .then(() => { ... cleanup went OK })
     *  .then(() => { ... cleanup failed })
     */
    cleanup (...args: any[]) : Promise<boolean>
  }

  /**
   * Some function that returns a promise
   */
  export interface BackOffCallable {
    () : Promise<boolean>
  }

  /**
   * A way of delaying some callable. Returns a promise after X
   * retries
   */
  export interface BackoffStrategy {
    new(
      /*
       * The number of times execute will try the callable before giving up
       */
      maxRetries: number,
      /*
       * The maximum interval of time to wait when retrying
       */
      maxDelay?: number
    ) : BackoffStrategy

    /**
     * execute some function, retrying some set number of times before failing
     */
    execute (callable: BackOffCallable) : Promise<boolean>
  }

  /**
   * Options used for creating a health strategy via the
   * HealthStrategy factory
   */
  export interface HealthStrategyOptions {
    /**
     * The type of health strategy to use, i.e. http, mongodb, redis
     */
    type: 'http' | 'mongodb' | 'redis' | 'postgres',

    /**
     * The configuration options for the type of strategy you want to use
     * i.e. timeout
     */
    opts?: object,

    /**
     * A custom adapter to use for a health strategy, i.e. you may want to use some
     * library/database driver copacetic doesn't support out of the box
     */
    adapter?: Function
  }

  /**
   * Options used for registering a new dependency
   */
  export interface DependencyOptions {
    /**
     * Configuration options for a health strategy
     */
    strategy?: HealthStrategyOptions,

    /**
     * The relationship between a service and dependency
     */
    level?: dependencyLevel,

    /**
     * The identifier used for a dependency
     */
    name: string,

    /**
     * The resource accessed when checking the health of a dependency
     */
    url: string
  }

  /**
   * Options for using the express middleware
   */
  export interface MiddlewareOptions {
    /**
     * The instance of copacetic that will serve health information
     */
    copacetic: Copacetic,

    /**
     * The rate at which dependencies will be polled, of the format
     * '5 seconds', '1m minute 20 seconds' etc.
     */
    interval?: string,

    /**
     * The dependencies to be health checked
     */
    dependencies?: Array<copacetic.Dependency>,

    /**
     * check the health of dependencies in sequence, or parallel
     */
    parallel?: boolean,

    /**
     * schedule the next check as soon as a poll starts, or wait
     */
    schedule?: string,

    /**
     * When true the middleware will output all health information
     * for the registered dependencies. If not verbose, only a status code
     * will be returned
     */
    verbose?: boolean
  }

  /**
   * Describes the relationship between your service and a dependency
   */
  export enum dependencyLevel {
    /**
     * Your service cannot function when a hard dependency is unavailable
     */
    HARD,

    /*
     * Your service can still run, even if this dependency is unavailable
     */
    SOFT
  }
  /**
   * Express middleware for a copacetic instance
   */
  export function Middleware(options: MiddlewareOptions): Function

  /**
   * Factory function for providing different health strategies
   */
  export function HealthStrategy(options: HealthStrategyOptions): Function

  export namespace cluster {
    interface AttachOptions {
      dependency?: {
        level: dependencyLevel
      }
    }
    export function attach (copacetic: Copacetic, attachOptions?: AttachOptions): Function
  }
}

export = Copacetic