import { JsonRpcProvider } from '@ethersproject/providers'
import { AVERAGE_L1_BLOCK_TIME } from 'constants/chains'
import ConfiguredJsonRpcProvider from 'rpc/ConfiguredJsonRpcProvider'

/**
 * A controller which marks itself disabled on an error, and re-enables itself using exponential backoff.
 * After each retry, it will wait twice as long to retry again. After a success, it will reset the backoff.
 */
class Controller {
  private isEnabled = true
  private timeout: ReturnType<typeof setTimeout> | undefined
  private exponentialBackoffFactor = 1

  constructor(private minimumBackoffTime: number) {}

  private reset() {
    this.isEnabled = true

    clearTimeout(this.timeout)
    this.timeout = undefined
  }

  onSuccess() {
    this.reset()
    this.exponentialBackoffFactor = 1
  }

  /**
   * Called onError.
   * Idempotent - calling this multiple times will *not* reset the exponential backoff timer.
   */
  onError() {
    this.isEnabled = false
    if (!this.timeout) {
      this.timeout = setTimeout(() => {
        this.reset()
        this.exponentialBackoffFactor *= 2
      }, this.minimumBackoffTime * this.exponentialBackoffFactor)
    }
  }

  get enabled() {
    return this.isEnabled
  }
}

interface ControlledProvider {
  provider: JsonRpcProvider
  controller: Controller
}

interface AppJsonRpcProviderOptions {
  minimumBackoffTime?: number
}

/**
 * An application-specific JSON-RPC provider.
 *
 * This super-provider will instantiate providers for all supported JSON-RPC URLs, so that it may use them as fallbacks.
 * It will use the first (primary) JSON-RPC URL unless there is issue, at which point it will fallback to the next, &c.,
 * retrying the former using exponential backoff. This prevents secondary URLs from permanently overtaking primary URLs.
 */
export default class AppJsonRpcProvider extends ConfiguredJsonRpcProvider {
  providers: ReadonlyArray<ControlledProvider>

  constructor(
    providers: JsonRpcProvider[],
    { minimumBackoffTime = AVERAGE_L1_BLOCK_TIME }: AppJsonRpcProviderOptions = {}
  ) {
    if (providers.length === 0) throw new Error('Missing providers for AppJsonRpcProvider')
    super(undefined, providers[0].network)
    // AppJsonRpcProvider configures its own pollingInterval, so the encapsulated providers do not need to poll.
    // providers.forEach((provider) => (provider.pollingInterval = Infinity))
    this.providers = providers.map((provider) => ({ provider, controller: new Controller(minimumBackoffTime) }))
  }

  async perform(method: string, params: { [name: string]: any }): Promise<any> {
    const sortedProviders = AppJsonRpcProvider.sortProviders(this.providers)
    for (const { provider, controller } of sortedProviders) {
      try {
        const result = await provider.perform(method, params)
        controller.onSuccess()
        return result
      } catch (error) {
        console.warn('rpc action failed', error)
        controller.onError()
      }
    }
    throw new Error(`All providers failed to perform the operation: ${method}`)
  }

  static sortProviders(providers: ReadonlyArray<ControlledProvider>): Array<ControlledProvider> {
    // Try enabled providers before resorting to disabled providers.
    // Note that we do not filtered out disabled providers.
    return [...providers].sort(({ controller: { enabled: a } }, { controller: { enabled: b } }) => {
      if (a && !b) {
        return -1
      } else if (!a && b) {
        return 1
      } else {
        return 0 // sort is stable
      }
    })
  }
}
