// Externals types
import { MarkOptional, DeepRequired } from 'ts-essentials'

// External modules
import EventEmitter from 'events'
import { randomBytes } from 'crypto'
import { TransactionRequest } from '@ethersproject/abstract-provider'
import {
  EventFilter,
  BaseContract,
  BigNumber,
  ContractTransaction,
  providers,
  Signer,
  VoidSigner
} from 'ethers'

// Our local types
import {
  ERC20Tornado,
  ERC20Tornado__factory,
  ETHTornado,
  ETHTornado__factory,
  TornadoInstance,
  TornadoInstance__factory,
  TornadoProxy__factory,
  TornadoProxy,
  ERC20,
  ERC20__factory,
  Multicall3Contract__factory
} from './deth'
import { Multicall3 } from './deth/Multicall3Contract'

// Local modules
import { Onchain, Cache, Docs } from '@tornado/sdk-data'
import { ErrorUtils, HexUtils, AsyncUtils } from '@tornado/sdk-utils'

// @ts-ignore
import { parseIndexableString } from 'pouchdb-collate'

// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  DECLARATIONS (MUST BE INLINED) ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

export type TornadoContracts = TornadoInstance | TornadoProxy | ETHTornado | ERC20Tornado | ERC20

export namespace Options {
  export interface Sync {
    startBlock?: number
    targetBlock?: number
    blockDelta?: number
    blockDivisor?: number
    concurrencyLimit?: number
    msTimeout?: number
    listenForEvents?: boolean
    persistentCache?: true
    cacheAdapter?: string
  }
}

// We use a vanilla provider here, but in reality we will probably
// add a censorship-checking custom derivative of it
type Provider = providers.Provider

// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ REST ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

/**
 * The Chain class stores Tornado-agnostic chain data and also
 * handles such interactions.
 */
export class Chain {
  public provider: Provider
  private _emptySigner: VoidSigner

  private _signer?: Signer
  private _chainId?: number
  private _symbol?: string
  private _fetched: boolean

  constructor(provider: Provider, signer?: Signer) {
    this.provider = provider
    this._signer = signer
    this._emptySigner = new VoidSigner('0x' + randomBytes(20).toString('hex'), provider)
    this._fetched = false
  }

  connectSigner(signer: Signer): void {
    this._signer = signer
  }

  async fetchChainData(): Promise<void> {
    const network = await this.provider.getNetwork()
    this._chainId = network.chainId
    this._symbol = await Onchain.getNetworkSymbol(String(network.chainId))
    this._fetched = true
  }

  private _signerConnected(parentCallName: string): void {
    if (!this._signer) throw ErrorUtils.getError(`Chain.${parentCallName}: signer must be connected!`)
  }

  private _propertiesFetched(parentCallName: string): void {
    if (!this._fetched)
      throw ErrorUtils.getError(
        `Chain.${parentCallName}: properties must be fetched first with \`fetchProperties\`.`
      )
  }

  get signer(): Signer {
    this._signerConnected('signer')
    return this._signer!
  }
  get id(): number {
    this._propertiesFetched('id')
    return this._chainId!
  }
  get symbol(): string {
    this._propertiesFetched('symbol')
    return this._symbol!
  }

  latestBlockNum(): Promise<number> {
    return this.provider.getBlockNumber()
  }

  getAccountBalance(account: string): Promise<BigNumber> {
    return this.provider.getBalance(account)
  }

  getGasPrice(): Promise<BigNumber> {
    return this.provider.getGasPrice()
  }

  getTokenContract(tokenAddress: string): ERC20 {
    return Contracts.getToken(tokenAddress, this._signer ?? this.provider)
  }

  async getTokenDecimals(token: string): Promise<BigNumber> {
    let treq = {
      to: token,
      data: '0x313ce567'
    }
    return BigNumber.from(await this._emptySigner.call(treq))
  }

  async getTokenBalance(account: string, token: string, normalized: boolean = false): Promise<BigNumber> {
    let treq = {
      to: token,
      data: '0x70a08231000000000000000000000000' + HexUtils.prepareAddress(account)
    }
    let divisor = normalized ? BigNumber.from(10).pow(await this.getTokenDecimals(token)) : 1
    return BigNumber.from(await this._emptySigner.call(treq)).div(divisor)
  }

  async populateBatchCall(
    callStruct: Array<MarkOptional<Multicall3.Call3ValueStruct, 'value'>>
  ): Promise<TransactionRequest> {
    if (callStruct[0].value)
      return await Multicall3Contract__factory.connect(
        await Onchain.getMulticall3Address(String(this.id)),
        this.provider
      ).populateTransaction.aggregate3Value(callStruct as Array<Multicall3.Call3ValueStruct>)

    return await Multicall3Contract__factory.connect(
      await Onchain.getMulticall3Address(String(this.id)),
      this.provider
    ).populateTransaction.aggregate3(callStruct)
  }

  async batchCall(
    callStruct: Array<MarkOptional<Multicall3.Call3ValueStruct, 'value'>>
  ): Promise<ContractTransaction> {
    if (this._signer)
      if (callStruct[0].value)
        return await Multicall3Contract__factory.connect(
          await Onchain.getMulticall3Address(String(this.id)),
          this._signer
        ).aggregate3Value(callStruct as Array<Multicall3.Call3ValueStruct>)
      else {
        return await Multicall3Contract__factory.connect(
          await Onchain.getMulticall3Address(String(this.id)),
          this.provider
        ).aggregate3(callStruct)
      }
    else throw ErrorUtils.getError('Chain.batchCall: no signer provided.')
  }
}

/**
 * This is Tornado-specific.
 */
export namespace Contracts {
  function _getContract<C extends TornadoContracts>(
    name: string,
    address: string,
    signerOrProvider: Signer | Provider
  ): C {
    if (name == 'TornadoInstance') {
      return TornadoInstance__factory.connect(address, signerOrProvider) as C
    } else if (name == 'TornadoProxy') {
      return TornadoProxy__factory.connect(address, signerOrProvider) as C
    } else if (name == 'ETHTornado') {
      return ETHTornado__factory.connect(address, signerOrProvider) as C
    } else if (name == 'ERC20Tornado') {
      return ERC20Tornado__factory.connect(address, signerOrProvider) as C
    } else {
      return ERC20__factory.connect(address, signerOrProvider) as C
    }
  }

  type Path = string
  const contractMap: Map<Path, BaseContract> = new Map<Path, BaseContract>()

  export function getProxy(network: string, signerOrProvider: Signer | Provider): TornadoProxy {
    const key = `TornadoProxy${network}`
    if (!contractMap.has(key)) {
      contractMap.set(
        key,
        _getContract<TornadoProxy>('TornadoProxy', Onchain.getProxyAddressSync(network), signerOrProvider)
      )
    }
    return contractMap.get(`TornadoProxy${network}`) as TornadoProxy
  }

  export function getInstance(
    network: string,
    token: string,
    denomination: string,
    signerOrProvider: Signer | Provider
  ): TornadoInstance {
    const key = `TornadoInstance${network}${token}${denomination}`
    if (!contractMap.has(key)) {
      contractMap.set(
        key,
        _getContract<TornadoInstance>(
          'TornadoInstance',
          Onchain.getInstanceAddressSync(network, token, denomination),
          signerOrProvider
        )
      )
    }
    return contractMap.get(key) as TornadoInstance
  }

  export function getToken(tokenAddress: string, signerOrProvider: Signer | Provider): ERC20 {
    if (!contractMap.has(tokenAddress))
      contractMap.set(tokenAddress, _getContract<ERC20>('ERC20', tokenAddress, signerOrProvider))
    return contractMap.get(tokenAddress) as ERC20
  }

  export function getTornToken(signerOrProvider: Signer | Provider): ERC20 {
    const key = '$TORN'
    if (!contractMap.has(key)) {
      contractMap.set(
        key,
        _getContract<ERC20>('ERC20', '0x77777feddddffc19ff86db637967013e6c6a116c', signerOrProvider)
      )
    }
    return contractMap.get(key) as ERC20
  }
}

export abstract class Synchronizer extends EventEmitter {
  async sync(
    eventName: string,
    filter: EventFilter,
    contract: BaseContract,
    cache: Cache.Syncable<Docs.Base>,
    options?: Options.Sync
  ): Promise<void> {
    const _options = await this._populateSyncOptions(options)

    // Assign pooler
    cache.initializePooler(cache.getCallbacks(contract), cache.getErrorHandlers(), _options.concurrencyLimit)

    // Decide whether we have a latest block
    const numEntries = (await cache.db.info()).doc_count

    // Check for synced blocks
    if (0 < numEntries) {
      const [lastSyncedBlock, ,] = parseIndexableString(
        (await cache.db.allDocs({ descending: true, limit: 1 })).rows[0].id
      )
      _options.startBlock = lastSyncedBlock < _options.startBlock ? _options.startBlock : lastSyncedBlock
      _options.blockDelta = Math.floor((_options.targetBlock - _options.startBlock) / _options.blockDivisor)
    }

    // Start synchronizing
    let dbPromises = []

    this.emit('debug', _options.startBlock, _options.targetBlock, _options.blockDelta)

    this.emit('sync', 'syncing')

    for (
      let currentBlock = _options.startBlock,
        blockDelta = _options.blockDelta,
        targetBlock = _options.targetBlock,
        concurrencyLimit = _options.concurrencyLimit;
      currentBlock < targetBlock;
      currentBlock += blockDelta
    ) {
      if (cache.pooler!.pending < concurrencyLimit) {
        const sum = currentBlock + blockDelta

        await AsyncUtils.timeout(_options.msTimeout)

        if (currentBlock + blockDelta < targetBlock) {
          await cache.pooler!.pool(currentBlock, sum)
        } else {
          await cache.pooler!.pool(currentBlock, sum - (sum % targetBlock))
        }

        this.emit('debug', currentBlock++, sum)
      } else {
        let res: Array<any> = await cache.pooler!.race()

        if (res.length != 0)
          dbPromises.push(
            cache.db.bulkDocs(res.map((el) => cache.buildDoc(el))).catch((err) => {
              throw ErrorUtils.ensureError(err)
            })
          )

        currentBlock -= blockDelta
      }
    }

    this.emit('sync', 'synced')

    // Immediately start listening if we're doing this
    if (_options.listenForEvents) this.listenForEvents(eventName, contract, filter, cache)

    // Then wait for all pooler requests to resolve
    let results = await cache.pooler!.all()

    // Then transform them, we know the shape in forward
    results = results.reduce((res: any[], response: any[]) => {
      if (response[0]) response.forEach((el: any) => res.push(cache.buildDoc(el)))
      return res
    }, [])

    // Then wait for old dbPromises to resolve
    await Promise.all(dbPromises)

    // Add the last docs
    await cache.db.bulkDocs(results).catch((err) => {
      throw ErrorUtils.ensureError(err)
    })
  }

  listenForEvents(
    name: string,
    contract: BaseContract,
    filter: EventFilter,
    cache: Cache.Syncable<Docs.Base>
  ) {
    contract.on(filter, (...eventArgs) => {
      this.emit(name, cache.name, cache.db.put(cache.buildDoc(eventArgs[eventArgs.length - 1])))
    })
  }

  clearListenerByIndex(contract: BaseContract, event: EventFilter, listenerIndex: number = 0): void {
    const listeners = contract.listeners()
    contract.off(event, listeners[listenerIndex])
  }

  protected abstract _populateSyncOptions(options?: Options.Sync): Promise<DeepRequired<Options.Sync>>
}