/**
 * Provides types and utilities for working with bulletin board contracts.
 *
 * @packageDocumentation
 */

import {
  type CoinPublicKey,
  type ContractAddress,
  encodeCoinPublicKey,
  convert_bigint_to_Uint8Array,
} from '@midnight-ntwrk/compact-runtime';
import { type Logger } from 'pino';
import type { BBoardDerivedState, BBoardContract, BBoardProviders, DeployedBBoardContract } from './common-types.js';
import {
  type BBoardPrivateState,
  Contract,
  createBBoardPrivateState,
  ledger,
  pureCircuits,
  witnesses,
  STATE,
} from '@midnight-ntwrk/bboard-contract';
import * as utils from './utils/index.js';
import { deployContract, findDeployedContract, withZswapWitnesses } from '@midnight-ntwrk/midnight-js-contracts';
import { combineLatest, map, tap, from, type Observable } from 'rxjs';

/** @internal */
const createBBoardContract = (coinPublicKey: CoinPublicKey): BBoardContract =>
  new Contract(withZswapWitnesses(witnesses)(encodeCoinPublicKey(coinPublicKey)));

/**
 * An API for a deployed bulletin board.
 */
export interface DeployedBBoardAPI {
  readonly deployedContractAddress: ContractAddress;
  readonly state$: Observable<BBoardDerivedState>;

  post: (message: string) => Promise<void>;
  takeDown: () => Promise<void>;
}

/**
 * Provides an implementation of {@link DeployedBBoardAPI} by adapting a deployed bulletin board
 * contract.
 *
 * @remarks
 * The `BBoardPrivateState` is managed at the DApp level by a private state provider. As such, this
 * private state is shared between all instances of {@link BBoardAPI}, and their underlying deployed
 * contracts. The private state defines a `'secretKey'` property that effectively identifies the current
 * user, and is used to determine if the current user is the poster of the message as the observable
 * contract state changes.
 *
 * In the future, Midnight.js will provide a private state provider that supports private state storage
 * keyed by contract address. This will remove the current workaround of sharing private state across
 * the deployed bulletin board contracts, and allows for a unique secret key to be generated for each bulletin
 * board that the user interacts with.
 */
// TODO: Update BBoardAPI to use contract level private state storage.
export class BBoardAPI implements DeployedBBoardAPI {
  /** @internal */
  private constructor(
    public readonly deployedContract: DeployedBBoardContract,
    providers: BBoardProviders,
    private readonly logger?: Logger,
  ) {
    this.deployedContractAddress = deployedContract.finalizedDeployTxData.contractAddress;
    this.state$ = combineLatest(
      [
        // Combine public (ledger) state with...
        providers.publicDataProvider.contractStateObservable(this.deployedContractAddress, { type: 'latest' }).pipe(
          map((contractState) => ledger(contractState.data)),
          tap((ledgerState) =>
            logger?.trace({
              ledgerStateChanged: {
                ledgerState: {
                  ...ledgerState,
                  state: ledgerState.state === STATE.occupied ? 'occupied' : 'vacant',
                  poster: utils.toHex(ledgerState.poster),
                },
              },
            }),
          ),
        ),
        // ...private state...
        //    since the private state of the bulletin board application never changes, we can query the
        //    private state once and always use the same value with `combineLatest`. In applications
        //    where the private state is expected to change, we would need to make this an `Observable`.
        from(providers.privateStateProvider.get('bboardPrivateState') as Promise<BBoardPrivateState>),
      ],
      // ...and combine them to produce the required derived state.
      (ledgerState, privateState) => {
        const hashedSecretKey = pureCircuits.public_key(
          privateState.secretKey,
          convert_bigint_to_Uint8Array(32, ledgerState.instance),
        );

        return {
          state: ledgerState.state,
          message: ledgerState.message.value,
          instance: ledgerState.instance,
          isOwner: utils.toHex(ledgerState.poster) === utils.toHex(hashedSecretKey),
        };
      },
    );
  }

  /**
   * Gets the address of the current deployed contract.
   */
  readonly deployedContractAddress: ContractAddress;

  /**
   * Gets an observable stream of state changes based on the current public (ledger),
   * and private state data.
   */
  readonly state$: Observable<BBoardDerivedState>;

  /**
   * Attempts to post a given message to the bulletin board.
   *
   * @param message The message to post.
   *
   * @remarks
   * This method can fail during local circuit execution if the bulletin board is currently occupied.
   */
  async post(message: string): Promise<void> {
    this.logger?.info(`postingMessage: ${message}`);

    const { txHash, blockHeight } =
      // EXERCISE 3: CALL THE post CIRCUIT AND SUBMIT THE TRANSACTION TO THE NETWORK
      await this.deployedContract.contractCircuitsInterface // EXERCISE ANSWER
        .post(message); // EXERCISE ANSWER

    this.logger?.trace({
      transactionAdded: {
        circuit: 'post',
        txHash,
        blockHeight,
      },
    });
  }

  /**
   * Attempts to take down any currently posted message on the bulletin board.
   *
   * @remarks
   * This method can fail during local circuit execution if the bulletin board is currently vacant,
   * or if the currently posted message isn't owned by the poster computed from the current private
   * state.
   */
  async takeDown(): Promise<void> {
    this.logger?.info('takingDownMessage');

    const { txHash, blockHeight } =
      // EXERCISE 4: CALL THE take_down CIRCUIT AND SUBMIT THE TRANSACTION TO THE NETWORK
      await this.deployedContract.contractCircuitsInterface // EXERCISE ANSWER
        .take_down(); // EXERCISE ANSWER

    this.logger?.trace({
      transactionAdded: {
        circuit: 'take_down',
        txHash,
        blockHeight,
      },
    });
  }

  /**
   * Deploys a new bulletin board contract to the network.
   *
   * @param providers The bulletin board providers.
   * @param logger An optional 'pino' logger to use for logging.
   * @returns A `Promise` that resolves with a {@link BBoardAPI} instance that manages the newly deployed
   * {@link DeployedBBoardContract}; or rejects with a deployment error.
   */
  static async deploy(providers: BBoardProviders, logger?: Logger): Promise<BBoardAPI> {
    logger?.info('deployContract');

    const deployedBBoardContract = await deployContract(
      // EXERCISE 5: FILL IN THE CORRECT ARGUMENTS TO deployContract
      providers, // EXERCISE ANSWER
      'bboardPrivateState', // EXERCISE ANSWER
      await BBoardAPI.getPrivateState(providers), // EXERCISE ANSWER
      createBBoardContract(providers.walletProvider.coinPublicKey), // EXERCISE ANSWER
    );

    logger?.trace({
      contractDeployed: {
        finalizedDeployTxData: deployedBBoardContract.finalizedDeployTxData,
      },
    });

    return new BBoardAPI(deployedBBoardContract, providers, logger);
  }

  /**
   * Finds an already deployed bulletin board contract on the network, and joins it.
   *
   * @param providers The bulletin board providers.
   * @param address The contract address of the deployed bulletin board contract to search for and join.
   * @param logger An optional 'pino' logger to use for logging.
   * @returns A `Promise` that resolves with a {@link BBoardAPI} instance that manages the joined
   * {@link DeployedBBoardContract}; or rejects with an error.
   */
  static async join(providers: BBoardProviders, contractAddress: ContractAddress, logger?: Logger): Promise<BBoardAPI> {
    logger?.info({
      joinContract: {
        contractAddress,
      },
    });

    const deployedBBoardContract = await findDeployedContract(
      providers,
      contractAddress,
      createBBoardContract(providers.walletProvider.coinPublicKey),
      {
        privateStateKey: 'bboardPrivateState',
        initialPrivateState: await BBoardAPI.getPrivateState(providers),
      },
    );

    logger?.trace({
      contractJoined: {
        finalizedDeployTxData: deployedBBoardContract.finalizedDeployTxData,
      },
    });

    return new BBoardAPI(deployedBBoardContract, providers, logger);
  }

  private static async getPrivateState(providers: BBoardProviders): Promise<BBoardPrivateState> {
    const existingPrivateState = await providers.privateStateProvider.get('bboardPrivateState');

    return existingPrivateState ?? createBBoardPrivateState(utils.randomBytes(32));
  }
}

/**
 * A namespace that represents the exports from the `'utils'` sub-package.
 *
 * @public
 */
export * as utils from './utils/index.js';

export * from './common-types.js';
