import camelCase from "camelcase";
import EventEmitter from "eventemitter3";
import * as bs58 from "bs58";
import {
  Signer,
  PublicKey,
  SystemProgram,
  TransactionInstruction,
  Commitment,
} from "@solana/web3.js";
import Provider from "../../provider";
import { Idl, IdlTypeDef } from "../../idl";
import Coder, {
  ACCOUNT_DISCRIMINATOR_SIZE,
  accountDiscriminator,
  accountSize,
} from "../../coder";
import { Subscription, Address, translateAddress } from "../common";
import { getProvider } from "../../";
import * as pubkeyUtil from "../../utils/pubkey";

export default class AccountFactory {
  public static build(
    idl: Idl,
    coder: Coder,
    programId: PublicKey,
    provider: Provider
  ): AccountNamespace {
    const accountFns: AccountNamespace = {};

    idl.accounts.forEach((idlAccount) => {
      const name = camelCase(idlAccount.name);
      accountFns[name] = new AccountClient(
        idl,
        idlAccount,
        programId,
        provider,
        coder
      );
    });

    return accountFns;
  }
}

/**
 * The namespace provides handles to an [[AccountClient]] object for each
 * account in a program.
 *
 * ## Usage
 *
 * ```javascript
 * account.<account-client>
 * ```
 *
 * ## Example
 *
 * To fetch a `Counter` account from the above example,
 *
 * ```javascript
 * const counter = await program.account.counter.fetch(address);
 * ```
 *
 * For the full API, see the [[AccountClient]] reference.
 */
export interface AccountNamespace {
  [key: string]: AccountClient;
}

export class AccountClient {
  /**
   * Returns the number of bytes in this account.
   */
  get size(): number {
    return this._size;
  }
  private _size: number;

  /**
   * Returns the program ID owning all accounts.
   */
  get programId(): PublicKey {
    return this._programId;
  }
  private _programId: PublicKey;

  /**
   * Returns the client's wallet and network provider.
   */
  get provider(): Provider {
    return this._provider;
  }
  private _provider: Provider;

  /**
   * Returns the coder.
   */
  get coder(): Coder {
    return this._coder;
  }
  private _coder: Coder;

  private _idlAccount: IdlTypeDef;

  constructor(
    idl: Idl,
    idlAccount: IdlTypeDef,
    programId: PublicKey,
    provider?: Provider,
    coder?: Coder
  ) {
    this._idlAccount = idlAccount;
    this._programId = programId;
    this._provider = provider ?? getProvider();
    this._coder = coder ?? new Coder(idl);
    this._size = ACCOUNT_DISCRIMINATOR_SIZE + accountSize(idl, idlAccount);
  }

  /**
   * Returns a deserialized account.
   *
   * @param address The address of the account to fetch.
   */
  async fetch(address: Address): Promise<Object> {
    const accountInfo = await this._provider.connection.getAccountInfo(
      translateAddress(address)
    );
    if (accountInfo === null) {
      throw new Error(`Account does not exist ${address.toString()}`);
    }

    // Assert the account discriminator is correct.
    const discriminator = await accountDiscriminator(this._idlAccount.name);
    if (discriminator.compare(accountInfo.data.slice(0, 8))) {
      throw new Error("Invalid account discriminator");
    }

    return this._coder.accounts.decode(this._idlAccount.name, accountInfo.data);
  }

  /**
   * Returns all instances of this account type for the program.
   */
  async all(filter?: Buffer): Promise<ProgramAccount<any>[]> {
    let bytes = await accountDiscriminator(this._idlAccount.name);
    if (filter !== undefined) {
      bytes = Buffer.concat([bytes, filter]);
    }

    let resp = await this._provider.connection.getProgramAccounts(
      this._programId,
      {
        commitment: this._provider.connection.commitment,
        filters: [
          {
            memcmp: {
              offset: 0,
              bytes: bs58.encode(bytes),
            },
          },
        ],
      }
    );
    return resp.map(({ pubkey, account }) => {
      return {
        publicKey: pubkey,
        account: this._coder.accounts.decode(
          this._idlAccount.name,
          account.data
        ),
      };
    });
  }

  /**
   * Returns an `EventEmitter` emitting a "change" event whenever the account
   * changes.
   */
  subscribe(address: Address, commitment?: Commitment): EventEmitter {
    if (subscriptions.get(address.toString())) {
      return subscriptions.get(address.toString()).ee;
    }

    const ee = new EventEmitter();
    address = translateAddress(address);
    const listener = this._provider.connection.onAccountChange(
      address,
      (acc) => {
        const account = this._coder.accounts.decode(
          this._idlAccount.name,
          acc.data
        );
        ee.emit("change", account);
      },
      commitment
    );

    subscriptions.set(address.toString(), {
      ee,
      listener,
    });

    return ee;
  }

  /**
   * Unsubscribes from the account at the given address.
   */
  unsubscribe(address: Address) {
    let sub = subscriptions.get(address.toString());
    if (!sub) {
      console.warn("Address is not subscribed");
      return;
    }
    if (subscriptions) {
      this._provider.connection
        .removeAccountChangeListener(sub.listener)
        .then(() => {
          subscriptions.delete(address.toString());
        })
        .catch(console.error);
    }
  }

  /**
   * Returns an instruction for creating this account.
   */
  async createInstruction(
    signer: Signer,
    sizeOverride?: number
  ): Promise<TransactionInstruction> {
    const size = this.size;

    return SystemProgram.createAccount({
      fromPubkey: this._provider.wallet.publicKey,
      newAccountPubkey: signer.publicKey,
      space: sizeOverride ?? size,
      lamports:
        await this._provider.connection.getMinimumBalanceForRentExemption(
          sizeOverride ?? size
        ),
      programId: this._programId,
    });
  }

  /**
   * Function returning the associated account. Args are keys to associate.
   * Order matters.
   */
  async associated(...args: Array<PublicKey | Buffer>): Promise<any> {
    const addr = await this.associatedAddress(...args);
    return await this.fetch(addr);
  }

  /**
   * Function returning the associated address. Args are keys to associate.
   * Order matters.
   */
  async associatedAddress(
    ...args: Array<PublicKey | Buffer>
  ): Promise<PublicKey> {
    return await pubkeyUtil.associated(this._programId, ...args);
  }
}

/**
 * @hidden
 *
 * Deserialized account owned by a program.
 */
export type ProgramAccount<T = any> = {
  publicKey: PublicKey;
  account: T;
};

// Tracks all subscriptions.
const subscriptions: Map<string, Subscription> = new Map();