// @flow

import assert from 'assert';
import * as BufferLayout from 'buffer-layout';
import nacl from 'tweetnacl';
import bs58 from 'bs58';

import * as Layout from './layout';
import {PublicKey} from './publickey';
import type {Account} from './account';

/**
 * @typedef {string} TransactionSignature
 */
export type TransactionSignature = string;

/**
 * @typedef {string} TransactionId
 */
export type TransactionId = string;

/**
 * List of TransactionInstruction object fields that may be initialized at construction
 *
 * @typedef {Object} TransactionInstructionCtorFields
 * @property {?Array<PublicKey>} keys
 * @property {?PublicKey} programId
 * @property {?Buffer} userdata
 */
type TransactionInstructionCtorFields = {|
  keys?: Array<PublicKey>;
  programId?: PublicKey;
  userdata?: Buffer;
|};


/**
 * Transaction Instruction class
 */
export class TransactionInstruction {
  /**
   * Public keys to include in this transaction
   */
  keys: Array<PublicKey> = [];

  /**
   * Program Id to execute
   */
  programId: PublicKey;

  /**
   * Program input
   */
  userdata: Buffer = Buffer.alloc(0);

  constructor(opts?: TransactionInstructionCtorFields) {
    opts && Object.assign(this, opts);
  }
}


/**
 * List of Transaction object fields that may be initialized at construction
 *
 * @typedef {Object} TransactionCtorFields
 * @property {?Buffer} signature
 * @property {?Array<PublicKey>} keys
 * @property {?PublicKey} programId
 * @property {?number} fee
 * @property {?Buffer} userdata
 */
type TransactionCtorFields = {|
  fee?: number;
|};

/**
 * Transaction class
 */
export class Transaction {

  /**
   * Current signature of the transaction.  Typically created by invoking the
   * `sign()` method
   */
  signature: ?Buffer;


  /**
   * The instructions to atomically execute
   */
  instructions: Array<TransactionInstruction> = [];

  /**
   * A recent transaction id.  Must be populated by the caller
   */
  lastId: ?TransactionId;

  /**
   * Fee for this transaction
   */
  fee: number = 0;

  /**
   * Construct an empty Transaction
   */
  constructor(opts?: TransactionCtorFields) {
    opts && Object.assign(this, opts);
  }

  /**
   * Add instructions to this Transaction
   */
  add(item: Transaction | TransactionInstructionCtorFields): Transaction {
    if (item instanceof Transaction) {
      this.instructions = this.instructions.concat(item.instructions);
    } else {
      this.instructions.push(new TransactionInstruction(item));
    }
    return this;
  }

  /**
   * @private
   */
  _getSignData(): Buffer {
    const {lastId} = this;
    if (!lastId) {
      throw new Error('Transaction lastId required');
    }

    if (this.instructions.length < 1) {
      throw new Error('No instructions provided');
    }

    const keys = [];
    const programIds = [];
    this.instructions.forEach(instruction => {
      const programId = instruction.programId.toString();
      if (!programIds.includes(programId)) {
        programIds.push(programId);
      }

      instruction.keys
      .map(key => key.toString())
      .forEach(key => {
        if (!keys.includes(key)) {
          keys.push(key);
        }
      });
    });

    const instructions = this.instructions.map(instruction => {
      const {userdata, programId} = instruction;
      return {
        programIdIndex: programIds.indexOf(programId.toString()),
        keyIndices: instruction.keys.map(key => keys.indexOf(key.toString())),
        userdata,
      };
    });

    instructions.forEach(instruction => {
      assert(instruction.programIdIndex >= 0);
      instruction.keyIndices.forEach(keyIndex => assert(keyIndex >= 0));
    });

    const instructionLayout = BufferLayout.struct([
      BufferLayout.u8('programIdIndex'),

      BufferLayout.u32('keyIndicesLength'),
      BufferLayout.u32('keyIndicesLengthPadding'),
      BufferLayout.seq(
        BufferLayout.u8('keyIndex'),
        BufferLayout.offset(BufferLayout.u32(), -8),
        'keyIndices'
      ),
      BufferLayout.u32('userdataLength'),
      BufferLayout.u32('userdataLengthPadding'),
      BufferLayout.seq(
        BufferLayout.u8('userdatum'),
        BufferLayout.offset(BufferLayout.u32(), -8),
        'userdata'
      ),
    ]);

    const signDataLayout = BufferLayout.struct([
      BufferLayout.u32('keysLength'),
      BufferLayout.u32('keysLengthPadding'),
      BufferLayout.seq(
        Layout.publicKey('key'),
        BufferLayout.offset(BufferLayout.u32(), -8),
        'keys'
      ),
      Layout.publicKey('lastId'),
      BufferLayout.ns64('fee'),

      BufferLayout.u32('programIdsLength'),
      BufferLayout.u32('programIdsLengthPadding'),
      BufferLayout.seq(
        Layout.publicKey('programId'),
        BufferLayout.offset(BufferLayout.u32(), -8),
        'programIds'
      ),

      BufferLayout.u32('instructionsLength'),
      BufferLayout.u32('instructionsLengthPadding'),
      BufferLayout.seq(
        instructionLayout,
        BufferLayout.offset(BufferLayout.u32(), -8),
        'instructions'
      ),
    ]);

    const transaction = {
      keys: keys.map((key) => (new PublicKey(key)).toBuffer()),
      lastId: Buffer.from(bs58.decode(lastId)),
      fee: this.fee,
      programIds: programIds.map(programId => (new PublicKey(programId)).toBuffer()),
      instructions,
    };

    let signData = Buffer.alloc(2048);
    const length = signDataLayout.encode(transaction, signData);
    signData = signData.slice(0, length);

    return signData;
  }

  /**
   * Sign the Transaction with the specified account
   *
   * The Transaction must be assigned a valid `lastId` before invoking this method
   */
  sign(from: Account) {
    const signData = this._getSignData();
    this.signature = nacl.sign.detached(signData, from.secretKey);
    assert(this.signature.length === 64);
  }

  /**
   * Serialize the Transaction in the wire format.
   *
   * The Transaction must have a valid `signature` before invoking this method
   */
  serialize(): Buffer {
    const {signature} = this;
    if (!signature) {
      throw new Error('Transaction has not been signed');
    }

    const signData = this._getSignData();
    const wireTransaction = Buffer.alloc(
      signature.length + signData.length
    );

    Buffer.from(signature).copy(wireTransaction, 0);
    signData.copy(wireTransaction, signature.length);
    return wireTransaction;
  }

  /**
   * Deprecated method
   * @private
   */
  get keys(): Array<PublicKey> {
    assert(this.instructions.length === 1);
    return this.instructions[0].keys;
  }

  /**
   * Deprecated method
   * @private
   */
  get programId(): PublicKey {
    assert(this.instructions.length === 1);
    return this.instructions[0].programId;
  }

  /**
   * Deprecated method
   * @private
   */
  get userdata(): Buffer {
    assert(this.instructions.length === 1);
    return this.instructions[0].userdata;
  }

}