solana-program-examples/basics/transfer-sol/native/tests/instruction.ts

import * as borsh from "borsh";
import { Buffer } from "buffer";
import { 
    PublicKey, 
    SystemProgram,
    TransactionInstruction 
} from '@solana/web3.js';


export enum InstructionType {
    CpiTransfer,
    ProgramTransfer,
}


export class TransferInstruction {

    instruction: InstructionType;
    amount: number;

    constructor(props: {
        instruction: InstructionType,
        amount: number,
    }) {
        this.instruction = props.instruction;
        this.amount = props.amount;
    }

    toBuffer() { 
        return Buffer.from(borsh.serialize(TransferInstructionSchema, this)) 
    };
    
    static fromBuffer(buffer: Buffer) {
        return borsh.deserialize(TransferInstructionSchema, TransferInstruction, buffer);
    };
};

export const TransferInstructionSchema = new Map([
    [ TransferInstruction, { 
        kind: 'struct', 
        fields: [ 
            ['instruction', 'u8'],
            ['amount', 'u64'],
        ],
    }]
]);

export function createTransferInstruction(
    payerPubkey: PublicKey,
    recipientPubkey: PublicKey,
    programId: PublicKey,
    instruction: InstructionType,
    amount: number,
): TransactionInstruction {

    const instructionObject = new TransferInstruction({
        instruction,
        amount,
    });

    const ix = new TransactionInstruction({
        keys: [
            {pubkey: payerPubkey, isSigner: true, isWritable: true},
            {pubkey: recipientPubkey, isSigner: false, isWritable: true},
            {pubkey: SystemProgram.programId, isSigner: false, isWritable: false}
        ],
        programId,
        data: instructionObject.toBuffer(),
    });

    return ix;
}