solana-program-examples/basics/close-account/native/ts/instructions/close.ts

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


export class Close {

    instruction: MyInstruction;

    constructor(props: {
        instruction: MyInstruction,
    }) {
        this.instruction = props.instruction;
    }

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

export const CloseSchema = new Map([
    [ Close, { 
        kind: 'struct', 
        fields: [ 
            ['instruction', 'u8'],
        ],
    }]
]);

export function createCloseUserInstruction(
    target: PublicKey,
    payer: PublicKey,
    programId: PublicKey,
): TransactionInstruction {

    const instructionObject = new Close({
        instruction: MyInstruction.CloseUser,
    });

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

    return ix;
}