solana-program-examples/tokens/transfer-tokens/native/program/src/instructions/mint_spl.rs

use {
    borsh::{ 
        BorshDeserialize, 
        BorshSerialize, 
    },
    solana_program::{
        account_info::{next_account_info, AccountInfo},
        entrypoint::ProgramResult, 
        msg, 
        program::invoke,
    },
    spl_token::{
        instruction as token_instruction,
    },
    spl_associated_token_account::{
        instruction as associated_token_account_instruction,
    },
};


#[derive(BorshSerialize, BorshDeserialize, Debug)]
pub struct MintSplArgs {
    pub quantity: u64,
}


pub fn mint_spl(
    accounts: &[AccountInfo],
    args: MintSplArgs,
) -> ProgramResult {

    let accounts_iter = &mut accounts.iter();

    let mint_account = next_account_info(accounts_iter)?;
    let mint_authority = next_account_info(accounts_iter)?;
    let associated_token_account = next_account_info(accounts_iter)?;
    let payer = next_account_info(accounts_iter)?;
    let system_program = next_account_info(accounts_iter)?;
    let token_program = next_account_info(accounts_iter)?;
    let associated_token_program = next_account_info(accounts_iter)?;

    if associated_token_account.lamports() == 0 {
        msg!("Creating associated token account...");
        invoke(
            &associated_token_account_instruction::create_associated_token_account(
                &payer.key,
                &payer.key,
                &mint_account.key,
            ),
            &[
                mint_account.clone(),
                associated_token_account.clone(),
                payer.clone(),
                system_program.clone(),
                token_program.clone(),
                associated_token_program.clone(),
            ]
        )?;
    } else {
        msg!("Associated token account exists.");
    }
    msg!("Associated Token Address: {}", associated_token_account.key);

    msg!("Minting {} tokens to associated token account...", args.quantity);
    invoke(
        &token_instruction::mint_to(
            &token_program.key,
            &mint_account.key,
            &associated_token_account.key,
            &mint_authority.key,
            &[&mint_authority.key],
            args.quantity,
        )?,
        &[
            mint_account.clone(),
            mint_authority.clone(),
            associated_token_account.clone(),
            token_program.clone(),
        ],
    )?;

    msg!("Tokens minted to wallet successfully.");

    Ok(())
}