CRUD App: Create Entry

Challenge: The Create Instruction

Write the create_entry instruction. You must initialize a PDA using the author's public key and the journal title as seeds.

Dynamic Space Allocation

While we defined #[max_len(1000)] for the message, if the user only writes "Hello", allocating 1000 bytes is a waste of rent! We should only allocate the space actually needed for the string they pass in.

A string in Rust requires 4 bytes to store its length, plus 1 byte for every character.

#[derive(Accounts)]
#[instruction(title: String, message: String)]
pub struct CreateEntry<'info> {
    #[account(mut)]
    pub owner: Signer<'info>,

    #[account(
        init,
        payer = owner,
        // 8 (discriminator) + 32 (pubkey) + (4 + title.len()) + (4 + message.len())
        space = 8 + 32 + (4 + title.len()) + (4 + message.len()),
        seeds = [title.as_bytes(), owner.key().as_ref()],
        bump
    )]
    pub journal_entry: Account<'info, JournalEntryState>,
    pub system_program: Program<'info, System>,
}

Implement the logic to save the title, message, and owner to the PDA!