Solana-AI-platform

    }     pub fn rent_model(ctx: Context<RentModel>) -> Result<()> {        let model = &mut ctx.accounts.model;        require!(model.is_available, ErrorCode::ModelNotAvailable);         let renter = &ctx.accounts.renter;        let uploader = &ctx.accounts.uploader;         // Transfer SOL from renter -> uploader (CPI to system program)        let ix = system_instruction::transfer(&renter.key(), &uploader.key(), model.price_lamports);        invoke(            &ix,            &[                renter.to_account_info(),                uploader.to_account_info(),                ctx.accounts.system_program.to_account_info(),            ],        )?;         model.times_rented = model.times_rented.checked_add(1).ok_or(ErrorCode::MathOverflow)?;        let now = Clock::get()?.unix_timestamp;        emit!(ModelRented {            model: model.key(),

1. Line 41 require!(model.is_available, ErrorCode::ModelNotAvailable);: An explicit validation that aborts the instruction with an error.
2. Line 48 invoke(: Makes a cross-program invocation into another program.
3. Line 57 model.times_rented = model.times_rented.checked_add(1).ok_or(ErrorCode::MathOverflow)?;: Uses checked arithmetic so overflow fails instead of wrapping.
4. Line 58 let now = Clock::get()?.unix_timestamp;: Reads on-chain time from the Clock sysvar.
5. Line 59 emit!(ModelRented {: Emits an Anchor event that clients can parse from the logs.

    const programPubkey = new PublicKey(programId);    const connection = new Connection(rpcUrl, "confirmed");    const wallet = new anchor.Wallet(keypair);    const provider = new anchor.AnchorProvider(connection, wallet, anchor.AnchorProvider.defaultOptions());    anchor.setProvider(provider);     const program = new anchor.Program(idl, programPubkey, provider);     // derive PDA: seeds = ["model", model_hash_bytes]    const seedBytes = Buffer.from(modelHashHex, "hex");    if (seedBytes.length !== 32) {      exitJSON({ success: false, error: "model_hash_hex must be 32 bytes (64 hex chars)" }, 1);    }    const [modelPda] = await PublicKey.findProgramAddress([Buffer.from("model"), seedBytes], program.programId);     // fetch model account to ensure exists and get uploader pubkey    let modelAccount;    try {      modelAccount = await program.account.model.fetch(modelPda);    } catch (e) {      exitJSON({ success: false, error: "Model account not found on-chain for given hash", details: e.message || String(e) }, 1);    }     // uploader pubkey depends on your account layout; we expect a pubkey field named `uploader`

1. Line 129 // derive PDA: seeds = ["model", model_hash_bytes]: Declares the PDA seeds. Anchor re-derives the address and rejects the account if it doesn't match.
2. Line 134 const [modelPda] = await PublicKey.findProgramAddress([Buffer.from("model"), seedBytes], p: Derives a PDA from seeds and the program ID and returns the address with its canonical bump.