One Program, Many Instructions

use anchor_lang::prelude::*;

declare_id!("MyD3F1ProgramAddressHere11111111111111111111");

#[program]
pub mod my_defi {
    use super::*;

    pub fn initialize_pool(ctx: Context<InitPool>) -> Result<()> { /* ... */ Ok(()) }
    pub fn deposit(ctx: Context<Deposit>, amount: u64) -> Result<()> { /* ... */ Ok(()) }
    pub fn withdraw(ctx: Context<Withdraw>, shares: u64) -> Result<()> { /* ... */ Ok(()) }
    pub fn swap(ctx: Context<Swap>, amount_in: u64, min_out: u64) -> Result<()> { /* ... */ Ok(()) }
    pub fn liquidate(ctx: Context<Liquidate>) -> Result<()> { /* ... */ Ok(()) }
}

// Each instruction is dispatched by an 8-byte discriminator (sha256("global:method_name"))
// Programs are upgraded by re-uploading the binary; upgrade authority must sign.
// No proxy patterns needed — upgrade is built into the BPF loader.

#[derive(Accounts)]
pub struct InitPool<'info> { /* accounts */ }
#[derive(Accounts)]
pub struct Deposit<'info> { /* accounts */ }
// ... etc