//! This example demonstrates the use of zero copy deserialization for accounts.
//! The main noticeable benefit one achieves using zero copy is the ability
//! to create accounts larger than the size of the stack or heap, as is
//! demonstrated by the event queue in this example.

use anchor_lang::prelude::*;

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

    #[state(zero_copy)]
    pub struct Globals {
        pub authority: Pubkey,
        // The solana runtime currently restricts how much one can resize an
        // account on CPI to ~10240 bytes. State accounts are program derived
        // addresses, which means its max size is limited by this restriction
        // (i.e., this is not an Anchor specific issue).
        //
        // As a result, we only use 250 events here.
        //
        // For larger zero-copy data structures, one must use non-state anchor
        // accounts, as is demonstrated below.
        pub events: [Event; 250],
    }

    impl Globals {
        // Note that the `new` constructor is different from non-zero-copy
        // state accounts. Namely, it takes in a `&mut self` parameter.
        pub fn new(&mut self, ctx: Context<New>) -> ProgramResult {
            self.authority = *ctx.accounts.authority.key;
            Ok(())
        }

        #[access_control(auth(&self, &ctx))]
        pub fn set_event(
            &mut self,
            ctx: Context<SetEvent>,
            idx: u32,
            event: RpcEvent,
        ) -> ProgramResult {
            self.events[idx as usize] = event.into();
            Ok(())
        }
    }

    pub fn create_foo(ctx: Context<CreateFoo>) -> ProgramResult {
        let foo = &mut ctx.accounts.foo.load_init()?;
        foo.authority = *ctx.accounts.authority.key;
        foo.set_second_authority(ctx.accounts.authority.key);
        Ok(())
    }

    pub fn update_foo(ctx: Context<UpdateFoo>, data: u64) -> ProgramResult {
        let mut foo = ctx.accounts.foo.load_mut()?;
        foo.data = data;
        Ok(())
    }

    pub fn update_foo_second(ctx: Context<UpdateFooSecond>, second_data: u64) -> ProgramResult {
        let mut foo = ctx.accounts.foo.load_mut()?;
        foo.second_data = second_data;
        Ok(())
    }

    pub fn create_bar(ctx: Context<CreateBar>) -> ProgramResult {
        let bar = &mut ctx.accounts.bar.load_init()?;
        bar.authority = *ctx.accounts.authority.key;
        Ok(())
    }

    pub fn update_bar(ctx: Context<UpdateBar>, data: u64) -> ProgramResult {
        let bar = &mut ctx.accounts.bar.load_mut()?;
        bar.data = data;
        Ok(())
    }

    pub fn create_large_account(_ctx: Context<CreateLargeAccount>) -> ProgramResult {
        Ok(())
    }

    pub fn update_large_account(
        ctx: Context<UpdateLargeAccount>,
        idx: u32,
        data: u64,
    ) -> ProgramResult {
        let event_q = &mut ctx.accounts.event_q.load_mut()?;
        event_q.events[idx as usize] = Event {
            data,
            from: *ctx.accounts.from.key,
        };
        Ok(())
    }
}

#[derive(Accounts)]
pub struct New<'info> {
    #[account(signer)]
    authority: AccountInfo<'info>,
}

#[derive(Accounts)]
pub struct SetEvent<'info> {
    #[account(signer)]
    authority: AccountInfo<'info>,
}

#[derive(Accounts)]
pub struct CreateFoo<'info> {
    #[account(init)]
    foo: Loader<'info, Foo>,
    #[account(signer)]
    authority: AccountInfo<'info>,
    rent: Sysvar<'info, Rent>,
}

#[derive(Accounts)]
pub struct UpdateFoo<'info> {
    #[account(mut, has_one = authority)]
    foo: Loader<'info, Foo>,
    #[account(signer)]
    authority: AccountInfo<'info>,
}

#[derive(Accounts)]
pub struct UpdateFooSecond<'info> {
    #[account(mut, "&foo.load()?.get_second_authority() == second_authority.key")]
    foo: Loader<'info, Foo>,
    #[account(signer)]
    second_authority: AccountInfo<'info>,
}

#[derive(Accounts)]
pub struct CreateBar<'info> {
    #[account(init, associated = authority, with = foo)]
    bar: Loader<'info, Bar>,
    #[account(signer)]
    authority: AccountInfo<'info>,
    foo: Loader<'info, Foo>,
    rent: Sysvar<'info, Rent>,
    system_program: AccountInfo<'info>,
}

#[derive(Accounts)]
pub struct UpdateBar<'info> {
    #[account(mut, associated = authority, with = foo, has_one = authority)]
    bar: Loader<'info, Bar>,
    #[account(signer)]
    authority: AccountInfo<'info>,
    foo: Loader<'info, Foo>,
}

#[derive(Accounts)]
pub struct CreateLargeAccount<'info> {
    #[account(init)]
    event_q: Loader<'info, EventQ>,
    rent: Sysvar<'info, Rent>,
}

#[derive(Accounts)]
pub struct UpdateLargeAccount<'info> {
    #[account(mut)]
    event_q: Loader<'info, EventQ>,
    #[account(signer)]
    from: AccountInfo<'info>,
}

#[account(zero_copy)]
pub struct Foo {
    pub authority: Pubkey,
    pub data: u64,
    pub second_data: u64,
    #[accessor(Pubkey)] // The `accessor` api will likely be removed.
    pub second_authority: [u8; 32],
}

#[associated(zero_copy)]
#[derive(Default)]
pub struct Bar {
    pub authority: Pubkey,
    pub data: u64,
}

#[account(zero_copy)]
pub struct EventQ {
    pub events: [Event; 25000],
}

#[zero_copy]
pub struct Event {
    pub from: Pubkey,
    pub data: u64,
}

// A separate type is used for the RPC interface for two main reasons.
//
// 1. AnchorSerialize and AnchorDeserialize must be derived. Anchor requires
//    *all* instructions to implement the AnchorSerialize and AnchorDeserialize
//    traits, so any types in method signatures must as well.
// 2. All types for zero copy deserialization are `#[repr(packed)]`. However,
//    the implementation of AnchorSerialize (i.e. borsh), uses references
//    to the fields it serializes. So if we were to just throw tehse derives
//    onto the other `Event` struct, we would have references to
//    `#[repr(packed)]` fields, which is unsafe. To avoid the unsafeness, we
//    just use a separate type.
#[derive(AnchorSerialize, AnchorDeserialize)]
pub struct RpcEvent {
    pub from: Pubkey,
    pub data: u64,
}

impl From<RpcEvent> for Event {
    fn from(e: RpcEvent) -> Event {
        Event {
            from: e.from,
            data: e.data,
        }
    }
}

fn auth(globals: &Globals, ctx: &Context<SetEvent>) -> ProgramResult {
    if &globals.authority != ctx.accounts.authority.key {
        return Err(ProgramError::Custom(1)); // Arbitrary error.
    }
    Ok(())
}