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use {
    crate::objects::*,
    anchor_lang::{prelude::*, solana_program::system_program},
    anchor_spl::{associated_token::get_associated_token_address, token::TokenAccount},
    clockwork_utils::{anchor_sighash, AccountMetaData, CrankResponse, InstructionData},
    std::mem::size_of,
};

#[derive(Accounts)]
pub struct SnapshotEntryCreate<'info> {
    #[account(address = Config::pubkey())]
    pub config: Account<'info, Config>,

    #[account(
        address = delegation.pubkey(),
        constraint = delegation.id.eq(&snapshot_frame.total_entries),
        has_one = worker,
    )]
    pub delegation: Box<Account<'info, Delegation>>,

    #[account(
        associated_token::authority = delegation,
        associated_token::mint = config.mint,
    )]
    pub delegation_stake: Account<'info, TokenAccount>,

    #[account(mut)]
    pub payer: Signer<'info>,

    #[account(address = config.epoch_queue)]
    pub queue: Signer<'info>,

    #[account(
        address = Registry::pubkey(),
        constraint = registry.locked
    )]
    pub registry: Box<Account<'info, Registry>>,

    #[account(
        address = snapshot.pubkey(),
        constraint = registry.current_epoch.checked_add(1).unwrap().eq(&snapshot.id)
    )]
    pub snapshot: Box<Account<'info, Snapshot>>,

    #[account(
        init,
        seeds = [
            SEED_SNAPSHOT_ENTRY,
            snapshot_frame.key().as_ref(),
            snapshot_frame.total_entries.to_be_bytes().as_ref(),
        ],
        bump,
        payer = payer,
        space = 8 + size_of::<SnapshotEntry>(),
    )]
    pub snapshot_entry: Account<'info, SnapshotEntry>,

    #[account(
        mut,
        seeds = [
            SEED_SNAPSHOT_FRAME,
            snapshot_frame.snapshot.as_ref(),
            snapshot_frame.id.to_be_bytes().as_ref(),
        ],
        bump,
        has_one = snapshot,
        constraint = snapshot_frame.id.checked_add(1).unwrap().eq(&snapshot.total_frames),
    )]
    pub snapshot_frame: Box<Account<'info, SnapshotFrame>>,

    #[account(address = system_program::ID)]
    pub system_program: Program<'info, System>,

    #[account(
        address = worker.pubkey(),
        constraint = worker.id.eq(&snapshot_frame.id),
    )]
    pub worker: Box<Account<'info, Worker>>,
}

pub fn handler(ctx: Context<SnapshotEntryCreate>) -> Result<CrankResponse> {
    // Get accounts.
    let config = &ctx.accounts.config;
    let delegation = &ctx.accounts.delegation;
    let delegation_stake = &ctx.accounts.delegation_stake;
    let payer = &ctx.accounts.payer;
    let queue = &ctx.accounts.queue;
    let registry = &ctx.accounts.registry;
    let snapshot = &mut ctx.accounts.snapshot;
    let snapshot_entry = &mut ctx.accounts.snapshot_entry;
    let snapshot_frame = &mut ctx.accounts.snapshot_frame;
    let system_program = &ctx.accounts.system_program;
    let worker = &ctx.accounts.worker;

    // Initialize snapshot entry account.
    snapshot_entry.init(
        delegation.key(),
        snapshot_frame.total_entries,
        snapshot_frame.key(),
        delegation_stake.amount,
    )?;

    // Update the snapshot frame.
    snapshot_frame.total_entries = snapshot_frame.total_entries.checked_add(1).unwrap();

    // Build the next instruction for the queue.
    let next_instruction = if snapshot_frame.total_entries.lt(&worker.total_delegations) {
        // Create a snapshot entry for the next delegation.
        let next_delegation_pubkey =
            Delegation::pubkey(worker.pubkey(), delegation.id.checked_add(1).unwrap());
        let next_snapshot_entry_pubkey = SnapshotEntry::pubkey(
            snapshot_frame.key(),
            snapshot_entry.id.checked_add(1).unwrap(),
        );
        Some(InstructionData {
            program_id: crate::ID,
            accounts: vec![
                AccountMetaData::new_readonly(config.key(), false),
                AccountMetaData::new_readonly(next_delegation_pubkey, false),
                AccountMetaData::new_readonly(
                    get_associated_token_address(&next_delegation_pubkey, &config.mint),
                    false,
                ),
                AccountMetaData::new(payer.key(), true),
                AccountMetaData::new_readonly(queue.key(), true),
                AccountMetaData::new_readonly(registry.key(), false),
                AccountMetaData::new_readonly(snapshot.key(), false),
                AccountMetaData::new(next_snapshot_entry_pubkey, false),
                AccountMetaData::new(snapshot_frame.key(), false),
                AccountMetaData::new_readonly(system_program.key(), false),
                AccountMetaData::new_readonly(worker.key(), false),
            ],
            data: anchor_sighash("snapshot_entry_create").to_vec(),
        })
    } else if snapshot.total_frames.lt(&registry.total_workers) {
        // This frame has captured all its entries. Create a frame for the next worker.
        let next_snapshot_frame_pubkey =
            SnapshotFrame::pubkey(snapshot.key(), snapshot_frame.id.checked_add(1).unwrap());
        let next_worker_pubkey = Worker::pubkey(worker.id.checked_add(1).unwrap());
        Some(InstructionData {
            program_id: crate::ID,
            accounts: vec![
                AccountMetaData::new_readonly(config.key(), false),
                AccountMetaData::new(payer.key(), true),
                AccountMetaData::new_readonly(queue.key(), true),
                AccountMetaData::new_readonly(registry.key(), false),
                AccountMetaData::new(snapshot.key(), false),
                AccountMetaData::new(next_snapshot_frame_pubkey, false),
                AccountMetaData::new_readonly(system_program.key(), false),
                AccountMetaData::new_readonly(next_worker_pubkey, false),
                AccountMetaData::new_readonly(
                    get_associated_token_address(&next_worker_pubkey, &config.mint),
                    false,
                ),
            ],
            data: anchor_sighash("snapshot_frame_create").to_vec(),
        })
    } else {
        // All entries in this frame have been captured, and it is the last frame. The snapshot is done!
        Some(InstructionData {
            program_id: crate::ID,
            accounts: vec![
                AccountMetaData::new_readonly(config.key(), false),
                AccountMetaData::new_readonly(queue.key(), true),
                AccountMetaData::new(registry.key(), false),
            ],
            data: anchor_sighash("registry_epoch_cutover").to_vec(),
        })
    };

    Ok(CrankResponse {
        next_instruction,
        ..CrankResponse::default()
    })
}