use std::mem::size_of;

use ore_api::{consts::*, instruction::OpenArgs, loaders::*, state::Proof};
use solana_program::{
    account_info::AccountInfo,
    blake3::hashv,
    clock::Clock,
    entrypoint::ProgramResult,
    program_error::ProgramError,
    slot_hashes::SlotHash,
    system_program,
    sysvar::{self, Sysvar},
};

use crate::utils::{create_pda, AccountDeserialize, Discriminator};

/// Register generates a new hash chain for a prospective miner. Its responsibilities include:
/// 1. Initialize a new proof account.
/// 2. Generate an initial hash from the signer's key.
///
/// Safety requirements:
/// - Register is a permissionless instruction and can be invoked by any singer.
/// - Can only succeed if the provided proof acount PDA is valid (associated with the signer).
/// - Can only succeed if the user does not already have a proof account.
/// - The provided system program must be valid.
pub fn process_open<'a, 'info>(accounts: &'a [AccountInfo<'info>], data: &[u8]) -> ProgramResult {
    // Parse args
    let args = OpenArgs::try_from_bytes(data)?;

    // Load accounts
    let [signer, miner_info, payer_info, proof_info, system_program, slot_hashes_info] = accounts
    else {
        return Err(ProgramError::NotEnoughAccountKeys);
    };
    load_signer(signer)?;
    load_system_account(miner_info, false)?;
    load_signer(payer_info)?;
    load_uninitialized_pda(
        proof_info,
        &[PROOF, signer.key.as_ref()],
        args.bump,
        &ore_api::id(),
    )?;
    load_program(system_program, system_program::id())?;
    load_sysvar(slot_hashes_info, sysvar::slot_hashes::id())?;

    // Initialize proof
    create_pda(
        proof_info,
        &ore_api::id(),
        8 + size_of::<Proof>(),
        &[PROOF, signer.key.as_ref(), &[args.bump]],
        system_program,
        payer_info,
    )?;
    let clock = Clock::get().or(Err(ProgramError::InvalidAccountData))?;
    let mut proof_data = proof_info.data.borrow_mut();
    proof_data[0] = Proof::discriminator() as u8;
    let proof = Proof::try_from_bytes_mut(&mut proof_data)?;
    proof.authority = *signer.key;
    proof.balance = 0;
    proof.challenge = hashv(&[
        signer.key.as_ref(),
        &slot_hashes_info.data.borrow()[0..size_of::<SlotHash>()],
    ])
    .0;
    proof.last_hash = [0; 32];
    proof.last_hash_at = clock.unix_timestamp;
    proof.last_stake_at = clock.unix_timestamp;
    proof.miner = *miner_info.key;
    proof.total_hashes = 0;
    proof.total_rewards = 0;

    Ok(())
}