use std::mem::size_of;

use drillx::Solution;
use ore_api::{
    consts::*,
    error::OreError,
    event::MineEvent,
    instruction::MineArgs,
    loaders::*,
    state::{Bus, Config, Proof},
};
use solana_program::program::set_return_data;
#[allow(deprecated)]
use solana_program::{
    account_info::AccountInfo,
    blake3::hashv,
    clock::Clock,
    entrypoint::ProgramResult,
    log::sol_log,
    program_error::ProgramError,
    pubkey::Pubkey,
    slot_hashes::SlotHash,
    sysvar::{self, Sysvar},
};

use crate::{authenticate, utils::AccountDeserialize};

/// Mine is the primary workhorse instruction of the Ore program. Its responsibilities include:
/// 1. Calculate the hash from the provided nonce.
/// 2. Payout rewards based on difficulty, staking multiplier, and liveness penalty.
/// 3. Generate a new challenge for the miner.
/// 4. Update the miner's lifetime stats.
///
/// Safety requirements:
/// - Mine is a permissionless instruction and can be called by any signer.
/// - Can only succeed if mining is not paused.
/// - Can only succeed if the last reset was less than 60 seconds ago.
/// - Can only succeed if the provided hash satisfies the minimum difficulty requirement.
/// - Can only succeed if the miners proof pubkey matches the declared proof pubkey.
/// - The provided proof account must be associated with the signer.
/// - The provided bus, config, noise, stake, and slot hash sysvar must be valid.
pub fn process_mine<'a, 'info>(
    _program_id: &Pubkey,
    accounts: &'a [AccountInfo<'info>],
    data: &[u8],
) -> ProgramResult {
    // Parse args
    let args = MineArgs::try_from_bytes(data)?;

    // Load accounts
    let [signer, bus_info, config_info, proof_info, instructions_sysvar, slot_hashes_sysvar] =
        accounts
    else {
        return Err(ProgramError::NotEnoughAccountKeys);
    };
    load_signer(signer)?;
    load_any_bus(bus_info, true)?;
    load_config(config_info, false)?;
    load_proof_with_miner(proof_info, signer.key, true)?;
    load_sysvar(instructions_sysvar, sysvar::instructions::id())?;
    load_sysvar(slot_hashes_sysvar, sysvar::slot_hashes::id())?;

    // Authenticate the proof account
    if let Ok(Some(auth_address)) = authenticate(&instructions_sysvar.data.borrow()) {
        if auth_address.ne(proof_info.key) {
            return Err(OreError::AuthFailed.into());
        }
    } else {
        return Err(OreError::AuthFailed.into());
    }

    // Validate epoch is active.
    let config_data = config_info.data.borrow();
    let config = Config::try_from_bytes(&config_data)?;
    let clock = Clock::get().or(Err(ProgramError::InvalidAccountData))?;
    if config
        .last_reset_at
        .saturating_add(EPOCH_DURATION)
        .le(&clock.unix_timestamp)
    {
        return Err(OreError::NeedsReset.into());
    }

    // Validate the hash digest.
    let mut proof_data = proof_info.data.borrow_mut();
    let proof = Proof::try_from_bytes_mut(&mut proof_data)?;
    let solution = Solution::new(args.digest, args.nonce);
    if !solution.is_valid(&proof.challenge) {
        return Err(OreError::HashInvalid.into());
    }

    // Reject spam transactions.
    let t: i64 = clock.unix_timestamp;
    let t_target = proof.last_hash_at.saturating_add(ONE_MINUTE);
    let t_spam = t_target.saturating_sub(TOLERANCE);
    if t.lt(&t_spam) {
        return Err(OreError::Spam.into());
    }

    // Validate hash satisfies the minimnum difficulty.
    let hash = solution.to_hash();
    let difficulty = hash.difficulty();
    if difficulty.lt(&(config.min_difficulty as u32)) {
        return Err(OreError::HashTooEasy.into());
    }

    // Normalize difficulty and calculate reward rate
    let normalized_difficulty = difficulty
        .checked_sub(config.min_difficulty as u32)
        .unwrap();
    let mut reward = config
        .base_reward_rate
        .checked_mul(2u64.checked_pow(normalized_difficulty).unwrap())
        .unwrap();
    sol_log(&format!("Diff {}", difficulty));

    // Apply staking multiplier.
    // If user has greater than or equal to the max stake on the network, they receive 2x multiplier.
    // Any stake less than this will receives between 1x and 2x multipler. The multipler is only active
    // if the miner's last stake deposit was more than one minute ago.
    let mut bus_data = bus_info.data.borrow_mut();
    let bus = Bus::try_from_bytes_mut(&mut bus_data)?;
    if proof.balance.gt(&0) && proof.last_stake_at.saturating_add(ONE_MINUTE).lt(&t) {
        // Update staking reward
        if config.top_balance.gt(&0) {
            let staking_reward = (reward as u128)
                .checked_mul(proof.balance.min(config.top_balance) as u128)
                .unwrap()
                .checked_div(config.top_balance as u128)
                .unwrap() as u64;
            reward = reward.checked_add(staking_reward).unwrap();
        }

        // Update bus stake tracker if stake is active
        if proof.balance.gt(&bus.top_balance) {
            bus.top_balance = proof.balance;
        }
    }

    // Apply liveness penalty.
    let t_liveness = t_target.saturating_add(TOLERANCE);
    if t.gt(&t_liveness) {
        reward = reward.saturating_sub(
            reward
                .checked_mul(t.checked_sub(t_liveness).unwrap() as u64)
                .unwrap()
                .checked_div(ONE_MINUTE as u64)
                .unwrap(),
        );
    }

    // Limit payout amount to whatever is left in the bus
    let reward_actual = reward.min(bus.rewards);

    // Update balances
    bus.theoretical_rewards = bus.theoretical_rewards.checked_add(reward).unwrap();
    bus.rewards = bus.rewards.checked_sub(reward_actual).unwrap();
    proof.balance = proof.balance.checked_add(reward_actual).unwrap();

    // Hash recent slot hash into the next challenge to prevent pre-mining attacks
    proof.last_hash = hash.h;
    proof.challenge = hashv(&[
        hash.h.as_slice(),
        &slot_hashes_sysvar.data.borrow()[0..size_of::<SlotHash>()],
    ])
    .0;

    // Update time trackers
    proof.last_hash_at = t.max(t_target);

    // Update lifetime stats
    proof.total_hashes = proof.total_hashes.saturating_add(1);
    proof.total_rewards = proof.total_rewards.saturating_add(reward);

    // Log the mined rewards
    set_return_data(
        MineEvent {
            difficulty: difficulty as u64,
            reward: reward_actual,
            timing: t.saturating_sub(t_liveness),
        }
        .to_bytes(),
    );

    Ok(())
}