//! State changes that are not related to transactions.

use alloy_eips::eip4895::Withdrawal;
use alloy_primitives::{map::HashMap, Address, U256};
use reth_chainspec::EthereumHardforks;
use reth_consensus_common::calc;
use reth_primitives::{Block, Withdrawals};

/// Collect all balance changes at the end of the block.
///
/// Balance changes might include the block reward, uncle rewards, withdrawals, or irregular
/// state changes (DAO fork).
#[inline]
pub fn post_block_balance_increments<ChainSpec: EthereumHardforks>(
    chain_spec: &ChainSpec,
    block: &Block,
    total_difficulty: U256,
) -> HashMap<Address, u128> {
    let mut balance_increments = HashMap::default();

    // Add block rewards if they are enabled.
    if let Some(base_block_reward) =
        calc::base_block_reward(chain_spec, block.number, block.difficulty, total_difficulty)
    {
        // Ommer rewards
        for ommer in &block.body.ommers {
            *balance_increments.entry(ommer.beneficiary).or_default() +=
                calc::ommer_reward(base_block_reward, block.number, ommer.number);
        }

        // Full block reward
        *balance_increments.entry(block.beneficiary).or_default() +=
            calc::block_reward(base_block_reward, block.body.ommers.len());
    }

    // process withdrawals
    insert_post_block_withdrawals_balance_increments(
        chain_spec,
        block.timestamp,
        block.body.withdrawals.as_ref().map(Withdrawals::as_ref),
        &mut balance_increments,
    );

    balance_increments
}

/// Returns a map of addresses to their balance increments if the Shanghai hardfork is active at the
/// given timestamp.
///
/// Zero-valued withdrawals are filtered out.
#[inline]
pub fn post_block_withdrawals_balance_increments<ChainSpec: EthereumHardforks>(
    chain_spec: &ChainSpec,
    block_timestamp: u64,
    withdrawals: &[Withdrawal],
) -> HashMap<Address, u128> {
    let mut balance_increments =
        HashMap::with_capacity_and_hasher(withdrawals.len(), Default::default());
    insert_post_block_withdrawals_balance_increments(
        chain_spec,
        block_timestamp,
        Some(withdrawals),
        &mut balance_increments,
    );
    balance_increments
}

/// Applies all withdrawal balance increments if shanghai is active at the given timestamp to the
/// given `balance_increments` map.
///
/// Zero-valued withdrawals are filtered out.
#[inline]
pub fn insert_post_block_withdrawals_balance_increments<ChainSpec: EthereumHardforks>(
    chain_spec: &ChainSpec,
    block_timestamp: u64,
    withdrawals: Option<&[Withdrawal]>,
    balance_increments: &mut HashMap<Address, u128>,
) {
    // Process withdrawals
    if chain_spec.is_shanghai_active_at_timestamp(block_timestamp) {
        if let Some(withdrawals) = withdrawals {
            for withdrawal in withdrawals {
                if withdrawal.amount > 0 {
                    *balance_increments.entry(withdrawal.address).or_default() +=
                        withdrawal.amount_wei().to::<u128>();
                }
            }
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use alloy_consensus::constants::GWEI_TO_WEI;
    use reth_chainspec::ChainSpec;
    use reth_ethereum_forks::{ChainHardforks, EthereumHardfork, ForkCondition};

    /// Tests that the function correctly inserts balance increments when the Shanghai hardfork is
    /// active and there are withdrawals.
    #[test]
    fn test_insert_post_block_withdrawals_balance_increments_shanghai_active_with_withdrawals() {
        // Arrange
        // Create a ChainSpec with the Shanghai hardfork active at timestamp 100
        let chain_spec = ChainSpec {
            hardforks: ChainHardforks::new(vec![(
                Box::new(EthereumHardfork::Shanghai),
                ForkCondition::Timestamp(100),
            )]),
            ..Default::default()
        };

        // Define the block timestamp and withdrawals
        let block_timestamp = 1000;
        let withdrawals = vec![
            Withdrawal {
                address: Address::from([1; 20]),
                amount: 1000,
                index: 45,
                validator_index: 12,
            },
            Withdrawal {
                address: Address::from([2; 20]),
                amount: 500,
                index: 412,
                validator_index: 123,
            },
        ];

        // Create an empty HashMap to hold the balance increments
        let mut balance_increments = HashMap::default();

        // Act
        // Call the function with the prepared inputs
        insert_post_block_withdrawals_balance_increments(
            &chain_spec,
            block_timestamp,
            Some(&withdrawals),
            &mut balance_increments,
        );

        // Assert
        // Verify that the balance increments map has the correct number of entries
        assert_eq!(balance_increments.len(), 2);
        // Verify that the balance increments map contains the correct values for each address
        assert_eq!(
            *balance_increments.get(&Address::from([1; 20])).unwrap(),
            (1000 * GWEI_TO_WEI).into()
        );
        assert_eq!(
            *balance_increments.get(&Address::from([2; 20])).unwrap(),
            (500 * GWEI_TO_WEI).into()
        );
    }

    /// Tests that the function correctly handles the case when Shanghai is active but there are no
    /// withdrawals.
    #[test]
    fn test_insert_post_block_withdrawals_balance_increments_shanghai_active_no_withdrawals() {
        // Arrange
        // Create a ChainSpec with the Shanghai hardfork active
        let chain_spec = ChainSpec {
            hardforks: ChainHardforks::new(vec![(
                Box::new(EthereumHardfork::Shanghai),
                ForkCondition::Timestamp(100),
            )]),
            ..Default::default()
        };

        // Define the block timestamp and an empty list of withdrawals
        let block_timestamp = 1000;
        let withdrawals = Vec::<Withdrawal>::new();

        // Create an empty HashMap to hold the balance increments
        let mut balance_increments = HashMap::default();

        // Act
        // Call the function with the prepared inputs
        insert_post_block_withdrawals_balance_increments(
            &chain_spec,
            block_timestamp,
            Some(&withdrawals),
            &mut balance_increments,
        );

        // Assert
        // Verify that the balance increments map is empty
        assert!(balance_increments.is_empty());
    }

    /// Tests that the function correctly handles the case when Shanghai is not active even if there
    /// are withdrawals.
    #[test]
    fn test_insert_post_block_withdrawals_balance_increments_shanghai_not_active_with_withdrawals()
    {
        // Arrange
        // Create a ChainSpec without the Shanghai hardfork active
        let chain_spec = ChainSpec::default(); // Mock chain spec with Shanghai not active

        // Define the block timestamp and withdrawals
        let block_timestamp = 1000;
        let withdrawals = vec![
            Withdrawal {
                address: Address::from([1; 20]),
                amount: 1000,
                index: 45,
                validator_index: 12,
            },
            Withdrawal {
                address: Address::from([2; 20]),
                amount: 500,
                index: 412,
                validator_index: 123,
            },
        ];

        // Create an empty HashMap to hold the balance increments
        let mut balance_increments = HashMap::default();

        // Act
        // Call the function with the prepared inputs
        insert_post_block_withdrawals_balance_increments(
            &chain_spec,
            block_timestamp,
            Some(&withdrawals),
            &mut balance_increments,
        );

        // Assert
        // Verify that the balance increments map is empty
        assert!(balance_increments.is_empty());
    }

    /// Tests that the function correctly handles the case when Shanghai is active but all
    /// withdrawals have zero amounts.
    #[test]
    fn test_insert_post_block_withdrawals_balance_increments_shanghai_active_with_zero_withdrawals()
    {
        // Arrange
        // Create a ChainSpec with the Shanghai hardfork active
        let chain_spec = ChainSpec {
            hardforks: ChainHardforks::new(vec![(
                Box::new(EthereumHardfork::Shanghai),
                ForkCondition::Timestamp(100),
            )]),
            ..Default::default()
        };

        // Define the block timestamp and withdrawals with zero amounts
        let block_timestamp = 1000;
        let withdrawals = vec![
            Withdrawal {
                address: Address::from([1; 20]),
                amount: 0, // Zero withdrawal amount
                index: 45,
                validator_index: 12,
            },
            Withdrawal {
                address: Address::from([2; 20]),
                amount: 0, // Zero withdrawal amount
                index: 412,
                validator_index: 123,
            },
        ];

        // Create an empty HashMap to hold the balance increments
        let mut balance_increments = HashMap::default();

        // Act
        // Call the function with the prepared inputs
        insert_post_block_withdrawals_balance_increments(
            &chain_spec,
            block_timestamp,
            Some(&withdrawals),
            &mut balance_increments,
        );

        // Assert
        // Verify that the balance increments map is empty
        assert!(balance_increments.is_empty());
    }

    /// Tests that the function correctly handles the case when Shanghai is active but there are no
    /// withdrawals provided.
    #[test]
    fn test_insert_post_block_withdrawals_balance_increments_shanghai_active_with_empty_withdrawals(
    ) {
        // Arrange
        // Create a ChainSpec with the Shanghai hardfork active
        let chain_spec = ChainSpec {
            hardforks: ChainHardforks::new(vec![(
                Box::new(EthereumHardfork::Shanghai),
                ForkCondition::Timestamp(100),
            )]),
            ..Default::default()
        };

        // Define the block timestamp and no withdrawals
        let block_timestamp = 1000;
        let withdrawals = None; // No withdrawals provided

        // Create an empty HashMap to hold the balance increments
        let mut balance_increments = HashMap::default();

        // Act
        // Call the function with the prepared inputs
        insert_post_block_withdrawals_balance_increments(
            &chain_spec,
            block_timestamp,
            withdrawals,
            &mut balance_increments,
        );

        // Assert
        // Verify that the balance increments map is empty
        assert!(balance_increments.is_empty());
    }
}