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use std::ops::{Add, Sub};

use ex3_blockchain_public_types::BlockHead;
use rs_merkle::algorithms::Sha256;
use rs_merkle::MerkleTree;
use serde::{Deserialize, Serialize};
use serde_bytes::ByteBuf;

use ex3_crypto::sha256;
use ex3_error::OtherError;
use ex3_serde::bincode::{deserialize, serialize};

use crate::transaction::EncodedTransaction;
use crate::{AssetAmount, AssetId, BlockHeight, WalletRegisterId};

pub type MerkleRoot = [u8; 32];
pub type MerkleNode = [u8; 32];
pub type BlockHash = [u8; 32];

#[derive(Clone, Debug, PartialEq, Eq)]
pub struct BlockHeadExt {
    pub height: BlockHeight,
    pub validate_on_chain: bool,
    pub sharding_reported: bool,
    pub has_local_body: bool,
    pub snapshot_effected: bool,
}

impl BlockHeadExt {
    pub fn encode(&self) -> Vec<u8> {
        serialize(&(
            &self.validate_on_chain,
            &self.sharding_reported,
            &self.has_local_body,
            &self.snapshot_effected,
            &self.height,
        ))
        .unwrap()
    }

    pub fn decode(bytes: &[u8]) -> Result<Self, OtherError> {
        let (validate_on_chain, has_been_reported, has_local_body, has_been_effected, height) =
            deserialize(bytes).map_err(|e| OtherError::new(format!("{:?}", e)))?;
        Ok(Self {
            validate_on_chain,
            sharding_reported: has_been_reported,
            has_local_body,
            snapshot_effected: has_been_effected,
            height,
        })
    }
}

impl TryFrom<&[u8]> for BlockHeadExt {
    type Error = OtherError;

    fn try_from(bytes: &[u8]) -> Result<Self, Self::Error> {
        Self::decode(bytes)
    }
}

#[derive(Debug, Clone, PartialEq, Eq)]
pub struct Block {
    pub head: BlockHead,
    pub body: Option<BlockBody>,
}

impl Block {
    pub fn is_body_valid(&self) -> bool {
        if let Some(body) = &self.body {
            let tx_root = &body.tx_merkle_root();
            let balance_changed_root = &body.balances_changed_merkle_root();
            &self.head.tx_root == tx_root && &self.head.balance_changed_root == balance_changed_root
        } else {
            false
        }
    }
}

#[derive(Debug, Clone, PartialEq, Eq)]
pub struct BlockBody {
    pub txs: Vec<EncodedTransaction>,
    pub balances_changed: Vec<(WalletRegisterId, Vec<(AssetId, AmountChange)>)>,
}

impl BlockBody {
    pub fn encode(&self) -> Vec<u8> {
        serialize(&(&self.txs, &self.balances_changed)).unwrap()
    }

    pub fn tx_merkle_root(&self) -> MerkleRoot {
        self.build_tx_merkle_tree().root().unwrap()
    }

    pub fn build_tx_merkle_tree(&self) -> MerkleTree<Sha256> {
        let nodes: Vec<MerkleNode> = self
            .txs
            .iter()
            .map(|tx| sha256!(serialize(&tx).unwrap()))
            .collect();

        MerkleTree::<Sha256>::from_leaves(&nodes)
    }

    pub fn balances_changed_merkle_root(&self) -> MerkleRoot {
        self.build_balances_changed_merkle_tree().root().unwrap()
    }

    pub fn build_balances_changed_merkle_tree(&self) -> MerkleTree<Sha256> {
        let nodes: Vec<MerkleNode> = self
            .balances_changed
            .iter()
            .map(|(wallet_id, assets_change)| {
                let bytes = serialize(&(wallet_id, assets_change)).unwrap();
                sha256!(&bytes)
            })
            .collect();
        MerkleTree::<Sha256>::from_leaves(&nodes)
    }
}

impl TryFrom<&[u8]> for BlockBody {
    type Error = OtherError;

    fn try_from(bytes: &[u8]) -> Result<Self, Self::Error> {
        let (txs, balances_changed) =
            deserialize(bytes).map_err(|e| OtherError::new(format!("{:?}", e)))?;
        Ok(Self {
            txs,
            balances_changed,
        })
    }
}

#[derive(Deserialize, Serialize, Debug, Clone, PartialEq, Eq)]
pub struct EncodedBlockBody(pub ByteBuf);

impl From<BlockBody> for EncodedBlockBody {
    fn from(body: BlockBody) -> Self {
        let bytes = serialize(&body.encode()).unwrap();
        EncodedBlockBody(ByteBuf::from(bytes))
    }
}

impl From<EncodedBlockBody> for BlockBody {
    fn from(encoded_body: EncodedBlockBody) -> Self {
        encoded_body.0.as_slice().try_into().unwrap()
    }
}

#[derive(Deserialize, Serialize, Debug, Clone, PartialEq, Eq)]
pub enum AmountChange {
    Increase(AssetAmount),
    Decrease(AssetAmount),
}

impl AmountChange {
    pub fn merge(&self, other: &Self) -> Self {
        match (self, other) {
            (AmountChange::Increase(a), AmountChange::Increase(b)) => {
                AmountChange::Increase(a.add(b))
            }
            (AmountChange::Decrease(a), AmountChange::Decrease(b)) => {
                AmountChange::Decrease(a.add(b))
            }
            (AmountChange::Increase(a), AmountChange::Decrease(b)) => {
                if a >= b {
                    AmountChange::Increase(a.sub(b))
                } else {
                    AmountChange::Decrease(b.sub(a))
                }
            }
            (AmountChange::Decrease(a), AmountChange::Increase(b)) => {
                if a >= b {
                    AmountChange::Decrease(a.sub(b))
                } else {
                    AmountChange::Increase(b.sub(a))
                }
            }
        }
    }
}