//! A partial chain is a chain that only contains a subset of the blocks in the
//! full chain. We use multiple partial chains to sync up with the full chain,
//! and then merge them together to get the full chain. This allows us to make
//! Initial Block Download in parallel.
//!
//! We use a [PartialChainState] insted of the useal ChainState, mainly for
//! performance. Because we assume that only one worker will hold a [PartialChainState]
//! at a given time, we can drop all syncronization primitives and make a really performatic
//! ChainState that will consume and validate blocks as fast as we possibly can.
//!
//! This choice removes the use of costly atomic operations, but opens space for design flaws
//! and memory unsoundness, so here are some tips about this module and how people looking for
//! extend or use this code should proceed:
//!   
//!   - Shared ownership is forbidden: if you have two threads or tasks owning this, you'll have
//!     data race. If you want to hold shared ownership for this module, you need to place a
//!     [PartialChainState] inside an `Arc<Mutex>` yourself. Don't just Arc this and expect it to
//!     work, as you are garanteed to have data races.
//!   - The interior is toxic, so no peeking: no references, mutable or not, to any field should
//!     leak through the API, as we are not enforcing lifetime or borrowing rules at compile time.
//!   - Sending is fine: There's nothing in this module that makes it not sendable to between
//!     threads, as long as the origin thread gives away the ownership.
use bitcoin::BlockHash;
use floresta_common::prelude::*;
extern crate alloc;

use core::cell::UnsafeCell;
#[cfg(feature = "bitcoinconsensus")]
use core::ffi::c_uint;

#[cfg(feature = "bitcoinconsensus")]
use bitcoin::bitcoinconsensus;
use bitcoin::block::Header as BlockHeader;
use log::info;
use rustreexo::accumulator::stump::Stump;

use super::chainparams::ChainParams;
use super::consensus::Consensus;
use super::error::BlockValidationErrors;
use super::error::BlockchainError;
use super::BlockchainInterface;
use super::UpdatableChainstate;
use crate::UtreexoBlock;

#[doc(hidden)]
#[derive(Debug)]
pub(crate) struct PartialChainStateInner {
    /// The current accumulator state, it starts with a hardcoded value and
    /// gets checked against the result of the previous partial chainstate.
    pub(crate) current_acc: Stump,
    /// The block headers in this interval, we need this to verify the blocks
    /// and to build the accumulator. We assume this is sorted by height, and
    /// should contains all blocks in this interval.
    pub(crate) blocks: Vec<BlockHeader>,
    /// The height this interval starts at. This [initial_height, final_height), so
    /// if we break the interval at height 100, the first interval will be [0, 100)
    /// and the second interval will be [100, 200). And the initial height of the
    /// second interval will be 99.
    pub(crate) initial_height: u32,
    /// The height we are on right now, this is used to keep track of the progress
    /// of the sync.
    pub(crate) current_height: u32,
    /// The height we are syncing up to, trying to push more blocks than this will
    /// result in an error.
    pub(crate) final_height: u32,
    /// The error that occurred during validation, if any. It is here so we can
    /// pull that afterwords.
    pub(crate) error: Option<BlockValidationErrors>,
    /// The consensus parameters, we need this to validate the blocks.
    pub(crate) consensus: Consensus,
    /// Whether we assume the signatures in this interval as valid, this is used to
    /// speed up syncing, by assuming signatures in old blocks are valid.
    pub(crate) assume_valid: bool,
}

/// A partial chain is a chain that only contains a subset of the blocks in the
/// full chain. We use multiple partial chains to sync up with the full chain,
/// and then merge them together to get the full chain. This allows us to conduct
/// the sync in parallel. To build one, we need to know the initial
/// height, the final height, and the block headers in between.
///
/// We need to modify our current state as-we-go, but we also need to use the main
/// traits that define a chainstate. Most cruccially, both crates don't take a mutable
/// reference in any method, so we need some form of interior mutability.
/// We could just use a mutex, but this is not required and very wateful. Partial chains
/// differ from the normal chain because they only have one owner, the worker responsible
/// for driving this chain to it's completion. Because of that, we can simply use a UnsafeCell
/// and forbit shared access between threads by not implementing [Clone].
pub struct PartialChainState(pub(crate) UnsafeCell<PartialChainStateInner>);

/// We need to send [PartialChainState] between threads/tasks, because the worker thread, once it
/// finishes, needs to notify the main task and pass the final partial chain.
/// # Safety
///
/// All itens inside the [UnsafeCell] are [Send], most importantly, there are no references or
/// smart pointers inside it, so sending shouldn't be a problem.
unsafe impl Send for PartialChainState {}
unsafe impl Sync for PartialChainState {}

impl PartialChainStateInner {
    /// Returns the height we have synced up to so far
    pub fn current_height(&self) -> u32 {
        self.current_height
    }

    /// Whether or not we have synced up to the final height
    pub fn is_sync(&self) -> bool {
        self.current_height == self.final_height
    }

    pub fn get_block(&self, height: u32) -> Option<&BlockHeader> {
        let index = height - self.initial_height;
        self.blocks.get(index as usize)
    }

    #[cfg(feature = "bitcoinconsensus")]
    /// Returns the validation flags, given the current block height
    fn get_validation_flags(&self, height: u32) -> c_uint {
        let chains_params = &self.consensus.parameters;
        let hash = self.get_block(height).unwrap().block_hash();
        if let Some(flag) = chains_params.exceptions.get(&hash) {
            return *flag;
        }
        // From Bitcoin Core:
        // BIP16 didn't become active until Apr 1 2012 (on mainnet, and
        // retroactively applied to testnet)
        // However, only one historical block violated the P2SH rules (on both
        // mainnet and testnet).
        // Similarly, only one historical block violated the TAPROOT rules on
        // mainnet.
        // For simplicity, always leave P2SH+WITNESS+TAPROOT on except for the two
        // violating blocks.
        let mut flags = bitcoinconsensus::VERIFY_P2SH | bitcoinconsensus::VERIFY_WITNESS;

        if height >= chains_params.bip65_activation_height {
            flags |= bitcoinconsensus::VERIFY_CHECKLOCKTIMEVERIFY;
        }
        if height >= chains_params.bip66_activation_height {
            flags |= bitcoinconsensus::VERIFY_DERSIG;
        }
        if height >= chains_params.csv_activation_height {
            flags |= bitcoinconsensus::VERIFY_CHECKSEQUENCEVERIFY;
        }
        if height >= chains_params.segwit_activation_height {
            flags |= bitcoinconsensus::VERIFY_NULLDUMMY;
        }
        flags
    }

    #[inline]
    /// Update our internal state, given a new height and accumulator
    fn update_state(&mut self, height: u32, acc: Stump) {
        self.current_height = height;
        self.current_acc = acc;
    }

    #[inline]
    /// Returns the parameters for this chain
    fn chain_params(&self) -> ChainParams {
        self.consensus.parameters.clone()
    }

    #[inline]
    /// Returns the ancestor for a given block header
    fn get_ancestor(&self, height: u32) -> Result<BlockHeader, BlockchainError> {
        let prev = self.get_block(height - 1).unwrap();
        Ok(*prev)
    }

    /// Process a block, given the proof, inputs, and deleted hashes. If we find an error,
    /// we save it.
    pub fn process_block(
        &mut self,
        block: &bitcoin::Block,
        proof: rustreexo::accumulator::proof::Proof,
        inputs: HashMap<bitcoin::OutPoint, bitcoin::TxOut>,
        del_hashes: Vec<bitcoin::hashes::sha256::Hash>,
    ) -> Result<u32, BlockchainError> {
        let height = self.current_height + 1;

        if let Err(BlockchainError::BlockValidation(e)) = self.validate_block(block, height, inputs)
        {
            self.error = Some(e.clone());
            return Err(BlockchainError::BlockValidation(e));
        }

        let acc = match Consensus::update_acc(&self.current_acc, block, height, proof, del_hashes) {
            Ok(acc) => acc,
            Err(_) => {
                self.error = Some(BlockValidationErrors::InvalidProof);
                return Err(BlockchainError::InvalidProof);
            }
        };

        // ... If we came this far, we consider this block valid ...

        if height % 10_000 == 0 {
            info!(
                "Downloading blocks: height={height} hash={}",
                block.block_hash()
            );
        }
        self.update_state(height, acc);

        Ok(height)
    }

    /// Check whether a block is valid
    fn validate_block(
        &self,
        block: &bitcoin::Block,
        height: u32,
        inputs: HashMap<bitcoin::OutPoint, bitcoin::TxOut>,
    ) -> Result<(), BlockchainError> {
        if !block.check_merkle_root() {
            return Err(BlockchainError::BlockValidation(
                BlockValidationErrors::BadMerkleRoot,
            ));
        }
        if height >= self.chain_params().bip34_activation_height
            && block.bip34_block_height() != Ok(height as u64)
        {
            return Err(BlockchainError::BlockValidation(
                BlockValidationErrors::BadBip34,
            ));
        }
        if !block.check_witness_commitment() {
            return Err(BlockchainError::BlockValidation(
                BlockValidationErrors::BadWitnessCommitment,
            ));
        }
        let prev_block = self.get_ancestor(height)?;
        if block.header.prev_blockhash != prev_block.block_hash() {
            return Err(BlockchainError::BlockValidation(
                BlockValidationErrors::BlockExtendsAnOrphanChain,
            ));
        }
        // Validate block transactions
        let subsidy = self.consensus.get_subsidy(height);
        let verify_script = self.assume_valid;
        #[cfg(feature = "bitcoinconsensus")]
        let flags = self.get_validation_flags(height);
        #[cfg(not(feature = "bitcoinconsensus"))]
        let flags = 0;
        Consensus::verify_block_transactions(
            height,
            inputs,
            &block.txdata,
            subsidy,
            verify_script,
            flags,
        )?;
        Ok(())
    }
}

impl PartialChainState {
    /// Borrows the inner content as immutable referece.
    ///
    /// # Safety
    /// We can assume this [UnsafeCell] is initialized because the only way to get a
    /// [PartialChainState] is through our APIs, and we make sure this [UnsafeCell] is
    /// always valid.
    /// The reference returned here **should not** leak through the API, as there's no
    /// syncronization mechanims for it.
    #[inline(always)]
    #[must_use]
    #[doc(hidden)]
    fn inner(&self) -> &PartialChainStateInner {
        unsafe { self.0.get().as_ref().expect("this pointer is valid") }
    }

    /// Borrows the inner content as a mutable referece.
    ///
    /// # Safety
    /// We can assume this [UnsafeCell] is initialized because the only way to get a
    /// [PartialChainState] is through our APIs, and we make sure this [UnsafeCell] is
    /// always valid.
    /// The reference returned here **should not** leak through the API, as there's no
    /// syncronization mechanims for it.
    #[inline(always)]
    #[allow(clippy::mut_from_ref)]
    #[must_use]
    #[doc(hidden)]
    fn inner_mut(&self) -> &mut PartialChainStateInner {
        unsafe { self.0.get().as_mut().expect("this pointer is valid") }
    }

    /// Returns all blocks in this partial chain
    pub fn list_blocks(&self) -> &[BlockHeader] {
        &self.inner().blocks
    }

    /// Returns all block we have validated so far in this chain
    pub fn list_valid_blocks(&self) -> Vec<&BlockHeader> {
        self.inner()
            .blocks
            .iter()
            .take(self.inner().current_height as usize)
            .collect()
    }

    /// Returns whether any block inside this interval is invalid
    pub fn has_invalid_blocks(&self) -> bool {
        self.inner().error.is_some()
    }
}

impl UpdatableChainstate for PartialChainState {
    fn connect_block(
        &self,
        block: &bitcoin::Block,
        proof: rustreexo::accumulator::proof::Proof,
        inputs: HashMap<bitcoin::OutPoint, bitcoin::TxOut>,
        del_hashes: Vec<bitcoin::hashes::sha256::Hash>,
    ) -> Result<u32, BlockchainError> {
        self.inner_mut()
            .process_block(block, proof, inputs, del_hashes)
    }

    fn get_root_hashes(&self) -> Vec<rustreexo::accumulator::node_hash::NodeHash> {
        self.inner().current_acc.roots.clone()
    }

    //these are no-ops, you can call them, but they won't do anything

    fn flush(&self) -> Result<(), BlockchainError> {
        // no-op: we keep everything on memory
        Ok(())
    }

    fn toggle_ibd(&self, _is_ibd: bool) {
        // no-op: we know if we finished by looking at our current and end height
    }

    // these are unimplemented, and will panic if called

    fn accept_header(&self, _header: BlockHeader) -> Result<(), BlockchainError> {
        unimplemented!("partialChainState shouldn't be used to accept new headers")
    }

    fn switch_chain(&self, _new_tip: BlockHash) -> Result<(), BlockchainError> {
        unimplemented!("partialChainState shouldn't be used to switch chains")
    }

    fn get_partial_chain(
        &self,
        _initial_height: u32,
        _final_height: u32,
        _acc: Stump,
    ) -> Result<PartialChainState, BlockchainError> {
        unimplemented!("We are a partial chain")
    }

    fn invalidate_block(&self, _block: BlockHash) -> Result<(), BlockchainError> {
        unimplemented!("we know if a block is invalid, just break out of your loop and use the is_valid() method")
    }

    fn handle_transaction(&self) -> Result<(), BlockchainError> {
        unimplemented!("we don't do transactions")
    }

    fn process_rescan_block(&self, _block: &bitcoin::Block) -> Result<(), BlockchainError> {
        unimplemented!("we don't do rescan")
    }

    fn mark_chain_as_assumed(&self, _acc: Stump, _tip: BlockHash) -> Result<bool, BlockchainError> {
        unimplemented!("no need to mark as valid")
    }

    fn mark_block_as_valid(&self, _block: BlockHash) -> Result<(), BlockchainError> {
        unimplemented!("no need to mark as valid")
    }
}

impl BlockchainInterface for PartialChainState {
    type Error = BlockchainError;

    fn get_height(&self) -> Result<u32, Self::Error> {
        Ok(self.inner().current_height)
    }

    fn get_block_hash(&self, height: u32) -> Result<bitcoin::BlockHash, BlockchainError> {
        let height = height - self.inner().initial_height;
        self.inner()
            .blocks
            .get(height as usize)
            .map(|b| b.block_hash())
            .ok_or(BlockchainError::BlockNotPresent)
    }

    fn get_best_block(&self) -> Result<(u32, bitcoin::BlockHash), Self::Error> {
        Ok((
            self.inner().current_height(),
            self.get_block_hash(self.inner().current_height())?,
        ))
    }

    fn is_coinbase_mature(
        &self,
        height: u32,
        _block: bitcoin::BlockHash,
    ) -> Result<bool, Self::Error> {
        let current_height = self.inner().current_height;
        let coinbase_maturity = self.inner().chain_params().coinbase_maturity;

        Ok(height + coinbase_maturity > current_height)
    }

    fn get_validation_index(&self) -> Result<u32, Self::Error> {
        Ok(self.inner().current_height)
    }

    fn is_in_idb(&self) -> bool {
        !self.inner().is_sync()
    }

    // partial chain states are only used for IBD, so we don't need to implement these

    fn get_block_header(&self, _height: &BlockHash) -> Result<BlockHeader, Self::Error> {
        unimplemented!("PartialChainState::get_block_header")
    }

    fn get_chain_tips(&self) -> Result<Vec<BlockHash>, Self::Error> {
        unimplemented!("PartialChainState::get_chain_tips")
    }

    fn validate_block(
        &self,
        _block: &bitcoin::Block,
        _proof: rustreexo::accumulator::proof::Proof,
        _inputs: HashMap<bitcoin::OutPoint, bitcoin::TxOut>,
        _del_hashes: Vec<bitcoin::hashes::sha256::Hash>,
        _acc: Stump,
    ) -> Result<(), Self::Error> {
        unimplemented!("PartialChainState::validate_block")
    }

    fn get_fork_point(&self, _block: BlockHash) -> Result<BlockHash, Self::Error> {
        unimplemented!("PartialChainState::get_fork_point")
    }

    fn update_acc(
        &self,
        _acc: Stump,
        _block: UtreexoBlock,
        _height: u32,
        _proof: rustreexo::accumulator::proof::Proof,
        _del_hashes: Vec<bitcoin::hashes::sha256::Hash>,
    ) -> Result<Stump, Self::Error> {
        unimplemented!("PartialChainState::update_acc")
    }

    fn get_block_locator_for_tip(
        &self,
        _tip: BlockHash,
    ) -> Result<Vec<BlockHash>, BlockchainError> {
        unimplemented!("PartialChainState::get_block_locator_for_tip")
    }

    fn get_block(&self, _hash: &bitcoin::BlockHash) -> Result<bitcoin::Block, Self::Error> {
        unimplemented!("PartialChainState::get_block")
    }

    fn get_tx(&self, _txid: &bitcoin::Txid) -> Result<Option<bitcoin::Transaction>, Self::Error> {
        unimplemented!("partialChainState::get_tx")
    }

    fn rescan(&self, _start_height: u32) -> Result<(), Self::Error> {
        unimplemented!("partialChainState::rescan")
    }

    fn broadcast(&self, _tx: &bitcoin::Transaction) -> Result<(), Self::Error> {
        unimplemented!("partialChainState::broadcast")
    }

    fn subscribe(&self, _tx: sync::Arc<dyn crate::BlockConsumer>) {
        unimplemented!("partialChainState::subscibe")
    }

    fn estimate_fee(&self, _target: usize) -> Result<f64, Self::Error> {
        unimplemented!("partialChainState::estimate_fee")
    }

    fn get_rescan_index(&self) -> Option<u32> {
        unimplemented!("partialChainState::get_rescan_index")
    }

    fn get_block_height(&self, _hash: &bitcoin::BlockHash) -> Result<Option<u32>, Self::Error> {
        unimplemented!("partialChainState::get_block_height")
    }

    fn get_unbroadcasted(&self) -> Vec<bitcoin::Transaction> {
        unimplemented!("partialChainState::get_unbroadcasted")
    }

    fn get_block_locator(&self) -> Result<Vec<bitcoin::BlockHash>, Self::Error> {
        unimplemented!("partialChainState::get_block_locator")
    }
}

// mainly for tests
impl From<PartialChainStateInner> for PartialChainState {
    fn from(value: PartialChainStateInner) -> Self {
        PartialChainState(UnsafeCell::new(value))
    }
}

#[cfg(test)]
mod tests {

    use core::str::FromStr;
    use std::collections::HashMap;

    use bitcoin::block::Header;
    use bitcoin::consensus::deserialize;
    use bitcoin::Block;
    use rustreexo::accumulator::node_hash::NodeHash;
    use rustreexo::accumulator::proof::Proof;
    use rustreexo::accumulator::stump::Stump;

    use super::PartialChainState;
    use crate::pruned_utreexo::chainparams::ChainParams;
    use crate::pruned_utreexo::consensus::Consensus;
    use crate::pruned_utreexo::error::BlockValidationErrors;
    use crate::pruned_utreexo::partial_chain::PartialChainStateInner;
    use crate::pruned_utreexo::UpdatableChainstate;
    use crate::BlockchainError;
    use crate::Network;

    #[test]
    fn test_with_invalid_block() {
        fn run(block: &str, reason: BlockValidationErrors) {
            let genesis = parse_block("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");
            let block = parse_block(block);

            let chainstate = get_empty_pchain(vec![genesis.header, block.header]);
            let res = chainstate.connect_block(&block, Proof::default(), HashMap::new(), vec![]);

            match res {
                Err(BlockchainError::BlockValidation(_e)) if matches!(reason, _e) => {}
                _ => panic!("unexpected {res:?}"),
            };
        }
        run("0000002000226e46111a0b59caaf126043eb5bbf28c34f3a5e332a1fc7b2b73cf188910f39adbcd7823048d34357bdca86cd47172afe2a4af8366b5b34db36df89386d49b23ec964ffff7f20000000000101000000010000000000000000000000000000000000000000000000000000000000000000ffffffff165108feddb99c6b8435060b2f503253482f627463642fffffffff0100f2052a01000000160014806cef41295922d32ddfca09c26cc4acd36c3ed000000000",super::BlockValidationErrors::BlockExtendsAnOrphanChain);
        run("0000002000226e46111a0b59caaf126043eb5bbf28c34f3a5e332a1fc7b2b73cf188910f40adbcd7823048d34357bdca86cd47172afe2a4af8366b5b34db36df89386d49b23ec964ffff7f20000000000101000000010000000000000000000000000000000000000000000000000000000000000000ffffffff165108feddb99c6b8435060b2f503253482f627463642fffffffff0100f2052a01000000160014806cef41295922d32ddfca09c26cc4acd36c3ed000000000", BlockValidationErrors::BadMerkleRoot);
    }
    fn parse_block(hex: &str) -> Block {
        let block = hex::decode(hex).unwrap();
        deserialize(&block).unwrap()
    }
    fn get_empty_pchain(blocks: Vec<Header>) -> PartialChainState {
        PartialChainStateInner {
            assume_valid: true,
            consensus: Consensus {
                parameters: ChainParams::from(Network::Regtest),
            },
            current_height: 0,
            current_acc: Stump::default(),
            final_height: 1,
            blocks,
            error: None,
            initial_height: 0,
        }
        .into()
    }

    #[test]
    fn test_updating_single_chain() {
        let blocks = include_str!("./testdata/blocks.txt");
        let mut parsed_blocks = vec![];
        for (i, block) in blocks.lines().enumerate() {
            if i > 100 {
                break;
            }
            let block: Block = deserialize(&hex::decode(block).unwrap()).unwrap();
            parsed_blocks.push(block);
        }
        let chainstate: PartialChainState = PartialChainStateInner {
            assume_valid: true,
            consensus: Consensus {
                parameters: ChainParams::from(Network::Regtest),
            },
            current_height: 0,
            current_acc: Stump::default(),
            final_height: 100,
            blocks: parsed_blocks.iter().map(|block| block.header).collect(),
            error: None,
            initial_height: 0,
        }
        .into();
        parsed_blocks.remove(0);
        for block in parsed_blocks {
            let proof = Proof::default();
            let inputs = HashMap::new();
            let del_hashes = vec![];
            chainstate
                .connect_block(&block, proof, inputs, del_hashes)
                .unwrap();
        }
        assert_eq!(chainstate.inner().current_height, 100);
    }

    #[test]
    fn test_updating_multiple_chains() {
        // We have two chains, one with 100 blocks, one with 50 blocks. We expect the
        // accumulator to be what we expect after 100 blocks and after 150 blocks.
        let blocks = include_str!("./testdata/blocks.txt");
        let mut parsed_blocks = vec![];
        for block in blocks.lines() {
            let block: Block = deserialize(&hex::decode(block).unwrap()).unwrap();
            parsed_blocks.push(block);
        }
        // The file contains 150 blocks, we split them into two chains.
        let (blocks1, blocks2) = parsed_blocks.split_at(101);
        let mut chainstate1 = PartialChainStateInner {
            assume_valid: true,
            consensus: Consensus {
                parameters: ChainParams::from(Network::Regtest),
            },
            current_height: 0,
            current_acc: Stump::default(),
            final_height: 100,
            blocks: blocks1.iter().map(|block| block.header).collect(),
            error: None,
            initial_height: 0,
        };
        // We need to add the last block of the first chain to the second chain, so that
        // the second chain can validate all its blocks.
        let mut blocks2_headers = vec![blocks1.last().unwrap()];
        blocks2_headers.extend(blocks2);

        let blocks2_headers = blocks2_headers.iter().map(|block| block.header).collect();

        let mut blocks1 = blocks1.iter();
        blocks1.next();

        for block in blocks1 {
            let proof = Proof::default();
            let inputs = HashMap::new();
            let del_hashes = vec![];
            chainstate1
                .process_block(block, proof, inputs, del_hashes)
                .unwrap();
        }
        // The state after 100 blocks, computed ahead of time.
        let roots = [
            "a2f1e6db842e13c7480c8d80f29ca2db5f9b96e1b428ebfdbd389676d7619081",
            "b21aae30bc74e9aef600a5d507ef27d799b9b6ba08e514656d34d717bdb569d2",
            "bedb648c9a3c5741660f926c1552d83ebb4cb1842cca6855b6d1089bb4951ce1",
        ]
        .iter()
        .map(|hash| NodeHash::from_str(hash).unwrap())
        .collect();

        let acc2 = Stump { roots, leaves: 100 };

        // acc2 is hard-coded, while chainstate1.current_acc is calculated.
        // after catching up in the first half, the accumulator should be the same.
        // We can have the speedup of doing it in parallel, without needing to trust
        // the hard-coded values.
        assert_eq!(chainstate1.current_acc, acc2);

        let chainstate2: PartialChainState = PartialChainStateInner {
            assume_valid: true,
            consensus: Consensus {
                parameters: ChainParams::from(Network::Regtest),
            },
            current_height: 100,
            current_acc: acc2,
            final_height: 150,
            blocks: blocks2_headers,
            error: None,
            initial_height: 100,
        }
        .into();

        for block in blocks2 {
            let proof = Proof::default();
            let inputs = HashMap::new();
            let del_hashes = vec![];
            chainstate2
                .connect_block(block, proof, inputs, del_hashes)
                .unwrap();
        }

        let roots = [
            "e00b4ecc7c30865af0ac3b0c7c1b996015f51d6a6577ee6f52cc04b55933eb91",
            "9bf9659f93e246e0431e228032cd4b3a4d8a13e57f3e08a221e61f3e0bae657f",
            "e329a7ddcc888130bb6e4f82ce9f5cf5a712a7b0ae05a1aaf21b363866a9b05e",
            "1864a4982532447dcb3d9a5d2fea9f8ed4e3b1e759d55b8a427fb599fed0c302",
        ]
        .iter()
        .map(|x| NodeHash::from(hex::decode(x).unwrap().as_slice()))
        .collect::<Vec<_>>();

        let expected_acc: Stump = Stump { leaves: 150, roots };

        assert_eq!(chainstate2.inner().current_height, 150);
        assert_eq!(chainstate2.inner().current_acc, expected_acc);
    }
}