// Copyright 2015-2020 Parity Technologies (UK) Ltd.
// This file is part of OpenEthereum.

// OpenEthereum is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// OpenEthereum is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with OpenEthereum.  If not, see <http://www.gnu.org/licenses/>.

//! Blockchain generator for tests.

use ethereum_types::{Bloom, H256, U256};
use std::collections::VecDeque;

use common_types::{
    encoded,
    header::Header,
    transaction::{Action, SignedTransaction, Transaction},
    view,
    views::BlockView,
};
use keccak_hash::keccak;
use rlp::encode;
use rlp_derive::RlpEncodable;
use triehash_ethereum::ordered_trie_root;

/// Helper structure, used for encoding blocks.
#[derive(Default, Clone, RlpEncodable)]
pub struct Block {
    /// Block header
    pub header: Header,
    /// Block transactions
    pub transactions: Vec<SignedTransaction>,
    /// Block uncles
    pub uncles: Vec<Header>,
}

impl Block {
    /// Get a copy of the header
    #[inline]
    pub fn header(&self) -> Header {
        self.header.clone()
    }

    /// Get block hash
    #[inline]
    pub fn hash(&self) -> H256 {
        view!(BlockView, &self.encoded().raw()).header_view().hash()
    }

    /// Get block number
    #[inline]
    pub fn number(&self) -> u64 {
        self.header.number()
    }

    /// Get RLP encoding of this block
    #[inline]
    pub fn encoded(&self) -> encoded::Block {
        encoded::Block::new(encode(self))
    }

    /// Get block difficulty
    #[inline]
    pub fn difficulty(&self) -> U256 {
        *self.header.difficulty()
    }
}

/// Specify block options for generator
#[derive(Debug)]
pub struct BlockOptions {
    /// Difficulty
    pub difficulty: U256,
    /// Set bloom filter
    pub bloom: Bloom,
    /// Transactions included in blocks
    pub transactions: Vec<SignedTransaction>,
}

impl Default for BlockOptions {
    fn default() -> Self {
        BlockOptions {
            difficulty: 10.into(),
            bloom: Bloom::default(),
            transactions: Vec::new(),
        }
    }
}

/// Utility to create blocks
#[derive(Clone)]
pub struct BlockBuilder {
    blocks: VecDeque<Block>,
}

impl BlockBuilder {
    /// Create new BlockBuilder starting at genesis.
    pub fn genesis() -> Self {
        let mut blocks = VecDeque::with_capacity(1);
        blocks.push_back(Block::default());

        BlockBuilder { blocks }
    }

    /// Add new block with default options.
    #[inline]
    pub fn add_block(&self) -> Self {
        self.add_block_with(|| BlockOptions::default())
    }

    /// Add `count` number of blocks with default options.
    #[inline]
    pub fn add_blocks(&self, count: usize) -> Self {
        self.add_blocks_with(count, || BlockOptions::default())
    }

    /// Add block with specified options.
    #[inline]
    pub fn add_block_with<T>(&self, get_metadata: T) -> Self
    where
        T: Fn() -> BlockOptions,
    {
        self.add_blocks_with(1, get_metadata)
    }

    /// Add a block with given difficulty
    #[inline]
    pub fn add_block_with_difficulty<T>(&self, difficulty: T) -> Self
    where
        T: Into<U256>,
    {
        let difficulty = difficulty.into();
        self.add_blocks_with(1, move || BlockOptions {
            difficulty,
            ..Default::default()
        })
    }

    /// Add a block with randomly generated transactions.
    #[inline]
    pub fn add_block_with_random_transactions(&self) -> Self {
        // Maximum of ~50 transactions
        let count = rand::random::<u8>() as usize / 5;
        let transactions = std::iter::repeat_with(|| {
            let data_len = rand::random::<u8>();
            let data = std::iter::repeat_with(|| rand::random::<u8>())
                .take(data_len as usize)
                .collect::<Vec<_>>();
            Transaction {
                nonce: 0.into(),
                gas_price: 0.into(),
                gas: 100_000.into(),
                action: Action::Create,
                value: 100.into(),
                data,
            }
            .sign(&keccak("").into(), None)
        })
        .take(count);

        self.add_block_with_transactions(transactions)
    }

    /// Add a block with given transactions.
    #[inline]
    pub fn add_block_with_transactions<T>(&self, transactions: T) -> Self
    where
        T: IntoIterator<Item = SignedTransaction>,
    {
        let transactions = transactions.into_iter().collect::<Vec<_>>();
        self.add_blocks_with(1, || BlockOptions {
            transactions: transactions.clone(),
            ..Default::default()
        })
    }

    /// Add a block with given bloom filter.
    #[inline]
    pub fn add_block_with_bloom(&self, bloom: Bloom) -> Self {
        self.add_blocks_with(1, move || BlockOptions {
            bloom,
            ..Default::default()
        })
    }

    /// Add a bunch of blocks with given metadata.
    pub fn add_blocks_with<T>(&self, count: usize, get_metadata: T) -> Self
    where
        T: Fn() -> BlockOptions,
    {
        assert!(count > 0, "There must be at least 1 block");
        let mut parent_hash = self.last().hash();
        let mut parent_number = self.last().number();
        let mut blocks = VecDeque::with_capacity(count);
        for _ in 0..count {
            let mut block = Block::default();
            let metadata = get_metadata();
            let block_number = parent_number + 1;
            let transactions = metadata.transactions;
            let transactions_root = ordered_trie_root(transactions.iter().map(rlp::encode));

            block.header.set_parent_hash(parent_hash);
            block.header.set_number(block_number);
            block.header.set_log_bloom(metadata.bloom);
            block.header.set_difficulty(metadata.difficulty);
            block.header.set_transactions_root(transactions_root);
            block.transactions = transactions;

            parent_hash = block.hash();
            parent_number = block_number;

            blocks.push_back(block);
        }

        BlockBuilder { blocks }
    }

    /// Get a reference to the last generated block.
    #[inline]
    pub fn last(&self) -> &Block {
        self.blocks
            .back()
            .expect("There is always at least 1 block")
    }
}

/// Generates a blockchain from given block builders (blocks will be concatenated).
#[derive(Clone)]
pub struct BlockGenerator {
    builders: VecDeque<BlockBuilder>,
}

impl BlockGenerator {
    /// Create new block generator.
    pub fn new<T>(builders: T) -> Self
    where
        T: IntoIterator<Item = BlockBuilder>,
    {
        BlockGenerator {
            builders: builders.into_iter().collect(),
        }
    }
}

impl Iterator for BlockGenerator {
    type Item = Block;

    fn next(&mut self) -> Option<Self::Item> {
        loop {
            match self.builders.front_mut() {
                Some(ref mut builder) => {
                    if let Some(block) = builder.blocks.pop_front() {
                        return Some(block);
                    }
                }
                None => return None,
            }
            self.builders.pop_front();
        }
    }
}

#[cfg(test)]
mod tests {
    use super::{BlockBuilder, BlockGenerator, BlockOptions};

    #[test]
    fn test_block_builder() {
        let genesis = BlockBuilder::genesis();
        let block_1 = genesis.add_block();
        let block_1001 = block_1.add_blocks(1000);
        let block_1002 = block_1001.add_block_with(|| BlockOptions::default());
        let generator = BlockGenerator::new(vec![genesis, block_1, block_1001, block_1002]);
        assert_eq!(generator.count(), 1003);
    }

    #[test]
    fn test_block_builder_fork() {
        let genesis = BlockBuilder::genesis();
        let block_10a = genesis.add_blocks(10);
        let block_11b = genesis.add_blocks(11);
        assert_eq!(block_10a.last().number(), 10);
        assert_eq!(block_11b.last().number(), 11);
    }
}