// Copyright 2015-2019 Parity Technologies (UK) Ltd.
// This file is part of Parity Ethereum.

// Parity Ethereum 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.

// Parity Ethereum 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 Parity Ethereum.  If not, see <http://www.gnu.org/licenses/>.

//! A provider for the PIP protocol. This is typically a full node, who can
//! give as much data as necessary to its peers.

use std::sync::Arc;

use common_types::{
    blockchain_info::BlockChainInfo, encoded, ids::BlockId, transaction::PendingTransaction,
};
use ethcore::client::{
    BlockChainClient, BlockInfo as ClientBlockInfo, ChainInfo, ProvingBlockChainClient,
};
use ethereum_types::H256;
use parking_lot::RwLock;

use cht::{self, BlockInfo};
use client::{AsLightClient, LightChainClient};
use transaction_queue::TransactionQueue;

use request;

/// Maximum allowed size of a headers request.
pub const MAX_HEADERS_PER_REQUEST: u64 = 512;

/// Defines the operations that a provider for the light subprotocol must fulfill.
pub trait Provider: Send + Sync {
    /// Provide current blockchain info.
    fn chain_info(&self) -> BlockChainInfo;

    /// Find the depth of a common ancestor between two blocks.
    /// If either block is unknown or an ancestor can't be found
    /// then return `None`.
    fn reorg_depth(&self, a: &H256, b: &H256) -> Option<u64>;

    /// Earliest block where state queries are available.
    /// If `None`, no state queries are servable.
    fn earliest_state(&self) -> Option<u64>;

    /// Provide a list of headers starting at the requested block,
    /// possibly in reverse and skipping `skip` at a time.
    ///
    /// The returned vector may have any length in the range [0, `max`], but the
    /// results within must adhere to the `skip` and `reverse` parameters.
    fn block_headers(
        &self,
        req: request::CompleteHeadersRequest,
    ) -> Option<request::HeadersResponse> {
        use request::HashOrNumber;

        if req.max == 0 {
            return None;
        }

        let best_num = self.chain_info().best_block_number;
        let start_num = match req.start {
            HashOrNumber::Number(start_num) => start_num,
            HashOrNumber::Hash(hash) => match self.block_header(BlockId::Hash(hash)) {
                None => {
                    trace!(target: "pip_provider", "Unknown block hash {} requested", hash);
                    return None;
                }
                Some(header) => {
                    let num = header.number();
                    let canon_hash = self.block_header(BlockId::Number(num)).map(|h| h.hash());

                    if req.max == 1 || canon_hash != Some(hash) {
                        // Non-canonical header or single header requested.
                        return Some(::request::HeadersResponse {
                            headers: vec![header],
                        });
                    }

                    num
                }
            },
        };

        let max = ::std::cmp::min(MAX_HEADERS_PER_REQUEST, req.max);

        let headers: Vec<_> = (0_u64..max)
            .map(|x: u64| x.saturating_mul(req.skip.saturating_add(1)))
            .take_while(|&x| {
                if req.reverse {
                    x < start_num
                } else {
                    best_num.saturating_sub(start_num) >= x
                }
            })
            .map(|x| {
                if req.reverse {
                    start_num.saturating_sub(x)
                } else {
                    start_num.saturating_add(x)
                }
            })
            .map(|x| self.block_header(BlockId::Number(x)))
            .take_while(|x| x.is_some())
            .flat_map(|x| x)
            .collect();

        if headers.is_empty() {
            None
        } else {
            Some(::request::HeadersResponse { headers })
        }
    }

    /// Get a block header by id.
    fn block_header(&self, id: BlockId) -> Option<encoded::Header>;

    /// Get a transaction index by hash.
    fn transaction_index(
        &self,
        req: request::CompleteTransactionIndexRequest,
    ) -> Option<request::TransactionIndexResponse>;

    /// Fulfill a block body request.
    fn block_body(&self, req: request::CompleteBodyRequest) -> Option<request::BodyResponse>;

    /// Fulfill a request for block receipts.
    fn block_receipts(
        &self,
        req: request::CompleteReceiptsRequest,
    ) -> Option<request::ReceiptsResponse>;

    /// Get an account proof.
    fn account_proof(
        &self,
        req: request::CompleteAccountRequest,
    ) -> Option<request::AccountResponse>;

    /// Get a storage proof.
    fn storage_proof(
        &self,
        req: request::CompleteStorageRequest,
    ) -> Option<request::StorageResponse>;

    /// Provide contract code for the specified (block_hash, code_hash) pair.
    fn contract_code(&self, req: request::CompleteCodeRequest) -> Option<request::CodeResponse>;

    /// Provide a header proof from a given Canonical Hash Trie as well as the
    /// corresponding header.
    fn header_proof(
        &self,
        req: request::CompleteHeaderProofRequest,
    ) -> Option<request::HeaderProofResponse>;

    /// Provide pending transactions.
    fn transactions_to_propagate(&self) -> Vec<PendingTransaction>;

    /// Provide a proof-of-execution for the given transaction proof request.
    /// Returns a vector of all state items necessary to execute the transaction.
    fn transaction_proof(
        &self,
        req: request::CompleteExecutionRequest,
    ) -> Option<request::ExecutionResponse>;

    /// Provide epoch signal data at given block hash. This should be just the
    fn epoch_signal(&self, req: request::CompleteSignalRequest) -> Option<request::SignalResponse>;
}

// Implementation of a light client data provider for a client.
impl<T: ProvingBlockChainClient + ?Sized> Provider for T {
    fn chain_info(&self) -> BlockChainInfo {
        ChainInfo::chain_info(self)
    }

    fn reorg_depth(&self, a: &H256, b: &H256) -> Option<u64> {
        self.tree_route(a, b).map(|route| route.index as u64)
    }

    fn earliest_state(&self) -> Option<u64> {
        Some(self.pruning_info().earliest_state)
    }

    fn block_header(&self, id: BlockId) -> Option<encoded::Header> {
        ClientBlockInfo::block_header(self, id)
    }

    fn transaction_index(
        &self,
        req: request::CompleteTransactionIndexRequest,
    ) -> Option<request::TransactionIndexResponse> {
        use common_types::ids::TransactionId;

        self.transaction_receipt(TransactionId::Hash(req.hash))
            .map(|receipt| request::TransactionIndexResponse {
                num: receipt.block_number,
                hash: receipt.block_hash,
                index: receipt.transaction_index as u64,
            })
    }

    fn block_body(&self, req: request::CompleteBodyRequest) -> Option<request::BodyResponse> {
        BlockChainClient::block_body(self, BlockId::Hash(req.hash))
            .map(|body| ::request::BodyResponse { body })
    }

    fn block_receipts(
        &self,
        req: request::CompleteReceiptsRequest,
    ) -> Option<request::ReceiptsResponse> {
        BlockChainClient::block_receipts(self, &req.hash).map(|x| ::request::ReceiptsResponse {
            receipts: x.receipts,
        })
    }

    fn account_proof(
        &self,
        req: request::CompleteAccountRequest,
    ) -> Option<request::AccountResponse> {
        self.prove_account(req.address_hash, BlockId::Hash(req.block_hash))
            .map(|(proof, acc)| ::request::AccountResponse {
                proof,
                nonce: acc.nonce,
                balance: acc.balance,
                code_hash: acc.code_hash,
                storage_root: acc.storage_root,
            })
    }

    fn storage_proof(
        &self,
        req: request::CompleteStorageRequest,
    ) -> Option<request::StorageResponse> {
        self.prove_storage(
            req.address_hash,
            req.key_hash,
            BlockId::Hash(req.block_hash),
        )
        .map(|(proof, item)| ::request::StorageResponse { proof, value: item })
    }

    fn contract_code(&self, req: request::CompleteCodeRequest) -> Option<request::CodeResponse> {
        self.state_data(&req.code_hash)
            .map(|code| ::request::CodeResponse { code })
    }

    fn header_proof(
        &self,
        req: request::CompleteHeaderProofRequest,
    ) -> Option<request::HeaderProofResponse> {
        let cht_number = match cht::block_to_cht_number(req.num) {
            Some(cht_num) => cht_num,
            None => {
                debug!(target: "pip_provider", "Requested CHT proof with invalid block number");
                return None;
            }
        };

        let mut needed = None;

        // build the CHT, caching the requested header as we pass through it.
        let cht = {
            let block_info = |id| {
                let hdr = self.block_header(id);
                let td = self.block_total_difficulty(id);

                match (hdr, td) {
                    (Some(hdr), Some(td)) => {
                        let info = BlockInfo {
                            hash: hdr.hash(),
                            parent_hash: hdr.parent_hash(),
                            total_difficulty: td,
                        };

                        if hdr.number() == req.num {
                            needed = Some((hdr, td));
                        }

                        Some(info)
                    }
                    _ => None,
                }
            };

            match cht::build(cht_number, block_info) {
                Some(cht) => cht,
                None => return None, // incomplete CHT.
            }
        };

        let (needed_hdr, needed_td) =
            needed.expect("`needed` always set in loop, number checked before; qed");

        // prove our result.
        match cht.prove(req.num, 0) {
            Ok(Some(proof)) => Some(::request::HeaderProofResponse {
                proof,
                hash: needed_hdr.hash(),
                td: needed_td,
            }),
            Ok(None) => None,
            Err(e) => {
                debug!(target: "pip_provider", "Error looking up number in freshly-created CHT: {}", e);
                None
            }
        }
    }

    fn transaction_proof(
        &self,
        req: request::CompleteExecutionRequest,
    ) -> Option<request::ExecutionResponse> {
        use common_types::transaction::Transaction;

        let id = BlockId::Hash(req.block_hash);
        let nonce = match self.nonce(&req.from, id) {
            Some(nonce) => nonce,
            None => return None,
        };
        let transaction = Transaction {
            nonce,
            gas: req.gas,
            gas_price: req.gas_price,
            action: req.action,
            value: req.value,
            data: req.data,
        }
        .fake_sign(req.from);

        self.prove_transaction(transaction, id)
            .map(|(_, proof)| ::request::ExecutionResponse { items: proof })
    }

    fn transactions_to_propagate(&self) -> Vec<PendingTransaction> {
        BlockChainClient::transactions_to_propagate(self)
            .into_iter()
            .map(|tx| tx.pending().clone())
            .collect()
    }

    fn epoch_signal(&self, req: request::CompleteSignalRequest) -> Option<request::SignalResponse> {
        self.epoch_signal(req.block_hash)
            .map(|signal| request::SignalResponse { signal })
    }
}

/// The light client "provider" implementation. This wraps a `LightClient` and
/// a light transaction queue.
pub struct LightProvider<L> {
    client: Arc<L>,
    txqueue: Arc<RwLock<TransactionQueue>>,
}

impl<L> LightProvider<L> {
    /// Create a new `LightProvider` from the given client and transaction queue.
    pub fn new(client: Arc<L>, txqueue: Arc<RwLock<TransactionQueue>>) -> Self {
        LightProvider { client, txqueue }
    }
}

// TODO: draw from cache (shared between this and the RPC layer)
impl<L: AsLightClient + Send + Sync> Provider for LightProvider<L> {
    fn chain_info(&self) -> BlockChainInfo {
        self.client.as_light_client().chain_info()
    }

    fn reorg_depth(&self, _a: &H256, _b: &H256) -> Option<u64> {
        None
    }

    fn earliest_state(&self) -> Option<u64> {
        None
    }

    fn block_header(&self, id: BlockId) -> Option<encoded::Header> {
        self.client.as_light_client().block_header(id)
    }

    fn transaction_index(
        &self,
        _req: request::CompleteTransactionIndexRequest,
    ) -> Option<request::TransactionIndexResponse> {
        None
    }

    fn block_body(&self, _req: request::CompleteBodyRequest) -> Option<request::BodyResponse> {
        None
    }

    fn block_receipts(
        &self,
        _req: request::CompleteReceiptsRequest,
    ) -> Option<request::ReceiptsResponse> {
        None
    }

    fn account_proof(
        &self,
        _req: request::CompleteAccountRequest,
    ) -> Option<request::AccountResponse> {
        None
    }

    fn storage_proof(
        &self,
        _req: request::CompleteStorageRequest,
    ) -> Option<request::StorageResponse> {
        None
    }

    fn contract_code(&self, _req: request::CompleteCodeRequest) -> Option<request::CodeResponse> {
        None
    }

    fn header_proof(
        &self,
        _req: request::CompleteHeaderProofRequest,
    ) -> Option<request::HeaderProofResponse> {
        None
    }

    fn transaction_proof(
        &self,
        _req: request::CompleteExecutionRequest,
    ) -> Option<request::ExecutionResponse> {
        None
    }

    fn epoch_signal(
        &self,
        _req: request::CompleteSignalRequest,
    ) -> Option<request::SignalResponse> {
        None
    }

    fn transactions_to_propagate(&self) -> Vec<PendingTransaction> {
        let chain_info = self.chain_info();
        self.txqueue.read().ready_transactions(
            chain_info.best_block_number,
            chain_info.best_block_timestamp,
        )
    }
}

impl<L: AsLightClient> AsLightClient for LightProvider<L> {
    type Client = L::Client;

    fn as_light_client(&self) -> &L::Client {
        self.client.as_light_client()
    }
}

#[cfg(test)]
mod tests {
    use super::Provider;
    use ethcore::client::{EachBlockWith, TestBlockChainClient};

    #[test]
    fn cht_proof() {
        let client = TestBlockChainClient::new();
        client.add_blocks(2000, EachBlockWith::Nothing);

        let req = ::request::CompleteHeaderProofRequest { num: 1500 };

        assert!(client.header_proof(req.clone()).is_none());

        client.add_blocks(48, EachBlockWith::Nothing);

        assert!(client.header_proof(req.clone()).is_some());
    }
}