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//
// Copyright 2018 Tamas Blummer
//
//Licensed under the Apache License, Version 2.0 (the "License");
//you may not use this file except in compliance with the License.
//You may obtain a copy of the License at
//
//http://www.apache.org/licenses/LICENSE-2.0
//
//Unless required by applicable law or agreed to in writing, software
//distributed under the License is distributed on an "AS IS" BASIS,
//WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
//See the License for the specific language governing permissions and
//limitations under the License.
//
extern crate libc;

use libc::{c_int,c_uchar, c_uint};

#[allow(non_camel_case_types)]
#[derive(PartialEq, Eq, PartialOrd, Ord, Hash, Debug, Clone, Copy)]
#[repr(C)]
pub enum Error {
    ERR_SCRIPT = 0,
    #[allow(dead_code)]
    ERR_TX_INDEX,
    #[allow(dead_code)]
    ERR_TX_SIZE_MISMATCH,
    #[allow(dead_code)]
    ERR_TX_DESERIALIZE,
    #[allow(dead_code)]
    ERR_AMOUNT_REQUIRED,
    #[allow(dead_code)]
    ERR_INVALID_FLAGS
}

#[allow(dead_code)]
pub const VERIFY_NONE : c_uint = 0;
// evaluate P2SH (BIP16) subscripts
pub const VERIFY_P2SH : c_uint = (1 << 0);
// enforce strict DER (BIP66) compliance
pub const VERIFY_DERSIG : c_uint = (1 << 2);
// enforce NULLDUMMY (BIP147)
pub const VERIFY_NULLDUMMY : c_uint = (1 << 4);
// enable CHECKLOCKTIMEVERIFY (BIP65)
pub const VERIFY_CHECKLOCKTIMEVERIFY : c_uint = (1 << 9);
// enable CHECKSEQUENCEVERIFY (BIP112)
pub const VERIFY_CHECKSEQUENCEVERIFY : c_uint = (1 << 10);
// enable WITNESS (BIP141)
pub const VERIFY_WITNESS : c_uint = (1 << 11);

pub const VERIFY_ALL : c_uint = VERIFY_P2SH | VERIFY_DERSIG | VERIFY_NULLDUMMY |
    VERIFY_CHECKLOCKTIMEVERIFY | VERIFY_CHECKSEQUENCEVERIFY | VERIFY_WITNESS;

extern "C" {
    pub fn bitcoinconsensus_version() -> c_int;

    pub fn bitcoinconsensus_verify_script_with_amount(
        script_pubkey:  *const c_uchar,
        script_pubkeylen: c_uint,
        amount: u64,
        tx_to: *const c_uchar,
        tx_tolen: c_uint,
        n_in: c_uint,
        flags: c_uint,
        err: *mut Error) -> c_int;
}

/// Compute flags for soft fork activation heights on the Bitcoin network
pub fn height_to_flags(height: u32) -> u32 {

    let mut flag = VERIFY_NONE;
    if height > 170059 {
        flag |= VERIFY_P2SH;
    }
    if height > 363724 {
        flag |= VERIFY_DERSIG;
    }
    if height > 388381 {
        flag |= VERIFY_CHECKLOCKTIMEVERIFY;
    }
    if height > 419328 {
        flag |= VERIFY_CHECKSEQUENCEVERIFY;
    }
    if height > 481824 {
        flag |= VERIFY_NULLDUMMY | VERIFY_WITNESS
    }
    flag as u32
}

/// Return libbitcoinconsenus version
pub fn version () -> u32 {
    unsafe { bitcoinconsensus_version() as u32 }
}

/// Verify a single spend (input) of a Bitcoin transaction.
/// # Arguments
///  * spend_output_script: a Bitcoin transaction output script to be spent, serialized in Bitcoin's on wire format
///  * amount: The spent output amount in satoshis
///  * spending_transaction: spending Bitcoin transaction, serialized in Bitcoin's on wire format
///  * input_index: index of the input within spending_transaction
/// # Returns
/// OK or Err. Note that amount will only be checked for Segwit transactions.
///
/// # Example
///
/// The (randomly choosen) Bitcoin transaction [aca326a724eda9a461c10a876534ecd5ae7b27f10f26c3862fb996f80ea2d45d](https://blockchain.info/tx/aca326a724eda9a461c10a876534ecd5ae7b27f10f26c3862fb996f80ea2d45d)
/// spends one input, that is the first output of [95da344585fcf2e5f7d6cbf2c3df2dcce84f9196f7a7bb901a43275cd6eb7c3f](https://blockchain.info/tx/95da344585fcf2e5f7d6cbf2c3df2dcce84f9196f7a7bb901a43275cd6eb7c3f) with a value of 630482530 satoshis
///
/// The spending transaction in wire format is:
///
/// `
/// spending = 02000000013f7cebd65c27431a90bba7f796914fe8cc2ddfc3f2cbd6f7e5f2fc854534da95000000006b483045022100de1ac3bcdfb0332207c4a91f3832bd2c2915840165f876ab47c5f8996b971c3602201c6c053d750fadde599e6f5c4e1963df0f01fc0d97815e8157e3d59fe09ca30d012103699b464d1d8bc9e47d4fb1cdaa89a1c5783d68363c4dbc4b524ed3d857148617feffffff02836d3c01000000001976a914fc25d6d5c94003bf5b0c7b640a248e2c637fcfb088ac7ada8202000000001976a914fbed3d9b11183209a57999d54d59f67c019e756c88ac6acb0700
/// `
///
/// The script of the first output of the spent transaction is:
///
/// `
/// spent = 76a9144bfbaf6afb76cc5771bc6404810d1cc041a6933988ac
/// `
///
/// The (pseudo code) call:
///
/// `
/// verify(spent, 630482530, spending, 0)
/// `
/// should return OK(())
///
/// **Note** that spent amount will only be checked for Segwit transactions. Above example is not segwit, therefore verify will succeed with any amount.

///
pub fn verify (spent_output: &[u8], amount: u64, spending_transaction: &[u8], input_index: usize) -> Result<(), Error> {
    verify_with_flags (spent_output, amount, spending_transaction, input_index, VERIFY_ALL)
}

/// Same as verify but with flags that turn past soft fork features on or off
pub fn verify_with_flags (spent_output_script: &[u8], amount: u64, spending_transaction: &[u8], input_index: usize, flags: u32) -> Result<(), Error> {
    unsafe {
        let mut error = Error::ERR_SCRIPT;

        let ret = bitcoinconsensus_verify_script_with_amount(
            spent_output_script.as_ptr(),
            spent_output_script.len() as c_uint,
            amount as u64,
            spending_transaction.as_ptr(),
            spending_transaction.len() as c_uint,
            input_index as c_uint,
            flags as c_uint,
            &mut error
        );
        if ret != 1 {
            Err(error)
        } else {
            Ok(())
        }
    }
}

#[cfg(test)]
mod tests {
    extern crate rustc_serialize as serialize;

    use super::*;
    use self::serialize::hex::FromHex;

    #[test]
    fn bitcoinconsensus_test() {
        // a random old-style transaction from the blockchain
        verify_test (
            "76a9144bfbaf6afb76cc5771bc6404810d1cc041a6933988ac",
            "02000000013f7cebd65c27431a90bba7f796914fe8cc2ddfc3f2cbd6f7e5f2fc854534da95000000006b483045022100de1ac3bcdfb0332207c4a91f3832bd2c2915840165f876ab47c5f8996b971c3602201c6c053d750fadde599e6f5c4e1963df0f01fc0d97815e8157e3d59fe09ca30d012103699b464d1d8bc9e47d4fb1cdaa89a1c5783d68363c4dbc4b524ed3d857148617feffffff02836d3c01000000001976a914fc25d6d5c94003bf5b0c7b640a248e2c637fcfb088ac7ada8202000000001976a914fbed3d9b11183209a57999d54d59f67c019e756c88ac6acb0700",
            0, 0
        ).unwrap();

        // a random segwit transaction from the blockchain using P2SH
        verify_test (
            "a91434c06f8c87e355e123bdc6dda4ffabc64b6989ef87",
            "01000000000101d9fd94d0ff0026d307c994d0003180a5f248146efb6371d040c5973f5f66d9df0400000017160014b31b31a6cb654cfab3c50567bcf124f48a0beaecffffffff012cbd1c000000000017a914233b74bf0823fa58bbbd26dfc3bb4ae715547167870247304402206f60569cac136c114a58aedd80f6fa1c51b49093e7af883e605c212bdafcd8d202200e91a55f408a021ad2631bc29a67bd6915b2d7e9ef0265627eabd7f7234455f6012103e7e802f50344303c76d12c089c8724c1b230e3b745693bbe16aad536293d15e300000000",
            1900000, 0
        ).unwrap();

        // a random segwit transaction from the blockchain using native segwit
        verify_test(
            "0020701a8d401c84fb13e6baf169d59684e17abd9fa216c8cc5b9fc63d622ff8c58d",
            "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",
            18393430 , 0
        ).unwrap();

        // a random old-style transaction from the blockchain - WITH WRONG SIGNATURE for the address
        assert!(verify_test (
            "76a9144bfbaf6afb76cc5771bc6404810d1cc041a6933988ff",
            "02000000013f7cebd65c27431a90bba7f796914fe8cc2ddfc3f2cbd6f7e5f2fc854534da95000000006b483045022100de1ac3bcdfb0332207c4a91f3832bd2c2915840165f876ab47c5f8996b971c3602201c6c053d750fadde599e6f5c4e1963df0f01fc0d97815e8157e3d59fe09ca30d012103699b464d1d8bc9e47d4fb1cdaa89a1c5783d68363c4dbc4b524ed3d857148617feffffff02836d3c01000000001976a914fc25d6d5c94003bf5b0c7b640a248e2c637fcfb088ac7ada8202000000001976a914fbed3d9b11183209a57999d54d59f67c019e756c88ac6acb0700",
            0, 0
        ).is_err());

        // a random segwit transaction from the blockchain using P2SH - WITH WRONG AMOUNT
        assert!(verify_test (
            "a91434c06f8c87e355e123bdc6dda4ffabc64b6989ef87",
            "01000000000101d9fd94d0ff0026d307c994d0003180a5f248146efb6371d040c5973f5f66d9df0400000017160014b31b31a6cb654cfab3c50567bcf124f48a0beaecffffffff012cbd1c000000000017a914233b74bf0823fa58bbbd26dfc3bb4ae715547167870247304402206f60569cac136c114a58aedd80f6fa1c51b49093e7af883e605c212bdafcd8d202200e91a55f408a021ad2631bc29a67bd6915b2d7e9ef0265627eabd7f7234455f6012103e7e802f50344303c76d12c089c8724c1b230e3b745693bbe16aad536293d15e300000000",
            900000, 0).is_err());

        // a random segwit transaction from the blockchain using native segwit - WITH WRONG SEGWIT
        assert!(verify_test(
            "0020701a8d401c84fb13e6baf169d59684e17abd9fa216c8cc5b9fc63d622ff8c58f",
            "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",
            18393430 , 0
        ).is_err());

    }

    fn verify_test (spent : &str, spending :&str, amount :u64, input: usize) -> Result<(),Error> {
        verify (spent.from_hex().unwrap().as_slice(), amount, spending.from_hex().unwrap().as_slice(), input)
    }

    #[test]
    fn invalid_flags_test() {
        verify_with_flags(&[], 0, &[], 0, VERIFY_ALL + 1).unwrap_err();
    }
}