// Rust Bitcoin Library
// Written in 2014 by
//   Andrew Poelstra <apoelstra@wpsoftware.net>
//
// To the extent possible under law, the author(s) have dedicated all
// copyright and related and neighboring rights to this software to
// the public domain worldwide. This software is distributed without
// any warranty.
//
// You should have received a copy of the CC0 Public Domain Dedication
// along with this software.
// If not, see <http://creativecommons.org/publicdomain/zero/1.0/>.
//

//! # Bitcoin Transaction
//!
//! A transaction describes a transfer of money. It consumes previously-unspent
//! transaction outputs and produces new ones, satisfying the condition to spend
//! the old outputs (typically a digital signature with a specific key must be
//! provided) and defining the condition to spend the new ones. The use of digital
//! signatures ensures that coins cannot be spent by unauthorized parties.
//!
//! This module provides the structures and functions needed to support transactions.
//!

use std::default::Default;
use serialize::json;

use util::hash::Sha256dHash;
use blockdata::script::{self, Script, ScriptError, ScriptTrace, read_scriptbool};
use blockdata::utxoset::UtxoSet;
use network::encodable::ConsensusEncodable;
use network::serialize::BitcoinHash;
use network::constants::Network;
use wallet::address::Address;

/// A transaction input, which defines old coins to be consumed
#[deriving(Clone, PartialEq, Eq, Show)]
pub struct TxIn {
  /// The hash of the transaction whose output is being used an an input
  pub prev_hash: Sha256dHash,
  /// The index of the output in the previous transaction, which may have several
  pub prev_index: u32,
  /// The script which pushes values on the stack which will cause
  /// the referenced output's script to accept
  pub script_sig: Script,
  /// The sequence number, which suggests to miners which of two
  /// conflicting transactions should be preferred, or 0xFFFFFFFF
  /// to ignore this feature. This is generally never used since
  /// the miner behaviour cannot be enforced.
  pub sequence: u32,
}

/// A transaction output, which defines new coins to be created from old ones.
#[deriving(Clone, PartialEq, Eq, Show)]
pub struct TxOut {
  /// The value of the output, in satoshis
  pub value: u64,
  /// The script which must satisfy for the output to be spent
  pub script_pubkey: Script
}

// This is used as a "null txout" in consensus signing code
impl Default for TxOut {
  fn default() -> TxOut {
    TxOut { value: 0xffffffffffffffff, script_pubkey: Script::new() }
  }
}

/// A classification for script pubkeys 
pub enum ScriptPubkeyTemplate {
  /// A pay-to-address output
  PayToPubkeyHash(Address),
  /// Another kind of output
  Unknown
}

impl TxOut {
  /// Determines the template that this output adheres to, if any
  pub fn classify(&self, network: Network) -> ScriptPubkeyTemplate {
    if self.script_pubkey.len() == 25 &&
       self.script_pubkey.slice_to(3) == &[0x76, 0xa9, 0x14] &&
       self.script_pubkey.slice_from(23) == &[0x88, 0xac] {
      PayToPubkeyHash(self.script_pubkey.slice(3, 23).to_address(network))
    } else {
      Unknown
    }
  }
}

/// A Bitcoin transaction, which describes an authenticated movement of coins
#[deriving(Clone, PartialEq, Eq, Show)]
pub struct Transaction {
  /// The protocol version, should always be 1.
  pub version: u32,
  /// Block number before which this transaction is valid, or 0 for
  /// valid immediately.
  pub lock_time: u32,
  /// List of inputs
  pub input: Vec<TxIn>,
  /// List of outputs
  pub output: Vec<TxOut>
}

/// A transaction error
#[deriving(PartialEq, Eq, Clone, Show)]
pub enum TransactionError {
  /// Concatenated script failed in the input half (script error)
  InputScriptFailure(ScriptError),
  /// Concatenated script failed in the output half (script error)
  OutputScriptFailure(ScriptError),
  /// P2SH serialized script failed (script error)
  P2shScriptFailure(ScriptError),
  /// P2SH serialized script ended with false at the top of the stack 
  P2shScriptReturnedFalse,
  /// P2SH serialized script ended with nothing in the stack
  P2shScriptReturnedEmptyStack,
  /// Script ended with false at the top of the stack 
  ScriptReturnedFalse,
  /// Script ended with nothing in the stack
  ScriptReturnedEmptyStack,
  /// Script ended with nothing in the stack (input txid, input vout)
  InputNotFound(Sha256dHash, u32),
}

impl json::ToJson for TransactionError {
  fn to_json(&self) -> json::Json {
    json::String(self.to_string())
  }
}

/// A trace of a transaction input's script execution
#[deriving(PartialEq, Eq, Clone, Show)]
pub struct InputTrace {
  input_txid: Sha256dHash,
  input_vout: usize,
  sig_trace: ScriptTrace,
  pubkey_trace: Option<ScriptTrace>,
  p2sh_trace: Option<ScriptTrace>,
  error: Option<TransactionError>
}

impl_json!(ScriptTrace, script, initial_stack, iterations, error);
impl_json!(InputTrace, input_txid, input_vout, sig_trace,
                       pubkey_trace, p2sh_trace, error);

/// A trace of a transaction's execution
#[deriving(PartialEq, Eq, Clone, Show)]
pub struct TransactionTrace {
  txid: Sha256dHash,
  inputs: Vec<InputTrace>
}

impl_json!(TransactionTrace, txid, inputs);

impl TxIn {
  /// Check an input's script for validity
  pub fn validate(&self,
                  utxoset: &UtxoSet,
                  txn: &Transaction,
                  index: usize) -> Result<(), TransactionError> {
    let txo = utxoset.get_utxo(self.prev_hash, self.prev_index);
    match txo {
      Some((_, txo)) => {
        let mut p2sh_stack = Vec::new();
        let mut p2sh_script = Script::new();

        let mut stack = Vec::with_capacity(6);
        match self.script_sig.evaluate(&mut stack, Some((txn, index)), None) {
          Ok(_) => {}
          Err(e) => { return Err(InputScriptFailure(e)); }
        }
        if txo.script_pubkey.is_p2sh() && stack.len() > 0 {
          p2sh_stack = stack.clone();
          p2sh_script = match p2sh_stack.pop() {
            Some(script::Owned(v)) => Script::from_vec(v),
            Some(script::Borrowed(s)) => Script::from_vec(s.to_vec()),
            None => unreachable!()
          };
        }
        match txo.script_pubkey.evaluate(&mut stack, Some((txn, index)), None) {
          Ok(_) => {}
          Err(e) => { return Err(OutputScriptFailure(e)); }
        }
        match stack.pop() {
          Some(v) => {
            if !read_scriptbool(v.as_slice()) {
              return Err(ScriptReturnedFalse);
            }
           }
          None => { return Err(ScriptReturnedEmptyStack); }
        }
        if txo.script_pubkey.is_p2sh() {
          match p2sh_script.evaluate(&mut p2sh_stack, Some((txn, index)), None) {
            Ok(_) => {}
            Err(e) => { return Err(P2shScriptFailure(e)); }
          }
          match p2sh_stack.pop() {
            Some(v) => {
              if !read_scriptbool(v.as_slice()) {
                return Err(P2shScriptReturnedFalse);
              }
            }
            None => { return Err(P2shScriptReturnedEmptyStack); }
          }
        }
      }
      None => { return Err(InputNotFound(self.prev_hash, self.prev_index)); }
    }
    Ok(())
  }
}

impl Transaction {
  /// Check a transaction for validity
  pub fn validate(&self, utxoset: &UtxoSet) -> Result<(), TransactionError> {
    for (n, input) in self.input.iter().enumerate() {
      try!(input.validate(utxoset, self, n));
    }
    Ok(())
  }

  /// Produce a trace of a transaction's execution
  pub fn trace(&self, utxoset: &UtxoSet) -> TransactionTrace {
    let mut ret = TransactionTrace { txid: self.bitcoin_hash(),
                                     inputs: Vec::with_capacity(self.input.len()) };
    for (n, input) in self.input.iter().enumerate() {
      // Setup trace
      let mut trace = InputTrace {
        input_txid: input.prev_hash,
        input_vout: input.prev_index as usize,
        sig_trace: ScriptTrace {
          script: Script::new(),
          initial_stack: vec![],
          iterations: vec![],
          error: None
        },
        pubkey_trace: None,
        p2sh_trace: None,
        error: None
      };
      // Run through the input
      let txo = utxoset.get_utxo(input.prev_hash, input.prev_index);
      match txo {
        Some((_, txo)) => {
          let mut p2sh_stack = Vec::new();
          let mut p2sh_script = Script::new();

          let mut stack = Vec::with_capacity(6);
          trace.sig_trace = input.script_sig.trace(&mut stack, Some((self, n)));
          let err = trace.sig_trace.error.as_ref().map(|e| e.clone());
          err.map(|e| trace.error = Some(InputScriptFailure(e)));

          if txo.script_pubkey.is_p2sh() && stack.len() > 0 {
            p2sh_stack = stack.clone();
            p2sh_script = match p2sh_stack.pop() {
              Some(script::Owned(v)) => Script::from_vec(v),
              Some(script::Borrowed(s)) => Script::from_vec(s.to_vec()),
              None => unreachable!()
            };
          }
          if trace.error.is_none() {
            trace.pubkey_trace = Some(txo.script_pubkey.trace(&mut stack, Some((self, n))));
            let err = trace.pubkey_trace.as_ref().unwrap().error.as_ref().map(|e| e.clone());
            err.map(|e| trace.error = Some(OutputScriptFailure(e)));
            match stack.pop() {
              Some(v) => {
                if !read_scriptbool(v.as_slice()) {
                  trace.error = Some(ScriptReturnedFalse);
                }
              }
              None => { trace.error = Some(ScriptReturnedEmptyStack); }
            }
            if trace.error.is_none() && txo.script_pubkey.is_p2sh() {
              trace.p2sh_trace = Some(p2sh_script.trace(&mut p2sh_stack, Some((self, n))));
              let err = trace.p2sh_trace.as_ref().unwrap().error.as_ref().map(|e| e.clone());
              err.map(|e| trace.error = Some(P2shScriptFailure(e)));
              match p2sh_stack.pop() {
                Some(v) => {
                  if !read_scriptbool(v.as_slice()) {
                    trace.error = Some(P2shScriptReturnedFalse);
                  }
                }
                None => { trace.error = Some(P2shScriptReturnedEmptyStack); }
              }
            }
          }
        }
        None => {
          trace.error = Some(InputNotFound(input.prev_hash, input.prev_index));
        }
      }
      ret.inputs.push(trace);
    }
    ret
  }
}

impl BitcoinHash for Transaction {
  fn bitcoin_hash(&self) -> Sha256dHash {
    use network::serialize::serialize;
    Sha256dHash::from_data(serialize(self).unwrap().as_slice())
  }
}

impl_consensus_encoding!(TxIn, prev_hash, prev_index, script_sig, sequence);
impl_json!(TxIn, prev_hash, prev_index, script_sig, sequence);
impl_consensus_encoding!(TxOut, value, script_pubkey);
impl_json!(TxOut, value, script_pubkey);
impl_consensus_encoding!(Transaction, version, input, output, lock_time);
impl_json!(Transaction, version, input, output, lock_time);


#[cfg(test)]
mod tests {
  use super::{Transaction, TxIn};

  use std::io::IoResult;

  use network::serialize::BitcoinHash;
  use network::serialize::deserialize;
  use util::misc::hex_bytes;

  #[test]
  fn test_txin() {
    let txin: IoResult<TxIn> = deserialize(hex_bytes("a15d57094aa7a21a28cb20b59aab8fc7d1149a3bdbcddba9c622e4f5f6a99ece010000006c493046022100f93bb0e7d8db7bd46e40132d1f8242026e045f03a0efe71bbb8e3f475e970d790221009337cd7f1f929f00cc6ff01f03729b069a7c21b59b1736ddfee5db5946c5da8c0121033b9b137ee87d5a812d6f506efdd37f0affa7ffc310711c06c7f3e097c9447c52ffffffff").unwrap());
    assert!(txin.is_ok());
  }

  #[test]
  fn test_transaction() {
    let hex_tx = hex_bytes("0100000001a15d57094aa7a21a28cb20b59aab8fc7d1149a3bdbcddba9c622e4f5f6a99ece010000006c493046022100f93bb0e7d8db7bd46e40132d1f8242026e045f03a0efe71bbb8e3f475e970d790221009337cd7f1f929f00cc6ff01f03729b069a7c21b59b1736ddfee5db5946c5da8c0121033b9b137ee87d5a812d6f506efdd37f0affa7ffc310711c06c7f3e097c9447c52ffffffff0100e1f505000000001976a9140389035a9225b3839e2bbf32d826a1e222031fd888ac00000000").unwrap();
    let tx: IoResult<Transaction> = deserialize(hex_tx);
    assert!(tx.is_ok());
    let realtx = tx.unwrap();
    // All these tests aren't really needed because if they fail, the hash check at the end
    // will also fail. But these will show you where the failure is so I'll leave them in.
    assert_eq!(realtx.version, 1);
    assert_eq!(realtx.input.len(), 1);
    // In particular this one is easy to get backward -- in bitcoin hashes are encoded
    // as little-endian 256-bit numbers rather than as data strings.
    assert_eq!(realtx.input[0].prev_hash.be_hex_string(),
               "ce9ea9f6f5e422c6a9dbcddb3b9a14d1c78fab9ab520cb281aa2a74a09575da1".to_string());
    assert_eq!(realtx.input[0].prev_index, 1);
    assert_eq!(realtx.output.len(), 1);
    assert_eq!(realtx.lock_time, 0);

    assert_eq!(realtx.bitcoin_hash().be_hex_string(),
               "a6eab3c14ab5272a58a5ba91505ba1a4b6d7a3a9fcbd187b6cd99a7b6d548cb7".to_string());
  }
}