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// Magical Bitcoin Library
// Written in 2020 by
//     Alekos Filini <alekos.filini@gmail.com>
//
// Copyright (c) 2020 Magical Bitcoin
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

//! Transaction builder
//!
//! ## Example
//!
//! ```
//! # use std::str::FromStr;
//! # use bitcoin::*;
//! # use bdk::*;
//! # use bdk::wallet::tx_builder::CreateTx;
//! # let to_address = Address::from_str("2N4eQYCbKUHCCTUjBJeHcJp9ok6J2GZsTDt").unwrap();
//! # let wallet = doctest_wallet!();
//! // create a TxBuilder from a wallet
//! let mut tx_builder = wallet.build_tx();
//!
//! tx_builder
//!     // Create a transaction with one output to `to_address` of 50_000 satoshi
//!     .add_recipient(to_address.script_pubkey(), 50_000)
//!     // With a custom fee rate of 5.0 satoshi/vbyte
//!     .fee_rate(FeeRate::from_sat_per_vb(5.0))
//!     // Only spend non-change outputs
//!     .do_not_spend_change()
//!     // Turn on RBF signaling
//!     .enable_rbf();
//! let (psbt, tx_details) = tx_builder.finish()?;
//! # Ok::<(), bdk::Error>(())
//! ```

use std::collections::BTreeMap;
use std::collections::HashSet;
use std::default::Default;
use std::marker::PhantomData;

use bitcoin::util::psbt::PartiallySignedTransaction as PSBT;
use bitcoin::{OutPoint, Script, SigHashType, Transaction};

use miniscript::descriptor::DescriptorTrait;

use super::coin_selection::{CoinSelectionAlgorithm, DefaultCoinSelectionAlgorithm};
use crate::{database::BatchDatabase, Error, Wallet};
use crate::{
    types::{FeeRate, KeychainKind, UTXO},
    TransactionDetails,
};
/// Context in which the [`TxBuilder`] is valid
pub trait TxBuilderContext: std::fmt::Debug + Default + Clone {}

/// Marker type to indicate the [`TxBuilder`] is being used to create a new transaction (as opposed
/// to bumping the fee of an existing one).
#[derive(Debug, Default, Clone)]
pub struct CreateTx;
impl TxBuilderContext for CreateTx {}

/// Marker type to indicate the [`TxBuilder`] is being used to bump the fee of an existing transaction.
#[derive(Debug, Default, Clone)]
pub struct BumpFee;
impl TxBuilderContext for BumpFee {}

/// A transaction builder
///
/// A `TxBuilder` is created by calling [`build_tx`] or [`build_fee_bump`] on a wallet. After
/// assigning it, you set options on it until finally calling [`finish`] to consume the builder and
/// generate the transaction.
///
/// Each option setting method on `TxBuilder` takes and returns `&mut self` so you can chain calls
/// as in the following example:
///
/// ```
/// # use bdk::*;
/// # use bdk::wallet::tx_builder::*;
/// # use bitcoin::*;
/// # use core::str::FromStr;
/// # let wallet = doctest_wallet!();
/// # let addr1 = Address::from_str("2N4eQYCbKUHCCTUjBJeHcJp9ok6J2GZsTDt").unwrap();
/// # let addr2 = addr1.clone();
/// // chaining
/// let (psbt1, details) = {
///     let mut builder = wallet.build_tx();
///     builder
///        .ordering(TxOrdering::Untouched)
///        .add_recipient(addr1.script_pubkey(), 50_000)
///        .add_recipient(addr2.script_pubkey(), 50_000);
///     builder.finish()?
/// };
///
/// // non-chaining
/// let (psbt2, details) = {
///     let mut builder = wallet.build_tx();
///     builder.ordering(TxOrdering::Untouched);
///     for addr in &[addr1, addr2] {
///         builder.add_recipient(addr.script_pubkey(), 50_000);
///     }
///     builder.finish()?
/// };
///
/// assert_eq!(psbt1.global.unsigned_tx.output[..2], psbt2.global.unsigned_tx.output[..2]);
/// # Ok::<(), bdk::Error>(())
/// ```
///
/// At the moment [`coin_selection`] is an exception to the rule as it consumes `self`.
/// This means it is usually best to call [`coin_selection`] on the return value of `build_tx` before assigning it.
///
/// For further examples see [this module](super::tx_builder)'s documentation;
///
/// [`build_tx`]: Wallet::build_tx
/// [`build_fee_bump`]: Wallet::build_fee_bump
/// [`finish`]: Self::finish
/// [`coin_selection`]: Self::coin_selection
#[derive(Clone, Debug)]
pub struct TxBuilder<'a, B, D, Cs, Ctx> {
    pub(crate) wallet: &'a Wallet<B, D>,
    // params and coin_selection are Options not becasue they are optionally set (they are always
    // there) but because `.finish()` uses `Option::take` to get an owned value from a &mut self.
    // They are only `None` after `.finish()` is called.
    pub(crate) params: TxParams,
    pub(crate) coin_selection: Cs,
    pub(crate) phantom: PhantomData<Ctx>,
}

/// The parameters for transaction creation sans coin selection algorithm.
//TODO: TxParams should eventually be exposed publicly.
#[derive(Default, Debug, Clone)]
pub(crate) struct TxParams {
    pub(crate) recipients: Vec<(Script, u64)>,
    pub(crate) drain_wallet: bool,
    pub(crate) single_recipient: Option<Script>,
    pub(crate) fee_policy: Option<FeePolicy>,
    pub(crate) internal_policy_path: Option<BTreeMap<String, Vec<usize>>>,
    pub(crate) external_policy_path: Option<BTreeMap<String, Vec<usize>>>,
    pub(crate) utxos: Vec<(UTXO, usize)>,
    pub(crate) unspendable: HashSet<OutPoint>,
    pub(crate) manually_selected_only: bool,
    pub(crate) sighash: Option<SigHashType>,
    pub(crate) ordering: TxOrdering,
    pub(crate) locktime: Option<u32>,
    pub(crate) rbf: Option<RBFValue>,
    pub(crate) version: Option<Version>,
    pub(crate) change_policy: ChangeSpendPolicy,
    pub(crate) force_non_witness_utxo: bool,
    pub(crate) add_global_xpubs: bool,
    pub(crate) include_output_redeem_witness_script: bool,
    pub(crate) bumping_fee: Option<PreviousFee>,
}

#[derive(Clone, Copy, Debug)]
pub(crate) struct PreviousFee {
    pub absolute: u64,
    pub rate: f32,
}

#[derive(Debug, Clone, Copy)]
pub(crate) enum FeePolicy {
    FeeRate(FeeRate),
    FeeAmount(u64),
}

impl std::default::Default for FeePolicy {
    fn default() -> Self {
        FeePolicy::FeeRate(FeeRate::default_min_relay_fee())
    }
}

// methods supported by both contexts, for any CoinSelectionAlgorithm
impl<'a, B, D: BatchDatabase, Cs: CoinSelectionAlgorithm<D>, Ctx: TxBuilderContext>
    TxBuilder<'a, B, D, Cs, Ctx>
{
    /// Set a custom fee rate
    pub fn fee_rate(&mut self, fee_rate: FeeRate) -> &mut Self {
        self.params.fee_policy = Some(FeePolicy::FeeRate(fee_rate));
        self
    }

    /// Set an absolute fee
    pub fn fee_absolute(&mut self, fee_amount: u64) -> &mut Self {
        self.params.fee_policy = Some(FeePolicy::FeeAmount(fee_amount));
        self
    }

    /// Set the policy path to use while creating the transaction for a given keychain.
    ///
    /// This method accepts a map where the key is the policy node id (see
    /// [`Policy::id`](crate::descriptor::Policy::id)) and the value is the list of the indexes of
    /// the items that are intended to be satisfied from the policy node (see
    /// [`SatisfiableItem::Thresh::items`](crate::descriptor::policy::SatisfiableItem::Thresh::items)).
    ///
    /// ## Example
    ///
    /// An example of when the policy path is needed is the following descriptor:
    /// `wsh(thresh(2,pk(A),sj:and_v(v:pk(B),n:older(6)),snj:and_v(v:pk(C),after(630000))))`,
    /// derived from the miniscript policy `thresh(2,pk(A),and(pk(B),older(6)),and(pk(C),after(630000)))`.
    /// It declares three descriptor fragments, and at the top level it uses `thresh()` to
    /// ensure that at least two of them are satisfied. The individual fragments are:
    ///
    /// 1. `pk(A)`
    /// 2. `and(pk(B),older(6))`
    /// 3. `and(pk(C),after(630000))`
    ///
    /// When those conditions are combined in pairs, it's clear that the transaction needs to be created
    /// differently depending on how the user intends to satisfy the policy afterwards:
    ///
    /// * If fragments `1` and `2` are used, the transaction will need to use a specific
    ///   `n_sequence` in order to spend an `OP_CSV` branch.
    /// * If fragments `1` and `3` are used, the transaction will need to use a specific `locktime`
    ///   in order to spend an `OP_CLTV` branch.
    /// * If fragments `2` and `3` are used, the transaction will need both.
    ///
    /// When the spending policy is represented as a tree (see
    /// [`Wallet::policies`](super::Wallet::policies)), every node
    /// is assigned a unique identifier that can be used in the policy path to specify which of
    /// the node's children the user intends to satisfy: for instance, assuming the `thresh()`
    /// root node of this example has an id of `aabbccdd`, the policy path map would look like:
    ///
    /// `{ "aabbccdd" => [0, 1] }`
    ///
    /// where the key is the node's id, and the value is a list of the children that should be
    /// used, in no particular order.
    ///
    /// If a particularly complex descriptor has multiple ambiguous thresholds in its structure,
    /// multiple entries can be added to the map, one for each node that requires an explicit path.
    ///
    /// ```
    /// # use std::str::FromStr;
    /// # use std::collections::BTreeMap;
    /// # use bitcoin::*;
    /// # use bdk::*;
    /// # let to_address = Address::from_str("2N4eQYCbKUHCCTUjBJeHcJp9ok6J2GZsTDt").unwrap();
    /// # let wallet = doctest_wallet!();
    /// let mut path = BTreeMap::new();
    /// path.insert("aabbccdd".to_string(), vec![0, 1]);
    ///
    /// let builder = wallet.build_tx()
    ///     .add_recipient(to_address.script_pubkey(), 50_000)
    ///     .policy_path(path, KeychainKind::External);
    ///
    /// # Ok::<(), bdk::Error>(())
    /// ```
    pub fn policy_path(
        &mut self,
        policy_path: BTreeMap<String, Vec<usize>>,
        keychain: KeychainKind,
    ) -> &mut Self {
        let to_update = match keychain {
            KeychainKind::Internal => &mut self.params.internal_policy_path,
            KeychainKind::External => &mut self.params.external_policy_path,
        };

        *to_update = Some(policy_path);
        self
    }

    /// Add the list of outpoints to the internal list of UTXOs that **must** be spent.
    ///
    /// If an error occurs while adding any of the UTXOs then none of them are added and the error is returned.
    ///
    /// These have priority over the "unspendable" utxos, meaning that if a utxo is present both in
    /// the "utxos" and the "unspendable" list, it will be spent.
    pub fn add_utxos(&mut self, outpoints: &[OutPoint]) -> Result<&mut Self, Error> {
        let utxos = outpoints
            .iter()
            .map(|outpoint| self.wallet.get_utxo(*outpoint)?.ok_or(Error::UnknownUTXO))
            .collect::<Result<Vec<_>, _>>()?;

        for utxo in utxos {
            let descriptor = self.wallet.get_descriptor_for_keychain(utxo.keychain);
            let satisfaction_weight = descriptor.max_satisfaction_weight().unwrap();
            self.params.utxos.push((utxo, satisfaction_weight));
        }

        Ok(self)
    }

    /// Add a utxo to the internal list of utxos that **must** be spent
    ///
    /// These have priority over the "unspendable" utxos, meaning that if a utxo is present both in
    /// the "utxos" and the "unspendable" list, it will be spent.
    pub fn add_utxo(&mut self, outpoint: OutPoint) -> Result<&mut Self, Error> {
        self.add_utxos(&[outpoint])
    }

    /// Only spend utxos added by [`add_utxo`].
    ///
    /// The wallet will **not** add additional utxos to the transaction even if they are needed to
    /// make the transaction valid.
    ///
    /// [`add_utxo`]: Self::add_utxo
    pub fn manually_selected_only(&mut self) -> &mut Self {
        self.params.manually_selected_only = true;
        self
    }

    /// Replace the internal list of unspendable utxos with a new list
    ///
    /// It's important to note that the "must-be-spent" utxos added with [`TxBuilder::add_utxo`]
    /// have priority over these. See the docs of the two linked methods for more details.
    pub fn unspendable(&mut self, unspendable: Vec<OutPoint>) -> &mut Self {
        self.params.unspendable = unspendable.into_iter().collect();
        self
    }

    /// Add a utxo to the internal list of unspendable utxos
    ///
    /// It's important to note that the "must-be-spent" utxos added with [`TxBuilder::add_utxo`]
    /// have priority over this. See the docs of the two linked methods for more details.
    pub fn add_unspendable(&mut self, unspendable: OutPoint) -> &mut Self {
        self.params.unspendable.insert(unspendable);
        self
    }

    /// Sign with a specific sig hash
    ///
    /// **Use this option very carefully**
    pub fn sighash(&mut self, sighash: SigHashType) -> &mut Self {
        self.params.sighash = Some(sighash);
        self
    }

    /// Choose the ordering for inputs and outputs of the transaction
    pub fn ordering(&mut self, ordering: TxOrdering) -> &mut Self {
        self.params.ordering = ordering;
        self
    }

    /// Use a specific nLockTime while creating the transaction
    ///
    /// This can cause conflicts if the wallet's descriptors contain an "after" (OP_CLTV) operator.
    pub fn nlocktime(&mut self, locktime: u32) -> &mut Self {
        self.params.locktime = Some(locktime);
        self
    }

    /// Build a transaction with a specific version
    ///
    /// The `version` should always be greater than `0` and greater than `1` if the wallet's
    /// descriptors contain an "older" (OP_CSV) operator.
    pub fn version(&mut self, version: i32) -> &mut Self {
        self.params.version = Some(Version(version));
        self
    }

    /// Do not spend change outputs
    ///
    /// This effectively adds all the change outputs to the "unspendable" list. See
    /// [`TxBuilder::unspendable`].
    pub fn do_not_spend_change(&mut self) -> &mut Self {
        self.params.change_policy = ChangeSpendPolicy::ChangeForbidden;
        self
    }

    /// Only spend change outputs
    ///
    /// This effectively adds all the non-change outputs to the "unspendable" list. See
    /// [`TxBuilder::unspendable`].
    pub fn only_spend_change(&mut self) -> &mut Self {
        self.params.change_policy = ChangeSpendPolicy::OnlyChange;
        self
    }

    /// Set a specific [`ChangeSpendPolicy`]. See [`TxBuilder::do_not_spend_change`] and
    /// [`TxBuilder::only_spend_change`] for some shortcuts.
    pub fn change_policy(&mut self, change_policy: ChangeSpendPolicy) -> &mut Self {
        self.params.change_policy = change_policy;
        self
    }

    /// Fill-in the [`psbt::Input::non_witness_utxo`](bitcoin::util::psbt::Input::non_witness_utxo) field even if the wallet only has SegWit
    /// descriptors.
    ///
    /// This is useful for signers which always require it, like Trezor hardware wallets.
    pub fn force_non_witness_utxo(&mut self) -> &mut Self {
        self.params.force_non_witness_utxo = true;
        self
    }

    /// Fill-in the [`psbt::Output::redeem_script`](bitcoin::util::psbt::Output::redeem_script) and
    /// [`psbt::Output::witness_script`](bitcoin::util::psbt::Output::witness_script) fields.
    ///
    /// This is useful for signers which always require it, like ColdCard hardware wallets.
    pub fn include_output_redeem_witness_script(&mut self) -> &mut Self {
        self.params.include_output_redeem_witness_script = true;
        self
    }

    /// Fill-in the `PSBT_GLOBAL_XPUB` field with the extended keys contained in both the external
    /// and internal descriptors
    ///
    /// This is useful for offline signers that take part to a multisig. Some hardware wallets like
    /// BitBox and ColdCard are known to require this.
    pub fn add_global_xpubs(&mut self) -> &mut Self {
        self.params.add_global_xpubs = true;
        self
    }

    /// Spend all the available inputs. This respects filters like [`TxBuilder::unspendable`] and the change policy.
    pub fn drain_wallet(&mut self) -> &mut Self {
        self.params.drain_wallet = true;
        self
    }

    /// Choose the coin selection algorithm
    ///
    /// Overrides the [`DefaultCoinSelectionAlgorithm`](super::coin_selection::DefaultCoinSelectionAlgorithm).
    ///
    /// Note that this function consumes the builder and returns it so it is usually best to put this as the first call on the builder.
    pub fn coin_selection<P: CoinSelectionAlgorithm<D>>(
        self,
        coin_selection: P,
    ) -> TxBuilder<'a, B, D, P, Ctx> {
        TxBuilder {
            wallet: self.wallet,
            params: self.params,
            coin_selection,
            phantom: PhantomData,
        }
    }

    /// Finish the building the transaction.
    ///
    /// Returns the [`BIP174`] "PSBT" and summary details about the transaction.
    ///
    /// [`BIP174`]: https://github.com/bitcoin/bips/blob/master/bip-0174.mediawiki
    pub fn finish(self) -> Result<(PSBT, TransactionDetails), Error> {
        self.wallet.create_tx(self.coin_selection, self.params)
    }
}

impl<'a, B, D: BatchDatabase, Cs: CoinSelectionAlgorithm<D>> TxBuilder<'a, B, D, Cs, CreateTx> {
    /// Replace the recipients already added with a new list
    pub fn set_recipients(&mut self, recipients: Vec<(Script, u64)>) -> &mut Self {
        self.params.recipients = recipients;
        self
    }

    /// Add a recipient to the internal list
    pub fn add_recipient(&mut self, script_pubkey: Script, amount: u64) -> &mut Self {
        self.params.recipients.push((script_pubkey, amount));
        self
    }

    /// Set a single recipient that will get all the selected funds minus the fee. No change will
    /// be created
    ///
    /// This method overrides any recipient set with [`set_recipients`](Self::set_recipients) or
    /// [`add_recipient`](Self::add_recipient).
    ///
    /// It can only be used in conjunction with [`drain_wallet`](Self::drain_wallet) to send the
    /// entire content of the wallet (minus filters) to a single recipient or with a
    /// list of manually selected UTXOs by enabling [`manually_selected_only`](Self::manually_selected_only)
    /// and selecting them with or [`add_utxo`](Self::add_utxo).
    ///
    /// When bumping the fees of a transaction made with this option, the user should remeber to
    /// add [`maintain_single_recipient`](Self::maintain_single_recipient) to correctly update the
    /// single output instead of adding one more for the change.
    pub fn set_single_recipient(&mut self, recipient: Script) -> &mut Self {
        self.params.single_recipient = Some(recipient);
        self.params.recipients.clear();

        self
    }

    /// Enable signaling RBF
    ///
    /// This will use the default nSequence value of `0xFFFFFFFD`.
    pub fn enable_rbf(&mut self) -> &mut Self {
        self.params.rbf = Some(RBFValue::Default);
        self
    }

    /// Enable signaling RBF with a specific nSequence value
    ///
    /// This can cause conflicts if the wallet's descriptors contain an "older" (OP_CSV) operator
    /// and the given `nsequence` is lower than the CSV value.
    ///
    /// If the `nsequence` is higher than `0xFFFFFFFD` an error will be thrown, since it would not
    /// be a valid nSequence to signal RBF.
    pub fn enable_rbf_with_sequence(&mut self, nsequence: u32) -> &mut Self {
        self.params.rbf = Some(RBFValue::Value(nsequence));
        self
    }
}

// methods supported only by bump_fee
impl<'a, B, D: BatchDatabase> TxBuilder<'a, B, D, DefaultCoinSelectionAlgorithm, BumpFee> {
    /// Bump the fees of a transaction made with [`set_single_recipient`](Self::set_single_recipient)
    ///
    /// Unless extra inputs are specified with [`add_utxo`], this flag will make
    /// `bump_fee` reduce the value of the existing output, or fail if it would be consumed
    /// entirely given the higher new fee rate.
    ///
    /// If extra inputs are added and they are not entirely consumed in fees, a change output will not
    /// be added; the existing output will simply grow in value.
    ///
    /// Fails if the transaction has more than one outputs.
    ///
    /// [`add_utxo`]: Self::add_utxo
    pub fn maintain_single_recipient(&mut self) -> Result<&mut Self, Error> {
        let mut recipients = self.params.recipients.drain(..).collect::<Vec<_>>();
        if recipients.len() != 1 {
            return Err(Error::SingleRecipientMultipleOutputs);
        }
        self.params.single_recipient = Some(recipients.pop().unwrap().0);
        Ok(self)
    }
}

/// Ordering of the transaction's inputs and outputs
#[derive(Debug, Ord, PartialOrd, Eq, PartialEq, Hash, Clone, Copy)]
pub enum TxOrdering {
    /// Randomized (default)
    Shuffle,
    /// Unchanged
    Untouched,
    /// BIP69 / Lexicographic
    BIP69Lexicographic,
}

impl Default for TxOrdering {
    fn default() -> Self {
        TxOrdering::Shuffle
    }
}

impl TxOrdering {
    /// Sort transaction inputs and outputs by [`TxOrdering`] variant
    pub fn sort_tx(&self, tx: &mut Transaction) {
        match self {
            TxOrdering::Untouched => {}
            TxOrdering::Shuffle => {
                use rand::seq::SliceRandom;
                #[cfg(test)]
                use rand::SeedableRng;

                #[cfg(not(test))]
                let mut rng = rand::thread_rng();
                #[cfg(test)]
                let mut rng = rand::rngs::StdRng::seed_from_u64(0);

                tx.output.shuffle(&mut rng);
            }
            TxOrdering::BIP69Lexicographic => {
                tx.input.sort_unstable_by_key(|txin| {
                    (txin.previous_output.txid, txin.previous_output.vout)
                });
                tx.output
                    .sort_unstable_by_key(|txout| (txout.value, txout.script_pubkey.clone()));
            }
        }
    }
}

/// Transaction version
///
/// Has a default value of `1`
#[derive(Debug, Ord, PartialOrd, Eq, PartialEq, Hash, Clone, Copy)]
pub(crate) struct Version(pub(crate) i32);

impl Default for Version {
    fn default() -> Self {
        Version(1)
    }
}

/// RBF nSequence value
///
/// Has a default value of `0xFFFFFFFD`
#[derive(Debug, Ord, PartialOrd, Eq, PartialEq, Hash, Clone, Copy)]
pub(crate) enum RBFValue {
    Default,
    Value(u32),
}

impl RBFValue {
    pub(crate) fn get_value(&self) -> u32 {
        match self {
            RBFValue::Default => 0xFFFFFFFD,
            RBFValue::Value(v) => *v,
        }
    }
}

/// Policy regarding the use of change outputs when creating a transaction
#[derive(Debug, Ord, PartialOrd, Eq, PartialEq, Hash, Clone, Copy)]
pub enum ChangeSpendPolicy {
    /// Use both change and non-change outputs (default)
    ChangeAllowed,
    /// Only use change outputs (see [`TxBuilder::only_spend_change`])
    OnlyChange,
    /// Only use non-change outputs (see [`TxBuilder::do_not_spend_change`])
    ChangeForbidden,
}

impl Default for ChangeSpendPolicy {
    fn default() -> Self {
        ChangeSpendPolicy::ChangeAllowed
    }
}

impl ChangeSpendPolicy {
    pub(crate) fn is_satisfied_by(&self, utxo: &UTXO) -> bool {
        match self {
            ChangeSpendPolicy::ChangeAllowed => true,
            ChangeSpendPolicy::OnlyChange => utxo.keychain == KeychainKind::Internal,
            ChangeSpendPolicy::ChangeForbidden => utxo.keychain == KeychainKind::External,
        }
    }
}

#[cfg(test)]
mod test {
    const ORDERING_TEST_TX: &'static str = "0200000003c26f3eb7932f7acddc5ddd26602b77e7516079b03090a16e2c2f54\
                                            85d1fd600f0100000000ffffffffc26f3eb7932f7acddc5ddd26602b77e75160\
                                            79b03090a16e2c2f5485d1fd600f0000000000ffffffff571fb3e02278217852\
                                            dd5d299947e2b7354a639adc32ec1fa7b82cfb5dec530e0500000000ffffffff\
                                            03e80300000000000002aaeee80300000000000001aa200300000000000001ff\
                                            00000000";
    macro_rules! ordering_test_tx {
        () => {
            deserialize::<bitcoin::Transaction>(&Vec::<u8>::from_hex(ORDERING_TEST_TX).unwrap())
                .unwrap()
        };
    }

    use bitcoin::consensus::deserialize;
    use bitcoin::hashes::hex::FromHex;

    use super::*;

    #[test]
    fn test_output_ordering_default_shuffle() {
        assert_eq!(TxOrdering::default(), TxOrdering::Shuffle);
    }

    #[test]
    fn test_output_ordering_untouched() {
        let original_tx = ordering_test_tx!();
        let mut tx = original_tx.clone();

        TxOrdering::Untouched.sort_tx(&mut tx);

        assert_eq!(original_tx, tx);
    }

    #[test]
    fn test_output_ordering_shuffle() {
        let original_tx = ordering_test_tx!();
        let mut tx = original_tx.clone();

        TxOrdering::Shuffle.sort_tx(&mut tx);

        assert_eq!(original_tx.input, tx.input);
        assert_ne!(original_tx.output, tx.output);
    }

    #[test]
    fn test_output_ordering_bip69() {
        use std::str::FromStr;

        let original_tx = ordering_test_tx!();
        let mut tx = original_tx.clone();

        TxOrdering::BIP69Lexicographic.sort_tx(&mut tx);

        assert_eq!(
            tx.input[0].previous_output,
            bitcoin::OutPoint::from_str(
                "0e53ec5dfb2cb8a71fec32dc9a634a35b7e24799295ddd5278217822e0b31f57:5"
            )
            .unwrap()
        );
        assert_eq!(
            tx.input[1].previous_output,
            bitcoin::OutPoint::from_str(
                "0f60fdd185542f2c6ea19030b0796051e7772b6026dd5ddccd7a2f93b73e6fc2:0"
            )
            .unwrap()
        );
        assert_eq!(
            tx.input[2].previous_output,
            bitcoin::OutPoint::from_str(
                "0f60fdd185542f2c6ea19030b0796051e7772b6026dd5ddccd7a2f93b73e6fc2:1"
            )
            .unwrap()
        );

        assert_eq!(tx.output[0].value, 800);
        assert_eq!(tx.output[1].script_pubkey, From::from(vec![0xAA]));
        assert_eq!(tx.output[2].script_pubkey, From::from(vec![0xAA, 0xEE]));
    }

    fn get_test_utxos() -> Vec<UTXO> {
        vec![
            UTXO {
                outpoint: OutPoint {
                    txid: Default::default(),
                    vout: 0,
                },
                txout: Default::default(),
                keychain: KeychainKind::External,
            },
            UTXO {
                outpoint: OutPoint {
                    txid: Default::default(),
                    vout: 1,
                },
                txout: Default::default(),
                keychain: KeychainKind::Internal,
            },
        ]
    }

    #[test]
    fn test_change_spend_policy_default() {
        let change_spend_policy = ChangeSpendPolicy::default();
        let filtered = get_test_utxos()
            .into_iter()
            .filter(|u| change_spend_policy.is_satisfied_by(u))
            .collect::<Vec<_>>();

        assert_eq!(filtered.len(), 2);
    }

    #[test]
    fn test_change_spend_policy_no_internal() {
        let change_spend_policy = ChangeSpendPolicy::ChangeForbidden;
        let filtered = get_test_utxos()
            .into_iter()
            .filter(|u| change_spend_policy.is_satisfied_by(u))
            .collect::<Vec<_>>();

        assert_eq!(filtered.len(), 1);
        assert_eq!(filtered[0].keychain, KeychainKind::External);
    }

    #[test]
    fn test_change_spend_policy_only_internal() {
        let change_spend_policy = ChangeSpendPolicy::OnlyChange;
        let filtered = get_test_utxos()
            .into_iter()
            .filter(|u| change_spend_policy.is_satisfied_by(u))
            .collect::<Vec<_>>();

        assert_eq!(filtered.len(), 1);
        assert_eq!(filtered[0].keychain, KeychainKind::Internal);
    }

    #[test]
    fn test_default_tx_version_1() {
        let version = Version::default();
        assert_eq!(version.0, 1);
    }
}