// Bitcoin Dev Kit
// Written in 2020 by Alekos Filini <alekos.filini@gmail.com>
//
// Copyright (c) 2020-2021 Bitcoin Dev Kit Developers
//
// This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
// or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
// You may not use this file except in accordance with one or both of these
// licenses.

use alloc::boxed::Box;
use core::convert::AsRef;
use core::ops::Sub;

use bdk_chain::ConfirmationTime;
use bitcoin::blockdata::transaction::{OutPoint, TxOut};
use bitcoin::{psbt, Weight};

use serde::{Deserialize, Serialize};

/// Types of keychains
#[derive(Serialize, Deserialize, Debug, Clone, Copy, PartialEq, Eq, Hash, Ord, PartialOrd)]
pub enum KeychainKind {
    /// External keychain, used for deriving recipient addresses.
    External = 0,
    /// Internal keychain, used for deriving change addresses.
    Internal = 1,
}

impl KeychainKind {
    /// Return [`KeychainKind`] as a byte
    pub fn as_byte(&self) -> u8 {
        match self {
            KeychainKind::External => b'e',
            KeychainKind::Internal => b'i',
        }
    }
}

impl AsRef<[u8]> for KeychainKind {
    fn as_ref(&self) -> &[u8] {
        match self {
            KeychainKind::External => b"e",
            KeychainKind::Internal => b"i",
        }
    }
}

/// Fee rate
#[derive(Debug, Copy, Clone, PartialEq, PartialOrd)]
// Internally stored as satoshi/vbyte
pub struct FeeRate(f32);

impl FeeRate {
    /// Create a new instance checking the value provided
    ///
    /// ## Panics
    ///
    /// Panics if the value is not [normal](https://doc.rust-lang.org/std/primitive.f32.html#method.is_normal) (except if it's a positive zero) or negative.
    fn new_checked(value: f32) -> Self {
        assert!(value.is_normal() || value == 0.0);
        assert!(value.is_sign_positive());

        FeeRate(value)
    }

    /// Create a new instance of [`FeeRate`] given a float fee rate in sats/kwu
    pub fn from_sat_per_kwu(sat_per_kwu: f32) -> Self {
        FeeRate::new_checked(sat_per_kwu / 250.0_f32)
    }

    /// Create a new instance of [`FeeRate`] given a float fee rate in sats/kvb
    pub fn from_sat_per_kvb(sat_per_kvb: f32) -> Self {
        FeeRate::new_checked(sat_per_kvb / 1000.0_f32)
    }

    /// Create a new instance of [`FeeRate`] given a float fee rate in btc/kvbytes
    ///
    /// ## Panics
    ///
    /// Panics if the value is not [normal](https://doc.rust-lang.org/std/primitive.f32.html#method.is_normal) (except if it's a positive zero) or negative.
    pub fn from_btc_per_kvb(btc_per_kvb: f32) -> Self {
        FeeRate::new_checked(btc_per_kvb * 1e5)
    }

    /// Create a new instance of [`FeeRate`] given a float fee rate in satoshi/vbyte
    ///
    /// ## Panics
    ///
    /// Panics if the value is not [normal](https://doc.rust-lang.org/std/primitive.f32.html#method.is_normal) (except if it's a positive zero) or negative.
    pub fn from_sat_per_vb(sat_per_vb: f32) -> Self {
        FeeRate::new_checked(sat_per_vb)
    }

    /// Create a new [`FeeRate`] with the default min relay fee value
    pub const fn default_min_relay_fee() -> Self {
        FeeRate(1.0)
    }

    /// Calculate fee rate from `fee` and weight units (`wu`).
    pub fn from_wu(fee: u64, wu: Weight) -> FeeRate {
        Self::from_vb(fee, wu.to_vbytes_ceil() as usize)
    }

    /// Calculate fee rate from `fee` and `vbytes`.
    pub fn from_vb(fee: u64, vbytes: usize) -> FeeRate {
        let rate = fee as f32 / vbytes as f32;
        Self::from_sat_per_vb(rate)
    }

    /// Return the value as satoshi/vbyte
    pub fn as_sat_per_vb(&self) -> f32 {
        self.0
    }

    /// Return the value as satoshi/kwu
    pub fn sat_per_kwu(&self) -> f32 {
        self.0 * 250.0_f32
    }

    /// Calculate absolute fee in Satoshis using size in weight units.
    pub fn fee_wu(&self, wu: Weight) -> u64 {
        self.fee_vb(wu.to_vbytes_ceil() as usize)
    }

    /// Calculate absolute fee in Satoshis using size in virtual bytes.
    pub fn fee_vb(&self, vbytes: usize) -> u64 {
        (self.as_sat_per_vb() * vbytes as f32).ceil() as u64
    }
}

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

impl Sub for FeeRate {
    type Output = Self;

    fn sub(self, other: FeeRate) -> Self::Output {
        FeeRate(self.0 - other.0)
    }
}

/// Trait implemented by types that can be used to measure weight units.
pub trait Vbytes {
    /// Convert weight units to virtual bytes.
    fn vbytes(self) -> usize;
}

impl Vbytes for usize {
    fn vbytes(self) -> usize {
        // ref: https://github.com/bitcoin/bips/blob/master/bip-0141.mediawiki#transaction-size-calculations
        (self as f32 / 4.0).ceil() as usize
    }
}

/// An unspent output owned by a [`Wallet`].
///
/// [`Wallet`]: crate::Wallet
#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq, Hash)]
pub struct LocalUtxo {
    /// Reference to a transaction output
    pub outpoint: OutPoint,
    /// Transaction output
    pub txout: TxOut,
    /// Type of keychain
    pub keychain: KeychainKind,
    /// Whether this UTXO is spent or not
    pub is_spent: bool,
    /// The derivation index for the script pubkey in the wallet
    pub derivation_index: u32,
    /// The confirmation time for transaction containing this utxo
    pub confirmation_time: ConfirmationTime,
}

/// A [`Utxo`] with its `satisfaction_weight`.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct WeightedUtxo {
    /// The weight of the witness data and `scriptSig` expressed in [weight units]. This is used to
    /// properly maintain the feerate when adding this input to a transaction during coin selection.
    ///
    /// [weight units]: https://en.bitcoin.it/wiki/Weight_units
    pub satisfaction_weight: usize,
    /// The UTXO
    pub utxo: Utxo,
}

#[derive(Debug, Clone, PartialEq, Eq)]
/// An unspent transaction output (UTXO).
pub enum Utxo {
    /// A UTXO owned by the local wallet.
    Local(LocalUtxo),
    /// A UTXO owned by another wallet.
    Foreign {
        /// The location of the output.
        outpoint: OutPoint,
        /// The information about the input we require to add it to a PSBT.
        // Box it to stop the type being too big.
        psbt_input: Box<psbt::Input>,
    },
}

impl Utxo {
    /// Get the location of the UTXO
    pub fn outpoint(&self) -> OutPoint {
        match &self {
            Utxo::Local(local) => local.outpoint,
            Utxo::Foreign { outpoint, .. } => *outpoint,
        }
    }

    /// Get the `TxOut` of the UTXO
    pub fn txout(&self) -> &TxOut {
        match &self {
            Utxo::Local(local) => &local.txout,
            Utxo::Foreign {
                outpoint,
                psbt_input,
            } => {
                if let Some(prev_tx) = &psbt_input.non_witness_utxo {
                    return &prev_tx.output[outpoint.vout as usize];
                }

                if let Some(txout) = &psbt_input.witness_utxo {
                    return txout;
                }

                unreachable!("Foreign UTXOs will always have one of these set")
            }
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn can_store_feerate_in_const() {
        const _MIN_RELAY: FeeRate = FeeRate::default_min_relay_fee();
    }

    #[test]
    #[should_panic]
    fn test_invalid_feerate_neg_zero() {
        let _ = FeeRate::from_sat_per_vb(-0.0);
    }

    #[test]
    #[should_panic]
    fn test_invalid_feerate_neg_value() {
        let _ = FeeRate::from_sat_per_vb(-5.0);
    }

    #[test]
    #[should_panic]
    fn test_invalid_feerate_nan() {
        let _ = FeeRate::from_sat_per_vb(f32::NAN);
    }

    #[test]
    #[should_panic]
    fn test_invalid_feerate_inf() {
        let _ = FeeRate::from_sat_per_vb(f32::INFINITY);
    }

    #[test]
    fn test_valid_feerate_pos_zero() {
        let _ = FeeRate::from_sat_per_vb(0.0);
    }

    #[test]
    fn test_fee_from_btc_per_kvb() {
        let fee = FeeRate::from_btc_per_kvb(1e-5);
        assert!((fee.as_sat_per_vb() - 1.0).abs() < f32::EPSILON);
    }

    #[test]
    fn test_fee_from_sat_per_vbyte() {
        let fee = FeeRate::from_sat_per_vb(1.0);
        assert!((fee.as_sat_per_vb() - 1.0).abs() < f32::EPSILON);
    }

    #[test]
    fn test_fee_default_min_relay_fee() {
        let fee = FeeRate::default_min_relay_fee();
        assert!((fee.as_sat_per_vb() - 1.0).abs() < f32::EPSILON);
    }

    #[test]
    fn test_fee_from_sat_per_kvb() {
        let fee = FeeRate::from_sat_per_kvb(1000.0);
        assert!((fee.as_sat_per_vb() - 1.0).abs() < f32::EPSILON);
    }

    #[test]
    fn test_fee_from_sat_per_kwu() {
        let fee = FeeRate::from_sat_per_kwu(250.0);
        assert!((fee.as_sat_per_vb() - 1.0).abs() < f32::EPSILON);
        assert_eq!(fee.sat_per_kwu(), 250.0);
    }
}