use fuel_crypto::Hasher;
use fuel_types::bytes;
use fuel_types::{Address, AssetId, Bytes32, ContractId, MessageId, Word};

use core::mem;

#[cfg(feature = "std")]
use fuel_types::bytes::{SizedBytes, WORD_SIZE};

#[cfg(feature = "std")]
use std::io;

mod consts;
mod repr;

use consts::*;

pub use repr::OutputRepr;

#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub enum Output {
    Coin {
        to: Address,
        amount: Word,
        asset_id: AssetId,
    },

    Contract {
        input_index: u8,
        balance_root: Bytes32,
        state_root: Bytes32,
    },

    Message {
        recipient: Address,
        amount: Word,
    },

    Change {
        to: Address,
        amount: Word,
        asset_id: AssetId,
    },

    Variable {
        to: Address,
        amount: Word,
        asset_id: AssetId,
    },

    ContractCreated {
        contract_id: ContractId,
        state_root: Bytes32,
    },
}

impl Default for Output {
    fn default() -> Self {
        Self::ContractCreated {
            contract_id: Default::default(),
            state_root: Default::default(),
        }
    }
}

impl bytes::SizedBytes for Output {
    fn serialized_size(&self) -> usize {
        match self {
            Self::Coin { .. } | Self::Change { .. } | Self::Variable { .. } => OUTPUT_CCV_SIZE,

            Self::Message { .. } => OUTPUT_MESSAGE_SIZE,

            Self::Contract { .. } => OUTPUT_CONTRACT_SIZE,

            Self::ContractCreated { .. } => OUTPUT_CONTRACT_CREATED_SIZE,
        }
    }
}

impl Output {
    pub const fn repr(&self) -> OutputRepr {
        OutputRepr::from_output(self)
    }

    pub const fn coin(to: Address, amount: Word, asset_id: AssetId) -> Self {
        Self::Coin {
            to,
            amount,
            asset_id,
        }
    }

    pub const fn contract(input_index: u8, balance_root: Bytes32, state_root: Bytes32) -> Self {
        Self::Contract {
            input_index,
            balance_root,
            state_root,
        }
    }

    pub const fn message(recipient: Address, amount: Word) -> Self {
        Self::Message { recipient, amount }
    }

    pub const fn change(to: Address, amount: Word, asset_id: AssetId) -> Self {
        Self::Change {
            to,
            amount,
            asset_id,
        }
    }

    pub const fn variable(to: Address, amount: Word, asset_id: AssetId) -> Self {
        Self::Variable {
            to,
            amount,
            asset_id,
        }
    }

    pub const fn contract_created(contract_id: ContractId, state_root: Bytes32) -> Self {
        Self::ContractCreated {
            contract_id,
            state_root,
        }
    }

    pub const fn asset_id(&self) -> Option<&AssetId> {
        match self {
            Output::Coin { asset_id, .. }
            | Output::Change { asset_id, .. }
            | Output::Variable { asset_id, .. } => Some(asset_id),
            _ => None,
        }
    }

    pub const fn to(&self) -> Option<&Address> {
        match self {
            Output::Coin { to, .. } | Output::Change { to, .. } | Output::Variable { to, .. } => {
                Some(to)
            }
            _ => None,
        }
    }

    pub const fn amount(&self) -> Option<Word> {
        match self {
            Output::Coin { amount, .. }
            | Output::Message { amount, .. }
            | Output::Change { amount, .. }
            | Output::Variable { amount, .. } => Some(*amount),
            _ => None,
        }
    }

    pub const fn input_index(&self) -> Option<u8> {
        match self {
            Output::Contract { input_index, .. } => Some(*input_index),
            _ => None,
        }
    }

    pub const fn balance_root(&self) -> Option<&Bytes32> {
        match self {
            Output::Contract { balance_root, .. } => Some(balance_root),
            _ => None,
        }
    }

    pub const fn state_root(&self) -> Option<&Bytes32> {
        match self {
            Output::Contract { state_root, .. } | Output::ContractCreated { state_root, .. } => {
                Some(state_root)
            }
            _ => None,
        }
    }

    pub const fn contract_id(&self) -> Option<&ContractId> {
        match self {
            Output::ContractCreated { contract_id, .. } => Some(contract_id),
            _ => None,
        }
    }

    pub const fn recipient(&self) -> Option<&Address> {
        match self {
            Output::Message { recipient, .. } => Some(recipient),
            _ => None,
        }
    }

    pub const fn is_coin(&self) -> bool {
        matches!(self, Self::Coin { .. })
    }

    pub const fn is_message(&self) -> bool {
        matches!(self, Self::Message { .. })
    }

    pub const fn is_variable(&self) -> bool {
        matches!(self, Self::Variable { .. })
    }

    pub const fn is_contract(&self) -> bool {
        matches!(self, Self::Contract { .. })
    }

    pub const fn is_contract_created(&self) -> bool {
        matches!(self, Self::ContractCreated { .. })
    }

    pub fn message_id(
        sender: &Address,
        recipient: &Address,
        nonce: &Bytes32,
        amount: Word,
        data: &[u8],
    ) -> MessageId {
        let message_id = *Hasher::default()
            .chain(sender)
            .chain(recipient)
            .chain(nonce)
            .chain(amount.to_be_bytes())
            .chain(data)
            .finalize();

        message_id.into()
    }

    pub fn message_nonce(txid: &Bytes32, idx: Word) -> Bytes32 {
        Hasher::default().chain(txid).chain([idx as u8]).finalize()
    }

    pub fn message_digest(data: &[u8]) -> Bytes32 {
        Hasher::hash(data)
    }

    /// Empties fields that should be zero during the signing.
    pub(crate) fn prepare_sign(&mut self) {
        match self {
            Output::Contract {
                balance_root,
                state_root,
                ..
            } => {
                mem::take(balance_root);
                mem::take(state_root);
            }

            Output::Message { recipient, amount } => {
                mem::take(recipient);
                mem::take(amount);
            }

            Output::Change { amount, .. } => {
                mem::take(amount);
            }

            Output::Variable {
                to,
                amount,
                asset_id,
                ..
            } => {
                mem::take(to);
                mem::take(amount);
                mem::take(asset_id);
            }

            _ => (),
        }
    }

    /// Prepare the output for VM initialization for script execution
    #[cfg(feature = "std")]
    pub fn prepare_init_script(&mut self) {
        match self {
            Output::Message { recipient, amount } => {
                mem::take(recipient);
                mem::take(amount);
            }

            Output::Change { amount, .. } => {
                mem::take(amount);
            }

            Output::Variable {
                to,
                amount,
                asset_id,
            } => {
                mem::take(to);
                mem::take(amount);
                mem::take(asset_id);
            }

            _ => (),
        }
    }

    /// Prepare the output for VM initialization for predicate verification
    pub fn prepare_init_predicate(&mut self) {
        self.prepare_sign()
    }
}

#[cfg(feature = "std")]
impl io::Read for Output {
    fn read(&mut self, mut buf: &mut [u8]) -> io::Result<usize> {
        let n = self.serialized_size();
        if buf.len() < n {
            return Err(bytes::eof());
        }

        let identifier: OutputRepr = self.into();
        buf = bytes::store_number_unchecked(buf, identifier as Word);

        match self {
            Self::Coin {
                to,
                amount,
                asset_id,
            }
            | Self::Change {
                to,
                amount,
                asset_id,
            }
            | Self::Variable {
                to,
                amount,
                asset_id,
            } => {
                buf = bytes::store_array_unchecked(buf, to);
                buf = bytes::store_number_unchecked(buf, *amount);

                bytes::store_array_unchecked(buf, asset_id);
            }

            Self::Message { recipient, amount } => {
                buf = bytes::store_array_unchecked(buf, recipient);

                bytes::store_number_unchecked(buf, *amount);
            }

            Self::Contract {
                input_index,
                balance_root,
                state_root,
            } => {
                buf = bytes::store_number_unchecked(buf, *input_index);
                buf = bytes::store_array_unchecked(buf, balance_root);

                bytes::store_array_unchecked(buf, state_root);
            }

            Self::ContractCreated {
                contract_id,
                state_root,
            } => {
                buf = bytes::store_array_unchecked(buf, contract_id);

                bytes::store_array_unchecked(buf, state_root);
            }
        }

        Ok(n)
    }
}

#[cfg(feature = "std")]
impl io::Write for Output {
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
        if buf.len() < WORD_SIZE {
            return Err(bytes::eof());
        }

        // Bounds safely checked
        let (identifier, buf): (Word, _) = unsafe { bytes::restore_number_unchecked(buf) };
        let identifier = OutputRepr::try_from(identifier)?;

        match identifier {
            OutputRepr::Coin | OutputRepr::Change | OutputRepr::Variable
                if buf.len() < OUTPUT_CCV_SIZE - WORD_SIZE =>
            {
                Err(bytes::eof())
            }

            OutputRepr::Message if buf.len() < OUTPUT_MESSAGE_SIZE - WORD_SIZE => Err(bytes::eof()),

            OutputRepr::Contract if buf.len() < OUTPUT_CONTRACT_SIZE - WORD_SIZE => {
                Err(bytes::eof())
            }

            OutputRepr::ContractCreated if buf.len() < OUTPUT_CONTRACT_CREATED_SIZE - WORD_SIZE => {
                Err(bytes::eof())
            }

            OutputRepr::Coin | OutputRepr::Change | OutputRepr::Variable => {
                // Safety: buf len is checked
                let (to, buf) = unsafe { bytes::restore_array_unchecked(buf) };
                let (amount, buf) = unsafe { bytes::restore_number_unchecked(buf) };
                let (asset_id, _) = unsafe { bytes::restore_array_unchecked(buf) };

                let to = to.into();
                let asset_id = asset_id.into();

                match identifier {
                    OutputRepr::Coin => {
                        *self = Self::Coin {
                            to,
                            amount,
                            asset_id,
                        }
                    }
                    OutputRepr::Change => {
                        *self = Self::Change {
                            to,
                            amount,
                            asset_id,
                        }
                    }
                    OutputRepr::Variable => {
                        *self = Self::Variable {
                            to,
                            amount,
                            asset_id,
                        }
                    }

                    _ => unreachable!(),
                }

                Ok(OUTPUT_CCV_SIZE)
            }

            OutputRepr::Message => {
                // Safety: buf len is checked
                let (recipient, buf) = unsafe { bytes::restore_array_unchecked(buf) };
                let (amount, _) = unsafe { bytes::restore_number_unchecked(buf) };

                let recipient = recipient.into();

                *self = Self::Message { recipient, amount };

                Ok(OUTPUT_MESSAGE_SIZE)
            }

            OutputRepr::Contract => {
                // Safety: buf len is checked
                let (input_index, buf) = unsafe { bytes::restore_u8_unchecked(buf) };
                let (balance_root, buf) = unsafe { bytes::restore_array_unchecked(buf) };
                let (state_root, _) = unsafe { bytes::restore_array_unchecked(buf) };

                let balance_root = balance_root.into();
                let state_root = state_root.into();

                *self = Self::Contract {
                    input_index,
                    balance_root,
                    state_root,
                };

                Ok(OUTPUT_CONTRACT_SIZE)
            }

            OutputRepr::ContractCreated => {
                // Safety: buf len is checked
                let (contract_id, buf) = unsafe { bytes::restore_array_unchecked(buf) };
                let (state_root, _) = unsafe { bytes::restore_array_unchecked(buf) };

                let contract_id = contract_id.into();
                let state_root = state_root.into();

                *self = Self::ContractCreated {
                    contract_id,
                    state_root,
                };

                Ok(OUTPUT_CONTRACT_CREATED_SIZE)
            }
        }
    }

    fn flush(&mut self) -> io::Result<()> {
        Ok(())
    }
}