// Copyright (C) 2019-2023 Aleo Systems Inc.
// This file is part of the snarkVM library.

// 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.

use crate::{
    traits::{RegistersLoad, RegistersLoadCircuit, RegistersStore, RegistersStoreCircuit, StackMatches, StackProgram},
    Opcode,
    Operand,
};
use console::{
    network::prelude::*,
    program::{Literal, LiteralType, Plaintext, PlaintextType, Register, RegisterType, Value},
};

/// BHP256 is a collision-resistant hash function that processes inputs in 256-bit chunks.
pub type HashBHP256<N> = HashInstruction<N, { Hasher::HashBHP256 as u8 }>;
/// BHP512 is a collision-resistant hash function that processes inputs in 512-bit chunks.
pub type HashBHP512<N> = HashInstruction<N, { Hasher::HashBHP512 as u8 }>;
/// BHP768 is a collision-resistant hash function that processes inputs in 768-bit chunks.
pub type HashBHP768<N> = HashInstruction<N, { Hasher::HashBHP768 as u8 }>;
/// BHP1024 is a collision-resistant hash function that processes inputs in 1024-bit chunks.
pub type HashBHP1024<N> = HashInstruction<N, { Hasher::HashBHP1024 as u8 }>;

/// Pedersen64 is a collision-resistant hash function that processes inputs in 64-bit chunks.
pub type HashPED64<N> = HashInstruction<N, { Hasher::HashPED64 as u8 }>;
/// Pedersen128 is a collision-resistant hash function that processes inputs in 128-bit chunks.
pub type HashPED128<N> = HashInstruction<N, { Hasher::HashPED128 as u8 }>;

/// Poseidon2 is a cryptographic hash function that processes inputs in 2-field chunks.
pub type HashPSD2<N> = HashInstruction<N, { Hasher::HashPSD2 as u8 }>;
/// Poseidon4 is a cryptographic hash function that processes inputs in 4-field chunks.
pub type HashPSD4<N> = HashInstruction<N, { Hasher::HashPSD4 as u8 }>;
/// Poseidon8 is a cryptographic hash function that processes inputs in 8-field chunks.
pub type HashPSD8<N> = HashInstruction<N, { Hasher::HashPSD8 as u8 }>;

/// Poseidon2 is a cryptographic hash function that processes inputs in 2-field chunks.
pub type HashManyPSD2<N> = HashInstruction<N, { Hasher::HashManyPSD2 as u8 }>;
/// Poseidon4 is a cryptographic hash function that processes inputs in 4-field chunks.
pub type HashManyPSD4<N> = HashInstruction<N, { Hasher::HashManyPSD4 as u8 }>;
/// Poseidon8 is a cryptographic hash function that processes inputs in 8-field chunks.
pub type HashManyPSD8<N> = HashInstruction<N, { Hasher::HashManyPSD8 as u8 }>;

enum Hasher {
    HashBHP256,
    HashBHP512,
    HashBHP768,
    HashBHP1024,
    HashPED64,
    HashPED128,
    HashPSD2,
    HashPSD4,
    HashPSD8,
    HashManyPSD2,
    HashManyPSD4,
    HashManyPSD8,
}

/// Returns the expected number of operands given the variant.
const fn expected_num_operands(variant: u8) -> usize {
    match variant {
        9..=11 => 2,
        _ => 1,
    }
}

/// Returns 'Ok(())' if the number of operands is correct.
/// Otherwise, returns an error.
fn check_number_of_operands(variant: u8, opcode: Opcode, num_operands: usize) -> Result<()> {
    let expected = expected_num_operands(variant);
    if expected != num_operands {
        bail!("Instruction '{opcode}' expects {expected} operands, found {num_operands} operands")
    }
    Ok(())
}

/// Returns 'true' if the destination type is valid.
fn is_valid_destination_type(destination_type: LiteralType) -> bool {
    !matches!(destination_type, LiteralType::Boolean | LiteralType::String)
}

/// Hashes the operand into the declared type.
#[derive(Clone, PartialEq, Eq, Hash)]
pub struct HashInstruction<N: Network, const VARIANT: u8> {
    /// The operand as `input`.
    operands: Vec<Operand<N>>,
    /// The destination register.
    destination: Register<N>,
    /// The destination register type.
    destination_type: LiteralType,
}

impl<N: Network, const VARIANT: u8> HashInstruction<N, VARIANT> {
    /// Initializes a new `hash` instruction.
    #[inline]
    pub fn new(operands: Vec<Operand<N>>, destination: Register<N>, destination_type: LiteralType) -> Result<Self> {
        // Sanity check the number of operands.
        check_number_of_operands(VARIANT, Self::opcode(), operands.len())?;
        // Sanity check the destination type.
        if !is_valid_destination_type(destination_type) {
            bail!("Invalid destination type for 'hash' instruction")
        }
        // Return the instruction.
        Ok(Self { operands, destination, destination_type })
    }

    /// Returns the opcode.
    #[inline]
    pub const fn opcode() -> Opcode {
        match VARIANT {
            0 => Opcode::Hash("hash.bhp256"),
            1 => Opcode::Hash("hash.bhp512"),
            2 => Opcode::Hash("hash.bhp768"),
            3 => Opcode::Hash("hash.bhp1024"),
            4 => Opcode::Hash("hash.ped64"),
            5 => Opcode::Hash("hash.ped128"),
            6 => Opcode::Hash("hash.psd2"),
            7 => Opcode::Hash("hash.psd4"),
            8 => Opcode::Hash("hash.psd8"),
            9 => Opcode::Hash("hash_many.psd2"),
            10 => Opcode::Hash("hash_many.psd4"),
            11 => Opcode::Hash("hash_many.psd8"),
            12.. => panic!("Invalid 'hash' instruction opcode"),
        }
    }

    /// Returns the operands in the operation.
    #[inline]
    pub fn operands(&self) -> &[Operand<N>] {
        // Sanity check that the operands is the correct length.
        debug_assert!(
            check_number_of_operands(VARIANT, Self::opcode(), self.operands.len()).is_ok(),
            "Invalid number of operands for '{}'",
            Self::opcode()
        );
        // Return the operand.
        &self.operands
    }

    /// Returns the destination register.
    #[inline]
    pub fn destinations(&self) -> Vec<Register<N>> {
        vec![self.destination.clone()]
    }

    /// Returns the destination register type.
    #[inline]
    pub const fn destination_type(&self) -> LiteralType {
        self.destination_type
    }
}

impl<N: Network, const VARIANT: u8> HashInstruction<N, VARIANT> {
    /// Evaluates the instruction.
    #[inline]
    pub fn evaluate(
        &self,
        stack: &(impl StackMatches<N> + StackProgram<N>),
        registers: &mut (impl RegistersLoad<N> + RegistersStore<N>),
    ) -> Result<()> {
        // Ensure the number of operands is correct.
        check_number_of_operands(VARIANT, Self::opcode(), self.operands.len())?;
        // Ensure the destination type is valid.
        ensure!(is_valid_destination_type(self.destination_type), "Invalid destination type in 'hash' instruction");

        // Load the operand.
        let input = registers.load(stack, &self.operands[0])?;
        // Hash the input.
        let output = match (VARIANT, self.destination_type) {
            (0, _) => Literal::Group(N::hash_to_group_bhp256(&input.to_bits_le())?),
            (1, _) => Literal::Group(N::hash_to_group_bhp512(&input.to_bits_le())?),
            (2, _) => Literal::Group(N::hash_to_group_bhp768(&input.to_bits_le())?),
            (3, _) => Literal::Group(N::hash_to_group_bhp1024(&input.to_bits_le())?),
            (4, _) => Literal::Group(N::hash_to_group_ped64(&input.to_bits_le())?),
            (5, _) => Literal::Group(N::hash_to_group_ped128(&input.to_bits_le())?),
            (6, LiteralType::Address) | (6, LiteralType::Group) => {
                Literal::Group(N::hash_to_group_psd2(&input.to_fields()?)?)
            }
            (6, _) => Literal::Field(N::hash_psd2(&input.to_fields()?)?),
            (7, LiteralType::Address) | (7, LiteralType::Group) => {
                Literal::Group(N::hash_to_group_psd4(&input.to_fields()?)?)
            }
            (7, _) => Literal::Field(N::hash_psd4(&input.to_fields()?)?),
            (8, LiteralType::Address) | (8, LiteralType::Group) => {
                Literal::Group(N::hash_to_group_psd8(&input.to_fields()?)?)
            }
            (8, _) => Literal::Field(N::hash_psd8(&input.to_fields()?)?),
            (9, _) => bail!("'hash_many' is not yet implemented"),
            (10, _) => bail!("'hash_many' is not yet implemented"),
            (11, _) => bail!("'hash_many' is not yet implemented"),
            (12.., _) => bail!("Invalid 'hash' variant: {VARIANT}"),
        };
        // Cast the output to the destination type.
        let output = output.downcast_lossy(self.destination_type)?;
        // Store the output.
        registers.store(stack, &self.destination, Value::Plaintext(Plaintext::from(output)))
    }

    /// Executes the instruction.
    #[inline]
    pub fn execute<A: circuit::Aleo<Network = N>>(
        &self,
        stack: &(impl StackMatches<N> + StackProgram<N>),
        registers: &mut (impl RegistersLoadCircuit<N, A> + RegistersStoreCircuit<N, A>),
    ) -> Result<()> {
        use circuit::{ToBits, ToFields};

        // Ensure the number of operands is correct.
        check_number_of_operands(VARIANT, Self::opcode(), self.operands.len())?;
        // Ensure the destination type is valid.
        ensure!(is_valid_destination_type(self.destination_type), "Invalid destination type in 'hash' instruction");

        // Load the operand.
        let input = registers.load_circuit(stack, &self.operands[0])?;
        // Hash the input.
        let output = match (VARIANT, self.destination_type) {
            (0, _) => circuit::Literal::Group(A::hash_to_group_bhp256(&input.to_bits_le())),
            (1, _) => circuit::Literal::Group(A::hash_to_group_bhp512(&input.to_bits_le())),
            (2, _) => circuit::Literal::Group(A::hash_to_group_bhp768(&input.to_bits_le())),
            (3, _) => circuit::Literal::Group(A::hash_to_group_bhp1024(&input.to_bits_le())),
            (4, _) => circuit::Literal::Group(A::hash_to_group_ped64(&input.to_bits_le())),
            (5, _) => circuit::Literal::Group(A::hash_to_group_ped128(&input.to_bits_le())),
            (6, LiteralType::Address) | (6, LiteralType::Group) => {
                circuit::Literal::Group(A::hash_to_group_psd2(&input.to_fields()))
            }
            (6, _) => circuit::Literal::Field(A::hash_psd2(&input.to_fields())),
            (7, LiteralType::Address) | (7, LiteralType::Group) => {
                circuit::Literal::Group(A::hash_to_group_psd4(&input.to_fields()))
            }
            (7, _) => circuit::Literal::Field(A::hash_psd4(&input.to_fields())),
            (8, LiteralType::Address) | (8, LiteralType::Group) => {
                circuit::Literal::Group(A::hash_to_group_psd8(&input.to_fields()))
            }
            (8, _) => circuit::Literal::Field(A::hash_psd8(&input.to_fields())),
            (9, _) => bail!("'hash_many' is not yet implemented"),
            (10, _) => bail!("'hash_many' is not yet implemented"),
            (11, _) => bail!("'hash_many' is not yet implemented"),
            (12.., _) => bail!("Invalid 'hash' variant: {VARIANT}"),
        };
        let output = output.downcast_lossy(self.destination_type)?;
        // Convert the output to a stack value.
        let output = circuit::Value::Plaintext(circuit::Plaintext::Literal(output, Default::default()));
        // Store the output.
        registers.store_circuit(stack, &self.destination, output)
    }

    /// Finalizes the instruction.
    #[inline]
    pub fn finalize(
        &self,
        stack: &(impl StackMatches<N> + StackProgram<N>),
        registers: &mut (impl RegistersLoad<N> + RegistersStore<N>),
    ) -> Result<()> {
        self.evaluate(stack, registers)
    }

    /// Returns the output type from the given program and input types.
    #[inline]
    pub fn output_types(
        &self,
        _stack: &impl StackProgram<N>,
        input_types: &[RegisterType<N>],
    ) -> Result<Vec<RegisterType<N>>> {
        // Ensure the number of input types is correct.
        check_number_of_operands(VARIANT, Self::opcode(), input_types.len())?;
        // Ensure the number of operands is correct.
        check_number_of_operands(VARIANT, Self::opcode(), self.operands.len())?;
        // Ensure the destination type is valid.
        ensure!(is_valid_destination_type(self.destination_type), "Invalid destination type in 'hash' instruction");

        // TODO (howardwu): If the operation is Pedersen, check that it is within the number of bits.

        match VARIANT {
            0..=8 => Ok(vec![RegisterType::Plaintext(PlaintextType::Literal(self.destination_type))]),
            9..=11 => bail!("'hash_many' is not yet implemented"),
            12.. => bail!("Invalid 'hash' variant: {VARIANT}"),
        }
    }
}

impl<N: Network, const VARIANT: u8> Parser for HashInstruction<N, VARIANT> {
    /// Parses a string into an operation.
    #[inline]
    fn parse(string: &str) -> ParserResult<Self> {
        /// Parse the operands from the string.
        fn parse_operands<N: Network>(string: &str, num_operands: usize) -> ParserResult<Vec<Operand<N>>> {
            let mut operands = Vec::with_capacity(num_operands);
            let mut string = string;

            for _ in 0..num_operands {
                // Parse the operand from the string.
                let (next_string, operand) = Operand::parse(string)?;
                // Update the string.
                string = next_string;
                // Push the operand.
                operands.push(operand);
            }

            Ok((string, operands))
        }

        // Parse the opcode from the string.
        let (string, _) = tag(*Self::opcode())(string)?;
        // Parse the whitespace from the string.
        let (string, _) = Sanitizer::parse_whitespaces(string)?;
        // Parse the operands from the string.
        let (string, operands) = parse_operands(string, expected_num_operands(VARIANT))?;
        // Parse the whitespace from the string.
        let (string, _) = Sanitizer::parse_whitespaces(string)?;
        // Parse the "into" from the string.
        let (string, _) = tag("into")(string)?;
        // Parse the whitespace from the string.
        let (string, _) = Sanitizer::parse_whitespaces(string)?;
        // Parse the destination register from the string.
        let (string, destination) = Register::parse(string)?;
        // Parse the whitespace from the string.
        let (string, _) = Sanitizer::parse_whitespaces(string)?;
        // Parse the "as" from the string.
        let (string, _) = tag("as")(string)?;
        // Parse the whitespace from the string.
        let (string, _) = Sanitizer::parse_whitespaces(string)?;
        // Parse the destination register type from the string.
        let (string, destination_type) = LiteralType::parse(string)?;
        // Ensure the destination type is allowed.
        match destination_type {
            LiteralType::Boolean | LiteralType::String => map_res(fail, |_: ParserResult<Self>| {
                Err(error(format!("Failed to parse 'hash': '{destination_type}' is invalid")))
            })(string),
            _ => Ok((string, Self { operands, destination, destination_type })),
        }
    }
}

impl<N: Network, const VARIANT: u8> FromStr for HashInstruction<N, VARIANT> {
    type Err = Error;

    /// Parses a string into an operation.
    #[inline]
    fn from_str(string: &str) -> Result<Self> {
        match Self::parse(string) {
            Ok((remainder, object)) => {
                // Ensure the remainder is empty.
                ensure!(remainder.is_empty(), "Failed to parse string. Found invalid character in: \"{remainder}\"");
                // Return the object.
                Ok(object)
            }
            Err(error) => bail!("Failed to parse string. {error}"),
        }
    }
}

impl<N: Network, const VARIANT: u8> Debug for HashInstruction<N, VARIANT> {
    /// Prints the operation as a string.
    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
        Display::fmt(self, f)
    }
}

impl<N: Network, const VARIANT: u8> Display for HashInstruction<N, VARIANT> {
    /// Prints the operation to a string.
    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
        // Ensure the number of operands is correct.
        check_number_of_operands(VARIANT, Self::opcode(), self.operands.len()).map_err(|_| fmt::Error)?;
        // Print the operation.
        write!(f, "{} ", Self::opcode())?;
        self.operands.iter().try_for_each(|operand| write!(f, "{operand} "))?;
        write!(f, "into {} as {}", self.destination, self.destination_type)
    }
}

impl<N: Network, const VARIANT: u8> FromBytes for HashInstruction<N, VARIANT> {
    /// Reads the operation from a buffer.
    fn read_le<R: Read>(mut reader: R) -> IoResult<Self> {
        // Prepare the number of operands.
        let num_operands = expected_num_operands(VARIANT);
        // Read the operands.
        let operands = (0..num_operands).map(|_| Operand::read_le(&mut reader)).collect::<Result<_, _>>()?;
        // Read the destination register.
        let destination = Register::read_le(&mut reader)?;
        // Read the destination register type.
        let destination_type = LiteralType::read_le(&mut reader)?;
        // Return the operation.
        Ok(Self { operands, destination, destination_type })
    }
}

impl<N: Network, const VARIANT: u8> ToBytes for HashInstruction<N, VARIANT> {
    /// Writes the operation to a buffer.
    fn write_le<W: Write>(&self, mut writer: W) -> IoResult<()> {
        // Ensure the number of operands is correct.
        check_number_of_operands(VARIANT, Self::opcode(), self.operands.len()).map_err(|e| error(format!("{e}")))?;
        // Write the operands.
        self.operands.iter().try_for_each(|operand| operand.write_le(&mut writer))?;
        // Write the destination register.
        self.destination.write_le(&mut writer)?;
        // Write the destination register type.
        self.destination_type.write_le(&mut writer)
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use console::network::Testnet3;

    type CurrentNetwork = Testnet3;

    /// **Attention**: When changing this, also update in `tests/instruction/hash.rs`.
    fn valid_destination_types() -> &'static [LiteralType] {
        &[
            LiteralType::Address,
            LiteralType::Field,
            LiteralType::Group,
            LiteralType::I8,
            LiteralType::I16,
            LiteralType::I32,
            LiteralType::I64,
            LiteralType::I128,
            LiteralType::U8,
            LiteralType::U16,
            LiteralType::U32,
            LiteralType::U64,
            LiteralType::U128,
            LiteralType::Scalar,
        ]
    }

    #[test]
    fn test_parse() {
        for destination_type in valid_destination_types() {
            let instruction = format!("hash.bhp512 r0 into r1 as {destination_type}");
            let (string, hash) = HashBHP512::<CurrentNetwork>::parse(&instruction).unwrap();
            assert!(string.is_empty(), "Parser did not consume all of the string: '{string}'");
            assert_eq!(hash.operands.len(), 1, "The number of operands is incorrect");
            assert_eq!(hash.operands[0], Operand::Register(Register::Locator(0)), "The first operand is incorrect");
            assert_eq!(hash.destination, Register::Locator(1), "The destination register is incorrect");
            assert_eq!(hash.destination_type, *destination_type, "The destination type is incorrect");
        }
    }
}