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// 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::Opcode;
use console::{network::prelude::*, program::Identifier};

/// A position command, e.g. `position exit`.
/// Indicates a position to which the program can branch to.
#[derive(Clone, PartialEq, Eq, Hash)]
pub struct Position<N: Network> {
    /// The name to reference when branching to this position.
    name: Identifier<N>,
}

impl<N: Network> Position<N> {
    /// Returns the opcode.
    #[inline]
    pub const fn opcode() -> Opcode {
        Opcode::Command("position")
    }

    /// Returns the name.
    #[inline]
    pub fn name(&self) -> &Identifier<N> {
        &self.name
    }
}

impl<N: Network> Position<N> {
    /// Finalizes the command.
    /// Note that `Position` is a no-op.
    #[inline]
    pub fn finalize(&self) -> Result<()> {
        Ok(())
    }
}

impl<N: Network> Parser for Position<N> {
    /// Parses a string into a command.
    #[inline]
    fn parse(string: &str) -> ParserResult<Self> {
        // Parse the whitespace and comments from the string.
        let (string, _) = Sanitizer::parse(string)?;
        // 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 name from the string.
        let (string, name) = Identifier::parse(string)?;

        // Parse the whitespace from the string.
        let (string, _) = Sanitizer::parse_whitespaces(string)?;
        // Parse the ";" from the string.
        let (string, _) = tag(";")(string)?;

        Ok((string, Self { name }))
    }
}

impl<N: Network> FromStr for Position<N> {
    type Err = Error;

    /// Parses a string into the command.
    #[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> Debug for Position<N> {
    /// Prints the command as a string.
    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
        Display::fmt(self, f)
    }
}

impl<N: Network> Display for Position<N> {
    /// Prints the command to a string.
    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
        // Print the command.
        write!(f, "{} ", Self::opcode())?;
        // Print the name.
        write!(f, "{};", self.name)
    }
}

impl<N: Network> FromBytes for Position<N> {
    /// Reads the command from a buffer.
    fn read_le<R: Read>(mut reader: R) -> IoResult<Self> {
        // Read the name.
        let name = Identifier::read_le(&mut reader)?;
        // Return the command.
        Ok(Self { name })
    }
}

impl<N: Network> ToBytes for Position<N> {
    /// Writes the command to a buffer.
    fn write_le<W: Write>(&self, mut writer: W) -> IoResult<()> {
        // Write the name.
        self.name.write_le(&mut writer)
    }
}

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

    type CurrentNetwork = Testnet3;

    #[test]
    fn test_parse() {
        let (string, position) = Position::<CurrentNetwork>::parse("position exit;").unwrap();
        assert!(string.is_empty(), "Parser did not consume all of the string: '{string}'");
        assert_eq!(position.name, Identifier::from_str("exit").unwrap());
    }
}