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//! An `Operation` captures the semantics of the IL.

use std::fmt;
use il::*;

/// An IL Operation updates some state.
#[derive(Clone, Debug, Deserialize, Eq, Hash, Ord, PartialEq, PartialOrd, Serialize)]
pub enum Operation {
    /// Assign the value given in expression to the variable indicated.
    Assign {
        dst: Scalar,
        src: Expression
    },
    /// Store the value in src at the address given in index.
    Store {
        index: Expression,
        src: Expression
    },
    /// Load the value in memory at index and place the result in the variable dst.
    Load {
        dst: Scalar,
        index: Expression,
    },
    /// Branch to the value given by target.
    Branch {
        target: Expression
    },
    /// Holds an Intrinsic for unmodellable instructions
    Intrinsic {
        intrinsic: Intrinsic
    },
    /// An operation that does nothing, and allows for a placeholder
    /// `Instuction`
    Nop
}


impl Operation {
    /// Create a new `Operation::Assign`.
    pub fn assign(dst: Scalar, src: Expression) -> Operation {
        Operation::Assign {
            dst: dst,
            src: src
        }
    }

    /// Create a new `Operation::Store`.
    pub fn store(index: Expression, src: Expression) -> Operation {
        Operation::Store { index: index, src: src }
    }

    /// Create a new `Operation::Load`.
    pub fn load(dst: Scalar, index: Expression) -> Operation {
        Operation::Load { dst: dst, index: index }
    }

    /// Create a new `Operation::Brc`.
    pub fn branch(target: Expression) -> Operation {
        Operation::Branch { target: target }
    }

    /// Create a new `Operation::Intrinsic`.
    pub fn intrinsic(intrinsic: Intrinsic) -> Operation {
        Operation::Intrinsic { intrinsic: intrinsic }
    }

    /// Create a new `Operation::Nop`
    pub fn nop() -> Operation {
        Operation::Nop
    }

    /// Get each `Scalar` read by this `Operation`.
    pub fn scalars_read(&self) -> Option<Vec<&Scalar>> {
        match *self {
            Operation::Assign { ref src, .. } => Some(src.scalars()),
            Operation::Store { ref index, ref src } =>
                Some(index.scalars()
                          .into_iter()
                          .chain(src.scalars().into_iter())
                          .collect()),
            Operation::Load { ref index, .. } => Some(index.scalars()),
            Operation::Branch { ref target } => Some(target.scalars()),
            Operation::Intrinsic { ref intrinsic } => intrinsic.scalars_read(),
            Operation::Nop => Some(Vec::new())
        }
    }

    /// Get a mutable reference to each `Scalar` read by this `Operation`.
    pub fn scalars_read_mut(&mut self) -> Option<Vec<&mut Scalar>> {
        match *self {
            Operation::Assign { ref mut src, .. } => Some(src.scalars_mut()),
            Operation::Store { ref mut index, ref mut src } => 
                Some(index.scalars_mut()
                          .into_iter()
                          .chain(src.scalars_mut().into_iter())
                          .collect()),
            Operation::Load { ref mut index, .. } => Some(index.scalars_mut()),
            Operation::Branch { ref mut target } => Some(target.scalars_mut()),
            Operation::Intrinsic { ref mut intrinsic } =>
                intrinsic.scalars_read_mut(),
            Operation::Nop => Some(Vec::new())
        }
    }

    /// Get a Vec of the `Scalar`s written by this `Operation`
    pub fn scalars_written(&self) -> Option<Vec<&Scalar>> {
        match *self {
            Operation::Assign { ref dst, .. } |
            Operation::Load   { ref dst, .. } => Some(vec![dst]),
            Operation::Store  { .. } |
            Operation::Branch { .. } => Some(Vec::new()),
            Operation::Intrinsic { ref intrinsic } =>
                intrinsic.scalars_written(),
            Operation::Nop => Some(Vec::new())
        }
    }

    /// Get a Vec of mutable referencer to the `Scalar`s written by this
    /// `Operation`
    pub fn scalars_written_mut(&mut self) -> Option<Vec<&mut Scalar>> {
        match *self {
            Operation::Assign { ref mut dst, .. } |
            Operation::Load   { ref mut dst, .. } => Some(vec![dst]),
            Operation::Store  { .. } |
            Operation::Branch { .. } => Some(Vec::new()),
            Operation::Intrinsic { ref mut intrinsic } =>
                intrinsic.scalars_written_mut(),
            Operation::Nop => Some(Vec::new())
        }
    }
}


impl fmt::Display for Operation {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match *self {
            Operation::Assign { ref dst, ref src } =>
                write!(f, "{} = {}", dst, src),
            Operation::Store { ref index, ref src } =>
                write!(f, "[{}] = {}", index, src),
            Operation::Load { ref dst, ref index } =>
                write!(f, "{} = [{}]", dst, index),
            Operation::Branch { ref target } =>
                write!(f, "branch {}", target),
            Operation::Intrinsic { ref intrinsic } =>
                write!(f, "intrinsic {}", intrinsic),
            Operation::Nop => write!(f, "nop")
        }
    }
}