-- |
-- This module contains all expressions for Relapse variables.

module Data.Katydid.Relapse.Exprs.Var (
    varBoolExpr
    , varIntExpr
    , varUintExpr
    , varDoubleExpr
    , varStringExpr
    , varBytesExpr
    , isVar
) where

import Data.Text (Text)
import Data.ByteString (ByteString)

import qualified Data.Katydid.Parser.Parser as Parser

import Data.Katydid.Relapse.Expr

-- |
-- isVar returns whether an expression is one of the six variable expressions.
isVar :: Desc -> Bool
isVar d = null (_params d) && case _name d of
    "$bool" -> True
    "$int" -> True
    "$uint" -> True
    "$double" -> True
    "$string" -> True
    "$[]byte" -> True
    _ -> False

-- |
-- varBoolExpr creates a bool variable expression.
varBoolExpr :: Expr Bool
varBoolExpr = Expr {
    desc = Desc {
        _name = "$bool"
        , _toStr = "$bool"
        , _hash = hashWithName "$bool" []
        , _params = []
        , _hasVar = True
    }
    , eval = \l -> case l of
        (Parser.Bool b) -> Right b
        _ -> Left "not a bool"
}

-- |
-- varIntExpr creates an int variable expression.
varIntExpr :: Expr Int
varIntExpr = Expr {
    desc = Desc {
        _name = "$int"
        , _toStr = "$int"
        , _hash = hashWithName "$int" []
        , _params = []
        , _hasVar = True
    }
    , eval = \l -> case l of
        (Parser.Int i) -> Right i
        _ -> Left "not an int"
}

-- |
-- varUintExpr creates a uint variable expression.
varUintExpr :: Expr Word
varUintExpr = Expr {
    desc = Desc {
        _name = "$uint"
        , _toStr = "$uint"
        , _hash = hashWithName "$uint" []
        , _params = []
        , _hasVar = True
    }
    , eval = \l -> case l of
        (Parser.Uint u) -> Right u
        _ -> Left "not a uint"
}

-- |
-- varDoubleExpr creates a double variable expression.
varDoubleExpr :: Expr Double
varDoubleExpr = Expr {
    desc = Desc {
        _name = "$double"
        , _toStr = "$double"
        , _hash = hashWithName "$double" []
        , _params = []
        , _hasVar = True
    }
    , eval = \l -> case l of
        (Parser.Double d) -> Right d
        _ -> Left "not a double"
}

-- |
-- varStringExpr creates a string variable expression.
varStringExpr :: Expr Text
varStringExpr = Expr {
    desc = Desc {
        _name = "$string"
        , _toStr = "$string"
        , _hash = hashWithName "$string" []
        , _params = []
        , _hasVar = True
    }
    , eval = \l -> case l of
        (Parser.String s) -> Right s
        _ -> Left "not a string"
}

-- |
-- varBytesExpr creates a bytes variable expression.
varBytesExpr :: Expr ByteString
varBytesExpr = Expr {
    desc = Desc {
        _name = "$[]byte"
        , _toStr = "$[]byte"
        , _hash = hashWithName "$[]byte" []
        , _params = []
        , _hasVar = True
    }
    , eval = \l -> case l of
        (Parser.Bytes b) -> Right b
        _ -> Left "not bytes"
}