{-|
Module      : Language.JVM.Method
Copyright   : (c) Christian Gram Kalhauge, 2017
License     : MIT
Maintainer  : kalhuage@cs.ucla.edu
-}

{-# LANGUAGE DeriveGeneric   #-}
module Language.JVM.Method
  ( Method (..)

  , mAccessFlags
  , mAttributes

  , mName
  , mDescriptor

  -- * Attributes
  , mCode
  , mExceptions

  ) where

import           Data.Binary
import           Data.Set (Set)
import qualified Data.Text as Text
import           GHC.Generics            (Generic)

import           Data.Monoid

import           Language.JVM.AccessFlag
import           Language.JVM.Attribute  (Attribute, fromAttribute', Code, Exceptions)
import           Language.JVM.Constant   (ConstantRef, ConstantPool, lookupText)
import           Language.JVM.Utils

-- | A Method in the class-file, as described
-- [here](http://docs.oracle.com/javase/specs/jvms/se7/html/jvms-4.html#jvms-4.6).
data Method = Method
  { mAccessFlags'    :: BitSet16 MAccessFlag
  , mNameIndex       :: ! ConstantRef
  , mDescriptorIndex :: ! ConstantRef
  , mAttributes'     :: SizedList16 Attribute
  } deriving (Show, Eq, Generic)

instance Binary Method where

-- | Unpack the BitSet and get the AccessFlags as a Set.
mAccessFlags :: Method -> Set MAccessFlag
mAccessFlags = toSet . mAccessFlags'

-- | Unpack the SizedList and get the attributes as a List.
mAttributes :: Method -> [Attribute]
mAttributes = unSizedList . mAttributes'

-- | Lookup the name of the method in the 'ConstantPool'.
mName :: ConstantPool -> Method -> Maybe Text.Text
mName cp = flip lookupText cp . mNameIndex

-- | Lookup the descriptor of the method in the 'ConstantPool'.
mDescriptor :: ConstantPool -> Method -> Maybe Text.Text
mDescriptor cp = flip lookupText cp . mDescriptorIndex

-- | Fetch the 'Code' attribute, if any.
-- There can only one be one code attribute on a method.
mCode :: ConstantPool -> Method -> Maybe (Either String Code)
mCode cp =
  getFirst . foldMap (First . fromAttribute' cp) . mAttributes

-- | Fetch the 'Exceptions' attribute.
-- There can only one be one exceptions attribute on a method.
mExceptions :: ConstantPool -> Method -> Maybe (Either String Exceptions)
mExceptions cp =
  getFirst . foldMap (First . fromAttribute' cp) . mAttributes