{-# LANGUAGE PatternGuards #-}

module Idris.Inliner where

import Idris.Core.TT
import Idris.AbsSyntax

inlineDef :: IState -> [([Name], Term, Term)] -> [([Name], Term, Term)]
inlineDef ist ds = map (\ (ns, lhs, rhs) -> (ns, lhs, inlineTerm ist rhs)) ds

-- Inlining is either top level (i.e. not in a function arg) or argument level

-- For each application in a term:
--    * Check if the function is inlinable
--        (Dictionaries are inlinable in an argument, not otherwise)
--      - If so, try inlining without reducing its arguments
--        + If successful, then continue on the result (top level)
--        + If not, reduce the arguments (argument level) and try again
--      - If not, inline all the arguments (top level)

inlineTerm :: IState -> Term -> Term
inlineTerm ist tm = inl tm where
  inl orig@(P _ n _) = inlApp n [] orig
  inl orig@(App _ f a)
      | (P _ fn _, args) <- unApply orig = inlApp fn args orig
  inl (Bind n (Let t v) sc) = Bind n (Let t (inl v)) (inl sc)
  inl (Bind n b sc) = Bind n b (inl sc)
  inl tm = tm

  inlApp fn args orig = orig