{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE MultiParamTypeClasses #-}

module Zenith.Tree where

import Data.HexString

class Monoid v =>
      Measured a v
  where
  measure :: a -> v

data Tree v a
  = Leaf !v !a
  | Branch !v !(Tree v a) !(Tree v a)

value :: Tree v a -> v
value (Leaf v _) = v
value (Branch v _ _) = v

branch :: Monoid v => Tree v a -> Tree v a -> Tree v a
branch x y = Branch (value x <> value y) x y

leaf :: Measured a v => a -> Tree v a
leaf a = Leaf (measure a) a

data OrchardNode = OrchardNode
  { on_position :: !Integer
  , on_value :: !String
  , on_level :: !Int
  } deriving (Show, Eq)

instance Semigroup OrchardNode where
  (<>) x y =
    if on_level x == on_level y
      then OrchardNode
             (max (on_position x) (on_position y))
             (on_value x <> on_value y)
             (on_level x)
      else x

instance Monoid OrchardNode where
  mempty = OrchardNode 0 "" (-1)
  mappend = (<>)