{-# LANGUAGE UnicodeSyntax, NoMonomorphismRestriction, FlexibleInstances, TypeSynonymInstances #-}
module Todos.Tree 
  (delTag,
   pruneSelector,
   tagPred, statusPred, grepPred, descPred, datePred, idPred,
   forT, mapT)
  where

import Prelude hiding (putStrLn,readFile,getContents,print)
import Control.Monad
import Data.Generics
import Data.List
import Data.Tree
import Text.Regex.PCRE

import Todos.Types
import Todos.Unicode
import Todos.Config

mapTags ∷  (Data a) ⇒ ([String] → [String]) → [a] → [a]
mapTags f = map ⋄ everywhere ⋄ mkT changeTags
  where
    changeTags item@(Item {itemTags=ts}) = item {itemTags = f ts}
        
addTag ∷  (Data a) ⇒ String → [a] → [a]
addTag t = mapTags (t:)

delTag ∷  (Data a) ⇒ String → [a] → [a]
delTag t = mapTags (delete t)

pruneSelector ∷  BaseConfig → (TodoItem → 𝔹) → (Todo → [Todo])
pruneSelector bc pred =
  let Limit n = pruneL bc
      Limit m = minL   bc
  in  pruneSelector' n m pred
        
pruneSelector' ∷ ℤ → ℤ → (TodoItem → 𝔹) → (Todo → [Todo])
pruneSelector' n m pred = select n 0 False
    where
        select k t b (Node item trees) | t < m       = [Node item ⋄ concatMap (select (n-1) (t+1) True) trees]
                                       | pred item   = [Node item ⋄ concatMap (select (n-1) (t+1) True) trees]
                                       | (k > 0) ∧ b = [Node item ⋄ concatMap (select (k-1) (t+1) True) trees]
                                       | k > 0       = concatMap (select (k-1) (t+1) False) trees
                                       | otherwise   = []                                               

addS ∷  (Show a) ⇒ a → TodoItem → TodoItem
addS s item@(Item {itemName=name}) = item {itemName = name ⧺ " — " ⧺ show s}

-- | Check if item has given tag
tagPred ∷  String → TodoItem → 𝔹
tagPred tag = \item → tag ∈ itemTags item

-- | Check if item has given status
statusPred ∷  String → TodoItem → 𝔹
statusPred st = \item → st == itemStatus item
        
-- | Check if item's title matches to given regexp
grepPred ∷ String → TodoItem → 𝔹
grepPred pattern = \item → itemName item =~ pattern

-- | Check if item's description matches to given regexp
descPred ∷ String → TodoItem → 𝔹
descPred pattern = \item → itemDescr item =~ pattern

-- | Check if item has given ID
idPred :: String → TodoItem → 𝔹
idPred hash = \item → makeId item == hash

isLT ∷  (Ord t) ⇒ Maybe t → t → 𝔹
isLT Nothing _ = False
isLT (Just x) y = x <= y

isGT ∷  (Ord t) ⇒ Maybe t → t → 𝔹
isGT Nothing _ = False
isGT (Just x) y = x >= y

datePred ∷  (Ord a) ⇒ (t → Maybe a) → a → a → t → 𝔹
datePred selector curr dt | dt >= curr = \item → selector item `isLT` dt
                          | otherwise  = \item → selector item `isGT` dt

-- | Flattern the tree
flattern ∷ [Todo] → [Todo]
flattern = concatMap flat
    where
        flat ∷ Todo → [Todo]
        flat (Node item trees) = (Node item []):(concatMap flat trees)

-- | For each item in the tree, execute given monadic action (this is similar
-- to forM, but for trees instead of lists).
forT ∷ (Monad m, Eq t) ⇒ [Tree t] → (t → m a) → m [b]
forT todos f = forM (nub todos) forT'
  where
    forT' (Node item trees) =
      do f item
         res ← forM trees forT'
         return $ last res

-- | Similar to map, but for trees instead of lists.
mapT ∷ (t → t) → [Tree t] → [Tree t]
mapT f todos = map mapT' todos
  where
    mapT' (Node item trees) = Node (f item) (mapT f trees)