{-# LANGUAGE DeriveAnyClass #-}
{-# LANGUAGE DeriveGeneric  #-}
{-# LANGUAGE ViewPatterns   #-}

-- |
-- Module    : Data.Kanji.Types
-- Copyright : (c) Colin Woodbury, 2015, 2016
-- License   : GPL3
-- Maintainer: Colin Woodbury <colin@fosskers.ca>
--
-- Types for this library. While a constructor for `Kanji` is made available
-- here, you should prefer the `kanji` "smart constructor" unless you know
-- for sure that the `Char` in question falls within the correct UTF8 range.

module Data.Kanji.Types where

import Control.DeepSeq (NFData)
import Data.Aeson
import Data.Bool (bool)
import Data.Char (isLetter, isNumber, isPunctuation, ord)
import Data.Hashable
import GHC.Generics

---

-- | A single symbol of Kanji. Japanese Kanji were borrowed from China
-- over several waves during the last 1,500 years. Japan names 2,136 of
-- these as their standard set, with rarer characters being the domain
-- of academia and esoteric writers.
--
-- Japanese has several Japan-only Kanji, including:
--
-- * 畑 (a type of rice field)
-- * 峠 (a narrow mountain pass)
-- * 働 (to do physical labour)
newtype Kanji = Kanji Char deriving (Eq, Ord, Show, Generic, ToJSON, FromJSON, Hashable, NFData)

-- | The original `Char` of a `Kanji`.
_kanji :: Kanji -> Char
_kanji (Kanji k) = k

-- | Construct a `Kanji` value from some `Char` if it falls in the correct UTF8 range.
kanji :: Char -> Maybe Kanji
kanji c = bool Nothing (Just $ Kanji c) $ isKanji c

-- | A Level or "Kyuu" (級) of Japanese Kanji ranking. There are 12 of these,
-- from 10 to 1, including intermediate levels between 3 and 2, and 2 and 1.
--
-- Japanese students will typically have Level-5 ability by the time they
-- finish elementary school. Level-5 accounts for 1,006 characters.
--
-- By the end of middle school, they would have covered up to Level-3
-- (1607 Kanji) in their Japanese class curriculum.
--
-- While Level-2 (2,136 Kanji) is considered "standard adult" ability,
-- many adults could not pass the Level-2, or even the Level-Pre2 (1940 Kanji)
-- exam without considerable study.
--
-- Level data for Kanji above Level-2 is currently not provided by
-- this library.
data Level = Ten | Nine | Eight | Seven | Six | Five | Four | Three | PreTwo
           | Two | PreOne | One | Unknown
           deriving (Eq, Ord, Enum, Show, Generic, Hashable, NFData, ToJSON, FromJSON, ToJSONKey)

-- | Legal Kanji appear between UTF-8 characters 19968 and 40959.
isKanji :: Char -> Bool
isKanji (ord -> c) = 19968 <= c && c <= 40959
{-# INLINE isKanji #-}

-- | あ to ん.
isHiragana :: Char -> Bool
isHiragana (ord -> c) = 0x3040 <= c && c <= 0x309f
{-# INLINE isHiragana #-}

-- | ア to ン.
isKatakana :: Char -> Bool
isKatakana (ord -> c) = 0x30a0 <= c && c <= 0x30ff
{-# INLINE isKatakana #-}

-- | General categories for characters, at least as is useful for thinking about
-- Japanese.
--
-- Japanese "full-width" numbers and letters will be counted as `Numeral`
-- and `RomanLetter` respectively, alongside their usual ASCII forms.
data CharCat = Hanzi | Hiragana | Katakana | Numeral | RomanLetter | Punctuation | Other
  deriving (Eq, Ord, Show, Generic, Hashable, NFData, ToJSON, FromJSON, ToJSONKey)

category :: Char -> CharCat
category c | isKanji c       = Hanzi
           | isHiragana c    = Hiragana
           | isKatakana c    = Katakana
           | isLetter c      = RomanLetter
           | isNumber c      = Numeral
           | isPunctuation c = Punctuation
           | otherwise       = Other