-- |
-- Module      : Poker.Holdem.Evaluate
-- Description : Texas Hold'em poker hand evaluator.
-- Copyright   : (c) Ghais Issa, 2021
--
-- A Poker Hand Evaluator based on a perfect hash algorithm based
-- on the work of Henry Lee. The original CPP implementation can be
-- found here: [PokerHandEvaluator](https://github.com/HenryRLee/PokerHandEvaluator)
{-# LANGUAGE DerivingVia #-}
module Poker.Holdem.Evaluate
  (
    HandRank(..)
  , evaluate
  , evaluateHand
  )
where

import           Data.Array.Base (unsafeAccumArray, unsafeAt)
import qualified Data.Array.Unboxed as Array
import           Data.Bits (shift, (.&.), (.|.))
import           Data.Ord
import           Poker.Deck
import           Poker.Holdem
import qualified Poker.Holdem.Table.DP as Holdem
import qualified Poker.Holdem.Table.Flush as Holdem
import qualified Poker.Holdem.Table.NoFlush as Holdem
import qualified Poker.Holdem.Table.Suit as Holdem


-- | Rank of a hand.
--
-- if @(evaluate hand1) > (evaluate hand2)@ then hand1 is better than hand2
newtype HandRank = HandRank Int deriving newtype (Eq, Show, Read)
                                deriving newtype (Num)
                                deriving Ord via (Down Int)

-- | Evaluate a 7-card Texas Hold'em hand returning the rank of the hand.
evaluateHand :: Hand -> HandRank
evaluateHand (Hand (Hole c1 c2) (Community (Flop c3 c4 c5) (Turn c6) (Street c7))) =
  evaluate c1 c2 c3 c4 c5 c6 c7

-- | Evaluate a 7-card hand and return the rank of that hand.
evaluate ::
     Card  -- ^ c1
  -> Card  -- ^ c2
  -> Card  -- ^ c3
  -> Card  -- ^ c4
  -> Card  -- ^ c5
  -> Card  -- ^ c6
  -> Card  -- ^ c7
  -> HandRank -- ^ The rank of the hand.
evaluate (Card c1) (Card c2) (Card c3) (Card c4) (Card c5) (Card c6) (Card c7) =
  if Holdem.suitsLookup hash > 0 then
    HandRank $ handleFlush c1 c2 c3 c4 c5 c6 c7 hash
  else
    HandRank $ handleNonFlush c1 c2 c3 c4 c5 c6 c7
  where
    hash = suitHash c1 c2 c3 c4 c5 c6 c7

suitHash :: Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int
suitHash c1 c2 c3 c4 c5 c6 c7 =
  let b1 = suitBit `unsafeAt` c1
      b2 = suitBit `unsafeAt` c2
      b3 = suitBit `unsafeAt` c3
      b4 = suitBit `unsafeAt` c4
      b5 = suitBit `unsafeAt` c5
      b6 = suitBit `unsafeAt` c6
      b7 = suitBit `unsafeAt` c7
  in b1 + b2 + b3 + b4 + b5 + b6 + b7


hashQuinary :: Array.UArray Int Int -> Int
hashQuinary q = go 7 0 0
  where
    go k i s
      | i >= 13 = s
      | k <= 0 = s
      | otherwise =
        let sum' = s + Holdem.dpLookup q i k
            k' = k - (q `unsafeAt` i)
            i' = i + 1
         in go k' i' sum'

handleFlush :: Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int
handleFlush c1 c2 c3 c4 c5 c6 c7 hash =
  let
    suitBinary :: Array.UArray Int Int
    suitBinary = unsafeAccumArray (.|.) 0 (0, 3) [
        (c1 .&. 0x3, rankBit `unsafeAt` c1),
        (c2 .&. 0x3, rankBit `unsafeAt` c2),
        (c3 .&. 0x3, rankBit `unsafeAt` c3),
        (c4 .&. 0x3, rankBit `unsafeAt` c4),
        (c5 .&. 0x3, rankBit `unsafeAt` c5),
        (c6 .&. 0x3, rankBit `unsafeAt` c6),
        (c7 .&. 0x3, rankBit `unsafeAt` c7)]
    idx = suitBinary `unsafeAt` (Holdem.suitsLookup hash - 1)
  in Holdem.flushLookup idx



handleNonFlush :: Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int
handleNonFlush c1 c2 c3 c4 c5 c6 c7 =
  let
    idxs :: [(Int, Int)]
    idxs = [ (c1 `shift` (-2), 1),
             (c2 `shift` (-2), 1),
             (c3 `shift` (-2), 1),
             (c4 `shift` (-2), 1),
             (c5 `shift` (-2), 1),
             (c6 `shift` (-2), 1),
             (c7 `shift` (-2), 1)
           ]
    quinary :: Array.UArray Int Int
    quinary = unsafeAccumArray (+) 0 (0, 12) idxs
    hash =  hashQuinary quinary
  in Holdem.noFlushLookup hash

rankBit :: Array.UArray Int Int
rankBit = Array.listArray (0, 51)
    [ 0x1,      0x1,      0x1,      0x1,
      0x2,      0x2,      0x2,      0x2,
      0x4,      0x4,      0x4,      0x4,
      0x8,      0x8,      0x8,      0x8,
      0x10,     0x10,     0x10,     0x10,
      0x20,     0x20,     0x20,     0x20,
      0x40,     0x40,     0x40,     0x40,
      0x80,     0x80,     0x80,     0x80,
      0x100,    0x100,    0x100,    0x100,
      0x200,    0x200,    0x200,    0x200,
      0x400,    0x400,    0x400,    0x400,
      0x800,    0x800,    0x800,    0x800,
      0x1000,   0x1000,   0x1000,    0x1000
    ]

suitBit :: Array.UArray Int Int
suitBit =
  Array.listArray (0,51)
    [ 0x1,      0x8,      0x40,      0x200,
      0x1,      0x8,      0x40,      0x200,
      0x1,      0x8,      0x40,      0x200,
      0x1,      0x8,      0x40,      0x200,
      0x1,      0x8,      0x40,      0x200,
      0x1,      0x8,      0x40,      0x200,
      0x1,      0x8,      0x40,      0x200,
      0x1,      0x8,      0x40,      0x200,
      0x1,      0x8,      0x40,      0x200,
      0x1,      0x8,      0x40,      0x200,
      0x1,      0x8,      0x40,      0x200,
      0x1,      0x8,      0x40,      0x200,
      0x1,      0x8,      0x40,      0x200
    ]