From bee0febb5d98f0993a7a3bd175046f4fbf9c8eec Mon Sep 17 00:00:00 2001
From: Akshay Nair <phenax5@gmail.com>
Date: Sun, 15 Dec 2024 19:31:47 +0530
Subject: Generate random key sequences with lcg

---
 src/Chelleport.hs             |  6 ++++--
 src/Chelleport/KeySequence.hs | 38 +++++++++++++++++++++++---------------
 2 files changed, 27 insertions(+), 17 deletions(-)

(limited to 'src')

diff --git a/src/Chelleport.hs b/src/Chelleport.hs
index 82188b9..cb0ed84 100644
--- a/src/Chelleport.hs
+++ b/src/Chelleport.hs
@@ -7,6 +7,8 @@ import Chelleport.KeySequence (eventToKeycode, findMatchPosition, generateGrid,
 import Chelleport.Types
 import Chelleport.Utils (intToCInt)
 import qualified Chelleport.View
+import Data.List ((\\))
+import Data.Maybe (fromMaybe)
 import qualified SDL
 
 open :: IO ()
@@ -14,12 +16,12 @@ open = setupAppShell initialState update eventToAction Chelleport.View.render
 
 initialState :: DrawContext -> IO State
 initialState _ctx = do
-  let cells = generateGrid (rows, columns) hintKeys
+  let cells = fromMaybe (pure undefined) $ generateGrid 0 (rows, columns) hintKeys
   pure $ State {stateGrid = cells, stateKeySequence = []}
   where
     rows = 12
     columns = 12
-    hintKeys = "ABCDEFGHIJKLMNOPRSTUVWXYZ1234567890"
+    hintKeys = ['A' .. 'Z'] \\ "Q"
 
 update :: Update State AppAction
 update state _ctx (FilterSequence key) =
diff --git a/src/Chelleport/KeySequence.hs b/src/Chelleport/KeySequence.hs
index f112b57..9f7b5db 100644
--- a/src/Chelleport/KeySequence.hs
+++ b/src/Chelleport/KeySequence.hs
@@ -25,22 +25,30 @@ findMatchPosition keySequence = findWithIndex searchRows 0
 isValidKey :: SDL.Keycode -> Bool
 isValidKey = (`Map.member` keycodeMapping)
 
-generateKeyCells :: (Int, Int) -> KeySequence -> KeyGrid
-generateKeyCells (rows, columns) hintKeys =
-  (\row -> getCellSeq row <$> [1 .. columns]) <$> [1 .. rows]
+-- Linear Congruential Generator
+lcg :: Int -> Int
+lcg seed = (a * seed + c) `mod` fromIntegral m
   where
-    getCellSeq row col = [getPrefixHoriz row col, getPrefixVert row col, getKey row col]
-    getKey row col = hintKeys !! index
-      where
-        index = (secRow * (columns `div` 2) + secCol) `mod` length hintKeys
-        secCol = (col - 1) `mod` (columns `div` 2)
-        secRow = (row - 1) `mod` (rows `div` 2)
-    getPrefixHoriz _row col
-      | col <= (columns `div` 2) = 'H'
-      | otherwise = 'L'
-    getPrefixVert row _col
-      | row <= (rows `div` 2) = 'K'
-      | otherwise = 'J'
+    a = 1664525
+    c = 1013904223
+    m = (2 :: Integer) ^ (32 :: Integer)
+
+getIndexRounded :: Int -> [a] -> a
+getIndexRounded i ls = ls !! (i `mod` length ls)
+
+generateGrid :: Int -> (Int, Int) -> KeySequence -> Maybe KeyGrid
+generateGrid seed (rows, columns) hintKeys
+  | rows * columns > length hintKeys * length hintKeys = Nothing
+  | otherwise = Just $ (\row -> getKeySeq row <$> [0 .. columns - 1]) <$> [0 .. rows - 1]
+  where
+    allKeySeq = take numPairs . uniq $ generatePairs
+    numPairs = rows * columns
+    getKeySeq row col = allKeySeq !! (row * columns + col)
+    randomNumbers = iterate lcg seed
+    generatePairs =
+      [ [getIndexRounded i hintKeys, getIndexRounded j hintKeys]
+        | (i, j) <- zip randomNumbers (drop numPairs randomNumbers)
+      ]
 
 toKeyChar :: SDL.Keycode -> Maybe Char
 toKeyChar = (`Map.lookup` keycodeMapping)
-- 
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