From d0a67b462b492f136c5d07f4a75819d3516652d5 Mon Sep 17 00:00:00 2001
From: eug-vs <eugene@eug-vs.xyz>
Date: Sat, 21 Jan 2023 19:52:56 +0300
Subject: feat: precompute ray attacks

---
 src/attacks.rs | 126 ++++++++++++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 115 insertions(+), 11 deletions(-)

diff --git a/src/attacks.rs b/src/attacks.rs
index a8daec9..97e4f37 100644
--- a/src/attacks.rs
+++ b/src/attacks.rs
@@ -4,7 +4,7 @@ static NOT_A_FILE: Bitboard = 0xFEFEFEFEFEFEFEFE;
 static NOT_B_FILE: Bitboard = 0xFDFDFDFDFDFDFDFD;
 static NOT_G_FILE: Bitboard = 0xBFBFBFBFBFBFBFBF;
 static NOT_H_FILE: Bitboard = 0x7F7F7F7F7F7F7F7F;
-static B_FILE: Bitboard =     0x0202020202020202;
+static B_FILE:     Bitboard = 0x0202020202020202;
 
 /// An array where N-th item is an attack bitboard
 /// of a piece on N-th square
@@ -21,21 +21,24 @@ pub type Byte = u8;
 /// ```
 type FirstRankAttacks = [[Byte; 8]; 256];
 
+enum Direction {
+    Nort,
+    NoEa,
+    East,
+    SoEa,
+    Sout,
+    SoWe,
+    West,
+    NoWe,
+}
 
 #[derive(Debug)]
 pub struct Attacks {
     pub knight: AttackTable,
     pub king: AttackTable,
     pub first_rank_attacks: FirstRankAttacks,
-
-    // pub nort_ray: AttackTable,
-    // pub noea_ray: AttackTable,
-    // pub east_ray: AttackTable,
-    // pub soea_ray: AttackTable,
-    // pub sout_ray: AttackTable,
-    // pub sowe_ray: AttackTable,
-    // pub west_ray: AttackTable,
-    // pub nowe_ray: AttackTable,
+    /// Should be indexed by Direction
+    pub ray_attacks: [AttackTable; 8],
 }
 
 #[allow(unused)]
@@ -44,11 +47,13 @@ impl Attacks {
         let knight = Self::precompute_knight_attacks();
         let king = Self::precompute_king_attacks();
         let first_rank_attacks = Self::precompute_first_rank_attacks();
+        let ray_attacks = Self::precompute_ray_attacks();
 
         Self {
             knight,
             king,
             first_rank_attacks,
+            ray_attacks,
         }
     }
 
@@ -121,11 +126,93 @@ impl Attacks {
         }
         attacks
     }
+
+    fn precompute_ray_attacks() -> [AttackTable; 8] {
+        let mut nort = [0; 64];
+        let mut noea = [0; 64];
+        let mut east = [0; 64];
+        let mut soea = [0; 64];
+        let mut sout = [0; 64];
+        let mut sowe = [0; 64];
+        let mut west = [0; 64];
+        let mut nowe = [0; 64];
+
+        for rank in 0..8 {
+            for file in 0..8 {
+                let index = rank * 8 + file;
+                {
+                    let mut rank = rank;
+                    while rank != 7 {
+                        rank += 1;
+                        nort[index] |= 1 << (rank * 8 + file);
+                    }
+                }
+                {
+                    let mut rank = rank;
+                    let mut file = file;
+                    while (rank < 7) && (file < 7) {
+                        rank += 1;
+                        file += 1;
+                        noea[index] |= 1 << (rank * 8 + file);
+                    }
+                }
+                {
+                    let mut file = file;
+                    while file < 7 {
+                        file += 1;
+                        east[index] |= 1 << (rank * 8 + file);
+                    }
+                }
+                {
+                    let mut rank = rank;
+                    let mut file = file;
+                    while (rank > 0) && (file < 7) {
+                        rank -= 1;
+                        file += 1;
+                        soea[index] |= 1 << (rank * 8 + file);
+                    }
+                }
+                {
+                    let mut rank = rank;
+                    while rank > 0 {
+                        rank -= 1;
+                        sout[index] |= 1 << (rank * 8 + file);
+                    }
+                }
+                {
+                    let mut rank = rank;
+                    let mut file = file;
+                    while (rank > 0) && (file > 0) {
+                        rank -= 1;
+                        file -= 1;
+                        sowe[index] |= 1 << (rank * 8 + file);
+                    }
+                }
+                {
+                    let mut file = file;
+                    while file > 0 {
+                        file -= 1;
+                        west[index] |= 1 << (rank * 8 + file);
+                    }
+                }
+                {
+                    let mut rank = rank;
+                    let mut file = file;
+                    while (file > 0) && (rank < 7) {
+                        file -= 1;
+                        rank += 1;
+                        nowe[index] |= 1 << (rank * 8 + file);
+                    }
+                }
+            }
+        }
+        [nort, noea, east, soea, sout, sowe, west, nowe]
+    }
 }
 
 #[cfg(test)]
 mod tests {
-    use crate::{bitboard::pop_count, board::Square};
+    use crate::{bitboard::{pop_count, print}, board::Square};
 
     use super::*;
 
@@ -180,4 +267,21 @@ mod tests {
         assert_eq!(attacks[0b01010010][4], 0b01101110);
 
     }
+
+    #[test]
+    fn test_ray_attacks() {
+        let attacks = Attacks::precompute_ray_attacks();
+        let square = Square::E4 as usize;
+
+        let bitboard =
+            attacks[0][square] |
+            attacks[1][square] |
+            attacks[2][square] |
+            attacks[3][square] |
+            attacks[4][square] |
+            attacks[5][square] |
+            attacks[6][square] |
+            attacks[7][square];
+        print(bitboard);
+    }
 }
-- 
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