From 8289204e4ba6052c36e4a3119e3d8138c0b02974 Mon Sep 17 00:00:00 2001
From: Bruno BELANYI <bruno@belanyi.fr>
Date: Sun, 24 Jul 2022 13:40:01 +0200
Subject: [PATCH] Generate magic tables with build script

---
 Cargo.toml   |  11 +++++
 src/build.rs | 133 +++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 144 insertions(+)
 create mode 100644 src/build.rs

diff --git a/Cargo.toml b/Cargo.toml
index 52a2217..756e025 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -2,8 +2,19 @@
 name = "seer"
 version = "0.1.0"
 edition = "2021"
+build = "src/build.rs"
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
 random = "0.12.2"
+
+[build-dependencies]
+random = "0.12.2"
+
+# Optimize build scripts to shorten compile times.
+[profile.dev.build-override]
+opt-level = 3
+
+[profile.release.build-override]
+opt-level = 3
diff --git a/src/build.rs b/src/build.rs
new file mode 100644
index 0000000..29721d1
--- /dev/null
+++ b/src/build.rs
@@ -0,0 +1,133 @@
+use std::io::{Result, Write};
+
+pub mod board;
+pub mod movegen;
+pub mod utils;
+
+use crate::{
+    board::{Bitboard, Color, File, Square},
+    movegen::{
+        king::king_moves,
+        knight::knight_moves,
+        pawn::{pawn_captures, pawn_moves},
+        wizardry::generation::{generate_bishop_magics, generate_rook_magics},
+        Magic,
+    },
+};
+
+fn print_magics(out: &mut dyn Write, var_name: &str, magics: &[Magic]) -> Result<()> {
+    writeln!(out, "static {}: [Magic; {}] = [", var_name, magics.len())?;
+    for magic in magics.iter() {
+        writeln!(
+            out,
+            "    Magic{{magic: {}, offset: {}, mask: Bitboard({}), shift: {},}},",
+            magic.magic, magic.offset, magic.mask.0, magic.shift
+        )?;
+    }
+    writeln!(out, "];")?;
+    Ok(())
+}
+
+fn print_boards(out: &mut dyn Write, var_name: &str, boards: &[Bitboard]) -> Result<()> {
+    writeln!(out, "static {}: [Bitboard; {}] = [", var_name, boards.len())?;
+    for board in boards.iter().cloned() {
+        writeln!(out, "    Bitboard({}),", board.0)?;
+    }
+    writeln!(out, "];")?;
+    Ok(())
+}
+
+fn print_double_sided_boards(
+    out: &mut dyn Write,
+    var_name: &str,
+    white_boards: &[Bitboard],
+    black_boards: &[Bitboard],
+) -> Result<()> {
+    assert_eq!(white_boards.len(), black_boards.len());
+    writeln!(
+        out,
+        "static {}: [[Bitboard; {}]; 2] = [",
+        var_name,
+        white_boards.len()
+    )?;
+    for color in Color::iter() {
+        let boards = if color == Color::White {
+            white_boards
+        } else {
+            black_boards
+        };
+        writeln!(out, "    [")?;
+        for square in Square::iter() {
+            writeln!(out, "        Bitboard({}),", boards[square.index()].0)?;
+        }
+        writeln!(out, "    ],")?;
+    }
+    writeln!(out, "];")?;
+    Ok(())
+}
+
+#[allow(clippy::redundant_clone)]
+fn main() -> Result<()> {
+    // FIXME: rerun-if-changed directives
+
+    let out_dir = std::env::var_os("OUT_DIR").unwrap();
+    let magic_path = std::path::Path::new(&out_dir).join("magic_tables.rs");
+    let mut out = std::fs::File::create(&magic_path).unwrap();
+
+    let rng = random::default().seed([12, 27]);
+
+    {
+        let (magics, moves) = generate_bishop_magics(&mut rng.clone());
+        print_magics(&mut out, "BISHOP_MAGICS", &magics)?;
+        print_boards(&mut out, "BISHOP_MOVES", &moves)?;
+    }
+
+    {
+        let (magics, moves) = generate_rook_magics(&mut rng.clone());
+        print_magics(&mut out, "ROOK_MAGICS", &magics)?;
+        print_boards(&mut out, "ROOK_MOVES", &moves)?;
+    }
+
+    {
+        let moves: Vec<_> = Square::iter().map(knight_moves).collect();
+        print_boards(&mut out, "KNIGHT_MOVES", &moves)?;
+    }
+
+    {
+        let white_moves: Vec<_> = Square::iter()
+            .map(|square| pawn_moves(Color::White, square, Bitboard::EMPTY))
+            .collect();
+        let black_moves: Vec<_> = Square::iter()
+            .map(|square| pawn_moves(Color::Black, square, Bitboard::EMPTY))
+            .collect();
+        print_double_sided_boards(&mut out, "PAWN_MOVES", &white_moves, &black_moves)?;
+        let white_attacks: Vec<_> = Square::iter()
+            .map(|square| pawn_captures(Color::White, square))
+            .collect();
+        let black_attacks: Vec<_> = Square::iter()
+            .map(|square| pawn_captures(Color::Black, square))
+            .collect();
+        print_double_sided_boards(&mut out, "PAWN_ATTACKS", &white_attacks, &black_attacks)?;
+    }
+
+    {
+        let moves: Vec<_> = Square::iter().map(king_moves).collect();
+        print_boards(&mut out, "KING_MOVES", &moves)?;
+        let king_blockers: Vec<_> = Color::iter()
+            .map(|color| {
+                Square::new(File::F, color.first_rank()) | Square::new(File::G, color.first_rank())
+            })
+            .collect();
+        let queen_blockers: Vec<_> = Color::iter()
+            .map(|color| {
+                Square::new(File::B, color.first_rank())
+                    | Square::new(File::C, color.first_rank())
+                    | Square::new(File::D, color.first_rank())
+            })
+            .collect();
+        print_boards(&mut out, "KING_SIDE_CASTLE_BLOCKERS", &king_blockers)?;
+        print_boards(&mut out, "QUEEN_SIDE_CASTLE_BLOCKERS", &queen_blockers)?;
+    }
+
+    Ok(())
+}