Guide AI by heuristic evaluation; "best first search"

fish/src/ai.rs

@@ -1,6 +1,6 @@
 //! AI engine.
 
-use crate::find;
+use crate::{eval, find};
 use alloc::vec::Vec;
 use core::{future::Future, pin::Pin, task::Poll};
 use mino::srs::{Piece, PieceType};
@@ -15,6 +15,20 @@ pub struct Ai {
     cur_mat: MatBuf,
 }
 
+fn evaluate(mat: &Mat, depth: usize) -> i32 {
+    let w_height = 5;
+    let w_ideps = 10;
+    let w_mdse = 10;
+    let w_pc = 10;
+
+    let mut rating = 0;
+    rating += eval::max_height(mat) * w_height;
+    rating += eval::i_deps(mat) * w_ideps;
+    rating += eval::mystery_mdse(mat) * w_mdse;
+    rating += (depth as i32) * w_pc;
+    rating
+}
+
 impl Ai {
     // TODO: personality config
     pub fn new() -> Self {
@@ -50,18 +64,33 @@ impl Ai {
         }
 
         let ty = self.root_previews[depth];
-        let loc = {
-            let mut fl = find::find_locations(&self.cur_mat, ty, find::cap::All);
-            match fl.nth(0) {
-                Some(loc) => loc,
-                None => return true, // game over
+        let locs = find::find_locations(&self.cur_mat, ty, find::cap::All);
+        let pcs = locs.map(|loc| Piece { ty, loc });
+
+        let mut rate_mat: MatBuf = MatBuf::new();
+        let mut best_mat: MatBuf = MatBuf::new();
+        let mut best: Option<(i32, Piece)> = None;
+
+        for pc in pcs {
+            rate_mat.copy_from(&self.cur_mat);
+            pc.cells().fill(&mut rate_mat);
+            rate_mat.clear_lines();
+            let rating = evaluate(&rate_mat, depth);
+
+            let best_rating = best.clone().map_or(i32::MAX, |(r, _)| r);
+            if rating < best_rating {
+                best = Some((rating, pc));
+                best_mat.copy_from(&rate_mat);
             }
+        }
+
+        let pc = match best {
+            Some((_, pc)) => pc,
+            None => return true, // no locations; game over
         };
 
-        let piece = Piece { ty, loc };
-        piece.cells().fill(&mut self.cur_mat);
-        self.path.push(piece);
-
+        self.path.push(pc);
+        self.cur_mat.copy_from(&best_mat);
         false
     }