From 770f14609849552d965b4e9101bfb5c0870c08d0 Mon Sep 17 00:00:00 2001
From: Justin Worthe <justin@worthe-it.co.za>
Date: Mon, 8 Jul 2019 22:31:41 +0200
Subject: Command filtering to avoid wasting the selects

---
 src/game.rs               |  4 ++--
 src/geometry/direction.rs | 25 +++++++++++--------------
 src/strategy.rs           |  7 ++++---
 src/strategy/minimax.rs   | 37 ++++++++++++++++++++++++++++++-------
 4 files changed, 47 insertions(+), 26 deletions(-)

diff --git a/src/game.rs b/src/game.rs
index 4e074ea..c31f64f 100644
--- a/src/game.rs
+++ b/src/game.rs
@@ -458,7 +458,7 @@ impl GameBoard {
     }
 
     pub fn valid_moves_for_worm(&self, worm: &Worm) -> ArrayVec<[Action; 8]> {
-        Direction::all()
+        Direction::ALL
             .iter()
             .map(Direction::as_vec)
             .map(|d| worm.position + d)
@@ -491,7 +491,7 @@ impl GameBoard {
     }
 
     pub fn valid_shoot_commands(&self, player_index: usize) -> ArrayVec<[Command; 24]> {
-        let all_dirs = Direction::all();
+        let all_dirs = Direction::ALL;
         let no_select = all_dirs.iter().map(|d| Command::new(Action::Shoot(*d)));
 
         self.valid_selects(player_index)
diff --git a/src/geometry/direction.rs b/src/geometry/direction.rs
index 737bd00..d3f3b20 100644
--- a/src/geometry/direction.rs
+++ b/src/geometry/direction.rs
@@ -1,5 +1,5 @@
-use std::fmt;
 use crate::geometry::vec::Vec2d;
+use std::fmt;
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
 pub enum Direction {
@@ -54,17 +54,14 @@ impl Direction {
         }
     }
 
-    pub fn all() -> [Direction; 8] {
-        use Direction::*;
-        [
-            North,
-            NorthEast,
-            East,
-            SouthEast,
-            South,
-            SouthWest,
-            West,
-            NorthWest,
-        ]
-    }
+    pub const ALL: [Direction; 8] = [
+        Direction::North,
+        Direction::NorthEast,
+        Direction::East,
+        Direction::SouthEast,
+        Direction::South,
+        Direction::SouthWest,
+        Direction::West,
+        Direction::NorthWest,
+    ];
 }
diff --git a/src/strategy.rs b/src/strategy.rs
index 9c79d60..b6069a1 100644
--- a/src/strategy.rs
+++ b/src/strategy.rs
@@ -1,4 +1,5 @@
-mod mcts;
-mod minimax;
+//mod mcts;
+//pub use mcts::{choose_move, Node};
 
-pub use mcts::{choose_move, Node};
+mod minimax;
+pub use minimax::{choose_move, Node};
diff --git a/src/strategy/minimax.rs b/src/strategy/minimax.rs
index 2ed84b2..31e58a0 100644
--- a/src/strategy/minimax.rs
+++ b/src/strategy/minimax.rs
@@ -23,7 +23,7 @@ pub fn choose_move(
             .children
             .drain()
             .map(|(_k, n)| n)
-            .find(|n| false) // TODO: Identify the last opponent move to use this cache
+            .find(|_n| false) // TODO: Identify the last opponent move to use this cache
             .unwrap_or_else(|| {
                 eprintln!("Previous round did not appear in the cache");
                 Node {
@@ -227,14 +227,37 @@ fn update(node: &mut Node, commands: [Command; 2], score: Score) {
 }
 
 fn pruned_moves(state: &GameBoard, player_index: usize) -> Vec<Command> {
-    // TODO: Play one move into the future and make sure this doesn't
-    // hurt me or do something dumb? Should I rather specialize this
-    // to each type of move?
+    let sim_with_idle_opponent = |cmd| {
+        let mut idle_commands = [
+            Command::new(Action::DoNothing),
+            Command::new(Action::DoNothing),
+        ];
+        idle_commands[player_index] = cmd;
+        let mut state_cpy = state.clone();
+        state_cpy.simulate(idle_commands);
+        state_cpy
+    };
+
+    let opponent_index = GameBoard::opponent(player_index);
+    let my_starting_health = state.players[player_index].health();
+    let opponent_starting_health = state.players[opponent_index].health();
 
-    // TODO: Ensure that there are at least some moves left here. If
-    // there's nothing, at least return a vector that contains a
-    // nothing move.
     valid_moves(state, player_index)
+        .into_iter()
+        .filter(|command| {
+            //NB: These rules should pass for doing nothing, otherwise
+            // we need some other mechanism for sticking in a do
+            // nothing option
+
+            let idle_opponent_state = sim_with_idle_opponent(*command);
+            let hurt_self = idle_opponent_state.players[player_index].health() < my_starting_health;
+            let hurt_opponent =
+                idle_opponent_state.players[opponent_index].health() < opponent_starting_health;
+            let is_select = command.worm.is_some();
+
+            !hurt_self && (!is_select || hurt_opponent)
+        })
+        .collect()
 }
 
 fn valid_moves(state: &GameBoard, player_index: usize) -> Vec<Command> {
-- 
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