From 4fe231fcc252f19e3fa5e50d369571f1caf6ad33 Mon Sep 17 00:00:00 2001
From: Tom Barrett <tom@tombarrett.xyz>
Date: Sat, 20 Mar 2021 15:35:18 +0100
Subject: gems now fall

---
 src/main.rs | 37 ++++++++++++++++++++++++++++++++++---
 1 file changed, 34 insertions(+), 3 deletions(-)

diff --git a/src/main.rs b/src/main.rs
index f3d41b0..56f2ea9 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -5,7 +5,7 @@ use rand::{
     Rng,
 };
 
-#[derive(Debug, PartialEq)]
+#[derive(Debug, PartialEq, Clone)]
 enum Occupant {
     None,
     Green,
@@ -38,7 +38,7 @@ impl Distribution<Occupant> for Standard {
     }
 }
 
-#[derive(Debug)]
+#[derive(Debug, Clone)]
 struct Cell {
     x: u8,
     y: u8,
@@ -55,7 +55,7 @@ impl Cell {
     }
 }
 
-fn cell_falling_system(mut cell_query: Query<(&mut Cell, &mut TextureAtlasSprite)>) {
+fn cell_insert_system(mut cell_query: Query<(&mut Cell, &mut TextureAtlasSprite)>) {
     for (mut cell, mut sprite) in cell_query.iter_mut() {
         if cell.occupant == Occupant::None {
             if cell.y == 7 {
@@ -66,6 +66,36 @@ fn cell_falling_system(mut cell_query: Query<(&mut Cell, &mut TextureAtlasSprite
     }
 }
 
+fn cell_falling_system(mut cell_query: Query<(&mut Cell, &mut TextureAtlasSprite)>) {
+    let mut have_gems = Vec::new();
+    for (cell, _sprite) in cell_query.iter_mut() {
+        if cell.occupant != Occupant::None {
+            have_gems.push(cell.clone());
+        }
+    }
+
+    let mut moved_gems = Vec::new();
+    for (mut cell, mut sprite) in cell_query.iter_mut() {
+        if cell.occupant == Occupant::None {
+            if let Some(c) = have_gems
+                .iter()
+                .find(|&c| (c.x, c.y) == (cell.x, cell.y + 1))
+            {
+                cell.occupant = c.occupant.clone();
+                sprite.index = cell.occupant.to_index();
+                moved_gems.push(c.clone());
+            }
+        }
+    }
+
+    for (mut cell, mut sprite) in cell_query.iter_mut() {
+        if moved_gems.iter().any(|c| (c.x, c.y) == (cell.x, cell.y)) {
+            cell.occupant = Occupant::None;
+            sprite.index = cell.occupant.to_index();
+        }
+    }
+}
+
 pub fn setup(
     commands: &mut Commands,
     asset_server: Res<AssetServer>,
@@ -148,6 +178,7 @@ pub struct GemsPlugin;
 impl Plugin for GemsPlugin {
     fn build(&self, app: &mut AppBuilder) {
         app.add_startup_system(setup.system());
+        app.add_system(cell_insert_system.system());
         app.add_system(cell_falling_system.system());
     }
 }
-- 
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