From 41bd08f25c22fa2b31067e7ee380a7fa628e8d80 Mon Sep 17 00:00:00 2001
From: Andreas Schaafsma <the.hion.v@gmail.com>
Date: Sat, 4 Oct 2025 01:12:34 +0200
Subject: [PATCH] Implement line clearing

---
 tetris.c | 43 +++++++++++++++++++++++++++++++++++++++++++
 tetris.h |  3 +++
 2 files changed, 46 insertions(+)

diff --git a/tetris.c b/tetris.c
index 5688f58..2454c39 100644
--- a/tetris.c
+++ b/tetris.c
@@ -93,6 +93,48 @@ void zero_piece_mask(){
     }
 }
 
+void bool_array_fill(bool* target, int len, bool val){
+    for(int i = 0; i < len; i++){
+        target[i] = val;
+    }
+}
+
+void get_filled_lines(bool* target){
+    bool_array_fill(target, BOARD_HEIGHT, 0);
+    bool filled_line_array[BOARD_WIDTH] = {[0 ... BOARD_WIDTH-1] = 1};
+    // loop over board lines
+    for(int iter_y = 0; iter_y < BOARD_HEIGHT; iter_y++){
+        if(memcmp(board_mask[iter_y], filled_line_array, sizeof(bool)*BOARD_WIDTH) == 0){
+            target[iter_y] = 1;
+            continue;    
+        }
+    }
+}
+
+void clear_lines(){
+    bool filled_lines[BOARD_HEIGHT] = {0};
+    get_filled_lines(filled_lines);
+    int offset_lines = 0; // count the offset we need to keep when checking the rest of the lines
+    for(int line = BOARD_HEIGHT - 1; line > 0; line--){
+        
+        int hitline = line+offset_lines;
+        if(!filled_lines[line]) // The line we are iterating over is not filled
+        {
+            continue;
+        }
+
+        // shift all lines down one starting at hitline
+        for(int shift_line = hitline; shift_line > 0; shift_line--){
+            for(int iter_x = 0; iter_x < BOARD_WIDTH; iter_x++){
+                board[shift_line][iter_x] = board[shift_line-1][iter_x];
+                board_mask[shift_line][iter_x] = board_mask[shift_line-1][iter_x];
+            }
+        }
+        // All the lines are now shifted down (moved to higher index) so we need to start shifting offset by +1 now.
+        offset_lines++;
+    }
+}
+
 void populate_board_mask(){
     for(int i = 0; i < BOARD_HEIGHT; i++){
         for(int j = 0; j < BOARD_WIDTH; j++){
@@ -399,6 +441,7 @@ void game_tick(){
     place_piece();
     zero_piece_mask(); 
     populate_board_mask();
+    clear_lines();
     spawn_piece();
 }
 
diff --git a/tetris.h b/tetris.h
index a0882e8..be94811 100644
--- a/tetris.h
+++ b/tetris.h
@@ -161,6 +161,9 @@ void game_tick();
 void debugDraw(int x, int y, Color color);
 void debug_draw_blocks(Vector2 block_vecs[], Color color);
 void debug_draw_blocks_on_axis(Vector2 block_vecs[], Color color);
+void bool_array_fill(bool* target, int len, bool val);
+void get_filled_lines(bool* target);
+void clear_lines();
 void draw();
 void update();
 void init_game();