Initial data commit

Task/Tic-tac-toe/SQL/tic-tac-toe.sql

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+--Setup
+drop table if exists board;
+create table board (p char, r integer, c integer);
+insert into board values('.', 0, 0),('.', 0, 1),('.', 0, 2),('.', 1, 0),('.', 1, 1),('.', 1, 2),('.', 2, 0),('.', 2, 1),('.', 2, 2);
+
+
+-- Use a trigger for move events
+drop trigger if exists after_moved;
+create trigger after_moved after update on board for each row when new.p <> '.' and new.p <> 'O'
+begin
+
+    -- Verify move is valid
+    select
+        case
+            when (select v from msg) like '%Wins!' then raise(ABORT, 'The game is already over.')
+            when (select old.p from board where rowid = rid) <> '.' then raise(ABORT, 'That position has already been taken.  Please choose an available position.')
+            when new.p <> 'X' then raise(ABORT, 'Please place an ''X''')
+        end
+    from (
+        select rowid rid from board
+        where p = new.p
+        except
+        select p from board where p = old.p
+    );
+
+
+    -- Check for game over
+    update msg set v = (
+        select
+            case
+                when max(num) >= 3 then 'X Wins!'
+                when (select count(*) from board where p = '.') = 0 then 'Cat Wins!'
+                else 'Move made'
+            end
+        from ( -- Is Game Over
+            select count(*) num from board where p = 'X' group by r union -- Horz
+            select count(*) num from board where p = 'X' group by c union -- Vert
+            select count(*) num from board where p = 'X' and r = c union -- Diag TL->BR
+            select count(*) num from board where p = 'X' and (2-r) = c -- Diag TR->BL
+        )
+    );
+
+
+    --Have computer player make a random move
+    update board set p = 'O'
+    where rowid = (select rid from (select max(rnd),rid from (select rowid rid, random() rnd from board where p = '.')))
+    and (select v from msg) not like '%Wins!';
+    --NOTE: SQLite doesn't allow update order by in triggers, otherwise we could just use this beautiful line:
+    -- update board set p = 'O' where p = '.' order by random() limit 1;
+
+    --Check to see if the computer player won
+    update msg set v = (
+        select
+            case
+                when max(num) >= 3 then 'O Wins!'
+                else v
+            end
+        from ( -- Is Game Over
+            select count(*) num from board where p = 'O' group by r union -- Horz
+            select count(*) num from board where p = 'O' group by c union -- Vert
+            select count(*) num from board where p = 'O' and r = c union -- Diag TL->BR
+            select count(*) num from board where p = 'O' and (2-r) = c -- Diag TR->BL
+        )
+    );
+
+
+end;
+
+-- UI to display the logical board as a grid
+drop view if exists ui;
+create view ui as
+select case when p = '.' then col0.rowid else p end c0, c1, c2
+from board as col0
+join (select case when p = '.' then board.rowid else p end c1, r from board where c = 1) as col1 on col0.r = col1.r
+join (select case when p = '.' then board.rowid else p end  c2, r from board where c = 2) as col2 on col0.r = col2.r
+where c = 0;
+
+drop table if exists msg;
+create table msg (v text);
+insert into msg values('');
+
+-- Readme
+select * from ui;
+.print "Use this to play:"
+.print "->update board set p = 'X' where rowid = ?; select * from ui; select * from msg;"'