From 90fa73099e7ada2b1ed7c164207dceefe351a47c Mon Sep 17 00:00:00 2001
From: Alex Karle <alex@karle.co>
Date: Sat, 4 Apr 2020 00:22:26 -0400
Subject: [PATCH] Euchre::Dealer: [refactor] Add handler phase/turn validation

I found myself over the last couple commits copy/pasting the same "Not
your turn" message, and thought -- huh, it'd be nice if we never even
GOT here if we knew it was a turn-based action.

And whallah -- I present a beautifully complex dispatcher that has both
phase and turn checking built in! This works really nicely in practice,
and makes it easier to write the handlers, knowing that the game state
is correct.

Am I proud of it? Maybe
---
 lib/Euchre/Dealer.pm | 83 +++++++++++++++++++++++++++++++++++++++++++++--------------------------------------
 1 file changed, 45 insertions(+), 38 deletions(-)

diff --git a/lib/Euchre/Dealer.pm b/lib/Euchre/Dealer.pm
index 3f19b65..3326f33 100644
--- a/lib/Euchre/Dealer.pm
+++ b/lib/Euchre/Dealer.pm
@@ -94,21 +94,38 @@ sub gloaters_never_win {
 sub handle_msg {
     my ($cid, $msg) = @_;
 
+    # Crazy magic dispatch of
+    #
+    #   action => [ handler, req-phase, phase-err, needs-turn ]
+    #
+    # The last three are optional, but are useful to dedupe common
+    # assertions (like, needs to be their turn)
     my %dispatch = (
         # Game management endpoints
-        join_game   => \&join_game,
-        take_seat   => \&take_seat,
-        stand_up    => \&stand_up,
-        start_game  => \&start_game,
-        vote_trump  => \&vote_trump,
-        play_card   => \&play_card,
+        join_game   => [\&join_game],
+        take_seat   => [\&take_seat, 'lobby', "Can't change seats during game"],
+        stand_up    => [\&stand_up, 'lobby', "Can't change seats during game"],
+        start_game  => [\&start_game, 'lobby', "Game already started"],
+
+        # Gameplay
+        vote_trump  => [\&vote_trump, 'vote', "Not time for a vote", 1],
+        play_card   => [\&play_card, 'play', "Can't play cards yet", 1],
     );
 
-    if (exists $dispatch{$msg->{action}}) {
-        $dispatch{$msg->{action}}->($PLAYERS{$cid}, $msg);
-    } else {
+
+    if (!exists $dispatch{$msg->{action}}) {
         die "Unknown API action: $msg->{action}";
     }
+
+    my $p = $PLAYERS{$cid};
+    my ($handler, $req_phase, $phase_err, $turn_based) = @{$dispatch{$msg->{action}}};
+    if ($req_phase && ($p->{game}->{phase} ne $req_phase)) {
+        send_error($p, $phase_err);
+    } elsif ($turn_based && ($p->{seat} != $p->{game}->{turn})) {
+        send_error($p, "Not your turn!");
+    } else {
+        $handler->($p, $msg);
+    }
 }
 
 # player_name
@@ -254,30 +271,26 @@ sub vote_trump {
     my ($p, $msg) = @_;
 
     my $game = $p->{game};
-    if ($game->{turn} != $p->{seat}) {
-        send_error("Not your turn!");
-    } else {
-        if ($msg->{vote} eq 'pass') {
-            $game->{turn} = ($game->{turn} + 1 % 4);
-            $game->{pass_count}++;
-            if ($game->{pass_count} >= 8) {
-                # Throw em in
-                start_new_round($game);
-            } else {
-                broadcast_gamestate($game);
-            }
-        } elsif (defined suit_to_id($msg->{vote})) {
-            # XXX handle loner (needs to handle next-player)
-            # NOTE: we let clients decide what's kosher to vote
-            # based on their hand state, pass_count
-            $game->{trump} = suit_to_id($msg->{vote});
-            $game->{caller} = $p->{seat};
-            $game->{phase} = 'play';
-            $game->{turn} = ($game->{dealer} + 1 % 4);
-            broadcast_gamestate($game);
+    if ($msg->{vote} eq 'pass') {
+        $game->{turn} = ($game->{turn} + 1 % 4);
+        $game->{pass_count}++;
+        if ($game->{pass_count} >= 8) {
+            # Throw em in
+            start_new_round($game);
         } else {
-            send_error("Bad vote");
+            broadcast_gamestate($game);
         }
+    } elsif (defined suit_to_id($msg->{vote})) {
+        # XXX handle loner (needs to handle next-player)
+        # NOTE: we let clients decide what's kosher to vote
+        # based on their hand state, pass_count
+        $game->{trump} = suit_to_id($msg->{vote});
+        $game->{caller} = $p->{seat};
+        $game->{phase} = 'play';
+        $game->{turn} = ($game->{dealer} + 1 % 4);
+        broadcast_gamestate($game);
+    } else {
+        send_error("Bad vote");
     }
 }
 
@@ -289,12 +302,6 @@ sub play_card {
     my $game = $p->{game};
     my $seat = $p->{seat};
 
-    # Make sure we all behave
-    if ($p->{seat} != $game->{turn}) {
-        send_error("Not your turn");
-        return;
-    }
-
     # Update the table and current player
     push @{$game->{table}}, $msg->{card};
     $game->{turn} = ($game->{turn} + 1 % 4); # XXX: loner turn
@@ -329,7 +336,7 @@ sub play_card {
 
 sub signal_game_end {
     my ($game) = @_;
-    
+
     # TODO: send message with winners and end the game
     # (maybe put game no longer in progress?)
     $game->{phase} = 'end';
--
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