Better way to display errors

lib/PgWhyUpgrade.pm

@@ -19,6 +19,7 @@ sub startup {
 
     # Normal route to controller
     $r->get( '/' )->to( 'main#home' )->name( 'home' );
+    $r->get( '/error' )->to( 'main#error' )->name( 'error' );
     $r->get( '/show' )->to( 'main#show' )->name( 'show' );
     $r->get( '/metainfo' )->to( 'main#metainfo' )->name( 'metainfo' );
 }

lib/PgWhyUpgrade/Controller/Main.pm

@@ -16,17 +16,34 @@ sub home {
 sub show_validate {
     my $self = shift;
 
-    my $from = $self->param( 'from' );
-    my $to   = $self->param( 'to' );
+    my $from = $self->param( 'from' ) // '';
+    my $to   = $self->param( 'to' ) // '';
 
     # Validate that the versions given as from/to are ok
-    return $self->redirect_to( 'home' ) unless $from;
-    return $self->redirect_to( 'home' ) unless $from =~ m{\A\d+(\.\d+){0,2}\z};
-    return $self->redirect_to( 'home' ) unless $to;
-    return $self->redirect_to( 'home' ) unless $to =~ m{\A\d+(\.\d+){0,2}\z};
-    return $self->redirect_to( 'home' ) unless $self->db->valid_release( $from );
-    return $self->redirect_to( 'home' ) unless $self->db->valid_release( $to );
-    return $self->redirect_to( 'home' ) unless $from ne $to;
+    my @bad_versions = ();
+    unless (
+        ( $from =~ m{\A\d+(\.\d+){0,2}\z} ) &&
+        ( $self->db->valid_release( $from ) )
+    ) {
+        push @bad_versions, $from;
+    }
+    unless (
+        ( $to =~ m{\A\d+(\.\d+){0,2}\z} ) &&
+        ( $self->db->valid_release( $to ) )
+    ) {
+        push @bad_versions, $to;
+    }
+    if ( 0 < scalar @bad_versions ) {
+        $self->flash( 'msg' => 'bad_versions' );
+        $self->flash( 'vers' => \@bad_versions );
+        return $self->redirect_to( 'error' );
+    }
+
+    if ( $from eq $to ) {
+        $self->flash( 'msg' => 'same_version' );
+        $self->flash( 'ver' => $from );
+        return $self->redirect_to( 'error' );
+    }
 
     # Check if we don't need to swap from/to
     my $o_from = Pg::Version->new( $from );

public/css/style.css

@@ -228,3 +228,17 @@ p {
     padding: 0;
     padding-left: 1em;
 }
+#error {
+    color: #fc0;
+    border: 1px solid #f40;
+    margin: 1em 3em 0em 3em;
+    padding: 1em;
+    background: #400;
+}
+#error h1 {
+    padding: 0;
+    margin: 0;
+}
+#error span {
+    color: #ff0;
+}

templates/main/error.html.ep

+% layout 'default';
+<div id="error">
+    % if ( flash('msg') eq 'same_version' ) {
+        <h1>You tried to display diff from the same version to the same version (<span><%= flash('ver') %></span>)</h2>
+
+    % } elsif ( flash('msg') eq 'bad_versions' ) {
+        % if ( 1 == scalar @{ flash('vers') } ) {
+        <h1>Given version (<span><%= flash('vers')->[0] %></span>) is incorrect.</h1>
+        % } else {
+        <h1>Given versions (<span><%= join ', ', @{ flash('vers') } %></span>) are incorrect.</h1>
+        % }
+
+    % } else {
+        <h1>Something bad happened, but not sure what, sorry.</h2>
+    % }
+</div>