Revise error messages to include Linux debugging help

app/Exceptions/DockerMissingException.php

@@ -15,7 +15,7 @@ public function render($request = null): void
         $console->line('');
         $console->line($shell->formatErrorMessage('Docker is not installed.'));
         $console->line('');
-        $console->line($shell->formatErrorMessage('Please visit https://docs.docker.com/docker-for-mac/install/'));
+        $console->line($shell->formatErrorMessage('Please visit https://docs.docker.com/get-docker/'));
         $console->line($shell->formatErrorMessage('for information on how to install Docker for your machine.'));
     }
 }

app/Exceptions/DockerNotAvailableException.php

@@ -0,0 +1,58 @@
+<?php
+
+namespace App\Exceptions;
+
+use App\Shell\Environment;
+use App\Shell\Shell;
+use Exception;
+
+class DockerNotAvailableException extends Exception
+{
+    public function render($request = null): void
+    {
+        $console = app('console');
+        $shell = app(Shell::class);
+
+        $console->line('');
+        $console->line($shell->formatErrorMessage('Docker is not available.'));
+        $console->line('');
+
+        if (in_array(PHP_OS_FAMILY, ['Darwin', 'Linux', 'Windows'])) {
+            $osSpecificHelp = 'helpFor' . ucfirst(PHP_OS_FAMILY);
+            $this->$osSpecificHelp($console);
+        }
+    }
+
+    protected function helpForDarwin($console)
+    {
+        $console->line('Open Docker for Mac or run:');
+        $console->line('  open --background -a Docker');
+        $console->line('to start the Docker service.');
+    }
+
+    protected function helpForLinux($console)
+    {
+        $environment = app(Environment::class);
+        $shell = app(Shell::class);
+
+        $console->line('Verify that the Docker service is running:');
+        $console->line('  sudo systemctl status docker');
+        $console->line('Start the Docker service:');
+        $console->line('  sudo systemctl start docker');
+
+        if (! $environment->userIsInDockerGroup()) {
+            $console->line('');
+            $console->line($shell->formatErrorMessage('You are not in the docker group.'));
+            $console->line('');
+            $console->line('This is required to run Docker as a non-root user.');
+            $console->line('Add your user to the docker group by running:');
+            $console->line('  sudo usermod -aG docker ${USER}');
+            $console->line('and restart your session.');
+        }
+    }
+
+    protected function helpForWindows($console)
+    {
+        $console->line('Open Docker for Windows to start the Docker service.');
+    }
+}

app/InitializesCommands.php

@@ -3,7 +3,7 @@
 namespace App;
 
 use App\Exceptions\DockerMissingException;
-use App\Exceptions\DockerNotRunningException;
+use App\Exceptions\DockerNotAvailableException;
 use App\Shell\Docker;
 
 trait InitializesCommands
@@ -19,7 +19,7 @@ public function initializeCommand(): void
         }
 
         if (! app(Docker::class)->isDockerServiceRunning()) {
-            throw new DockerNotRunningException;
+            throw new DockerNotAvailableException;
         }
     }
 }

app/Shell/Environment.php

@@ -52,4 +52,9 @@ public function netstatCmd(): string
 
         return $netstatCmd;
     }
+
+    public function userIsInDockerGroup(): bool
+    {
+        return $this->shell->execQuietly('groups | grep docker')->isSuccessful();
+    }
 }