now the system folder will also be versioned

.gitignore

@@ -41,4 +41,4 @@ Thumbs.db
 /dist-sass/
 /js/coverage/
 /node_modules/
-/system/
+

system/.htaccess

@@ -0,0 +1,6 @@
+<IfModule authz_core_module>
+	Require all denied
+</IfModule>
+<IfModule !authz_core_module>
+	Deny from all
+</IfModule>

system/API/ResponseTrait.php

@@ -0,0 +1,359 @@
+<?php
+
+/**
+ * This file is part of CodeIgniter 4 framework.
+ *
+ * (c) CodeIgniter Foundation <admin@codeigniter.com>
+ *
+ * For the full copyright and license information, please view
+ * the LICENSE file that was distributed with this source code.
+ */
+
+namespace CodeIgniter\API;
+
+use CodeIgniter\Format\FormatterInterface;
+use CodeIgniter\HTTP\IncomingRequest;
+use CodeIgniter\HTTP\ResponseInterface;
+use Config\Services;
+
+/**
+ * Provides common, more readable, methods to provide
+ * consistent HTTP responses under a variety of common
+ * situations when working as an API.
+ */
+trait ResponseTrait
+{
+    /**
+     * Allows child classes to override the
+     * status code that is used in their API.
+     *
+     * @var array<string, int>
+     */
+    protected $codes = [
+        'created'                   => 201,
+        'deleted'                   => 200,
+        'updated'                   => 200,
+        'no_content'                => 204,
+        'invalid_request'           => 400,
+        'unsupported_response_type' => 400,
+        'invalid_scope'             => 400,
+        'temporarily_unavailable'   => 400,
+        'invalid_grant'             => 400,
+        'invalid_credentials'       => 400,
+        'invalid_refresh'           => 400,
+        'no_data'                   => 400,
+        'invalid_data'              => 400,
+        'access_denied'             => 401,
+        'unauthorized'              => 401,
+        'invalid_client'            => 401,
+        'forbidden'                 => 403,
+        'resource_not_found'        => 404,
+        'not_acceptable'            => 406,
+        'resource_exists'           => 409,
+        'conflict'                  => 409,
+        'resource_gone'             => 410,
+        'payload_too_large'         => 413,
+        'unsupported_media_type'    => 415,
+        'too_many_requests'         => 429,
+        'server_error'              => 500,
+        'unsupported_grant_type'    => 501,
+        'not_implemented'           => 501,
+    ];
+
+    /**
+     * How to format the response data.
+     * Either 'json' or 'xml'. If blank will be
+     * determined through content negotiation.
+     *
+     * @var string
+     */
+    protected $format = 'json';
+
+    /**
+     * Current Formatter instance. This is usually set by ResponseTrait::format
+     *
+     * @var FormatterInterface|null
+     */
+    protected $formatter;
+
+    /**
+     * Provides a single, simple method to return an API response, formatted
+     * to match the requested format, with proper content-type and status code.
+     *
+     * @param array|string|null $data
+     *
+     * @return ResponseInterface
+     */
+    protected function respond($data = null, ?int $status = null, string $message = '')
+    {
+        if ($data === null && $status === null) {
+            $status = 404;
+            $output = null;
+            $this->format($data);
+        } elseif ($data === null && is_numeric($status)) {
+            $output = null;
+            $this->format($data);
+        } else {
+            $status = empty($status) ? 200 : $status;
+            $output = $this->format($data);
+        }
+
+        if ($output !== null) {
+            if ($this->format === 'json') {
+                return $this->response->setJSON($output)->setStatusCode($status, $message);
+            }
+
+            if ($this->format === 'xml') {
+                return $this->response->setXML($output)->setStatusCode($status, $message);
+            }
+        }
+
+        return $this->response->setBody($output)->setStatusCode($status, $message);
+    }
+
+    /**
+     * Used for generic failures that no custom methods exist for.
+     *
+     * @param array|string $messages
+     * @param int          $status   HTTP status code
+     * @param string|null  $code     Custom, API-specific, error code
+     *
+     * @return ResponseInterface
+     */
+    protected function fail($messages, int $status = 400, ?string $code = null, string $customMessage = '')
+    {
+        if (! is_array($messages)) {
+            $messages = ['error' => $messages];
+        }
+
+        $response = [
+            'status'   => $status,
+            'error'    => $code ?? $status,
+            'messages' => $messages,
+        ];
+
+        return $this->respond($response, $status, $customMessage);
+    }
+
+    // --------------------------------------------------------------------
+    // Response Helpers
+    // --------------------------------------------------------------------
+
+    /**
+     * Used after successfully creating a new resource.
+     *
+     * @param array|string|null $data
+     *
+     * @return ResponseInterface
+     */
+    protected function respondCreated($data = null, string $message = '')
+    {
+        return $this->respond($data, $this->codes['created'], $message);
+    }
+
+    /**
+     * Used after a resource has been successfully deleted.
+     *
+     * @param array|string|null $data
+     *
+     * @return ResponseInterface
+     */
+    protected function respondDeleted($data = null, string $message = '')
+    {
+        return $this->respond($data, $this->codes['deleted'], $message);
+    }
+
+    /**
+     * Used after a resource has been successfully updated.
+     *
+     * @param array|string|null $data
+     *
+     * @return ResponseInterface
+     */
+    protected function respondUpdated($data = null, string $message = '')
+    {
+        return $this->respond($data, $this->codes['updated'], $message);
+    }
+
+    /**
+     * Used after a command has been successfully executed but there is no
+     * meaningful reply to send back to the client.
+     *
+     * @return ResponseInterface
+     */
+    protected function respondNoContent(string $message = 'No Content')
+    {
+        return $this->respond(null, $this->codes['no_content'], $message);
+    }
+
+    /**
+     * Used when the client is either didn't send authorization information,
+     * or had bad authorization credentials. User is encouraged to try again
+     * with the proper information.
+     *
+     * @return ResponseInterface
+     */
+    protected function failUnauthorized(string $description = 'Unauthorized', ?string $code = null, string $message = '')
+    {
+        return $this->fail($description, $this->codes['unauthorized'], $code, $message);
+    }
+
+    /**
+     * Used when access is always denied to this resource and no amount
+     * of trying again will help.
+     *
+     * @return ResponseInterface
+     */
+    protected function failForbidden(string $description = 'Forbidden', ?string $code = null, string $message = '')
+    {
+        return $this->fail($description, $this->codes['forbidden'], $code, $message);
+    }
+
+    /**
+     * Used when a specified resource cannot be found.
+     *
+     * @return ResponseInterface
+     */
+    protected function failNotFound(string $description = 'Not Found', ?string $code = null, string $message = '')
+    {
+        return $this->fail($description, $this->codes['resource_not_found'], $code, $message);
+    }
+
+    /**
+     * Used when the data provided by the client cannot be validated.
+     *
+     * @return ResponseInterface
+     *
+     * @deprecated Use failValidationErrors instead
+     */
+    protected function failValidationError(string $description = 'Bad Request', ?string $code = null, string $message = '')
+    {
+        return $this->fail($description, $this->codes['invalid_data'], $code, $message);
+    }
+
+    /**
+     * Used when the data provided by the client cannot be validated on one or more fields.
+     *
+     * @param string|string[] $errors
+     *
+     * @return ResponseInterface
+     */
+    protected function failValidationErrors($errors, ?string $code = null, string $message = '')
+    {
+        return $this->fail($errors, $this->codes['invalid_data'], $code, $message);
+    }
+
+    /**
+     * Use when trying to create a new resource and it already exists.
+     *
+     * @return ResponseInterface
+     */
+    protected function failResourceExists(string $description = 'Conflict', ?string $code = null, string $message = '')
+    {
+        return $this->fail($description, $this->codes['resource_exists'], $code, $message);
+    }
+
+    /**
+     * Use when a resource was previously deleted. This is different than
+     * Not Found, because here we know the data previously existed, but is now gone,
+     * where Not Found means we simply cannot find any information about it.
+     *
+     * @return ResponseInterface
+     */
+    protected function failResourceGone(string $description = 'Gone', ?string $code = null, string $message = '')
+    {
+        return $this->fail($description, $this->codes['resource_gone'], $code, $message);
+    }
+
+    /**
+     * Used when the user has made too many requests for the resource recently.
+     *
+     * @return ResponseInterface
+     */
+    protected function failTooManyRequests(string $description = 'Too Many Requests', ?string $code = null, string $message = '')
+    {
+        return $this->fail($description, $this->codes['too_many_requests'], $code, $message);
+    }
+
+    /**
+     * Used when there is a server error.
+     *
+     * @param string      $description The error message to show the user.
+     * @param string|null $code        A custom, API-specific, error code.
+     * @param string      $message     A custom "reason" message to return.
+     */
+    protected function failServerError(string $description = 'Internal Server Error', ?string $code = null, string $message = ''): ResponseInterface
+    {
+        return $this->fail($description, $this->codes['server_error'], $code, $message);
+    }
+
+    // --------------------------------------------------------------------
+    // Utility Methods
+    // --------------------------------------------------------------------
+
+    /**
+     * Handles formatting a response. Currently makes some heavy assumptions
+     * and needs updating! :)
+     *
+     * @param array|string|null $data
+     *
+     * @return string|null
+     */
+    protected function format($data = null)
+    {
+        // If the data is a string, there's not much we can do to it...
+        if (is_string($data)) {
+            // The content type should be text/... and not application/...
+            $contentType = $this->response->getHeaderLine('Content-Type');
+            $contentType = str_replace('application/json', 'text/html', $contentType);
+            $contentType = str_replace('application/', 'text/', $contentType);
+            $this->response->setContentType($contentType);
+            $this->format = 'html';
+
+            return $data;
+        }
+
+        $format = Services::format();
+        $mime   = "application/{$this->format}";
+
+        // Determine correct response type through content negotiation if not explicitly declared
+        if (
+            (empty($this->format) || ! in_array($this->format, ['json', 'xml'], true))
+            && $this->request instanceof IncomingRequest
+        ) {
+            $mime = $this->request->negotiate(
+                'media',
+                $format->getConfig()->supportedResponseFormats,
+                false
+            );
+        }
+
+        $this->response->setContentType($mime);
+
+        // if we don't have a formatter, make one
+        if (! isset($this->formatter)) {
+            // if no formatter, use the default
+            $this->formatter = $format->getFormatter($mime);
+        }
+
+        if ($mime !== 'application/json') {
+            // Recursively convert objects into associative arrays
+            // Conversion not required for JSONFormatter
+            $data = json_decode(json_encode($data), true);
+        }
+
+        return $this->formatter->format($data);
+    }
+
+    /**
+     * Sets the format the response should be in.
+     *
+     * @return $this
+     */
+    protected function setResponseFormat(?string $format = null)
+    {
+        $this->format = strtolower($format);
+
+        return $this;
+    }
+}