Refactor

15 files changed, 550 insertions, 313 deletions

diff --git a/.gitignore b/.gitignore
index a23bab3..da8b7b2 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,4 +1,5 @@
 /vendor/
 /content/
+/plugins/
 /config.toml
 
diff --git a/config.example.toml b/config.example.toml
index 64ecc4a..7d589d1 100644
--- a/config.example.toml
+++ b/config.example.toml
@@ -1,2 +1,3 @@
 [app]
 contentFolderPath = './content'
+pluginsFolderPath = './plugins'
diff --git a/public/index.php b/public/index.php
index b943298..8a7ec7d 100644
--- a/public/index.php
+++ b/public/index.php
@@ -1,11 +1,16 @@
 <?php
 
 use FlatFileForms\App;
+use FlatFileForms\PluginLoader;
+use FlatFileForms\PreLoader;
 use Yosymfony\Toml\Toml;
 
 require_once dirname(__DIR__) . '/vendor/autoload.php';
 
-function findAppConfigFile($path)
+/**
+ * Find the config file
+ */
+function findAppConfigFile(string $path): string
 {
   $currentDirectory = $path;
   while ($currentDirectory !== '/') {
@@ -20,17 +25,31 @@ function findAppConfigFile($path)
   die('config.toml missing');
 }
 
+// find and parse config
 $configFile = findAppConfigFile(dirname(__DIR__));
 $config = Toml::parseFile($configFile);
 
+// prepare possibly relative folders path
 chdir(dirname($configFile));
+
 $contentDirectoryPath = realpath($config['app']['contentFolderPath']);
 $contentDirectoryPath === false && die('Content folder "' . $config['app']['contentFolderPath'] . '" missing');
 $config['app']['contentFolderPath'] = $contentDirectoryPath;
+
+$pluginsDirectoryPath = realpath($config['app']['pluginsFolderPath']);
+$pluginsDirectoryPath === false && die('Plugins folder "' . $config['app']['pluginsFolderPath'] . '" missing');
+$config['app']['pluginsFolderPath'] = $pluginsDirectoryPath;
+
 chdir($_SERVER['DOCUMENT_ROOT']);
 
+// set config values to global $_ENV
 foreach ($config as $key => $value) {
   $_ENV[$key] = $value;
 }
 
+// load
+new PreLoader();
+new PluginLoader();
+
+// run
 new App();
diff --git a/src/App.php b/src/App.php
index 92ceb4a..15be58b 100644
--- a/src/App.php
+++ b/src/App.php
@@ -2,6 +2,10 @@
 
 namespace FlatFileForms;
 
+use FlatFileForms\Controllers\EntriesController;
+use FlatFileForms\Controllers\FieldsController;
+use FlatFileForms\Controllers\SubmissionController;
+use FlatFileForms\Controllers\ValidationController;
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpFoundation\Response;
 use Yosymfony\Toml\Toml;
@@ -33,104 +37,34 @@ class App
       // check api key
       $apiKey = $_GET['key'] ?? $_POST['key'] ?? null;
       if (empty($apiKey)) {
-        $response->setStatusCode(Response::HTTP_BAD_REQUEST);
-        throw new \Exception('API key missing');
+        throw new HttpException('API key missing', Response::HTTP_BAD_REQUEST);
       }
       if (! in_array($apiKey, $config['api']['keys'])) {
-        $response->setStatusCode(Response::HTTP_UNAUTHORIZED);
-        throw new \Exception('API key does not match');
+        throw new HttpException('API key does not match', Response::HTTP_UNAUTHORIZED);
       }
 
       // GET
       if ($method == 'GET')  {
         if (str_ends_with($path, '/fields')) {
-          $this->formPath = $formPath = $contentRoot . str_replace('/fields', '', $path);
+          $formPath = $contentRoot . str_replace('/fields', '', $path);
 
-          $fields = $this->buildFields($formPath, $_GET['page'] ?? null);
+          $builder = new Builder($formPath);
 
-          // flatten paged form
-          if ($this->isPagedFieldSet($fields) && isset($_GET['flat'])) {
-            $fields = array_merge(...array_values($fields));
-          }
+          $fieldsController = new FieldsController();
 
-          $content['data'] = $fields;
+          $content = $fieldsController->getFields($builder);
         }
 
         else if (str_ends_with($path, '/entries')) {
           if (! isset($_GET['dateFrom'])) {
-            $response->setStatusCode(Response::HTTP_BAD_REQUEST);
-            throw new \Exception('dateFrom parameter missing');
+            throw new HttpException('dateFrom parameter missing', Response::HTTP_BAD_REQUEST);
           }
 
-          $this->formPath = $formPath = $contentRoot . str_replace('/entries', '', $path);
-
-          $entries = [];
-
-          $dateFrom = new \DateTime($_GET['dateFrom']);
-          $dateTo = new \DateTime($_GET['dateTo'] ?? 'now');
-
-          $dateRangeYears = range($dateFrom->format('Y'), $dateTo->format('Y'));
-          $dateRangeYearsCount = count($dateRangeYears);
-          foreach ($dateRangeYears as $dateRangeYearIdx => $dateRangeYear) {
-            $yearPath = "$formPath/entries/$dateRangeYear";
-            if (! is_dir($yearPath)) {
-              continue;
-            }
-
-            if ($dateRangeYearsCount === 1) {
-              $dateRangeMonths = range($dateFrom->format('m'), $dateTo->format('m'));
-            }
-            else if ($dateRangeYearIdx === 0) {
-              $dateRangeMonths = range($dateFrom->format('m'), 12);
-            }
-            else if ($dateRangeYearIdx === $dateRangeYearsCount - 1) {
-              $dateRangeMonths = range(1, $dateTo->format('m'));
-            }
-            else {
-              $dateRangeMonths = range(1, 12);
-            }
-
-            $dateRangeMonthsCount = count($dateRangeMonths);
-            foreach ($dateRangeMonths as $dateRangeMonthIdx => $dateRangeMonth) {
-              $monthPath = "$yearPath/" . sprintf('%02d', $dateRangeMonth);
-              if (! is_dir($monthPath)) {
-                continue;
-              }
-
-              if ($dateRangeMonthsCount === 1) {
-                $dateRangeDays = range($dateFrom->format('d'), $dateTo->format('d'));
-              }
-              else if ($dateRangeYearIdx === 0 && $dateRangeMonthIdx === 0) {
-                $dateRangeDays = range($dateFrom->format('d'), 31);
-              }
-              else if ($dateRangeYearIdx === $dateRangeYearsCount - 1 && $dateRangeMonthIdx === $dateRangeMonthsCount - 1) {
-                $dateRangeDays = range(1, $dateTo->format('d'));
-              }
-              else {
-                $dateRangeDays = range(1, 31);
-              }
-
-              foreach ($dateRangeDays as $dateRangeDay) {
-                $dayPath = "$monthPath/" . sprintf('%02d', $dateRangeDay);
-                if (! is_dir($dayPath)) {
-                  continue;
-                }
-
-                $entriesForDay = $this->scandir($dayPath);
-                foreach ($entriesForDay as $entryForDay) {
-                  $entry = Toml::parseFile("$dayPath/$entryForDay");
-                  if (isset($_GET['flat'])) {
-                    $entries[] = $entry;
-                  } else {
-                    $entries[$dateRangeYear][$dateRangeMonth][$dateRangeDay][] = $entry;
-                  }
-                }
-              }
-
-            }
-          }
+          $formPath = $contentRoot . str_replace('/entries', '', $path);
+
+          $entriesController = new EntriesController();
 
-          $content['data'] = $entries;
+          $content = $entriesController->getEntries();
         }
 
         else {
@@ -141,46 +75,36 @@ class App
       // POST
       else if ($method == 'POST') {
         if (str_ends_with($path, '/validate')) {
-          $this->formPath = $formPath = $contentRoot . str_replace('/validate', '', $path);
+          $formPath = $contentRoot . str_replace('/validate', '', $path);
 
-          $fields = $this->buildFields($formPath, $_GET['page'] ?? null);
+          $builder = new Builder($formPath);
+          $validator = new Validator($formPath);
 
-          $content = $this->validateRequest($fields);
+          $validationController = new ValidationController();
+
+          $content = $validationController->validateRequest($builder, $validator);
         }
 
         else if (str_ends_with($path, '/submit')) {
-          $this->formPath = $formPath = $contentRoot . str_replace('/submit', '', $path);
-
-          $fields = $this->buildFields($formPath);
-
-          $content = $this->validateRequest($fields);
-
-          // if there were no validation errors then add entry
-          if (empty($content['error'])) {
-            $date = new \Datetime();
-            $entry = [
-              'fields' => $_POST,
-              'date' => $date->format('c'),
-            ];
-
-            $builder = new TomlBuilder();
-            $builder->addValue('date', $entry['date']);
-            $builder->addTable('fields');
-            foreach ($entry['fields'] as $entryKey => $entryValue) {
-              $builder->addValue($entryKey, $entryValue);
-            }
-
-            $entryDirectory = $formPath . '/entries/' . $date->format('Y/m/d');
-            @mkdir($entryDirectory, 0774, true);
-            $entryFilename = $date->format('Ymd_Hi_') . hash('adler32', serialize($entry)) . '.toml';
-            file_put_contents(
-              $entryDirectory . '/' . $entryFilename,
-              $builder->getTomlString()
-            );
+          $formPath = $contentRoot . str_replace('/submit', '', $path);
+
+          $builder = new Builder($formPath);
+          $validator = new Validator($formPath);
+
+          $submissionController = new SubmissionController();
+
+          $content = $submissionController->submit($builder, $validator, $formPath);
+
+          if (! empty($content['error'])) {
+            throw new HttpException($content['error'], Response::HTTP_UNPROCESSABLE_ENTITY);
           }
         }
       }
     } catch (\Exception $exception) {
+      if ($exception instanceof HttpException) {
+        $response->setStatusCode($exception->getCode());
+      }
+
       $content['error'] = basename(get_class($exception)) . ': ' . $exception->getMessage();
     }
 
@@ -190,178 +114,10 @@ class App
     $response->send();
   }
 
-  /**
-   * @param array $fields
-   */
-  public function validateRequest($fields) {
-    $content = [];
-    $hasInvalidFields = false;
-
-    $fields = $this->validateFields($fields);
-
-    if ($this->isPagedFieldSet($fields)) {
-      // remove surplus field values from response
-      $fields = array_map(function ($page) {
-        return array_map(function ($field) {
-          return array_intersect_key($field, array_flip([
-            'is_valid',
-          ]));
-        }, $page);
-      }, $fields);
-
-      $flattened = array_merge(...array_values($fields));
-      $hasInvalidFields = in_array(false, array_column($flattened, 'is_valid'));
-    } else {
-      // remove surplus field values from response
-      $fields = array_map(function ($field) {
-        return array_intersect_key($field, array_flip([
-          'is_valid',
-        ]));
-      }, $fields);
-
-      $hasInvalidFields = in_array(false, array_column($fields, 'is_valid'));
-    }
-
-    $content['data'] = $fields;
-
-    if ($hasInvalidFields) {
-      $content['error'] = 'Invalid fields';
-    }
-
-    return $content;
-  }
-
-  /**
-   * @param string $formPath
-   * @param mixed $page
-   */
-  public function buildFields($formPath, $page = null)
-  {
-    $parsed = Toml::parseFile($formPath . '/fields/_fields.toml');
-    $fields = [];
-
-    // if a page is requested
-    if ($page) {
-      if (! isset($parsed['page'])) {
-        throw new \Exception('Form has no pages');
-      }
-
-      if (! isset($parsed['page'][$page])) {
-        throw new \Exception('Form has no page ' . $page);
-      }
-
-      $fields = $this->buildSinglePageFields($parsed['page'][$page], $formPath);
-    }
-
-    // else get all fields
-    else {
-      // if form is paged
-      if (isset($parsed['page'])) {
-        $pages = $parsed['page'];
-        foreach ($pages as $pageKey => $pageFields) {
-          $fields[$pageKey] = $this->buildSinglePageFields($pageFields, $formPath);
-        }
-      }
-
-      // if form is not paged
-      else {
-        foreach ($parsed['field'] as $key => $field) {
-          $fields[$key] = $this->buildSingleField($formPath, $key, $field);
-        }
-      }
-    }
-
-    return $fields;
-  }
-
-  /**
-   * @param array $pageFields
-   * @param string $formPath
-   */
-  public function buildSinglePageFields($pageFields, $formPath)
-  {
-    $fields = [];
-
-    if (! empty($pageFields['file'])) {
-      $pageFields = array_replace_recursive($pageFields, Toml::parseFile($formPath . '/fields/' . $pageFields['file']));
-    }
-
-    foreach ($pageFields['field'] as $key => $field) {
-      $fields[$key] = $this->buildSingleField($formPath, $key, $field);
-    }
-
-    return $fields;
-  }
-
-  /**
-   * @param string $formPath
-   * @param string $key
-   * @param string $field
-   */
-  public function buildSingleField($formPath, $key, $field)
-  {
-    if (! empty($field['file'])) {
-      $field = array_replace_recursive($field, Toml::parseFile($formPath . '/fields/' . $field['file']));
-    }
-
-    if (empty($field['name'])) {
-      $field['name'] = $key;
-    }
-
-    return $field;
-  }
-
-  /**
-   * @param array $fields
-   */
-  public function validateFields($fields)
-  {
-    if ($this->isPagedFieldSet($fields)) {
-      foreach ($fields as $pageKey => &$pageFields) {
-        foreach ($pageFields as $key => &$field) {
-          $field = $this->validateSingleField($field);
-        }
-      }
-    } else {
-      foreach ($fields as $key => &$field) {
-        $field = $this->validateSingleField($field);
-      }
-    }
-
-    return $fields;
-  }
-
-  /**
-   * @param array $field
-   */
-  public function validateSingleField($field)
-  {
-    $value = $_POST[$field['name']] ?? '';
-    $field['is_valid'] = true;
-
-    if (isset($field['required']) && empty($value)) {
-      $field['is_valid'] = false;
-    }
-
-    if (isset($field['validation']['pattern']) && preg_match_all('/' . $field['validation']['pattern'] . '/', $value) === 0) {
-      $field['is_valid'] = false;
-    }
-
-    $validationFunctionName = 'validate_' . basename($this->formPath) . '_' . $field['name'];
-    if (function_exists($validationFunctionName)) {
-      $field = call_user_func($validationFunctionName, $field, $value);
-    }
-
-    return $field;
-  }
-
-  /**
-   * @param string $formPath
-   */
-  public function buildConfig($formPath)
+  public function buildConfig(string $requestPath): array
   {
     $config = [];
-    $currentDirectory = $formPath;
+    $currentDirectory = $requestPath;
     while (true) {
       $configFile = $currentDirectory . '/config/config.toml';
       if (file_exists($configFile)) {
@@ -387,34 +143,4 @@ class App
 
     return $config;
   }
-
-  /**
-   * @param array $fields
-   */
-  public function isPagedFieldSet($fields)
-  {
-    $firstItem = reset($fields);
-
-    return ! (isset($firstItem['name']) && ! is_array($firstItem['name']));
-  }
-
-  /**
-   * @param string|array $paths
-   */
-  public function scandir($paths)
-  {
-    $paths = (array)$paths;
-
-    $scanned = [];
-    foreach ($paths as $path) {
-      $filtered = array_values(
-        array_filter(
-          scandir($path), fn ($item) => ! in_array($item, ['.', '..'])
-        )
-      );
-      array_push($scanned, ...$filtered);
-    }
-
-    return $scanned;
-  }
 }
diff --git a/src/Builder.php b/src/Builder.php
new file mode 100644
index 0000000..308fa82
--- /dev/null
+++ b/src/Builder.php
@@ -0,0 +1,80 @@
+<?php
+
+namespace FlatFileForms;
+
+use Yosymfony\Toml\Toml;
+
+class Builder
+{
+  public function __construct(
+    private string $formPath
+  )
+  {}
+
+  public function buildFields(mixed $page = null)
+  {
+    $parsed = Toml::parseFile($this->formPath . '/fields/_fields.toml');
+    $fields = [];
+
+    // if a page is requested
+    if ($page) {
+      if (! isset($parsed['page'])) {
+        throw new \Exception('Form has no pages');
+      }
+
+      if (! isset($parsed['page'][$page])) {
+        throw new \Exception('Form has no page ' . $page);
+      }
+
+      $fields = $this->buildSinglePageFields($parsed['page'][$page]);
+    }
+
+    // else get all fields
+    else {
+      // if form is paged
+      if (isset($parsed['page'])) {
+        $pages = $parsed['page'];
+        foreach ($pages as $pageKey => $pageFields) {
+          $fields[$pageKey] = $this->buildSinglePageFields($pageFields);
+        }
+      }
+
+      // if form is not paged
+      else {
+        foreach ($parsed['field'] as $key => $field) {
+          $fields[$key] = $this->buildSingleField($key, $field);
+        }
+      }
+    }
+
+    return $fields;
+  }
+
+  public function buildSinglePageFields(array $pageFields): array
+  {
+    $fields = [];
+
+    if (! empty($pageFields['file'])) {
+      $pageFields = array_replace_recursive($pageFields, Toml::parseFile($this->formPath . '/fields/' . $pageFields['file']));
+    }
+
+    foreach ($pageFields['field'] as $key => $field) {
+      $fields[$key] = $this->buildSingleField($key, $field);
+    }
+
+    return $fields;
+  }
+
+  public function buildSingleField(string $key, array $field): array
+  {
+    if (! empty($field['file'])) {
+      $field = array_replace_recursive($field, Toml::parseFile($this->formPath . '/fields/' . $field['file']));
+    }
+
+    if (empty($field['name'])) {
+      $field['name'] = $key;
+    }
+
+    return $field;
+  }
+}
diff --git a/src/Controllers/EntriesController.php b/src/Controllers/EntriesController.php
new file mode 100644
index 0000000..13aa8e0
--- /dev/null
+++ b/src/Controllers/EntriesController.php
@@ -0,0 +1,84 @@
+<?php
+
+namespace FlatFileForms\Controllers;
+
+use Yosymfony\Toml\Toml;
+
+class EntriesController
+{
+  public function getEntries()
+  {
+    /**@var Utilities $utilities*/
+    global $utilities;
+
+    $entries = [];
+
+    $dateFrom = new \DateTime($_GET['dateFrom']);
+    $dateTo = new \DateTime($_GET['dateTo'] ?? 'now');
+
+    $dateRangeYears = range($dateFrom->format('Y'), $dateTo->format('Y'));
+    $dateRangeYearsCount = count($dateRangeYears);
+    foreach ($dateRangeYears as $dateRangeYearIdx => $dateRangeYear) {
+      $yearPath = "$formPath/entries/$dateRangeYear";
+      if (! is_dir($yearPath)) {
+        continue;
+      }
+
+      if ($dateRangeYearsCount === 1) {
+        $dateRangeMonths = range($dateFrom->format('m'), $dateTo->format('m'));
+      }
+      else if ($dateRangeYearIdx === 0) {
+        $dateRangeMonths = range($dateFrom->format('m'), 12);
+      }
+      else if ($dateRangeYearIdx === $dateRangeYearsCount - 1) {
+        $dateRangeMonths = range(1, $dateTo->format('m'));
+      }
+      else {
+        $dateRangeMonths = range(1, 12);
+      }
+
+      $dateRangeMonthsCount = count($dateRangeMonths);
+      foreach ($dateRangeMonths as $dateRangeMonthIdx => $dateRangeMonth) {
+        $monthPath = "$yearPath/" . sprintf('%02d', $dateRangeMonth);
+        if (! is_dir($monthPath)) {
+          continue;
+        }
+
+        if ($dateRangeMonthsCount === 1) {
+          $dateRangeDays = range($dateFrom->format('d'), $dateTo->format('d'));
+        }
+        else if ($dateRangeYearIdx === 0 && $dateRangeMonthIdx === 0) {
+          $dateRangeDays = range($dateFrom->format('d'), 31);
+        }
+        else if ($dateRangeYearIdx === $dateRangeYearsCount - 1 && $dateRangeMonthIdx === $dateRangeMonthsCount - 1) {
+          $dateRangeDays = range(1, $dateTo->format('d'));
+        }
+        else {
+          $dateRangeDays = range(1, 31);
+        }
+
+        foreach ($dateRangeDays as $dateRangeDay) {
+          $dayPath = "$monthPath/" . sprintf('%02d', $dateRangeDay);
+          if (! is_dir($dayPath)) {
+            continue;
+          }
+
+          $entriesForDay = $utilities->scandir($dayPath);
+          foreach ($entriesForDay as $entryForDay) {
+            $entry = Toml::parseFile("$dayPath/$entryForDay");
+            if (isset($_GET['flat'])) {
+              $entries[] = $entry;
+            } else {
+              $entries[$dateRangeYear][$dateRangeMonth][$dateRangeDay][] = $entry;
+            }
+          }
+        }
+
+      }
+    }
+
+    $content['data'] = $entries;
+
+    return $content;
+  }
+}
diff --git a/src/Controllers/FieldsController.php b/src/Controllers/FieldsController.php
new file mode 100644
index 0000000..c407604
--- /dev/null
+++ b/src/Controllers/FieldsController.php
@@ -0,0 +1,25 @@
+<?php
+
+namespace FlatFileForms\Controllers;
+
+use FlatFileForms\Builder;
+
+class FieldsController
+{
+  public function getFields(Builder $builder): array
+  {
+    /**@var Utilities $utilities*/
+    global $utilities;
+
+    $fields = $builder->buildFields($_GET['page'] ?? null);
+
+    // flatten paged form
+    if ($utilities->isPagedFieldSet($fields) && isset($_GET['flat'])) {
+      $fields = array_merge(...array_values($fields));
+    }
+
+    $content['data'] = $fields;
+
+    return $content;
+  }
+}
diff --git a/src/Controllers/SubmissionController.php b/src/Controllers/SubmissionController.php
new file mode 100644
index 0000000..f2c4c80
--- /dev/null
+++ b/src/Controllers/SubmissionController.php
@@ -0,0 +1,49 @@
+<?php
+
+namespace FlatFileForms\Controllers;
+
+use FlatFileForms\Builder;
+use FlatFileForms\Validator;
+use Yosymfony\Toml\TomlBuilder;
+
+class SubmissionController
+{
+  public function submit(Builder $builder, Validator $validator, $formPath)
+  {
+    $fields = $builder->buildFields();
+
+    // run through validation
+    $result = $validator->validateRequest($fields);
+
+    $content['data'] = $result['fields'];
+
+    // if there were no validation errors then add entry
+    if (empty($result['error'])) {
+      $date = new \Datetime();
+      $entry = [
+        'fields' => $_POST,
+        'date' => $date->format('c'),
+      ];
+
+      $entryBuilder = new TomlBuilder();
+      $entryBuilder->addValue('date', $entry['date']);
+      $entryBuilder->addTable('fields');
+      foreach ($entry['fields'] as $entryKey => $entryValue) {
+        $entryBuilder->addValue($entryKey, $entryValue);
+      }
+
+      $entryDirectory = $formPath . '/entries/' . $date->format('Y/m/d');
+      @mkdir($entryDirectory, 0774, true);
+      $entryFilename = $date->format('Ymd_Hi_') . hash('adler32', serialize($entry)) . '.toml';
+      file_put_contents(
+        $entryDirectory . '/' . $entryFilename,
+        $entryBuilder->getTomlString()
+      );
+    }
+    else {
+      $content['error'] = $result['error'];
+    }
+
+    return $content;
+  }
+}
diff --git a/src/Controllers/ValidationController.php b/src/Controllers/ValidationController.php
new file mode 100644
index 0000000..f90359a
--- /dev/null
+++ b/src/Controllers/ValidationController.php
@@ -0,0 +1,26 @@
+<?php
+
+namespace FlatFileForms\Controllers;
+
+use FlatFileForms\Builder;
+use FlatFileForms\Validator;
+
+class ValidationController
+{
+  public function validateRequest(Builder $builder, Validator $validator): array
+  {
+    /**@var Utilities $utilities*/
+    global $utilities;
+
+    $fields = $builder->buildFields($_GET['page'] ?? null);
+
+    $result = $validator->validateRequest($fields);
+
+    $content['data'] = $result['fields'];
+    if (! empty($result['error'])) {
+      $content['error'] = $result['error'];
+    }
+
+    return $content;
+  }
+}
diff --git a/src/HookManager.php b/src/HookManager.php
new file mode 100644
index 0000000..96ca8d3
--- /dev/null
+++ b/src/HookManager.php
@@ -0,0 +1,42 @@
+<?php
+
+namespace FlatFileForms;
+
+class HookManager
+{
+  private array $actions = [];
+  private array $filters = [];
+
+  public function addAction(string $name, callable $function, int $priority = 10): void
+  {
+    $this->action[$name][$priority][] = compact('name', 'function', 'priority');
+  }
+
+  public function addFilter(string $name, callable $function, int $priority = 10): void
+  {
+    $this->filters[$name][$priority][] = compact('name', 'callable', 'priority');
+  }
+
+  public function doAction(string $name, mixed ...$arguments): void
+  {
+    foreach ($this->actions[$name] as $actions) {
+      foreach ($actions as $action) {
+        call_user_func_array($action['function'], $arguments);
+      }
+    }
+  }
+
+  public function applyFilter(string $name, mixed $value, mixed ...$arguments): mixed
+  {
+    // set $value as first argument
+    array_unshift($arguments, $value);
+
+    foreach ($this->filters[$name] as $filters) {
+      foreach ($filters as $filter) {
+        $value = call_user_func_array($filter['function'], $arguments);
+      }
+    }
+
+    return $value;
+  }
+}
diff --git a/src/HttpException.php b/src/HttpException.php
new file mode 100644
index 0000000..85d2854
--- /dev/null
+++ b/src/HttpException.php
@@ -0,0 +1,6 @@
+<?php
+
+namespace FlatFileForms;
+
+class HttpException extends \Exception
+{}
diff --git a/src/PluginLoader.php b/src/PluginLoader.php
new file mode 100644
index 0000000..c8da5fd
--- /dev/null
+++ b/src/PluginLoader.php
@@ -0,0 +1,29 @@
+<?php
+
+namespace FlatFileForms;
+
+class PluginLoader
+{
+  public function __construct()
+  {
+    /**@var Utilities $utilities*/
+    global $utilities;
+
+    $pluginsDirectoryPath = $_ENV['app']['pluginsFolderPath'];
+
+    spl_autoload_register(function ($classname) use ($pluginsDirectoryPath) {
+      $classname = str_replace('FlatFileForms\\Plugins\\', '', $classname);
+
+      require_once
+        $pluginsDirectoryPath . '/' .
+        str_replace('\\', '/', $classname) .
+        '.php';
+    });
+
+    $pluginDirectories = $utilities->scandir($pluginsDirectoryPath);
+    foreach ($pluginDirectories as $directory) {
+      $pluginClass = 'FlatFileForms\\Plugins\\' . $directory . '\\Plugin';
+      $plugin = new $pluginClass();
+    }
+  }
+}
diff --git a/src/PreLoader.php b/src/PreLoader.php
new file mode 100644
index 0000000..57a0f52
--- /dev/null
+++ b/src/PreLoader.php
@@ -0,0 +1,15 @@
+<?php
+
+namespace FlatFileForms;
+
+class PreLoader
+{
+  public function __construct()
+  {
+    global $utilities;
+    $utilities = new Utilities();
+
+    global $hooks;
+    $hooks = new HookManager();
+  }
+}
diff --git a/src/Utilities.php b/src/Utilities.php
new file mode 100644
index 0000000..0462ad6
--- /dev/null
+++ b/src/Utilities.php
@@ -0,0 +1,40 @@
+<?php
+
+namespace FlatFileForms;
+
+class Utilities
+{
+  public function isPagedFieldSet(array $fields): bool
+  {
+    $firstItem = reset($fields);
+
+    return ! (isset($firstItem['name']) && ! is_array($firstItem['name']));
+  }
+
+  public function scandir(string $path): array
+  {
+    $path = rtrim($path, '/');
+
+    return array_values(
+      array_map(
+        fn ($item) => $path . '/' . $item,
+        array_filter(
+          scandir($path), fn ($item) => ! in_array($item, ['.', '..'])
+        )
+      )
+    );
+  }
+
+  public function scandirMultiple(string|array $paths): array
+  {
+    $paths = (array)$paths;
+
+    $merged = [];
+    foreach ($paths as $path) {
+      $scanned = $this->scandir($path);
+      array_push($merged, ...$scanned);
+    }
+
+    return $merged;
+  }
+}
diff --git a/src/Validator.php b/src/Validator.php
new file mode 100644
index 0000000..33cdf34
--- /dev/null
+++ b/src/Validator.php
@@ -0,0 +1,94 @@
+<?php
+
+namespace FlatFileForms;
+
+class Validator
+{
+  public function __construct(
+    private string $formPath
+  )
+  {}
+
+  public function validateRequest(array $fields): array
+  {
+    /**@var Utilities $utilities*/
+    global $utilities;
+
+    $result = [];
+    $hasInvalidFields = false;
+
+    $fields = $this->validateFields($fields);
+
+    if ($utilities->isPagedFieldSet($fields)) {
+      // remove surplus field values from response
+      $fields = array_map(function ($page) {
+        return array_map(function ($field) {
+          return array_intersect_key($field, array_flip([
+            'is_valid',
+          ]));
+        }, $page);
+      }, $fields);
+
+      $flattened = array_merge(...array_values($fields));
+      $hasInvalidFields = in_array(false, array_column($flattened, 'is_valid'));
+    } else {
+      // remove surplus field values from response
+      $fields = array_map(function ($field) {
+        return array_intersect_key($field, array_flip([
+          'is_valid',
+        ]));
+      }, $fields);
+
+      $hasInvalidFields = in_array(false, array_column($fields, 'is_valid'));
+    }
+
+    $result['fields'] = $fields;
+
+    if ($hasInvalidFields) {
+      $result['error'] = 'invalid fields';
+    }
+
+    return $result;
+  }
+
+  public function validateFields(array $fields): array
+  {
+    /**@var Utilities $utilities*/
+    global $utilities;
+
+    if ($utilities->isPagedFieldSet($fields)) {
+      foreach ($fields as $pageKey => &$pageFields) {
+        foreach ($pageFields as $key => &$field) {
+          $field = $this->validateSingleField($field);
+        }
+      }
+    } else {
+      foreach ($fields as $key => &$field) {
+        $field = $this->validateSingleField($field);
+      }
+    }
+
+    return $fields;
+  }
+
+  public function validateSingleField(array $field): array
+  {
+    $value = $_POST[$field['name']] ?? '';
+    $field['is_valid'] = true;
+
+    if (isset($field['required']) && empty($value)) {
+      $field['is_valid'] = false;
+    }
+
+    if (isset($field['validation']['pattern']) && preg_match_all('/' . $field['validation']['pattern'] . '/', $value) === 0) {
+      $field['is_valid'] = false;
+    }
+
+    $validationFunctionName = 'validate_' . basename($this->formPath) . '_' . $field['name'];
+    if (function_exists($validationFunctionName)) {
+      $field = call_user_func($validationFunctionName, $field, $value);
+    }
+
+    return $field;
+  }
+}