<?php

namespace Objects\DatabaseEntity;

use Driver\Logger\Logger;
use Driver\SQL\Column\BoolColumn;
use Driver\SQL\Column\DateTimeColumn;
use Driver\SQL\Column\IntColumn;
use Driver\SQL\Column\StringColumn;
use Driver\SQL\Condition\Compare;
use Driver\SQL\Condition\Condition;
use Driver\SQL\Column\DoubleColumn;
use Driver\SQL\Column\FloatColumn;
use Driver\SQL\Constraint\ForeignKey;
use Driver\SQL\Query\CreateTable;
use Driver\SQL\SQL;
use Driver\SQL\Strategy\CascadeStrategy;
use Driver\SQL\Strategy\SetNullStrategy;
use PHPUnit\Util\Exception;

class DatabaseEntityHandler {

  private \ReflectionClass $entityClass;
  private static \ReflectionProperty $ID_FIELD;
  private string $tableName;
  private array $columns;
  private array $properties;
  private array $relations;
  private SQL $sql;
  private Logger $logger;

  public function __construct(SQL $sql, \ReflectionClass $entityClass) {
    $this->sql = $sql;
    $className = $entityClass->getName();
    $this->logger = new Logger($entityClass->getShortName(), $sql);
    $this->entityClass = $entityClass;
    if (!$this->entityClass->isSubclassOf(DatabaseEntity::class) ||
      !$this->entityClass->isInstantiable()) {
      $this->raiseError("Cannot persist class '$className': Not an instance of DatabaseEntity or not instantiable.");
    }

    $this->tableName = $this->entityClass->getShortName();
    $this->columns = [];
    $this->properties = [];
    $this->relations = [];

    if (!isset(self::$ID_FIELD)) {
      self::$ID_FIELD = (new \ReflectionClass(DatabaseEntity::class))->getProperty("id");
    }

    foreach ($this->entityClass->getProperties() as $property) {
      $propertyName = $property->getName();
      $propertyType = $property->getType();
      $columnName = self::getColumnName($propertyName);
      if (!($propertyType instanceof \ReflectionNamedType)) {
        $this->raiseError("Cannot persist class '$className': Property '$propertyName' has no valid type");
      }

      $nullable = $propertyType->allowsNull();
      $propertyTypeName = $propertyType->getName();
      if ($propertyTypeName === 'string') {
        $this->columns[$propertyName] = new StringColumn($columnName, null, $nullable);
      } else if ($propertyTypeName === 'int') {
        $this->columns[$propertyName] = new IntColumn($columnName, $nullable);
      } else if ($propertyTypeName === 'float') {
        $this->columns[$propertyName] = new FloatColumn($columnName, $nullable);
      } else if ($propertyTypeName === 'double') {
        $this->columns[$propertyName] = new DoubleColumn($columnName, $nullable);
      } else if ($propertyTypeName === 'bool') {
        $this->columns[$propertyName] = new BoolColumn($columnName, $nullable);
      } else if ($propertyTypeName === 'DateTime') {
        $this->columns[$propertyName] = new DateTimeColumn($columnName, $nullable);
      } else {
        try {
          $requestedClass = new \ReflectionClass($propertyTypeName);
          if ($requestedClass->isSubclassOf(DatabaseEntity::class)) {
            $requestedHandler = ($requestedClass->getName() === $this->entityClass->getName()) ?
              $this : DatabaseEntity::getHandler($this->sql, $requestedClass);
            $strategy = $nullable ? new SetNullStrategy() : new CascadeStrategy();
            $this->columns[$propertyName] = new IntColumn($columnName, $nullable);
            $this->relations[$propertyName] = new ForeignKey($columnName, $requestedHandler->tableName, "id", $strategy);
          }
        } catch (\Exception $ex) {
          $this->raiseError("Cannot persist class '$className': Property '$propertyName' has non persist-able type: $propertyTypeName");
        }
      }

      $this->properties[$propertyName] = $property;
    }
  }

  private static function getColumnName(string $propertyName): string {
    // abcTestLOL => abc_test_lol
    return strtolower(preg_replace_callback("/([a-z])([A-Z]+)/", function ($m) {
      return $m[1] . "_" . strtolower($m[2]);
    }, $propertyName));
  }

  public function getReflection(): \ReflectionClass {
    return $this->entityClass;
  }

  public function getLogger(): Logger {
    return $this->logger;
  }

  public function getTableName(): string {
    return $this->tableName;
  }

  private function entityFromRow(array $row): DatabaseEntity {
    try {
      $entity = $this->entityClass->newInstanceWithoutConstructor();
      foreach ($this->columns as $propertyName => $column) {
        $value = $row[$column->getName()];
        $property = $this->properties[$propertyName];

        if ($property->getType()->getName() === "DateTime") {
          $value = new \DateTime($value);
        }

        $property->setValue($entity, $value);
      }

      self::$ID_FIELD->setAccessible(true);
      self::$ID_FIELD->setValue($entity, $row["id"]);
      return $entity;
    } catch (\Exception $exception) {
      $this->logger->error("Error creating entity from database row: " . $exception->getMessage());
      throw $exception;
    }
  }

  public function fetchOne(int $id): ?DatabaseEntity {
    $res = $this->sql->select("id", ...array_keys($this->columns))
      ->from($this->tableName)
      ->where(new Compare("id", $id))
      ->first()
      ->execute();

    if (empty($res)) {
      return null;
    } else {
      return $this->entityFromRow($res);
    }
  }

  public function fetchMultiple(?Condition $condition = null): ?array {
    $query = $this->sql->select("id", ...array_keys($this->columns))
      ->from($this->tableName);

    if ($condition) {
      $query->where($condition);
    }

    $res = $query->execute();
    if ($res === false) {
      return null;
    } else {
      $entities = [];
      foreach ($res as $row) {
        $entities[] = $this->entityFromRow($row);
      }
      return $entities;
    }
  }

  public function getTableQuery(): CreateTable {
    $query = $this->sql->createTable($this->tableName)
      ->onlyIfNotExists()
      ->addSerial("id")
      ->primaryKey("id");

    foreach ($this->columns as $column) {
      $query->addColumn($column);
    }

    foreach ($this->relations as $constraint) {
      $query->addConstraint($constraint);
    }

    return $query;
  }

  public function createTable(): bool {
    $query = $this->getTableQuery();
    return $query->execute();
  }

  public function insertOrUpdate(DatabaseEntity $entity) {
    $id = $entity->getId();
    if ($id === null) {
      $columns = [];
      $row = [];

      foreach ($this->columns as $propertyName => $column) {
        $columns[] = $column->getName();
        $property = $this->properties[$propertyName];
        if ($property->isInitialized($entity)) {
          $value = $property->getValue($entity);
        } else if (!$this->columns[$propertyName]->notNull()) {
          $value = null;
        } else {
          $this->logger->error("Cannot insert entity: property '$propertyName' was not initialized yet.");
          return false;
        }

        $row[] = $value;
      }

      $res = $this->sql->insert($this->tableName, $columns)
        ->addRow(...$row)
        ->returning("id")
        ->execute();

      if ($res !== false) {
        return $this->sql->getLastInsertId();
      } else {
        return false;
      }
    } else {
      $query = $this->sql->update($this->tableName)
        ->where(new Compare("id", $id));

      foreach ($this->columns as $propertyName => $column) {
        $columnName = $column->getName();
        $property = $this->properties[$propertyName];
        if ($property->isInitialized($entity)) {
          $value = $property->getValue($entity);
        } else if (!$this->columns[$propertyName]->notNull()) {
          $value = null;
        } else {
          $this->logger->error("Cannot update entity: property '$propertyName' was not initialized yet.");
          return false;
        }

        $query->set($columnName, $value);
      }

      return $query->execute();
    }
  }

  public function delete(int $id) {
    return $this->sql->delete($this->tableName)->where(new Compare("id", $id))->execute();
  }

  private function raiseError(string $message) {
    $this->logger->error($message);
    throw new Exception($message);
  }

  private function getPropertyValue() {

  }
}