<?php

namespace Driver\SQL;

use Driver\SQL\Column\Column;
use Driver\SQL\Condition\Compare;
use Driver\SQL\Condition\CondBool;
use Driver\SQL\Condition\CondIn;
use Driver\SQL\Condition\Condition;
use Driver\SQL\Condition\CondKeyword;
use Driver\SQL\Condition\CondNot;
use Driver\Sql\Condition\CondNull;
use Driver\SQL\Condition\CondOr;
use Driver\SQL\Constraint\Constraint;
use \Driver\SQL\Constraint\Unique;
use \Driver\SQL\Constraint\PrimaryKey;
use \Driver\SQL\Constraint\ForeignKey;
use Driver\SQL\Query\CreateTable;
use Driver\SQL\Query\Delete;
use Driver\SQL\Query\Drop;
use Driver\SQL\Query\Insert;
use Driver\SQL\Query\Query;
use Driver\SQL\Query\Select;
use Driver\SQL\Query\Truncate;
use Driver\SQL\Query\Update;
use Driver\SQL\Strategy\CascadeStrategy;
use Driver\SQL\Strategy\SetDefaultStrategy;
use Driver\SQL\Strategy\SetNullStrategy;
use Driver\SQL\Strategy\Strategy;
use Objects\ConnectionData;

abstract class SQL {

  protected string $lastError;
  protected $connection;
  protected ConnectionData $connectionData;
  protected int $lastInsertId;

  public function __construct($connectionData) {
    $this->connection = NULL;
    $this->lastError = 'Unknown Error';
    $this->connectionData = $connectionData;
    $this->lastInsertId = 0;
  }

  public function isConnected() {
    return !is_null($this->connection);
  }

  public function getLastError() {
    return trim($this->lastError);
  }

  public function createTable($tableName) {
    return new CreateTable($this, $tableName);
  }

  public function insert($tableName, $columns=array()) {
    return new Insert($this, $tableName, $columns);
  }

  public function select(...$columNames) {
    return new Select($this, $columNames);
  }

  public function truncate($table) {
    return new Truncate($this, $table);
  }

  public function delete($table) {
    return new Delete($this, $table);
  }

  public function update($table) {
    return new Update($this, $table);
  }

  public function drop(string $table) {
    return new Drop($this, $table);
  }

  // ####################
  // ### ABSTRACT METHODS
  // ####################

  // Misc
  public abstract function checkRequirements();
  public abstract function getDriverName();

  // Connection Managment
  public abstract function connect();
  public abstract function disconnect();

  // Querybuilder
  protected function buildQuery(Query $query, array &$params) {
    if ($query instanceof Select) {
      $select = $query;
      $columns = $this->columnName($select->getColumns());
      $tables = $select->getTables();

      if (!$tables) {
        return $this->execute("SELECT $columns", $params, true);
      }

      $tables = $this->tableName($tables);
      $where = $this->getWhereClause($select->getConditions(), $params);

      $joinStr = "";
      $joins = $select->getJoins();
      if (!empty($joins)) {
        foreach($joins as $join) {
          $type = $join->getType();
          $joinTable = $this->tableName($join->getTable());
          $columnA = $this->columnName($join->getColumnA());
          $columnB = $this->columnName($join->getColumnB());
          $tableAlias = ($join->getTableAlias() ? " " . $join->getTableAlias() : "");

          $joinStr .= " $type JOIN $joinTable$tableAlias ON $columnA=$columnB";
        }
      }

      $groupBy = "";
      $groupColumns = $select->getGroupBy();
      if (!empty($groupColumns)) {
        $groupBy = " GROUP BY " . $this->columnName($groupColumns);
      }

      $orderBy = "";
      $orderColumns = $select->getOrderBy();
      if (!empty($orderColumns)) {
        $orderBy = " ORDER BY " . $this->columnName($orderColumns);
        $orderBy .= ($select->isOrderedAscending() ? " ASC" : " DESC");
      }

      $limit = ($select->getLimit() > 0 ? (" LIMIT " . $select->getLimit()) : "");
      $offset = ($select->getOffset() > 0 ? (" OFFSET " . $select->getOffset()) : "");
      return "SELECT $columns FROM $tables$joinStr$where$groupBy$orderBy$limit$offset";
    } else {
      $this->lastError = "buildQuery() not implemented for type: " . get_class($query);
      return FALSE;
    }
  }

  public function executeCreateTable(CreateTable $createTable) {
    $tableName = $this->tableName($createTable->getTableName());
    $ifNotExists = $createTable->ifNotExists() ? " IF NOT EXISTS": "";

    $entries = array();
    foreach($createTable->getColumns() as $column) {
      $entries[] = ($tmp = $this->getColumnDefinition($column));
      if (is_null($tmp)) {
        return false;
      }
    }

    foreach($createTable->getConstraints() as $constraint) {
      $entries[] = ($tmp = $this->getConstraintDefinition($constraint));
      if (is_null($tmp)) {
        return false;
      }
    }

    $entries = implode(",", $entries);
    $query = "CREATE TABLE$ifNotExists $tableName ($entries)";
    return $this->execute($query);
  }

  public function executeInsert(Insert $insert) {

    $tableName = $this->tableName($insert->getTableName());
    $columns = $insert->getColumns();
    $rows = $insert->getRows();

    if (empty($rows)) {
      $this->lastError = "No rows to insert given.";
      return false;
    }

    if (is_null($columns) || empty($columns)) {
      $columnStr = "";
    } else {
      $columnStr = " (" . $this->columnName($columns) . ")";
    }

    $parameters = array();
    $values = array();
    foreach($rows as $row) {
      $rowPlaceHolder = array();
      foreach($row as $val) {
        $rowPlaceHolder[] = $this->addValue($val, $parameters);
      }

      $values[] = "(" . implode(",", $rowPlaceHolder) . ")";
    }

    $values = implode(",", $values);

    $onDuplicateKey = $this->getOnDuplicateStrategy($insert->onDuplicateKey(), $parameters);
    if ($onDuplicateKey === FALSE) {
      return false;
    }

    $returningCol = $insert->getReturning();
    $returning = $this->getReturning($returningCol);

    $query = "INSERT INTO $tableName$columnStr VALUES $values$onDuplicateKey$returning";
    if($insert->dump) { var_dump($query); var_dump($parameters); }
    $res = $this->execute($query, $parameters, !empty($returning));
    $success = ($res !== FALSE);

    if($success && $returningCol) {
      $this->fetchReturning($res, $returningCol);
    }

    return $success;
  }

  public function executeSelect(Select $select) {
    $params = array();
    $query = $this->buildQuery($select, $params);
    if($select->dump) { var_dump($query); var_dump($params); }
    return $this->execute($query, $params, true);
  }

  public function executeDelete(Delete $delete) {

    $params = array();
    $table = $this->tableName($delete->getTable());
    $where = $this->getWhereClause($delete->getConditions(), $params);

    $query = "DELETE FROM $table$where";
    if($delete->dump) { var_dump($query); }
    return $this->execute($query, $params);
  }

  public function executeTruncate(Truncate $truncate) {
    $query = "TRUNCATE " . $this->tableName($truncate->getTable());
    if ($truncate->dump) { var_dump($query); }
    return $this->execute($query);
  }

  public function executeUpdate(Update $update) {

    $params = array();
    $table = $this->tableName($update->getTable());

    $valueStr = array();
    foreach($update->getValues() as $key => $val) {
      $valueStr[] =  $this->columnName($key) . "=" . $this->addValue($val, $params);
    }
    $valueStr = implode(",", $valueStr);

    $where = $this->getWhereClause($update->getConditions(), $params);
    $query = "UPDATE $table SET $valueStr$where";
    if($update->dump) { var_dump($query); var_dump($params); }
    return $this->execute($query, $params);
  }

  public function executeDrop(Drop $drop) {
    $query = "DROP TABLE " . $this->tableName($drop->getTable());
    if ($drop->dump) { var_dump($query); }
    return $this->execute($query);
  }

  protected function getWhereClause($conditions, &$params) {
    if (!$conditions) {
      return "";
    } else {
      return " WHERE " . $this->buildCondition($conditions, $params);
    }
  }

  public function getConstraintDefinition(Constraint $constraint) {
    $columnName = $this->columnName($constraint->getColumnNames());
    if ($constraint instanceof PrimaryKey) {
      return "PRIMARY KEY ($columnName)";
    } else if ($constraint instanceof Unique) {
      return "UNIQUE ($columnName)";
    } else if ($constraint instanceof ForeignKey) {
      $refTable = $this->tableName($constraint->getReferencedTable());
      $refColumn = $this->columnName($constraint->getReferencedColumn());
      $strategy = $constraint->onDelete();
      $code = "FOREIGN KEY ($columnName) REFERENCES $refTable ($refColumn)";
      if ($strategy instanceof SetDefaultStrategy) {
        $code .= " ON DELETE SET DEFAULT";
      } else if($strategy instanceof SetNullStrategy) {
        $code .= " ON DELETE SET NULL";
      } else if($strategy instanceof CascadeStrategy) {
        $code .= " ON DELETE CASCADE";
      }

      return $code;
    } else {
      $this->lastError = "Unsupported constraint type: " . get_class($constraint);
      return false;
    }
  }

  protected function getReturning(?string $columns) {
    return "";
  }

  protected abstract function getColumnDefinition(Column $column);
  protected abstract function fetchReturning($res, string $returningCol);
  protected abstract function getOnDuplicateStrategy(?Strategy $strategy, &$params);

  protected abstract function getValueDefinition($val);
  protected abstract function addValue($val, &$params);

  protected abstract function tableName($table);
  protected abstract function columnName($col);

  // Special Keywords and functions
  public function now() { return $this->currentTimestamp(); }
  public abstract function currentTimestamp();

  public function count($col = NULL) {
    if (is_null($col)) {
      return new Keyword("COUNT(*) AS count");
    } else if($col instanceof Keyword) {
      return new Keyword("COUNT(" . $col->getValue() . ") AS count");
    } else {
      $countCol = strtolower(str_replace(".","_", $col)) .  "_count";
      $col = $this->columnName($col);
      return new Keyword("COUNT($col) AS $countCol");
    }
  }

  public function sum($col) {
    $sumCol = strtolower(str_replace(".","_", $col)) .  "_sum";
    $col = $this->columnName($col);
    return new Keyword("SUM($col) AS $sumCol");
  }

  public function distinct($col) {
    $col = $this->columnName($col);
    return new Keyword("DISTINCT($col)");
  }

  // Statements
  protected abstract function execute($query, $values=NULL, $returnValues=false);

  protected function buildCondition($condition, &$params) {

    if ($condition instanceof CondOr) {
      $conditions = array();
      foreach($condition->getConditions() as $cond) {
        $conditions[] = $this->buildCondition($cond, $params);
      }
      return "(" . implode(" OR ", $conditions) . ")";
    } else if ($condition instanceof Compare) {
      $column = $this->columnName($condition->getColumn());
      $value = $condition->getValue();
      $operator = $condition->getOperator();

      if ($value === null) {
        if ($operator === "=") {
          return "$column IS NULL";
        } else if ($operator === "!=") {
          return "$column IS NOT NULL";
        }
      }

      return $column . $operator . $this->addValue($value, $params);
    } else if ($condition instanceof CondBool) {
      return $this->columnName($condition->getValue());
    } else if (is_array($condition)) {
      if (count($condition) === 1) {
        return $this->buildCondition($condition[0], $params);
      } else {
        $conditions = array();
        foreach ($condition as $cond) {
          $conditions[] = $this->buildCondition($cond, $params);
        }
        return implode(" AND ", $conditions);
      }
    } else if($condition instanceof CondIn) {

      $expression = $condition->getExpression();
      if (is_array($expression)) {
        $values = array();
        foreach ($expression as $value) {
          $values[] = $this->addValue($value, $params);
        }

        $values = implode(",", $values);
      } else if($expression instanceof Select) {
        $values = $this->buildQuery($expression, $params);
      } else {
        $this->lastError = "Unsupported in-expression value: " . get_class($condition);
        return false;
      }

      return $this->columnName($condition->getColumn()) . " IN ($values)";
    } else if($condition instanceof CondKeyword) {
      $left = $condition->getLeftExp();
      $right = $condition->getRightExp();
      $keyword = $condition->getKeyword();
      $left = ($left instanceof Column) ? $this->columnName($left->getName()) : $this->addValue($left, $params);
      $right = ($right instanceof Column) ? $this->columnName($right->getName()) : $this->addValue($right, $params);
      return "$left $keyword $right ";
    } else if($condition instanceof CondNot) {
      $expression = $condition->getExpression();
      if ($expression instanceof Condition) {
        $expression = $this->buildCondition($expression, $params);
      } else {
        $expression = $this->columnName($expression);
      }

      return "NOT $expression";
    } else if($condition instanceof CondNull) {
      return $this->columnName($condition->getColumn()) . " IS NULL";
    } else {
      $this->lastError = "Unsupported condition type: " . get_class($condition);
      return false;
    }
  }

  public function setLastError($str) {
    $this->lastError = $str;
  }

  public function getLastInsertId() {
    return $this->lastInsertId;
  }

  public function close() {
    $this->disconnect();
    $this->connection = NULL;
  }

  public static function createConnection(ConnectionData $connectionData) {
    $type = $connectionData->getProperty("type");
    if ($type === "mysql") {
      $sql = new MySQL($connectionData);
    } else if ($type === "postgres") {
      $sql = new PostgreSQL($connectionData);
    /*} else if ($type === "oracle") {
      // $sql = new OracleSQL($connectionData);
    */
    } else {
      return "Unknown database type";
    }

    if ($sql->checkRequirements()) {
      $sql->connect();
    }

    return $sql;
  }

  public abstract function getStatus();

  public function parseBool($val) : bool {
    return in_array($val, array(true, 1, '1', 't', 'true', 'TRUE'), true);
  }
}