<?php
/**
 * @link http://www.yiiframework.com/
 * @copyright Copyright (c) 2008 Yii Software LLC
 * @license http://www.yiiframework.com/license/
 */

namespace yii\redis;

use yii\base\NotSupportedException;
use yii\db\Exception;
use yii\db\Expression;

/**
 * LuaScriptBuilder builds lua scripts used for retrieving data from redis.
 *
 * @author Carsten Brandt <mail@cebe.cc>
 * @since 2.0
 */
class LuaScriptBuilder extends \yii\base\Object
{
	/**
	 * Builds a Lua script for finding a list of records
	 * @param ActiveQuery $query the query used to build the script
	 * @return string
	 */
	public function buildAll($query)
	{
		// TODO add support for orderBy
		/** @var ActiveRecord $modelClass */
		$modelClass = $query->modelClass;
		$key = $this->quoteValue($modelClass::keyPrefix() . ':a:');
		return $this->build($query, "n=n+1 pks[n]=redis.call('HGETALL',$key .. pk)", 'pks');
	}

	/**
	 * Builds a Lua script for finding one record
	 * @param ActiveQuery $query the query used to build the script
	 * @return string
	 */
	public function buildOne($query)
	{
		// TODO add support for orderBy
		/** @var ActiveRecord $modelClass */
		$modelClass = $query->modelClass;
		$key = $this->quoteValue($modelClass::keyPrefix() . ':a:');
		return $this->build($query, "do return redis.call('HGETALL',$key .. pk) end", 'pks');
	}

	/**
	 * Builds a Lua script for finding a column
	 * @param ActiveQuery $query the query used to build the script
	 * @param string $column name of the column
	 * @return string
	 */
	public function buildColumn($query, $column)
	{
		// TODO add support for orderBy and indexBy
		/** @var ActiveRecord $modelClass */
		$modelClass = $query->modelClass;
		$key = $this->quoteValue($modelClass::keyPrefix() . ':a:');
		return $this->build($query, "n=n+1 pks[n]=redis.call('HGET',$key .. pk," . $this->quoteValue($column) . ")", 'pks');
	}

	/**
	 * Builds a Lua script for getting count of records
	 * @param ActiveQuery $query the query used to build the script
	 * @return string
	 */
	public function buildCount($query)
	{
		return $this->build($query, 'n=n+1', 'n');
	}

	/**
	 * Builds a Lua script for finding the sum of a column
	 * @param ActiveQuery $query the query used to build the script
	 * @param string $column name of the column
	 * @return string
	 */
	public function buildSum($query, $column)
	{
		/** @var ActiveRecord $modelClass */
		$modelClass = $query->modelClass;
		$key = $this->quoteValue($modelClass::keyPrefix() . ':a:');
		return $this->build($query, "n=n+redis.call('HGET',$key .. pk," . $this->quoteValue($column) . ")", 'n');
	}

	/**
	 * Builds a Lua script for finding the average of a column
	 * @param ActiveQuery $query the query used to build the script
	 * @param string $column name of the column
	 * @return string
	 */
	public function buildAverage($query, $column)
	{
		/** @var ActiveRecord $modelClass */
		$modelClass = $query->modelClass;
		$key = $this->quoteValue($modelClass::keyPrefix() . ':a:');
		return $this->build($query, "n=n+1 if v==nil then v=0 end v=v+redis.call('HGET',$key .. pk," . $this->quoteValue($column) . ")", 'v/n');
	}

	/**
	 * Builds a Lua script for finding the min value of a column
	 * @param ActiveQuery $query the query used to build the script
	 * @param string $column name of the column
	 * @return string
	 */
	public function buildMin($query, $column)
	{
		/** @var ActiveRecord $modelClass */
		$modelClass = $query->modelClass;
		$key = $this->quoteValue($modelClass::keyPrefix() . ':a:');
		return $this->build($query, "n=redis.call('HGET',$key .. pk," . $this->quoteValue($column) . ") if v==nil or n<v then v=n end", 'v');
	}

	/**
	 * Builds a Lua script for finding the max value of a column
	 * @param ActiveQuery $query the query used to build the script
	 * @param string $column name of the column
	 * @return string
	 */
	public function buildMax($query, $column)
	{
		/** @var ActiveRecord $modelClass */
		$modelClass = $query->modelClass;
		$key = $this->quoteValue($modelClass::keyPrefix() . ':a:');
		return $this->build($query, "n=redis.call('HGET',$key .. pk," . $this->quoteValue($column) . ") if v==nil or n>v then v=n end", 'v');
	}

	/**
	 * @param ActiveQuery $query the query used to build the script
	 * @param string $buildResult the lua script for building the result
	 * @param string $return the lua variable that should be returned
	 * @return string
	 */
	private function build($query, $buildResult, $return)
	{
		if (!empty($query->orderBy)) {
			throw new NotSupportedException('orderBy is currently not supported by redis ActiveRecord.');
		}

		$columns = [];
		if ($query->where !== null) {
			$condition = $this->buildCondition($query->where, $columns);
		} else {
			$condition = 'true';
		}

		$start = $query->offset === null ? 0 : $query->offset;
		$limitCondition = 'i>' . $start . ($query->limit === null ? '' : ' and i<=' . ($start + $query->limit));

		/** @var ActiveRecord $modelClass */
		$modelClass = $query->modelClass;
		$key = $this->quoteValue($modelClass::keyPrefix());
		$loadColumnValues = '';
		foreach($columns as $column => $alias) {
			$loadColumnValues .= "local $alias=redis.call('HGET',$key .. ':a:' .. pk, '$column')\n";
		}

		return <<<EOF
local allpks=redis.call('LRANGE',$key,0,-1)
local pks={}
local n=0
local v=nil
local i=0
for k,pk in ipairs(allpks) do
    $loadColumnValues
    if $condition then
      i=i+1
      if $limitCondition then
        $buildResult
      end
    end
end
return $return
EOF;
	}

	/**
	 * Adds a column to the list of columns to retrieve and creates an alias
	 * @param string $column the column name to add
	 * @param array $columns list of columns given by reference
	 * @return string the alias generated for the column name
	 */
	private function addColumn($column, &$columns)
	{
		if (isset($columns[$column])) {
			return $columns[$column];
		}
		$name = 'c' . preg_replace("/[^A-z]+/", "", $column) . count($columns);
		return $columns[$column] = $name;
	}

	/**
	 * Quotes a string value for use in a query.
	 * Note that if the parameter is not a string or int, it will be returned without change.
	 * @param string $str string to be quoted
	 * @return string the properly quoted string
	 */
	private function quoteValue($str)
	{
		if (!is_string($str) && !is_int($str)) {
			return $str;
		}

		return "'" . addcslashes(str_replace("'", "\\'", $str), "\000\n\r\\\032") . "'";
	}

	/**
	 * Parses the condition specification and generates the corresponding Lua expression.
	 * @param string|array $condition the condition specification. Please refer to [[ActiveQuery::where()]]
	 * on how to specify a condition.
	 * @param array $columns the list of columns and aliases to be used
	 * @return string the generated SQL expression
	 * @throws \yii\db\Exception if the condition is in bad format
	 * @throws \yii\base\NotSupportedException if the condition is not an array
	 */
	public function buildCondition($condition, &$columns)
	{
		static $builders = [
			'and' => 'buildAndCondition',
			'or' => 'buildAndCondition',
			'between' => 'buildBetweenCondition',
			'not between' => 'buildBetweenCondition',
			'in' => 'buildInCondition',
			'not in' => 'buildInCondition',
			'like' => 'buildLikeCondition',
			'not like' => 'buildLikeCondition',
			'or like' => 'buildLikeCondition',
			'or not like' => 'buildLikeCondition',
		];

		if (!is_array($condition)) {
			throw new NotSupportedException('Where condition must be an array in redis ActiveRecord.');
		}
		if (isset($condition[0])) { // operator format: operator, operand 1, operand 2, ...
			$operator = strtolower($condition[0]);
			if (isset($builders[$operator])) {
				$method = $builders[$operator];
				array_shift($condition);
				return $this->$method($operator, $condition, $columns);
			} else {
				throw new Exception('Found unknown operator in query: ' . $operator);
			}
		} else { // hash format: 'column1' => 'value1', 'column2' => 'value2', ...
			return $this->buildHashCondition($condition, $columns);
		}
	}

	private function buildHashCondition($condition, &$columns)
	{
		$parts = [];
		foreach ($condition as $column => $value) {
			if (is_array($value)) { // IN condition
				$parts[] = $this->buildInCondition('in', [$column, $value], $columns);
			} else {
				$column = $this->addColumn($column, $columns);
				if ($value === null) {
					$parts[] = "$column==nil";
				} elseif ($value instanceof Expression) {
					$parts[] = "$column==" . $value->expression;
				} else {
					$value = $this->quoteValue($value);
					$parts[] = "$column==$value";
				}
			}
		}
		return count($parts) === 1 ? $parts[0] : '(' . implode(') and (', $parts) . ')';
	}

	private function buildAndCondition($operator, $operands, &$columns)
	{
		$parts = [];
		foreach ($operands as $operand) {
			if (is_array($operand)) {
				$operand = $this->buildCondition($operand, $columns);
			}
			if ($operand !== '') {
				$parts[] = $operand;
			}
		}
		if (!empty($parts)) {
			return '(' . implode(") $operator (", $parts) . ')';
		} else {
			return '';
		}
	}

	private function buildBetweenCondition($operator, $operands, &$columns)
	{
		if (!isset($operands[0], $operands[1], $operands[2])) {
			throw new Exception("Operator '$operator' requires three operands.");
		}

		list($column, $value1, $value2) = $operands;

		$value1 = $this->quoteValue($value1);
		$value2 = $this->quoteValue($value2);
		$column = $this->addColumn($column, $columns);
		return "$column >= $value1 and $column <= $value2";
	}

	private function buildInCondition($operator, $operands, &$columns)
	{
		if (!isset($operands[0], $operands[1])) {
			throw new Exception("Operator '$operator' requires two operands.");
		}

		list($column, $values) = $operands;

		$values = (array)$values;

		if (empty($values) || $column === []) {
			return $operator === 'in' ? 'false' : 'true';
		}

		if (count($column) > 1) {
			return $this->buildCompositeInCondition($operator, $column, $values, $columns);
		} elseif (is_array($column)) {
			$column = reset($column);
		}
		$columnAlias = $this->addColumn($column, $columns);
		$parts = [];
		foreach ($values as $i => $value) {
			if (is_array($value)) {
				$value = isset($value[$column]) ? $value[$column] : null;
			}
			if ($value === null) {
				$parts[] = "$columnAlias==nil";
			} elseif ($value instanceof Expression) {
				$parts[] = "$columnAlias==" . $value->expression;
			} else {
				$value = $this->quoteValue($value);
				$parts[] = "$columnAlias==$value";
			}
		}
		$operator = $operator === 'in' ? '' : 'not ';
		return "$operator(" . implode(' or ', $parts) . ')';
	}

	protected function buildCompositeInCondition($operator, $inColumns, $values, &$columns)
	{
		$vss = [];
		foreach ($values as $value) {
			$vs = [];
			foreach ($inColumns as $column) {
				$column = $this->addColumn($column, $columns);
				if (isset($value[$column])) {
					$vs[] = "$column==" . $this->quoteValue($value[$column]);
				} else {
					$vs[] = "$column==nil";
				}
			}
			$vss[] = '(' . implode(' and ', $vs) . ')';
		}
		$operator = $operator === 'in' ? '' : 'not ';
		return "$operator(" . implode(' or ', $vss) . ')';
	}

	private function buildLikeCondition($operator, $operands, &$columns)
	{
		throw new NotSupportedException('LIKE conditions are not suppoerted by redis ActiveRecord.');
	}
}