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QueryGenerator.php
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QueryGenerator.php
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<?php
/**
* A simple query generator for conditionally building MySQL statements.
*
* Build clauses by calling their corresponding member functions.
*
* Each method takes two arguments:
* 1. An array of strings that will later be combined to form the clause.
* 2. An array of paramters for use in prepared statements.
*
* Available clauses / methods are:
* select, insert, replace, update, delete, from, join, set, columns, values,
* where, group, having, order, limit, offset, duplicate, modify
*
* After all clauses have been built, call the 'build' member function to
* compose the entire query. This returns an array containing the query and
* an array parameters.
*
* Example usage:
* $qGen = new QueryGenerator();
* $qGen->select(['field1', 'field2']);
* $qGen->from(['table1']);
* $qGen->join(['INNER JOIN table2 ON asdf = ?'], 'asdf');
* $qGen->where(['condition1 < ?', 'condition2 > ?'], [5, 7]);
* list($query, $params) = $qGen->build();
*
* Generated query:
* SELECT field1, field2
* FROM table1
* INNER JOIN table2 ON asdf = ?
* WHERE (condition1 < ?) AND (condition2 > ?)
*
* Generated parameters:
* ['asdf', 5, 7]
*/
class QueryGenerator {
/**
* The keys of this array are the set of clauses that can compose different
* statements. These correspond to methods that can be called on this class.
* The values are the syntax rules for collapsing the corresponding clauses.
*
* @var non-empty-array<string, array{
* clause: string,
* prefix: string,
* glue: string|false,
* suffix: string,
* requiresArgument?: bool
* }>
*/
private static array $methods = [
'select' => [
'clause' => 'SELECT <<MODIFIERS>> ',
'prefix' => '',
'glue' => ', ',
'suffix' => '',
'requiresArgument' => true,
],
'insert' => [
'clause' => 'INSERT <<MODIFIERS>> INTO ',
'prefix' => '',
'glue' => ', ',
'suffix' => '',
],
'replace' => [
'clause' => 'REPLACE <<MODIFIERS>> INTO ',
'prefix' => '',
'glue' => ', ',
'suffix' => '',
],
'update' => [
'clause' => 'UPDATE <<MODIFIERS>> ',
'prefix' => '',
'glue' => ', ',
'suffix' => '',
],
'delete' => [
'clause' => 'DELETE <<MODIFIERS>> ',
'prefix' => '',
'glue' => ', ',
'suffix' => '',
],
'from' => [
'clause' => 'FROM ',
'prefix' => '',
'glue' => ', ',
'suffix' => '',
'requiresArgument' => true,
],
'join' => [
'clause' => '',
'prefix' => '',
'glue' => "\n",
'suffix' => '',
'requiresArgument' => true,
],
'set' => [
'clause' => 'SET ',
'prefix' => '',
'glue' => ', ',
'suffix' => '',
'requiresArgument' => true,
],
'columns' => [
'clause' => '',
'prefix' => '(',
'glue' => ', ',
'suffix' => ')',
'requiresArgument' => true,
],
'values' => [
'clause' => 'VALUES ',
'prefix' => '(',
'glue' => '), (',
'suffix' => ')',
'requiresArgument' => true,
],
'where' => [
'clause' => 'WHERE ',
'prefix' => '(',
'glue' => ') AND (',
'suffix' => ')',
'requiresArgument' => true,
],
'group' => [
'clause' => 'GROUP BY ',
'prefix' => '',
'glue' => ', ',
'suffix' => '',
'requiresArgument' => true,
],
'having' => [
'clause' => 'HAVING ',
'prefix' => '(',
'glue' => ') AND (',
'suffix' => ')',
'requiresArgument' => true,
],
'order' => [
'clause' => 'ORDER BY ',
'prefix' => '',
'glue' => ', ',
'suffix' => '',
'requiresArgument' => true,
],
'limit' => [
'clause' => 'LIMIT ',
'prefix' => '',
'glue' => '',
'suffix' => '',
'requiresArgument' => true,
],
'offset' => [
'clause' => 'OFFSET ',
'prefix' => '',
'glue' => '',
'suffix' => '',
'requiresArgument' => true,
],
'as' => [
'clause' => 'AS ',
'prefix' => '',
'glue' => false,
'suffix' => '',
'requiresArgument' => true,
],
'duplicate' => [
'clause' => 'ON DUPLICATE KEY UPDATE ',
'prefix' => '',
'glue' => ', ',
'suffix' => '',
'requiresArgument' => true,
],
'modify' => [
'clause' => '',
'prefix' => '',
'glue' => ' ',
'suffix' => '',
'requiresArgument' => true,
],
'forupdate' => [
'clause' => 'FOR UPDATE',
'prefix' => '',
'glue' => '',
'suffix' => '',
'requiresArgument' => false,
],
];
/**
* The keys of this array are the primary clauses that can be present in a
* MySQL query. Each primary clause has a set of valid sub-clauses that can
* be present in a completed query of that type.
*
* @var non-empty-array<string, list<string>>
*/
private static array $possibleClauses = [
'select' => ['from', 'join', 'where', 'group', 'having', 'order', 'limit', 'offset', 'forupdate'],
'insert' => ['set', 'columns', 'values', 'duplicate', 'as'],
'replace' => ['set', 'columns', 'values'],
'update' => ['set', 'where', 'order', 'limit'],
'delete' => ['from', 'where', 'order', 'limit'],
];
/**
* Each query type can be formatted in a number of ways according to
* different sub-trees of its grammar. Each element in the value arrays of
* this array correspond to the minimum required set of sub-clauses needed
* in each of these grammar sub-trees. A query will be considered complete
* if it has all the sub-clauses listed in any of these sets.
*
* @var array<string, list<list<string>>>
*/
private static array $minimumClauses = [
'select' => [['from']],
'insert' => [['set'], ['columns', 'values']],
'replace' => [['set'], ['columns', 'values']],
'update' => [['set']],
'delete' => [['from']],
];
/**
* Each query type can specify a certain selection of modifiers. They each
* change some aspect of how the query runs.
*
* @var array<string, list<string>>
*/
private static array $queryModifiers = [
'select' => [
'ALL', 'DISTINCT', 'DISTINCTROW',
'HIGH_PRIORITY',
'STRAIGHT_JOIN',
'SQL_SMALL_RESULT', 'SQL_BIG_RESULT', 'SQL_BUFFER_RESULT',
'SQL_CACHE', 'SQL_NO_CACHE',
'SQL_CALC_FOUND_ROWS',
],
'insert' => ['LOW_PRIORITY', 'DELAYED', 'HIGH_PRIORITY', 'IGNORE'],
'replace' => ['LOW_PRIORITY', 'DELAYED'],
'update' => ['LOW_PRIORITY', 'IGNORE'],
'delete' => ['LOW_PRIORITY', 'QUICK', 'IGNORE'],
];
public function __construct(
private array $clauses = [],
private array $params = [],
private bool $validateQuery = true,
private bool $useOr = false,
) {
foreach (array_keys(self::$methods) as $method) {
$this->clauses[$method] = [];
$this->params[$method] = [];
}
}
/**
* Append the given clause components and parameters to their existing
* counterparts for the specified clause.
*/
public function __call(string $method, array $args) {
$method = strtolower($method);
if (!isset(self::$methods[$method])) {
throw new Exception("Method \"$method\" does not exist.");
}
$requiresArgument = (isset(self::$methods[$method]['requiresArgument'])
? self::$methods[$method]['requiresArgument']
: false);
if ($requiresArgument && count($args) < 1) {
throw new Exception("Missing argument 1 (\$clauses) for $method()");
} else if (count($args) < 2) {
$clauses = reset($args);
$params = [];
} else {
[$clauses, $params] = $args;
}
if ($clauses instanceof self) {
$clauses->skipValidation();
[$clauses, $params] = $clauses->build(skipClauses: true);
}
if (!is_array($clauses)) {
$clauses = [$clauses];
}
if (!is_array($params)) {
$params = [$params];
}
if (self::$methods[$method]['glue'] === false && count($this->clauses[$method]) > 1) {
throw new Exception("Only one '$method()' is allowed per query");
}
$this->clauses[$method] = array_merge($this->clauses[$method], $clauses);
$this->params[$method] = array_merge($this->params[$method], $params);
return $this;
}
/**
* Combine the clauses and parameters in this QueryGenerator to compose a
* complete query and paramter list.
*
* Incomplete queries will cause a MissingClauseException to be thrown
* (one of MissingPrimaryClauseException or MissingRequiredClauseException)
* unless `skipValidation` has been called.
*
* @param bool $skipClauses : Exclude the 'clause' part (WHERE, SELECT, FROM,
* ...) of each sub-expression. See constructClause
* for more info. This is mostly for internal usage.
*
* Returns an array containing the query and paramter list, respectively.
*
* @return array{0: string, 1: array<string, mixed>}
*/
public function build(bool $skipClauses = false): array {
if ($this->validateQuery) {
$this->assertCompleteQuery();
}
$setMethods = $this->getSetMethods();
$clauses = $params = [];
foreach (array_keys(self::$methods) as $method) {
// Modifiers are handled automatically by constructClause.
if ($method == 'modify') {
continue;
}
// Because we are indiscriminantly interating over every possible
// clause we need to verify that each clause we use has been set.
if (!isset($setMethods[$method])) {
continue;
}
$clauses[] = $this->constructClause($method, $skipClauses);
$params = array_merge($params, $this->params[$method]);
}
return [implode("\n", $clauses), $params];
}
/**
* Bypass query validation when building.
*/
public function skipValidation(): self {
$this->validateQuery = false;
return $this;
}
/**
* Use OR when joining where conditions
*/
public function useOr(): self {
$this->useOr = true;
return $this;
}
/**
* Assert the completeness of this QueryGenerator instance by verifying
* that all required clauses have been set.
*
* @throws MissingPrimaryClauseException
* @throws MissingRequiredClauseException
*/
private function assertCompleteQuery(): void {
$primaryMethod = $this->getPrimaryMethod();
if (!$primaryMethod) {
$primaryClauseStr = implode("', '", $this->getPrimaryClauses());
throw new MissingPrimaryClauseException(
"Missing primary clause. One of '$primaryClauseStr' needed."
);
}
$minimumClauses = self::$minimumClauses[$primaryMethod];
$setMethods = $this->getSetMethods();
foreach ($minimumClauses as $option) {
$intersection = array_intersect($option, $setMethods);
// We will want to compare this array to another for set equality,
// so we need to throw away arbitrary ordering.
sort($option);
sort($intersection);
// A matching minimum set was found.
if ($option == $intersection) {
return;
}
}
$requiredClauseOptions = array_map(function($option) {
return "'" . implode("', '", $option) . "'";
}, $minimumClauses);
$requiredClauseStr = '{' . implode('}, {', $requiredClauseOptions) . '}';
throw new MissingRequiredClauseException(
"Missing required clauses. One of $requiredClauseStr needed."
);
}
/**
* Return the list of primary query clauses.
*
* @return non-empty-list<string>
*/
private static function getPrimaryClauses(): array {
return array_keys(self::$possibleClauses);
}
/**
* Return the primary clause in this QueryGenerator instance.
* If multiple primary clauses have been set, all but the first set clause
* will be ignored.
*/
private function getPrimaryMethod(): string|false {
$primaryClauses = self::getPrimaryClauses();
$setMethods = $this->getSetMethods();
$setPrimaryClauses = array_intersect($primaryClauses, $setMethods);
return reset($setPrimaryClauses);
}
/**
* @return array<string, string>
*/
private function getSetMethods(): array {
$methods = array_keys(array_filter($this->clauses));
return array_combine($methods, $methods);
}
/**
* Return a string of the specified SQL clause using its syntax rules,
* optionally excluding the clause part (i.e. WHERE, SELECT, ...)
*
* Example:
* given where clauses 'foo = ?' and 'bar != ?'
* constructClause('where') => 'WHERE (foo = ?) AND (bar != ?)'
* constructClause('where', false) => '(foo = ?) AND (bar != ?)'
*/
private function constructClause(string $method, bool $skipClause = false): string {
$clauseInfo = self::$methods[$method];
$prefix = $clauseInfo['prefix'];
$clause = $clauseInfo['clause'];
if ($skipClause) {
$clause = '';
// The assumed precondition is that modify's prefix element will never
// contain the substring '<<MODIFIERS>>'.
} else if (strpos($clause, '<<MODIFIERS>>') !== false) {
$clause = str_replace('<<MODIFIERS>>', $this->constructClause('modify'), $clause);
// If there are no modifiers to apply we end up with an extra space
// after the primary verb.
$clause = str_replace(' ', ' ', $clause);
}
$suffix = $clauseInfo['suffix'];
$glue = $this->getGlue($method);
$pieces = implode($glue, $this->clauses[$method]);
return "$clause$prefix$pieces$suffix";
}
/**
* return the appropriate glue string for the given clause, taking into
* account $this->useOr
*/
private function getGlue(string $method): string|false {
if ($method !== 'where' || !$this->useOr) {
return self::$methods[$method]['glue'];
} else {
return ") OR (";
}
}
}
class MissingClauseException extends Exception {}
class MissingPrimaryClauseException extends MissingClauseException {}
class MissingRequiredClauseException extends MissingClauseException {}