Add support for LOCK and UNLOCK Statements

Signed-off-by: Deven Bansod <devenbansod.bits@gmail.com>

1 files changed, 203 insertions, 0 deletions

diff --git a/src/Components/LockExpression.php b/src/Components/LockExpression.php
new file mode 100644
index 0000000..644e3ca
--- /dev/null
+++ b/src/Components/LockExpression.php
@@ -0,0 +1,203 @@
+<?php
+
+/**
+ * Parses a reference to a LOCK expression.
+ */
+
+namespace PhpMyAdmin\SqlParser\Components;
+
+use PhpMyAdmin\SqlParser\Component;
+use PhpMyAdmin\SqlParser\Parser;
+use PhpMyAdmin\SqlParser\Token;
+use PhpMyAdmin\SqlParser\TokensList;
+
+/**
+ * Parses a reference to a LOCK expression.
+ *
+ * @category   Components
+ *
+ * @license    https://www.gnu.org/licenses/gpl-2.0.txt GPL-2.0+
+ */
+class LockExpression extends Component
+{
+    /**
+     * The table to be locked.
+     *
+     * @var Expression
+     */
+    public $table;
+
+    /**
+     * The type of lock to be applied.
+     *
+     * @var string
+     */
+    public $type;
+
+    /**
+     * @param Parser     $parser the parser that serves as context
+     * @param TokensList $list   the list of tokens that are being parsed
+     * @param array      $options parameters for parsing
+     *
+     * @return CaseExpression
+     */
+    public static function parse(Parser $parser, TokensList $list, array $options = array())
+    {
+        $ret = new self();
+
+        /**
+         * The state of the parser.
+         *
+         * Below are the states of the parser.
+         *
+         *      0 ---------------- [ tbl_name ] -----------------> 1
+         *      1 ---------------- [ lock_type ] ----------------> 2
+         *      2 -------------------- [ , ] --------------------> break
+         *
+         * @var int
+         */
+        $state = 0;
+
+        $prevToken = null;
+
+        for (; $list->idx < $list->count; ++$list->idx) {
+            /**
+             * Token parsed at this moment.
+             *
+             * @var Token
+             */
+            $token = $list->tokens[$list->idx];
+
+            // End of statement.
+            if ($token->type === Token::TYPE_DELIMITER
+                || ($token->type === Token::TYPE_OPERATOR
+                && $token->value === ',')
+            ) {
+                break;
+            }
+
+            if ($state === 0) {
+                $ret->table = Expression::parse($parser, $list, array('parseField' => 'table'));
+                $state = 1;
+            } elseif ($state === 1) {
+                // parse lock type
+                $ret->type = self::parseLockType($parser, $list);
+                $state = 2;
+            }
+            $prevToken = $token;
+        }
+
+        // 2 is the only valid end state
+        if ($state !== 2) {
+            $parser->error('Unexpected end of LOCK expression.', $prevToken);
+        }
+
+        --$list->idx;
+
+        return $ret;
+    }
+
+    /**
+     * @param LockExpression|LockExpression[] $component the component to be built
+     * @param array                           $options   parameters for building
+     *
+     * @return string
+     */
+    public static function build($component, array $options = array())
+    {
+        if (is_array($component)) {
+            return implode(', ', $component);
+        }
+
+        return $component->table . ' ' . $component->type;
+    }
+
+    private static function parseLockType(Parser $parser, TokensList $list) {
+        $lockType = '';
+
+        /**
+         * The state of the parser while parsing for lock type.
+         *
+         * Below are the states of the parser.
+         *
+         *      0 ---------------- [ READ ] -----------------> 1
+         *      0 ------------- [ LOW_PRIORITY ] ------------> 2
+         *      0 ---------------- [ WRITE ] ----------------> 3
+         *      1 ---------------- [ LOCAL ] ----------------> 3
+         *      2 ---------------- [ WRITE ] ----------------> 3
+         *
+         * @var int
+         */
+        $state = 0;
+
+        $prevToken = null;
+
+        for (; $list->idx < $list->count; ++$list->idx) {
+            /**
+             * Token parsed at this moment.
+             *
+             * @var Token
+             */
+            $token = $list->tokens[$list->idx];
+
+            // End of statement.
+            if ($token->type === Token::TYPE_DELIMITER
+                || ($token->type === Token::TYPE_OPERATOR
+                && $token->value === ',')
+            ) {
+                --$list->idx;
+                break;
+            }
+
+            // Skipping whitespaces and comments.
+            if ($token->type === Token::TYPE_WHITESPACE || $token->type === Token::TYPE_COMMENT) {
+                continue;
+            }
+
+            // We only expect keywords
+            if ($token->type !== Token::TYPE_KEYWORD) {
+                $parser->error('Unexpected token.', $token);
+                break;
+            }
+
+            if ($state === 0) {
+                if ($token->keyword === 'READ') {
+                    $state = 1;
+                } elseif ($token->keyword === 'LOW_PRIORITY') {
+                    $state = 2;
+                } elseif ($token->keyword === 'WRITE') {
+                    $state = 3;
+                } else {
+                    $parser->error('Unexpected keyword.', $token);
+                    break;
+                }
+                $lockType .= $token->keyword;
+            } elseif ($state === 1) {
+                if ($token->keyword === 'LOCAL') {
+                    $lockType .= ' ' . $token->keyword;
+                    $state = 3;
+                } else {
+                    $parser->error('Unexpected keyword.', $token);
+                    break;
+                }
+            } elseif ($state === 2) {
+                if ($token->keyword === 'WRITE') {
+                    $lockType .= ' ' . $token->keyword;
+                    $state = 3; // parsing over
+                } else {
+                    $parser->error('Unexpected keyword.', $token);
+                    break;
+                }
+            }
+
+            $prevToken = $token;
+        }
+
+        // Only  two possible end states
+        if ($state !== 1 && $state !== 3) {
+            $parser->error('Unexpected end of Lock expression.', $prevToken);
+        }
+
+        return $lockType;
+    }
+}