Initial SQLite development (#1)

Reviewed-on: #1

src/Exists.php

@@ -0,0 +1,40 @@
+<?php declare(strict_types=1);
+
+namespace BitBadger\PDODocument;
+
+use BitBadger\PDODocument\Mapper\ExistsMapper;
+
+/**
+ * Functions to determine if documents exist
+ */
+class Exists
+{
+    /**
+     * Determine if a document exists for the given ID
+     *
+     * @param string $tableName The name of the table in which document existence should be determined
+     * @param mixed $docId The ID of the document whose existence should be determined
+     * @return bool True if the document exists, false if not
+     * @throws DocumentException If any is encountered
+     */
+    public static function byId(string $tableName, mixed $docId): bool
+    {
+        return Custom::scalar(Query\Exists::byId($tableName), Parameters::id($docId), new ExistsMapper());
+    }
+
+    /**
+     * Determine if a document exists using a comparison on JSON fields
+     *
+     * @param string $tableName The name of the table in which document existence should be determined
+     * @param Field[] $fields The field comparison to match
+     * @param string $conjunction How to handle multiple conditions (optional; defaults to `AND`)
+     * @return bool True if any documents match the field comparison, false if not
+     * @throws DocumentException If any is encountered
+     */
+    public static function byFields(string $tableName, array $fields, string $conjunction = 'AND'): bool
+    {
+        $namedFields = Parameters::nameFields($fields);
+        return Custom::scalar(Query\Exists::byFields($tableName, $namedFields, $conjunction),
+            Parameters::addFields($namedFields, []), new ExistsMapper());
+    }
+}