<?php

	namespace vlw\MySQL;

	use Exception;
	
	use mysqli;
	use mysqli_stmt;
	use mysqli_result;

	use vlw\MySQL\Order;
	use vlw\MySQL\Operators;

	require_once "Order.php";
	require_once "Operators.php";

	// Interface for MySQL_Driver with abstractions for data manipulation
	class MySQL extends mysqli {
		public ?array $columns = null;
		
		protected string $table;
		protected ?string $limit = null;
		protected ?string $order_by = null;
		protected array $filter_columns = [];
		protected array $filter_values = [];
		protected ?string $filter_sql = null;

		// Pass constructor arguments to driver
		function __construct() {
			parent::__construct(...func_get_args());
		}

		/*
			# Helper methods
		*/

		private function throw_if_no_table() {
			if (!$this->table) {
				throw new Exception("No table name defined");
			}
		}

		// Coerce input to single dimensional array
		private static function to_list_array(mixed $input): array {
			return array_values(is_array($input) ? $input : [$input]);
		}

		// Convert value to MySQL tinyint
		private static function filter_boolean(mixed $value): int {
			return (int) filter_var($value, FILTER_VALIDATE_BOOLEAN);
		}

		// Convert all boolean type values to tinyints in array
		private static function filter_booleans(array $values): array {
			return array_map(fn(mixed $v): mixed => gettype($v) === "boolean" ? self::filter_boolean($v) : $v, $values);
		}

		private static function array_wrap_accents(array $input): array {
			return array_map(fn(mixed $v): string => "`{$v}`", $input);
		}

		/*
			# Definers
			These methods are used to build an SQL query by chaining methods together.
			Defined parameters will then be executed by an Executer method.
		*/

		// Use the following table name
		public function from(string $table): self {
			// Reset all definers when a new query begins
			$this->where();
			$this->limit();
			$this->order();

			$this->table = $table;
			return $this;
		}

		#[\Deprecated(
			message: "use MySQL->from() instead",
			since: "3.5.7",
		)]
		public function for(string $table): self {
			$this->from($table);
		}

		// Create a WHERE statement from filters
		public function where(?array ...$conditions): self {
			// Unset filters if null was passed
			if ($conditions === null) {
				$this->filter_sql = null;
				$this->filter_columns = null;
				$this->filter_values = null;

				return $this;
			}

			$values = [];
			$filters = [];

			// Group each condition into an AND block
			foreach ($conditions as $condition) {
				$filter = [];

				// Move along if the condition is empty
				if (empty($condition)) {
					continue;
				}

				// Create SQL string and append values to array for prepared statement
				foreach ($condition as $col => $operation) {
					$this->filter_columns[] = $col;

					// Assume we want an equals comparison if value is not an array
					if (!is_array($operation)) {
						$operation = [Operators::EQUALS->value => $operation];
					}

					// Resolve all operator enum values in inner array
					foreach ($operation as $operator => $value) {
						// Null values have special syntax
						if (is_null($value)) {
							// Treat anything that isn't an equals operator as falsy
							if ($operator !== Operators::EQUALS->value) {
								$filter[] = "`{$col}` IS NOT NULL";
								continue;
							}

							$filter[] = "`{$col}` IS NULL";	
							continue;
						}

						// Create SQL for prepared statement
						$filter[] = "`{$col}` {$operator} ?";
						
						// Append value to array with all other values
						$values[] = $value;
					}
				}

				// AND together all conditions into a group
				$filters[] = "(" . implode(" AND ", $filter) . ")";
			}

			// Do nothing if no filters were set
			if (empty($filters)) {
				return $this;
			}

			// OR all filter groups
			$this->filter_sql = implode(" OR ", $filters);
			// Set values property
			$this->filter_values = $values;

			return $this;
		}

		// SQL LIMIT string
		public function limit(?int $limit = null, ?int $offset = null): self {
			// Unset row limit if null was passed
			if ($limit === null) {
				$this->limit = null;
				return $this;
			}

			// Set LIMIT without range directly as integer
			if (is_int($limit)) {
				$this->limit = $limit;
				return $this;
			}

			// No offset defined, set limit property directly as string
			if (is_null($offset)) {
				$this->limit = (string) $limit;
				return $this;
			}

			// Set limit and offset as SQL CSV
			$this->limit = "{$offset},{$limit}";
			return $this;
		}

		// Return SQL SORT BY string from assoc array of columns and direction
		public function order(?array $order_by = null): self {
			// Unset row order by if null was passed
			if ($order_by === null) {
				$this->order_by = null;
				return $this;
			}

			// Assign Order Enum entries from array of arrays<Order|string>
			$orders = array_map(fn(Order|string $order): Order => $order instanceof Order ? $order : Order::tryFrom($order), array_values($order_by));
			// Create CSV string with Prepared Statement abbreviations from length of fields array.
			$sql = array_map(fn(string $column, Order|string $order): string => "`{$column}` " . $order->value, array_keys($order_by), $orders);

			$this->order_by = implode(",", $sql);
			return $this;
		}

		/*
			# Executors
			These methods execute various statements that each return a mysqli_result
		*/

		// Create Prepared Statament for SELECT with optional WHERE filters
		public function select(array|string|null $columns = null): mysqli_result|bool {
			$this->throw_if_no_table();

			// Create array of columns from CSV
			$this->columns = is_array($columns) || is_null($columns) ? $columns : explode(",", $columns);

			// Create CSV from columns or default to SQL NULL as a string
			$columns_sql = $this->columns ? implode(",", self::array_wrap_accents($this->columns)) : "NULL";

			// Create LIMIT statement if argument is defined
			$limit_sql = !is_null($this->limit) ? " LIMIT {$this->limit}" : "";

			// Create ORDER BY statement if argument is defined
			$order_by_sql = !is_null($this->order_by) ? " ORDER BY {$this->order_by}" : "";

			// Get array of SQL WHERE string and filter values
			$filter_sql = !is_null($this->filter_sql) ? " WHERE {$this->filter_sql}" : "";

			// Interpolate components into an SQL SELECT statmenet and execute
			$sql = "SELECT {$columns_sql} FROM `{$this->table}`{$filter_sql}{$order_by_sql}{$limit_sql}";
			// Return mysqli_response of matched rows
			return $this->execute_query($sql, self::to_list_array($this->filter_values));
		}

		// Create Prepared Statement for UPDATE using PRIMARY KEY as anchor
		public function update(array $entity): mysqli_result|bool {
			$this->throw_if_no_table();

			// Create CSV string with Prepared Statement abbreviations from length of fields array.
			$changes = array_map(fn($column) => "`{$column}` = ?", array_keys($entity));
			$changes = implode(",", $changes);

			// Get array of SQL WHERE string and filter values
			$filter_sql = !is_null($this->filter_sql) ? " WHERE {$this->filter_sql}" : "";

			// Get values from entity and convert booleans to tinyint
			$values = self::filter_booleans(array_values($entity));
			
			// Append values to filter property if where() was chained
			if ($this->filter_values) {
				array_push($values, ...$this->filter_values);
			}

			// Interpolate components into an SQL UPDATE statement and execute
			$sql = "UPDATE `{$this->table}` SET {$changes} {$filter_sql}";
			return $this->execute_query($sql, self::to_list_array($values));
		}

		// Create Prepared Statemt for INSERT
		public function insert(array $values): mysqli_result|bool {
			$this->throw_if_no_table();

			/*
				Use array keys from $values as columns to insert if array is associative.
				Treat statement as an all-columns INSERT if the $values array is sequential.
			*/
			$columns = !array_is_list($values) ? "(" . implode(",", array_keys($values)) . ")" : "";

			// Convert booleans to tinyint
			$values = self::filter_booleans($values);

			// Create CSV string with Prepared Statement abbreviatons from length of fields array.
			$values_stmt = implode(",", array_fill(0, count($values), "?"));

			// Interpolate components into an SQL INSERT statement and execute
			$sql = "INSERT INTO `{$this->table}` {$columns} VALUES ({$values_stmt})";
			return $this->execute_query($sql, self::to_list_array($values));
		}

		// Create Prepared Statemente for DELETE with WHERE condition(s)
		public function delete(array ...$conditions): mysqli_result|bool {
			$this->throw_if_no_table();

			// Set DELETE WHERE conditions from arguments
			$this->where(...$conditions);

			$sql = "DELETE FROM `{$this->table}` WHERE {$this->filter_sql}";
			return $this->execute_query($sql, self::to_list_array($this->filter_values));
		}

		// Execute SQL query with optional prepared statement and return mysqli_result
		public function exec(string $sql, mixed $params = null): mysqli_result {
			return $this->execute_query($sql, self::to_list_array($params));
		}
	}