feat: define custom MySQL WHERE operators (#38)

* feat: add MySQL operators enum

* feat(doc): add custom operators to README

README.md

@@ -210,6 +210,8 @@ In most cases you probably want to UPDATE against a constaint. Chain a [`where()
 
 Filter a [`MySQL->select()`](#select) or [`MySQL->update()`](#update) method by chaining the `MySQL->where()` method anywhere before it. The [`MySQL->delete()`](#delete) executor method also uses the same syntax for its arguments.
 
+Each key, value pair will be `AND` constrained against each other.
+
 ```php
 MySQL->where(
   ?array ...$conditions
@@ -233,9 +235,7 @@ $coffee = MySQL->for("beverages")->where(["beverage_type" => "coffee"])->select(
 ]
 ```
 
-## Advanced filtering
+## Capture groups
-
-You can do more detailed filtering by passing more constraints into the same array, or even futher by passing multiple arrays each with filters.
 
 ### AND
 
@@ -272,6 +272,25 @@ MySQL->where($filter1, $filter2, ...);
 WHERE (beverage_type = 'coffee' AND beverage_size = 15) OR (beverage_type = 'tea' AND beverage_name = 'black')
 ```
 
+## Define custom operators
+
+By default, all values in an the assoc array passed to `where()` will be treated as an `EQUALS` (=) operator.
+
+```php
+MySQL->where(["column" => "euqals_this_value"]);
+```
+
+Setting the value of any key to another assoc array will allow for more "advanced" filtering by defining your own [`Operators`](https://github.com/VictorWesterlund/php-libmysqldriver/blob/master/src/Operators.php).
+
+The key of this subarray can be any MySQL operator string, or the **->value** of any case in the [`Operators`](https://github.com/VictorWesterlund/php-libmysqldriver/blob/master/src/Operators.php) enum.
+
+```php
+MySQL->where([
+  "beverage_name" => [
+    Operators::LIKE->value => "%wildcard_contains%"
+  ]
+]);
+```
 
 # ORDER BY
 

src/MySQL.php

@@ -2,11 +2,15 @@
 
 	namespace libmysqldriver;
 
-	use \Exception;
+	use Exception;
+	
+	use mysqli;
+	use mysqli_stmt;
+	use mysqli_result;
 
-	use \mysqli;
+	use libmysqldriver\Operators;
-	use \mysqli_stmt;
+
-	use \mysqli_result;
+	require_once "Operators.php";
 
 	// Interface for MySQL_Driver with abstractions for data manipulation
 	class MySQL extends mysqli {
@@ -121,21 +125,36 @@
 				}
 
 				// Create SQL string and append values to array for prepared statement
-				foreach ($condition as $col => $value) {
+				foreach ($condition as $col => $operation) {
 					if ($this->model && !$this->in_model($col)) {
 						continue;
 					}
 
-					// Value is null so it does not need to be added to the prepared statement
+					// Assume we want an equals comparison if value is not an array
-					if (is_null($value)) {
+					if (!is_array($operation)) {
-						$filter[] = "`{$col}` IS NULL";
+						$operation = [Operators::EQUALS->value => $operation];
-						continue;
 					}
 
-					// Create SQL for prepared statement
+					// Resolve all operator enum values in inner array
-					$filter[] = "`{$col}` = ?";
+					foreach ($operation as $operator => $value) {
-					// Append value to array with all other values
+						// Null values have special syntax
-					$values[] = $value;
+						if (is_null($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

src/Operators.php

@@ -0,0 +1,46 @@
+<?php
+
+	namespace libmysqldriver;
+
+	enum Operators: string {
+		// Logical
+		case ALL     = "ALL";
+		case AND     = "AND";
+		case ANY     = "ANY";
+		case BETWEEN = "BETWEEN";
+		case EXISTS  = "EXISTS";
+		case IN      = "IN";
+		case LIKE    = "LIKE";
+		case NOT     = "NOT";
+		case OR      = "OR";
+		case SOME    = "SOME";
+
+		// Comparison
+		case EQUALS = "=";
+		case GT     = ">";
+		case LT     = "<";
+		case GTE    = ">=";
+		case LTE    = "<=";
+		case NOTE   = "<>";
+
+		// Arithmetic
+		case ADD      = "+";
+		case SUBTRACT = "-";
+		case MULTIPLY = "*";
+		case DIVIDE   = "/";
+		case MODULO   = "%"; 
+
+		// Bitwise
+		case BS_AND = "&";
+		case BS_OR  = "|";
+		case BS_XOR = "^";
+
+		// Compound
+		case ADDE    = "+=";
+		case SUBE    = "-=";
+		case DIVE    = "/=";
+		case MODE    = "%=";
+		case BS_ANDE = "&=";
+		case BS_ORE  = "|*=";
+		case BS_XORE = "^-=";
+	}