Add support for negative lookups to constraints.

README.md

@@ -112,6 +112,7 @@ The config is composed of many objects in the `patterns` array:
       - `field`: a string representing the name of the field.
       - `position`: the 1-based index of what number column this field represents. For instance, assuming a table with 3 columns `foo`, `bar`, and `baz`, and you wished to modify the `bar` column, this value would be `2`.
       - `value`: string value to match against.
+      - `compare`: An optional string stating how to treat the constraints.
 
 ### Constraints
 
@@ -126,13 +127,23 @@ Supposing you have a WordPress database and you need to modify certain meta, be
     {
       "field": "meta_key",
       "position": 3,
-      "value": "last_ip_address"
+      "value": "last_ip_address",
+      "compare": "like"
     }
   ]
 }
-
 ```
 
+#### Compare rules
+Constraints allow the user to define rules for how to treat the comparison value. The following rules are supported:
+
+**PS: Remember that comparison rules are first come first serve, so as soon as a rule that would negate the anonymization of a field is found, it will short-circuit any further rules. You should also try to avoid comapring against other fields, remember that a field you may wish to compare against may already have been modified and no longer give the expected value!**
+
+- `like`: The default behavior. The SQL value must be equal to the constraint `value` field.
+- `not like`: The SQL value must not be equal to the constraint `value` field.
+- `regex`: The SQL value must match the regex string given in the `value` field.
+- `regex not like`: The inverse of `regex`, and requires the regex patter to not match the SQL value.
+
 ### Field Types
 
 Each column stores a certain type of data, be it a name, username, email, etc. The `type` property in the config is used to define the type of data stored, and ultimately the type of random data to be inserted into the field. [https://github.com/dmgk/faker](https://github.com/dmgk/faker) is used for generating the fake data. These are the types currently supported:

internal/anonymize/anonymize.go

@@ -357,10 +357,37 @@ func rowObeysConstraints(constraints []config.PatternFieldConstraint, row sqlpar
 
 		parsedValue := convertSQLValToString(value)
 		// TODO: Add behing a flag for debugging.
-		//log.Printf("Error: Constraint obediance, parsed value: %s, constraint value: %s.", parsedValue, constraint.Value)
-
-		if parsedValue != constraint.Value {
-			return false
+		//log.Printf("Error: Constraint obediance, parsed value: %s, constraint value: %s, and comparator: %s.", parsedValue, constraint.Value, constraint.Compare)
+
+		switch constraint.Compare {
+		case "not like",
+			"<>",
+			"!=":
+			if parsedValue == constraint.Value {
+				return false
+			}
+		case "regex not like":
+			re := regexp.MustCompile(constraint.Value)
+			match := re.MatchString(parsedValue)
+			if match {
+				return false
+			}
+		case "regex":
+			re := regexp.MustCompile(constraint.Value)
+			match := re.MatchString(parsedValue)
+			if !match {
+				return false
+			}
+		case "like",
+			"==",
+			"=":
+			if parsedValue != constraint.Value {
+				return false
+			}
+		default:
+			if parsedValue != constraint.Value {
+				return false
+			}
 		}
 	}
 	return true

internal/config/config.go

@@ -38,6 +38,7 @@ type PatternFieldConstraint struct {
 	Field    string `json:"field"`
 	Position int    `json:"position"`
 	Value    string `json:"value"`
+	Compare  string `json:"compare"`
 }
 
 // New creates a new Config from flags and environment variables

internal/embed/files/config.default.json

@@ -7,13 +7,27 @@
           "field": "user_login",
           "position": 2,
           "type": "username",
-          "constraints": null
+          "constraints": [
+            {
+              "field": "user_login",
+              "position": 2,
+              "value": "myaccount",
+              "compare": "not like"
+            }
+          ]
         },
         {
           "field": "user_pass",
           "position": 3,
           "type": "password",
-          "constraints": null
+          "constraints": [
+            {
+              "field": "user_login",
+              "position": 2,
+              "value": "myaccount",
+              "compare": "not like"
+            }
+          ]
         },
         {
           "field": "user_nicename",