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//
// Gendarme.Rules.Smells.AvoidLargeClassesRule class
//
// Authors:
// Néstor Salceda <nestor.salceda@gmail.com>
//
// (C) 2007-2008 Néstor Salceda
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//
using System;
using Mono.Cecil;
using Gendarme.Framework;
using Gendarme.Framework.Rocks;
namespace Gendarme.Rules.Smells {
// TODO: The summary should explain what a field prefix is.
// What do field prefixes have to do with large classes?
// The problem text says that the issue with large classes is that "duplicated code will not
// be far away". This does not seem to me to be the real issue with large classes. The
// problem is more that they are difficult to understand and to maintain.
// Can the default be changed?
/// <summary>
/// This rule allows developers to measure the classes size. When a
/// class is trying to doing a lot of work, then you probabily have
/// the Large Class smell.
///
/// This rule will fire if a type contains too many fields (over 25 by default) or
/// has fields with common prefixes. If the rule does fire then the type should
/// be reviewed to see if new classes should be extracted from it.
/// </summary>
/// <example>
/// Bad example:
/// <code>
/// public class MyClass {
/// int x, x1, x2, x3;
/// string s, s1, s2, s3;
/// DateTime bar, bar1, bar2;
/// string[] strings, strings1;
/// }
/// </code>
/// </example>
/// <example>
/// Good example:
/// <code>
/// public class MyClass {
/// int x;
/// string s;
/// DateTime bar;
/// }
/// </code>
/// </example>
//SUGGESTION: Public / Private ratios.
//SUGGESTION: Lines of Code.
//SUGGESTION: Weird distributions.
[Problem ("The class is trying to do too much. Generally if a class is too large, duplicated code will not be far away.")]
[Solution ("You can apply the Extract Class or Extract Subclass refactoring.")]
public class AvoidLargeClassesRule : Rule,ITypeRule {
private static int maxFields = 25;
public static int MaxFields {
get {
return maxFields;
}
set {
maxFields = value;
}
}
private static bool IsTooLarge (TypeDefinition type)
{
int counter = 0;
//Skip the constants and others related from this check.
//It's common use a class for store constants, by
//example: Gendarme.Framework.MethodSignatures.
foreach (FieldDefinition field in type.Fields) {
if (field.IsSpecialName || field.HasConstant || field.IsInitOnly)
continue;
if (field.IsGeneratedCode ())
continue;
counter++;
}
return counter >= MaxFields;
}
private RuleResult CheckForClassFields (TypeDefinition type)
{
if (IsTooLarge (type)) {
Runner.Report (type, Severity.High, Confidence.High, "This type contains a lot of fields.");
}
return RuleResult.Success;
}
private static bool HasPrefixedFields (string prefix, TypeDefinition type)
{
if (prefix.Length == 0)
return false;
int counter = 0;
foreach (FieldDefinition field in type.Fields) {
if (field.Name.StartsWith (prefix))
counter++;
}
return counter > 1;
}
private static int GetIndexOfFirst (string value, Predicate<char> predicate)
{
foreach (char character in value)
if (predicate (character))
return value.IndexOf (character);
return -1;
}
private static int GetIndexOfFirstDash (string value)
{
bool valueTruncated = false;
if (value.IndexOf ('_') == 1) {
value = value.Substring (2, value.Length - 2);
valueTruncated = true;
}
foreach (char character in value) {
if (character.Equals ('_'))
return value.IndexOf (character) + (valueTruncated? 2 : 0);
}
return -1;
}
private static string GetFieldPrefix (FieldDefinition field)
{
int index = GetIndexOfFirst (field.Name, delegate (char character) {return Char.IsNumber (character);});
if (index != -1)
return field.Name.Substring (0, index);
index = GetIndexOfFirst (field.Name, delegate (char character) {return Char.IsUpper (character);});
if (index != -1)
return field.Name.Substring (0, index);
index = GetIndexOfFirstDash (field.Name);
if (index != -1)
return field.Name.Substring (0, index);
return String.Empty;
}
private bool ExitsCommonPrefixes (TypeDefinition type)
{
foreach (FieldDefinition field in type.Fields) {
// skip special, constant and read-only fields
if (field.IsSpecialName || field.HasConstant || field.IsInitOnly)
continue;
// skip C# 3 fields generated for auto-implemented properties
if (field.IsGeneratedCode ())
continue;
string prefix = GetFieldPrefix (field);
if (HasPrefixedFields (prefix, type)) {
Runner.Report (type, Severity.Medium, Confidence.High, "This type contains common prefixes.");
return true;
}
}
return false;
}
private RuleResult CheckForCommonPrefixesInFields (TypeDefinition type)
{
if (ExitsCommonPrefixes (type))
return RuleResult.Failure;
return RuleResult.Success;
}
public RuleResult CheckType (TypeDefinition type)
{
if (type.IsEnum || !type.HasFields || type.IsGeneratedCode ())
return RuleResult.DoesNotApply;
CheckForClassFields (type);
CheckForCommonPrefixesInFields (type);
return Runner.CurrentRuleResult;
}
}
}
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