# EasyValidate - .NET Validation Library

## Overview
EasyValidate is a modern, type-safe .NET validation library using source generators, Roslyn analyzers, and code fixers. It provides compile-time code generation for efficient runtime validation.

## Installation
```bash
dotnet add package EasyValidate
```

## Quick Start
```csharp
using EasyValidate.Abstractions;
using EasyValidate.Attributes;

// Class MUST be partial and implement IGenerate
public partial class User : IGenerate
{
    [NotNull]
    [NotEmpty]
    public string? Name { get; set; }

    [NotNull]
    [EmailAddress]
    public string? Email { get; set; }

    [Range(18, 120)]
    public int Age { get; set; }
}

// Usage
var user = new User { Name = "John", Email = "john@example.com", Age = 25 };
var result = user.Validate();
if (result.IsValid()) { /* valid */ }
```

## Key Concepts

### 1. IGenerate Interface
All classes with validation attributes MUST:
- Be declared as `partial`
- Implement `IGenerate` interface

### 2. Validation Chains
Group related validations using the `Chain` property:
```csharp
[NotNull(Chain = "shipping")]
[FutureDate(Chain = "shipping")]
public DateTime? ShippingDate { get; set; }
```

### 3. Conditional Validation
Use `ConditionalMethod` to conditionally run validation:
```csharp
[NotNull(ConditionalMethod = nameof(ShouldValidate))]
public string? OptionalField { get; set; }

private bool ShouldValidate(IChainResult result) => condition;
```

### 4. Async Validation
Implement `IAsyncValidationAttribute<T>` for database/API calls:
```csharp
public async Task<AttributeResult> ValidateAsync(string propertyName, string value)
{
    var exists = await _repository.ExistsAsync(value);
    return exists ? AttributeResult.Fail("Already exists") : AttributeResult.Success();
}
```

### 5. Parameter Validation
Apply attributes to method parameters:
```csharp
public void Process([NotNull] string? value, [Range(1, 100)] int count) { }
```

## Available Attributes

### String Attributes
- `NotEmpty` - Not null, empty, or whitespace
- `EmailAddress` - Valid email format
- `Url` - Valid URL
- `Phone` - Valid phone number
- `CreditCard` - Valid credit card (Luhn)
- `Alpha` - Only letters
- `AlphaNumeric` - Only letters and numbers
- `Numeric` - Parseable as number
- `Matches(pattern)` - Regex match
- `StartsWith(prefix)`, `EndsWith(suffix)`, `Contains(substring)`, `NotContains(substring)`
- `OneOf(...values)`, `NotOneOf(...values)`
- `Uppercase`, `Lowercase`, `FirstLetterUpper`
- `NoWhitespace`
- `Guid`, `Hex`, `Color`, `IpAddress`, `MacAddress`, `ISBN`, `Ascii`
- `BaseEncoding(type)`, `FileExtension(...extensions)`, `ValidEnum(typeof(T))`

### Numeric Attributes
- `Range(min, max)` - Value in range
- `Positive`, `Negative`, `NonZero`
- `GreaterThan(value)`, `GreaterThanOrEqualTo(value)`
- `LessThan(value)`, `LessThanOrEqualTo(value)`
- `DivisibleBy(divisor)`, `MultipleOf(value)`
- `EvenNumber`, `OddNumber`, `Prime`, `Fibonacci`
- `PowerOf(base)`
- `MinDigits(count)`, `MaxDigits(count)`

### Date Attributes
- `PastDate`, `FutureDate`, `Today`, `NotTodayDate`
- `NotInPast`, `NotInFuture`
- `DateRange(min, max)`, `TimeRange(start, end)`
- `MinAge(years)`, `MaxAge(years)`, `AgeRange(min, max)`
- `DayOfWeek(...days)`, `Day(...days)`, `Month(...months)`, `Year(...years)`
- `Quarter(...quarters)`
- `LeapYear`, `NotLeapYear`
- `UTC`, `NotUTC`

### Collection Attributes
- `HasElements` - At least one element
- `MinLength(count)`, `MaxLength(count)`, `Length(exactCount)`
- `UniqueElements`, `NoNullElements`
- `ContainsElement(value)`, `NotContainElement(value)`
- `Single(value)`, `SingleOrNone(value)`

### General Attributes
- `NotNull` - Value not null
- `Optional` - Null is allowed
- `NotDefault` - Not default value
- `EqualTo(value)`, `NotEqualTo(value)`

## Common Properties (All Attributes)
- `ErrorCode` - Custom error identifier
- `Chain` - Validation chain name
- `ConditionalMethod` - Method name for conditional execution

## Analyzer Error Codes
- EASY001-003: Attribute inheritance/usage issues
- EASY004-006: Attribute parameter issues
- EASY007-010: Chain validation issues
- EASY011-015: Conditional method issues
- EASY016-019: Setup and design issues

## Best Practices
1. Always use `partial` classes with `IGenerate`
2. Order: `NotNull` → `NotEmpty` → specific validations
3. Use `nameof()` for `ConditionalMethod`
4. Set meaningful `ErrorCode` values
5. Implement both sync and async methods in `IAsyncValidationAttribute`

## Links
- Documentation: https://easy-validate.netlify.app
- Repository: https://github.com/mu-dawood/EasyValidate
- NuGet: https://www.nuget.org/packages/EasyValidate