using System;
using System.Text.RegularExpressions;

namespace Swan.Validators {
  /// <summary>
  /// Regex validator.
  /// </summary>
  [AttributeUsage(AttributeTargets.Property)]
  public class MatchAttribute : Attribute, IValidator {
    /// <summary>
    /// Initializes a new instance of the <see cref="MatchAttribute" /> class.
    /// </summary>
    /// <param name="regex">A regex string.</param>
    /// <param name="errorMessage">The error message.</param>
    /// <exception cref="ArgumentNullException">Expression.</exception>
    public MatchAttribute(String regex, String errorMessage = null) {
      this.Expression = regex ?? throw new ArgumentNullException(nameof(regex));
      this.ErrorMessage = errorMessage ?? "String does not match the specified regular expression";
    }

    /// <summary>
    /// The string regex used to find a match.
    /// </summary>
    public String Expression {
      get;
    }

    /// <inheritdoc/>
    public String ErrorMessage {
      get; internal set;
    }

    /// <inheritdoc/>
    public Boolean IsValid<T>(T value) => Equals(value, default(T)) ? false : !(value is String) ? throw new ArgumentException("Property is not a string") : Regex.IsMatch(value.ToString(), this.Expression);
  }

  /// <summary>
  /// Email validator.
  /// </summary>
  [AttributeUsage(AttributeTargets.Property)]
  public class EmailAttribute : MatchAttribute {
    private const String EmailRegExp =
        @"^(?("")("".+?(?<!\\)""@)|(([0-9a-z]((\.(?!\.))|[-!#\$%&'\*\+/=\?\^`\{\}\|~\w])*)(?<=[0-9a-z])@))" +
        @"(?(\[)(\[(\d{1,3}\.){3}\d{1,3}\])|(([0-9a-z][-0-9a-z]*[0-9a-z]*\.)+[a-z0-9][\-a-z0-9]{0,22}[a-z0-9]))$";

    /// <summary>
    /// Initializes a new instance of the <see cref="EmailAttribute"/> class.
    /// </summary>
    /// <param name="errorMessage">The error message.</param>
    public EmailAttribute(String errorMessage = null) : base(EmailRegExp, errorMessage ?? "String is not an email") {
    }
  }

  /// <summary>
  /// A not null validator.
  /// </summary>
  [AttributeUsage(AttributeTargets.Property)]
  public class NotNullAttribute : Attribute, IValidator {
    /// <inheritdoc/>
    public String ErrorMessage => "Value is null";

    /// <inheritdoc/>
    public Boolean IsValid<T>(T value) => !Equals(default(T), value);
  }

  /// <summary>
  /// A range constraint validator.
  /// </summary>
  [AttributeUsage(AttributeTargets.Property)]
  public class RangeAttribute : Attribute, IValidator {
    /// <summary>
    /// Initializes a new instance of the <see cref="RangeAttribute"/> class.
    /// Constructor that takes integer minimum and maximum values.
    /// </summary>
    /// <param name="min">The minimum value.</param>
    /// <param name="max">The maximum value.</param>
    public RangeAttribute(Int32 min, Int32 max) {
      if(min >= max) {
        throw new InvalidOperationException("Maximum value must be greater than minimum");
      }

      this.Maximum = max;
      this.Minimum = min;
    }

    /// <summary>
    /// Initializes a new instance of the <see cref="RangeAttribute"/> class.
    /// Constructor that takes double minimum and maximum values.
    /// </summary>
    /// <param name="min">The minimum value.</param>
    /// <param name="max">The maximum value.</param>
    public RangeAttribute(Double min, Double max) {
      if(min >= max) {
        throw new InvalidOperationException("Maximum value must be greater than minimum");
      }

      this.Maximum = max;
      this.Minimum = min;
    }

    /// <inheritdoc/>
    public String ErrorMessage => "Value is not within the specified range";

    /// <summary>
    /// Maximum value for the range.
    /// </summary>
    public IComparable Maximum {
      get;
    }

    /// <summary>
    /// Minimum value for the range.
    /// </summary>
    public IComparable Minimum {
      get;
    }

    /// <inheritdoc/>
    public Boolean IsValid<T>(T value) => value is IComparable comparable ? comparable.CompareTo(this.Minimum) >= 0 && comparable.CompareTo(this.Maximum) <= 0 : throw new ArgumentException(nameof(value));
  }
}