using Swan.Reflection;
using System;
using System.Collections.Generic;
using System.Linq;

namespace Swan.Parsers {
  /// <summary>
  /// Provides methods to parse command line arguments.
  /// Based on CommandLine (Copyright 2005-2015 Giacomo Stelluti Scala and Contributors.).
  /// </summary>
  /// <example>
  /// The following example shows how to parse CLI arguments into objects.
  /// <code>
  /// class Example 
  /// {
  ///     using System;
  ///     using Swan.Parsers;
  ///     
  ///     static void Main(string[] args)
  ///     {
  ///         // parse the supplied command-line arguments into the options object
  ///         var res = Runtime.ArgumentParser.ParseArguments(args, out var options);
  ///     }
  ///     
  ///     class Options
  ///     {
  ///         [ArgumentOption('v', "verbose", HelpText = "Set verbose mode.")]
  ///         public bool Verbose { get; set; }
  ///
  ///         [ArgumentOption('u', Required = true, HelpText = "Set user name.")]
  ///         public string Username { get; set; }
  ///
  ///         [ArgumentOption('n', "names", Separator = ',',
  ///         Required = true, HelpText = "A list of files separated by a comma")]
  ///         public string[] Files { get; set; }
  ///         
  ///         [ArgumentOption('p', "port", DefaultValue = 22, HelpText = "Set port.")]
  ///         public int Port { get; set; }
  ///
  ///         [ArgumentOption("color", DefaultValue = ConsoleColor.Red,
  ///         HelpText = "Set a color.")]
  ///         public ConsoleColor Color { get; set; }
  ///     }
  /// }
  /// </code>
  /// The following code describes how to parse CLI verbs.
  /// <code>
  /// class Example2 
  /// {
  ///     using Swan;
  ///     using Swan.Parsers;
  ///     
  ///     static void Main(string[] args)
  ///     {
  ///         // create an instance of the VerbOptions class
  ///         var options = new VerbOptions();
  ///         
  ///         // parse the supplied command-line arguments into the options object
  ///         var res = Runtime.ArgumentParser.ParseArguments(args, options);
  ///         
  ///         // if there were no errors parsing
  ///         if (res)
  ///         {
  ///             if(options.Run != null)
  ///             {
  ///                 // run verb was selected
  ///             }
  ///             
  ///             if(options.Print != null)
  ///             {
  ///                 // print verb was selected
  ///             }
  ///         }
  ///         
  ///         // flush all error messages
  ///         Terminal.Flush();
  ///     }
  ///     
  ///     class VerbOptions
  ///     {
  ///         [VerbOption("run", HelpText = "Run verb.")]
  ///         public RunVerbOption Run { get; set; }
  ///         
  ///         [VerbOption("print", HelpText = "Print verb.")]
  ///         public PrintVerbOption Print { get; set; }
  ///     }
  ///     
  ///     class RunVerbOption
  ///     {
  ///         [ArgumentOption('o', "outdir", HelpText = "Output directory",
  ///         DefaultValue = "", Required = false)]
  ///         public string OutDir { get; set; }
  ///     }
  ///     
  ///     class PrintVerbOption
  ///     {
  ///         [ArgumentOption('t', "text", HelpText = "Text to print",
  ///         DefaultValue = "", Required = false)]
  ///         public string Text { get; set; }
  ///     }
  /// }
  /// </code>
  /// </example>
  public partial class ArgumentParser {
    /// <summary>
    /// Initializes a new instance of the <see cref="ArgumentParser"/> class.
    /// </summary>
    public ArgumentParser() : this(new ArgumentParserSettings()) {
    }

    /// <summary>
    /// Initializes a new instance of the <see cref="ArgumentParser" /> class,
    /// configurable with <see cref="ArgumentParserSettings" /> using a delegate.
    /// </summary>
    /// <param name="parseSettings">The parse settings.</param>
    public ArgumentParser(ArgumentParserSettings parseSettings) => this.Settings = parseSettings ?? throw new ArgumentNullException(nameof(parseSettings));

    /// <summary>
    /// Gets the current.
    /// </summary>
    /// <value>
    /// The current.
    /// </value>
    public static ArgumentParser Current { get; } = new ArgumentParser();

    /// <summary>
    /// Gets the instance that implements <see cref="ArgumentParserSettings" /> in use.
    /// </summary>
    /// <value>
    /// The settings.
    /// </value>
    public ArgumentParserSettings Settings {
      get;
    }

    /// <summary>
    /// Parses a string array of command line arguments constructing values in an instance of type <typeparamref name="T" />.
    /// </summary>
    /// <typeparam name="T">The type of the options.</typeparam>
    /// <param name="args">The arguments.</param>
    /// <param name="instance">The instance.</param>
    /// <returns>
    /// <c>true</c> if was converted successfully; otherwise,  <c>false</c>.
    /// </returns>
    /// <exception cref="ArgumentNullException">
    /// The exception that is thrown when a null reference (Nothing in Visual Basic) 
    /// is passed to a method that does not accept it as a valid argument.
    /// </exception>
    /// <exception cref="InvalidOperationException">
    /// The exception that is thrown when a method call is invalid for the object's current state.
    /// </exception>
    public Boolean ParseArguments<T>(IEnumerable<String> args, out T instance) {
      instance = Activator.CreateInstance<T>();
      return this.ParseArguments(args, instance);
    }

    /// <summary>
    /// Parses a string array of command line arguments constructing values in an instance of type <typeparamref name="T" />.
    /// </summary>
    /// <typeparam name="T">The type of the options.</typeparam>
    /// <param name="args">The arguments.</param>
    /// <param name="instance">The instance.</param>
    /// <returns>
    /// <c>true</c> if was converted successfully; otherwise,  <c>false</c>.
    /// </returns>
    /// <exception cref="ArgumentNullException">
    /// The exception that is thrown when a null reference (Nothing in Visual Basic) 
    /// is passed to a method that does not accept it as a valid argument.
    /// </exception>
    /// <exception cref="InvalidOperationException">
    /// The exception that is thrown when a method call is invalid for the object's current state.
    /// </exception>
    public Boolean ParseArguments<T>(IEnumerable<String> args, T instance) {
      if(args == null) {
        throw new ArgumentNullException(nameof(args));
      }

      if(Equals(instance, default(T))) {
        throw new ArgumentNullException(nameof(instance));
      }

      TypeResolver<T> typeResolver = new TypeResolver<T>(args.FirstOrDefault());
      Object options = typeResolver.GetOptionsObject(instance);

      if(options == null) {
        ReportUnknownVerb<T>();
        return false;
      }

      if(typeResolver.Properties == null) {
        throw new InvalidOperationException($"Type {typeof(T).Name} is not valid");
      }

      Validator validator = new Validator(typeResolver.Properties, args, options, this.Settings);

      if(validator.IsValid()) {
        return true;
      }

      this.ReportIssues(validator);
      return false;
    }

    private static void ReportUnknownVerb<T>() {
      Terminal.WriteLine("No verb was specified", ConsoleColor.Red);
      Terminal.WriteLine("Valid verbs:", ConsoleColor.Cyan);

      PropertyTypeCache.DefaultCache.Value.RetrieveAllProperties<T>(true).Select(x => AttributeCache.DefaultCache.Value.RetrieveOne<VerbOptionAttribute>(x)).Where(x => x != null).ToList().ForEach(x => Terminal.WriteLine(x.ToString(), ConsoleColor.Cyan));
    }

    private void ReportIssues(Validator validator) {
      if(this.Settings.WriteBanner) {
        Terminal.WriteWelcomeBanner();
      }

      IEnumerable<ArgumentOptionAttribute> options = validator.GetPropertiesOptions();

      foreach(ArgumentOptionAttribute option in options) {
        Terminal.WriteLine(String.Empty);

        // TODO: If Enum list values
        String shortName = String.IsNullOrWhiteSpace(option.ShortName) ? String.Empty : $"-{option.ShortName}";
        String longName = String.IsNullOrWhiteSpace(option.LongName) ? String.Empty : $"--{option.LongName}";
        String comma = String.IsNullOrWhiteSpace(shortName) || String.IsNullOrWhiteSpace(longName) ? String.Empty : ", ";
        String defaultValue = option.DefaultValue == null ? String.Empty : $"(Default: {option.DefaultValue}) ";

        Terminal.WriteLine($"  {shortName}{comma}{longName}\t\t{defaultValue}{option.HelpText}", ConsoleColor.Cyan);
      }

      Terminal.WriteLine(String.Empty);
      Terminal.WriteLine("  --help\t\tDisplay this help screen.", ConsoleColor.Cyan);

      if(validator.UnknownList.Any()) {
        Terminal.WriteLine($"Unknown arguments: {String.Join(", ", validator.UnknownList)}", ConsoleColor.Red);
      }

      if(validator.RequiredList.Any()) {
        Terminal.WriteLine($"Required arguments: {String.Join(", ", validator.RequiredList)}", ConsoleColor.Red);
      }
    }
  }
}