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/*
Two types of CLI arguments:
---------------------------

1. Full arguments
    - listed explicitly (eg. "--arg1")
    - usually a full word
    - can contain spaces represented as "--project-name"

2. Shortened arguments
    - listed implicitly version (eg. "-a")
    - usually a single letter, interpreted as such


Two types of CLI values:
------------------------

1. String inputs
    a) Single character (char)
    b) Single word (Word type)
    c) Multiple words (Sentence type)

2. Number inputs
    a) Single digit (Digit type)
    b) Digit string (Number type)
*/

using Builtins;

namespace CommandLine
{
    /// <summary>
    /// A struct representing a command-line argument.
    /// 
    /// This contains two properties, a name and a list of aliases
    /// that can be used instead of the name, and serves as a way
    /// to represent a command-line argument in a centralised manner.
    /// </summary>
    public struct Argument
    {
        private readonly string _name;
        private readonly string[] _aliases;

        public string Name { get { return _name; } }
        public string[] Aliases { get { return _aliases; } }

        /// <summary>
        /// Create an Argument instance with only a name and no aliases.
        /// </summary>
        /// <param name="name"></param>
        public Argument(string name)
        {
            _name = name;
            _aliases = [];
        }

        /// <summary>
        /// Create an Argument instance with a name and an array of aliases.<para/>
        /// 
        /// These aliases will be used when comparing between two arguments
        /// and serves as a way to tell if arguments are repeated or not.
        /// </summary>
        /// <param name="name"></param>
        /// <param name="aliases"></param>
        public Argument(string name, string[] aliases)
        {
            _name = name;
            _aliases = aliases;
        }

        /// <summary>
        /// Create an Argument instance with a name and a single alias.<para/>
        /// 
        /// Thhis alias will be used when comparing between two arguments
        /// and serves as a way to tell if arguments are repeated or not.
        /// </summary>
        /// <param name="name"></param>
        /// <param name="alias"></param>
        public Argument(string name, string alias)
        {
            _name = name;
            _aliases = [alias];
        }

        public override bool Equals(object? obj)
        {
            if (obj is null) return false;

            if (obj is string) return Name == obj.ToString();

            Argument other = (Argument)obj;

            return Name == other.Name
                || other.Aliases.Contains(Name)
                || Aliases.Contains(other.Name);
        }

        public static implicit operator string(Argument arg) => arg.Name;
        public static implicit operator Argument(string str) => new(str);

        public override int GetHashCode() => Name.GetHashCode() ^ Aliases.GetHashCode();

        public override string ToString() => $"Argument({_name}{(_aliases.Length > 0 ? $", aliases = [{string.Join(", ", _aliases)}]" : "")})";
    }

    public abstract class Command
    {
        private readonly string _name;
        private readonly Argument[] _arguments;
        private readonly string? _doc;

        public string Name { get { return _name; } }
        public Argument[] Arguments { get { return _arguments; } }
        public string? Docstring { get { return _doc; } }
        public Argument[] ReturnedArguments { get; set; }

        public static List<Command> CreatedCommands { get {
            List<Command> names = [];

            foreach (var asm in AppDomain.CurrentDomain.GetAssemblies())
            {
                foreach (var type in asm.GetTypes())
                {
                    if (type.BaseType == typeof(Command))
                    {
                        var inst = Activator.CreateInstance(type);

                        if (inst == null) throw new ArgumentNullException("Null error when searching for commands.");

                        names.Add((Command)inst);
                    }
                }
            }

            return names;
        } }

        public Command(string name)
        {
            _name = name;
            _arguments = [name];
            _doc = null;
           
            ReturnedArguments = [];
        }

        public Command(string name, string docstring)
        {
            _name = name;
            _arguments = [name];
            _doc = docstring.Trim().Replace("\n", "").Replace("\n\n", "\n");

            ReturnedArguments = [];
        }
        
        public Command(string name, Argument[] arguments)
        {
            if (name == "help") throw new Exception("command names cannot be called 'help'.");
            
            _name = name;
            _arguments = [name, .. arguments];
            _doc = null;

            ReturnedArguments = [];
        }

        public Command(string name, Argument[] arguments, string docstring)
        {
            if (name == "help") throw new Exception("command names cannot be called 'help'.");
            
            _name = name;
            _arguments = [name, .. arguments];
            _doc = docstring.Trim().Replace("\n", "").Replace("\n\n", "\n");

            ReturnedArguments = [];
        }

        public virtual void Callback()
        {
            throw new NotImplementedException("this method must be overrided in a subclass.");
        }
    }

    public struct CLI
    {
        public Command[] ValidCommands { get; set; }

        public CLI(Command[] validCommands)
        {
            ValidCommands = validCommands;
        }

        public Dictionary<string, string> ArgParser(string[] argsFromCLI, Argument[] validArguments)
        {
            if (validArguments
                    .Where(x => x.Name == "help")
                    .ToList()
                    .Count == 1
                && validArguments.Length > 1)
            {
                validArguments = [new Argument("help_args")];
            }

            List<int> validArgIndexes = Enumerable
                .Range(0, argsFromCLI.Length)
                .Where(n => validArguments.Contains(argsFromCLI[n]))
                .ToList();

            validArgIndexes.Add(argsFromCLI.Length);

            Dictionary<string, string> convertedArgs = [];

            for (int x = 0; x < validArgIndexes.Count - 1; x++)
            {
                int firstIndex  = validArgIndexes[x];
                int secondIndex = validArgIndexes[x + 1];

                string first = argsFromCLI[firstIndex];
                string other = string.Join(" ", argsFromCLI[(firstIndex + 1) .. secondIndex]);

                convertedArgs.Add(first, other);
            }

            return convertedArgs;
        }

        public Command? SingleArgParser(string[] argsFromCLI)
        {
            string[] validArguments = ValidCommands.Select(x => x.Name).ToArray();

            List<int> validArgIndexes = Enumerable
                .Range(0, argsFromCLI.Length)
                .Where(n => validArguments.Contains(argsFromCLI[n]))
                .ToList();
            
            if (validArgIndexes.Count != 2) return null;

            int argIndex = validArgIndexes[0];

            string other = string.Join(' ', argsFromCLI[(argIndex + 1) .. (argsFromCLI.Length - argIndex)]);

            Command command = ValidCommands.Where(x => x.Name == argsFromCLI[argIndex]).First();

            command.ReturnedArguments = [other];

            return command;
        }
    }
}

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using CommandLine;

namespace Builtins
{
    // Echo command
    class EchoCommand : Command
    {
        public EchoCommand()
            : base("echo", docstring:
                """
                A simple echo command that repeats back whatever the user sends.

                If the first argument is a number, it will be treated as the number of times
                to repeat the following sequence of characters, joined by a space.

                Usage
                -----
                >>> echo hello world
                hello world

                >>> echo 3 hi
                hi hi hi
                """
            )
        {
        }

        public override void Callback()
        {
            string echoString = ReturnedArguments[0];
            string[] echoStringParts = echoString.Split(' ');

            if (echoStringParts.Length == 1)
            {
                Console.WriteLine(echoString);
                return;
            }
            
            string firstEchoWord  = echoStringParts[0];
            string restOfEchoWord = string.Join(" ", echoStringParts[1 .. echoStringParts.Length]);

            if (int.TryParse(firstEchoWord, out int count))
            {
                Console.WriteLine(string.Join(" ", Enumerable.Range(0, count + 1).Select(_ => restOfEchoWord)));
            }
            else
            {
                Console.WriteLine(echoString);
            }
        }
    }

    // Close command
    class CloseCommand : Command
    {
        public CloseCommand()
            : base("close", docstring:
                """
                A simple close command that stops the process entirely and closes the window.

                Usage
                -----
                >>> close
                """)
        {
        }

        public override void Callback()
        {
            Environment.Exit(0);
        }
    }

    // Help command
    class HelpCommand : Command
    {
        public HelpCommand()
            : base("help")
        {
        }

        public override void Callback()
        {
            // Get what the user queried with the help command
            string query = ReturnedArguments[0];

            // Get all the commands subclassing command
            List<Command> search = CreatedCommands.Where(cmd => cmd.Name == query).ToList();

            if (search.Count == 0)
            {
                Console.WriteLine($"The search for command '{query}' yielded no results.");
                return;
            }

            Command command = search[0];

            string title = $"Help on command '{command}':";

            Console.WriteLine($"{title}\n{new string('-', title.Length)}\n{command.Docstring}\n{new string('-', title.Length)}");
        }
    }
}

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using CommandLine;
using Builtins;

class Program
{
    static void RunCLI()
    {
        Console.Title = "Example CLI";
        
        string? input;
        // Dictionary<string, string>? args;
        Command? command;

        HelpCommand help = new();
        EchoCommand echo = new();
        CloseCommand close = new();
        
        while (true)
        {
            Console.Write(">>> ");
            input = Console.ReadLine();

            if (input == null)
            {
                Console.WriteLine();
                continue;
            }

            CLI cli = new([help, echo, close]);
            command = cli.SingleArgParser(input.Split(' '));

            if (command == null)
            {
                Console.WriteLine("Error occured when attempting to parse console input.");
                continue;
            }

            command.Callback();
        }
    }

    static void Main()
    {
        // RunCLI();
        Console.WriteLine(new EchoCommand().Docstring);
    }
}