using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;

namespace StardewModdingAPI.Mods.ConsoleCommands.Framework.Commands
{
    /// <summary>Provides methods for parsing command-line arguments.</summary>
    internal class ArgumentParser : IReadOnlyList<string>
    {
        /*********
        ** Fields
        *********/
        /// <summary>The command name for errors.</summary>
        private readonly string CommandName;

        /// <summary>The arguments to parse.</summary>
        private readonly string[] Args;

        /// <summary>Writes messages to the console and log file.</summary>
        private readonly IMonitor Monitor;


        /*********
        ** Accessors
        *********/
        /// <summary>Get the number of arguments.</summary>
        public int Count => this.Args.Length;

        /// <summary>Get the argument at the specified index in the list.</summary>
        /// <param name="index">The zero-based index of the element to get.</param>
        public string this[int index] => this.Args[index];

        /// <summary>A method which parses a string argument into the given value.</summary>
        /// <typeparam name="T">The expected argument type.</typeparam>
        /// <param name="input">The argument to parse.</param>
        /// <param name="output">The parsed value.</param>
        /// <returns>Returns whether the argument was successfully parsed.</returns>
        public delegate bool ParseDelegate<T>(string input, out T output);


        /*********
        ** Public methods
        *********/
        /// <summary>Construct an instance.</summary>
        /// <param name="commandName">The command name for errors.</param>
        /// <param name="args">The arguments to parse.</param>
        /// <param name="monitor">Writes messages to the console and log file.</param>
        public ArgumentParser(string commandName, string[] args, IMonitor monitor)
        {
            this.CommandName = commandName;
            this.Args = args;
            this.Monitor = monitor;
        }

        /// <summary>Try to read a string argument.</summary>
        /// <param name="index">The argument index.</param>
        /// <param name="name">The argument name for error messages.</param>
        /// <param name="value">The parsed value.</param>
        /// <param name="required">Whether to show an error if the argument is missing.</param>
        /// <param name="oneOf">Require that the argument match one of the given values (case-insensitive).</param>
        public bool TryGet(int index, string name, out string value, bool required = true, string[] oneOf = null)
        {
            value = null;

            // validate
            if (this.Args.Length < index + 1)
            {
                if (required)
                    this.LogError($"Argument {index} ({name}) is required.");
                return false;
            }
            if (oneOf?.Any() == true && !oneOf.Contains(this.Args[index], StringComparer.InvariantCultureIgnoreCase))
            {
                this.LogError($"Argument {index} ({name}) must be one of {string.Join(", ", oneOf)}.");
                return false;
            }

            // get value
            value = this.Args[index];
            return true;
        }

        /// <summary>Try to read an integer argument.</summary>
        /// <param name="index">The argument index.</param>
        /// <param name="name">The argument name for error messages.</param>
        /// <param name="value">The parsed value.</param>
        /// <param name="required">Whether to show an error if the argument is missing.</param>
        /// <param name="min">The minimum value allowed.</param>
        /// <param name="max">The maximum value allowed.</param>
        public bool TryGetInt(int index, string name, out int value, bool required = true, int? min = null, int? max = null)
        {
            value = 0;

            // get argument
            if (!this.TryGet(index, name, out string raw, required))
                return false;

            // parse
            if (!int.TryParse(raw, out value))
            {
                this.LogIntFormatError(index, name, min, max);
                return false;
            }

            // validate
            if ((min.HasValue && value < min) || (max.HasValue && value > max))
            {
                this.LogIntFormatError(index, name, min, max);
                return false;
            }

            return true;
        }

        /// <summary>Returns an enumerator that iterates through the collection.</summary>
        /// <returns>An enumerator that can be used to iterate through the collection.</returns>
        public IEnumerator<string> GetEnumerator()
        {
            return ((IEnumerable<string>)this.Args).GetEnumerator();
        }

        /// <summary>Returns an enumerator that iterates through a collection.</summary>
        /// <returns>An <see cref="T:System.Collections.IEnumerator" /> object that can be used to iterate through the collection.</returns>
        IEnumerator IEnumerable.GetEnumerator()
        {
            return this.GetEnumerator();
        }


        /*********
        ** Private methods
        *********/
        /// <summary>Log a usage error.</summary>
        /// <param name="message">The message describing the error.</param>
        private void LogError(string message)
        {
            this.Monitor.Log($"{message} Type 'help {this.CommandName}' for usage.", LogLevel.Error);
        }

        /// <summary>Print an error for an invalid int argument.</summary>
        /// <param name="index">The argument index.</param>
        /// <param name="name">The argument name for error messages.</param>
        /// <param name="min">The minimum value allowed.</param>
        /// <param name="max">The maximum value allowed.</param>
        private void LogIntFormatError(int index, string name, int? min, int? max)
        {
            if (min.HasValue && max.HasValue)
                this.LogError($"Argument {index} ({name}) must be an integer between {min} and {max}.");
            else if (min.HasValue)
                this.LogError($"Argument {index} ({name}) must be an integer and at least {min}.");
            else if (max.HasValue)
                this.LogError($"Argument {index} ({name}) must be an integer and at most {max}.");
            else
                this.LogError($"Argument {index} ({name}) must be an integer.");
        }
    }
}