using UnityEngine;
using UnityEngine.UI;
using UnityEngine.EventSystems;
using System;
using System.Collections.Generic;
using UnityEngine.Events;

namespace UnityConsole
{
    /// <summary>
    /// The interactive front-end of the console.
    /// </summary>
    [DisallowMultipleComponent]
    [RequireComponent(typeof(ConsoleController))]
    public class ConsoleUI : MonoBehaviour, IScrollHandler
    {
        public event Action<bool> onToggleConsole;
        public event Action<string> onSubmitCommand;
        public event Action onClearConsole;

        public Scrollbar scrollbar;
        public Text outputText;
        public ScrollRect outputArea;
        public InputField inputField;

        /// <summary>
        /// Indicates whether the console is currently open or close.
        /// </summary>
        public bool isConsoleOpen => enabled;

        void Awake()
        {
            inputField.onEndEdit.AddListener(OnSubmit);
            Show(false);
        }

        /// <summary>
        /// Opens or closes the console.
        /// </summary>
        public void ToggleConsole()
        {
            ClearInput();
            enabled = !enabled;
        }

        /// <summary>
        /// Opens the console.
        /// </summary>
        public void OpenConsole()
        {
            enabled = true;
        }

        /// <summary>
        /// Closes the console.
        /// </summary>
        public void CloseConsole()
        {
            enabled = false;
        }

        void OnEnable()
        {
            OnToggle(true);
        }

        void OnDisable()
        {
            OnToggle(false);
        }

        private void OnToggle(bool open)
        {
            Show(open);

            if (open)
            {
                inputField.ActivateInputField();
            }
            else
            {
                ClearInput();
            }

            onToggleConsole?.Invoke(open);
        }

        private void Show(bool show)
        {
            inputField.gameObject.SetActive(show);
            outputArea.gameObject.SetActive(show);
            scrollbar.gameObject.SetActive(show);
        }

        /// <summary>
        /// What to do when the user wants to submit a command.
        /// </summary>
        public void OnSubmit(string input)
        {
            if (EventSystem.current.alreadySelecting)
            {
                // if user selected something else, don't treat as a submit
                return;
            }

            input = input.Replace('\n', ' ').Replace('\r', ' ');

            if (input.Length > 0)
            {
                onSubmitCommand?.Invoke(input);
                scrollbar.value = 0;
                ClearInput();
            }

            inputField.ActivateInputField();
        }

        /// <summary>
        /// What to do when the user uses the scrollwheel while hovering the console input.
        /// </summary>
        public void OnScroll(PointerEventData eventData)
        {
            scrollbar.value += 0.08f * eventData.scrollDelta.y;
        }

        /// <summary>
        /// Displays the given message as a new entry in the console output.
        /// </summary>
        public void AddNewOutputLine(string line)
        {
            int length = outputText.text.Length;
            if (length > 8192)
                outputText.text = outputText.text.Substring(length - 8192);

            outputText.text += Environment.NewLine + line;
        }

        /// <summary>
        /// Clears the console output.
        /// </summary>
        public void ClearOutput()
        {
            outputText.text = "";
            outputText.SetLayoutDirty();
            onClearConsole?.Invoke();
        }

        /// <summary>
        /// Clears the console input.
        /// </summary>
        public void ClearInput()
        {
            SetInputText("");
        }

        /// <summary>
        /// Writes the given string into the console input, ready to be user submitted.
        /// </summary>
        public void SetInputText(string input)
        {
            inputField.MoveTextStart(false);
            inputField.text = input;
            inputField.MoveTextEnd(false);
            inputField.caretPosition = inputField.text.Length;
        }

        public void TabComplete()
        {
            List<string> commandsPrefix = ConsoleCommandsDatabase.CommandsMatchingPrefix(inputField.text);
            List<string> commandsContaining = ConsoleCommandsDatabase.CommandsContainingStrings(
                new string[]
                {
                    inputField.text
                }, true);

            if (commandsPrefix.Count == 0)
            {
                if (commandsContaining.Count == 0)
                {
                    AddNewOutputLine("No command contains \"" + inputField.text + "\"");
                    return;
                }

                commandsPrefix = commandsContaining;
                commandsContaining.Clear();
            }

            if (commandsPrefix.Count == 1)
            {
                SetInputText(commandsPrefix[0]);
            }
            else
            {
                string prefix = LongestCommonPrefix(commandsPrefix);
                if (string.Equals(inputField.text, prefix, StringComparison.OrdinalIgnoreCase))
                {
                    AddNewOutputLine("<b>Did you mean...</b>");
                    commandsPrefix.Sort();
                    foreach (var cmd in commandsPrefix)
                    {
                        AddNewOutputLine("    " + cmd);
                    }

                    if (commandsContaining.Count != 0)
                    {
                        AddNewOutputLine("<b>Or others containing this term...</b>");
                        commandsContaining.Sort();
                        foreach (var cmd in commandsContaining)
                        {
                            AddNewOutputLine("    " + cmd);
                        }
                    }
                }
                else
                {
                    SetInputText(prefix);
                }
            }
        }

        private static string LongestCommonPrefix(List<string> strs)
        {
            if (strs == null || strs.Count == 0)
            {
                return "";
            }

            int minLength = int.MaxValue;
            foreach (var str in strs)
            {
                minLength = Math.Min(minLength, str.Length);
            }

            int left = 1;
            int right = minLength;
            while (left <= right)
            {
                int mid = (left + right) / 2;
                if (IsCommonPrefix(strs, mid))
                {
                    left = mid + 1;
                }
                else
                {
                    right = mid - 1;
                }
            }

            return strs[0].Substring(0, (left + right) / 2);
        }

        private static bool IsCommonPrefix(List<string> strs, int len)
        {
            string str = strs[0].Substring(0, len);
            for (int index = 1; index < strs.Count; ++index)
            {
                if (!strs[index].StartsWith(str))
                {
                    return false;
                }
            }

            return true;
        }
    }
}