using System;
using System.Collections.Generic;
using osu.Framework;
using osu.Framework.Audio.Sample;
using osu.Framework.Graphics.Containers;
using osu.Framework.Graphics.Drawables;
using OpenTK.Graphics;
using osu.Framework.Graphics;
using OpenTK;
using osu.Framework.Cached;
using osu.Framework.Graphics.Transformations;
using OpenTK.Input;
using osu.Framework.Input;
using osu.Framework.Graphics.Sprites;
using osu.Framework.MathUtils;
using osu.Framework.Threading;

namespace osu.Game.Graphics.UserInterface
{
    internal class TextBox : MaskingContainer
    {
        private FlowContainer textFlow;
        private Box background;
        protected Box cursor;
        protected Container TextContainer;

        internal int? LengthLimit;
        internal bool ResetTextOnEdit;
        internal string textBeforeCommit;

        internal virtual bool AllowClipboardExport => true;

        protected virtual Color4 BackgroundCommit => new Color4(249, 90, 255, 200);
        protected virtual Color4 BackgroundFocused => new Color4(100, 100, 100, 255);
        protected virtual Color4 BackgroundUnfocused => new Color4(100, 100, 100, 120);

        public bool ReadOnly;

        TextInputSource textInput;

        internal delegate void OnCommitHandler(TextBox sender, bool newText);
        internal event OnCommitHandler OnCommit;
        public event OnCommitHandler OnChange;

        internal float SpaceWidth = 10;

        private Scheduler textUpdateScheduler = new Scheduler();

        public override void Load()
        {
            base.Load();

            Add(background = new Box()
            {
                Colour = BackgroundUnfocused,
                SizeMode = InheritMode.XY,
            });

            Add(TextContainer = new Container() { SizeMode = InheritMode.XY });

            textFlow = new FlowContainer()
            {
                Direction = FlowDirection.HorizontalOnly,
            };

            cursor = new Box()
            {
                Size = Vector2.One,
                Colour = Color4.Transparent,
                SizeMode = InheritMode.Y,
                Alpha = 0
            };

            TextContainer.Add(cursor);
            TextContainer.Add(textFlow);
        }

        private void resetSelection()
        {
            selectionStart = selectionEnd = text.Length;
            cursorAndLayout.Invalidate();
        }

        protected override void Dispose(bool disposing)
        {
            OnChange = null;
            OnCommit = null;

            UnbindInput();

            base.Dispose(disposing);
        }

        private float textContainerPosX;
        protected virtual float TextContainerIconOffset => 0;

        protected string TextAtLastLayout = string.Empty;

        protected override void UpdateLayout()
        {
            base.UpdateLayout();

            //have to run this after children flow
            cursorAndLayout.Refresh(delegate
            {
                textUpdateScheduler.Update();

                Vector2 cursorPos = Vector2.Zero;
                if (text.Length > 0)
                    cursorPos.X = getPositionAt(selectionLeft);

                float cursorPosEnd = getPositionAt(selectionEnd);

                float cursorWidth = 2;

                if (selectionLength > 0)
                    cursorWidth = getPositionAt(selectionRight) - cursorPos.X;

                float cursorRelativePositionInBox = (cursorPosEnd - textContainerPosX) / Width;

                //we only want to reposition the view when the cursor reaches near the extremities.
                if (cursorRelativePositionInBox < 0.1 || cursorRelativePositionInBox > 0.9)
                {
                    textContainerPosX = cursorPosEnd - Width / 2;
                }

                textContainerPosX = MathHelper.Clamp(textContainerPosX, 0, Math.Max(0, textFlow.Width - Width));

                TextContainer.MoveToX(TextContainerIconOffset - textContainerPosX, 300, EasingTypes.OutExpo);

                if (HasFocus)
                {
                    cursor.ClearTransformations();
                    cursor.MoveTo(cursorPos, 60, EasingTypes.Out);
                    cursor.ScaleTo(new Vector2(cursorWidth, 1), 60, EasingTypes.Out);

                    if (selectionLength > 0)
                    {
                        cursor.FadeTo(0.5f, 200, EasingTypes.Out);
                        cursor.FadeColour(new Color4(249, 90, 255, 255), 200, EasingTypes.Out);
                    }
                    else
                    {
                        cursor.FadeTo(0.5f, 200, EasingTypes.Out);
                        cursor.FadeColour(Color4.White, 200, EasingTypes.Out);
                        cursor.Transforms.Add(new TransformAlpha(Clock)
                        {
                            StartValue = 0.5f,
                            EndValue = 0.2f,
                            StartTime = Time,
                            EndTime = Time + 500,
                            Easing = EasingTypes.InOutSine,
                            LoopCount = -1,
                        });
                    }
                }

                OnChange?.Invoke(this, TextAtLastLayout != text);
                TextAtLastLayout = text;

                return cursorPos;
            });
        }

        private float getPositionAt(int index)
        {
            if (index > 0)
            {
                if (index < text.Length)
                    return textFlow.Children[index].Position.X + textFlow.Position.X;
                else
                    return textFlow.Children[index - 1].Position.X + textFlow.Children[index - 1].Size.X + textFlow.Padding.X + textFlow.Position.X;
            }
            else
                return 0;
        }

        private int getCharacterClosestTo(Vector2 pos)
        {
            pos = textFlow.GetLocalPosition(pos);

            int i = 0;
            foreach (Drawable d in textFlow.Children)
            {
                if (d.Position.X + d.Size.X / 2 > pos.X)
                    break;
                i++;
            }

            return i;
        }

        internal bool HandleLeftRightArrows = true;

        int selectionStart;
        int selectionEnd;

        int selectionLength => Math.Abs(selectionEnd - selectionStart);

        int selectionLeft => Math.Min(selectionStart, selectionEnd);
        int selectionRight => Math.Max(selectionStart, selectionEnd);

        Cached<Vector2> cursorAndLayout = new Cached<Vector2>();

        private void moveSelection(int offset, bool expand)
        {
            if (textInput?.ImeActive == true) return;

            int oldStart = selectionStart;
            int oldEnd = selectionEnd;

            if (expand)
                selectionEnd = MathHelper.Clamp(selectionEnd + offset, 0, text.Length);
            else
            {
                if (selectionLength > 0 && Math.Abs(offset) <= 1)
                {
                    //we don't want to move the location when "removing" an existing selection, just set the new location.
                    if (offset > 0)
                        selectionEnd = selectionStart = selectionRight;
                    else
                        selectionEnd = selectionStart = selectionLeft;
                }
                else
                    selectionEnd = selectionStart = MathHelper.Clamp((offset > 0 ? selectionRight : selectionLeft) + offset, 0, text.Length);
            }

            if (oldStart != selectionStart || oldEnd != selectionEnd)
            {
                Game.Audio.Sample.Get(@"Keyboard/key-movement")?.Play();
                cursorAndLayout.Invalidate();
            }
        }

        private bool removeCharacterOrSelection(bool sound = true)
        {
            if (text.Length == 0) return false;
            if (selectionLength == 0 && selectionLeft == 0) return false;

            int count = MathHelper.Clamp(selectionLength, 1, text.Length);
            int start = MathHelper.Clamp(selectionLength > 0 ? selectionLeft : selectionLeft - 1, 0, text.Length - count);

            if (count == 0) return false;

            if (sound)
                Game.Audio.Sample.Get(@"Keyboard/key-delete")?.Play();

            for (int i = 0; i < count; i++)
            {
                Drawable d = textFlow.Children[start];
                textFlow.Remove(d);

                TextContainer.Add(d);
                d.FadeOut(200);
                d.MoveToY(d.Size.Y, 200, EasingTypes.InExpo);
                d.Expire();
            }
            text = text.Remove(start, count);

            if (selectionLength > 0)
                selectionStart = selectionEnd = selectionLeft;
            else
                selectionStart = selectionEnd = selectionLeft - 1;

            cursorAndLayout.Invalidate();
            return true;
        }

        protected virtual Drawable AddCharacterToFlow(char c)
        {
            for (int i = selectionLeft; i < text.Length; i++)
                textFlow.Children[i].Depth = i + 1;

            Drawable ch;

            if (char.IsWhiteSpace(c))
            {
                float width = SpaceWidth / 2;

                switch ((int)c)
                {
                    case 0x3000: //double-width space
                        width = SpaceWidth;
                        break;
                }

                textFlow.Add(ch = new Container()
                {
                    SizeMode = InheritMode.None,
                    Size = new Vector2(width, SpaceWidth),
                    Depth = selectionLeft
                });
            }
            else
            {
                textFlow.Add(ch = new SpriteText()
                {
                    Text = c.ToString(),
                    Depth = selectionLeft
                });
            }

            return ch;
        }

        /// <summary>
        /// Insert an arbitrary string into the text at the current position.
        /// </summary>
        /// <param name="text"></param>
        private void insertString(string text)
        {
            foreach (char c in text)
            {
                if (char.IsControl(c)) continue;
                addCharacter(c);
            }
        }

        private Drawable addCharacter(char c)
        {
            if (selectionLength > 0)
                removeCharacterOrSelection();

            if (text.Length + 1 > LengthLimit)
            {
                if (background.Alpha > 0)
                    background.FlashColour(Color4.Red, 200);
                else
                    textFlow.FlashColour(Color4.Red, 200);
                return null;
            }

            Drawable ch = AddCharacterToFlow(c);

            ch.Position = new Vector2(0, SpaceWidth);
            ch.MoveToY(0, 200, EasingTypes.OutExpo);

            text = text.Insert(selectionLeft, c.ToString());
            selectionStart = selectionEnd = selectionLeft + 1;

            cursorAndLayout.Invalidate();

            return ch;
        }

        private string text;
        internal virtual string Text
        {
            get
            {
                return text;
            }
            set
            {
                if (value == text)
                    return;

                textUpdateScheduler.Add(delegate
                {
                    int startBefore = selectionStart;
                    selectionStart = selectionEnd = 0;
                    textFlow?.Clear();
                    text = string.Empty;

                    foreach (char c in value)
                        addCharacter(c);

                    selectionStart = MathHelper.Clamp(startBefore, 0, text.Length);
                }, true);

                cursorAndLayout.Invalidate();
            }
        }

        public string SelectedText => selectionLength > 0 ? Text.Substring(selectionLeft, selectionLength) : string.Empty;

        protected override bool OnKeyDown(InputState state, KeyDownEventArgs args)
        {
            if (!HasFocus)
                return false;

            if (textInput?.ImeActive == true) return true;

            switch (args.Key)
            {
                case Key.Tab:
                    return false;
                case Key.End:
                    moveSelection(text.Length, state.Keyboard.ShiftPressed);
                    return true;
                case Key.Home:
                    moveSelection(-text.Length, state.Keyboard.ShiftPressed);
                    return true;
                case Key.Left:
                    {
                        if (!HandleLeftRightArrows) return false;

                        if (selectionEnd == 0) return true;

                        int amount = 1;
                        if (state.Keyboard.ControlPressed)
                        {
                            int lastSpace = text.LastIndexOf(' ', Math.Max(0, selectionEnd - 2));
                            if (lastSpace >= 0)
                                amount = selectionEnd - lastSpace - 1;
                            else
                                amount = selectionEnd;
                        }

                        moveSelection(-amount, state.Keyboard.ShiftPressed);
                    }
                    return true;
                case Key.Right:
                    {
                        if (!HandleLeftRightArrows) return false;

                        if (selectionEnd == text.Length) return true;

                        int amount = 1;
                        if (state.Keyboard.ControlPressed)
                        {
                            int nextSpace = text.IndexOf(' ', selectionEnd + 1);
                            if (nextSpace >= 0)
                                amount = nextSpace - selectionEnd;
                            else
                                amount = text.Length - selectionEnd;
                        }

                        moveSelection(amount, state.Keyboard.ShiftPressed);
                    }

                    return true;
                case Key.Enter:
                    TriggerFocusLost(state);
                    return true;
                case Key.Delete:
                    if (selectionLength == 0)
                    {
                        if (text.Length == selectionStart)
                            return true;

                        if (state.Keyboard.ControlPressed)
                        {
                            int spacePos = selectionStart;
                            while (text[spacePos] == ' ' && spacePos < text.Length)
                                spacePos++;

                            spacePos = MathHelper.Clamp(text.IndexOf(' ', spacePos), 0, text.Length);
                            selectionEnd = spacePos;

                            if (selectionStart == 0 && spacePos == 0)
                                selectionEnd = text.Length;

                            if (selectionLength == 0)
                                return true;
                        }
                        else
                        {
                            //we're deleting in front of the cursor, so move the cursor forward once first
                            selectionStart = selectionEnd = selectionStart + 1;
                        }
                    }

                    removeCharacterOrSelection();
                    return true;
                case Key.Back:
                    if (selectionLength == 0 && state.Keyboard.ControlPressed)
                    {
                        int spacePos = selectionLeft >= 2 ? Math.Max(0, text.LastIndexOf(' ', selectionLeft - 2) + 1) : 0;
                        selectionStart = spacePos;
                    }

                    removeCharacterOrSelection();
                    return true;
            }

            if (state.Keyboard.ControlPressed)
            {
                //handling of function keys
                switch (args.Key)
                {
                    case Key.A:
                        selectionStart = 0;
                        selectionEnd = text.Length;
                        cursorAndLayout.Invalidate();
                        return true;
                    case Key.C:
                        if (string.IsNullOrEmpty(SelectedText) || !AllowClipboardExport) return true;
                        //System.Windows.Forms.Clipboard.SetText(SelectedText);
                        return true;
                    case Key.X:
                        if (string.IsNullOrEmpty(SelectedText)) return true;

                        //if (AllowClipboardExport)
                        //    System.Windows.Forms.Clipboard.SetText(SelectedText);
                        removeCharacterOrSelection();
                        return true;
                    case Key.V:
                        //the text is pasted into the hidden textbox, so we don't need any direct clipboard interaction here.
                        //insertString(textInput.GetPendingText());
                        return true;
                }

                return false;
            }

            string str = textInput.GetPendingText();
            if (!string.IsNullOrEmpty(str))
            {
                if (state.Keyboard.ShiftPressed)
                    Game.Audio.Sample.Get(@"Keyboard/key-caps")?.Play();
                else
                    Game.Audio.Sample.Get($@"Keyboard/key-press-{RNG.Next(1, 5)}")?.Play();
                insertString(str);

                return true;
            }

            return false;
        }

        protected override bool OnDrag(InputState state)
        {
            //if (textInput?.ImeActive == true) return true;

            if (text.Length == 0) return true;

            selectionEnd = getCharacterClosestTo(state.Mouse.Position);
            if (selectionLength > 0)
                TriggerFocus();

            cursorAndLayout.Invalidate();
            return true;
        }

        protected override bool OnDragStart(InputState state)
        {
            //need to handle this so we get onDrag events.
            return true;
        }

        protected override bool OnDoubleClick(InputState state)
        {
            if (textInput?.ImeActive == true) return true;

            if (text.Length == 0) return true;

            int hover = Math.Min(text.Length - 1, getCharacterClosestTo(state.Mouse.Position));

            int lastSpace = text.LastIndexOf(' ', hover);
            int nextSpace = text.IndexOf(' ', hover);

            selectionStart = lastSpace >= 0 ? lastSpace + 1 : 0;
            selectionEnd = nextSpace >= 0 ? nextSpace : text.Length;
            cursorAndLayout.Invalidate();
            return true;
        }

        protected override bool OnMouseDown(InputState state, MouseDownEventArgs args)
        {
            if (textInput?.ImeActive == true) return true;

            selectionStart = selectionEnd = getCharacterClosestTo(state.Mouse.Position);

            cursorAndLayout.Invalidate();

            return true;
        }

        protected override void OnFocusLost(InputState state)
        {
            UnbindInput();

            cursor.ClearTransformations();
            cursor.FadeOut(200);

            if (state.Keyboard.Keys.Contains(Key.Enter))
            {
                background.Colour = BackgroundUnfocused;
                background.ClearTransformations();
                background.FlashColour(BackgroundCommit, 400);

                Game.Audio.Sample.Get(@"Keyboard/key-confirm")?.Play();
                OnCommit?.Invoke(this, true);
            }
            else
            {
                background.ClearTransformations();
                background.FadeColour(BackgroundUnfocused, 200, EasingTypes.OutExpo);
            }

            cursorAndLayout.Invalidate();
        }

        protected override bool OnFocus(InputState state)
        {
            if (ReadOnly) return false;

            BindInput();

            textBeforeCommit = Text;
            if (ResetTextOnEdit)
                Text = string.Empty;

            background.ClearTransformations();
            background.FadeColour(BackgroundFocused, 200, EasingTypes.Out);

            cursorAndLayout.Invalidate();
            return true;
        }

        #region Native TextBox handling (winform specific)
        protected void UnbindInput()
        {
            textInput?.Deactivate();
        }

        protected void BindInput()
        {
            if (textInput == null)
            {
                textInput = Game.Host.TextInput;
                textInput.OnNewImeComposition += onImeComposition;
                textInput.OnNewImeResult += onImeResult;
            }

            textInput.Activate();
        }

        private void onImeResult(string s)
        {
            //we only succeeded if there is pending data in the textbox
            if (imeDrawables.Count > 0)
            {
                Game.Audio.Sample.Get($@"Keyboard/key-confirm")?.Play();

                foreach (Drawable d in imeDrawables)
                {
                    d.Colour = Color4.White;
                    d.FadeTo(1, 200, EasingTypes.Out);
                }
            }

            imeDrawables.Clear();
        }

        List<Drawable> imeDrawables = new List<Drawable>();

        private void onImeComposition(string s)
        {
            //search for unchanged characters..
            int matchCount = 0;
            bool matching = true;
            bool didDelete = false;

            int searchStart = text.Length - imeDrawables.Count;

            //we want to keep processing to the end of the longest string (the current displayed or the new composition).
            int maxLength = Math.Max(imeDrawables.Count, s.Length);

            for (int i = 0; i < maxLength; i++)
            {
                if (matching && searchStart + i < text.Length && i < s.Length && text[searchStart + i] == s[i])
                {
                    matchCount = i + 1;
                    continue;
                }

                matching = false;

                if (matchCount < imeDrawables.Count)
                {
                    //if we are no longer matching, we want to remove all further characters.
                    removeCharacterOrSelection(false);
                    imeDrawables.RemoveAt(matchCount);
                    didDelete = true;
                }
            }

            if (matchCount == s.Length)
            {
                //in the case of backspacing (or a NOP), we can exit early here.
                if (didDelete)
                    Game.Audio.Sample.Get($@"Keyboard/key-delete")?.Play();
                return;
            }

            //add any new or changed characters
            for (int i = matchCount; i < s.Length; i++)
            {
                Drawable dr = addCharacter(s[i]);
                if (dr != null)
                {
                    dr.Colour = Color4.Aqua;
                    dr.Alpha = 0.6f;
                    imeDrawables.Add(dr);
                }
            }

            Game.Audio.Sample.Get($@"Keyboard/key-press-{RNG.Next(1, 5)}")?.Play();
        }
        #endregion
    }
}