using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Diagnostics;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace CodeEditorComponent.Source
{
    public partial class CodeEditorComponent : Panel
    {
        public Options Options { get; } = new Options();

        public List<Line> Lines { get; } = new List<Line>();
        public int LineCount => Lines.Count;
        private Line CurrentLine => Lines[Caret.Y];

        private Caret Caret { get; set; } = new Caret();

        private float fontWidth, fontHeight;
        private int lineNumberBarWidth = 100;

        private float TotalLineHeight => fontHeight + Options.LineHeightMargin;

        VScrollBar vScrollBar = new VScrollBar();
        HScrollBar hScrollBar = new HScrollBar();

        float scrollX = 0f, scrollY = 0f;

        Label debugLabel = new Label();

        public CodeEditorComponent()
        {
            InitializeComponent();

            InitScrollBars();
            InitEvents();
            InitTest();
        }

        #region Initialization

        void InitEvents()
        {
            DoubleBuffered = true;

            Options.OnFontChanged += OnFontChanged;

            OnLineCountChanged += UpdateVScrollbar;
            OnLineModified += UpdateHScrollbar;

            OnCodeSet += UpdateVScrollbar;

            Timer timer = new Timer();
            timer.Interval = 10;
            timer.Enabled = true;
            timer.Tick += (sender, args) => Refresh();
        }

        void InitScrollBars()
        {
            vScrollBar.Parent = this;
            vScrollBar.Dock = DockStyle.Right;
            vScrollBar.LargeChange = 1;
            vScrollBar.ValueChanged += (sender, args) => scrollY = vScrollBar.Value;

            hScrollBar.Parent = this;
            hScrollBar.Dock = DockStyle.Bottom;
        }

        void InitTest()
        {
            debugLabel.Parent = this;
            debugLabel.Dock = DockStyle.Bottom;

            Options.Font = new Font("Consolas", 13, FontStyle.Regular);
            Code = @"import std.stdio;
void main() {
    writeln(""Hello world!"");
}

int soManyLinesOfCode() {
    int gay = 5;
    gay ^= 255;
    gay |= 5;
    return gay;
}

int soManyLinesOfCode() {
    int gay = 5;
    gay ^= 255;
    gay |= 5;
    return gay;
}

int soManyLinesOfCode() {
    int gay = 5;
    gay ^= 255;
    gay |= 5;
    return gay;
}

int soManyLinesOfCode() {
    int gay = 5;
    gay ^= 255;
    gay |= 5;
    return gay;
}
";
        }

        #endregion

        protected void OnFontChanged(Font font)
        {
            var size = CreateGraphics().MeasureString("0", font, 200, StringFormat.GenericTypographic);

            fontWidth = size.Width;
            fontHeight = size.Height;
        }

        protected override void OnSizeChanged(EventArgs e)
        {
            base.OnSizeChanged(e);
            Refresh();
        }

        public override Cursor Cursor => Cursors.IBeam;

        public string Code
        {
            get { return Lines.Select(l => l.Text).Aggregate((a, b) => $"{a}\r\n{b}"); }
            set
            {
                Lines.Clear();

                foreach (string line in value.Replace("\r\n", "\n").Split('\n'))
                    Lines.Add(new Line() { Text = line });

                OnCodeSet?.Invoke();

                Refresh();
            }
        }

        #region Code Editing

        void InsertTextAtCurrentPosition(string text)
        {
            InsertText(Caret.X, Caret.Y, text);
        }

        void InsertText(int x, int y, string text)
        {
            CurrentLine.Text = CurrentLine.Text.Insert(Caret.X, text);
            MoveCaret(text.Length, 0);
            OnLineModified?.Invoke(y);

            Refresh();
        }

        void RemoveTextAtPreviousPosition()
        {
            if (Caret.Y == 0 && Caret.X == 0)
                return;

            MoveCaret(-1, 0);
            RemoveText(Caret.X, Caret.Y, 1);
        }

        void RemoveText(int x, int y, int length)
        {
            if (x >= CurrentLine.Length)
            {
                if (LineCount <= 1)
                    return;

                CurrentLine.Text += Lines[y + 1].Text;
                Lines.RemoveAt(y + 1);

                OnLineCountChanged?.Invoke();
            }
            else
            {
                CurrentLine.Text = CurrentLine.Text.Remove(x, length <= CurrentLine.Length ? length : CurrentLine.Length);
            }

            OnLineModified?.Invoke(y);

            Refresh();
        }

        void InsertLineAtCurrentPosition()
        {
            InsertLine(Caret.X, Caret.Y);
        }

        void InsertLine(int x, int y)
        {
            Line newLine = new Line() { Text = CurrentLine.Text.Substring(x) };
            Lines.Insert(y + 1, newLine);
            if (CurrentLine.Length > x)
                CurrentLine.Text = CurrentLine.Text.Remove(x);
            MoveCaret(1, 0);

            OnLineModified?.Invoke(y);
            OnLineModified?.Invoke(y + 1);
            OnLineCountChanged?.Invoke();

            Refresh();
        }

        void InsertTabAtCurrentPosition()
        {
            InsertTab(Caret.X, Caret.Y);
        }

        void InsertTab(int x, int y)
        {
            InsertText(x, y, new string(' ', GetDistanceToNextIndent(x)));
        }

        int GetDistanceToNextIndent(int x)
        {
            return x % Options.TabToSpaces != 0 ? 4 - (x % Options.TabToSpaces) : Options.TabToSpaces;
        }

        #endregion

        void UpdateVScrollbar()
        {
            vScrollBar.Maximum = LineCount - 1;
        }

        void UpdateHScrollbar(int line)
        {
            // TODO: Horizontal scrollbar update
        }
    }
}