using System;
using Cairo;
using System.Text.RegularExpressions;
using System.Resources;
using System.Collections.Generic;

namespace SBRL.SimpleTurtle
{
	public class Area
	{
		public double X;
		public double Y;
		public double Width;
		public double Height;

		public Area(double inX, double inY, double inWidth, double inHeight)
		{
			X = inX;
			Y = inY;
			Width = inWidth;
			Height = inHeight;
		}
	}
	public class Turtle
	{
		private bool strictMode = false;
		private string commandQueue;

		private PointD position;
		private Area bounds;
		private double heading;
		private double headingStep;
		public double HeadingStep
		{
			get { return headingStep; }
			set { headingStep = value; }
		}
		private double movementStep ;
		public double MovementStep
		{
			get { return movementStep; }
			set { movementStep = value; }
		}

		public Turtle ()
		{
			Reset();
		}

		public void ApplyDefinitions(Dictionary<string, string> definitions)
		{
			foreach(KeyValuePair<string, string> definition in definitions)
			{
				switch(definition.Key.ToLower())
				{
					case "angle":
						HeadingStep = double.Parse(definition.Value);
						break;
				}
			}
		}

		public bool Commands(string commandText)
		{
			// Remove all whitespace
			commandText = Regex.Replace(commandText, @"\s+", "");
			commandText = commandText.Replace("h", "f");

			string okCommands = "f+-";

			foreach(char ch in commandText)
			{
				if(okCommands.Contains(ch.ToString()))
				{
					switch(ch)
					{
						case 'f':
							Forwards();
							break;
						case '+':
							Turn(false);
							break;
						case '-':
							Turn(true);
							break;
						default:
							if (strictMode) {
								Console.WriteLine("The unexpected character '{0}' slipped through the net!", ch);
								return false;
							}
							break;
					}
				}
				else if(strictMode)
				{
					Console.Error.WriteLine("Error: unexpected character '{0}'", ch);
					return false;
				}
			}
			commandQueue += commandText;
			return true;
		}

		public void Draw(string filename, bool reset = true)
		{
			ImageSurface canvas = new ImageSurface(Format.ARGB32, (int)Math.Ceiling(bounds.Width + 10), (int)Math.Ceiling(bounds.Height + 10));
			Context context = new Context(canvas);
			position = new PointD(-bounds.X + 5, -bounds.Y + 5);
			heading = 0;

			context.LineWidth = 3;
			context.MoveTo(position);
			foreach(char ch in commandQueue)
			{
				switch(ch)
				{
					case 'f':
						PointD newPosition = new PointD(
							position.X + movementStep * Math.Sin(heading),
							position.Y + movementStep * Math.Cos(heading)
						);
						context.LineTo(newPosition);
						position = newPosition;
						break;
					case '+':
						heading += headingStep;
						break;
					case '-':
						heading -= headingStep;
						break;
				}
			}

			context.Stroke();
			canvas.WriteToPng(string.Format(filename));
			context.Dispose();
			canvas.Dispose();
			if(reset)
				Reset();
		}

		public void Forwards()
		{
			PointD newPosition = new PointD(
				position.X + MovementStep * Math.Sin(heading),
				position.Y + MovementStep * Math.Cos(heading)
			);

			if (newPosition.X > bounds.X + bounds.Width)
				bounds.Width += newPosition.X - position.X;
			if (newPosition.Y > bounds.Y + bounds.Height)
				bounds.Height += newPosition.Y - position.Y;
			if (newPosition.X < bounds.X)
			{
				bounds.X = newPosition.X;
				bounds.Width += position.X - newPosition.X;
			}
			if (newPosition.Y < bounds.Y)
			{
				bounds.Y = newPosition.Y;
				bounds.Height += position.Y - newPosition.Y;
			}

			position = newPosition;
		}

		public void Turn(bool anticlockwise = false)
		{
			if (!anticlockwise)
				heading += HeadingStep;
			else
				heading -= HeadingStep;
		}

		public void Reset()
		{
			commandQueue = string.Empty;
			position = new PointD(0, 0);
			bounds = new Area(position.X, position.Y, 1, 1);
			heading = 0;
			headingStep = Math.PI / 2;
			movementStep = 25;
		}
	}
}