using UnityEngine;
using System.Collections;

public static class GuiHelper
{
    // The texture used by DrawLine(Color)
    private static Texture2D _coloredLineTexture;

    // The color used by DrawLine(Color)
    private static Color _coloredLineColor;

    /// <summary>
    /// Draw a line between two points with the specified color and a thickness of 1
    /// </summary>
    /// <param name="lineStart">The start of the line</param>
    /// <param name="lineEnd">The end of the line</param>
    /// <param name="color">The color of the line</param>
    public static void DrawLine(Vector2 lineStart, Vector2 lineEnd, Color color)
    {
        if ((lineStart.x == lineEnd.x) && (lineStart.y == lineEnd.y))
            return;
        DrawLine(lineStart, lineEnd, color, 1);
    }

    /// <summary>
    /// Draw a line between two points with the specified color and thickness
    /// Inspired by code posted by Sylvan
    /// http://forum.unity3d.com/threads/17066-How-to-draw-a-GUI-2D-quot-line-quot?p=407005&viewfull=1#post407005
    /// </summary>
    /// <param name="lineStart">The start of the line</param>
    /// <param name="lineEnd">The end of the line</param>
    /// <param name="color">The color of the line</param>
    /// <param name="thickness">The thickness of the line</param>
    public static void DrawLine(Vector2 lineStart, Vector2 lineEnd, Color color, int thickness)
    {
        if ((lineStart.x == lineEnd.x) && (lineStart.y == lineEnd.y))
            return;
        if (_coloredLineTexture == null || _coloredLineColor != color)
        {
            _coloredLineColor = color;
            _coloredLineTexture = new Texture2D(1, 1);
            _coloredLineTexture.SetPixel(0, 0, _coloredLineColor);
            _coloredLineTexture.wrapMode = TextureWrapMode.Repeat;
            _coloredLineTexture.Apply();
        }
        DrawLineStretched(lineStart, lineEnd, _coloredLineTexture, thickness);
    }

    /// <summary>
    /// Draw a line between two points with the specified texture and thickness.
    /// The texture will be stretched to fill the drawing rectangle.
    /// Inspired by code posted by Sylvan
    /// http://forum.unity3d.com/threads/17066-How-to-draw-a-GUI-2D-quot-line-quot?p=407005&viewfull=1#post407005
    /// </summary>
    /// <param name="lineStart">The start of the line</param>
    /// <param name="lineEnd">The end of the line</param>
    /// <param name="texture">The texture of the line</param>
    /// <param name="thickness">The thickness of the line</param>
    public static void DrawLineStretched(Vector2 lineStart, Vector2 lineEnd, Texture2D texture, int thickness)
    {
        if ((lineStart.x == lineEnd.x) && (lineStart.y == lineEnd.y))
            return;
        Vector2 lineVector = lineEnd - lineStart;
        float angle = Mathf.Rad2Deg * Mathf.Atan(lineVector.y / lineVector.x);
        if (lineVector.x < 0)
        {
            angle += 180;
        }

        if (thickness < 1)
        {
            thickness = 1;
        }

        // The center of the line will always be at the center
        // regardless of the thickness.
        int thicknessOffset = (int)Mathf.Ceil(thickness / 2);

        GUIUtility.RotateAroundPivot(angle,
                                     lineStart);
        GUI.DrawTexture(new Rect(lineStart.x,
                                 lineStart.y - thicknessOffset,
                                 lineVector.magnitude,
                                 thickness),
                        texture);
        GUIUtility.RotateAroundPivot(-angle, lineStart);
    }

    /// <summary>
    /// Draw a line between two points with the specified texture and a thickness of 1
    /// The texture will be repeated to fill the drawing rectangle.
    /// </summary>
    /// <param name="lineStart">The start of the line</param>
    /// <param name="lineEnd">The end of the line</param>
    /// <param name="texture">The texture of the line</param>
    public static void DrawLine(Vector2 lineStart, Vector2 lineEnd, Texture2D texture)
    {
        if ((lineStart.x == lineEnd.x) && (lineStart.y == lineEnd.y))
            return;
        DrawLine(lineStart, lineEnd, texture, 1);
    }

    /// <summary>
    /// Draw a line between two points with the specified texture and thickness.
    /// The texture will be repeated to fill the drawing rectangle.
    /// Inspired by code posted by Sylvan and ArenMook
    /// http://forum.unity3d.com/threads/17066-How-to-draw-a-GUI-2D-quot-line-quot?p=407005&viewfull=1#post407005
    /// http://forum.unity3d.com/threads/28247-Tile-texture-on-a-GUI?p=416986&viewfull=1#post416986
    /// </summary>
    /// <param name="lineStart">The start of the line</param>
    /// <param name="lineEnd">The end of the line</param>
    /// <param name="texture">The texture of the line</param>
    /// <param name="thickness">The thickness of the line</param>
    public static void DrawLine(Vector2 lineStart, Vector2 lineEnd, Texture2D texture, int thickness)
    {
        if ((lineStart.x == lineEnd.x) && (lineStart.y == lineEnd.y))
            return;
        Vector2 lineVector = lineEnd - lineStart;
        float angle = Mathf.Rad2Deg * Mathf.Atan(lineVector.y / lineVector.x);
        if (lineVector.x < 0)
        {
            angle += 180;
        }

        if (thickness < 1)
        {
            thickness = 1;
        }

        // The center of the line will always be at the center
        // regardless of the thickness.
        int thicknessOffset = (int)Mathf.Ceil(thickness / 2);

        Rect drawingRect = new Rect(lineStart.x,
                                    lineStart.y - thicknessOffset,
                                    Vector2.Distance(lineStart, lineEnd),
                                    (float)thickness);
        GUIUtility.RotateAroundPivot(angle,
                                     lineStart);
        GUI.BeginGroup(drawingRect);
        {
            int drawingRectWidth = Mathf.RoundToInt(drawingRect.width);
            int drawingRectHeight = Mathf.RoundToInt(drawingRect.height);

            for (int y = 0; y < drawingRectHeight; y += texture.height)
            {
                for (int x = 0; x < drawingRectWidth; x += texture.width)
                {
                    GUI.DrawTexture(new Rect(x,
                                             y,
                                             texture.width,
                                             texture.height),
                                    texture);
                }
            }
        }
        GUI.EndGroup();
        GUIUtility.RotateAroundPivot(-angle, lineStart);
    }
}