using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Drawing;
using MuPDF;
using MuPDF.Extensions;
using PDFPatcher.Common;
using DrawingPoint = System.Drawing.Point;
using MuPoint = MuPDF.Point;
using MuRectangle = MuPDF.Box;

namespace PDFPatcher.Functions.Editor;

public enum ContentDirection
{
	Auto,
	TopToDown,
	RightToLeft,
	LeftToRight,
}

public enum MouseMode
{
	Move, Selection
}

public readonly struct PagePoint(int pageNumber, float imageX, float imageY) : IEquatable<PagePoint>
{
	public static readonly PagePoint Empty;

	public readonly int Page = pageNumber;
	public readonly float ImageX = imageX, ImageY = imageY;

	public override bool Equals(object obj) {
		return obj is PagePoint point && Equals(point);
	}

	public bool Equals(PagePoint other) {
		return Page == other.Page &&
			   ImageX == other.ImageX &&
			   ImageY == other.ImageY;
	}

	public override int GetHashCode() {
		int hashCode = -1954381243;
		hashCode = hashCode * -1521134295 + Page.GetHashCode();
		hashCode = hashCode * -1521134295 + ImageX.GetHashCode();
		hashCode = hashCode * -1521134295 + ImageY.GetHashCode();
		return hashCode;
	}

	public static bool operator ==(PagePoint left, PagePoint right) {
		return left.Equals(right);
	}

	public static bool operator !=(PagePoint left, PagePoint right) {
		return !(left == right);
	}
}

readonly struct PagePosition
{
	public static readonly PagePosition Empty = default;
	/// <summary>
	/// 所在页码。
	/// </summary>
	public readonly int Page;
	/// <summary>
	/// 在 PDF 页面空间上的位置。
	/// </summary>
	public readonly float PageX, PageY;
	/// <summary>
	/// 在渲染页面上的位置。
	/// </summary>
	public readonly int ImageX, ImageY;
	/// <summary>
	/// 当前点是否在页面上。
	/// </summary>
	public readonly bool IsInPage;

	internal PagePosition(int page, PointF position, DrawingPoint imagePosition, bool isInPage)
		: this(page, position.X, position.Y, imagePosition.X, imagePosition.Y, isInPage) { }

	internal PagePosition(int page, float x, float y, int imageX, int imageY, bool isInPage) {
		Page = page;
		PageX = x;
		PageY = y;
		ImageX = imageX;
		ImageY = imageY;
		IsInPage = isInPage;
	}

	public MuPoint Location => new(PageX, PageY);

	public MuPoint ToPageCoordinate(Page page) {
		var pb = page.Bound;
		return new MuPoint(PageX - pb.Left, pb.Bottom - PageY);
	}
}

readonly struct PageRegion
{
	public static readonly PageRegion Empty = new PageRegion();

	public readonly int Page;
	public readonly MuRectangle Region;

	internal PageRegion(PagePosition p1, PagePosition p2) {
		if (p1.Page != p2.Page) {
			Page = 0;
			Region = new MuRectangle();
		}
		else {
			Page = p1.Page;
			Region = new MuRectangle(p1.PageX, p1.PageY, p2.PageX, p2.PageY);
		}
	}

	public MuRectangle ToPageCoordinate(Page page) {
		var r = Region;
		var pb = page.Bound;
		return new MuRectangle(r.Left,
			pb.Bottom - r.Top,
			r.Right,
			pb.Bottom - r.Bottom);
	}
}

readonly struct TextInfo(Page page, MuRectangle bbox, List<TextLine> textLines, List<TextSpan> spans)
{
	public readonly Page Page = page;

	/// <summary>获取文本字符的位置边框。</summary>
	public readonly MuRectangle TextBBox = bbox;
	/// <summary>获取文本位置以下的文本行。</summary>
	public readonly List<TextLine> Lines = textLines;
	public readonly List<TextSpan> Spans = spans;

	public MuRectangle BBox => TextBBox;

	public IEnumerable<TextFont> GetFonts() {
		if (!Spans.HasContent()) {
			yield break;
		}
		var fonts = new HashSet<TextFont>();
		foreach (var span in Spans) {
			if (fonts.Add(span.Font)) {
				yield return span.Font;
			}
		}
	}

	public IEnumerable<string> GetFontNames() {
		if (!Spans.HasContent()) {
			yield break;
		}
		HashSet<string> fonts = [];
		foreach (var span in Spans) {
			var f = span.Font;
			if (fonts.Add(f.Name)) {
				yield return f.Name;
			}
		}
	}

	public override string ToString() {
		if (Lines == null) {
			return null;
		}
		var c = Lines.Count;
		if (c == 1) {
			return Lines[0].GetText();
		}
		var sb = StringBuilderCache.Acquire(100);
		var b = Lines[0].Bound;
		foreach (var line in Lines) {
			if (line.Bound.IsHorizontalNeighbor(b)) {
				sb.Append(line.GetText());
				b = b.Union(line.Bound);
			}
			else {
				b = line.Bound;
				sb.AppendLine();
				sb.Append(line.GetText());
			}
		}
		return StringBuilderCache.GetStringAndRelease(sb);
	}
}

[DebuggerDisplay("Point={Point}; Font={Font}; Size={Size}; Color={Color}; Text={Text}")]
public sealed class TextSpan(TextLine line, MuPoint point, string text, float size, TextFont font, MuRectangle box, int color)
{
	public TextLine Line { get; } = line;
	public MuPoint Point { get; } = point;
	public string Text { get; } = text;
	public float Size { get; } = size;
	public TextFont Font { get; } = font;
	public MuRectangle Box { get; } = box;
	public int Color { get; } = color;

	public static IEnumerable<TextSpan> GetTextSpans(TextLine line) {
		var r = new List<TextSpan>(2);
		var ch = line.FirstCharacter;
		var start = ch;
		var end = line.LastCharacter;
		var size = ch.Size;
		var font = ch.Font;
		var color = ch.Color;
		var t = StringBuilderCache.Acquire(100);
		t.Append((char)ch.Character);
		do {
			ch = ch.Next;
			if (ch is null) {
				break;
			}
			if (start.HasSameStyle(ch)) {
				t.Append((char)ch.Character);
				continue;
			}
			r.Add(new TextSpan(line, start.Origin, t.ToString(), size, font, start.Quad.Union(ch.Quad).ToBox(), color));
			t.Length = 0;
			size = ch.Size;
			font = ch.Font;
			color = ch.Color;
			start = ch;
			t.Append((char)ch.Character);
		} while (ch != end);
		if (t.Length > 0) {
			var s = StringBuilderCache.GetStringAndRelease(t).TrimEnd();
			if (s.Length > 0) {
				r.Add(new TextSpan(line, start.Origin, s, size, font, start.Quad.Union(end.Quad).ToBox(), color));
			}
		}
		else {
			StringBuilderCache.Release(t);
		}
		return r;
	}
}

readonly struct Selection(RenderResultCache cache, int page, MuRectangle region, RectangleF imageRegion)
{
	public static readonly Selection Empty = default;

	readonly RenderResultCache _cache = cache;
	/// <summary>
	/// 获取选中区域的页码。
	/// </summary>
	public readonly int Page = page;
	/// <summary>
	/// 获取选中区域在页面上的矩形区域（屏幕左下角点坐标为0，0）。
	/// </summary>
	public readonly MuRectangle PageRegion = region;
	/// <summary>
	/// 获取选中区域在显示图片上的矩形区域。
	/// </summary>
	public readonly RectangleF ImageRegion = imageRegion;

	public Bitmap GetSelectedBitmap() {
		_cache.LoadPage(Page);
		var p = _cache.GetBitmap(Page);
		return p.Clone(new MuRectangle(
				Math.Max(ImageRegion.Left, 0),
				Math.Max(ImageRegion.Top, 0),
				Math.Min(ImageRegion.Right, p.Width),
				Math.Min(ImageRegion.Bottom, p.Height)
			).ToRectangleF(), p.PixelFormat);
	}
}