using System;
using System.Collections.Generic;
using System.Globalization;
using System.IO;
using System.Text.RegularExpressions;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Content;
using Microsoft.Xna.Framework.Graphics;
using MLEM.Extensions;
using MLEM.Misc;
using MLEM.Textures;
#if FNA
using MLEM.Extensions;
#endif

namespace MLEM.Data {
    /// <summary>
    /// <para>
    /// This class represents an atlas of <see cref="TextureRegion"/> objects which are loaded from a special texture atlas file.
    /// To load a data texture atlas, you can use <see cref="DataTextureAtlasExtensions.LoadTextureAtlas"/>.
    /// </para>
    /// <para>
    /// Data texture atlases are designed to be easy to write by hand. Because of this, their structure is very simple.
    /// Each texture region defined in the atlas consists of its names (where multiple names can be separated by whitespace), followed by a set of possible instructions and their arguments, also separated by whitespace.
    /// <list type="bullet">
    /// <item><description>The <c>loc</c> (or <c>location</c>) instruction defines the <see cref="TextureRegion.Area"/> of the texture region as a rectangle whose origin is its top-left corner. It requires four arguments: x, y, width and height of the rectangle.</description></item>
    /// <item><description>The (optional) <c>piv</c> (or <c>pivot</c>) instruction defines the <see cref="TextureRegion.PivotPixels"/> of the texture region. It requires two arguments: x and y. If it is not supplied, the pivot defaults to the top-left corner of the texture region.</description></item>
    /// <item><description>The (optional) <c>off</c> (of <c>offset</c>) instruction defines an offset that is added onto the location and pivot of this texture region. This is useful when duplicating a previously defined texture region to create a second region that has a constant offset. It requires two arguments: The x and y offset.</description></item>
    /// <item><description>The (optional and repeatable) <c>cpy</c> (or <c>copy</c>) instruction defines an additional texture region that should also be generated from the same data, but with a given offset that will be applied to the location and pivot. It requires three arguments: the copy region's name and the x and y offsets.</description></item>
    /// <item><description>The (optional and repeatable) <c>dat</c> (or <c>data</c>) instruction defines a custom data point that can be added to the resulting <see cref="TextureRegion"/>'s <see cref="GenericDataHolder"/> data. It requires two arguments: the data point's name and the data point's value, the latter of which is also stored as a string value.</description></item>
    /// </list>
    /// </para>
    /// <example>
    /// The following entry defines a texture region with the names <c>LongTableRight</c> and <c>LongTableUp</c>, whose <see cref="TextureRegion.Area"/> will be a rectangle with X=32, Y=30, Width=64, Height=48, and whose <see cref="TextureRegion.PivotPixels"/> will be a vector with X=80, Y=46.
    /// <code>
    /// LongTableRight LongTableUp
    /// loc 32 30 64 48
    /// piv 80 46
    /// </code>
    /// </example>
    /// </summary>
    /// <remarks>
    /// To see a Data Texture Atlas in action, you can check out the sandbox project: https://github.com/Ellpeck/MLEM/blob/main/Sandbox/Content/Textures/Furniture.atlas.
    /// Additionally, if you are using Aseprite, there is a script to automatically populate it: https://gist.github.com/Ellpeck/e597c1412465c10f41a42050ec117ea2.
    /// </remarks>
    public class DataTextureAtlas {

        /// <summary>
        /// The texture to use for this atlas
        /// </summary>
        public readonly TextureRegion Texture;
        /// <summary>
        /// Returns the texture region with the given name, or null if it does not exist.
        /// </summary>
        /// <param name="name">The region's name</param>
        public TextureRegion this[string name] {
            get {
                this.regions.TryGetValue(name, out var ret);
                return ret;
            }
        }
        /// <summary>
        /// Returns an enumerable of all of the <see cref="TextureRegion"/> values in this atlas.
        /// </summary>
        public IEnumerable<TextureRegion> Regions => this.regions.Values;
        /// <summary>
        /// Returns an enumerable of all of the <see cref="TextureRegion"/> names in this atlas.
        /// </summary>
        public IEnumerable<string> RegionNames => this.regions.Keys;

        private readonly Dictionary<string, TextureRegion> regions = new Dictionary<string, TextureRegion>();

        private DataTextureAtlas(TextureRegion texture) {
            this.Texture = texture;
        }

        /// <summary>
        /// Loads a <see cref="DataTextureAtlas"/> from the given loaded texture and texture data file.
        /// For more information on data texture atlases, see the <see cref="DataTextureAtlas"/> type documentation.
        /// </summary>
        /// <param name="texture">The texture to use for this data texture atlas</param>
        /// <param name="content">The content manager to use for loading</param>
        /// <param name="infoPath">The path, including extension, to the atlas info file</param>
        /// <param name="pivotRelative">If this value is true, then the pivot points passed in the info file will be relative to the coordinates of the texture region, not relative to the entire texture's origin.</param>
        /// <returns>A new data texture atlas with the given settings</returns>
        public static DataTextureAtlas LoadAtlasData(TextureRegion texture, ContentManager content, string infoPath, bool pivotRelative = false) {
            var info = Path.Combine(content.RootDirectory, infoPath);
            string text;
            try {
                if (Path.IsPathRooted(info)) {
                    text = File.ReadAllText(info);
                } else {
                    using (var reader = new StreamReader(TitleContainer.OpenStream(info)))
                        text = reader.ReadToEnd();
                }
            } catch (Exception e) {
                throw new ContentLoadException($"Couldn't load data texture atlas data from {info}", e);
            }
            var atlas = new DataTextureAtlas(texture);
            var words = Regex.Split(text, @"\s+");

            var namesOffsets = new List<(string, Vector2)>();
            var customData = new Dictionary<string, string>();
            var location = Rectangle.Empty;
            var pivot = Vector2.Zero;
            var offset = Vector2.Zero;
            for (var i = 0; i < words.Length; i++) {
                var word = words[i];
                try {
                    switch (word) {
                        case "loc":
                        case "location":
                            location = new Rectangle(
                                int.Parse(words[i + 1], CultureInfo.InvariantCulture), int.Parse(words[i + 2], CultureInfo.InvariantCulture),
                                int.Parse(words[i + 3], CultureInfo.InvariantCulture), int.Parse(words[i + 4], CultureInfo.InvariantCulture));
                            i += 4;
                            break;
                        case "piv":
                        case "pivot":
                            pivot = new Vector2(
                                float.Parse(words[i + 1], CultureInfo.InvariantCulture),
                                float.Parse(words[i + 2], CultureInfo.InvariantCulture));
                            i += 2;
                            break;
                        case "off":
                        case "offset":
                            offset = new Vector2(
                                float.Parse(words[i + 1], CultureInfo.InvariantCulture),
                                float.Parse(words[i + 2], CultureInfo.InvariantCulture));
                            i += 2;
                            break;
                        case "cpy":
                        case "copy":
                            var copyOffset = new Vector2(
                                float.Parse(words[i + 2], CultureInfo.InvariantCulture),
                                float.Parse(words[i + 3], CultureInfo.InvariantCulture));
                            namesOffsets.Add((words[i + 1], copyOffset));
                            i += 3;
                            break;
                        case "dat":
                        case "data":
                            customData.Add(words[i + 1], words[i + 2]);
                            i += 2;
                            break;
                        default:
                            // if we have a location for the previous regions, they're valid so we add them
                            if (location != Rectangle.Empty && namesOffsets.Count > 0) {
                                location.Offset(offset.ToPoint());
                                pivot += offset;
                                if (!pivotRelative)
                                    pivot -= location.Location.ToVector2();

                                foreach (var (name, off) in namesOffsets) {
                                    var region = new TextureRegion(texture, location.OffsetCopy(off.ToPoint())) {
                                        PivotPixels = pivot + off,
                                        Name = name
                                    };
                                    foreach (var kv in customData)
                                        region.SetData(kv.Key, kv.Value);
                                    atlas.regions.Add(name, region);
                                }
                                namesOffsets.Clear();
                            }

                            // we're starting a new region (or adding another name for a new region), so clear old data
                            namesOffsets.Add((word.Trim(), Vector2.Zero));
                            customData.Clear();
                            location = Rectangle.Empty;
                            pivot = Vector2.Zero;
                            offset = Vector2.Zero;
                            break;
                    }
                } catch (Exception e) {
                    throw new ContentLoadException($"Couldn't parse data texture atlas instruction {word} for region(s) {string.Join(", ", namesOffsets)}", e);
                }
            }

            return atlas;
        }

    }

    /// <summary>
    /// A set of extension methods for dealing with <see cref="DataTextureAtlas"/>.
    /// </summary>
    public static class DataTextureAtlasExtensions {

        /// <summary>
        /// Loads a <see cref="DataTextureAtlas"/> from the given texture and texture data file.
        /// For more information on data texture atlases, see the <see cref="DataTextureAtlas"/> type documentation.
        /// </summary>
        /// <param name="content">The content manager to use for loading</param>
        /// <param name="texturePath">The path to the texture file</param>
        /// <param name="infoPath">The path, including extension, to the atlas info file, or null if "<paramref name="texturePath"/>.atlas" should be used</param>
        /// <param name="pivotRelative">If this value is true, then the pivot points passed in the info file will be relative to the coordinates of the texture region, not relative to the entire texture's origin.</param>
        /// <returns>A new data texture atlas with the given settings</returns>
        public static DataTextureAtlas LoadTextureAtlas(this ContentManager content, string texturePath, string infoPath = null, bool pivotRelative = false) {
            var texture = new TextureRegion(content.Load<Texture2D>(texturePath));
            return DataTextureAtlas.LoadAtlasData(texture, content, infoPath ?? $"{texturePath}.atlas", pivotRelative);
        }

    }
}