// --------------------------------------------------------------------------------------------------------------------
// <copyright file="CommonParameterParserUtility.cs" company="James South">
//   Copyright (c) James South.
//   Licensed under the Apache License, Version 2.0.
// </copyright>
// <summary>
//   Encapsulates methods to correctly parse querystring parameters.
// </summary>
// --------------------------------------------------------------------------------------------------------------------

namespace ImageProcessor.Web.Helpers
{
    using System;
    using System.Collections.Generic;
    using System.Drawing;
    using System.Globalization;
    using System.Text;
    using System.Text.RegularExpressions;

    using ImageProcessor.Common.Extensions;
    using ImageProcessor.Imaging;
    using ImageProcessor.Web.Extensions;

    /// <summary>
    /// Encapsulates methods to correctly parse querystring parameters.
    /// </summary>
    public static class CommonParameterParserUtility
    {
        /// <summary>
        /// The collection of known colors.
        /// </summary>
        private static readonly Dictionary<string, KnownColor> KnownColors = new Dictionary<string, KnownColor>();

        /// <summary>
        /// The regular expression to search strings for colors.
        /// </summary>
        private static readonly Regex ColorRegex = BuildColorRegex();
 
        /// <summary>
        /// The regular expression to search strings for angles.
        /// </summary>
        private static readonly Regex AngleRegex = new Regex(@"(rotate|angle)(=|-)(?:3[0-5][0-9]|[12][0-9]{2}|[1-9][0-9]?)", RegexOptions.Compiled);

        /// <summary>
        /// The regular expression to search strings for values between 1 and 100.
        /// </summary>
        private static readonly Regex In100RangeRegex = new Regex(@"(-?0*(?:100|[1-9][0-9]?))", RegexOptions.Compiled);

        /// <summary>
        /// The sharpen regex.
        /// </summary>
        private static readonly Regex BlurSharpenRegex = new Regex(@"(blur|sharpen)=\d+", RegexOptions.Compiled);

        /// <summary>
        /// The sigma regex.
        /// </summary>
        private static readonly Regex SigmaRegex = new Regex(@"sigma(=|-)\d+(.?\d+)?", RegexOptions.Compiled);

        /// <summary>
        /// The threshold regex.
        /// </summary>
        private static readonly Regex ThresholdRegex = new Regex(@"threshold(=|-)\d+", RegexOptions.Compiled);

        /// <summary>
        /// Returns the correct <see cref="T:System.Int32"/> containing the angle for the given string.
        /// </summary>
        /// <param name="input">
        /// The input string containing the value to parse.
        /// </param>
        /// <returns>
        /// The correct <see cref="T:System.Int32"/> containing the angle for the given string.
        /// </returns>
        public static int ParseAngle(string input)
        {
            foreach (Match match in AngleRegex.Matches(input))
            {
                // Split on angle
                int angle;
                string value = match.Value.Split(new[] { '=', '-' })[1];
                int.TryParse(value, NumberStyles.Any, CultureInfo.InvariantCulture, out angle);
                return angle;
            }

            // No rotate - matches the RotateLayer default.
            return 0;
        }

        /// <summary>
        /// Returns the correct <see cref="T:System.Drawing.Color"/> for the given string.
        /// </summary>
        /// <param name="input">
        /// The input string containing the value to parse.
        /// </param>
        /// <returns>
        /// The correct <see cref="T:System.Drawing.Color"/>
        /// </returns>
        public static Color ParseColor(string input)
        {
            foreach (Match match in ColorRegex.Matches(input))
            {
                string value = match.Value.Split(new[] { '=', '-' })[1];

                if (KnownColors.ContainsKey(value))
                {
                    return Color.FromKnownColor(KnownColors[value]);
                }

                if (value.Contains(","))
                {
                    int[] split = value.ToPositiveIntegerArray();
                    byte red = split[0].ToByte();
                    byte green = split[1].ToByte();
                    byte blue = split[2].ToByte();
                    byte alpha = split[3].ToByte();

                    return Color.FromArgb(alpha, red, green, blue);
                }

                // Split on color-hex
                return ColorTranslator.FromHtml("#" + value);
            }

            return Color.Transparent;
        }

        /// <summary>
        /// Returns the correct <see cref="T:System.Int32"/> for the given string.
        /// </summary>
        /// <param name="input">
        /// The input string containing the value to parse.
        /// </param>
        /// <returns>
        /// The correct <see cref="T:System.Int32"/> between -100 and 100.
        /// </returns>
        public static int ParseIn100Range(string input)
        {
            int value = 0;
            foreach (Match match in In100RangeRegex.Matches(input))
            {
                value = int.Parse(match.Value, CultureInfo.InvariantCulture);
            }

            return value;
        }

        /// <summary>
        /// Returns the correct <see cref="GaussianLayer"/> for the given string.
        /// </summary>
        /// <param name="input">
        /// The input string containing the value to parse.
        /// </param>
        /// <param name="maxSize">
        /// The maximum size to set the Gaussian kernel to.
        /// </param>
        /// <param name="maxSigma">
        /// The maximum Sigma value (standard deviation) for Gaussian function used to calculate the kernel.
        /// </param>
        /// <param name="maxThreshold">
        /// The maximum threshold value, which is added to each weighted sum of pixels.
        /// </param>
        /// <returns>
        /// The correct <see cref="GaussianLayer"/> .
        /// </returns>
        public static GaussianLayer ParseGaussianLayer(string input, int maxSize, double maxSigma, int maxThreshold)
        {
            int size = ParseBlurSharpen(input);
            double sigma = ParseSigma(input);
            int threshold = ParseThreshold(input);

            size = maxSize < size ? maxSize : size;
            sigma = maxSigma < sigma ? maxSigma : sigma;
            threshold = maxThreshold < threshold ? maxThreshold : threshold;

            return new GaussianLayer(size, sigma, threshold);
        }

        /// <summary>
        /// Returns the correct <see cref="T:System.Int32"/> containing the blur value
        /// for the given string.
        /// </summary>
        /// <param name="input">
        /// The input string containing the value to parse.
        /// </param>
        /// <returns>
        /// The correct <see cref="T:System.Int32"/> for the given string.
        /// </returns>
        private static int ParseBlurSharpen(string input)
        {
            // ReSharper disable once LoopCanBeConvertedToQuery
            foreach (Match match in BlurSharpenRegex.Matches(input))
            {
                return Convert.ToInt32(match.Value.Split('=')[1]);
            }

            return 0;
        }

        /// <summary>
        /// Returns the correct <see cref="T:System.Double"/> containing the sigma value
        /// for the given string.
        /// </summary>
        /// <param name="input">
        /// The input string containing the value to parse.
        /// </param>
        /// <returns>
        /// The correct <see cref="T:System.Double"/> for the given string.
        /// </returns>
        private static double ParseSigma(string input)
        {
            foreach (Match match in SigmaRegex.Matches(input))
            {
                // split on text-
                return Convert.ToDouble(match.Value.Split(new[] { '=', '-' })[1]);
            }

            return 1.4d;
        }

        /// <summary>
        /// Returns the correct <see cref="T:System.Int32"/> containing the threshold value
        /// for the given string.
        /// </summary>
        /// <param name="input">
        /// The input string containing the value to parse.
        /// </param>
        /// <returns>
        /// The correct <see cref="T:System.Int32"/> for the given string.
        /// </returns>
        private static int ParseThreshold(string input)
        {
            // ReSharper disable once LoopCanBeConvertedToQuery
            foreach (Match match in ThresholdRegex.Matches(input))
            {
                return Convert.ToInt32(match.Value.Split(new[] { '=', '-' })[1]);
            }

            return 0;
        }

        /// <summary>
        /// Builds a regular expression for the three main colour types.
        /// </summary>
        /// <returns>
        /// The <see cref="Regex"/> to match colors.
        /// </returns>
        private static Regex BuildColorRegex()
        {
            StringBuilder stringBuilder = new StringBuilder();
            stringBuilder.Append(@"(bgcolor|color|tint|vignette)(=|-)(\d+,\d+,\d+,\d+|([0-9a-fA-F]{3}){1,2}|(");

            KnownColor[] knownColors = (KnownColor[])Enum.GetValues(typeof(KnownColor));

            for (int i = 0; i < knownColors.Length; i++)
            {
                KnownColor knownColor = knownColors[i];
                string name = knownColor.ToString().ToLowerInvariant();

                KnownColors.Add(name, knownColor);

                stringBuilder.Append(i > 0 ? "|" + name : name);
            }

            stringBuilder.Append("))");

            return new Regex(stringBuilder.ToString(), RegexOptions.IgnoreCase);
        }
    }
}