using System;
using System.Collections.Generic;
using System.Drawing;
using System.Linq;

namespace OpenNest
{
    /// <summary>
    /// The colors drawings are given by position. Immutable: it copies the colors it is given,
    /// so a caller's later edits to its own array never change what drawings receive.
    /// </summary>
    public sealed class PartPalette
    {
        private readonly Color[] colors;

        public PartPalette(IEnumerable<Color> colors, bool useGoldenAngle = false)
        {
            ArgumentNullException.ThrowIfNull(colors);
            this.colors = colors.ToArray();
            Colors = Array.AsReadOnly(this.colors);
            UseGoldenAngle = useGoldenAngle;
        }

        /// <summary>The default palette, also the fallback before a color scheme is applied.</summary>
        public static PartPalette Classic { get; } = new PartPalette(new[]
        {
            Color.FromArgb(205, 92, 92), // Indian Red
            Color.FromArgb(148, 103, 189), // Medium Purple
            Color.FromArgb(75, 180, 175), // Teal
            Color.FromArgb(210, 190, 75), // Goldenrod
            Color.FromArgb(190, 85, 175), // Orchid
            Color.FromArgb(185, 115, 85), // Sienna
            Color.FromArgb(120, 100, 190), // Slate Blue
            Color.FromArgb(200, 100, 140), // Rose
            Color.FromArgb(80, 175, 155), // Sea Green
            Color.FromArgb(195, 160, 85), // Dark Khaki
            Color.FromArgb(175, 95, 160), // Plum
            Color.FromArgb(215, 130, 130), // Light Coral
        });

        /// <summary>The explicit colors, cycled by <see cref="ColorAt"/> unless <see cref="UseGoldenAngle"/>.</summary>
        public IReadOnlyList<Color> Colors { get; }

        /// <summary>When set, colors are generated by <see cref="PartColorPalette.GoldenAngle"/> instead of cycled.</summary>
        public bool UseGoldenAngle { get; }

        public Color ColorAt(int index)
        {
            ArgumentOutOfRangeException.ThrowIfNegative(index);
            return UseGoldenAngle
                ? PartColorPalette.GoldenAngle(index)
                : colors[index % colors.Length];
        }
    }
}