using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
using Spectre.Console.Rendering;

namespace Spectre.Console
{
    internal sealed class ProgressBar : Renderable, IHasCulture
    {
        private const int PULSESIZE = 20;
        private const int PULSESPEED = 15;

        public double Value { get; set; }
        public double MaxValue { get; set; } = 100;

        public int? Width { get; set; }
        public bool ShowRemaining { get; set; } = true;
        public char UnicodeBar { get; set; } = '━';
        public char AsciiBar { get; set; } = '-';
        public bool ShowValue { get; set; }
        public bool IsIndeterminate { get; set; }
        public CultureInfo? Culture { get; set; }

        public Style CompletedStyle { get; set; } = new Style(foreground: Color.Yellow);
        public Style FinishedStyle { get; set; } = new Style(foreground: Color.Green);
        public Style RemainingStyle { get; set; } = new Style(foreground: Color.Grey);
        public Style IndeterminateStyle { get; set; } = DefaultPulseStyle;

        internal static Style DefaultPulseStyle { get; } = new Style(foreground: Color.DodgerBlue1, background: Color.Grey23);

        protected override Measurement Measure(RenderContext context, int maxWidth)
        {
            var width = Math.Min(Width ?? maxWidth, maxWidth);
            return new Measurement(4, width);
        }

        protected override IEnumerable<Segment> Render(RenderContext context, int maxWidth)
        {
            var width = Math.Min(Width ?? maxWidth, maxWidth);
            var completedBarCount = Math.Min(MaxValue, Math.Max(0, Value));
            var isCompleted = completedBarCount >= MaxValue;

            if (IsIndeterminate && !isCompleted)
            {
                foreach (var segment in RenderIndeterminate(context, width))
                {
                    yield return segment;
                }

                yield break;
            }

            var bar = !context.Unicode ? AsciiBar : UnicodeBar;
            var style = isCompleted ? FinishedStyle : CompletedStyle;
            var barCount = Math.Max(0, (int)(width * (completedBarCount / MaxValue)));

            // Show value?
            var value = completedBarCount.ToString(Culture ?? CultureInfo.InvariantCulture);
            if (ShowValue)
            {
                barCount = barCount - value.Length - 1;
                barCount = Math.Max(0, barCount);
            }

            if (barCount < 0)
            {
                yield break;
            }

            yield return new Segment(new string(bar, barCount), style);

            if (ShowValue)
            {
                yield return barCount == 0
                    ? new Segment(value, style)
                    : new Segment(" " + value, style);
            }

            // More space available?
            if (barCount < width)
            {
                var diff = width - barCount;
                if (ShowValue)
                {
                    diff = diff - value.Length - 1;
                    if (diff <= 0)
                    {
                        yield break;
                    }
                }

                var legacy = context.ColorSystem == ColorSystem.NoColors || context.ColorSystem == ColorSystem.Legacy;
                var remainingToken = ShowRemaining && !legacy ? bar : ' ';
                yield return new Segment(new string(remainingToken, diff), RemainingStyle);
            }
        }

        private IEnumerable<Segment> RenderIndeterminate(RenderContext context, int width)
        {
            var bar = context.Unicode ? UnicodeBar.ToString() : AsciiBar.ToString();
            var style = IndeterminateStyle ?? DefaultPulseStyle;

            IEnumerable<Segment> GetPulseSegments()
            {
                // For 1-bit and 3-bit colors, fall back to
                // a simpler versions with only two colors.
                if (context.ColorSystem == ColorSystem.NoColors ||
                    context.ColorSystem == ColorSystem.Legacy)
                {
                    // First half of the pulse
                    var segments = Enumerable.Repeat(new Segment(bar, new Style(style.Foreground)), PULSESIZE / 2);

                    // Second half of the pulse
                    var legacy = context.ColorSystem == ColorSystem.NoColors || context.ColorSystem == ColorSystem.Legacy;
                    var bar2 = legacy ? " " : bar;
                    segments = segments.Concat(Enumerable.Repeat(new Segment(bar2, new Style(style.Background)), PULSESIZE - (PULSESIZE / 2)));

                    foreach (var segment in segments)
                    {
                        yield return segment;
                    }

                    yield break;
                }

                for (var index = 0; index < PULSESIZE; index++)
                {
                    var position = index / (float)PULSESIZE;
                    var fade = 0.5f + ((float)Math.Cos(position * Math.PI * 2) / 2.0f);
                    var color = style.Foreground.Blend(style.Background, fade);

                    yield return new Segment(bar, new Style(foreground: color));
                }
            }

            // Get the pulse segments
            var pulseSegments = GetPulseSegments();
            pulseSegments = pulseSegments.Repeat((width / PULSESIZE) + 2);

            // Repeat the pulse segments
            var currentTime = (DateTime.Now - DateTime.Today).TotalSeconds;
            var offset = (int)(currentTime * PULSESPEED) % PULSESIZE;

            return pulseSegments.Skip(offset).Take(width);
        }
    }
}