#region Setup
using System;
using System.Collections.Generic;
using System.Globalization;
using System.IO;
using System.Linq;
using ChartForgeX.Core;
using ChartForgeX.Primitives;
using ChartForgeX.Rendering;
using ChartForgeX.Themes;
using ChartForgeX.Topology;
using ChartForgeX.Typography;
using ChartForgeX.VisualArtifacts;
using ChartForgeX.VisualBlocks;

var mode = VisualThemeMode.Light;
var theme = VisualTheme.Graphite();
var model = DifferenceAreaRecipe.Create("smooth-boundaries", mode);
var context = new VisualRenderContext(
    new VisualLayoutOptions(new VisualSize(800, 440)), theme, mode,
    new VisualFrame("Actual and forecast requests", "Shading compares Actual above and below Forecast", showLegend: null, showSurface: false));
var prepared = model.Prepare(context);
File.WriteAllText("visual.svg", prepared.ToSvg());
File.WriteAllBytes("visual.png", prepared.ToPng());
File.WriteAllText("visual.html", prepared.ToArtifact("example", VisualArtifactKind.Chart).ToHtmlPage());
#endregion

/// <summary>Builds actual-versus-forecast areas with crossings, gaps and stepped boundaries.</summary>
public static class DifferenceAreaRecipe {
    /// <summary>Creates the selected difference-area example from paired authored observations.</summary>
    public static Chart Create(string variant = "wide", VisualThemeMode mode = VisualThemeMode.Light) {
        if (variant is not ("wide" or "compact" or "sparse" or "options" or "compact-options" or "dated-gaps" or "compact-dated-gaps"
            or "step-start" or "step-middle" or "step-end" or "compact-step-middle" or "singleton" or "compact-singleton" or "dense" or "compact-dense" or "smooth-boundaries" or "compact-smooth-boundaries"))
            throw new ArgumentOutOfRangeException(nameof(variant));
        if (variant is "smooth-boundaries" or "compact-smooth-boundaries") {
            var smoothPairs = ChartDifferencePoints.FromXY(new[] { 1d, 2, 3, 4, 5, 6, 7, 8 },
                new double?[] { 42, 68, 48, null, 74, 46, 62, 55 }, new double?[] { 56, 54, 60, 60, 58, 64, 50, 68 });
            var smoothComparison = ChartSeries.CreateDifferenceArea(new ChartSeriesId("comparison"), "Actual and forecast", smoothPairs)
                .WithBoundaryInterpolation(new(ChartInterpolation.Smooth), new(ChartInterpolation.Step, ChartStepPosition.Middle))
                .WithObservationId(3, new ChartObservationId("resumed-comparison"))
                .ConfigureDifferenceArea(options => { options.FirstName = "Actual"; options.SecondName = "Forecast"; })
                .ConfigureMarkers(markers => markers.Radius = 3);
            return Chart.Create().WithTitle("Smooth actual and held forecast").WithXAxis("Observation").WithYAxis("Completed requests")
                .AddSeries(smoothComparison);
        }
        if (variant is "singleton" or "compact-singleton") return Chart.Create().WithTitle("One observed comparison")
            .AddSeries(ChartSeries.CreateDifferenceArea(new ChartSeriesId("comparison"), "Actual and forecast", new[] { new ChartDifferencePoint(0, 0, 7) })
                .WithObservationId(0, new ChartObservationId("only-comparison"))
                .ConfigureDifferenceArea(options => { options.FirstName = "Actual"; options.SecondName = "Forecast"; }));
        if (variant is "dense" or "compact-dense") return Chart.Create().WithTitle("Observed and forecast").WithXAxis("Observation").WithYAxis("Completed requests")
            .AddSeries(ChartSeries.CreateDifferenceArea(new ChartSeriesId("comparison"), "Actual and forecast",
                Enumerable.Range(0, 32).Select(index => new ChartDifferencePoint(index,
                    index % 7 == 0 ? 0 : Math.Sin(index * .6) * 9,
                    index % 7 == 0 ? 0 : Math.Cos(index * .6) * 7, index == 16)))
                .ConfigureDifferenceArea(options => { options.FirstName = "Actual"; options.SecondName = "Forecast"; })
                .ConfigureMarkers(options => options.Radius = 2));
        var dated = variant is "dated-gaps" or "compact-dated-gaps";
        var stepped = variant is "step-start" or "step-middle" or "step-end" or "compact-step-middle";
        var day = new DateTime(2026, 3, 1, 0, 0, 0, DateTimeKind.Utc);
        var actual = new[] { 42d, 68, stepped ? 78 : 48, 60, 74, 46, 62 };
        var forecast = new[] { 56d, 54, stepped ? 62 : 60, 60, 58, 64, 50 };
        var pairs = new ChartDifferencePoint[actual.Length];
        for (var item = 0; item < pairs.Length; item++) pairs[item] = dated
            ? new ChartDifferencePoint(day.AddDays(item + (item >= 4 ? 2 : 0)), actual[item], forecast[item], item == 4)
            : new ChartDifferencePoint(item + 1, actual[item], forecast[item], stepped && item == 5);
        var chart = Chart.Create().WithXAxis(dated ? "Observation date (UTC)" : "Observation")
            .WithYAxis(dated ? "Primary reference" : "Completed requests");
        if (dated) {
            chart.ConfigureXAxis(axis => axis.WithTimeScale());
            var reference = ChartSeries.CreateLine(new ChartSeriesId("primary-reference"), "Primary reference",
                new[] { new ChartPoint(day, 1), new ChartPoint(day.AddDays(8), 2) });
            chart.AddSeries(reference);
        }
        var comparison = ChartSeries.CreateDifferenceArea(new ChartSeriesId("comparison"), "Actual and forecast", pairs);
        comparison.ConfigureDifferenceArea(options => {
            options.FirstName = "Actual"; options.SecondName = "Forecast";
            options.PositiveFill = ChartColor.FromHex("#267EAB"); options.NegativeFill = ChartColor.FromHex("#D47A34");
            options.PositiveFillOpacity = .48; options.NegativeFillOpacity = .48;
        }).ConfigureMarkers(markers => markers.Radius = 3);
        if (stepped) comparison.WithInterpolation(ChartInterpolation.Step, variant switch {
            "step-start" => ChartStepPosition.Start,
            "step-end" => ChartStepPosition.End,
            _ => ChartStepPosition.Middle
        });
        if (dated) {
            comparison.UseSecondaryValueAxis().WithFillPattern(ChartFillPattern.DiagonalForward);
            chart.WithSecondaryYAxis("Completed requests");
        }
        return chart.AddSeries(comparison);
    }
}