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("step-middle", mode);
var context = new VisualRenderContext(
    new VisualLayoutOptions(new VisualSize(800, 440)), theme, mode,
    new VisualFrame("Actual and forecast requests", "Paired values change halfway between observations; missing sections stay open", 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());

/// <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"))
            throw new ArgumentOutOfRangeException(nameof(variant));
        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.UseSecondaryYAxis().WithFillPattern(ChartFillPattern.DiagonalForward);
            chart.WithSecondaryYAxis("Completed requests");
        }
        return chart.AddSeries(comparison).WithValueFormat(ChartValueFormat.Number("0.##", CultureInfo.InvariantCulture));
    }
}