using System;

namespace codelanguage;

public readonly record struct ScreenPixelPosition(double X, double Y);

public static class ScreenLocLayout
{
    public static bool TryResolve(string? screenLoc, double viewportWidth, double viewportHeight, double tileSize, out ScreenPixelPosition position)
    {
        if (ScreenLocParser.TryParse(screenLoc, out var parsed))
        {
            position = Resolve(parsed, viewportWidth, viewportHeight, tileSize);
            return true;
        }
        position = default;
        return false;
    }

    public static ScreenPixelPosition Resolve(ScreenLocPosition location, double viewportWidth, double viewportHeight, double tileSize)
    {
        var width = Math.Max(0, viewportWidth);
        var height = Math.Max(0, viewportHeight);
        var x = ResolveAxis(location.XAnchor, location.XOffset, width, tileSize, horizontal: true);
        var y = ResolveAxis(location.YAnchor, location.YOffset, height, tileSize, horizontal: false);
        return new ScreenPixelPosition(x + location.XPixelOffset, y + location.YPixelOffset);
    }

    private static double ResolveAxis(string anchor, double offset, double extent, double tile, bool horizontal)
    {
        if (anchor == "NUMERIC") return Math.Max(0, offset * tile);
        if (anchor == "CENTER" || anchor == "MIDDLE") return extent / 2 + offset * tile;
        if (anchor.EndsWith("_PERCENT", StringComparison.Ordinal)) return extent * offset / 100.0;
        if (anchor.StartsWith("SCREEN_", StringComparison.Ordinal)) anchor = anchor[7..];

        bool positive = anchor is "RIGHT" or "TOP" or "EAST" or "NORTH" or "NORTHEAST" or "NORTHWEST";
        bool edge = anchor is "LEFT" or "RIGHT" or "TOP" or "BOTTOM";
        if (horizontal)
        {
            if (anchor.Contains("EAST", StringComparison.Ordinal) || anchor == "RIGHT") return extent + offset * tile;
            if (anchor.Contains("WEST", StringComparison.Ordinal) || anchor == "LEFT") return offset * tile;
        }
        else
        {
            if (anchor.Contains("NORTH", StringComparison.Ordinal) || anchor == "TOP") return extent + offset * tile;
            if (anchor.Contains("SOUTH", StringComparison.Ordinal) || anchor == "BOTTOM") return offset * tile;
        }
        return (positive || edge) ? extent + offset * tile : offset * tile;
    }
}