using System.IO;
using SkiaSharp;

namespace Jellyfin.Plugin.SRFPlay.Utilities;

/// <summary>
/// Generates placeholder images for content without thumbnails.
/// </summary>
public static class PlaceholderImageGenerator
{
    private const int Width = 640;
    private const int Height = 360; // 16:9 aspect ratio

    /// <summary>
    /// Generates a placeholder image with the given text centered.
    /// </summary>
    /// <param name="text">The text to display (typically channel/show name).</param>
    /// <returns>A memory stream containing the PNG image.</returns>
    public static MemoryStream GeneratePlaceholder(string text)
    {
        using var surface = SKSurface.Create(new SKImageInfo(Width, Height));
        var canvas = surface.Canvas;

        // Dark gradient background
        using var backgroundPaint = new SKPaint();
        using var shader = SKShader.CreateLinearGradient(
            new SKPoint(0, 0),
            new SKPoint(Width, Height),
            new[] { new SKColor(45, 45, 48), new SKColor(28, 28, 30) },
            null,
            SKShaderTileMode.Clamp);
        backgroundPaint.Shader = shader;
        canvas.DrawRect(0, 0, Width, Height, backgroundPaint);

        // Text
        using var textPaint = new SKPaint
        {
            Color = SKColors.White,
            IsAntialias = true,
            TextAlign = SKTextAlign.Center,
            Typeface = SKTypeface.FromFamilyName("Arial", SKFontStyle.Bold)
        };

        // Calculate font size to fit text (max 48, min 24)
        float fontSize = 48;
        textPaint.TextSize = fontSize;
        var textWidth = textPaint.MeasureText(text);
        var maxWidth = Width * 0.85f;

        if (textWidth > maxWidth)
        {
            fontSize = fontSize * maxWidth / textWidth;
            fontSize = fontSize < 24 ? 24 : fontSize;
            textPaint.TextSize = fontSize;
        }

        // Center text vertically
        SKRect textBounds = default;
        textPaint.MeasureText(text, ref textBounds);
        var yPos = (Height / 2) - textBounds.MidY;

        canvas.DrawText(text, Width / 2, yPos, textPaint);

        // Encode to PNG
        using var image = surface.Snapshot();
        using var data = image.Encode(SKEncodedImageFormat.Png, 100);

        var stream = new MemoryStream();
        data.SaveTo(stream);
        stream.Position = 0;
        return stream;
    }
}