using DeluxeBackend.Services;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using SkiaSharp;
using System.Formats.Asn1;
using System.Security.Cryptography;
using System.Text;

namespace DeluxeBackend.Controllers
{
    [Route("Images")]
    [ApiController]
    public class ImagesController : ControllerBase
    {

        private readonly HttpClient httpClient;
        private readonly string _cachePath;

        

        public ImagesController(HttpClient httpClient, IWebHostEnvironment env)
        {
            this.httpClient = httpClient;
            _cachePath = Path.Combine(env.ContentRootPath, "image_cache");
        }

        [HttpGet("{*filePath}")]
        public async Task<IActionResult> GetImage(
            string filePath,
            [FromQuery] int? width = null,
            [FromQuery] int? height = null,
            [FromQuery] string? cropSquare = null,
            [FromQuery] string? sig = null)
        {
            if (string.IsNullOrEmpty(filePath)) return BadRequest();

            if (sig != null && sig != "p1") return BadRequest();

            bool crop = cropSquare?.ToLower() switch
            {
                "1" => true,
                "true" => true,
                _ => false
            };

            string cacheKey = GenerateCacheKey(filePath, width, height, crop);
            string cachedFilePath = Path.Combine(_cachePath, cacheKey + ".png");
            byte[] imageBytes;

            if (System.IO.File.Exists(cachedFilePath))
            {
                imageBytes = await System.IO.File.ReadAllBytesAsync(cachedFilePath);
            }
            else
            {
                string cdnUrl = $"{CdnService.Url.TrimEnd('/')}/img/{filePath}";

                try
                {
                    var response = await httpClient.GetAsync(cdnUrl);
                    if (!response.IsSuccessStatusCode) return NotFound();

                    using var stream = await response.Content.ReadAsStreamAsync();
                    using var original = SKBitmap.Decode(stream);

                    if (original == null) return await ServeRawFallback(cdnUrl, sig, filePath);

                    SKBitmap currentBitmap = original;

                    if (crop)
                    {
                        int size = Math.Min(original.Width, original.Height);
                        int x = (original.Width - size) / 2;
                        int y = (original.Height - size) / 2;

                        var subset = new SKBitmap(size, size);
                        original.ExtractSubset(subset, new SKRectI(x, y, x + size, y + size));
                        currentBitmap = subset;
                    }

                    if (width.HasValue || height.HasValue)
                    {
                        int w = width ?? (int)(currentBitmap.Width * ((float)height! / currentBitmap.Height));
                        int h = height ?? (int)(currentBitmap.Height * ((float)width! / currentBitmap.Width));

                        var info = new SKImageInfo(w, h);
                        var resized = new SKBitmap(info);
                        currentBitmap.ScalePixels(resized, SKSamplingOptions.Default);

                        if (currentBitmap != original) currentBitmap.Dispose();
                        currentBitmap = resized;
                    }

                    using (var image = SKImage.FromBitmap(currentBitmap))
                    using (var data = image.Encode(SKEncodedImageFormat.Png, 100))
                    {
                        imageBytes = data.ToArray();
                    }

                    if (currentBitmap != original) currentBitmap.Dispose();

                    if (!Directory.Exists(_cachePath)) Directory.CreateDirectory(_cachePath);
                    await System.IO.File.WriteAllBytesAsync(cachedFilePath, imageBytes);
                }
                catch
                {
                    return await ServeRawFallback(cdnUrl, sig, filePath);
                }
            }

            if (!string.IsNullOrEmpty(sig))
            {
                SignPayloadAndAppendHeader(imageBytes, sig);
            }

            return File(imageBytes, "image/png");
        }

        private async Task<IActionResult> ServeRawFallback(string url, string? sig, string? filename)
        {
            try
            {
                var response = await httpClient.GetAsync(url);
                if (!response.IsSuccessStatusCode) return NotFound();

                byte[] rawBytes = await response.Content.ReadAsByteArrayAsync();

                if (!string.IsNullOrEmpty(sig))
                {
                    SignPayloadAndAppendHeader(Encoding.UTF8.GetBytes(filename), sig);
                }

                string contentType = response.Content.Headers.ContentType?.ToString() ?? "application/octet-stream";
                return File(rawBytes, contentType);
            }
            catch
            {
                return StatusCode(500, "Error pipeline processing fallback asset safely.");
            }
        }

        private void SignPayloadAndAppendHeader(byte[] payload, string sig)
        {
            using var rsa = RSA.Create();
            rsa.ImportParameters(ServerConfig.RsaParams);

            byte[] signatureBytes = rsa.SignData(payload, HashAlgorithmName.SHA1, RSASignaturePadding.Pkcs1);
            string base64Signature = Convert.ToBase64String(signatureBytes);

            Response.Headers.Append("Content-Signature", $"key-id=KEY:RSA:{sig}.rec.net; data={base64Signature};");
        }

        private static string GenerateCacheKey(string path, int? w, int? h, bool crop)
        {
            string rawKey = $"{path}_{w}_{h}_{crop}";
            byte[] hashBytes = SHA256.HashData(Encoding.UTF8.GetBytes(rawKey));
            return Convert.ToHexString(hashBytes);
        }
    }
}