using MailSharp.MailClient.Services;
using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.StaticFiles;

namespace MailSharp.MailClient.Controllers.Api;

// Serves cached external images referenced by allowed-sender messages, at
// /cache/images/{emailAddress}/{messageId}/{fileName} (fileName is "01.jpg" etc., see
// ImageSanitizer) so it's obvious on disk which images belong to which message. On the first
// request for a given file it doesn't exist yet: the handler looks up the original URL,
// downloads it now, saves it to disk, and serves it - every later request for that same file is
// then a plain disk read. Anonymous on purpose: the <img> lives inside a sandboxed srcdoc iframe
// (opaque origin), so the auth cookie would not reliably be sent for this subresource anyway -
// and a cached image is just already-public picture content, not account data, so serving it
// without a session is a low-risk trade-off.
[AllowAnonymous]
[ApiController]
public class ImageCacheController(IMailCacheStore cacheStore, IHttpClientFactory httpClientFactory) : ControllerBase
{
	private static readonly FileExtensionContentTypeProvider ContentTypeProvider = new();

	[HttpGet("/cache/images/{emailAddress}/{messageId}/{fileName}")]
	public async Task<IActionResult> GetImage(string emailAddress, string messageId, string fileName)
	{
		var existingPath = cacheStore.GetCachedImagePath(emailAddress, messageId, fileName);
		if (existingPath != null)
		{
			return PhysicalFile(existingPath, ResolveContentType(existingPath));
		}

		var url = cacheStore.GetImageSourceUrl(emailAddress, messageId, fileName);
		if (url == null) return NotFound();

		try
		{
			var client = httpClientFactory.CreateClient("ImageDownload");
			using var response = await client.GetAsync(url, HttpCompletionOption.ResponseHeadersRead);
			if (!response.IsSuccessStatusCode) return NotFound();

			var contentType = response.Content.Headers.ContentType?.MediaType ?? "";
			if (!contentType.StartsWith("image/", StringComparison.OrdinalIgnoreCase)) return NotFound();

			var bytes = await response.Content.ReadAsByteArrayAsync();
			if (bytes.Length == 0 || bytes.Length > 10_000_000) return NotFound();

			// The source URL had no extension (e.g. "/picture" with no ".jpg"): fall back to
			// guessing one from the response's actual Content-Type so the cached file isn't left
			// extensionless on disk.
			var finalFileName = EnsureExtension(fileName, contentType);
			var savedPath = cacheStore.SaveCachedImageFile(emailAddress, messageId, finalFileName, bytes);
			return PhysicalFile(savedPath, contentType);
		}
		catch
		{
			return NotFound();
		}
	}

	private static string EnsureExtension(string fileName, string contentType)
	{
		if (fileName.Contains('.')) return fileName;

		var extension = contentType.ToLowerInvariant() switch
		{
			"image/jpeg" or "image/jpg" => ".jpg",
			"image/png" => ".png",
			"image/gif" => ".gif",
			"image/webp" => ".webp",
			"image/bmp" => ".bmp",
			"image/svg+xml" => ".svg",
			"image/tiff" => ".tiff",
			"image/x-icon" or "image/vnd.microsoft.icon" => ".ico",
			"image/avif" => ".avif",
			"image/heic" => ".heic",
			_ => ""
		};

		return fileName + extension;
	}

	private static string ResolveContentType(string path) =>
		ContentTypeProvider.TryGetContentType(path, out var contentType) ? contentType : "application/octet-stream";
}