MilkyShots/Lactose/Controllers/MediaController.cs

using Butter.Types;
using Lactose.Configuration;
using Lactose.Repositories;
using Lactose.Services;
using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.RateLimiting;
using Microsoft.Extensions.Options;
using Microsoft.IdentityModel.Tokens;
using System.IdentityModel.Tokens.Jwt;

namespace Lactose.Controllers;

/// <summary>
/// Serves media files (original, thumbnail, preview) for assets.
/// </summary>
/// <param name="authService">Authentication service.</param>
/// <param name="mediaRepository">Media repository.</param>
/// <param name="assetRepository">Asset repository.</param>
/// <param name="signKeyOptions">JWT signing key configuration.</param>
[ApiController]
[Authorize]
[AllowAnonymous]
[Route("api/[controller]")]
public class MediaController(
    LactoseAuthService authService,
    IMediaRepository mediaRepository,
    IAssetRepository assetRepository,
    IOptions<SignKeyConfiguration> signKeyOptions
) : ControllerBase {

    /// <summary>
    /// Gets the original image file for an asset.
    /// </summary>
    /// <param name="id">The asset ID.</param>
    /// <returns>The physical image file, or 404 if not found or access denied.</returns>
    [HttpGet("{id}")]
    [HttpGet("original/{id}")]
    [EnableRateLimiting("media_original")]
    public ActionResult GetImage(Guid id) {
        var user = GetUserFromRequest();
        var asset = assetRepository.Find(id);
        
        if (asset == null) return NotFound();

        if (CanAccessAssetDirectly(user, asset.DeletedAt)) {
            return PhysicalFile(asset.OriginalPath, asset.MimeType);
        }
        var data = mediaRepository.GetOriginalData(id, user?.Id, user?.AccessLevel ?? EAccessLevel.User);
        if (data == null) return NotFound();

        return PhysicalFile(data.Path, data.MimeType);
    }

    /// <summary>
    /// Gets the thumbnail image for an asset.
    /// </summary>
    /// <param name="id">The asset ID.</param>
    /// <returns>The physical thumbnail file, or 404 if not found or access denied.</returns>
    [HttpGet("thumb/{id}")]
    [EnableRateLimiting("media_thumb")]
    public ActionResult GetThumb(Guid id) {
        var user  = GetUserFromRequest();
        var asset = assetRepository.Find(id);
        
        if (asset == null) return NotFound();

        // Thumbnails are immutable per asset — allow browser/proxy caching
        Response.Headers.CacheControl = "public, max-age=86400";

        if (CanAccessAssetDirectly(user, asset.DeletedAt)) {
            if (string.IsNullOrEmpty(asset.ThumbnailPath)) return NotFound();
            return PhysicalFile(asset.ThumbnailPath, "image/webp");
        }
        var data = mediaRepository.GetThumbData(id, user?.Id, user?.AccessLevel ?? EAccessLevel.User);
        if (data == null) return NotFound();

        return PhysicalFile(data.Path, data.MimeType);
    }

    /// <summary>
    /// Gets the preview image for an asset.
    /// </summary>
    /// <param name="id">The asset ID.</param>
    /// <returns>The physical preview file, or 404 if not found or access denied.</returns>
    [HttpGet("preview/{id}")]
    [EnableRateLimiting("media_preview")]
    public ActionResult GetPreview(Guid id) {
        var user  = GetUserFromRequest();
        var asset = assetRepository.Find(id);
        
        if (asset == null) return NotFound();

        // Previews are immutable per asset — allow browser/proxy caching
        Response.Headers.CacheControl = "public, max-age=86400";

        if (CanAccessAssetDirectly(user, asset.DeletedAt)) {
            if (string.IsNullOrEmpty(asset.PreviewPath)) return NotFound();
            return PhysicalFile(asset.PreviewPath, "image/webp");
        }
        var data = mediaRepository.GetPreviewData(id, user?.Id, user?.AccessLevel ?? EAccessLevel.User);
        if (data == null) return NotFound();

        return PhysicalFile(data.Path, data.MimeType);
    }

    /// <summary>
    /// Extracts the authenticated user from the request, first trying the Authorization header,
    /// then falling back to the <c>token</c> query parameter for browser image requests.
    /// </summary>
    private LactoseAuthenticatedUser? GetUserFromRequest() {
        var user = authService.GetUserData(User);
        if (user != null) return user;

        var token = Request.Query["token"].FirstOrDefault();
        if (string.IsNullOrEmpty(token)) return null;

        try {
            var handler = new JwtSecurityTokenHandler();
            var key = signKeyOptions.Value.GetSecurityKey();
            var principal = handler.ValidateToken(token, new TokenValidationParameters {
                IssuerSigningKey = key,
                ValidateIssuer = false,
                ValidateAudience = false,
                ValidateLifetime = true
            }, out _);
            return authService.GetUserData(principal);
        } catch {
            return null;
        }
    }

    /// <summary>
    /// Determines whether the requester can access asset files directly without repository-level filtering.
    /// </summary>
    /// <param name="user">The authenticated user, if any.</param>
    /// <param name="deletedAt">The asset deletion timestamp.</param>
    /// <returns><see langword="true"/> for admins, or for curators when the asset is not deleted; otherwise <see langword="false"/>.</returns>
    private static bool CanAccessAssetDirectly(LactoseAuthenticatedUser? user, DateTime? deletedAt) {
        return user?.AccessLevel switch {
            EAccessLevel.Admin => true,
            EAccessLevel.Curator => deletedAt == null,
            _ => false
        };
    }
}