Optimizely DAM alt text helper for Optimizely CMS 12

DamAltTextHelper.cs

using EPiServer.Cms.WelcomeIntegration.Core;
using EPiServer.Cms.WelcomeIntegration.Core.Internal;
using EPiServer.Cms.WelcomeIntegration.UI;
using EPiServer.Cms.WelcomeIntegration.UI.Internal;
using Microsoft.Extensions.Caching.Memory;
using Microsoft.Extensions.Options;
using Optimizely.Cmp.Client;

namespace OptimzelyDamHelpers;

// Add following to Startup.cs in ConfigureServices(IServiceCollection services)
//
//    services.AddSingleton<IDamAltTextHelper, DamAltTextHelper>();
//

public interface IDamAltTextHelper
{
    string GetAltText(DAMImageAsset damImageAsset);
    string GetAltText(ContentReference damContentReference);
}

public class DamAltTextHelper : IDamAltTextHelper
{
    private readonly IDAMAssetIdentityResolver _damAssetIdResolver;
    private readonly IDAMAssetMetadataService _damMetadataService;
    private readonly ICmpClient _cmpClient;
    private readonly IMemoryCache _cache;
    private readonly IOptions<DAMUiOptions> _damUiOptions;

    private const string AltTextKey = "alt_text";

    public DamAltTextHelper(IDAMAssetIdentityResolver damAssetIdResolver, IDAMAssetMetadataService damMetadataService, ICmpClient cmpClient, IMemoryCache cache, IOptions<DAMUiOptions> damUiOptions)
    {
        _damAssetIdResolver = damAssetIdResolver;
        _damMetadataService = damMetadataService;
        _cmpClient = cmpClient;
        _cache = cache;
        _damUiOptions = damUiOptions;
    }

    public string GetAltText(DAMImageAsset damImageAsset)
    {
        return GetAltText(damImageAsset.ContentLink);
    }

    public string GetAltText(ContentReference damContentReference)
    {
        // If this isn't an asset selected from the DAM, ignore
        if (damContentReference == null || damContentReference.ProviderName != "dam")
            return string.Empty;

        // Attempt to retrieve resolve the asset identity
        var assetIdentity = _damAssetIdResolver.Get(damContentReference);
        if (assetIdentity == null) return string.Empty;

        // Check if the Guid can be retrieved
        var assetId = assetIdentity.GetAssetId();
        if (!Guid.TryParse(assetId, out var assetGuid))
            return string.Empty;


        // Use a service to retrieve the alt text, these requests are cached but
        // bear in mind that this generates an API request to Optimizely CMP/DAM
        Dictionary<string, object?> assetMetadata;

        if (IsRendition(assetIdentity))
        {
            assetMetadata = GetRenditionMetaData(assetGuid).Result;
        }
        else
        {
            assetMetadata = _damMetadataService.GetAssetMetadata(assetGuid).Result;
        }

        if (assetMetadata.Keys.Count > 0 &&
            assetMetadata.ContainsKey(AltTextKey) &&
            !string.IsNullOrEmpty(assetMetadata[AltTextKey]?.ToString()))
        {
            // Return the alt text
            return assetMetadata[AltTextKey].ToString();
        }

        return string.Empty;
    }

    public async Task<Dictionary<string, object?>> GetRenditionMetaData(Guid id)
    {
        var result = await _cache.GetOrCreateAsync(id.ToString(), async factory =>
        {
            var data = await _cmpClient.SendAsync<Dictionary<string, object?>>($"renditions/{id:N}", HttpMethod.Get, null);
            factory.AbsoluteExpirationRelativeToNow = _damUiOptions.Value.AssetMetadataCacheExpiration;
            return data;
        });

        return result ?? new Dictionary<string, object?>();
    }

    public bool IsRendition(DAMAssetIdentity assetIdentity)
    {
        var assetEncodedId = assetIdentity.DAMAssetUri.Segments.Last();
        return Guid.TryParse(assetEncodedId, out _);
    }
}