1 files changed, 155 insertions, 0 deletions
diff --git a/Services/FeedService.cs b/Services/FeedService.cs
new file mode 100644
index 0000000..864a751
--- /dev/null
+++ b/Services/FeedService.cs
@@ -0,0 +1,155 @@
+using Microsoft.EntityFrameworkCore;
+
+namespace HyperBooru.Services;
+
+public interface IFeedService {
+    public Media[] LoadChunk(
+        bool selectIngest,
+        bool includeNsfw,
+        Media? key = null,
+        int count = 50);
+
+    public Media[] LoadChunk(
+        bool selectIngest,
+        bool includeNsfw,
+        string query,
+        Media? key = null,
+        int count = 50);
+
+    public Media[] LoadChunk(
+        bool selectIngest,
+        bool includeNsfw,
+        Guid tagId,
+        Media? key = null,
+        int count = 50);
+}
+
+public class FeedService : IFeedService {
+    private IDbContextFactory<HBContext> dbFactory;
+
+    public FeedService(IDbContextFactory<HBContext> dbFactory) =>
+        this.dbFactory = dbFactory;
+
+    public Media[] LoadChunk(
+        bool selectIngest,
+        bool includeNsfw,
+        Media? key,
+        int count) => LoadChunkInternal(selectIngest, includeNsfw, null, null, key, count);
+
+    public Media[] LoadChunk(
+        bool selectIngest,
+        bool includeNsfw,
+        string query,
+        Media? key,
+        int count) => LoadChunkInternal(selectIngest, includeNsfw, query, null, key, count);
+
+    public Media[] LoadChunk(
+        bool selectIngest,
+        bool includeNsfw,
+        Guid tagId,
+        Media? key,
+        int count) => LoadChunkInternal(selectIngest, includeNsfw, null, tagId, key, count);
+
+    private Media[] LoadChunkInternal(
+        bool selectIngest,
+        bool includeNsfw,
+        string? query,
+        Guid? tagId,
+        Media? key,
+        int count) {
+
+        if(selectIngest && !includeNsfw)
+            return Array.Empty<Media>();
+
+        using var db = dbFactory.CreateDbContext();
+
+        IQueryable<Media> media = db.Media
+            .AsSingleQuery()
+            .AsNoTracking()
+            .Include(m => m.Tags)
+            .Include(m => m.CurrentUploadedFile);
+
+        if(!includeNsfw)
+            media = media
+                .Where(m => !TagsThatImply(db, HBContext.NsfwTag)
+                    .Intersect(m.Tags.Select(t => t.TagDefinitionId))
+                    .Any());
+
+        if(selectIngest) {
+            media = media
+                .Where(m => m.Tags
+                    .Select(t => t.TagDefinitionId)
+                        .Contains((int) HBObjectId.IngestTag));
+        } else {
+            media = media
+                .Where(m => !m.Tags
+                    .Select(t => t.TagDefinitionId)
+                        .Contains((int) HBObjectId.IngestTag));
+        }
+
+        if(query is not null) {
+            media = Search(media, query);
+        } else if(tagId is not null) {
+            media = media
+                .Where(m => TagsThatImply(db, (Guid) tagId)
+                    .Intersect(m.Tags.Select(t => t.TagDefinitionId))
+                    .Any());
+        }
+
+        if(key is not null)
+            media = media.Where(m => m.ObjectId > key.ObjectId);
+
+        return media
+            .OrderBy(m => m.ObjectId)
+            .Take(count)
+            .ToArray();
+    }
+
+    private static IQueryable<Media> Search(IQueryable<Media> media, string query) {
+        // TODO: search implicit tags as well
+
+        query = query.ToLower().Trim();
+
+        return media
+            .Where(m =>
+                (m.ShortDescription != null && m.ShortDescription.ToLower().Contains(query)) ||
+                (m.LongDescription != null && m.LongDescription.ToLower().Contains(query)) ||
+                (m.UploadedFiles.Any(uf => uf.Filename != null && uf.Filename.ToLower().Contains(query))) ||
+                (m.OcrData != null && m.OcrData.SearchableText.ToLower().Contains(query)) ||
+                (m.Tags.Any(t => t.TagDefinition.Name.ToLower().Contains(query))));
+    }
+
+    private static IQueryable<int> TagsThatImply(HBContext db, Guid tagId) =>
+        db.Database.SqlQueryRaw<int>("""
+            WITH RECURSIVE basetag AS (
+                SELECT "ObjectId" FROM "Objects" WHERE "Guid" = {0}
+            ),
+            impliedtags AS (
+                    SELECT
+                        "TagDefinitionObjectId"
+                    FROM
+                        "TagDefinitionTagDefinition"
+                    INNER JOIN
+                        basetag
+                    ON
+                        "ImplicitTagsObjectId" = basetag."ObjectId"
+                UNION
+                    SELECT
+                        "TagDefinitionTagDefinition"."TagDefinitionObjectId"
+                    FROM
+                        "TagDefinitionTagDefinition"
+                    INNER JOIN
+                        impliedtags
+                    ON
+                        impliedtags."TagDefinitionObjectId" = "TagDefinitionTagDefinition"."ImplicitTagsObjectId"
+            )
+                SELECT DISTINCT
+                    "TagDefinitionObjectId" AS "Value"
+                FROM impliedtags
+            UNION
+                SELECT
+                    "ObjectId" AS "Value"
+                FROM
+                    basetag
+            """, tagId);
+}