Added media limit sampling.

src/media.js

@@ -1,13 +1,12 @@
 'use strict';
 
 const config = require('config');
-// const util = require('util');
 const Promise = require('bluebird');
 const fs = require('fs').promises;
 const path = require('path');
 const nanoid = require('nanoid/non-secure');
 const mime = require('mime');
-const fileType = require('file-type');
+// const fileType = require('file-type');
 const sharp = require('sharp');
 const blake2 = require('blake2');
 
@@ -72,6 +71,60 @@ async function getThumbnail(buffer, height = config.media.thumbnailSize) {
     return null;
 }
 
+function sampleMedias(medias, limit = config.media.limit, preferLast = true) {
+    // limit media sets, use extrax as fallbacks
+    if (medias.length <= limit) {
+        return medias;
+    }
+
+    const chunkSize = Math.floor(medias.length / limit);
+    const rest = medias.length - (limit * chunkSize);
+
+    const chunks = Array.from(
+        { length: limit },
+        (value, index) => {
+            const start = (chunkSize * index) + Math.min(index, rest);
+
+            return medias.slice(
+                start,
+                start + chunkSize + (index < rest ? 1 : 0),
+            );
+        },
+    );
+
+    // flip last chunk so the very last image (often the best cumshot) is tried first
+    const lastPreferredChunks = preferLast
+        ? chunks.slice(0, -1).concat(chunks.slice(-1).reverse())
+        : chunks;
+
+    const groupedMedias = lastPreferredChunks.map((chunk) => {
+        // merge chunked medias into single media with grouped fallback priorities,
+        // so the first sources of each media is preferred over all second sources, etc.
+        const sources = chunk
+            .reduce((accSources, media) => {
+                media.sources.forEach((source, index) => {
+                    if (!accSources[index]) {
+                        accSources.push([source]);
+                        return;
+                    }
+
+                    accSources[index].push(source);
+                });
+
+                return accSources;
+            }, [])
+            .flat();
+
+        return {
+            id: chunk[0].id,
+            role: chunk[0].role,
+            sources,
+        };
+    });
+
+    return groupedMedias;
+}
+
 function itemsByKey(items, key) {
     return items.reduce((acc, item) => ({ ...acc, [item[key]]: item }), {});
 }
@@ -143,7 +196,7 @@ function toBaseMedias(rawMedias, role) {
         return [];
     }
 
-    return rawMedias.map((rawMedia) => {
+    const baseMedias = rawMedias.map((rawMedia) => {
         if (!rawMedia) {
             return null;
         }
@@ -157,6 +210,10 @@ function toBaseMedias(rawMedias, role) {
 
         return baseSourceToBaseMedia(baseSource, role);
     }).filter(Boolean);
+
+    const sampledBaseMedias = sampleMedias(baseMedias);
+
+    return sampledBaseMedias;
 }
 
 async function findSourceDuplicates(baseMedias) {
@@ -465,7 +522,6 @@ async function associateReleaseMedia(releases) {
         return;
     }
 
-    // TODO: media count limits
     // TODO: catch errors
     // TODO: stage by role