From 996007f84ef833fce6ea7d94183bb84a511129e2 Mon Sep 17 00:00:00 2001
From: Eduard Urbach <e.urbach@gmail.com>
Date: Tue, 27 Mar 2018 10:13:27 +0200
Subject: [PATCH] Improved recommendations

---
 pages/recommended/anime.go | 59 ++++++++++++++++++++++++++++++++++++--
 1 file changed, 56 insertions(+), 3 deletions(-)

diff --git a/pages/recommended/anime.go b/pages/recommended/anime.go
index 4cca829e..0ae74fed 100644
--- a/pages/recommended/anime.go
+++ b/pages/recommended/anime.go
@@ -1,6 +1,8 @@
 package recommended
 
 import (
+	"fmt"
+	"math"
 	"net/http"
 	"sort"
 
@@ -11,7 +13,9 @@ import (
 )
 
 const (
-	maxRecommendations = 10
+	maxRecommendations                = 10
+	bestGenreCount                    = 3
+	genreBonusCompletedAnimeThreshold = 40
 )
 
 // Anime shows a list of recommended anime.
@@ -25,6 +29,41 @@ func Anime(ctx *aero.Context) string {
 	}
 
 	animeList := viewUser.AnimeList()
+	completed := animeList.FilterStatus(arn.AnimeListStatusCompleted)
+
+	// Genre affinity
+	genreItems := animeList.Genres()
+	genreAffinity := map[string]float64{}
+	bestGenres := []string{}
+
+	for genre, animeListItems := range genreItems {
+		affinity := 0.0
+
+		for _, item := range animeListItems {
+			if item.Status != arn.AnimeListStatusCompleted {
+				continue
+			}
+
+			if item.Rating.Overall != 0 {
+				affinity += item.Rating.Overall
+			} else {
+				affinity += 5.0
+			}
+		}
+
+		genreAffinity[genre] = affinity
+		bestGenres = append(bestGenres, genre)
+	}
+
+	sort.Slice(bestGenres, func(i, j int) bool {
+		return genreAffinity[bestGenres[i]] > genreAffinity[bestGenres[j]]
+	})
+
+	if len(bestGenres) > bestGenreCount {
+		bestGenres = bestGenres[:bestGenreCount]
+	}
+
+	fmt.Println(bestGenres)
 
 	// Get all anime
 	var tv []*arn.Anime
@@ -65,18 +104,32 @@ func Anime(ctx *aero.Context) string {
 		prequels := anime.Prequels()
 
 		for _, prequel := range prequels {
-			item := animeList.Find(prequel.ID)
+			item := completed.Find(prequel.ID)
 
 			// Filter out unimportant prequels
 			if prequel.Score() < anime.Score()/2 {
 				continue
 			}
 
-			if item == nil || item.Status != arn.AnimeListStatusCompleted {
+			if item == nil {
 				animeAffinity -= 20.0
 			}
 		}
 
+		// Give favorite genre bonus if we have enough completed anime
+		if len(completed.Items) >= genreBonusCompletedAnimeThreshold {
+			bestGenreCount := 0
+
+			for _, genre := range anime.Genres {
+				if arn.Contains(bestGenres, genre) {
+					bestGenreCount++
+				}
+			}
+
+			// Use square root to dampen the bonus of additional best genres
+			animeAffinity += math.Sqrt(float64(bestGenreCount)) * 7.0
+		}
+
 		affinity[anime.ID] = animeAffinity
 	}