Add song ranks, improve non-S rating calculation

titles/chuni/frontend.py

@@ -13,6 +13,69 @@ from .config import ChuniConfig
 from .const import ChuniConstants
 
 
+def pairwise(iterable):
+    # https://docs.python.org/3/library/itertools.html#itertools.pairwise
+    # but for Python < 3.10. pairwise('ABCDEFG') → AB BC CD DE EF FG
+    iterator = iter(iterable)
+    a = next(iterator, None)
+    for b in iterator:
+        yield a, b
+        a = b
+
+
+def calculate_song_rank(score: int, game_version: int) -> str:
+    if game_version >= ChuniConstants.VER_CHUNITHM_NEW:
+        intervals = ChuniConstants.SCORE_RANK_INTERVALS_NEW
+    else:
+        intervals = ChuniConstants.SCORE_RANK_INTERVALS_OLD
+
+    for (min_score, rank) in intervals:
+        if score >= min_score:
+            return rank
+
+    return "D"
+
+
+def calculate_song_rating(score: int, chart_constant: float, game_version: int) -> float:
+    is_new = game_version >= ChuniConstants.VER_CHUNITHM_NEW
+
+    if is_new:  # New and later
+        max_score = 1009000
+        max_rating_modifier = 2.15
+    else:  # Up to Paradise Lost
+        max_score = 1007500
+        max_rating_modifier = 2.0
+
+    if (score < 500000):
+        return 0.0  # D
+    elif (score >= max_score):
+        return chart_constant + max_rating_modifier  # SSS/SSS+
+
+    # Okay, we're doing this the hard way.
+    # Rating goes up linearly between breakpoints listed below.
+    # Pick the score interval in which we are in, then calculate
+    # the position between possible ratings.
+    score_intervals = [
+        ( 500000, 0.0),  # C
+        ( 800000, max(0.0, (chart_constant - 5.0) / 2)),  # BBB
+        ( 900000, max(0.0, (chart_constant - 5.0))),  # A
+        ( 925000, max(0.0, (chart_constant - 3.0))),  # AA
+        ( 975000, chart_constant),  # S
+        (1000000, chart_constant + 1.0),  # SS
+        (1005000, chart_constant + 1.5),  # SS+
+        (1007500, chart_constant + 2.0),  # SSS
+        (1009000, chart_constant + max_rating_modifier),  # SSS+!
+    ]
+
+    for ((lo_score, lo_rating), (hi_score, hi_rating)) in pairwise(score_intervals):
+        if not (lo_score <= score < hi_score):
+            continue
+
+        interval_pos = (score - lo_score) / (hi_score - lo_score)
+        return lo_rating + ((hi_rating - lo_rating) * interval_pos)
+
+
+
 class ChuniFrontend(FE_Base):
     def __init__(
         self, cfg: CoreConfig, environment: jinja2.Environment, cfg_dir: str
@@ -91,37 +154,27 @@ class ChuniFrontend(FE_Base):
             base_list=[]
             if profile and rating:
                 song_records = []
+
                 for song in rating:
                     music_chart = await self.data.static.get_music_chart(usr_sesh.chunithm_version, song.musicId, song.difficultId)
-                    if music_chart:
-                        if (song.score < 800000):
-                            song_rating = 0
-                        elif (song.score >= 800000 and song.score < 900000):
-                            song_rating = music_chart.level / 2 - 5
-                        elif (song.score >= 900000 and song.score < 925000):
-                            song_rating = music_chart.level - 5
-                        elif (song.score >= 925000 and song.score < 975000):
-                            song_rating = music_chart.level - 3
-                        elif (song.score >= 975000 and song.score < 1000000):
-                            song_rating = (song.score - 975000) / 2500 * 0.1 + music_chart.level
-                        elif (song.score >= 1000000 and song.score < 1005000):
-                            song_rating = (song.score - 1000000) / 1000 * 0.1 + 1 + music_chart.level
-                        elif (song.score >= 1005000 and song.score < 1007500):
-                            song_rating = (song.score - 1005000) / 500 * 0.1 + 1.5 + music_chart.level
-                        elif (song.score >= 1007500 and song.score < 1009000):
-                            song_rating = (song.score - 1007500) / 100 * 0.01 + 2 + music_chart.level
-                        elif (song.score >= 1009000):
-                            song_rating = 2.15 + music_chart.level
-                        song_rating = int(song_rating * 10 ** 2) / 10 ** 2
-                        song_records.append({
-                            "difficultId": song.difficultId,
-                            "musicId": song.musicId,
-                            "title": music_chart.title,
-                            "level": music_chart.level,
-                            "score": song.score,
-                            "type": song.type,
-                            "song_rating": song_rating,
-                        })
+                    if not music_chart:
+                        continue
+
+                    rank = calculate_song_rank(song.score, profile.version)
+                    rating = calculate_song_rating(song.score, music_chart.level, profile.version)
+
+                    song_rating = int(rating * 10 ** 2) / 10 ** 2
+                    song_records.append({
+                        "difficultId": song.difficultId,
+                        "musicId": song.musicId,
+                        "title": music_chart.title,
+                        "level": music_chart.level,
+                        "score": song.score,
+                        "type": song.type,
+                        "rank": rank,
+                        "song_rating": song_rating,
+                    })
+
                 hot_list = [obj for obj in song_records if obj["type"] == "userRatingBaseHotList"]
                 base_list = [obj for obj in song_records if obj["type"] == "userRatingBaseList"]
             return Response(template.render(
@@ -243,4 +296,4 @@ class ChuniFrontend(FE_Base):
                 resp.set_cookie("ARTEMIS_SESH", encoded_sesh)
             return resp
         else:
-            return RedirectResponse("/gate/", 303)
+            return RedirectResponse("/gate/", 303)