Refactor code structure for improved readability and maintainability

app/models/playlist_sound.py

@@ -0,0 +1,37 @@
+from typing import TYPE_CHECKING
+
+from sqlmodel import Field, Relationship, UniqueConstraint
+
+from app.models.base import BaseModel
+
+if TYPE_CHECKING:
+    from app.models.playlist import Playlist
+    from app.models.sound import Sound
+
+
+class PlaylistSound(BaseModel, table=True):
+    """Database model for a sound in a playlist."""
+
+    __tablename__ = "playlist_sound"  # pyright: ignore[reportAssignmentType]
+
+    playlist_id: int = Field(foreign_key="playlist.id", nullable=False)
+    sound_id: int = Field(foreign_key="sound.id", nullable=False)
+    position: int = Field(default=0, ge=0, nullable=False)
+
+    # constraints
+    __table_args__ = (
+        UniqueConstraint(
+            "playlist_id",
+            "sound_id",
+            name="uq_playlist_sound_playlist_sound",
+        ),
+        UniqueConstraint(
+            "playlist_id",
+            "position",
+            name="uq_playlist_sound_playlist_position",
+        ),
+    )
+
+    # relationships
+    playlist: "Playlist" = Relationship(back_populates="playlist_sounds")
+    sound: "Sound" = Relationship(back_populates="playlist_sounds")