refactor: deduplicate persistence, add upsert queries, throttle snake saves

- Replace Create+Get+Update with UpsertGame/UpsertSnakeGame queries
- Extract free functions (saveGame, loadGame, etc.) from duplicated
  receiver methods on Store and Instance types
- Remove duplicate generateID from snake package, reuse game.GenerateID
- Throttle snake game DB writes to every 2s instead of every tick
- Fix double-lock in c4game chat handler
- Update all code for sqlc pointer types (*string instead of sql.NullString)

snake/store.go

@@ -2,11 +2,10 @@ package snake
 
 import (
 	"context"
-	"crypto/rand"
-	"encoding/hex"
 	"sync"
 
 	"github.com/ryanhamamura/c4/db/repository"
+	"github.com/ryanhamamura/c4/game"
 )
 
 type SnakeStore struct {
@@ -39,7 +38,7 @@ func (ss *SnakeStore) Create(width, height int, mode GameMode, speed int) *Snake
 	if speed <= 0 {
 		speed = DefaultSpeed
 	}
-	id := generateID(4)
+	id := game.GenerateID(4)
 	sg := &SnakeGame{
 		ID: id,
 		State: &GameState{
@@ -63,7 +62,7 @@ func (ss *SnakeStore) Create(width, height int, mode GameMode, speed int) *Snake
 	ss.gamesMu.Unlock()
 
 	if ss.queries != nil {
-		ss.saveSnakeGame(sg) //nolint:errcheck
+		saveSnakeGame(ss.queries, sg) //nolint:errcheck
 	}
 
 	return si
@@ -82,12 +81,12 @@ func (ss *SnakeStore) Get(id string) (*SnakeGameInstance, bool) {
 		return nil, false
 	}
 
-	sg, err := ss.loadSnakeGame(id)
+	sg, err := loadSnakeGame(ss.queries, id)
 	if err != nil || sg == nil {
 		return nil, false
 	}
 
-	players, _ := ss.loadSnakePlayers(id)
+	players, _ := loadSnakePlayers(ss.queries, id)
 	if sg.Players == nil {
 		sg.Players = make([]*Player, 8)
 	}
@@ -207,8 +206,8 @@ func (si *SnakeGameInstance) Join(player *Player) bool {
 	si.game.Players[slot] = player
 
 	if si.queries != nil {
-		si.saveSnakePlayer(si.game.ID, player) //nolint:errcheck
-		si.saveSnakeGame(si.game)              //nolint:errcheck
+		saveSnakePlayer(si.queries, si.game.ID, player) //nolint:errcheck
+		saveSnakeGame(si.queries, si.game)              //nolint:errcheck
 	}
 
 	si.notify()
@@ -294,16 +293,10 @@ func (si *SnakeGameInstance) CreateRematch() *SnakeGameInstance {
 	si.game.RematchGameID = &newID
 
 	if si.queries != nil {
-		si.saveSnakeGame(si.game) //nolint:errcheck
+		saveSnakeGame(si.queries, si.game) //nolint:errcheck
 	}
 	si.gameMu.Unlock()
 
 	si.notify()
 	return newSI
 }
-
-func generateID(size int) string {
-	b := make([]byte, size)
-	_, _ = rand.Read(b)
-	return hex.EncodeToString(b)
-}