feat: add configuration package with YAML loading and defaults

Add config package that loads game settings from YAML files with
sensible defaults for server, game, combat, dungeon, and backup
settings. Includes config.yaml with all defaults documented.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

config.yaml

@@ -0,0 +1,44 @@
+# Catacombs Configuration
+# All values shown are defaults. Uncomment and modify as needed.
+
+server:
+  # SSH port for game client connections
+  ssh_port: 2222
+  # HTTP port for web interface
+  http_port: 8080
+
+game:
+  # Seconds allowed per player turn
+  turn_timeout_sec: 5
+  # Maximum players per game session
+  max_players: 4
+  # Maximum dungeon floors
+  max_floors: 20
+  # Cooperative play bonus multiplier
+  coop_bonus: 0.10
+  # Maximum items a player can carry
+  inventory_limit: 10
+  # Number of skill uses per floor
+  skill_uses: 3
+
+combat:
+  # Probability of successfully fleeing combat
+  flee_chance: 0.50
+  # Monster stat scaling per floor
+  monster_scaling: 1.15
+  # HP reduction when playing solo
+  solo_hp_reduction: 0.50
+
+dungeon:
+  # Map dimensions in tiles
+  map_width: 60
+  map_height: 20
+  # Room count range per floor
+  min_rooms: 5
+  max_rooms: 8
+
+backup:
+  # Minutes between automatic backups
+  interval_min: 60
+  # Directory for backup files
+  dir: "./data/backup"

config/config.go

@@ -0,0 +1,75 @@
+package config
+
+import (
+	"os"
+
+	"gopkg.in/yaml.v3"
+)
+
+type Config struct {
+	Server  ServerConfig  `yaml:"server"`
+	Game    GameConfig    `yaml:"game"`
+	Combat  CombatConfig  `yaml:"combat"`
+	Dungeon DungeonConfig `yaml:"dungeon"`
+	Backup  BackupConfig  `yaml:"backup"`
+}
+
+type ServerConfig struct {
+	SSHPort  int `yaml:"ssh_port"`
+	HTTPPort int `yaml:"http_port"`
+}
+
+type GameConfig struct {
+	TurnTimeoutSec int     `yaml:"turn_timeout_sec"`
+	MaxPlayers     int     `yaml:"max_players"`
+	MaxFloors      int     `yaml:"max_floors"`
+	CoopBonus      float64 `yaml:"coop_bonus"`
+	InventoryLimit int     `yaml:"inventory_limit"`
+	SkillUses      int     `yaml:"skill_uses"`
+}
+
+type CombatConfig struct {
+	FleeChance      float64 `yaml:"flee_chance"`
+	MonsterScaling  float64 `yaml:"monster_scaling"`
+	SoloHPReduction float64 `yaml:"solo_hp_reduction"`
+}
+
+type DungeonConfig struct {
+	MapWidth  int `yaml:"map_width"`
+	MapHeight int `yaml:"map_height"`
+	MinRooms  int `yaml:"min_rooms"`
+	MaxRooms  int `yaml:"max_rooms"`
+}
+
+type BackupConfig struct {
+	IntervalMin int    `yaml:"interval_min"`
+	Dir         string `yaml:"dir"`
+}
+
+func defaults() Config {
+	return Config{
+		Server: ServerConfig{SSHPort: 2222, HTTPPort: 8080},
+		Game: GameConfig{
+			TurnTimeoutSec: 5, MaxPlayers: 4, MaxFloors: 20,
+			CoopBonus: 0.10, InventoryLimit: 10, SkillUses: 3,
+		},
+		Combat: CombatConfig{FleeChance: 0.50, MonsterScaling: 1.15, SoloHPReduction: 0.50},
+		Dungeon: DungeonConfig{MapWidth: 60, MapHeight: 20, MinRooms: 5, MaxRooms: 8},
+		Backup: BackupConfig{IntervalMin: 60, Dir: "./data/backup"},
+	}
+}
+
+func Load(path string) (*Config, error) {
+	cfg := defaults()
+	if path == "" {
+		return &cfg, nil
+	}
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return nil, err
+	}
+	if err := yaml.Unmarshal(data, &cfg); err != nil {
+		return nil, err
+	}
+	return &cfg, nil
+}

config/config_test.go

@@ -0,0 +1,85 @@
+package config
+
+import (
+	"os"
+	"testing"
+)
+
+func TestLoadDefaults(t *testing.T) {
+	cfg, err := Load("")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if cfg.Server.SSHPort != 2222 {
+		t.Errorf("expected SSH port 2222, got %d", cfg.Server.SSHPort)
+	}
+	if cfg.Server.HTTPPort != 8080 {
+		t.Errorf("expected HTTP port 8080, got %d", cfg.Server.HTTPPort)
+	}
+	if cfg.Game.TurnTimeoutSec != 5 {
+		t.Errorf("expected turn timeout 5, got %d", cfg.Game.TurnTimeoutSec)
+	}
+	if cfg.Game.MaxPlayers != 4 {
+		t.Errorf("expected max players 4, got %d", cfg.Game.MaxPlayers)
+	}
+	if cfg.Game.MaxFloors != 20 {
+		t.Errorf("expected max floors 20, got %d", cfg.Game.MaxFloors)
+	}
+	if cfg.Game.CoopBonus != 0.10 {
+		t.Errorf("expected coop bonus 0.10, got %f", cfg.Game.CoopBonus)
+	}
+	if cfg.Game.InventoryLimit != 10 {
+		t.Errorf("expected inventory limit 10, got %d", cfg.Game.InventoryLimit)
+	}
+	if cfg.Combat.FleeChance != 0.50 {
+		t.Errorf("expected flee chance 0.50, got %f", cfg.Combat.FleeChance)
+	}
+	if cfg.Combat.MonsterScaling != 1.15 {
+		t.Errorf("expected monster scaling 1.15, got %f", cfg.Combat.MonsterScaling)
+	}
+}
+
+func TestLoadFromFile(t *testing.T) {
+	content := []byte(`
+server:
+  ssh_port: 3333
+  http_port: 9090
+game:
+  turn_timeout_sec: 10
+  max_players: 2
+`)
+	f, err := os.CreateTemp("", "config-*.yaml")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.Remove(f.Name())
+	f.Write(content)
+	f.Close()
+
+	cfg, err := Load(f.Name())
+	if err != nil {
+		t.Fatal(err)
+	}
+	if cfg.Server.SSHPort != 3333 {
+		t.Errorf("expected SSH port 3333, got %d", cfg.Server.SSHPort)
+	}
+	if cfg.Server.HTTPPort != 9090 {
+		t.Errorf("expected HTTP port 9090, got %d", cfg.Server.HTTPPort)
+	}
+	if cfg.Game.TurnTimeoutSec != 10 {
+		t.Errorf("expected turn timeout 10, got %d", cfg.Game.TurnTimeoutSec)
+	}
+	if cfg.Game.MaxPlayers != 2 {
+		t.Errorf("expected max players 2, got %d", cfg.Game.MaxPlayers)
+	}
+	// Unset fields should have defaults
+	if cfg.Game.MaxFloors != 20 {
+		t.Errorf("expected default max floors 20, got %d", cfg.Game.MaxFloors)
+	}
+	if cfg.Combat.FleeChance != 0.50 {
+		t.Errorf("expected default flee chance 0.50, got %f", cfg.Combat.FleeChance)
+	}
+	if cfg.Dungeon.MapWidth != 60 {
+		t.Errorf("expected default map width 60, got %d", cfg.Dungeon.MapWidth)
+	}
+}

go.mod

@@ -41,4 +41,5 @@ require (
 	golang.org/x/exp v0.0.0-20240719175910-8a7402abbf56 // indirect
 	golang.org/x/sys v0.36.0 // indirect
 	golang.org/x/text v0.23.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
 )

go.sum

@@ -79,5 +79,6 @@ golang.org/x/term v0.30.0 h1:PQ39fJZ+mfadBm0y5WlL4vlM7Sx1Hgf13sMIY2+QS9Y=
 golang.org/x/term v0.30.0/go.mod h1:NYYFdzHoI5wRh/h5tDMdMqCqPJZEuNqVR5xJLd/n67g=
 golang.org/x/text v0.23.0 h1:D71I7dUrlY+VX0gQShAThNGHFxZ13dGLBHQLVl1mJlY=
 golang.org/x/text v0.23.0/go.mod h1:/BLNzu4aZCJ1+kcD0DNRotWKage4q2rGVAg4o22unh4=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=