feat: integrate config system into relay main.go

Add support for loading configuration from YAML file via -config flag.
Wire up auth, rate limiting, and metrics interceptors based on config.

Changes:
- Add -config flag to relay command
- Use config types directly in auth package (AuthOperationConfig)
- Add conversion methods: RateLimitConfig.ToRateLimiter(), MetricsConfig.ToMetrics()
- Add Metrics.Serve() method for prometheus HTTP endpoint
- Update main.go to initialize interceptors from config
- Fix type naming: OperationAuthConfig -> AuthOperationConfig for consistency

Config now supports complete relay setup including auth read/write
allowlists, rate limiting, and prometheus metrics.

1 files changed, 61 insertions, 14 deletions

diff --git a/internal/config/config.go b/internal/config/config.go
index 36c8be5..dcceade 100644
--- a/internal/config/config.go
+++ b/internal/config/config.go
@@ -7,6 +7,9 @@ import (
         "time"
 
         "gopkg.in/yaml.v3"
+        "northwest.io/muxstr/internal/auth"
+        "northwest.io/muxstr/internal/metrics"
+        "northwest.io/muxstr/internal/ratelimit"
         "northwest.io/nostr"
 )
 
@@ -33,18 +36,10 @@ type DatabaseConfig struct {
 }
 
 type AuthConfig struct {
-        Read            AuthOperationConfig `yaml:"read"`
-        Write           AuthOperationConfig `yaml:"write"`
-        TimestampWindow int64               `yaml:"timestamp_window"`
-        SkipMethods     []string            `yaml:"skip_methods"`
-}
-
-// AuthOperationConfig configures auth for read or write operations.
-// Three states: disabled (allow all), enabled with empty list (require auth),
-// enabled with npubs (whitelist only). Npubs normalized to hex at load time.
-type AuthOperationConfig struct {
-        Enabled      bool     `yaml:"enabled"`
-        AllowedNpubs []string `yaml:"allowed_npubs"`
+        Read            auth.AuthOperationConfig `yaml:"read"`
+        Write           auth.AuthOperationConfig `yaml:"write"`
+        TimestampWindow int64                    `yaml:"timestamp_window"`
+        SkipMethods     []string                 `yaml:"skip_methods"`
 }
 
 type RateLimitConfig struct {
@@ -105,11 +100,11 @@ func Default() *Config {
                         Path: "relay.db",
                 },
                 Auth: AuthConfig{
-                        Read: AuthOperationConfig{
+                        Read: auth.AuthOperationConfig{
                                 Enabled:      false,
                                 AllowedNpubs: nil,
                         },
-                        Write: AuthOperationConfig{
+                        Write: auth.AuthOperationConfig{
                                 Enabled:      false,
                                 AllowedNpubs: nil,
                         },
@@ -349,3 +344,55 @@ func (c *Config) Save(filename string) error {
 
         return nil
 }
+
+func (r *RateLimitConfig) ToRateLimiter() *ratelimit.Config {
+        rlConfig := &ratelimit.Config{
+                RequestsPerSecond:   r.DefaultRPS,
+                BurstSize:           r.DefaultBurst,
+                IPRequestsPerSecond: r.IPRPS,
+                IPBurstSize:         r.IPBurst,
+                SkipMethods:         r.SkipMethods,
+                SkipUsers:           r.SkipUsers,
+                CleanupInterval:     r.CleanupInterval,
+                MaxIdleTime:         r.MaxIdleTime,
+        }
+
+        if r.Methods != nil {
+                rlConfig.MethodLimits = make(map[string]ratelimit.MethodLimit, len(r.Methods))
+                for method, limit := range r.Methods {
+                        rlConfig.MethodLimits[method] = ratelimit.MethodLimit{
+                                RequestsPerSecond: limit.RPS,
+                                BurstSize:         limit.Burst,
+                        }
+                }
+        }
+
+        if r.Users != nil {
+                rlConfig.UserLimits = make(map[string]ratelimit.UserLimit, len(r.Users))
+                for user, limit := range r.Users {
+                        userLimit := ratelimit.UserLimit{
+                                RequestsPerSecond: limit.RPS,
+                                BurstSize:         limit.Burst,
+                        }
+                        if limit.Methods != nil {
+                                userLimit.MethodLimits = make(map[string]ratelimit.MethodLimit, len(limit.Methods))
+                                for method, methodLimit := range limit.Methods {
+                                        userLimit.MethodLimits[method] = ratelimit.MethodLimit{
+                                                RequestsPerSecond: methodLimit.RPS,
+                                                BurstSize:         methodLimit.Burst,
+                                        }
+                                }
+                        }
+                        rlConfig.UserLimits[user] = userLimit
+                }
+        }
+
+        return rlConfig
+}
+
+func (m *MetricsConfig) ToMetrics() *metrics.Config {
+        return &metrics.Config{
+                Namespace: m.Namespace,
+                Subsystem: m.Subsystem,
+        }
+}