# Configuration

This package provides configuration management for the relay with support for YAML files and environment variable overrides.

## Overview

Configuration can be loaded from:
1. **YAML file** - Primary configuration source
2. **Environment variables** - Override file values
3. **Defaults** - Sensible defaults if not specified

## Usage

### Load from File

```go
import "northwest.io/muxstr/internal/config"

// Load configuration
cfg, err := config.Load("config.yaml")
if err != nil {
    log.Fatal(err)
}

// Use configuration
fmt.Printf("gRPC listening on %s\n", cfg.Server.GrpcAddr)
```

### Load with Environment Overrides

```bash
# Set environment variables
export MUXSTR_SERVER_GRPC_ADDR=":50051"
export MUXSTR_AUTH_REQUIRED=true
export MUXSTR_RATE_LIMIT_DEFAULT_RPS=100

# Run relay
./relay -config config.yaml
```

Environment variables use the format: `MUXSTR_<SECTION>_<KEY>`

### Use Defaults

```go
// Get default configuration
cfg := config.Default()
```

## Configuration File Format

### Complete Example

```yaml
# Server configuration
server:
  # gRPC server address
  grpc_addr: ":50051"

  # HTTP server address (for Connect and WebSocket)
  http_addr: ":8080"

  # Public URL for reverse proxy deployments (optional)
  # Example: "relay.example.com"
  public_url: ""

  # Read timeout for requests (optional)
  read_timeout: "30s"

  # Write timeout for responses (optional)
  write_timeout: "30s"

# Database configuration
database:
  # Path to SQLite database file
  path: "relay.db"

  # Maximum number of open connections
  max_connections: 10

  # Connection max lifetime
  max_lifetime: "1h"

# Authentication configuration
auth:
  # Enable authentication
  enabled: false

  # Require authentication for all requests
  # If false, authentication is optional (pubkey available if provided)
  required: false

  # Timestamp window in seconds for replay protection
  timestamp_window: 60

  # Allowed pubkeys (optional, whitelist)
  # If empty, all valid signatures are accepted
  allowed_pubkeys: []

  # Skip authentication for these methods
  skip_methods:
    - "/grpc.health.v1.Health/Check"

# Rate limiting configuration
rate_limit:
  # Enable rate limiting
  enabled: false

  # Default rate limit (requests per second)
  default_rps: 10

  # Default burst size (token bucket capacity)
  default_burst: 20

  # Rate limit for unauthenticated users (per IP)
  ip_rps: 5
  ip_burst: 10

  # Method-specific limits
  methods:
    "/nostr.v1.NostrRelay/PublishEvent":
      rps: 2
      burst: 5
    "/nostr.v1.NostrRelay/Subscribe":
      rps: 1
      burst: 3

  # User-specific limits (VIP/premium users)
  users:
    "vip-pubkey-here":
      rps: 100
      burst: 200

  # Skip rate limiting for these methods
  skip_methods:
    - "/grpc.health.v1.Health/Check"

  # Skip rate limiting for these pubkeys (admins)
  skip_users: []

  # Cleanup interval for idle limiters
  cleanup_interval: "5m"

  # Max idle time before limiter is removed
  max_idle_time: "10m"

# Metrics configuration
metrics:
  # Enable Prometheus metrics
  enabled: true

  # Metrics HTTP server address
  addr: ":9090"

  # Metrics path
  path: "/metrics"

  # Namespace for metrics
  namespace: "muxstr"

  # Subsystem for metrics
  subsystem: "relay"

# Logging configuration
logging:
  # Log level: debug, info, warn, error
  level: "info"

  # Log format: json, text
  format: "json"

  # Output: stdout, stderr, or file path
  output: "stdout"

# Storage configuration
storage:
  # Enable automatic compaction
  auto_compact: true

  # Compact interval
  compact_interval: "24h"

  # Maximum event age (0 = unlimited)
  max_event_age: "0"
```

### Minimal Example

```yaml
server:
  grpc_addr: ":50051"
  http_addr: ":8080"

database:
  path: "relay.db"

metrics:
  enabled: true
  addr: ":9090"
```

## Environment Variables

All configuration values can be overridden with environment variables using the pattern:

```
MUXSTR_<SECTION>_<SUBSECTION>_<KEY>=value
```

Examples:

| Config Path | Environment Variable |
|-------------|---------------------|
| `server.grpc_addr` | `MUXSTR_SERVER_GRPC_ADDR` |
| `database.path` | `MUXSTR_DATABASE_PATH` |
| `auth.required` | `MUXSTR_AUTH_REQUIRED` |
| `rate_limit.default_rps` | `MUXSTR_RATE_LIMIT_DEFAULT_RPS` |
| `metrics.enabled` | `MUXSTR_METRICS_ENABLED` |

Complex types:

```bash
# Lists (comma-separated)
export MUXSTR_AUTH_ALLOWED_PUBKEYS="pubkey1,pubkey2,pubkey3"

# Durations
export MUXSTR_SERVER_READ_TIMEOUT="30s"
export MUXSTR_DATABASE_MAX_LIFETIME="1h"

# Booleans
export MUXSTR_AUTH_ENABLED=true
export MUXSTR_METRICS_ENABLED=false
```

## Validation

Configuration is validated on load:

```go
cfg, err := config.Load("config.yaml")
if err != nil {
    // Validation errors include detailed messages
    log.Fatalf("Invalid configuration: %v", err)
}
```

Validation checks:
- Required fields are present
- Addresses are valid (host:port format)
- File paths are accessible
- Numeric values are in valid ranges
- Durations are parseable

## Default Values

If not specified, the following defaults are used:

```go
Server:
  GrpcAddr: ":50051"
  HttpAddr: ":8080"
  ReadTimeout: 30s
  WriteTimeout: 30s

Database:
  Path: "relay.db"
  MaxConnections: 10
  MaxLifetime: 1h

Auth:
  Enabled: false
  Required: false
  TimestampWindow: 60

RateLimit:
  Enabled: false
  DefaultRPS: 10
  DefaultBurst: 20
  IPRPS: 5
  IPBurst: 10
  CleanupInterval: 5m
  MaxIdleTime: 10m

Metrics:
  Enabled: true
  Addr: ":9090"
  Path: "/metrics"
  Namespace: "muxstr"
  Subsystem: "relay"

Logging:
  Level: "info"
  Format: "json"
  Output: "stdout"
```

## Configuration Precedence

Values are loaded in this order (later overrides earlier):

1. **Defaults** - Built-in default values
2. **Config file** - Values from YAML file
3. **Environment variables** - OS environment overrides

Example:
```yaml
# config.yaml
server:
  grpc_addr: ":50051"
```

```bash
# Environment override
export MUXSTR_SERVER_GRPC_ADDR=":9000"

# Result: gRPC listens on :9000 (env var wins)
```

## Reloading Configuration

Configuration can be reloaded without restart (future feature):

```go
// Watch for changes
watcher, err := config.Watch("config.yaml")
if err != nil {
    log.Fatal(err)
}

for cfg := range watcher.Updates {
    // Apply new configuration
    updateServer(cfg)
}
```

## Best Practices

1. **Use config files for static settings**: Server addresses, paths, etc.
2. **Use env vars for deployment-specific settings**: Secrets, environment-specific URLs
3. **Keep secrets out of config files**: Use env vars or secret management
4. **Version control your config**: Check in config.yaml (without secrets)
5. **Document custom settings**: Add comments to config.yaml
6. **Validate in CI**: Run `relay -config config.yaml -validate` in CI pipeline
7. **Use different configs per environment**: `config.dev.yaml`, `config.prod.yaml`

## Example Configurations

### Development

```yaml
server:
  grpc_addr: ":50051"
  http_addr: ":8080"

database:
  path: "relay-dev.db"

auth:
  enabled: false

rate_limit:
  enabled: false

metrics:
  enabled: true
  addr: ":9090"

logging:
  level: "debug"
  format: "text"
```

### Production

```yaml
server:
  grpc_addr: ":50051"
  http_addr: ":8080"
  public_url: "relay.example.com"
  read_timeout: "30s"
  write_timeout: "30s"

database:
  path: "/var/lib/muxstr/relay.db"
  max_connections: 50

auth:
  enabled: true
  required: false
  timestamp_window: 60

rate_limit:
  enabled: true
  default_rps: 10
  default_burst: 20
  methods:
    "/nostr.v1.NostrRelay/PublishEvent":
      rps: 2
      burst: 5

metrics:
  enabled: true
  addr: ":9090"

logging:
  level: "info"
  format: "json"
  output: "/var/log/muxstr/relay.log"
```

### High-Performance

```yaml
server:
  grpc_addr: ":50051"
  http_addr: ":8080"

database:
  path: "/mnt/fast-ssd/relay.db"
  max_connections: 100
  max_lifetime: "30m"

auth:
  enabled: true
  required: true
  timestamp_window: 30

rate_limit:
  enabled: true
  default_rps: 100
  default_burst: 200

metrics:
  enabled: true
  addr: ":9090"

logging:
  level: "warn"
  format: "json"
```