// Package centrifugo is the Centrifugo driver of lighthouse: an HTTP API
// client, a connection and subscription token issuer, and the subscribe
// proxy handler. Import it for its side effect to register the
// "centrifugo" realtime.driver.
package centrifugo

import (
	"net/netip"
	"strings"
	"time"

	"git.golem15.com/golem15/summercms/modules/compass"
	"git.golem15.com/golem15/summercms/modules/lighthouse"
	"git.golem15.com/golem15/summercms/modules/surf"
)

// Default values of the realtime.centrifugo.* keys.
const (
	DefaultAPIURL        = "http://127.0.0.1:8001/api"
	DefaultTokenTTL      = 3600 * time.Second
	DefaultWSURL         = "/ws"
	DefaultTokenPath     = "/api/realtime/token"
	DefaultSubscribePath = "/api/realtime/subscribe"
)

// Config is the realtime.centrifugo.* configuration.
type Config struct {
	// APIURL is the Centrifugo HTTP API base, without a trailing method.
	APIURL string
	// APIKey authenticates publishes; empty disables them.
	APIKey string
	// TokenSecret signs connection and subscription tokens (HS256); empty
	// makes the token route answer 503.
	TokenSecret string
	// TokenTTL is the lifetime of issued tokens.
	TokenTTL time.Duration
	// WSURL is the WebSocket URL the client connects to.
	WSURL string
	// ProxySecret is the X-Centrifugo-Secret header value the subscribe
	// proxy expects; empty denies every subscribe.
	ProxySecret string
	// TokenPath and SubscribePath are the mounted route paths.
	TokenPath     string
	SubscribePath string
	// TrustedProxies are the http.trusted_proxies used to log the client IP
	// of a denied subscribe.
	TrustedProxies []netip.Prefix
}

// LoadConfig reads realtime.centrifugo.* from c, filling the defaults.
// token_ttl is an integer number of seconds or a duration string.
func LoadConfig(c *compass.Config) Config {
	cfg := Config{
		APIURL:        DefaultAPIURL,
		TokenTTL:      DefaultTokenTTL,
		WSURL:         DefaultWSURL,
		TokenPath:     DefaultTokenPath,
		SubscribePath: DefaultSubscribePath,
	}
	if c == nil {
		return cfg
	}
	str := func(key string) string { return strings.TrimSpace(c.String("realtime.centrifugo." + key)) }
	if v := str("api_url"); v != "" {
		cfg.APIURL = strings.TrimSuffix(v, "/")
	}
	cfg.APIKey = str("api_key")
	cfg.TokenSecret = str("token_secret")
	cfg.ProxySecret = str("proxy_secret")
	if d := lighthouse.DurationSetting(c, "realtime.centrifugo.token_ttl"); d > 0 {
		cfg.TokenTTL = d
	}
	if v := str("ws_url"); v != "" {
		cfg.WSURL = v
	}
	if v := str("token_path"); v != "" {
		cfg.TokenPath = v
	}
	if v := str("subscribe_path"); v != "" {
		cfg.SubscribePath = v
	}
	cfg.TrustedProxies = surf.TrustedProxies(c)
	return cfg
}