// Package lighthouse is the transport-neutral realtime layer: a publisher
// interface with pluggable drivers, subscribe-time channel authorization,
// and model broadcasts enqueued in the write transaction.
//
// Models, authorizers and application code talk only to this package. A
// driver package (for example lighthouse/centrifugo) is imported for its
// side effect of registering itself, and is chosen with realtime.driver.
package lighthouse

import (
	"fmt"
	"log/slog"
	"strings"
	"sync"
	"time"

	"git.golem15.com/golem15/summercms/modules/backpack"
	"git.golem15.com/golem15/summercms/modules/compass"
)

const (
	// DefaultDriver is the driver used when realtime.driver is empty.
	DefaultDriver = "null"
	// DefaultQueue is the River queue of broadcast jobs when
	// realtime.broadcast_queue is empty.
	DefaultQueue = "broadcasts"
	// DefaultTimeout is the broadcast job timeout when
	// realtime.broadcast_timeout is empty.
	DefaultTimeout = 5 * time.Second
)

// Service is the app-scoped realtime service. Get it with From.
type Service struct {
	app       *backpack.App
	driver    Driver
	log       *slog.Logger
	namespace string
	queue     string
	timeout   time.Duration

	mu     sync.RWMutex
	lookup UserLookup
}

// From returns the app's Service, building and publishing it on first use.
// The first call reads realtime.driver (default "null"),
// realtime.broadcast_namespace (default ""), realtime.broadcast_queue
// (default "broadcasts") and realtime.broadcast_timeout (default 5s; an
// integer number of seconds or a duration string) and builds the driver
// through its registered factory. An unknown driver name is an error.
func From(app *backpack.App) (*Service, error) {
	if app == nil {
		return nil, fmt.Errorf("lighthouse: app is nil")
	}
	if s, ok := app.Lookup[*Service](); ok && s != nil {
		return s, nil
	}
	svc := newService(app)
	name := DefaultDriver
	if app.Config != nil {
		if v := strings.TrimSpace(app.Config.String("realtime.driver")); v != "" {
			name = strings.ToLower(v)
		}
	}
	factory, ok := driverFactory(name)
	if !ok {
		return nil, fmt.Errorf("lighthouse: unknown realtime.driver %q (registered: %s; a driver package must be imported to register itself)", name, strings.Join(driverNames(), ", "))
	}
	d, err := factory(app, svc)
	if err != nil {
		return nil, fmt.Errorf("lighthouse: driver %s: %w", name, err)
	}
	if d == nil {
		return nil, fmt.Errorf("lighthouse: driver %s returned nil", name)
	}
	svc.driver = d
	if err := app.Publish(svc); err != nil {
		if existing, ok := app.Lookup[*Service](); ok && existing != nil {
			return existing, nil
		}
		return nil, fmt.Errorf("lighthouse: %w", err)
	}
	return svc, nil
}

func newService(app *backpack.App) *Service {
	svc := &Service{
		app:     app,
		log:     loggerFromApp(app),
		queue:   DefaultQueue,
		timeout: DefaultTimeout,
	}
	if app == nil || app.Config == nil {
		return svc
	}
	c := app.Config
	svc.namespace = strings.TrimSpace(c.String("realtime.broadcast_namespace"))
	if v := strings.TrimSpace(c.String("realtime.broadcast_queue")); v != "" {
		svc.queue = v
	}
	if d := DurationSetting(c, "realtime.broadcast_timeout"); d > 0 {
		svc.timeout = d
	}
	return svc
}

// Driver returns the driver selected by realtime.driver.
func (s *Service) Driver() Driver {
	if s == nil {
		return nil
	}
	return s.driver
}

// Logger returns the app logger the service and its driver log through.
func (s *Service) Logger() *slog.Logger {
	if s == nil || s.log == nil {
		return slog.Default()
	}
	return s.log
}

// Namespace returns realtime.broadcast_namespace.
func (s *Service) Namespace() string {
	if s == nil {
		return ""
	}
	return s.namespace
}

// Queue returns the River queue broadcast jobs are enqueued on.
func (s *Service) Queue() string {
	if s == nil {
		return DefaultQueue
	}
	return s.queue
}

// Timeout returns the per-job timeout of a broadcast job.
func (s *Service) Timeout() time.Duration {
	if s == nil {
		return DefaultTimeout
	}
	return s.timeout
}

// DurationSetting reads path as a duration string ("5s") or an integer
// number of seconds. It returns 0 when the key is missing or invalid.
func DurationSetting(c *compass.Config, path string) time.Duration {
	if c == nil {
		return 0
	}
	raw := strings.TrimSpace(c.String(path))
	if raw == "" {
		return 0
	}
	if d, err := time.ParseDuration(raw); err == nil && d > 0 {
		return d
	}
	if n := c.Int(path); n > 0 {
		return time.Duration(n) * time.Second
	}
	return 0
}

func loggerFromApp(app *backpack.App) *slog.Logger {
	if app != nil {
		if log, ok := app.Lookup[*slog.Logger](); ok && log != nil {
			return log
		}
	}
	return slog.Default()
}