// Package config loads the Game Lobby Service process configuration from
// environment variables.
package config

import (
	"crypto/tls"
	"fmt"
	"strings"
	"time"

	"galaxy/lobby/internal/telemetry"
)

const (
	shutdownTimeoutEnvVar = "LOBBY_SHUTDOWN_TIMEOUT"
	logLevelEnvVar        = "LOBBY_LOG_LEVEL"

	publicHTTPAddrEnvVar              = "LOBBY_PUBLIC_HTTP_ADDR"
	publicHTTPReadHeaderTimeoutEnvVar = "LOBBY_PUBLIC_HTTP_READ_HEADER_TIMEOUT"
	publicHTTPReadTimeoutEnvVar       = "LOBBY_PUBLIC_HTTP_READ_TIMEOUT"
	publicHTTPIdleTimeoutEnvVar       = "LOBBY_PUBLIC_HTTP_IDLE_TIMEOUT"

	internalHTTPAddrEnvVar              = "LOBBY_INTERNAL_HTTP_ADDR"
	internalHTTPReadHeaderTimeoutEnvVar = "LOBBY_INTERNAL_HTTP_READ_HEADER_TIMEOUT"
	internalHTTPReadTimeoutEnvVar       = "LOBBY_INTERNAL_HTTP_READ_TIMEOUT"
	internalHTTPIdleTimeoutEnvVar       = "LOBBY_INTERNAL_HTTP_IDLE_TIMEOUT"

	redisAddrEnvVar             = "LOBBY_REDIS_ADDR"
	redisUsernameEnvVar         = "LOBBY_REDIS_USERNAME"
	redisPasswordEnvVar         = "LOBBY_REDIS_PASSWORD"
	redisDBEnvVar               = "LOBBY_REDIS_DB"
	redisTLSEnabledEnvVar       = "LOBBY_REDIS_TLS_ENABLED"
	redisOperationTimeoutEnvVar = "LOBBY_REDIS_OPERATION_TIMEOUT"

	gmEventsStreamEnvVar                 = "LOBBY_GM_EVENTS_STREAM"
	gmEventsReadBlockTimeoutEnvVar       = "LOBBY_GM_EVENTS_READ_BLOCK_TIMEOUT"
	userLifecycleStreamEnvVar            = "LOBBY_USER_LIFECYCLE_STREAM"
	userLifecycleReadBlockTimeoutEnvVar  = "LOBBY_USER_LIFECYCLE_READ_BLOCK_TIMEOUT"
	runtimeStartJobsStreamEnvVar         = "LOBBY_RUNTIME_START_JOBS_STREAM"
	runtimeStopJobsStreamEnvVar          = "LOBBY_RUNTIME_STOP_JOBS_STREAM"
	runtimeJobResultsStreamEnvVar        = "LOBBY_RUNTIME_JOB_RESULTS_STREAM"
	runtimeJobResultsReadBlockTimeoutEnv = "LOBBY_RUNTIME_JOB_RESULTS_READ_BLOCK_TIMEOUT"
	notificationIntentsStreamEnvVar      = "LOBBY_NOTIFICATION_INTENTS_STREAM"

	userServiceBaseURLEnvVar = "LOBBY_USER_SERVICE_BASE_URL"
	userServiceTimeoutEnvVar = "LOBBY_USER_SERVICE_TIMEOUT"

	gmBaseURLEnvVar = "LOBBY_GM_BASE_URL"
	gmTimeoutEnvVar = "LOBBY_GM_TIMEOUT"

	enrollmentAutomationIntervalEnvVar = "LOBBY_ENROLLMENT_AUTOMATION_INTERVAL"

	raceNameDirectoryBackendEnvVar  = "LOBBY_RACE_NAME_DIRECTORY_BACKEND"
	raceNameExpirationIntervalEnvVar = "LOBBY_RACE_NAME_EXPIRATION_INTERVAL"

	otelServiceNameEnvVar                 = "OTEL_SERVICE_NAME"
	otelTracesExporterEnvVar              = "OTEL_TRACES_EXPORTER"
	otelMetricsExporterEnvVar             = "OTEL_METRICS_EXPORTER"
	otelExporterOTLPProtocolEnvVar        = "OTEL_EXPORTER_OTLP_PROTOCOL"
	otelExporterOTLPTracesProtocolEnvVar  = "OTEL_EXPORTER_OTLP_TRACES_PROTOCOL"
	otelExporterOTLPMetricsProtocolEnvVar = "OTEL_EXPORTER_OTLP_METRICS_PROTOCOL"
	otelStdoutTracesEnabledEnvVar         = "LOBBY_OTEL_STDOUT_TRACES_ENABLED"
	otelStdoutMetricsEnabledEnvVar        = "LOBBY_OTEL_STDOUT_METRICS_ENABLED"

	defaultShutdownTimeout                   = 30 * time.Second
	defaultLogLevel                          = "info"
	defaultPublicHTTPAddr                    = ":8094"
	defaultInternalHTTPAddr                  = ":8095"
	defaultReadHeaderTimeout                 = 2 * time.Second
	defaultReadTimeout                       = 10 * time.Second
	defaultIdleTimeout                       = time.Minute
	defaultRedisDB                           = 0
	defaultRedisOperationTimeout             = 2 * time.Second
	defaultGMEventsStream                    = "gm:lobby_events"
	defaultGMEventsReadBlockTimeout          = 2 * time.Second
	defaultUserLifecycleStream               = "user:lifecycle_events"
	defaultUserLifecycleReadBlockTimeout     = 2 * time.Second
	defaultRuntimeStartJobsStream            = "runtime:start_jobs"
	defaultRuntimeStopJobsStream             = "runtime:stop_jobs"
	defaultRuntimeJobResultsStream           = "runtime:job_results"
	defaultRuntimeJobResultsReadBlockTimeout = 2 * time.Second
	defaultNotificationIntentsStream         = "notification:intents"
	defaultUserServiceTimeout                = time.Second
	defaultGMTimeout                         = 5 * time.Second
	defaultEnrollmentAutomationInterval      = 30 * time.Second
	defaultRaceNameExpirationInterval        = time.Hour
	defaultOTelServiceName                   = "galaxy-lobby"

	// RaceNameDirectoryBackendRedis selects the Redis-backed Race Name
	// Directory adapter. It is the default production backend.
	RaceNameDirectoryBackendRedis = "redis"

	// RaceNameDirectoryBackendStub selects the in-process Race Name
	// Directory stub used by unit tests that do not need Redis.
	RaceNameDirectoryBackendStub = "stub"
)

// Config stores the full Game Lobby Service process configuration.
type Config struct {
	// ShutdownTimeout bounds graceful shutdown of every long-lived component.
	ShutdownTimeout time.Duration

	// Logging configures the process-wide structured logger.
	Logging LoggingConfig

	// PublicHTTP configures the public authenticated HTTP listener that serves
	// gateway-forwarded player commands.
	PublicHTTP PublicHTTPConfig

	// InternalHTTP configures the trusted internal HTTP listener that serves
	// Game Master registration and admin operations.
	InternalHTTP InternalHTTPConfig

	// Redis configures the shared Redis client and the Redis Streams keys
	// consumed by the runnable service skeleton and its future workers.
	Redis RedisConfig

	// UserService configures the synchronous User Service eligibility client.
	UserService UserServiceConfig

	// GM configures the synchronous Game Master registration client.
	GM GMConfig

	// EnrollmentAutomation configures the periodic enrollment automation
	// worker that will be added in the
	EnrollmentAutomation EnrollmentAutomationConfig

	// RaceNameDirectory configures the Race Name Directory backend
	// selector. It governs which adapter is wired by the runtime:
	// Redis-backed persistence in production, an in-process stub for
	// tests that do not need Redis.
	RaceNameDirectory RaceNameDirectoryConfig

	// PendingRegistration configures the periodic worker that releases
	// every pending_registration whose eligible_until has passed.
	PendingRegistration PendingRegistrationConfig

	// Telemetry configures the process-wide OpenTelemetry runtime.
	Telemetry TelemetryConfig
}

// RaceNameDirectoryConfig configures which Race Name Directory adapter
// is wired into the runtime.
type RaceNameDirectoryConfig struct {
	// Backend selects the Race Name Directory adapter. Accepted values
	// are RaceNameDirectoryBackendRedis and RaceNameDirectoryBackendStub.
	Backend string
}

// Validate reports whether cfg stores a supported Race Name Directory
// backend selector.
func (cfg RaceNameDirectoryConfig) Validate() error {
	switch cfg.Backend {
	case RaceNameDirectoryBackendRedis, RaceNameDirectoryBackendStub:
		return nil
	case "":
		return fmt.Errorf("race name directory backend must not be empty")
	default:
		return fmt.Errorf("race name directory backend %q must be one of %q or %q",
			cfg.Backend,
			RaceNameDirectoryBackendRedis,
			RaceNameDirectoryBackendStub)
	}
}

// LoggingConfig configures the process-wide structured logger.
type LoggingConfig struct {
	// Level stores the process log level accepted by log/slog.
	Level string
}

// PublicHTTPConfig configures the public authenticated HTTP listener.
type PublicHTTPConfig struct {
	// Addr stores the TCP listen address.
	Addr string

	// ReadHeaderTimeout bounds request-header reading.
	ReadHeaderTimeout time.Duration

	// ReadTimeout bounds reading one request.
	ReadTimeout time.Duration

	// IdleTimeout bounds how long keep-alive connections stay open.
	IdleTimeout time.Duration
}

// Validate reports whether cfg stores a usable public HTTP listener
// configuration.
func (cfg PublicHTTPConfig) Validate() error {
	switch {
	case strings.TrimSpace(cfg.Addr) == "":
		return fmt.Errorf("public HTTP addr must not be empty")
	case !isTCPAddr(cfg.Addr):
		return fmt.Errorf("public HTTP addr %q must use host:port form", cfg.Addr)
	case cfg.ReadHeaderTimeout <= 0:
		return fmt.Errorf("public HTTP read header timeout must be positive")
	case cfg.ReadTimeout <= 0:
		return fmt.Errorf("public HTTP read timeout must be positive")
	case cfg.IdleTimeout <= 0:
		return fmt.Errorf("public HTTP idle timeout must be positive")
	default:
		return nil
	}
}

// InternalHTTPConfig configures the trusted internal HTTP listener.
type InternalHTTPConfig struct {
	// Addr stores the TCP listen address.
	Addr string

	// ReadHeaderTimeout bounds request-header reading.
	ReadHeaderTimeout time.Duration

	// ReadTimeout bounds reading one request.
	ReadTimeout time.Duration

	// IdleTimeout bounds how long keep-alive connections stay open.
	IdleTimeout time.Duration
}

// Validate reports whether cfg stores a usable internal HTTP listener
// configuration.
func (cfg InternalHTTPConfig) Validate() error {
	switch {
	case strings.TrimSpace(cfg.Addr) == "":
		return fmt.Errorf("internal HTTP addr must not be empty")
	case !isTCPAddr(cfg.Addr):
		return fmt.Errorf("internal HTTP addr %q must use host:port form", cfg.Addr)
	case cfg.ReadHeaderTimeout <= 0:
		return fmt.Errorf("internal HTTP read header timeout must be positive")
	case cfg.ReadTimeout <= 0:
		return fmt.Errorf("internal HTTP read timeout must be positive")
	case cfg.IdleTimeout <= 0:
		return fmt.Errorf("internal HTTP idle timeout must be positive")
	default:
		return nil
	}
}

// RedisConfig configures the shared Redis client and the Redis-owned
// Streams keys consumed by the runnable service skeleton.
type RedisConfig struct {
	// Addr stores the Redis network address.
	Addr string

	// Username stores the optional Redis ACL username.
	Username string

	// Password stores the optional Redis ACL password.
	Password string

	// DB stores the Redis logical database index.
	DB int

	// TLSEnabled reports whether TLS must be used for Redis connections.
	TLSEnabled bool

	// OperationTimeout bounds one Redis round trip including the startup PING.
	OperationTimeout time.Duration

	// GMEventsStream stores the Redis Streams key for Game Master runtime
	// events consumed by Lobby.
	GMEventsStream string

	// GMEventsReadBlockTimeout bounds the maximum blocking read window on
	// GMEventsStream.
	GMEventsReadBlockTimeout time.Duration

	// RuntimeStartJobsStream stores the Redis Streams key Lobby writes start
	// jobs to.
	RuntimeStartJobsStream string

	// RuntimeStopJobsStream stores the Redis Streams key Lobby writes stop
	// jobs to. publishes stop jobs only from the orphan-container
	// path inside the runtime job result worker.
	RuntimeStopJobsStream string

	// RuntimeJobResultsStream stores the Redis Streams key Lobby reads
	// runtime job results from.
	RuntimeJobResultsStream string

	// RuntimeJobResultsReadBlockTimeout bounds the maximum blocking read window
	// on RuntimeJobResultsStream.
	RuntimeJobResultsReadBlockTimeout time.Duration

	// NotificationIntentsStream stores the Redis Streams key Lobby writes
	// notification intents to.
	NotificationIntentsStream string

	// UserLifecycleStream stores the Redis Streams key Lobby reads
	// User Service lifecycle events from. The stream is consumed by the
	// cascade worker.
	UserLifecycleStream string

	// UserLifecycleReadBlockTimeout bounds the maximum blocking read
	// window on UserLifecycleStream.
	UserLifecycleReadBlockTimeout time.Duration
}

// TLSConfig returns the conservative TLS configuration used by the Redis
// client when TLSEnabled is true.
func (cfg RedisConfig) TLSConfig() *tls.Config {
	if !cfg.TLSEnabled {
		return nil
	}

	return &tls.Config{MinVersion: tls.VersionTLS12}
}

// Validate reports whether cfg stores a usable Redis configuration.
func (cfg RedisConfig) Validate() error {
	switch {
	case strings.TrimSpace(cfg.Addr) == "":
		return fmt.Errorf("redis addr must not be empty")
	case !isTCPAddr(cfg.Addr):
		return fmt.Errorf("redis addr %q must use host:port form", cfg.Addr)
	case cfg.DB < 0:
		return fmt.Errorf("redis db must not be negative")
	case cfg.OperationTimeout <= 0:
		return fmt.Errorf("redis operation timeout must be positive")
	case strings.TrimSpace(cfg.GMEventsStream) == "":
		return fmt.Errorf("redis gm events stream must not be empty")
	case cfg.GMEventsReadBlockTimeout <= 0:
		return fmt.Errorf("redis gm events read block timeout must be positive")
	case strings.TrimSpace(cfg.RuntimeStartJobsStream) == "":
		return fmt.Errorf("redis runtime start jobs stream must not be empty")
	case strings.TrimSpace(cfg.RuntimeStopJobsStream) == "":
		return fmt.Errorf("redis runtime stop jobs stream must not be empty")
	case strings.TrimSpace(cfg.RuntimeJobResultsStream) == "":
		return fmt.Errorf("redis runtime job results stream must not be empty")
	case cfg.RuntimeJobResultsReadBlockTimeout <= 0:
		return fmt.Errorf("redis runtime job results read block timeout must be positive")
	case strings.TrimSpace(cfg.NotificationIntentsStream) == "":
		return fmt.Errorf("redis notification intents stream must not be empty")
	case strings.TrimSpace(cfg.UserLifecycleStream) == "":
		return fmt.Errorf("redis user lifecycle stream must not be empty")
	case cfg.UserLifecycleReadBlockTimeout <= 0:
		return fmt.Errorf("redis user lifecycle read block timeout must be positive")
	default:
		return nil
	}
}

// UserServiceConfig configures the synchronous User Service eligibility
// client used by the application flow.
type UserServiceConfig struct {
	// BaseURL stores the User Service root URL.
	BaseURL string

	// Timeout bounds one User Service request.
	Timeout time.Duration
}

// Validate reports whether cfg stores a usable User Service client
// configuration.
func (cfg UserServiceConfig) Validate() error {
	switch {
	case strings.TrimSpace(cfg.BaseURL) == "":
		return fmt.Errorf("user service base url must not be empty")
	case !isHTTPURL(cfg.BaseURL):
		return fmt.Errorf("user service base url %q must be an absolute http(s) URL", cfg.BaseURL)
	case cfg.Timeout <= 0:
		return fmt.Errorf("user service timeout must be positive")
	default:
		return nil
	}
}

// GMConfig configures the synchronous Game Master registration client.
type GMConfig struct {
	// BaseURL stores the Game Master root URL.
	BaseURL string

	// Timeout bounds one Game Master request.
	Timeout time.Duration
}

// Validate reports whether cfg stores a usable Game Master client
// configuration.
func (cfg GMConfig) Validate() error {
	switch {
	case strings.TrimSpace(cfg.BaseURL) == "":
		return fmt.Errorf("gm base url must not be empty")
	case !isHTTPURL(cfg.BaseURL):
		return fmt.Errorf("gm base url %q must be an absolute http(s) URL", cfg.BaseURL)
	case cfg.Timeout <= 0:
		return fmt.Errorf("gm timeout must be positive")
	default:
		return nil
	}
}

// EnrollmentAutomationConfig configures the periodic enrollment automation
// worker.
type EnrollmentAutomationConfig struct {
	// Interval stores the enrollment automation tick interval.
	Interval time.Duration
}

// Validate reports whether cfg stores a usable enrollment automation
// configuration.
func (cfg EnrollmentAutomationConfig) Validate() error {
	if cfg.Interval <= 0 {
		return fmt.Errorf("enrollment automation interval must be positive")
	}

	return nil
}

// PendingRegistrationConfig configures the periodic worker that
// releases expired Race Name Directory pending_registration entries.
type PendingRegistrationConfig struct {
	// Interval stores the pending-registration expiration tick interval.
	Interval time.Duration
}

// Validate reports whether cfg stores a usable pending-registration
// expiration worker configuration.
func (cfg PendingRegistrationConfig) Validate() error {
	if cfg.Interval <= 0 {
		return fmt.Errorf("race name expiration interval must be positive")
	}

	return nil
}

// TelemetryConfig configures the Game Lobby Service OpenTelemetry runtime.
type TelemetryConfig struct {
	// ServiceName overrides the default OpenTelemetry service name.
	ServiceName string

	// TracesExporter selects the external traces exporter. Supported values are
	// `none` and `otlp`.
	TracesExporter string

	// MetricsExporter selects the external metrics exporter. Supported values
	// are `none` and `otlp`.
	MetricsExporter string

	// TracesProtocol selects the OTLP traces protocol when TracesExporter is
	// `otlp`.
	TracesProtocol string

	// MetricsProtocol selects the OTLP metrics protocol when MetricsExporter is
	// `otlp`.
	MetricsProtocol string

	// StdoutTracesEnabled enables the additional stdout trace exporter used
	// for local development and debugging.
	StdoutTracesEnabled bool

	// StdoutMetricsEnabled enables the additional stdout metric exporter used
	// for local development and debugging.
	StdoutMetricsEnabled bool
}

// Validate reports whether cfg contains a supported OpenTelemetry
// configuration.
func (cfg TelemetryConfig) Validate() error {
	return telemetry.ProcessConfig{
		ServiceName:          cfg.ServiceName,
		TracesExporter:       cfg.TracesExporter,
		MetricsExporter:      cfg.MetricsExporter,
		TracesProtocol:       cfg.TracesProtocol,
		MetricsProtocol:      cfg.MetricsProtocol,
		StdoutTracesEnabled:  cfg.StdoutTracesEnabled,
		StdoutMetricsEnabled: cfg.StdoutMetricsEnabled,
	}.Validate()
}

// DefaultConfig returns the default Game Lobby Service process
// configuration.
func DefaultConfig() Config {
	return Config{
		ShutdownTimeout: defaultShutdownTimeout,
		Logging: LoggingConfig{
			Level: defaultLogLevel,
		},
		PublicHTTP: PublicHTTPConfig{
			Addr:              defaultPublicHTTPAddr,
			ReadHeaderTimeout: defaultReadHeaderTimeout,
			ReadTimeout:       defaultReadTimeout,
			IdleTimeout:       defaultIdleTimeout,
		},
		InternalHTTP: InternalHTTPConfig{
			Addr:              defaultInternalHTTPAddr,
			ReadHeaderTimeout: defaultReadHeaderTimeout,
			ReadTimeout:       defaultReadTimeout,
			IdleTimeout:       defaultIdleTimeout,
		},
		Redis: RedisConfig{
			DB:                                defaultRedisDB,
			OperationTimeout:                  defaultRedisOperationTimeout,
			GMEventsStream:                    defaultGMEventsStream,
			GMEventsReadBlockTimeout:          defaultGMEventsReadBlockTimeout,
			RuntimeStartJobsStream:            defaultRuntimeStartJobsStream,
			RuntimeStopJobsStream:             defaultRuntimeStopJobsStream,
			RuntimeJobResultsStream:           defaultRuntimeJobResultsStream,
			RuntimeJobResultsReadBlockTimeout: defaultRuntimeJobResultsReadBlockTimeout,
			NotificationIntentsStream:         defaultNotificationIntentsStream,
			UserLifecycleStream:               defaultUserLifecycleStream,
			UserLifecycleReadBlockTimeout:     defaultUserLifecycleReadBlockTimeout,
		},
		UserService: UserServiceConfig{
			Timeout: defaultUserServiceTimeout,
		},
		GM: GMConfig{
			Timeout: defaultGMTimeout,
		},
		EnrollmentAutomation: EnrollmentAutomationConfig{
			Interval: defaultEnrollmentAutomationInterval,
		},
		RaceNameDirectory: RaceNameDirectoryConfig{
			Backend: RaceNameDirectoryBackendRedis,
		},
		PendingRegistration: PendingRegistrationConfig{
			Interval: defaultRaceNameExpirationInterval,
		},
		Telemetry: TelemetryConfig{
			ServiceName:     defaultOTelServiceName,
			TracesExporter:  "none",
			MetricsExporter: "none",
		},
	}
}