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

import (
	"fmt"
	"net"
	netmail "net/mail"
	"net/url"
	"strings"
	"time"

	"galaxy/notification/internal/telemetry"
	"galaxy/postgres"
	"galaxy/redisconn"
)

const (
	envPrefix = "NOTIFICATION"

	shutdownTimeoutEnvVar = "NOTIFICATION_SHUTDOWN_TIMEOUT"
	logLevelEnvVar        = "NOTIFICATION_LOG_LEVEL"

	internalHTTPAddrEnvVar              = "NOTIFICATION_INTERNAL_HTTP_ADDR"
	internalHTTPReadHeaderTimeoutEnvVar = "NOTIFICATION_INTERNAL_HTTP_READ_HEADER_TIMEOUT"
	internalHTTPReadTimeoutEnvVar       = "NOTIFICATION_INTERNAL_HTTP_READ_TIMEOUT"
	internalHTTPIdleTimeoutEnvVar       = "NOTIFICATION_INTERNAL_HTTP_IDLE_TIMEOUT"

	intentsStreamEnvVar                = "NOTIFICATION_INTENTS_STREAM"
	intentsReadBlockTimeoutEnvVar      = "NOTIFICATION_INTENTS_READ_BLOCK_TIMEOUT"
	gatewayClientEventsStreamEnvVar    = "NOTIFICATION_GATEWAY_CLIENT_EVENTS_STREAM"
	gatewayClientEventsStreamMaxEnvVar = "NOTIFICATION_GATEWAY_CLIENT_EVENTS_STREAM_MAX_LEN"
	mailDeliveryCommandsStreamEnvVar   = "NOTIFICATION_MAIL_DELIVERY_COMMANDS_STREAM"

	pushRetryMaxAttemptsEnvVar  = "NOTIFICATION_PUSH_RETRY_MAX_ATTEMPTS"
	emailRetryMaxAttemptsEnvVar = "NOTIFICATION_EMAIL_RETRY_MAX_ATTEMPTS"
	routeLeaseTTLEnvVar         = "NOTIFICATION_ROUTE_LEASE_TTL"
	routeBackoffMinEnvVar       = "NOTIFICATION_ROUTE_BACKOFF_MIN"
	routeBackoffMaxEnvVar       = "NOTIFICATION_ROUTE_BACKOFF_MAX"
	idempotencyTTLEnvVar        = "NOTIFICATION_IDEMPOTENCY_TTL"

	recordRetentionEnvVar          = "NOTIFICATION_RECORD_RETENTION"
	malformedIntentRetentionEnvVar = "NOTIFICATION_MALFORMED_INTENT_RETENTION"
	cleanupIntervalEnvVar          = "NOTIFICATION_CLEANUP_INTERVAL"

	userServiceBaseURLEnvVar = "NOTIFICATION_USER_SERVICE_BASE_URL"
	userServiceTimeoutEnvVar = "NOTIFICATION_USER_SERVICE_TIMEOUT"

	adminEmailsGeoReviewRecommendedEnvVar      = "NOTIFICATION_ADMIN_EMAILS_GEO_REVIEW_RECOMMENDED"
	adminEmailsGameGenerationFailedEnvVar      = "NOTIFICATION_ADMIN_EMAILS_GAME_GENERATION_FAILED"
	adminEmailsLobbyRuntimePausedAfterEnvVar   = "NOTIFICATION_ADMIN_EMAILS_LOBBY_RUNTIME_PAUSED_AFTER_START"
	adminEmailsLobbyApplicationSubmittedEnvVar = "NOTIFICATION_ADMIN_EMAILS_LOBBY_APPLICATION_SUBMITTED"

	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         = "NOTIFICATION_OTEL_STDOUT_TRACES_ENABLED"
	otelStdoutMetricsEnabledEnvVar        = "NOTIFICATION_OTEL_STDOUT_METRICS_ENABLED"

	defaultShutdownTimeout       = 5 * time.Second
	defaultLogLevel              = "info"
	defaultInternalHTTPAddr      = ":8092"
	defaultReadHeaderTimeout     = 2 * time.Second
	defaultReadTimeout           = 10 * time.Second
	defaultIdleTimeout           = time.Minute

	defaultIntentsStream                   = "notification:intents"
	defaultIntentsReadBlockTimeout         = 2 * time.Second
	defaultGatewayClientEventsStream       = "gateway:client-events"
	defaultGatewayClientEventsStreamMaxLen int64 = 1024
	defaultMailDeliveryCommandsStream      = "mail:delivery_commands"

	defaultPushRetryMaxAttempts  = 3
	defaultEmailRetryMaxAttempts = 7
	defaultRouteLeaseTTL         = 5 * time.Second
	defaultRouteBackoffMin       = time.Second
	defaultRouteBackoffMax       = 5 * time.Minute
	defaultIdempotencyTTL        = 168 * time.Hour

	defaultRecordRetention          = 30 * 24 * time.Hour
	defaultMalformedIntentRetention = 90 * 24 * time.Hour
	defaultCleanupInterval          = time.Hour

	defaultUserServiceTimeout = time.Second
	defaultOTelServiceName    = "galaxy-notification"

	otelExporterNone         = "none"
	otelExporterOTLP         = "otlp"
	otelProtocolHTTPProtobuf = "http/protobuf"
	otelProtocolGRPC         = "grpc"
)

// Config stores the full Notification 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

	// InternalHTTP configures the private probe HTTP listener.
	InternalHTTP InternalHTTPConfig

	// Redis configures the shared Redis connection topology and the inbound
	// `notification:intents` stream plus the outbound stream names. Durable
	// notification state lives in PostgreSQL after Stage 5 of `PG_PLAN.md`.
	Redis RedisConfig

	// Postgres configures the PostgreSQL-backed durable store consumed via
	// `pkg/postgres`.
	Postgres PostgresConfig

	// Streams stores the stable Redis Stream names reserved for ingress and
	// downstream publication.
	Streams StreamsConfig

	// IntentsReadBlockTimeout stores the maximum Redis Streams blocking read
	// window used by the intent consumer.
	IntentsReadBlockTimeout time.Duration

	// Retry stores the frozen retry settings used by the route publishers.
	Retry RetryConfig

	// Retention stores the periodic SQL retention worker configuration.
	Retention RetentionConfig

	// UserService configures the trusted user-enrichment dependency.
	UserService UserServiceConfig

	// AdminRouting stores the type-specific configured administrator email
	// lists.
	AdminRouting AdminRoutingConfig

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

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

// InternalHTTPConfig configures the private probe 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 Notification Service Redis connection topology.
// Per-call timeouts live in `Conn.OperationTimeout`.
type RedisConfig struct {
	// Conn carries the connection topology (master, replicas, password, db,
	// per-call timeout). Loaded via redisconn.LoadFromEnv("NOTIFICATION").
	Conn redisconn.Config
}

// Validate reports whether cfg stores a usable Redis configuration.
func (cfg RedisConfig) Validate() error {
	return cfg.Conn.Validate()
}

// PostgresConfig configures the PostgreSQL-backed durable store.
type PostgresConfig struct {
	// Conn stores the primary plus replica DSN topology and pool tuning.
	// Loaded via postgres.LoadFromEnv("NOTIFICATION").
	Conn postgres.Config
}

// Validate reports whether cfg stores a usable PostgreSQL configuration.
func (cfg PostgresConfig) Validate() error {
	return cfg.Conn.Validate()
}

// StreamsConfig stores the stable Redis Stream names used by Notification
// Service.
type StreamsConfig struct {
	// Intents stores the ingress intent stream.
	Intents string

	// GatewayClientEvents stores the downstream Gateway client-events stream.
	GatewayClientEvents string

	// GatewayClientEventsStreamMaxLen bounds the downstream Gateway
	// client-events stream with approximate trimming.
	GatewayClientEventsStreamMaxLen int64

	// MailDeliveryCommands stores the downstream Mail Service command stream.
	MailDeliveryCommands string
}

// Validate reports whether cfg stores usable stream names.
func (cfg StreamsConfig) Validate() error {
	switch {
	case strings.TrimSpace(cfg.Intents) == "":
		return fmt.Errorf("intents stream must not be empty")
	case strings.TrimSpace(cfg.GatewayClientEvents) == "":
		return fmt.Errorf("gateway client-events stream must not be empty")
	case cfg.GatewayClientEventsStreamMaxLen <= 0:
		return fmt.Errorf("gateway client-events stream max len must be positive")
	case strings.TrimSpace(cfg.MailDeliveryCommands) == "":
		return fmt.Errorf("mail delivery-commands stream must not be empty")
	default:
		return nil
	}
}

// RetryConfig stores the frozen retry budgets, backoff settings, and the
// per-acceptance idempotency window.
type RetryConfig struct {
	// PushMaxAttempts stores the route retry budget for the `push` channel.
	PushMaxAttempts int

	// EmailMaxAttempts stores the route retry budget for the `email` channel.
	EmailMaxAttempts int

	// RouteLeaseTTL stores the temporary route-lease lifetime used to avoid
	// duplicate publication across replicas.
	RouteLeaseTTL time.Duration

	// RouteBackoffMin stores the minimum retry backoff.
	RouteBackoffMin time.Duration

	// RouteBackoffMax stores the maximum retry backoff.
	RouteBackoffMax time.Duration

	// IdempotencyTTL stores the per-acceptance idempotency window the service
	// layer applies to the durable `idempotency_expires_at` column on the
	// `records` table.
	IdempotencyTTL time.Duration
}

// Validate reports whether cfg stores usable retry settings.
func (cfg RetryConfig) Validate() error {
	switch {
	case cfg.PushMaxAttempts <= 0:
		return fmt.Errorf("push retry max attempts must be positive")
	case cfg.EmailMaxAttempts <= 0:
		return fmt.Errorf("email retry max attempts must be positive")
	case cfg.RouteLeaseTTL <= 0:
		return fmt.Errorf("route lease ttl must be positive")
	case cfg.RouteBackoffMin <= 0:
		return fmt.Errorf("route backoff min must be positive")
	case cfg.RouteBackoffMax <= 0:
		return fmt.Errorf("route backoff max must be positive")
	case cfg.RouteBackoffMin > cfg.RouteBackoffMax:
		return fmt.Errorf("route backoff min must not exceed route backoff max")
	case cfg.IdempotencyTTL <= 0:
		return fmt.Errorf("idempotency ttl must be positive")
	default:
		return nil
	}
}

// RetentionConfig stores the durable retention windows applied by the
// periodic SQL retention worker.
type RetentionConfig struct {
	// RecordRetention bounds how long records (and their cascaded routes and
	// dead_letters) survive after acceptance.
	RecordRetention time.Duration

	// MalformedIntentRetention bounds how long malformed-intent rows survive
	// after their original `recorded_at`.
	MalformedIntentRetention time.Duration

	// CleanupInterval stores the wall-clock period between two retention
	// passes.
	CleanupInterval time.Duration
}

// Validate reports whether cfg stores a usable retention configuration.
func (cfg RetentionConfig) Validate() error {
	switch {
	case cfg.RecordRetention <= 0:
		return fmt.Errorf("%s must be positive", recordRetentionEnvVar)
	case cfg.MalformedIntentRetention <= 0:
		return fmt.Errorf("%s must be positive", malformedIntentRetentionEnvVar)
	case cfg.CleanupInterval <= 0:
		return fmt.Errorf("%s must be positive", cleanupIntervalEnvVar)
	default:
		return nil
	}
}

// UserServiceConfig configures the trusted user-enrichment dependency.
type UserServiceConfig struct {
	// BaseURL stores the absolute base URL of the trusted User Service.
	BaseURL string

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

// Validate reports whether cfg stores a usable User Service configuration.
func (cfg UserServiceConfig) Validate() error {
	switch {
	case strings.TrimSpace(cfg.BaseURL) == "":
		return fmt.Errorf("user service base URL must not be empty")
	case !isAbsoluteHTTPURL(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
	}
}

// AdminRoutingConfig stores the type-specific configured administrator email
// lists.
type AdminRoutingConfig struct {
	// GeoReviewRecommended stores recipients for `geo.review_recommended`.
	GeoReviewRecommended []string

	// GameGenerationFailed stores recipients for `game.generation_failed`.
	GameGenerationFailed []string

	// LobbyRuntimePausedAfterStart stores recipients for
	// `lobby.runtime_paused_after_start`.
	LobbyRuntimePausedAfterStart []string

	// LobbyApplicationSubmitted stores recipients for public
	// `lobby.application.submitted` notifications.
	LobbyApplicationSubmitted []string
}

// Validate reports whether cfg stores valid normalized administrator email
// lists.
func (cfg AdminRoutingConfig) Validate() error {
	if err := validateNormalizedEmailList("geo.review_recommended", cfg.GeoReviewRecommended); err != nil {
		return err
	}
	if err := validateNormalizedEmailList("game.generation_failed", cfg.GameGenerationFailed); err != nil {
		return err
	}
	if err := validateNormalizedEmailList("lobby.runtime_paused_after_start", cfg.LobbyRuntimePausedAfterStart); err != nil {
		return err
	}
	if err := validateNormalizedEmailList("lobby.application.submitted", cfg.LobbyApplicationSubmitted); err != nil {
		return err
	}

	return nil
}

// TelemetryConfig configures the Notification 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 Notification Service process
// configuration.
func DefaultConfig() Config {
	return Config{
		ShutdownTimeout: defaultShutdownTimeout,
		Logging: LoggingConfig{
			Level: defaultLogLevel,
		},
		InternalHTTP: InternalHTTPConfig{
			Addr:              defaultInternalHTTPAddr,
			ReadHeaderTimeout: defaultReadHeaderTimeout,
			ReadTimeout:       defaultReadTimeout,
			IdleTimeout:       defaultIdleTimeout,
		},
		Redis: RedisConfig{
			Conn: redisconn.DefaultConfig(),
		},
		Postgres: PostgresConfig{
			Conn: postgres.DefaultConfig(),
		},
		Streams: StreamsConfig{
			Intents:                         defaultIntentsStream,
			GatewayClientEvents:             defaultGatewayClientEventsStream,
			GatewayClientEventsStreamMaxLen: defaultGatewayClientEventsStreamMaxLen,
			MailDeliveryCommands:            defaultMailDeliveryCommandsStream,
		},
		IntentsReadBlockTimeout: defaultIntentsReadBlockTimeout,
		Retry: RetryConfig{
			PushMaxAttempts:  defaultPushRetryMaxAttempts,
			EmailMaxAttempts: defaultEmailRetryMaxAttempts,
			RouteLeaseTTL:    defaultRouteLeaseTTL,
			RouteBackoffMin:  defaultRouteBackoffMin,
			RouteBackoffMax:  defaultRouteBackoffMax,
			IdempotencyTTL:   defaultIdempotencyTTL,
		},
		Retention: RetentionConfig{
			RecordRetention:          defaultRecordRetention,
			MalformedIntentRetention: defaultMalformedIntentRetention,
			CleanupInterval:          defaultCleanupInterval,
		},
		UserService: UserServiceConfig{
			Timeout: defaultUserServiceTimeout,
		},
		Telemetry: TelemetryConfig{
			ServiceName:     defaultOTelServiceName,
			TracesExporter:  otelExporterNone,
			MetricsExporter: otelExporterNone,
		},
	}
}

// Validate reports whether cfg contains a consistent Notification Service
// process configuration.
func (cfg Config) Validate() error {
	if cfg.ShutdownTimeout <= 0 {
		return fmt.Errorf("load notification config: %s must be positive", shutdownTimeoutEnvVar)
	}

	if err := cfg.InternalHTTP.Validate(); err != nil {
		return fmt.Errorf("load notification config: %s", err)
	}
	if err := cfg.Redis.Validate(); err != nil {
		return fmt.Errorf("load notification config: %w", err)
	}
	if err := cfg.Postgres.Validate(); err != nil {
		return fmt.Errorf("load notification config: %w", err)
	}
	if err := cfg.Streams.Validate(); err != nil {
		return fmt.Errorf("load notification config: %s", err)
	}
	if cfg.IntentsReadBlockTimeout <= 0 {
		return fmt.Errorf("load notification config: %s must be positive", intentsReadBlockTimeoutEnvVar)
	}
	if err := cfg.Retry.Validate(); err != nil {
		return fmt.Errorf("load notification config: %s", err)
	}
	if err := cfg.Retention.Validate(); err != nil {
		return fmt.Errorf("load notification config: %s", err)
	}
	if err := cfg.UserService.Validate(); err != nil {
		return fmt.Errorf("load notification config: %s", err)
	}
	if err := cfg.AdminRouting.Validate(); err != nil {
		return fmt.Errorf("load notification config: %s", err)
	}
	if err := cfg.Telemetry.Validate(); err != nil {
		return fmt.Errorf("load notification config: %w", err)
	}

	return nil
}

func validateNormalizedEmailList(name string, values []string) error {
	for index, value := range values {
		normalized, err := normalizeMailboxAddress(value)
		if err != nil {
			return fmt.Errorf("%s[%d]: %w", name, index, err)
		}
		if normalized != value {
			return fmt.Errorf("%s[%d]: email address must already be normalized", name, index)
		}
	}

	return nil
}

func normalizeMailboxAddress(value string) (string, error) {
	trimmed := strings.TrimSpace(value)
	if trimmed == "" {
		return "", fmt.Errorf("email address must not be empty")
	}

	parsed, err := netmail.ParseAddress(trimmed)
	if err != nil {
		return "", fmt.Errorf("invalid email address %q: %w", trimmed, err)
	}
	if parsed.Name != "" {
		return "", fmt.Errorf("email address %q must not include a display name", trimmed)
	}

	return strings.ToLower(parsed.Address), nil
}

func parseEmailList(name string, raw string) ([]string, error) {
	trimmed := strings.TrimSpace(raw)
	if trimmed == "" {
		return nil, nil
	}

	parts := strings.Split(trimmed, ",")
	addresses := make([]string, 0, len(parts))
	seen := make(map[string]struct{}, len(parts))
	for index, part := range parts {
		normalized, err := normalizeMailboxAddress(part)
		if err != nil {
			return nil, fmt.Errorf("%s[%d]: %w", name, index, err)
		}
		if _, ok := seen[normalized]; ok {
			continue
		}
		seen[normalized] = struct{}{}
		addresses = append(addresses, normalized)
	}

	return addresses, nil
}

func normalizeBaseURL(value string) string {
	trimmed := strings.TrimSpace(value)
	if trimmed == "" {
		return ""
	}

	return strings.TrimRight(trimmed, "/")
}

func isAbsoluteHTTPURL(value string) bool {
	parsed, err := url.Parse(strings.TrimSpace(value))
	if err != nil {
		return false
	}

	if parsed.Scheme != "http" && parsed.Scheme != "https" {
		return false
	}

	return parsed.Host != ""
}

func isTCPAddr(value string) bool {
	host, port, err := net.SplitHostPort(strings.TrimSpace(value))
	if err != nil {
		return false
	}

	if port == "" {
		return false
	}
	if host == "" {
		return true
	}

	return true
}