package config

import (
	"fmt"
	"log/slog"
	"os"
	"strconv"
	"strings"
	"time"

	"galaxy/postgres"
	"galaxy/redisconn"
)

// LoadFromEnv builds Config from environment variables and validates the
// resulting configuration. Connection topology for Redis and PostgreSQL is
// delegated to the shared `pkg/redisconn` and `pkg/postgres` LoadFromEnv
// helpers — the Redis loader hard-fails on the deprecated
// `NOTIFICATION_REDIS_TLS_ENABLED` / `NOTIFICATION_REDIS_USERNAME` env vars;
// the Postgres loader requires a primary DSN.
func LoadFromEnv() (Config, error) {
	cfg := DefaultConfig()

	var err error

	cfg.ShutdownTimeout, err = durationEnv(shutdownTimeoutEnvVar, cfg.ShutdownTimeout)
	if err != nil {
		return Config{}, err
	}

	cfg.Logging.Level = stringEnv(logLevelEnvVar, cfg.Logging.Level)

	cfg.InternalHTTP.Addr = stringEnv(internalHTTPAddrEnvVar, cfg.InternalHTTP.Addr)
	cfg.InternalHTTP.ReadHeaderTimeout, err = durationEnv(internalHTTPReadHeaderTimeoutEnvVar, cfg.InternalHTTP.ReadHeaderTimeout)
	if err != nil {
		return Config{}, err
	}
	cfg.InternalHTTP.ReadTimeout, err = durationEnv(internalHTTPReadTimeoutEnvVar, cfg.InternalHTTP.ReadTimeout)
	if err != nil {
		return Config{}, err
	}
	cfg.InternalHTTP.IdleTimeout, err = durationEnv(internalHTTPIdleTimeoutEnvVar, cfg.InternalHTTP.IdleTimeout)
	if err != nil {
		return Config{}, err
	}

	redisConn, err := redisconn.LoadFromEnv(envPrefix)
	if err != nil {
		return Config{}, err
	}
	cfg.Redis.Conn = redisConn

	pgConn, err := postgres.LoadFromEnv(envPrefix)
	if err != nil {
		return Config{}, err
	}
	cfg.Postgres.Conn = pgConn

	cfg.Streams.Intents = stringEnv(intentsStreamEnvVar, cfg.Streams.Intents)
	cfg.Streams.GatewayClientEvents = stringEnv(gatewayClientEventsStreamEnvVar, cfg.Streams.GatewayClientEvents)
	cfg.Streams.GatewayClientEventsStreamMaxLen, err = int64Env(gatewayClientEventsStreamMaxEnvVar, cfg.Streams.GatewayClientEventsStreamMaxLen)
	if err != nil {
		return Config{}, err
	}
	cfg.Streams.MailDeliveryCommands = stringEnv(mailDeliveryCommandsStreamEnvVar, cfg.Streams.MailDeliveryCommands)
	cfg.IntentsReadBlockTimeout, err = durationEnv(intentsReadBlockTimeoutEnvVar, cfg.IntentsReadBlockTimeout)
	if err != nil {
		return Config{}, err
	}

	cfg.Retry.PushMaxAttempts, err = intEnv(pushRetryMaxAttemptsEnvVar, cfg.Retry.PushMaxAttempts)
	if err != nil {
		return Config{}, err
	}
	cfg.Retry.EmailMaxAttempts, err = intEnv(emailRetryMaxAttemptsEnvVar, cfg.Retry.EmailMaxAttempts)
	if err != nil {
		return Config{}, err
	}
	cfg.Retry.RouteLeaseTTL, err = durationEnv(routeLeaseTTLEnvVar, cfg.Retry.RouteLeaseTTL)
	if err != nil {
		return Config{}, err
	}
	cfg.Retry.RouteBackoffMin, err = durationEnv(routeBackoffMinEnvVar, cfg.Retry.RouteBackoffMin)
	if err != nil {
		return Config{}, err
	}
	cfg.Retry.RouteBackoffMax, err = durationEnv(routeBackoffMaxEnvVar, cfg.Retry.RouteBackoffMax)
	if err != nil {
		return Config{}, err
	}
	cfg.Retry.IdempotencyTTL, err = durationEnv(idempotencyTTLEnvVar, cfg.Retry.IdempotencyTTL)
	if err != nil {
		return Config{}, err
	}

	cfg.Retention.RecordRetention, err = durationEnv(recordRetentionEnvVar, cfg.Retention.RecordRetention)
	if err != nil {
		return Config{}, err
	}
	cfg.Retention.MalformedIntentRetention, err = durationEnv(malformedIntentRetentionEnvVar, cfg.Retention.MalformedIntentRetention)
	if err != nil {
		return Config{}, err
	}
	cfg.Retention.CleanupInterval, err = durationEnv(cleanupIntervalEnvVar, cfg.Retention.CleanupInterval)
	if err != nil {
		return Config{}, err
	}

	cfg.UserService.BaseURL = normalizeBaseURL(stringEnv(userServiceBaseURLEnvVar, cfg.UserService.BaseURL))
	cfg.UserService.Timeout, err = durationEnv(userServiceTimeoutEnvVar, cfg.UserService.Timeout)
	if err != nil {
		return Config{}, err
	}

	cfg.AdminRouting.GeoReviewRecommended, err = emailListEnv(adminEmailsGeoReviewRecommendedEnvVar, cfg.AdminRouting.GeoReviewRecommended)
	if err != nil {
		return Config{}, err
	}
	cfg.AdminRouting.GameGenerationFailed, err = emailListEnv(adminEmailsGameGenerationFailedEnvVar, cfg.AdminRouting.GameGenerationFailed)
	if err != nil {
		return Config{}, err
	}
	cfg.AdminRouting.LobbyRuntimePausedAfterStart, err = emailListEnv(adminEmailsLobbyRuntimePausedAfterEnvVar, cfg.AdminRouting.LobbyRuntimePausedAfterStart)
	if err != nil {
		return Config{}, err
	}
	cfg.AdminRouting.LobbyApplicationSubmitted, err = emailListEnv(adminEmailsLobbyApplicationSubmittedEnvVar, cfg.AdminRouting.LobbyApplicationSubmitted)
	if err != nil {
		return Config{}, err
	}

	cfg.Telemetry.ServiceName = stringEnv(otelServiceNameEnvVar, cfg.Telemetry.ServiceName)
	cfg.Telemetry.TracesExporter = normalizeExporterValue(stringEnv(otelTracesExporterEnvVar, cfg.Telemetry.TracesExporter))
	cfg.Telemetry.MetricsExporter = normalizeExporterValue(stringEnv(otelMetricsExporterEnvVar, cfg.Telemetry.MetricsExporter))
	cfg.Telemetry.TracesProtocol = loadOTLPProtocol(
		os.Getenv(otelExporterOTLPTracesProtocolEnvVar),
		os.Getenv(otelExporterOTLPProtocolEnvVar),
		cfg.Telemetry.TracesExporter,
	)
	cfg.Telemetry.MetricsProtocol = loadOTLPProtocol(
		os.Getenv(otelExporterOTLPMetricsProtocolEnvVar),
		os.Getenv(otelExporterOTLPProtocolEnvVar),
		cfg.Telemetry.MetricsExporter,
	)
	cfg.Telemetry.StdoutTracesEnabled, err = boolEnv(otelStdoutTracesEnabledEnvVar, cfg.Telemetry.StdoutTracesEnabled)
	if err != nil {
		return Config{}, err
	}
	cfg.Telemetry.StdoutMetricsEnabled, err = boolEnv(otelStdoutMetricsEnabledEnvVar, cfg.Telemetry.StdoutMetricsEnabled)
	if err != nil {
		return Config{}, err
	}

	if err := validateLogLevel(cfg.Logging.Level); err != nil {
		return Config{}, fmt.Errorf("load notification config: %s: %w", logLevelEnvVar, err)
	}
	if err := cfg.Validate(); err != nil {
		return Config{}, err
	}

	return cfg, nil
}

func stringEnv(name string, fallback string) string {
	value, ok := os.LookupEnv(name)
	if !ok {
		return fallback
	}

	return strings.TrimSpace(value)
}

func durationEnv(name string, fallback time.Duration) (time.Duration, error) {
	value, ok := os.LookupEnv(name)
	if !ok {
		return fallback, nil
	}

	parsed, err := time.ParseDuration(strings.TrimSpace(value))
	if err != nil {
		return 0, fmt.Errorf("%s: %w", name, err)
	}

	return parsed, nil
}

func intEnv(name string, fallback int) (int, error) {
	value, ok := os.LookupEnv(name)
	if !ok {
		return fallback, nil
	}

	parsed, err := strconv.Atoi(strings.TrimSpace(value))
	if err != nil {
		return 0, fmt.Errorf("%s: %w", name, err)
	}

	return parsed, nil
}

func int64Env(name string, fallback int64) (int64, error) {
	value, ok := os.LookupEnv(name)
	if !ok {
		return fallback, nil
	}

	parsed, err := strconv.ParseInt(strings.TrimSpace(value), 10, 64)
	if err != nil {
		return 0, fmt.Errorf("%s: %w", name, err)
	}

	return parsed, nil
}

func boolEnv(name string, fallback bool) (bool, error) {
	value, ok := os.LookupEnv(name)
	if !ok {
		return fallback, nil
	}

	parsed, err := strconv.ParseBool(strings.TrimSpace(value))
	if err != nil {
		return false, fmt.Errorf("%s: %w", name, err)
	}

	return parsed, nil
}

func emailListEnv(name string, fallback []string) ([]string, error) {
	raw, ok := os.LookupEnv(name)
	if !ok {
		return append([]string(nil), fallback...), nil
	}

	return parseEmailList(name, raw)
}

func validateLogLevel(value string) error {
	var level slog.Level
	return level.UnmarshalText([]byte(strings.TrimSpace(value)))
}

func normalizeExporterValue(value string) string {
	switch strings.TrimSpace(value) {
	case "", otelExporterNone:
		return otelExporterNone
	default:
		return strings.TrimSpace(value)
	}
}

func loadOTLPProtocol(primary string, fallback string, exporter string) string {
	protocol := strings.TrimSpace(primary)
	if protocol == "" {
		protocol = strings.TrimSpace(fallback)
	}
	if protocol == "" && exporter == otelExporterOTLP {
		return otelProtocolHTTPProtobuf
	}

	return protocol
}