package config

import (
	"fmt"
	"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
// `MAIL_REDIS_TLS_ENABLED` / `MAIL_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
	cfg.Redis.CommandStream = stringEnv(redisCommandStreamEnvVar, cfg.Redis.CommandStream)

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

	cfg.SMTP.Mode = stringEnv(smtpModeEnvVar, cfg.SMTP.Mode)
	cfg.SMTP.Addr = stringEnv(smtpAddrEnvVar, cfg.SMTP.Addr)
	cfg.SMTP.Username = stringEnv(smtpUsernameEnvVar, cfg.SMTP.Username)
	cfg.SMTP.Password = stringEnv(smtpPasswordEnvVar, cfg.SMTP.Password)
	cfg.SMTP.FromEmail = stringEnv(smtpFromEmailEnvVar, cfg.SMTP.FromEmail)
	cfg.SMTP.FromName = stringEnv(smtpFromNameEnvVar, cfg.SMTP.FromName)
	cfg.SMTP.Timeout, err = durationEnv(smtpTimeoutEnvVar, cfg.SMTP.Timeout)
	if err != nil {
		return Config{}, err
	}
	cfg.SMTP.InsecureSkipVerify, err = boolEnv(smtpInsecureSkipVerifyEnvVar, cfg.SMTP.InsecureSkipVerify)
	if err != nil {
		return Config{}, err
	}

	cfg.Templates.Dir = stringEnv(templateDirEnvVar, cfg.Templates.Dir)

	cfg.AttemptWorkerConcurrency, err = intEnv(attemptWorkerConcurrencyEnvVar, cfg.AttemptWorkerConcurrency)
	if err != nil {
		return Config{}, err
	}
	cfg.StreamBlockTimeout, err = durationEnv(streamBlockTimeoutEnvVar, cfg.StreamBlockTimeout)
	if err != nil {
		return Config{}, err
	}
	cfg.OperatorRequestTimeout, err = durationEnv(operatorRequestTimeoutEnvVar, cfg.OperatorRequestTimeout)
	if err != nil {
		return Config{}, err
	}
	cfg.IdempotencyTTL, err = durationEnv(idempotencyTTLEnvVar, cfg.IdempotencyTTL)
	if err != nil {
		return Config{}, err
	}
	cfg.Retention.DeliveryRetention, err = durationEnv(deliveryRetentionEnvVar, cfg.Retention.DeliveryRetention)
	if err != nil {
		return Config{}, err
	}
	cfg.Retention.MalformedCommandRetention, err = durationEnv(malformedCommandRetentionEnvVar, cfg.Retention.MalformedCommandRetention)
	if err != nil {
		return Config{}, err
	}
	cfg.Retention.CleanupInterval, err = durationEnv(cleanupIntervalEnvVar, cfg.Retention.CleanupInterval)
	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 = normalizeProtocolValue(
		os.Getenv(otelExporterOTLPTracesProtocolEnvVar),
		os.Getenv(otelExporterOTLPProtocolEnvVar),
		cfg.Telemetry.TracesProtocol,
	)
	cfg.Telemetry.MetricsProtocol = normalizeProtocolValue(
		os.Getenv(otelExporterOTLPMetricsProtocolEnvVar),
		os.Getenv(otelExporterOTLPProtocolEnvVar),
		cfg.Telemetry.MetricsProtocol,
	)
	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 := validateSlogLevel(cfg.Logging.Level); err != nil {
		return Config{}, fmt.Errorf("%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: parse duration: %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: parse int: %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: parse bool: %w", name, err)
	}

	return parsed, nil
}

func normalizeExporterValue(value string) string {
	trimmed := strings.TrimSpace(value)
	switch trimmed {
	case "", "none":
		return "none"
	default:
		return trimmed
	}
}

func normalizeProtocolValue(primary string, fallback string, defaultValue string) string {
	primary = strings.TrimSpace(primary)
	if primary != "" {
		return primary
	}

	fallback = strings.TrimSpace(fallback)
	if fallback != "" {
		return fallback
	}

	return strings.TrimSpace(defaultValue)
}