package config

import (
	"fmt"
	"log/slog"
	"net"
	"net/mail"
	"strings"
)

// Validate reports whether cfg stores a usable Mail Service process
// configuration.
func (cfg Config) Validate() error {
	switch {
	case cfg.ShutdownTimeout <= 0:
		return fmt.Errorf("%s must be positive", shutdownTimeoutEnvVar)
	case cfg.AttemptWorkerConcurrency <= 0:
		return fmt.Errorf("%s must be positive", attemptWorkerConcurrencyEnvVar)
	case cfg.StreamBlockTimeout <= 0:
		return fmt.Errorf("%s must be positive", streamBlockTimeoutEnvVar)
	case cfg.OperatorRequestTimeout <= 0:
		return fmt.Errorf("%s must be positive", operatorRequestTimeoutEnvVar)
	case cfg.IdempotencyTTL <= 0:
		return fmt.Errorf("%s must be positive", idempotencyTTLEnvVar)
	}

	if err := cfg.InternalHTTP.Validate(); err != nil {
		return err
	}
	if err := cfg.Redis.Validate(); err != nil {
		return err
	}
	if err := cfg.Postgres.Validate(); err != nil {
		return fmt.Errorf("postgres: %w", err)
	}
	if err := cfg.Retention.Validate(); err != nil {
		return err
	}
	if err := cfg.SMTP.Validate(); err != nil {
		return err
	}
	if err := cfg.Templates.Validate(); err != nil {
		return err
	}
	if err := cfg.Telemetry.Validate(); err != nil {
		return err
	}

	return nil
}

func validateSlogLevel(level string) error {
	var slogLevel slog.Level
	if err := slogLevel.UnmarshalText([]byte(strings.TrimSpace(level))); err != nil {
		return fmt.Errorf("invalid slog level %q: %w", level, err)
	}

	return nil
}

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 !strings.Contains(host, " ")
}

func validateMailbox(name string, value string) error {
	trimmed := strings.TrimSpace(value)
	if trimmed == "" {
		return fmt.Errorf("%s must not be empty", name)
	}

	parsed, err := mail.ParseAddress(trimmed)
	if err != nil || parsed == nil || parsed.Name != "" || parsed.Address != trimmed {
		return fmt.Errorf("%s %q must be a single valid email address", name, value)
	}

	return nil
}