package barkfile

import (
	"errors"
	"fmt"
	"net"
	"regexp"
	"strconv"
	"strings"
)

// NormalizeHostname returns the canonical lookup form for a DNS hostname.
func NormalizeHostname(hostname string) string {
	return strings.TrimSuffix(strings.ToLower(strings.TrimSpace(hostname)), ".")
}

const DockerSecretPrefix = "barkstack_"

var secretReferencePattern = regexp.MustCompile(`^[a-z][a-z0-9_]*$`)

// DockerSecretName returns the namespaced Docker object name for a validated
// short Barkfile secret reference.
func DockerSecretName(reference string) string {
	return DockerSecretPrefix + reference
}

// Validate verifies configuration invariants that do not require opening files.
func (c Config) Validate() error {
	var errs []error
	if strings.TrimSpace(c.Listen) == "" {
		errs = append(errs, errors.New("listen address is required"))
	} else if err := validateListenAddress(c.Listen); err != nil {
		errs = append(errs, fmt.Errorf("listen address %q: %w", c.Listen, err))
	}
	certificateSet := strings.TrimSpace(c.TLS.CertFile) != ""
	keySet := strings.TrimSpace(c.TLS.KeyFile) != ""
	if certificateSet != keySet {
		errs = append(errs, errors.New("tls requires both cert and key"))
	}
	if len(c.Databases) == 0 {
		errs = append(errs, errors.New("at least one database route is required"))
	}

	seenHostnames := make(map[string]string, len(c.Databases))
	seenNames := make(map[string]struct{}, len(c.Databases))
	for _, database := range c.Databases {
		name := strings.TrimSpace(database.Name)
		if name == "" {
			errs = append(errs, errors.New("database name is required"))
		} else if _, exists := seenNames[name]; exists {
			errs = append(errs, fmt.Errorf("duplicate database name %q", name))
		} else {
			seenNames[name] = struct{}{}
		}
		hostname := NormalizeHostname(database.Hostname)
		if hostname != "" {
			if existing, ok := seenHostnames[hostname]; ok {
				errs = append(errs, fmt.Errorf("duplicate hostname %q for databases %q and %q", hostname, existing, name))
			} else {
				seenHostnames[hostname] = name
			}
		}
		if database.Postgres != nil {
			if database.Upstream != "" {
				errs = append(errs, fmt.Errorf("database %q: upstream and postgres cannot both be configured", name))
			}
			if err := validatePostgres(*database.Postgres); err != nil {
				errs = append(errs, fmt.Errorf("database %q: postgres: %w", name, err))
			}
		} else if strings.TrimSpace(database.Upstream) == "" {
			errs = append(errs, fmt.Errorf("database %q: upstream or postgres is required", name))
		} else if err := validateAddress(database.Upstream); err != nil {
			errs = append(errs, fmt.Errorf("database %q: upstream %q: %w", name, database.Upstream, err))
		}
	}
	return errors.Join(errs...)
}

func validatePostgres(postgres PostgresConfig) error {
	switch postgres.Image {
	case "postgres:16", "postgres:17", "postgres:18":
	default:
		return fmt.Errorf("image %q must be postgres:16, postgres:17, or postgres:18", postgres.Image)
	}
	if strings.TrimSpace(postgres.Volume) == "" {
		return errors.New("volume is required")
	}
	if !ValidSecretReference(postgres.PasswordSecret) {
		return fmt.Errorf("password_secret %q must start with a lowercase letter, contain only lowercase letters, digits, or underscores, and be at most 54 characters", postgres.PasswordSecret)
	}
	if postgres.IdleTimeout < 0 {
		return errors.New("idle_timeout cannot be negative")
	}
	if postgres.TrafficIdleTimeout < 0 {
		return errors.New("traffic_idle_timeout cannot be negative")
	}
	return nil
}

// ValidSecretReference reports whether reference is safe for use as a short
// Barkfile secret name and as part of a Docker secret name.
func ValidSecretReference(reference string) bool {
	return len(reference) <= 54 && secretReferencePattern.MatchString(reference)
}

func validateListenAddress(address string) error {
	_, port, err := net.SplitHostPort(address)
	if err != nil {
		return err
	}
	portNumber, err := strconv.ParseUint(port, 10, 16)
	if err != nil || portNumber == 0 {
		return errors.New("port must be between 1 and 65535")
	}
	return nil
}

func validateAddress(address string) error {
	host, port, err := net.SplitHostPort(address)
	if err != nil {
		return err
	}
	if strings.TrimSpace(host) == "" {
		return errors.New("host is required")
	}
	portNumber, err := strconv.ParseUint(port, 10, 16)
	if err != nil || portNumber == 0 {
		return errors.New("port must be between 1 and 65535")
	}
	return nil
}