package certificate

import (
	"crypto/x509"
	"encoding/pem"
	"fmt"
	"os"
	"path/filepath"
	"time"

	"git.secnex.io/secnex/certman/certificate/utils"
	"git.secnex.io/secnex/certman/models"
	"git.secnex.io/secnex/certman/repositories"
	"github.com/google/uuid"
	"gorm.io/gorm"
)

// CertificateAuthorityService handles certificate authority operations
type CertificateAuthorityService struct {
	caRepo     *repositories.CertificateAuthorityRepository
	orgRepo    *repositories.OrganizationRepository
	certDir    string
	privateDir string
}

// NewCertificateAuthorityService creates a new certificate authority service
func NewCertificateAuthorityService(
	db *gorm.DB,
	certDir string,
	privateDir string,
) *CertificateAuthorityService {
	return &CertificateAuthorityService{
		caRepo:     repositories.NewCertificateAuthorityRepository(db),
		orgRepo:    repositories.NewOrganizationRepository(db),
		certDir:    certDir,
		privateDir: privateDir,
	}
}

// CreateRootCA creates a new root certificate authority
func (s *CertificateAuthorityService) CreateRootCA(req *CreateRootCARequest) (*models.CertificateAuthority, error) {
	// Validate request
	if err := s.validateRootCARequest(req); err != nil {
		return nil, fmt.Errorf("invalid request: %w", err)
	}

	// Check if organization exists
	org, err := s.orgRepo.GetByID(req.OrganizationID.String())
	if err != nil {
		return nil, fmt.Errorf("organization not found: %w", err)
	}

	// Check if root CA already exists for this organization
	existingCAs, err := s.caRepo.GetAll()
	if err != nil {
		return nil, fmt.Errorf("failed to check existing CAs: %w", err)
	}

	for _, ca := range existingCAs {
		if ca.Root && ca.OrganizationID == req.OrganizationID {
			return nil, fmt.Errorf("root CA already exists for organization %s", org.Name)
		}
	}

	// Create certificate configuration
	var config *utils.CertificateConfig
	if req.ValidityYears > 0 {
		config = utils.CACertificateConfigWithValidity(true, req.ValidityYears) // true = isRoot
	} else {
		config = utils.CACertificateConfig(true) // true = isRoot
	}
	config.CommonName = req.CommonName
	config.Organization = org.Name
	config.OrganizationalUnit = req.OrganizationalUnit
	config.Country = req.Country
	config.State = req.State
	config.Locality = req.Locality
	config.Street = req.Street
	config.PostalCode = req.PostalCode
	config.Email = req.Email

	// Validate configuration
	if err := utils.ValidateCertificateConfig(config); err != nil {
		return nil, fmt.Errorf("invalid certificate configuration: %w", err)
	}

	// Generate certificate and private key
	generator := utils.NewCertificateGenerator(config)
	cert, privateKey, err := generator.GenerateSelfSignedCertificate()
	if err != nil {
		return nil, fmt.Errorf("failed to generate root CA certificate: %w", err)
	}

	// Save certificate and private key to files
	certFileID, err := s.saveCertificate(cert, "root-ca")
	if err != nil {
		return nil, fmt.Errorf("failed to save certificate: %w", err)
	}

	privateKeyFileID, err := s.savePrivateKey(privateKey, "root-ca")
	if err != nil {
		return nil, fmt.Errorf("failed to save private key: %w", err)
	}

	// Create CA model
	ca := &models.CertificateAuthority{
		Name:                      req.Name,
		Description:               req.Description,
		SerialNumber:              cert.SerialNumber.String(),
		AttributeCommonName:       cert.Subject.CommonName,
		AttributeOrganization:     cert.Subject.Organization[0],
		AttributeOrganizationUnit: cert.Subject.OrganizationalUnit[0],
		AttributeCountry:          cert.Subject.Country[0],
		AttributeState:            cert.Subject.Province[0],
		AttributeLocality:         cert.Subject.Locality[0],
		AttributeStreet:           cert.Subject.StreetAddress[0],
		AttributeEmail:            req.Email,
		AttributeAddress:          req.Address,
		AttributePostalCode:       cert.Subject.PostalCode[0],
		AttributeNotBefore:        cert.NotBefore,
		AttributeNotAfter:         cert.NotAfter,
		Root:                      true,
		ParentID:                  nil, // Root CA has no parent
		OrganizationID:            req.OrganizationID,
		FileID:                    certFileID,
		PrivateKeyID:              privateKeyFileID,
	}

	// Save to database
	createdCA, err := s.caRepo.Create(*ca)
	if err != nil {
		// Clean up files if database save fails
		s.cleanupFiles(certFileID, privateKeyFileID)
		return nil, fmt.Errorf("failed to save CA to database: %w", err)
	}

	return &createdCA, nil
}

// CreateIntermediateCA creates a new intermediate certificate authority
func (s *CertificateAuthorityService) CreateIntermediateCA(req *CreateIntermediateCARequest) (*models.CertificateAuthority, error) {
	// Validate request
	if err := s.validateIntermediateCARequest(req); err != nil {
		return nil, fmt.Errorf("invalid request: %w", err)
	}

	// Check if organization exists
	org, err := s.orgRepo.GetByID(req.OrganizationID.String())
	if err != nil {
		return nil, fmt.Errorf("organization not found: %w", err)
	}

	// Get parent CA
	parentCA, err := s.caRepo.GetByID(req.ParentCAID.String())
	if err != nil {
		return nil, fmt.Errorf("parent CA not found: %w", err)
	}

	// Load parent CA certificate and private key
	parentCert, parentPrivateKey, err := s.loadCACertificateAndKey(&parentCA)
	if err != nil {
		return nil, fmt.Errorf("failed to load parent CA certificate: %w", err)
	}

	// Create certificate configuration
	var config *utils.CertificateConfig
	if req.ValidityYears > 0 {
		config = utils.CACertificateConfigWithValidity(false, req.ValidityYears) // false = not root
	} else {
		config = utils.CACertificateConfig(false) // false = not root
	}
	config.CommonName = req.CommonName
	config.Organization = org.Name
	config.OrganizationalUnit = req.OrganizationalUnit
	config.Country = req.Country
	config.State = req.State
	config.Locality = req.Locality
	config.Street = req.Street
	config.PostalCode = req.PostalCode
	config.Email = req.Email

	// Validate configuration
	if err := utils.ValidateCertificateConfig(config); err != nil {
		return nil, fmt.Errorf("invalid certificate configuration: %w", err)
	}

	// Generate certificate and private key
	generator := utils.NewCertificateGenerator(config)
	cert, privateKey, err := generator.GenerateCertificate(parentCert, parentPrivateKey)
	if err != nil {
		return nil, fmt.Errorf("failed to generate intermediate CA certificate: %w", err)
	}

	// Save certificate and private key to files
	certFileID, err := s.saveCertificate(cert, "intermediate-ca")
	if err != nil {
		return nil, fmt.Errorf("failed to save certificate: %w", err)
	}

	privateKeyFileID, err := s.savePrivateKey(privateKey, "intermediate-ca")
	if err != nil {
		return nil, fmt.Errorf("failed to save private key: %w", err)
	}

	// Create CA model
	ca := &models.CertificateAuthority{
		Name:                      req.Name,
		Description:               req.Description,
		SerialNumber:              cert.SerialNumber.String(),
		AttributeCommonName:       cert.Subject.CommonName,
		AttributeOrganization:     cert.Subject.Organization[0],
		AttributeOrganizationUnit: cert.Subject.OrganizationalUnit[0],
		AttributeCountry:          cert.Subject.Country[0],
		AttributeState:            cert.Subject.Province[0],
		AttributeLocality:         cert.Subject.Locality[0],
		AttributeStreet:           cert.Subject.StreetAddress[0],
		AttributeEmail:            req.Email,
		AttributeAddress:          req.Address,
		AttributePostalCode:       cert.Subject.PostalCode[0],
		AttributeNotBefore:        cert.NotBefore,
		AttributeNotAfter:         cert.NotAfter,
		Root:                      false,
		ParentID:                  &req.ParentCAID,
		OrganizationID:            req.OrganizationID,
		FileID:                    certFileID,
		PrivateKeyID:              privateKeyFileID,
	}

	// Save to database
	createdCA, err := s.caRepo.Create(*ca)
	if err != nil {
		// Clean up files if database save fails
		s.cleanupFiles(certFileID, privateKeyFileID)
		return nil, fmt.Errorf("failed to save CA to database: %w", err)
	}

	return &createdCA, nil
}

// GetCA retrieves a certificate authority by ID
func (s *CertificateAuthorityService) GetCA(id string) (*models.CertificateAuthority, error) {
	ca, err := s.caRepo.GetByID(id)
	if err != nil {
		return nil, fmt.Errorf("CA not found: %w", err)
	}
	return &ca, nil
}

// GetAllCAs retrieves all certificate authorities
func (s *CertificateAuthorityService) GetAllCAs() ([]models.CertificateAuthority, error) {
	cas, err := s.caRepo.GetAll()
	if err != nil {
		return nil, fmt.Errorf("failed to retrieve CAs: %w", err)
	}
	return cas, nil
}

// GetRootCAs retrieves all root certificate authorities
func (s *CertificateAuthorityService) GetRootCAs() ([]models.CertificateAuthority, error) {
	allCAs, err := s.caRepo.GetAll()
	if err != nil {
		return nil, fmt.Errorf("failed to retrieve CAs: %w", err)
	}

	var rootCAs []models.CertificateAuthority
	for _, ca := range allCAs {
		if ca.Root {
			rootCAs = append(rootCAs, ca)
		}
	}

	return rootCAs, nil
}

// GetIntermediateCAs retrieves all intermediate certificate authorities
func (s *CertificateAuthorityService) GetIntermediateCAs() ([]models.CertificateAuthority, error) {
	allCAs, err := s.caRepo.GetAll()
	if err != nil {
		return nil, fmt.Errorf("failed to retrieve CAs: %w", err)
	}

	var intermediateCAs []models.CertificateAuthority
	for _, ca := range allCAs {
		if !ca.Root {
			intermediateCAs = append(intermediateCAs, ca)
		}
	}

	return intermediateCAs, nil
}

// GetCAByParent retrieves all certificate authorities under a specific parent
func (s *CertificateAuthorityService) GetCAByParent(parentID string) ([]models.CertificateAuthority, error) {
	allCAs, err := s.caRepo.GetAll()
	if err != nil {
		return nil, fmt.Errorf("failed to retrieve CAs: %w", err)
	}

	var childCAs []models.CertificateAuthority
	for _, ca := range allCAs {
		if ca.ParentID != nil && ca.ParentID.String() == parentID {
			childCAs = append(childCAs, ca)
		}
	}

	return childCAs, nil
}

// GetCACertificate retrieves the certificate for a CA
func (s *CertificateAuthorityService) GetCACertificate(caID string) (*x509.Certificate, error) {
	ca, err := s.caRepo.GetByID(caID)
	if err != nil {
		return nil, fmt.Errorf("CA not found: %w", err)
	}

	cert, _, err := s.loadCACertificateAndKey(&ca)
	if err != nil {
		return nil, fmt.Errorf("failed to load CA certificate: %w", err)
	}

	return cert, nil
}

// GetCAPrivateKey retrieves the private key for a CA
func (s *CertificateAuthorityService) GetCAPrivateKey(caID string) (interface{}, error) {
	ca, err := s.caRepo.GetByID(caID)
	if err != nil {
		return nil, fmt.Errorf("CA not found: %w", err)
	}

	_, privateKey, err := s.loadCACertificateAndKey(&ca)
	if err != nil {
		return nil, fmt.Errorf("failed to load CA private key: %w", err)
	}

	return privateKey, nil
}

// UpdateCA updates a certificate authority
func (s *CertificateAuthorityService) UpdateCA(ca *models.CertificateAuthority) error {
	return s.caRepo.Update(*ca)
}

// DeleteCA deletes a certificate authority
func (s *CertificateAuthorityService) DeleteCA(caID string) error {
	ca, err := s.caRepo.GetByID(caID)
	if err != nil {
		return fmt.Errorf("CA not found: %w", err)
	}

	// Check if CA has children
	children, err := s.GetCAByParent(caID)
	if err != nil {
		return fmt.Errorf("failed to check CA children: %w", err)
	}

	if len(children) > 0 {
		return fmt.Errorf("cannot delete CA with children: %d intermediate CAs depend on this CA", len(children))
	}

	// Delete from database
	if err := s.caRepo.Delete(caID); err != nil {
		return fmt.Errorf("failed to delete CA from database: %w", err)
	}

	// Clean up files
	s.cleanupFiles(ca.FileID, ca.PrivateKeyID)

	return nil
}

// RevokeCA revokes a certificate authority (marks as revoked but keeps in database)
func (s *CertificateAuthorityService) RevokeCA(caID string, reason string) error {
	ca, err := s.caRepo.GetByID(caID)
	if err != nil {
		return fmt.Errorf("CA not found: %w", err)
	}

	// Update CA with revocation information
	ca.Description = fmt.Sprintf("%s [REVOKED: %s]", ca.Description, reason)

	if err := s.caRepo.Update(ca); err != nil {
		return fmt.Errorf("failed to revoke CA: %w", err)
	}

	return nil
}

// ValidateCAChain validates the certificate chain for a CA
func (s *CertificateAuthorityService) ValidateCAChain(caID string) error {
	ca, err := s.caRepo.GetByID(caID)
	if err != nil {
		return fmt.Errorf("CA not found: %w", err)
	}

	// Load CA certificate
	cert, _, err := s.loadCACertificateAndKey(&ca)
	if err != nil {
		return fmt.Errorf("failed to load CA certificate: %w", err)
	}

	// If it's a root CA, validate it's self-signed
	if ca.Root {
		if err := cert.CheckSignatureFrom(cert); err != nil {
			return fmt.Errorf("root CA certificate is not properly self-signed: %w", err)
		}
		return nil
	}

	// For intermediate CAs, validate the chain
	if ca.ParentID == nil {
		return fmt.Errorf("intermediate CA must have a parent")
	}

	parentCA, err := s.caRepo.GetByID(ca.ParentID.String())
	if err != nil {
		return fmt.Errorf("parent CA not found: %w", err)
	}

	parentCert, _, err := s.loadCACertificateAndKey(&parentCA)
	if err != nil {
		return fmt.Errorf("failed to load parent CA certificate: %w", err)
	}

	// Validate certificate chain
	if err := cert.CheckSignatureFrom(parentCert); err != nil {
		return fmt.Errorf("CA certificate is not properly signed by parent: %w", err)
	}

	// Check validity period
	now := time.Now()
	if now.Before(cert.NotBefore) {
		return fmt.Errorf("CA certificate is not yet valid")
	}
	if now.After(cert.NotAfter) {
		return fmt.Errorf("CA certificate has expired")
	}

	return nil
}

// Helper methods

// saveCertificate saves a certificate to a file and returns the file ID
func (s *CertificateAuthorityService) saveCertificate(cert *x509.Certificate, prefix string) (string, error) {
	// Create certificate directory if it doesn't exist
	if err := os.MkdirAll(s.certDir, 0755); err != nil {
		return "", fmt.Errorf("failed to create certificate directory: %w", err)
	}

	// Generate file ID
	fileID := fmt.Sprintf("%s-%s", prefix, uuid.New().String())

	// Export certificate to PEM
	exporter := utils.NewCertificateExporter()
	certPEM, err := exporter.ExportCertificateToPEM(cert)
	if err != nil {
		return "", fmt.Errorf("failed to export certificate to PEM: %w", err)
	}

	// Save to file
	certPath := filepath.Join(s.certDir, fmt.Sprintf("%s.crt", fileID))
	if err := os.WriteFile(certPath, certPEM, 0644); err != nil {
		return "", fmt.Errorf("failed to write certificate file: %w", err)
	}

	return fileID, nil
}

// savePrivateKey saves a private key to a file and returns the file ID
func (s *CertificateAuthorityService) savePrivateKey(privateKey interface{}, prefix string) (string, error) {
	// Create private key directory if it doesn't exist
	if err := os.MkdirAll(s.privateDir, 0700); err != nil {
		return "", fmt.Errorf("failed to create private key directory: %w", err)
	}

	// Generate file ID
	fileID := fmt.Sprintf("%s-%s", prefix, uuid.New().String())

	// Export private key to PEM
	exporter := utils.NewCertificateExporter()
	keyPEM, err := exporter.ExportPrivateKeyToPEM(privateKey)
	if err != nil {
		return "", fmt.Errorf("failed to export private key to PEM: %w", err)
	}

	// Save to file
	keyPath := filepath.Join(s.privateDir, fmt.Sprintf("%s.key", fileID))
	if err := os.WriteFile(keyPath, keyPEM, 0600); err != nil {
		return "", fmt.Errorf("failed to write private key file: %w", err)
	}

	return fileID, nil
}

// loadCACertificateAndKey loads a CA certificate and private key from files
func (s *CertificateAuthorityService) loadCACertificateAndKey(ca *models.CertificateAuthority) (*x509.Certificate, interface{}, error) {
	// Load certificate
	certPath := filepath.Join(s.certDir, fmt.Sprintf("%s.crt", ca.FileID))
	certPEM, err := os.ReadFile(certPath)
	if err != nil {
		return nil, nil, fmt.Errorf("failed to read certificate file: %w", err)
	}

	block, _ := pem.Decode(certPEM)
	if block == nil {
		return nil, nil, fmt.Errorf("failed to decode certificate PEM")
	}

	cert, err := x509.ParseCertificate(block.Bytes)
	if err != nil {
		return nil, nil, fmt.Errorf("failed to parse certificate: %w", err)
	}

	// Load private key
	keyPath := filepath.Join(s.privateDir, fmt.Sprintf("%s.key", ca.PrivateKeyID))
	keyPEM, err := os.ReadFile(keyPath)
	if err != nil {
		return nil, nil, fmt.Errorf("failed to read private key file: %w", err)
	}

	block, _ = pem.Decode(keyPEM)
	if block == nil {
		return nil, nil, fmt.Errorf("failed to decode private key PEM")
	}

	var privateKey interface{}
	switch block.Type {
	case "RSA PRIVATE KEY":
		privateKey, err = x509.ParsePKCS1PrivateKey(block.Bytes)
	case "EC PRIVATE KEY":
		privateKey, err = x509.ParseECPrivateKey(block.Bytes)
	default:
		return nil, nil, fmt.Errorf("unsupported private key type: %s", block.Type)
	}

	if err != nil {
		return nil, nil, fmt.Errorf("failed to parse private key: %w", err)
	}

	return cert, privateKey, nil
}

// cleanupFiles removes certificate and private key files
func (s *CertificateAuthorityService) cleanupFiles(certFileID, privateKeyFileID string) {
	if certFileID != "" {
		certPath := filepath.Join(s.certDir, fmt.Sprintf("%s.crt", certFileID))
		os.Remove(certPath)
	}

	if privateKeyFileID != "" {
		keyPath := filepath.Join(s.privateDir, fmt.Sprintf("%s.key", privateKeyFileID))
		os.Remove(keyPath)
	}
}

// validateRootCARequest validates a root CA creation request
func (s *CertificateAuthorityService) validateRootCARequest(req *CreateRootCARequest) error {
	if req.Name == "" {
		return fmt.Errorf("name is required")
	}
	if req.CommonName == "" {
		return fmt.Errorf("common name is required")
	}
	if req.Organization == "" {
		return fmt.Errorf("organization is required")
	}
	if req.Country == "" {
		return fmt.Errorf("country is required")
	}
	if req.OrganizationID == uuid.Nil {
		return fmt.Errorf("organization ID is required")
	}
	return nil
}

// validateIntermediateCARequest validates an intermediate CA creation request
func (s *CertificateAuthorityService) validateIntermediateCARequest(req *CreateIntermediateCARequest) error {
	if req.Name == "" {
		return fmt.Errorf("name is required")
	}
	if req.CommonName == "" {
		return fmt.Errorf("common name is required")
	}
	if req.Organization == "" {
		return fmt.Errorf("organization is required")
	}
	if req.Country == "" {
		return fmt.Errorf("country is required")
	}
	if req.OrganizationID == uuid.Nil {
		return fmt.Errorf("organization ID is required")
	}
	if req.ParentCAID == uuid.Nil {
		return fmt.Errorf("parent CA ID is required")
	}
	return nil
}

// Request structures

// CreateRootCARequest represents a request to create a root CA
type CreateRootCARequest struct {
	Name               string
	Description        string
	CommonName         string
	Organization       string
	OrganizationalUnit string
	Country            string
	State              string
	Locality           string
	Street             string
	Address            string
	PostalCode         string
	Email              string
	OrganizationID     uuid.UUID
	ValidityYears      int // Custom validity period in years (0 = use default)
}

// CreateIntermediateCARequest represents a request to create an intermediate CA
type CreateIntermediateCARequest struct {
	Name               string
	Description        string
	CommonName         string
	Organization       string
	OrganizationalUnit string
	Country            string
	State              string
	Locality           string
	Street             string
	Address            string
	PostalCode         string
	Email              string
	OrganizationID     uuid.UUID
	ParentCAID         uuid.UUID
	ValidityYears      int // Custom validity period in years (0 = use default)
}