// Package ca implements the CA (PKI) engine for X.509 certificate issuance.
package ca

import (
	"context"
	"crypto"
	"crypto/ecdsa"
	"crypto/ed25519"
	"crypto/rsa"
	"crypto/x509"
	"encoding/json"
	"encoding/pem"
	"errors"
	"fmt"
	"net"
	"strings"
	"sync"
	"time"

	"git.wntrmute.dev/kyle/goutils/certlib/certgen"

	"git.wntrmute.dev/kyle/metacrypt/internal/barrier"
	"git.wntrmute.dev/kyle/metacrypt/internal/engine"
)

var (
	ErrSealed         = errors.New("ca: engine is sealed")
	ErrIssuerNotFound = errors.New("ca: issuer not found")
	ErrIssuerExists   = errors.New("ca: issuer already exists")
	ErrCertNotFound   = errors.New("ca: certificate not found")
	ErrUnknownProfile = errors.New("ca: unknown profile")
	ErrForbidden      = errors.New("ca: forbidden")
	ErrUnauthorized   = errors.New("ca: authentication required")
)

// issuerState holds in-memory state for a loaded issuer.
type issuerState struct {
	cert   *x509.Certificate
	key    crypto.PrivateKey
	config *IssuerConfig
}

// CAEngine implements the CA (PKI) engine.
type CAEngine struct {
	mu        sync.RWMutex
	barrier   barrier.Barrier
	mountPath string
	config    *CAConfig
	rootCert  *x509.Certificate
	rootKey   crypto.PrivateKey
	issuers   map[string]*issuerState
}

// NewCAEngine creates a new CA engine instance.
func NewCAEngine() engine.Engine {
	return &CAEngine{
		issuers: make(map[string]*issuerState),
	}
}

func (e *CAEngine) Type() engine.EngineType {
	return engine.EngineTypeCA
}

// Initialize sets up the CA engine for first use: generates a self-signed root CA.
func (e *CAEngine) Initialize(ctx context.Context, b barrier.Barrier, mountPath string, config map[string]interface{}) error {
	e.mu.Lock()
	defer e.mu.Unlock()

	e.barrier = b
	e.mountPath = mountPath

	cfg := defaultCAConfig()
	if config != nil {
		if err := mapToCAConfig(config, cfg); err != nil {
			return fmt.Errorf("ca: parse config: %w", err)
		}
	}
	e.config = cfg

	// Store config.
	configData, err := json.Marshal(cfg)
	if err != nil {
		return fmt.Errorf("ca: marshal config: %w", err)
	}
	if err := b.Put(ctx, mountPath+"config.json", configData); err != nil {
		return fmt.Errorf("ca: store config: %w", err)
	}

	var rootCert *x509.Certificate
	var rootKey crypto.PrivateKey
	var certPEM, keyPEM []byte

	// If root_cert_pem and root_key_pem are provided, import them
	// instead of generating a new root CA.
	rootCertStr, _ := config["root_cert_pem"].(string)
	rootKeyStr, _ := config["root_key_pem"].(string)

	if rootCertStr != "" && rootKeyStr != "" {
		certPEM = []byte(rootCertStr)
		keyPEM = []byte(rootKeyStr)

		var err error
		rootCert, err = parseCertPEM(certPEM)
		if err != nil {
			return fmt.Errorf("ca: parse imported root cert: %w", err)
		}
		if !rootCert.IsCA {
			return fmt.Errorf("ca: imported certificate is not a CA")
		}
		rootKey, err = parsePrivateKeyPEM(keyPEM)
		if err != nil {
			return fmt.Errorf("ca: parse imported root key: %w", err)
		}
	} else {
		// Generate self-signed root CA.
		creq := &certgen.CertificateRequest{
			KeySpec: certgen.KeySpec{
				Algorithm: cfg.KeyAlgorithm,
				Size:      cfg.KeySize,
			},
			Subject: certgen.Subject{
				CommonName:   cfg.Organization + " Root CA",
				Organization: cfg.Organization,
				Country:      cfg.Country,
			},
			Profile: certgen.Profile{
				IsCA:    true,
				PathLen: 1,
				KeyUse:  []string{"cert sign", "crl sign"},
				Expiry:  cfg.RootExpiry,
			},
		}

		var err error
		rootCert, rootKey, err = certgen.GenerateSelfSigned(creq)
		if err != nil {
			return fmt.Errorf("ca: generate root CA: %w", err)
		}

		certPEM = pem.EncodeToMemory(&pem.Block{Type: "CERTIFICATE", Bytes: rootCert.Raw})
		keyPEM, err = marshalPrivateKey(rootKey)
		if err != nil {
			return fmt.Errorf("ca: marshal root key: %w", err)
		}
	}

	if err := b.Put(ctx, mountPath+"root/cert.pem", certPEM); err != nil {
		return fmt.Errorf("ca: store root cert: %w", err)
	}
	if err := b.Put(ctx, mountPath+"root/key.pem", keyPEM); err != nil {
		return fmt.Errorf("ca: store root key: %w", err)
	}

	e.rootCert = rootCert
	e.rootKey = rootKey

	return nil
}

// Unseal loads the CA state from the barrier into memory.
func (e *CAEngine) Unseal(ctx context.Context, b barrier.Barrier, mountPath string) error {
	e.mu.Lock()
	defer e.mu.Unlock()

	e.barrier = b
	e.mountPath = mountPath

	// Load config.
	configData, err := b.Get(ctx, mountPath+"config.json")
	if err != nil {
		return fmt.Errorf("ca: load config: %w", err)
	}
	var cfg CAConfig
	if err := json.Unmarshal(configData, &cfg); err != nil {
		return fmt.Errorf("ca: parse config: %w", err)
	}
	e.config = &cfg

	// Load root cert and key.
	certPEM, err := b.Get(ctx, mountPath+"root/cert.pem")
	if err != nil {
		return fmt.Errorf("ca: load root cert: %w", err)
	}
	keyPEM, err := b.Get(ctx, mountPath+"root/key.pem")
	if err != nil {
		return fmt.Errorf("ca: load root key: %w", err)
	}

	rootCert, err := parseCertPEM(certPEM)
	if err != nil {
		return fmt.Errorf("ca: parse root cert: %w", err)
	}
	rootKey, err := parsePrivateKeyPEM(keyPEM)
	if err != nil {
		return fmt.Errorf("ca: parse root key: %w", err)
	}

	e.rootCert = rootCert
	e.rootKey = rootKey
	e.issuers = make(map[string]*issuerState)

	// Load all issuers.
	issuerPaths, err := b.List(ctx, mountPath+"issuers/")
	if err != nil {
		return fmt.Errorf("ca: list issuers: %w", err)
	}

	// Collect unique issuer names from paths like "name/cert.pem", "name/key.pem", "name/config.json".
	issuerNames := make(map[string]bool)
	for _, p := range issuerPaths {
		parts := strings.SplitN(p, "/", 2)
		if len(parts) > 0 && parts[0] != "" {
			issuerNames[parts[0]] = true
		}
	}

	for name := range issuerNames {
		is, err := e.loadIssuer(ctx, b, mountPath, name)
		if err != nil {
			return fmt.Errorf("ca: load issuer %q: %w", name, err)
		}
		e.issuers[name] = is
	}

	return nil
}

func (e *CAEngine) loadIssuer(ctx context.Context, b barrier.Barrier, mountPath, name string) (*issuerState, error) {
	prefix := mountPath + "issuers/" + name + "/"

	certPEM, err := b.Get(ctx, prefix+"cert.pem")
	if err != nil {
		return nil, fmt.Errorf("load cert: %w", err)
	}
	keyPEM, err := b.Get(ctx, prefix+"key.pem")
	if err != nil {
		return nil, fmt.Errorf("load key: %w", err)
	}
	configData, err := b.Get(ctx, prefix+"config.json")
	if err != nil {
		return nil, fmt.Errorf("load config: %w", err)
	}

	cert, err := parseCertPEM(certPEM)
	if err != nil {
		return nil, fmt.Errorf("parse cert: %w", err)
	}
	key, err := parsePrivateKeyPEM(keyPEM)
	if err != nil {
		return nil, fmt.Errorf("parse key: %w", err)
	}
	var cfg IssuerConfig
	if err := json.Unmarshal(configData, &cfg); err != nil {
		return nil, fmt.Errorf("parse config: %w", err)
	}

	return &issuerState{cert: cert, key: key, config: &cfg}, nil
}

// Seal zeroizes all in-memory key material.
func (e *CAEngine) Seal() error {
	e.mu.Lock()
	defer e.mu.Unlock()

	zeroizeKey(e.rootKey)
	e.rootKey = nil
	e.rootCert = nil
	e.config = nil

	for name, is := range e.issuers {
		zeroizeKey(is.key)
		delete(e.issuers, name)
	}
	e.issuers = nil

	return nil
}

// HandleRequest dispatches CA operations.
func (e *CAEngine) HandleRequest(ctx context.Context, req *engine.Request) (*engine.Response, error) {
	switch req.Operation {
	case "get-root":
		return e.handleGetRoot(ctx)
	case "get-chain":
		return e.handleGetChain(ctx, req)
	case "get-issuer":
		return e.handleGetIssuer(ctx, req)
	case "create-issuer":
		return e.handleCreateIssuer(ctx, req)
	case "delete-issuer":
		return e.handleDeleteIssuer(ctx, req)
	case "list-issuers":
		return e.handleListIssuers(ctx, req)
	case "issue":
		return e.handleIssue(ctx, req)
	case "get-cert":
		return e.handleGetCert(ctx, req)
	case "list-certs":
		return e.handleListCerts(ctx, req)
	case "renew":
		return e.handleRenew(ctx, req)
	case "import-root":
		return e.handleImportRoot(ctx, req)
	default:
		return nil, fmt.Errorf("ca: unknown operation: %s", req.Operation)
	}
}

// --- Public methods for unauthenticated PKI routes ---

// GetRootCertPEM returns the root CA certificate in PEM format.
func (e *CAEngine) GetRootCertPEM() ([]byte, error) {
	e.mu.RLock()
	defer e.mu.RUnlock()

	if e.rootCert == nil {
		return nil, ErrSealed
	}
	return pem.EncodeToMemory(&pem.Block{Type: "CERTIFICATE", Bytes: e.rootCert.Raw}), nil
}

// GetIssuerCertPEM returns the named issuer's certificate in PEM format.
func (e *CAEngine) GetIssuerCertPEM(name string) ([]byte, error) {
	e.mu.RLock()
	defer e.mu.RUnlock()

	if e.rootCert == nil {
		return nil, ErrSealed
	}
	is, ok := e.issuers[name]
	if !ok {
		return nil, ErrIssuerNotFound
	}
	return pem.EncodeToMemory(&pem.Block{Type: "CERTIFICATE", Bytes: is.cert.Raw}), nil
}

// GetChainPEM returns the full certificate chain (issuer + root) in PEM format.
func (e *CAEngine) GetChainPEM(issuerName string) ([]byte, error) {
	e.mu.RLock()
	defer e.mu.RUnlock()

	if e.rootCert == nil {
		return nil, ErrSealed
	}
	is, ok := e.issuers[issuerName]
	if !ok {
		return nil, ErrIssuerNotFound
	}

	var chain []byte
	chain = append(chain, pem.EncodeToMemory(&pem.Block{Type: "CERTIFICATE", Bytes: is.cert.Raw})...)
	chain = append(chain, pem.EncodeToMemory(&pem.Block{Type: "CERTIFICATE", Bytes: e.rootCert.Raw})...)
	return chain, nil
}

// --- Operation handlers ---

func (e *CAEngine) handleImportRoot(ctx context.Context, req *engine.Request) (*engine.Response, error) {
	if req.CallerInfo == nil {
		return nil, ErrUnauthorized
	}
	if !req.CallerInfo.IsAdmin {
		return nil, ErrForbidden
	}

	certStr, _ := req.Data["cert_pem"].(string)
	keyStr, _ := req.Data["key_pem"].(string)
	if certStr == "" || keyStr == "" {
		return nil, fmt.Errorf("ca: cert_pem and key_pem are required")
	}

	newCert, err := parseCertPEM([]byte(certStr))
	if err != nil {
		return nil, fmt.Errorf("ca: parse imported cert: %w", err)
	}
	if !newCert.IsCA {
		return nil, fmt.Errorf("ca: imported certificate is not a CA")
	}

	newKey, err := parsePrivateKeyPEM([]byte(keyStr))
	if err != nil {
		return nil, fmt.Errorf("ca: parse imported key: %w", err)
	}

	e.mu.Lock()
	defer e.mu.Unlock()

	// Only allow import if there is no root or the current root is expired.
	if e.rootCert != nil && time.Now().Before(e.rootCert.NotAfter) {
		return nil, fmt.Errorf("ca: current root is still valid (expires %s); cannot replace", e.rootCert.NotAfter.Format(time.RFC3339))
	}

	// Zeroize old key if present.
	if e.rootKey != nil {
		zeroizeKey(e.rootKey)
	}

	// Store in barrier.
	certPEM := []byte(certStr)
	keyPEM := []byte(keyStr)
	if err := e.barrier.Put(ctx, e.mountPath+"root/cert.pem", certPEM); err != nil {
		return nil, fmt.Errorf("ca: store root cert: %w", err)
	}
	if err := e.barrier.Put(ctx, e.mountPath+"root/key.pem", keyPEM); err != nil {
		return nil, fmt.Errorf("ca: store root key: %w", err)
	}

	e.rootCert = newCert
	e.rootKey = newKey

	return &engine.Response{
		Data: map[string]interface{}{
			"cn":         newCert.Subject.CommonName,
			"expires_at": newCert.NotAfter,
		},
	}, nil
}

func (e *CAEngine) handleGetRoot(_ context.Context) (*engine.Response, error) {
	e.mu.RLock()
	defer e.mu.RUnlock()

	if e.rootCert == nil {
		return nil, ErrSealed
	}

	certPEM := pem.EncodeToMemory(&pem.Block{Type: "CERTIFICATE", Bytes: e.rootCert.Raw})
	return &engine.Response{
		Data: map[string]interface{}{
			"cert_pem": string(certPEM),
		},
	}, nil
}

func (e *CAEngine) handleGetChain(_ context.Context, req *engine.Request) (*engine.Response, error) {
	issuerName, _ := req.Data["issuer"].(string)
	if issuerName == "" {
		issuerName = req.Path
	}

	chain, err := e.GetChainPEM(issuerName)
	if err != nil {
		return nil, err
	}
	return &engine.Response{
		Data: map[string]interface{}{
			"chain_pem": string(chain),
		},
	}, nil
}

func (e *CAEngine) handleGetIssuer(_ context.Context, req *engine.Request) (*engine.Response, error) {
	name := req.Path

	certPEM, err := e.GetIssuerCertPEM(name)
	if err != nil {
		return nil, err
	}
	return &engine.Response{
		Data: map[string]interface{}{
			"cert_pem": string(certPEM),
		},
	}, nil
}

func (e *CAEngine) handleCreateIssuer(ctx context.Context, req *engine.Request) (*engine.Response, error) {
	if req.CallerInfo == nil {
		return nil, ErrUnauthorized
	}
	if !req.CallerInfo.IsAdmin {
		return nil, ErrForbidden
	}

	name, _ := req.Data["name"].(string)
	if name == "" {
		return nil, fmt.Errorf("ca: issuer name is required")
	}

	e.mu.Lock()
	defer e.mu.Unlock()

	if e.rootCert == nil {
		return nil, ErrSealed
	}

	if _, exists := e.issuers[name]; exists {
		return nil, ErrIssuerExists
	}

	// Determine key spec: use issuer-specific overrides or fall back to CA config.
	keyAlg := e.config.KeyAlgorithm
	keySize := e.config.KeySize
	if v, ok := req.Data["key_algorithm"].(string); ok && v != "" {
		keyAlg = v
	}
	if v, ok := req.Data["key_size"].(float64); ok {
		keySize = int(v)
	}

	expiry := "43800h" // 5 years default
	if v, ok := req.Data["expiry"].(string); ok && v != "" {
		expiry = v
	}

	maxTTL := "2160h" // 90 days default
	if v, ok := req.Data["max_ttl"].(string); ok && v != "" {
		maxTTL = v
	}

	// Generate issuer key pair and CSR.
	ks := certgen.KeySpec{Algorithm: keyAlg, Size: keySize}
	_, priv, err := ks.Generate()
	if err != nil {
		return nil, fmt.Errorf("ca: generate issuer key: %w", err)
	}

	creq := certgen.CertificateRequest{
		KeySpec: ks,
		Subject: certgen.Subject{
			CommonName:   name,
			Organization: e.config.Organization,
			Country:      e.config.Country,
		},
	}

	csr, err := creq.Request(priv)
	if err != nil {
		return nil, fmt.Errorf("ca: create issuer CSR: %w", err)
	}

	// Sign with root CA using an intermediate CA profile.
	profile := certgen.Profile{
		IsCA:    true,
		PathLen: 0,
		KeyUse:  []string{"cert sign", "crl sign"},
		Expiry:  expiry,
	}

	issuerCert, err := profile.SignRequest(e.rootCert, csr, e.rootKey)
	if err != nil {
		return nil, fmt.Errorf("ca: sign issuer cert: %w", err)
	}

	// Store in barrier.
	prefix := e.mountPath + "issuers/" + name + "/"
	certPEM := pem.EncodeToMemory(&pem.Block{Type: "CERTIFICATE", Bytes: issuerCert.Raw})
	keyPEM, err := marshalPrivateKey(priv)
	if err != nil {
		return nil, fmt.Errorf("ca: marshal issuer key: %w", err)
	}

	issuerCfg := &IssuerConfig{
		Name:         name,
		KeyAlgorithm: keyAlg,
		KeySize:      keySize,
		Expiry:       expiry,
		MaxTTL:       maxTTL,
		CreatedBy:    req.CallerInfo.Username,
		CreatedAt:    time.Now(),
	}
	cfgData, err := json.Marshal(issuerCfg)
	if err != nil {
		return nil, fmt.Errorf("ca: marshal issuer config: %w", err)
	}

	if err := e.barrier.Put(ctx, prefix+"cert.pem", certPEM); err != nil {
		return nil, fmt.Errorf("ca: store issuer cert: %w", err)
	}
	if err := e.barrier.Put(ctx, prefix+"key.pem", keyPEM); err != nil {
		return nil, fmt.Errorf("ca: store issuer key: %w", err)
	}
	if err := e.barrier.Put(ctx, prefix+"config.json", cfgData); err != nil {
		return nil, fmt.Errorf("ca: store issuer config: %w", err)
	}

	e.issuers[name] = &issuerState{cert: issuerCert, key: priv, config: issuerCfg}

	return &engine.Response{
		Data: map[string]interface{}{
			"name":     name,
			"cert_pem": string(certPEM),
		},
	}, nil
}

func (e *CAEngine) handleDeleteIssuer(ctx context.Context, req *engine.Request) (*engine.Response, error) {
	if req.CallerInfo == nil {
		return nil, ErrUnauthorized
	}
	if !req.CallerInfo.IsAdmin {
		return nil, ErrForbidden
	}

	name, _ := req.Data["name"].(string)
	if name == "" {
		name = req.Path
	}

	e.mu.Lock()
	defer e.mu.Unlock()

	if e.rootCert == nil {
		return nil, ErrSealed
	}

	is, exists := e.issuers[name]
	if !exists {
		return nil, ErrIssuerNotFound
	}

	// Zeroize key material.
	zeroizeKey(is.key)

	// Delete from barrier.
	prefix := e.mountPath + "issuers/" + name + "/"
	for _, suffix := range []string{"cert.pem", "key.pem", "config.json"} {
		if err := e.barrier.Delete(ctx, prefix+suffix); err != nil {
			return nil, fmt.Errorf("ca: delete issuer %s: %w", suffix, err)
		}
	}

	delete(e.issuers, name)

	return &engine.Response{
		Data: map[string]interface{}{"ok": true},
	}, nil
}

func (e *CAEngine) handleListIssuers(_ context.Context, req *engine.Request) (*engine.Response, error) {
	if req.CallerInfo == nil {
		return nil, ErrUnauthorized
	}

	e.mu.RLock()
	defer e.mu.RUnlock()

	if e.rootCert == nil {
		return nil, ErrSealed
	}

	names := make([]string, 0, len(e.issuers))
	for name := range e.issuers {
		names = append(names, name)
	}

	return &engine.Response{
		Data: map[string]interface{}{
			"issuers": names,
		},
	}, nil
}

func (e *CAEngine) handleIssue(ctx context.Context, req *engine.Request) (*engine.Response, error) {
	if req.CallerInfo == nil {
		return nil, ErrUnauthorized
	}

	issuerName, _ := req.Data["issuer"].(string)
	if issuerName == "" {
		issuerName = req.Path
	}
	if issuerName == "" {
		return nil, fmt.Errorf("ca: issuer name is required")
	}

	profileName, _ := req.Data["profile"].(string)
	if profileName == "" {
		profileName = "server"
	}

	cn, _ := req.Data["common_name"].(string)
	if cn == "" {
		return nil, fmt.Errorf("ca: common_name is required")
	}

	e.mu.Lock()
	defer e.mu.Unlock()

	if e.rootCert == nil {
		return nil, ErrSealed
	}

	is, ok := e.issuers[issuerName]
	if !ok {
		return nil, ErrIssuerNotFound
	}

	profile, ok := GetProfile(profileName)
	if !ok {
		return nil, fmt.Errorf("%w: %s", ErrUnknownProfile, profileName)
	}

	// Apply user overrides.
	if v, ok := req.Data["ttl"].(string); ok && v != "" {
		profile.Expiry = v
	}
	if v, ok := req.Data["key_usages"].([]interface{}); ok {
		profile.KeyUse = toStringSlice(v)
	}
	if v, ok := req.Data["ext_key_usages"].([]interface{}); ok {
		profile.ExtKeyUsages = toStringSlice(v)
	}

	// Determine leaf key spec.
	keyAlg := is.config.KeyAlgorithm
	keySize := is.config.KeySize
	if v, ok := req.Data["key_algorithm"].(string); ok && v != "" {
		keyAlg = v
	}
	if v, ok := req.Data["key_size"].(float64); ok {
		keySize = int(v)
	}

	// Parse SANs.
	var dnsNames []string
	var ipAddrs []string
	if v, ok := req.Data["dns_names"].([]interface{}); ok {
		dnsNames = toStringSlice(v)
	}
	if v, ok := req.Data["ip_addresses"].([]interface{}); ok {
		ipAddrs = toStringSlice(v)
	}

	// Generate leaf key pair and CSR.
	ks := certgen.KeySpec{Algorithm: keyAlg, Size: keySize}
	_, leafKey, err := ks.Generate()
	if err != nil {
		return nil, fmt.Errorf("ca: generate leaf key: %w", err)
	}

	creq := certgen.CertificateRequest{
		KeySpec: ks,
		Subject: certgen.Subject{
			CommonName:   cn,
			Organization: e.config.Organization,
			DNSNames:     dnsNames,
			IPAddresses:  ipAddrs,
		},
	}

	csr, err := creq.Request(leafKey)
	if err != nil {
		return nil, fmt.Errorf("ca: create leaf CSR: %w", err)
	}

	leafCert, err := profile.SignRequest(is.cert, csr, is.key)
	if err != nil {
		return nil, fmt.Errorf("ca: sign leaf cert: %w", err)
	}

	// Build PEM outputs.
	leafCertPEM := pem.EncodeToMemory(&pem.Block{Type: "CERTIFICATE", Bytes: leafCert.Raw})
	leafKeyPEM, err := marshalPrivateKey(leafKey)
	if err != nil {
		return nil, fmt.Errorf("ca: marshal leaf key: %w", err)
	}

	var chainPEM []byte
	chainPEM = append(chainPEM, leafCertPEM...)
	chainPEM = append(chainPEM, pem.EncodeToMemory(&pem.Block{Type: "CERTIFICATE", Bytes: is.cert.Raw})...)
	chainPEM = append(chainPEM, pem.EncodeToMemory(&pem.Block{Type: "CERTIFICATE", Bytes: e.rootCert.Raw})...)

	serial := fmt.Sprintf("%x", leafCert.SerialNumber)

	// Collect all SANs for the record.
	allSANs := append(leafCert.DNSNames, ipStrings(leafCert.IPAddresses)...)

	// Store cert record (NO private key).
	record := &CertRecord{
		Serial:    serial,
		Issuer:    issuerName,
		CN:        cn,
		SANs:      allSANs,
		Profile:   profileName,
		CertPEM:   string(leafCertPEM),
		IssuedBy:  req.CallerInfo.Username,
		IssuedAt:  time.Now(),
		ExpiresAt: leafCert.NotAfter,
	}
	recordData, err := json.Marshal(record)
	if err != nil {
		return nil, fmt.Errorf("ca: marshal cert record: %w", err)
	}
	if err := e.barrier.Put(ctx, e.mountPath+"certs/"+serial+".json", recordData); err != nil {
		return nil, fmt.Errorf("ca: store cert record: %w", err)
	}

	return &engine.Response{
		Data: map[string]interface{}{
			"serial":    serial,
			"cert_pem":  string(leafCertPEM),
			"key_pem":   string(leafKeyPEM),
			"chain_pem": string(chainPEM),
			"cn":        cn,
			"sans":      allSANs,
			"issued_by": req.CallerInfo.Username,
			"expires_at": leafCert.NotAfter,
		},
	}, nil
}

func (e *CAEngine) handleGetCert(ctx context.Context, req *engine.Request) (*engine.Response, error) {
	if req.CallerInfo == nil {
		return nil, ErrUnauthorized
	}

	serial, _ := req.Data["serial"].(string)
	if serial == "" {
		serial = req.Path
	}
	if serial == "" {
		return nil, fmt.Errorf("ca: serial is required")
	}

	e.mu.RLock()
	defer e.mu.RUnlock()

	recordData, err := e.barrier.Get(ctx, e.mountPath+"certs/"+serial+".json")
	if err != nil {
		if errors.Is(err, barrier.ErrNotFound) {
			return nil, ErrCertNotFound
		}
		return nil, fmt.Errorf("ca: load cert record: %w", err)
	}

	var record CertRecord
	if err := json.Unmarshal(recordData, &record); err != nil {
		return nil, fmt.Errorf("ca: parse cert record: %w", err)
	}

	return &engine.Response{
		Data: map[string]interface{}{
			"serial":     record.Serial,
			"issuer":     record.Issuer,
			"cn":         record.CN,
			"sans":       record.SANs,
			"profile":    record.Profile,
			"cert_pem":   record.CertPEM,
			"issued_by":  record.IssuedBy,
			"issued_at":  record.IssuedAt,
			"expires_at": record.ExpiresAt,
		},
	}, nil
}

func (e *CAEngine) handleListCerts(ctx context.Context, req *engine.Request) (*engine.Response, error) {
	if req.CallerInfo == nil {
		return nil, ErrUnauthorized
	}

	e.mu.RLock()
	defer e.mu.RUnlock()

	paths, err := e.barrier.List(ctx, e.mountPath+"certs/")
	if err != nil {
		return nil, fmt.Errorf("ca: list certs: %w", err)
	}

	var certs []map[string]interface{}
	for _, p := range paths {
		if !strings.HasSuffix(p, ".json") {
			continue
		}
		recordData, err := e.barrier.Get(ctx, e.mountPath+"certs/"+p)
		if err != nil {
			continue
		}
		var record CertRecord
		if err := json.Unmarshal(recordData, &record); err != nil {
			continue
		}
		certs = append(certs, map[string]interface{}{
			"serial":     record.Serial,
			"issuer":     record.Issuer,
			"cn":         record.CN,
			"profile":    record.Profile,
			"issued_by":  record.IssuedBy,
			"issued_at":  record.IssuedAt,
			"expires_at": record.ExpiresAt,
		})
	}

	return &engine.Response{
		Data: map[string]interface{}{
			"certs": certs,
		},
	}, nil
}

func (e *CAEngine) handleRenew(ctx context.Context, req *engine.Request) (*engine.Response, error) {
	if req.CallerInfo == nil {
		return nil, ErrUnauthorized
	}

	serial, _ := req.Data["serial"].(string)
	if serial == "" {
		serial = req.Path
	}
	if serial == "" {
		return nil, fmt.Errorf("ca: serial is required")
	}

	e.mu.Lock()
	defer e.mu.Unlock()

	if e.rootCert == nil {
		return nil, ErrSealed
	}

	// Load original cert record.
	recordData, err := e.barrier.Get(ctx, e.mountPath+"certs/"+serial+".json")
	if err != nil {
		if errors.Is(err, barrier.ErrNotFound) {
			return nil, ErrCertNotFound
		}
		return nil, fmt.Errorf("ca: load cert record: %w", err)
	}

	var record CertRecord
	if err := json.Unmarshal(recordData, &record); err != nil {
		return nil, fmt.Errorf("ca: parse cert record: %w", err)
	}

	// Look up issuer.
	is, ok := e.issuers[record.Issuer]
	if !ok {
		return nil, fmt.Errorf("ca: original issuer %q no longer exists", record.Issuer)
	}

	// Parse original cert to extract attributes.
	origCert, err := parseCertPEM([]byte(record.CertPEM))
	if err != nil {
		return nil, fmt.Errorf("ca: parse original cert: %w", err)
	}

	// Build profile from original cert's usages.
	profile, _ := GetProfile(record.Profile)
	// Use original TTL duration.
	origDuration := origCert.NotAfter.Sub(origCert.NotBefore)
	profile.Expiry = fmt.Sprintf("%dh", int(origDuration.Hours()))

	// Generate new key.
	ks := certgen.KeySpec{Algorithm: is.config.KeyAlgorithm, Size: is.config.KeySize}
	_, newKey, err := ks.Generate()
	if err != nil {
		return nil, fmt.Errorf("ca: generate renewal key: %w", err)
	}

	creq := certgen.CertificateRequest{
		KeySpec: ks,
		Subject: certgen.Subject{
			CommonName:   origCert.Subject.CommonName,
			Organization: firstOrEmpty(origCert.Subject.Organization),
			DNSNames:     origCert.DNSNames,
			IPAddresses:  ipStrings(origCert.IPAddresses),
		},
	}

	csr, err := creq.Request(newKey)
	if err != nil {
		return nil, fmt.Errorf("ca: create renewal CSR: %w", err)
	}

	newCert, err := profile.SignRequest(is.cert, csr, is.key)
	if err != nil {
		return nil, fmt.Errorf("ca: sign renewal cert: %w", err)
	}

	// Build PEMs.
	newCertPEM := pem.EncodeToMemory(&pem.Block{Type: "CERTIFICATE", Bytes: newCert.Raw})
	newKeyPEM, err := marshalPrivateKey(newKey)
	if err != nil {
		return nil, fmt.Errorf("ca: marshal renewal key: %w", err)
	}

	var chainPEM []byte
	chainPEM = append(chainPEM, newCertPEM...)
	chainPEM = append(chainPEM, pem.EncodeToMemory(&pem.Block{Type: "CERTIFICATE", Bytes: is.cert.Raw})...)
	chainPEM = append(chainPEM, pem.EncodeToMemory(&pem.Block{Type: "CERTIFICATE", Bytes: e.rootCert.Raw})...)

	newSerial := fmt.Sprintf("%x", newCert.SerialNumber)

	allSANs := append(newCert.DNSNames, ipStrings(newCert.IPAddresses)...)

	newRecord := &CertRecord{
		Serial:    newSerial,
		Issuer:    record.Issuer,
		CN:        record.CN,
		SANs:      allSANs,
		Profile:   record.Profile,
		CertPEM:   string(newCertPEM),
		IssuedBy:  req.CallerInfo.Username,
		IssuedAt:  time.Now(),
		ExpiresAt: newCert.NotAfter,
	}
	newRecordData, err := json.Marshal(newRecord)
	if err != nil {
		return nil, fmt.Errorf("ca: marshal renewal record: %w", err)
	}
	if err := e.barrier.Put(ctx, e.mountPath+"certs/"+newSerial+".json", newRecordData); err != nil {
		return nil, fmt.Errorf("ca: store renewal record: %w", err)
	}

	return &engine.Response{
		Data: map[string]interface{}{
			"serial":     newSerial,
			"cert_pem":   string(newCertPEM),
			"key_pem":    string(newKeyPEM),
			"chain_pem":  string(chainPEM),
			"cn":         record.CN,
			"expires_at": newCert.NotAfter,
		},
	}, nil
}

// --- Helpers ---

func defaultCAConfig() *CAConfig {
	return &CAConfig{
		Organization: "Metacircular",
		KeyAlgorithm: "ecdsa",
		KeySize:      521,
		RootExpiry:   "87600h", // 10 years
	}
}

func mapToCAConfig(m map[string]interface{}, cfg *CAConfig) error {
	if v, ok := m["organization"].(string); ok {
		cfg.Organization = v
	}
	if v, ok := m["country"].(string); ok {
		cfg.Country = v
	}
	if v, ok := m["key_algorithm"].(string); ok {
		cfg.KeyAlgorithm = v
	}
	if v, ok := m["key_size"].(float64); ok {
		cfg.KeySize = int(v)
	}
	if v, ok := m["root_expiry"].(string); ok {
		cfg.RootExpiry = v
	}
	return nil
}

func marshalPrivateKey(key crypto.PrivateKey) ([]byte, error) {
	der, err := x509.MarshalPKCS8PrivateKey(key)
	if err != nil {
		return nil, err
	}
	return pem.EncodeToMemory(&pem.Block{Type: "PRIVATE KEY", Bytes: der}), nil
}

func parseCertPEM(data []byte) (*x509.Certificate, error) {
	block, _ := pem.Decode(data)
	if block == nil {
		return nil, fmt.Errorf("no PEM block found")
	}
	return x509.ParseCertificate(block.Bytes)
}

func parsePrivateKeyPEM(data []byte) (crypto.PrivateKey, error) {
	block, _ := pem.Decode(data)
	if block == nil {
		return nil, fmt.Errorf("no PEM block found")
	}
	return x509.ParsePKCS8PrivateKey(block.Bytes)
}

func zeroizeKey(key crypto.PrivateKey) {
	if key == nil {
		return
	}
	switch k := key.(type) {
	case *ecdsa.PrivateKey:
		k.D.SetInt64(0)
	case *rsa.PrivateKey:
		k.D.SetInt64(0)
		for _, p := range k.Primes {
			p.SetInt64(0)
		}
	case ed25519.PrivateKey:
		for i := range k {
			k[i] = 0
		}
	}
}

func toStringSlice(v []interface{}) []string {
	s := make([]string, 0, len(v))
	for _, item := range v {
		if str, ok := item.(string); ok {
			s = append(s, str)
		}
	}
	return s
}

func ipStrings(ips []net.IP) []string {
	s := make([]string, 0, len(ips))
	for _, ip := range ips {
		s = append(s, ip.String())
	}
	return s
}

func firstOrEmpty(s []string) string {
	if len(s) > 0 {
		return s[0]
	}
	return ""
}