package webserver

import (
	"context"
	"crypto/tls"
	"crypto/x509"
	"fmt"
	"log/slog"
	"os"

	"google.golang.org/grpc"
	"google.golang.org/grpc/credentials"
	"google.golang.org/grpc/metadata"

	pb "git.wntrmute.dev/kyle/metacrypt/gen/metacrypt/v2"
)

// VaultClient wraps the gRPC stubs for communicating with the vault.
type VaultClient struct {
	conn   *grpc.ClientConn
	system pb.SystemServiceClient
	auth   pb.AuthServiceClient
	engine pb.EngineServiceClient
	pki    pb.PKIServiceClient
	ca     pb.CAServiceClient
}

// NewVaultClient dials the vault gRPC server and returns a client.
func NewVaultClient(addr, caCertPath string, logger *slog.Logger) (*VaultClient, error) {
	logger.Debug("connecting to vault", "addr", addr, "ca_cert", caCertPath)

	tlsCfg := &tls.Config{MinVersion: tls.VersionTLS12}
	if caCertPath != "" {
		logger.Debug("loading vault CA certificate", "path", caCertPath)
		pemData, err := os.ReadFile(caCertPath) //nolint:gosec
		if err != nil {
			return nil, fmt.Errorf("webserver: read CA cert: %w", err)
		}
		pool := x509.NewCertPool()
		if !pool.AppendCertsFromPEM(pemData) {
			return nil, fmt.Errorf("webserver: parse CA cert")
		}
		tlsCfg.RootCAs = pool
		logger.Debug("vault CA certificate loaded successfully")
	} else {
		logger.Debug("no CA cert configured, using system roots")
	}

	logger.Debug("dialing vault gRPC", "addr", addr)
	conn, err := grpc.NewClient(addr, grpc.WithTransportCredentials(credentials.NewTLS(tlsCfg)))
	if err != nil {
		return nil, fmt.Errorf("webserver: dial vault: %w", err)
	}
	logger.Debug("vault gRPC connection established", "addr", addr)

	return &VaultClient{
		conn:   conn,
		system: pb.NewSystemServiceClient(conn),
		auth:   pb.NewAuthServiceClient(conn),
		engine: pb.NewEngineServiceClient(conn),
		pki:    pb.NewPKIServiceClient(conn),
		ca:     pb.NewCAServiceClient(conn),
	}, nil
}

// Close closes the underlying connection.
func (c *VaultClient) Close() error {
	return c.conn.Close()
}

// withToken returns a context with the Bearer token in outgoing metadata.
func withToken(ctx context.Context, token string) context.Context {
	return metadata.AppendToOutgoingContext(ctx, "authorization", "Bearer "+token)
}

// Status returns the current vault state string (e.g. "unsealed").
func (c *VaultClient) Status(ctx context.Context) (string, error) {
	resp, err := c.system.Status(ctx, &pb.StatusRequest{})
	if err != nil {
		return "", err
	}
	return resp.State, nil
}

// Init initializes the vault with the given password.
func (c *VaultClient) Init(ctx context.Context, password string) error {
	_, err := c.system.Init(ctx, &pb.InitRequest{Password: password})
	return err
}

// Unseal unseals the vault with the given password.
func (c *VaultClient) Unseal(ctx context.Context, password string) error {
	_, err := c.system.Unseal(ctx, &pb.UnsealRequest{Password: password})
	return err
}

// TokenInfo holds validated token details returned by the vault.
type TokenInfo struct {
	Username string
	Roles    []string
	IsAdmin  bool
}

// Login authenticates against the vault and returns the session token.
func (c *VaultClient) Login(ctx context.Context, username, password, totpCode string) (string, error) {
	resp, err := c.auth.Login(ctx, &pb.LoginRequest{
		Username: username,
		Password: password,
		TotpCode: totpCode,
	})
	if err != nil {
		return "", err
	}
	return resp.Token, nil
}

// ValidateToken validates a token against the vault and returns the token info.
func (c *VaultClient) ValidateToken(ctx context.Context, token string) (*TokenInfo, error) {
	resp, err := c.auth.TokenInfo(withToken(ctx, token), &pb.TokenInfoRequest{})
	if err != nil {
		return nil, err
	}
	return &TokenInfo{
		Username: resp.Username,
		Roles:    resp.Roles,
		IsAdmin:  resp.IsAdmin,
	}, nil
}

// MountInfo holds metadata about an engine mount.
type MountInfo struct {
	Name      string
	Type      string
	MountPath string
}

// ListMounts returns all engine mounts from the vault.
func (c *VaultClient) ListMounts(ctx context.Context, token string) ([]MountInfo, error) {
	resp, err := c.engine.ListMounts(withToken(ctx, token), &pb.ListMountsRequest{})
	if err != nil {
		return nil, err
	}
	mounts := make([]MountInfo, 0, len(resp.Mounts))
	for _, m := range resp.Mounts {
		mounts = append(mounts, MountInfo{
			Name:      m.Name,
			Type:      m.Type,
			MountPath: m.MountPath,
		})
	}
	return mounts, nil
}

// Mount creates a new engine mount on the vault.
func (c *VaultClient) Mount(ctx context.Context, token, name, engineType string, config map[string]interface{}) error {
	req := &pb.MountRequest{
		Name: name,
		Type: engineType,
	}
	if len(config) > 0 {
		cfg := make(map[string]string, len(config))
		for k, v := range config {
			cfg[k] = fmt.Sprintf("%v", v)
		}
		req.Config = cfg
	}
	_, err := c.engine.Mount(withToken(ctx, token), req)
	return err
}

// GetRootCert returns the root CA certificate PEM for the given mount.
func (c *VaultClient) GetRootCert(ctx context.Context, mount string) ([]byte, error) {
	resp, err := c.pki.GetRootCert(ctx, &pb.GetRootCertRequest{Mount: mount})
	if err != nil {
		return nil, err
	}
	return resp.CertPem, nil
}

// GetIssuerCert returns a named issuer certificate PEM for the given mount.
func (c *VaultClient) GetIssuerCert(ctx context.Context, mount, issuer string) ([]byte, error) {
	resp, err := c.pki.GetIssuerCert(ctx, &pb.GetIssuerCertRequest{Mount: mount, Issuer: issuer})
	if err != nil {
		return nil, err
	}
	return resp.CertPem, nil
}

// ImportRoot imports an existing root CA certificate and key into the given mount.
func (c *VaultClient) ImportRoot(ctx context.Context, token, mount, certPEM, keyPEM string) error {
	_, err := c.ca.ImportRoot(withToken(ctx, token), &pb.ImportRootRequest{
		Mount:   mount,
		CertPem: []byte(certPEM),
		KeyPem:  []byte(keyPEM),
	})
	return err
}

// CreateIssuerRequest holds parameters for creating an intermediate CA issuer.
type CreateIssuerRequest struct {
	Mount        string
	Name         string
	KeyAlgorithm string
	KeySize      int32
	Expiry       string
	MaxTTL       string
}

// CreateIssuer creates a new intermediate CA issuer on the given mount.
func (c *VaultClient) CreateIssuer(ctx context.Context, token string, req CreateIssuerRequest) error {
	_, err := c.ca.CreateIssuer(withToken(ctx, token), &pb.CreateIssuerRequest{
		Mount:        req.Mount,
		Name:         req.Name,
		KeyAlgorithm: req.KeyAlgorithm,
		KeySize:      req.KeySize,
		Expiry:       req.Expiry,
		MaxTtl:       req.MaxTTL,
	})
	return err
}

// ListIssuers returns the names of all issuers for the given mount.
func (c *VaultClient) ListIssuers(ctx context.Context, token, mount string) ([]string, error) {
	resp, err := c.ca.ListIssuers(withToken(ctx, token), &pb.ListIssuersRequest{Mount: mount})
	if err != nil {
		return nil, err
	}
	return resp.Issuers, nil
}

// IssueCertRequest holds parameters for issuing a leaf certificate.
type IssueCertRequest struct {
	Mount         string
	Issuer        string
	Profile       string
	CommonName    string
	DNSNames      []string
	IPAddresses   []string
	TTL           string
	KeyUsages     []string
	ExtKeyUsages  []string
}

// IssuedCert holds the result of a certificate issuance.
type IssuedCert struct {
	Serial    string
	CertPEM   string
	KeyPEM    string
	ChainPEM  string
	ExpiresAt string
}

// IssueCert issues a new leaf certificate from the named issuer.
func (c *VaultClient) IssueCert(ctx context.Context, token string, req IssueCertRequest) (*IssuedCert, error) {
	resp, err := c.ca.IssueCert(withToken(ctx, token), &pb.IssueCertRequest{
		Mount:         req.Mount,
		Issuer:        req.Issuer,
		Profile:       req.Profile,
		CommonName:    req.CommonName,
		DnsNames:      req.DNSNames,
		IpAddresses:   req.IPAddresses,
		Ttl:           req.TTL,
		KeyUsages:     req.KeyUsages,
		ExtKeyUsages:  req.ExtKeyUsages,
	})
	if err != nil {
		return nil, err
	}
	issued := &IssuedCert{
		Serial:   resp.Serial,
		CertPEM:  string(resp.CertPem),
		KeyPEM:   string(resp.KeyPem),
		ChainPEM: string(resp.ChainPem),
	}
	if resp.ExpiresAt != nil {
		issued.ExpiresAt = resp.ExpiresAt.AsTime().Format("2006-01-02T15:04:05Z")
	}
	return issued, nil
}

// SignCSRRequest holds parameters for signing an external CSR.
type SignCSRRequest struct {
	Mount   string
	Issuer  string
	CSRPEM  string
	Profile string
	TTL     string
}

// SignedCert holds the result of signing a CSR.
type SignedCert struct {
	Serial    string
	CertPEM   string
	ChainPEM  string
	ExpiresAt string
}

// SignCSR signs an externally generated CSR with the named issuer.
func (c *VaultClient) SignCSR(ctx context.Context, token string, req SignCSRRequest) (*SignedCert, error) {
	resp, err := c.ca.SignCSR(withToken(ctx, token), &pb.SignCSRRequest{
		Mount:   req.Mount,
		Issuer:  req.Issuer,
		CsrPem:  []byte(req.CSRPEM),
		Profile: req.Profile,
		Ttl:     req.TTL,
	})
	if err != nil {
		return nil, err
	}
	sc := &SignedCert{
		Serial:   resp.Serial,
		CertPEM:  string(resp.CertPem),
		ChainPEM: string(resp.ChainPem),
	}
	if resp.ExpiresAt != nil {
		sc.ExpiresAt = resp.ExpiresAt.AsTime().Format("2006-01-02T15:04:05Z")
	}
	return sc, nil
}

// CertDetail holds the full certificate record for the detail view.
type CertDetail struct {
	Serial     string
	Issuer     string
	CommonName string
	SANs       []string
	Profile    string
	IssuedBy   string
	IssuedAt   string
	ExpiresAt  string
	CertPEM    string
	Revoked    bool
	RevokedAt  string
	RevokedBy  string
}

// GetCert retrieves a full certificate record by serial number.
func (c *VaultClient) GetCert(ctx context.Context, token, mount, serial string) (*CertDetail, error) {
	resp, err := c.ca.GetCert(withToken(ctx, token), &pb.GetCertRequest{Mount: mount, Serial: serial})
	if err != nil {
		return nil, err
	}
	rec := resp.GetCert()
	if rec == nil {
		return nil, fmt.Errorf("cert not found")
	}
	cd := &CertDetail{
		Serial:     rec.Serial,
		Issuer:     rec.Issuer,
		CommonName: rec.CommonName,
		SANs:       rec.Sans,
		Profile:    rec.Profile,
		IssuedBy:   rec.IssuedBy,
		CertPEM:    string(rec.CertPem),
		Revoked:    rec.Revoked,
		RevokedBy:  rec.RevokedBy,
	}
	if rec.IssuedAt != nil {
		cd.IssuedAt = rec.IssuedAt.AsTime().Format("2006-01-02T15:04:05Z")
	}
	if rec.ExpiresAt != nil {
		cd.ExpiresAt = rec.ExpiresAt.AsTime().Format("2006-01-02T15:04:05Z")
	}
	if rec.RevokedAt != nil {
		cd.RevokedAt = rec.RevokedAt.AsTime().Format("2006-01-02T15:04:05Z")
	}
	return cd, nil
}

// RevokeCert marks a certificate as revoked.
func (c *VaultClient) RevokeCert(ctx context.Context, token, mount, serial string) error {
	_, err := c.ca.RevokeCert(withToken(ctx, token), &pb.RevokeCertRequest{Mount: mount, Serial: serial})
	return err
}

// DeleteCert permanently removes a certificate record.
func (c *VaultClient) DeleteCert(ctx context.Context, token, mount, serial string) error {
	_, err := c.ca.DeleteCert(withToken(ctx, token), &pb.DeleteCertRequest{Mount: mount, Serial: serial})
	return err
}

// CertSummary holds lightweight certificate metadata for list views.
type CertSummary struct {
	Serial     string
	Issuer     string
	CommonName string
	Profile    string
	IssuedBy   string
	IssuedAt   string
	ExpiresAt  string
}

// ListCerts returns all certificate summaries for the given mount.
func (c *VaultClient) ListCerts(ctx context.Context, token, mount string) ([]CertSummary, error) {
	resp, err := c.ca.ListCerts(withToken(ctx, token), &pb.ListCertsRequest{Mount: mount})
	if err != nil {
		return nil, err
	}
	certs := make([]CertSummary, 0, len(resp.Certs))
	for _, s := range resp.Certs {
		cs := CertSummary{
			Serial:     s.Serial,
			Issuer:     s.Issuer,
			CommonName: s.CommonName,
			Profile:    s.Profile,
			IssuedBy:   s.IssuedBy,
		}
		if s.IssuedAt != nil {
			cs.IssuedAt = s.IssuedAt.AsTime().Format("2006-01-02T15:04:05Z")
		}
		if s.ExpiresAt != nil {
			cs.ExpiresAt = s.ExpiresAt.AsTime().Format("2006-01-02T15:04:05Z")
		}
		certs = append(certs, cs)
	}
	return certs, nil
}