package security

import (
	"context"
	"net"
	"strings"

	"github.com/seaweedfs/seaweedfs/weed/glog"
	"google.golang.org/grpc/codes"
	"google.golang.org/grpc/credentials"
	"google.golang.org/grpc/metadata"
	"google.golang.org/grpc/peer"
	"google.golang.org/grpc/status"
)

// CheckGrpcAdminPeer authenticates the peer of an admin-plane gRPC handler:
// a client certificate verified by the server's TLS config, or a Bearer token
// signed by signingKey (jwt.filer_signing.key). With no key configured remote
// callers cannot be told apart, so only local clients (unix socket, loopback,
// or an address assigned to this host) are allowed.
func CheckGrpcAdminPeer(ctx context.Context, signingKey SigningKey) error {
	if isMtlsVerifiedPeer(ctx) {
		return nil
	}
	if len(signingKey) == 0 {
		return CheckLocalGrpcPeer(ctx)
	}
	md, ok := metadata.FromIncomingContext(ctx)
	if !ok {
		return status.Error(codes.Unauthenticated, "missing metadata")
	}
	authHeaders := md.Get("authorization")
	if len(authHeaders) == 0 {
		return status.Error(codes.Unauthenticated, "missing authorization metadata")
	}
	raw := strings.TrimSpace(authHeaders[0])
	parts := strings.Fields(raw)
	if len(parts) != 2 || !strings.EqualFold(parts[0], "Bearer") || parts[1] == "" {
		return status.Error(codes.Unauthenticated, "authorization header must use Bearer scheme")
	}
	parsed, err := DecodeJwt(signingKey, EncodedJwt(parts[1]), &SeaweedFilerAdminClaims{})
	if err != nil || parsed == nil || !parsed.Valid {
		return status.Error(codes.Unauthenticated, "invalid admin token")
	}
	if claims, ok := parsed.Claims.(*SeaweedFilerAdminClaims); !ok || claims.SessionId != "" {
		return status.Error(codes.Unauthenticated, "invalid admin token")
	}
	return nil
}

// GrpcAdminPeerCredentials returns outgoing metadata carrying a Bearer token
// for admin-plane gRPC handlers, or nil when no signing key is configured.
func GrpcAdminPeerCredentials(signingKey SigningKey, expiresAfterSec int) metadata.MD {
	token := GenJwtForFilerAdmin(signingKey, expiresAfterSec)
	if token == "" {
		return nil
	}
	return metadata.Pairs("authorization", "Bearer "+string(token))
}

func isMtlsVerifiedPeer(ctx context.Context) bool {
	pr, ok := peer.FromContext(ctx)
	if !ok {
		return false
	}
	tlsInfo, ok := pr.AuthInfo.(credentials.TLSInfo)
	return ok && len(tlsInfo.State.VerifiedChains) > 0
}

// CheckLocalGrpcPeer admits only clients on this host: unix sockets, loopback,
// or an address assigned to a local interface.
func CheckLocalGrpcPeer(ctx context.Context) error {
	if ctx == nil {
		return status.Error(codes.Unauthenticated, "admin gRPC calls require jwt.filer_signing.key or a local client")
	}
	pr, ok := peer.FromContext(ctx)
	if !ok {
		return status.Error(codes.Unauthenticated, "admin gRPC calls require jwt.filer_signing.key or a local client")
	}
	if _, isUnix := pr.Addr.(*net.UnixAddr); isUnix {
		return nil
	}
	var ip net.IP
	if tcpAddr, ok := pr.Addr.(*net.TCPAddr); ok {
		ip = tcpAddr.IP
	} else if h, _, err := net.SplitHostPort(pr.Addr.String()); err == nil {
		ip = net.ParseIP(h)
	} else {
		ip = net.ParseIP(pr.Addr.String())
	}
	if ip != nil && (ip.IsLoopback() || isLocalAddress(ip)) {
		return nil
	}
	glog.V(1).Infof("rejected unauthenticated admin gRPC call from %s: no jwt.filer_signing.key configured", pr.Addr)
	return status.Error(codes.Unauthenticated, "admin gRPC calls require jwt.filer_signing.key or a local client")
}

// isLocalAddress enumerates interfaces per call: only reachable for
// non-loopback TCP peers on the no-key admin path, which is low-volume —
// and a cached set would keep trusting an address after it is removed from
// the host and reassigned.
func isLocalAddress(ip net.IP) bool {
	addrs, err := net.InterfaceAddrs()
	if err != nil {
		return false
	}
	for _, a := range addrs {
		if ipNet, ok := a.(*net.IPNet); ok && ipNet.IP.Equal(ip) {
			return true
		}
	}
	return false
}