package agent

import (
	"context"
	"crypto/x509"
	"encoding/pem"
	"fmt"
	"net"
	"os"
	"time"

	"google.golang.org/grpc/codes"
	"google.golang.org/grpc/status"

	mcpv1 "git.wntrmute.dev/mc/mcp/gen/mcp/v1"
	mcproxy "git.wntrmute.dev/mc/mc-proxy/client/mcproxy"
	"git.wntrmute.dev/mc/mcp/internal/registry"
)

// SetupEdgeRoute provisions a TLS cert and registers an mc-proxy route for a
// public hostname. Called by the master on edge nodes.
func (a *Agent) SetupEdgeRoute(ctx context.Context, req *mcpv1.SetupEdgeRouteRequest) (*mcpv1.SetupEdgeRouteResponse, error) {
	a.Logger.Info("SetupEdgeRoute", "hostname", req.GetHostname(),
		"backend_hostname", req.GetBackendHostname(), "backend_port", req.GetBackendPort())

	// Validate required fields.
	if req.GetHostname() == "" {
		return nil, status.Error(codes.InvalidArgument, "hostname is required")
	}
	if req.GetBackendHostname() == "" {
		return nil, status.Error(codes.InvalidArgument, "backend_hostname is required")
	}
	if req.GetBackendPort() == 0 {
		return nil, status.Error(codes.InvalidArgument, "backend_port is required")
	}
	if !req.GetBackendTls() {
		return nil, status.Error(codes.InvalidArgument, "backend_tls must be true")
	}

	if a.Proxy == nil {
		return nil, status.Error(codes.FailedPrecondition, "mc-proxy not configured")
	}

	// Resolve the backend hostname to a Tailnet IP.
	ips, err := net.LookupHost(req.GetBackendHostname())
	if err != nil || len(ips) == 0 {
		return nil, status.Errorf(codes.InvalidArgument, "cannot resolve backend_hostname %q: %v", req.GetBackendHostname(), err)
	}
	backendIP := ips[0]

	// Validate the resolved IP is a Tailnet address (100.64.0.0/10).
	ip := net.ParseIP(backendIP)
	if ip == nil {
		return nil, status.Errorf(codes.InvalidArgument, "resolved IP %q is not valid", backendIP)
	}
	_, tailnet, _ := net.ParseCIDR("100.64.0.0/10")
	if !tailnet.Contains(ip) {
		return nil, status.Errorf(codes.InvalidArgument, "resolved IP %s is not a Tailnet address", backendIP)
	}

	backend := fmt.Sprintf("%s:%d", backendIP, req.GetBackendPort())

	// Provision TLS cert for the public hostname if cert provisioner is available.
	certPath := ""
	keyPath := ""
	if a.Certs != nil {
		if err := a.Certs.EnsureCert(ctx, req.GetHostname(), []string{req.GetHostname()}); err != nil {
			return nil, status.Errorf(codes.Internal, "provision cert for %s: %v", req.GetHostname(), err)
		}
		certPath = a.Proxy.CertPath(req.GetHostname())
		keyPath = a.Proxy.KeyPath(req.GetHostname())
	} else {
		// No cert provisioner — check if certs already exist on disk.
		certPath = a.Proxy.CertPath(req.GetHostname())
		keyPath = a.Proxy.KeyPath(req.GetHostname())
		if _, err := os.Stat(certPath); err != nil {
			return nil, status.Errorf(codes.FailedPrecondition, "no cert provisioner and cert not found at %s", certPath)
		}
	}

	// Register the L7 route in mc-proxy.
	route := mcproxy.Route{
		Hostname:   req.GetHostname(),
		Backend:    backend,
		Mode:       "l7",
		TLSCert:    certPath,
		TLSKey:     keyPath,
		BackendTLS: true,
	}
	if err := a.Proxy.AddRoute(ctx, ":443", route); err != nil {
		return nil, status.Errorf(codes.Internal, "add mc-proxy route: %v", err)
	}

	// Persist the edge route in the registry.
	if err := registry.CreateEdgeRoute(a.DB, req.GetHostname(), req.GetBackendHostname(), int(req.GetBackendPort()), certPath, keyPath); err != nil {
		a.Logger.Warn("failed to persist edge route", "hostname", req.GetHostname(), "err", err)
	}

	a.Logger.Info("edge route established",
		"hostname", req.GetHostname(), "backend", backend, "cert", certPath)

	return &mcpv1.SetupEdgeRouteResponse{}, nil
}

// RemoveEdgeRoute removes an mc-proxy route and cleans up the TLS cert for a
// public hostname. Called by the master on edge nodes.
func (a *Agent) RemoveEdgeRoute(ctx context.Context, req *mcpv1.RemoveEdgeRouteRequest) (*mcpv1.RemoveEdgeRouteResponse, error) {
	a.Logger.Info("RemoveEdgeRoute", "hostname", req.GetHostname())

	if req.GetHostname() == "" {
		return nil, status.Error(codes.InvalidArgument, "hostname is required")
	}

	if a.Proxy == nil {
		return nil, status.Error(codes.FailedPrecondition, "mc-proxy not configured")
	}

	// Remove the mc-proxy route.
	if err := a.Proxy.RemoveRoute(ctx, ":443", req.GetHostname()); err != nil {
		a.Logger.Warn("remove mc-proxy route", "hostname", req.GetHostname(), "err", err)
		// Continue — clean up cert and registry even if route removal fails.
	}

	// Remove the TLS cert.
	if a.Certs != nil {
		if err := a.Certs.RemoveCert(req.GetHostname()); err != nil {
			a.Logger.Warn("remove cert", "hostname", req.GetHostname(), "err", err)
		}
	}

	// Remove from registry.
	if err := registry.DeleteEdgeRoute(a.DB, req.GetHostname()); err != nil {
		a.Logger.Warn("delete edge route from registry", "hostname", req.GetHostname(), "err", err)
	}

	a.Logger.Info("edge route removed", "hostname", req.GetHostname())
	return &mcpv1.RemoveEdgeRouteResponse{}, nil
}

// ListEdgeRoutes returns all edge routes managed by this agent.
func (a *Agent) ListEdgeRoutes(_ context.Context, _ *mcpv1.ListEdgeRoutesRequest) (*mcpv1.ListEdgeRoutesResponse, error) {
	a.Logger.Debug("ListEdgeRoutes called")

	routes, err := registry.ListEdgeRoutes(a.DB)
	if err != nil {
		return nil, status.Errorf(codes.Internal, "list edge routes: %v", err)
	}

	resp := &mcpv1.ListEdgeRoutesResponse{}
	for _, r := range routes {
		er := &mcpv1.EdgeRoute{
			Hostname:        r.Hostname,
			BackendHostname: r.BackendHostname,
			BackendPort:     int32(r.BackendPort), //nolint:gosec // port is a small positive integer
		}

		// Read cert metadata if available.
		if r.TLSCert != "" {
			if certData, readErr := os.ReadFile(r.TLSCert); readErr == nil { //nolint:gosec // path from registry, not user input
				if block, _ := pem.Decode(certData); block != nil {
					if cert, parseErr := x509.ParseCertificate(block.Bytes); parseErr == nil {
						er.CertSerial = cert.SerialNumber.String()
						er.CertExpires = cert.NotAfter.UTC().Format(time.RFC3339)
					}
				}
			}
		}

		resp.Routes = append(resp.Routes, er)
	}

	return resp, nil
}

// HealthCheck returns the agent's health status. Called by the master when
// heartbeats are missed.
func (a *Agent) HealthCheck(_ context.Context, _ *mcpv1.HealthCheckRequest) (*mcpv1.HealthCheckResponse, error) {
	a.Logger.Debug("HealthCheck called")

	st := "healthy"
	containers := int32(0)

	// Count running containers if the runtime is available.
	if a.Runtime != nil {
		if list, err := a.Runtime.List(context.Background()); err == nil {
			containers = int32(len(list)) //nolint:gosec // container count is small
		} else {
			st = "degraded"
		}
	}

	return &mcpv1.HealthCheckResponse{
		Status:     st,
		Containers: containers,
	}, nil
}