package agent

import (
	"context"
	"fmt"
	"strings"

	mcpv1 "git.wntrmute.dev/mc/mcp/gen/mcp/v1"
	"git.wntrmute.dev/mc/mcp/internal/registry"
	"git.wntrmute.dev/mc/mcp/internal/runtime"
	"google.golang.org/grpc/codes"
	"google.golang.org/grpc/status"
)

// SyncDesiredState reconciles the agent's registry with the declared service
// specs. It creates or updates services and components, then discovers
// untracked containers and adds them with desired_state "ignore".
func (a *Agent) SyncDesiredState(ctx context.Context, req *mcpv1.SyncDesiredStateRequest) (*mcpv1.SyncDesiredStateResponse, error) {
	a.Logger.Info("SyncDesiredState", "services", len(req.GetServices()))

	known := make(map[string]bool)

	var results []*mcpv1.ServiceSyncResult
	for _, spec := range req.GetServices() {
		if spec.GetName() == "" {
			return nil, status.Error(codes.InvalidArgument, "service name is required")
		}
		r, names, err := a.syncService(ctx, spec)
		if err != nil {
			return nil, err
		}
		for _, n := range names {
			known[n] = true
		}
		results = append(results, r)
	}

	// Reconciliation: find containers not in the registry and add them.
	if err := a.reconcileUntracked(ctx, known); err != nil {
		a.Logger.Info("reconcile untracked containers failed", "error", err)
	}

	return &mcpv1.SyncDesiredStateResponse{Results: results}, nil
}

// syncService creates or updates a single service and its components.
// It returns the sync result and a list of container names that belong to
// this service.
func (a *Agent) syncService(_ context.Context, spec *mcpv1.ServiceSpec) (*mcpv1.ServiceSyncResult, []string, error) {
	result := &mcpv1.ServiceSyncResult{Name: spec.GetName()}
	var changes []string
	var containerNames []string

	desiredState := "running"
	if !spec.GetActive() {
		desiredState = "stopped"
	}

	// Create or update the service record.
	existing, err := registry.GetService(a.DB, spec.GetName())
	if err != nil {
		// Service does not exist; create it.
		if err := registry.CreateService(a.DB, spec.GetName(), spec.GetActive()); err != nil {
			return nil, nil, status.Errorf(codes.Internal, "create service %q: %v", spec.GetName(), err)
		}
		changes = append(changes, "created service")
	} else if existing.Active != spec.GetActive() {
		if err := registry.UpdateServiceActive(a.DB, spec.GetName(), spec.GetActive()); err != nil {
			return nil, nil, status.Errorf(codes.Internal, "update service %q: %v", spec.GetName(), err)
		}
		changes = append(changes, fmt.Sprintf("active: %v -> %v", existing.Active, spec.GetActive()))
	}

	// Create or update each component.
	for _, cs := range spec.GetComponents() {
		containerName := spec.GetName() + "-" + cs.GetName()
		containerNames = append(containerNames, containerName)

		comp := protoToComponent(spec.GetName(), cs, desiredState)

		if componentExists(a.DB, spec.GetName(), cs.GetName()) {
			if err := registry.UpdateComponentSpec(a.DB, comp); err != nil {
				return nil, nil, status.Errorf(codes.Internal, "update component %q/%q: %v", spec.GetName(), cs.GetName(), err)
			}
			if err := registry.UpdateComponentState(a.DB, spec.GetName(), cs.GetName(), desiredState, ""); err != nil {
				return nil, nil, status.Errorf(codes.Internal, "update component state %q/%q: %v", spec.GetName(), cs.GetName(), err)
			}
			changes = append(changes, fmt.Sprintf("updated %s", cs.GetName()))
		} else {
			if err := registry.CreateComponent(a.DB, comp); err != nil {
				return nil, nil, status.Errorf(codes.Internal, "create component %q/%q: %v", spec.GetName(), cs.GetName(), err)
			}
			changes = append(changes, fmt.Sprintf("created %s", cs.GetName()))
		}
	}

	result.Changed = len(changes) > 0
	result.Summary = strings.Join(changes, "; ")
	if !result.Changed {
		result.Summary = "no changes"
	}

	a.Logger.Info("sync service", "service", spec.GetName(), "changed", result.Changed, "summary", result.Summary)
	return result, containerNames, nil
}

// reconcileUntracked lists all containers from the runtime and adds any that
// are not already tracked in the registry with desired_state "ignore".
func (a *Agent) reconcileUntracked(ctx context.Context, known map[string]bool) error {
	containers, err := a.Runtime.List(ctx)
	if err != nil {
		return fmt.Errorf("list containers: %w", err)
	}

	for _, c := range containers {
		if known[c.Name] {
			continue
		}

		service, component, ok := parseContainerName(c.Name)
		if !ok {
			continue
		}

		if componentExists(a.DB, service, component) {
			continue
		}

		if _, err := registry.GetService(a.DB, service); err != nil {
			if err := registry.CreateService(a.DB, service, true); err != nil {
				a.Logger.Info("reconcile: create service failed", "service", service, "error", err)
				continue
			}
		}

		comp := &registry.Component{
			Name:          component,
			Service:       service,
			Image:         c.Image,
			Network:       c.Network,
			UserSpec:      c.User,
			Restart:       c.Restart,
			DesiredState:  "ignore",
			ObservedState: c.State,
			Version:       runtime.ExtractVersion(c.Image),
		}
		if err := registry.CreateComponent(a.DB, comp); err != nil {
			a.Logger.Info("reconcile: create component failed", "container", c.Name, "error", err)
			continue
		}

		a.Logger.Info("reconcile: adopted untracked container", "container", c.Name, "desired_state", "ignore")
	}

	return nil
}

// protoToComponent converts a proto ComponentSpec to a registry Component.
func protoToComponent(service string, cs *mcpv1.ComponentSpec, desiredState string) *registry.Component {
	return &registry.Component{
		Name:         cs.GetName(),
		Service:      service,
		Image:        cs.GetImage(),
		Network:      cs.GetNetwork(),
		UserSpec:     cs.GetUser(),
		Restart:      cs.GetRestart(),
		Ports:        cs.GetPorts(),
		Volumes:      cs.GetVolumes(),
		Cmd:          cs.GetCmd(),
		DesiredState: desiredState,
		Version:      runtime.ExtractVersion(cs.GetImage()),
	}
}

// parseContainerName splits "service-component" into its parts. Returns false
// if the name does not contain a hyphen.
func parseContainerName(name string) (service, component string, ok bool) {
	i := strings.IndexByte(name, '-')
	if i < 0 {
		return "", "", false
	}
	return name[:i], name[i+1:], true
}