package webapp

import (
	"encoding/json"
	"errors"
	"net/http"
)

// clusterStatusResponse is the JSON the operator-facing
// /web/api/cluster/status endpoint returns. The shape is stable so the
// e2e shell script and any future frontend pages can pin against it.
//
// FSMConfigVersion / FSMOutboxLen / FSMPartition surface the FSM-side
// operator signals from plan section 6.1 (config_version, outbox
// length, partition_state) so a single GET tells the operator what
// config the cluster has adopted, whether the notification outbox is
// draining, and whether the cluster sees itself as partitioned.
type clusterStatusResponse struct {
	SelfID           string   `json:"self_id"`
	Role             string   `json:"role"`
	Term             uint64   `json:"term"`
	LeaderID         string   `json:"leader_id"`
	Voters           []string `json:"voters"`
	AppliedIndex     uint64   `json:"applied_index"`
	CommitIndex      uint64   `json:"commit_index"`
	FSMChecks        int      `json:"fsm_checks"`
	FSMMembers       int      `json:"fsm_membership"`
	FSMConfigVersion uint64   `json:"fsm_config_version"`
	FSMOutboxLen     int      `json:"fsm_outbox_len"`
	FSMPartition     string   `json:"fsm_partition"`
	ClusterID        string   `json:"cluster_id"`
	LocalAddr        string   `json:"local_addr"`
}

// handleClusterStatus serializes the current cluster state for the
// operator. Returns 503 if no cluster is attached; 200 otherwise.
//
// Admin-only: the worker webapp is single-tenant so the session
// middleware (requireSession) is the admin check. Cross-tenant
// protection is not required at this layer.
//
// The `r` parameter is unused but kept so the signature matches
// http.HandlerFunc (the route is registered via requireSession).
func (s *Server) handleClusterStatus(w http.ResponseWriter, _ *http.Request) {
	writeNoStore(w)
	if s.cluster == nil {
		http.Error(w, "cluster not configured", http.StatusServiceUnavailable)
		return
	}
	stats := s.cluster.Stats()
	resp := clusterStatusResponse{
		SelfID:           stats.NodeID,
		Role:             stats.State,
		Term:             stats.Term,
		LeaderID:         stats.Leader,
		Voters:           stats.Voters,
		AppliedIndex:     stats.AppliedIndex,
		CommitIndex:      stats.LastIndex,
		FSMChecks:        stats.FSMChecks,
		FSMMembers:       stats.FSMMembers,
		FSMConfigVersion: stats.FSMConfigVersion,
		FSMOutboxLen:     stats.FSMOutboxLen,
		FSMPartition:     stats.FSMPartition,
		ClusterID:        s.cluster.ClusterID(),
		LocalAddr:        s.cluster.LocalAddr(),
	}
	if resp.Voters == nil {
		resp.Voters = []string{}
	}
	w.Header().Set("Content-Type", "application/json; charset=utf-8")
	w.WriteHeader(http.StatusOK)
	if err := json.NewEncoder(w).Encode(resp); err != nil {
		s.deps.Logger.Printf("cluster status encode: %v", err)
	}
}

// ErrClusterNotConfigured is returned when a cluster-admin endpoint is
// hit on a server without a cluster attached.
var ErrClusterNotConfigured = errors.New("webapp: cluster not configured")