package workercluster

import "encoding/json"

// EntryType enumerates the kinds of replicated log entries the FSM
// understands. Every log entry committed through the Raft Apply path
// carries an Entry of one of these kinds.
//
// The set is the subset from plan section 6.2 that this implementation
// actually exercises today. The remaining kinds are defined in
// distworker/entries.go placeholders (ObserverSetUpdate, IncidentObserve,
// ...) so later phases can add Apply branches without a wire-format
// churn.
type EntryType string

const (
	// EntryConfigAdopt installs a new adopted critical-check list
	// into the FSM. Replaces any previously adopted list.
	EntryConfigAdopt EntryType = "config.adopt"

	// EntryObserverSetUpdate installs a new observer set with a
	// version stamp.
	EntryObserverSetUpdate EntryType = "observer_set.update"

	// EntryMembershipProposeAdd appends a Member to the membership
	// cache. The Raft library itself handles the voter promotion; the
	// FSM just keeps a denormalized mirror.
	EntryMembershipProposeAdd EntryType = "membership.propose_add"

	// EntryMembershipDemote flips a voter's role to observer.
	EntryMembershipDemote EntryType = "membership.demote"

	// EntryMembershipRemove drops a Member from the membership cache.
	EntryMembershipRemove EntryType = "membership.remove"

	// EntryIncidentObserve appends one observer vote for a check.
	EntryIncidentObserve EntryType = "incident.observe"

	// EntryIncidentTransition records a state transition produced by
	// the FSM from committed observations.
	EntryIncidentTransition EntryType = "incident.transition"

	// EntryOutboxEnqueue appends notification outbox metadata.
	EntryOutboxEnqueue EntryType = "outbox.enqueue"

	// EntryOutboxDelivered marks an outbox entry as delivered.
	EntryOutboxDelivered EntryType = "outbox.delivered"

	// EntryOutboxAck records a delivery ack / duplicate marker.
	EntryOutboxAck EntryType = "outbox.ack"

	// EntryPartitionReport stores the cluster's view of network
	// partition state.
	EntryPartitionReport EntryType = "partition.report"

	// EntryDiagnosticsUpdate stores per-worker health metadata.
	EntryDiagnosticsUpdate EntryType = "diagnostics.update"
)

// Entry is the wire format the FSM expects on every Apply. The Data
// field holds the JSON-encoded payload of the matching struct.
type Entry struct {
	Type     EntryType       `json:"type"`
	Term     uint64          `json:"term,omitempty"`
	Index    uint64          `json:"index,omitempty"`
	ActorID  string          `json:"actor_id,omitempty"`
	Version  uint64          `json:"version,omitempty"`
	Adopted  json.RawMessage `json:"adopted,omitempty"`
	Set      json.RawMessage `json:"set,omitempty"`
	Member   json.RawMessage `json:"member,omitempty"`
	State    json.RawMessage `json:"state,omitempty"`
	Observe  json.RawMessage `json:"observe,omitempty"`
	Outbox   json.RawMessage `json:"outbox,omitempty"`
	OutboxID uint64          `json:"outbox_seq,omitempty"`
	Report   json.RawMessage `json:"report,omitempty"`
	Diag     json.RawMessage `json:"diag,omitempty"`
}

// ConfigAdoptPayload is the body of an EntryConfigAdopt entry.
type ConfigAdoptPayload struct {
	Version uint64                `json:"version"`
	Actor   string                `json:"actor"`
	Checks  []CriticalCheckConfig `json:"checks"`
}

// ObserverSetPayload is the body of an EntryObserverSetUpdate entry.
type ObserverSetPayload struct {
	Set ObserverSet `json:"set"`
}

// MemberPayload is the body of an EntryMembershipProposeAdd,
// EntryMembershipDemote, and EntryMembershipRemove entries.
type MemberPayload struct {
	Member Member  `json:"member"`
	Reason string  `json:"reason,omitempty"`
	Prev   *Member `json:"prev,omitempty"` // populated on demote/remove
}

// IncidentObservePayload is one observer vote for a check.
type IncidentObservePayload struct {
	CheckID    int64  `json:"check_id"`
	WorkerID   string `json:"worker_id"`
	Label      string `json:"label"` // ok | warn | down | unknown
	ObservedIx uint64 `json:"observed_at_index"`
}

// IncidentTransitionPayload is the FSM-produced state transition
// recorded after a quorum rule fires.
type IncidentTransitionPayload struct {
	CheckID int64         `json:"check_id"`
	State   IncidentState `json:"state"`
	Reason  string        `json:"reason,omitempty"`
}

// OutboxPayload is the body of an EntryOutboxEnqueue entry.
type OutboxPayload struct {
	Entry OutboxMeta `json:"entry"`
}

// OutboxUpdatePayload is the body of EntryOutboxDelivered and
// EntryOutboxAck entries.
type OutboxUpdatePayload struct {
	Seq       uint64 `json:"seq"`
	State     string `json:"state"`
	Attempts  int    `json:"attempts"`
	LastError string `json:"last_error,omitempty"`
}

// PartitionReportPayload is the body of an EntryPartitionReport entry.
type PartitionReportPayload struct {
	State PartitionState `json:"state"`
}

// DiagnosticsPayload is the body of an EntryDiagnosticsUpdate entry.
type DiagnosticsPayload struct {
	Diag WorkerDiagnostics `json:"diag"`
}

// EncodeEntry marshals a fully-populated Entry to JSON bytes ready to
// hand to raft.Apply.
func EncodeEntry(e *Entry) ([]byte, error) {
	return json.Marshal(e)
}

// DecodeEntry parses Entry bytes back into the wire struct.
func DecodeEntry(b []byte) (Entry, error) {
	var e Entry
	if err := json.Unmarshal(b, &e); err != nil {
		return e, err
	}
	return e, nil
}