package ipc

import (
	"context"
	"database/sql"
	"encoding/json"
	"errors"
	"fmt"
	"net"
	"os"
	"sync"
	"sync/atomic"
	"time"

	"github.com/kami/maven/internal/store"
	"golang.org/x/sys/unix"
)

// storeAPI — adapts *store.Store to CoreAPI. The daemon constructs one of
// these inside the core process; the socket Server calls it through the
// CoreAPI interface, so over-the-wire and in-process callers behave
// identically. The translation here is the only place store sentinels cross
// the wire: store.ErrNoFact becomes ipc.ErrNoFact, etc. — keeping the module
// view of errors stable regardless of transport.
type storeAPI struct {
	s *store.Store
}

// NewStoreAPI wraps a *store.Store as a CoreAPI. The store is the sqlcipher-
// unlocked handle held ONLY in core's address space; this adapter never
// returns it to a caller — core mediates.
func NewStoreAPI(s *store.Store) CoreAPI { return &storeAPI{s: s} }

func (a *storeAPI) WriteFact(ctx context.Context, req WriteFactReq) (int64, error) {
	var voids sql.NullInt64
	if req.VoidsID != nil {
		voids = sql.NullInt64{Int64: *req.VoidsID, Valid: true}
	}
	id, err := a.s.WriteFact(ctx, req.Ts, store.FactKind(req.Kind), req.Key, req.Value, req.Source, req.Confidence, voids)
	return id, mapErr(err)
}

func (a *storeAPI) LatestFact(ctx context.Context, key string) (Fact, error) {
	f, err := a.s.LatestFact(ctx, key)
	if err != nil {
		return Fact{}, mapErr(err)
	}
	return toFact(f), nil
}

func (a *storeAPI) LatestFactBySource(ctx context.Context, key, source string) (Fact, error) {
	f, err := a.s.LatestFactBySource(ctx, key, source)
	if err != nil {
		return Fact{}, mapErr(err)
	}
	return toFact(f), nil
}

func (a *storeAPI) Since(ctx context.Context, key string, now time.Time) (time.Duration, error) {
	d, err := a.s.Since(ctx, key, now)
	return d, mapErr(err)
}

func (a *storeAPI) Presence(ctx context.Context) (Presence, error) {
	b, score, upd, err := a.s.LoadPresenceState(ctx)
	if err != nil {
		return Presence{}, fmt.Errorf("ipc: load presence: %w", err)
	}
	return Presence{Bucket: Bucket(b), Score: score, Updated: upd}, nil
}

func (a *storeAPI) CreateReminder(ctx context.Context, fire time.Time, payload, cron string) (int64, error) {
	id, err := a.s.CreateReminder(ctx, fire, payload, cron)
	return id, mapErr(err)
}

func (a *storeAPI) MarkReminder(ctx context.Context, id int64, status string) error {
	return mapErr(a.s.MarkReminder(ctx, id, status))
}

func (a *storeAPI) ListReminders(ctx context.Context, n int) ([]Reminder, error) {
	rs, err := a.s.ListReminders(ctx, n)
	if err != nil {
		return nil, mapErr(err)
	}
	out := make([]Reminder, len(rs))
	for i, r := range rs {
		out[i] = toReminder(r)
	}
	return out, nil
}

func (a *storeAPI) RescheduleReminder(ctx context.Context, id int64, now time.Time) error {
	return mapErr(a.s.RescheduleReminder(ctx, id, now))
}

func (a *storeAPI) RecordNudge(ctx context.Context, rule, channel, message string, ts time.Time) (int64, error) {
	id, err := a.s.RecordNudge(ctx, rule, channel, message, ts)
	return id, mapErr(err)
}

func (a *storeAPI) ResolveNudge(ctx context.Context, id int64, outcome string, ts time.Time) error {
	return mapErr(a.s.ResolveNudge(ctx, id, outcome, ts))
}

func (a *storeAPI) RecentOutcomes(ctx context.Context, rule string, n int) ([]string, error) {
	out, err := a.s.RecentOutcomes(ctx, rule, n)
	return out, mapErr(err)
}

func (a *storeAPI) RecentFacts(ctx context.Context, n int) ([]Fact, error) {
	fs, err := a.s.RecentFacts(ctx, n)
	if err != nil {
		return nil, mapErr(err)
	}
	out := make([]Fact, len(fs))
	for i, f := range fs {
		out[i] = toFact(f)
	}
	return out, nil
}

func (a *storeAPI) CalendarEvents(ctx context.Context, from, to time.Time) ([]Fact, error) {
	fs, err := a.s.CalendarEvents(ctx, from, to)
	if err != nil {
		return nil, mapErr(err)
	}
	out := make([]Fact, len(fs))
	for i, f := range fs {
		out[i] = toFact(f)
	}
	return out, nil
}

func (a *storeAPI) RecentNudges(ctx context.Context, n int) ([]Nudge, error) {
	ns, err := a.s.RecentNudges(ctx, n)
	if err != nil {
		return nil, mapErr(err)
	}
	out := make([]Nudge, len(ns))
	for i, ng := range ns {
		out[i] = toNudge(ng)
	}
	return out, nil
}

func (a *storeAPI) WriteNote(ctx context.Context, ts time.Time, text string, embedding []float32, source string) (int64, error) {
	id, err := a.s.WriteNote(ctx, ts, text, embedding, source)
	return id, mapErr(err)
}

func (a *storeAPI) QueryNotes(ctx context.Context, embedding []float32, k int) ([]Note, error) {
	ns, err := a.s.QueryNotes(ctx, embedding, k)
	if err != nil {
		return nil, mapErr(err)
	}
	out := make([]Note, len(ns))
	for i, n := range ns {
		out[i] = toNote(n)
	}
	return out, nil
}

func (a *storeAPI) RecentNotes(ctx context.Context, n int) ([]Note, error) {
	ns, err := a.s.RecentNotes(ctx, n)
	if err != nil {
		return nil, mapErr(err)
	}
	out := make([]Note, len(ns))
	for i, note := range ns {
		out[i] = toNote(note)
	}
	return out, nil
}

func (a *storeAPI) ProposeTool(ctx context.Context, name, utterance, scope string, ts time.Time) (bool, error) {
	ok, err := a.s.ProposeTool(ctx, name, utterance, scope, ts)
	return ok, mapErr(err)
}

func (a *storeAPI) EnableTool(ctx context.Context, name string, cmd []string, destructive bool, scope string, ts time.Time) error {
	return mapErr(a.s.EnableTool(ctx, name, cmd, destructive, scope, ts))
}

func (a *storeAPI) DisableTool(ctx context.Context, name string) error {
	return mapErr(a.s.DisableTool(ctx, name))
}

func (a *storeAPI) LookupTool(ctx context.Context, name string) (Tool, error) {
	t, err := a.s.LookupTool(ctx, name)
	if err != nil {
		return Tool{}, mapErr(err)
	}
	return toTool(t), nil
}

func (a *storeAPI) RevertFact(ctx context.Context, key string) (int64, error) {
	_, newID, err := a.s.VoidLatestFact(ctx, key, "feedback", time.Now())
	return newID, mapErr(err)
}

func (a *storeAPI) Chat(ctx context.Context, text string) (string, error) {
	return "", errors.New("store: chat not available via direct store API")
}

func (a *storeAPI) TickTrace(ctx context.Context) (TickTrace, error) {
	return TickTrace{}, errors.New("store: tick trace not available via direct store API")
}

func (a *storeAPI) ListTools(ctx context.Context, status string) ([]Tool, error) {
	ts, err := a.s.ListTools(ctx, status)
	if err != nil {
		return nil, mapErr(err)
	}
	out := make([]Tool, len(ts))
	for i, t := range ts {
		out[i] = toTool(t)
	}
	return out, nil
}

func (a *storeAPI) DeleteTool(ctx context.Context, name string) error {
	return mapErr(a.s.DeleteTool(ctx, name))
}

func (a *storeAPI) ListProposedRoutines(ctx context.Context) ([]ProposedRoutine, error) {
	rs, err := a.s.ListProposedRoutines(ctx)
	if err != nil {
		return nil, mapErr(err)
	}
	out := make([]ProposedRoutine, len(rs))
	for i, r := range rs {
		out[i] = ProposedRoutine{
			ID:           r.ID,
			Action:       r.Action,
			Object:       r.Object,
			IntervalDays: r.IntervalDays,
			Status:       r.Status,
			CreatedTs:    r.CreatedTs.UnixMilli(),
		}
		if r.ReminderID != nil {
			out[i].ReminderID = r.ReminderID
		}
	}
	return out, nil
}

func (a *storeAPI) DismissProposedRoutine(ctx context.Context, id int64) error {
	return mapErr(a.s.DismissProposedRoutine(ctx, id))
}

func toTool(t store.Tool) Tool {
	return Tool{
		Name: t.Name, Scope: t.Scope, Cmd: t.Cmd, Destructive: t.Destructive,
		Status: t.Status, Utterance: t.Utterance, Created: t.CreatedTs, Updated: t.UpdatedTs,
	}
}

func toReminder(r store.Reminder) Reminder {
	return Reminder{
		ID:         r.ID,
		CreatedTs:  r.CreatedTs,
		FireTs:     r.FireTs,
		NextFireTs: r.NextFireTs,
		Payload:    r.Payload,
		Status:     r.Status,
		Cron:       r.Cron,
	}
}

func toNote(n store.Note) Note {
	return Note{ID: n.ID, Ts: n.Ts, Text: n.Text, Source: n.Source, Score: n.Score}
}

func toNudge(n store.Nudge) Nudge {
	out := Nudge{
		ID: n.ID, Ts: n.Ts, Rule: n.Rule, Channel: n.Channel,
		Message: n.Message, Outcome: n.Outcome,
	}
	if n.OutcomeTs.Valid {
		v := n.OutcomeTs.Int64
		out.OutcomeTs = &v
	}
	return out
}

func toFact(f store.Fact) Fact {
	out := Fact{
		ID:         f.ID,
		Ts:         f.Ts,
		Kind:       string(f.Kind),
		Key:        f.Key,
		Value:      f.Value,
		Source:     f.Source,
		Confidence: f.Confidence,
	}
	if f.VoidsID.Valid {
		v := f.VoidsID.Int64
		out.VoidsID = &v
	}
	return out
}

// mapErr — store sentinel ↔ ipc sentinel. An unrecognized store error is
// wrapped but not mapped (server-side dispatch surfaces it as codeInternal,
// keeping internal text off the wire except to the daemon log).
func mapErr(err error) error {
	if err == nil {
		return nil
	}
	switch {
	case errors.Is(err, store.ErrNoFact):
		return ErrNoFact
	case errors.Is(err, store.ErrConfidence):
		return ErrConfidence
	case errors.Is(err, store.ErrVoidsMissing):
		return ErrVoidsMissing
	case errors.Is(err, store.ErrNudgeNotFound):
		return ErrNudgeNotFound
	case errors.Is(err, store.ErrNudgeOutcome):
		return ErrNudgeOutcome
	case errors.Is(err, store.ErrReminderNotFound):
		return ErrReminderNotFound
	case errors.Is(err, store.ErrReminderState):
		return ErrReminderState
	case errors.Is(err, store.ErrToolNotFound):
		return ErrToolNotFound
	}
	return err
}

// Server — the core side of the boundary. Listens on a unix domain socket,
// accepts module connections, frames requests to a CoreAPI and responses back.
// One Server per daemon process; concurrent connections are handled in their
// own goroutine but share the single CoreAPI (and therefore the single store
// writer — store is single-connection, SetMaxOpenConns(1), so serialization is
// already guaranteed at the db; the Server adds no locking of its own).
type Server struct {
	api  atomic.Value // stores CoreAPI
	path string

	ln     net.Listener
	wg     sync.WaitGroup
	done   chan struct{}
	accept sync.Mutex // guards wg.Add vs Close's wg.Wait sequence

	// Check — optional authorization hook. dispatch runs it BEFORE method
	// dispatch, with the raw params, so the auth layer can make verdicts
	// that depend on the call's shape (e.g. WriteFact's source). A non-nil
	// error aborts the call; the wire code is codeForbidden when the error
	// satisfies errors.Is(ErrForbidden), else codeInternal.
	//
	// Nil ⇒ today's auth floor: any same-uid caller (the 0600 socket perms)
	// is authorized, identical to pre-auth behavior. The daemon sets this to
	// auth.Gate.Check once the auth layer is constructed; there is no module
	// change to gain or lose the seam.
	Check CheckFunc

	// StepUp — optional handler for MethodAssertStepUp. When a real Session
	// (PasskeySession) is wired, the daemon sets this to session.Assert so a
	// module (mavweb) can assert a user-verification gesture over IPC. Nil ⇒
	// MethodAssertStepUp returns ErrUnknownMethod (same as pre-stepup floor).
	StepUp StepUpFunc

	// WrapKeyFn — wraps the in-memory store encryption key with a passkey
	// credential public key (HKDF-AESGCM) and writes the wrapped blob to disk.
	// Set by the daemon; nil ⇒ MethodStoreEncryptionKey returns ErrUnknownMethod.
	WrapKeyFn WrapKeyFunc

	// UnlockFn — unwraps the store encryption key from the wrapped blob using
	// the passkey credential public key, opens the encrypted store, and wires
	// the rest of the daemon (voice, loop, delivery). Set by the daemon when
	// in locked mode; nil ⇒ MethodUnlock returns ErrUnknownMethod.
	UnlockFn UnlockFunc

	// now is injected so tests can drive time; the loop already works in
	// absolute ts supplied by callers, so this isn't load-bearing for live ops.
}

// WrapKeyFunc — wraps the store encryption key with the given credential
// public key and persists the wrapped blob.
type WrapKeyFunc func(ctx context.Context, publicKey []byte) error

// UnlockFunc — unwraps the store encryption key using the given credential
// public key and completes daemon initialization.
type UnlockFunc func(ctx context.Context, publicKey []byte) error

// CheckFunc — the auth hook signature. Wired by the daemon (auth.Gate.Check
// satisfies this); dispatch calls it once per request after param-unmarshal
// independence (it gets the raw params, may unmarshal what it needs — ipc
// already unmarshals for the typed call separately). Keeping Check on raw
// params means ipc doesn't need to know each method's authority shape, and
// auth doesn't need to leak implementation into ipc.
type CheckFunc func(ctx context.Context, m Method, params json.RawMessage) error

// StepUpFunc — records a user-verification gesture. Set by the daemon when
// a real Session is wired (PasskeySession); nil means not available.
// MethodAssertStepUp dispatch calls this instead of going through CoreAPI.
type StepUpFunc func(ctx context.Context) error

// Listen creates a Server bound to path. path's parent dir must exist and be
// 0700 (we chmod it if we own it); the socket file itself is created 0600 so
// only the same unix user can connect — the current "auth floor", same radius
// as wg at the network boundary. Removing a stale socket at path first lets
// the daemon restart cleanly.
func Listen(path string, api CoreAPI) (*Server, error) {
	_ = os.Remove(path) // stale socket from a crashed daemon; ignore missing
	if err := os.MkdirAll(parentDir(path), 0o700); err != nil {
		return nil, fmt.Errorf("ipc: mkdir socket dir: %w", err)
	}
	// umask could widen the perms on socket creation; tighten then chmod to
	// be explicit. 0600 ⇒ read+write by owner only.
	oldMask := unix.Umask(0o077)
	ln, err := net.Listen("unix", path)
	unix.Umask(oldMask)
	if err != nil {
		return nil, fmt.Errorf("ipc: listen %s: %w", path, err)
	}
	if err := os.Chmod(path, 0o600); err != nil {
		_ = ln.Close()
		_ = os.Remove(path)
		return nil, fmt.Errorf("ipc: chmod socket: %w", err)
	}
	s := &Server{
		path: path,
		ln:   ln,
		done: make(chan struct{}),
	}
	s.api.Store(api)
	return s, nil
}

// Serve accepts connections until the listener closes. Each connection is
// served in its own goroutine; a panicking handler or a malformed frame tears
// down only that conn, not the server (a misbehaving module can't kill core).
func (s *Server) Serve() error {
	for {
		c, err := s.ln.Accept()
		if err != nil {
			select {
			case <-s.done:
				return nil // graceful Close
			default:
				return fmt.Errorf("ipc: accept: %w", err)
			}
		}
		// wg.Add under accept mutex so Close's wg.Wait (also under accept) sees
		// a consistent counter — a connection accepted just before Close closes
		// the listener must be tracked before Wait starts.
		s.accept.Lock()
		s.wg.Add(1)
		s.accept.Unlock()
		go func(c net.Conn) {
			defer s.wg.Done()
			defer c.Close()
			s.serveConn(c)
		}(c)
	}
}

func (s *Server) serveConn(c net.Conn) {
	caller, callerOK := peerCaller(c)
	ctx := context.Background()
	if callerOK {
		ctx = WithCaller(ctx, caller)
	}
	for {
		var req Request
		if err := readFrame(c, &req); err != nil {
			return // EOF or malformed ⇒ end this conn; nothing to recover
		}
		// redispatch expects the framework's recover so one bad call can't
		// take the goroutine (and therefore the conn) with it.
		result, err := s.safeDispatch(ctx, req)
		resp := Response{}
		if err != nil {
			resp.Error = rpcErr(err)
		} else {
			resp.Result = result
		}
		if err := writeFrame(c, resp); err != nil {
			return
		}
	}
}

func (s *Server) safeDispatch(ctx context.Context, req Request) (result json.RawMessage, err error) {
	defer func() {
		if r := recover(); r != nil {
			err = fmt.Errorf("ipc: panic dispatching %s: %v", req.Method, r)
		}
	}()
	return s.dispatch(ctx, req)
}

// dispatch unmarshals params for req.Method and calls the matching CoreAPI
// method. Unknown method ⇒ ErrUnknownMethod; a malformed params payload ⇒
// ErrBadParams with the underlying text (local, server-side, not shipped to
// the module except as a generic message via rpcErr).
//
// Authorization runs ONCE at the top: if Server.Check is set, we call it with
// the raw params before any method-specific unmarshal; auth unmarshals fields
// it cares about (WriteFact's source, etc.) itself. A nil Check is the floor
// and is invisible at the wire — pre-auth Server behavior is unchanged.
func (s *Server) dispatch(ctx context.Context, req Request) (json.RawMessage, error) {
	api := s.api.Load().(CoreAPI)
	if s.Check != nil {
		if err := s.Check(ctx, req.Method, req.Params); err != nil {
			return nil, err
		}
	}
	switch req.Method {
	case MethodWriteFact:
		var p WriteFactReq
		if err := unmarshalParams(req.Params, &p); err != nil {
			return nil, err
		}
		id, err := api.WriteFact(ctx, p)
		return marshalResult(idResp{ID: id}), err

	case MethodLatestFact:
		var p keyReq
		if err := unmarshalParams(req.Params, &p); err != nil {
			return nil, err
		}
		f, err := api.LatestFact(ctx, p.Key)
		if err != nil {
			return nil, err
		}
		return marshalResult(f), nil

	case MethodLatestFactBySource:
		var p keySourceReq
		if err := unmarshalParams(req.Params, &p); err != nil {
			return nil, err
		}
		f, err := api.LatestFactBySource(ctx, p.Key, p.Source)
		if err != nil {
			return nil, err
		}
		return marshalResult(f), nil

	case MethodSince:
		var p sinceReq
		if err := unmarshalParams(req.Params, &p); err != nil {
			return nil, err
		}
		d, err := api.Since(ctx, p.Key, p.Now)
		if err != nil {
			return nil, err
		}
		return marshalResult(sinceResp{Dur: d}), nil

	case MethodPresence:
		pres, err := api.Presence(ctx)
		if err != nil {
			return nil, err
		}
		return marshalResult(pres), nil

	case MethodCreateReminder:
		var p createReminderReq
		if err := unmarshalParams(req.Params, &p); err != nil {
			return nil, err
		}
		id, err := api.CreateReminder(ctx, p.Fire, p.Payload, p.Cron)
		return marshalResult(idResp{ID: id}), err

	case MethodMarkReminder:
		var p markReminderReq
		if err := unmarshalParams(req.Params, &p); err != nil {
			return nil, err
		}
		err := api.MarkReminder(ctx, p.ID, p.Status)
		return marshalResult(nil), err

	case MethodListReminders:
		var p nReq
		if err := unmarshalParams(req.Params, &p); err != nil {
			return nil, err
		}
		out, err := api.ListReminders(ctx, p.N)
		if err != nil {
			return nil, err
		}
		if out == nil {
			out = []Reminder{}
		}
		return marshalResult(out), nil

	case MethodRecordNudge:
		var p recordNudgeReq
		if err := unmarshalParams(req.Params, &p); err != nil {
			return nil, err
		}
		id, err := api.RecordNudge(ctx, p.Rule, p.Channel, p.Message, p.Ts)
		return marshalResult(idResp{ID: id}), err

	case MethodResolveNudge:
		var p resolveNudgeReq
		if err := unmarshalParams(req.Params, &p); err != nil {
			return nil, err
		}
		err := api.ResolveNudge(ctx, p.ID, p.Outcome, p.Ts)
		return marshalResult(nil), err

	case MethodRecentOutcomes:
		var p outcomesReq
		if err := unmarshalParams(req.Params, &p); err != nil {
			return nil, err
		}
		out, err := api.RecentOutcomes(ctx, p.Rule, p.N)
		if err != nil {
			return nil, err
		}
		if out == nil {
			out = []string{} // stable non-null on the wire
		}
		return marshalResult(out), nil

	case MethodRecentFacts:
		var p nReq
		if err := unmarshalParams(req.Params, &p); err != nil {
			return nil, err
		}
		out, err := api.RecentFacts(ctx, p.N)
		if err != nil {
			return nil, err
		}
		if out == nil {
			out = []Fact{}
		}
		return marshalResult(out), nil

	case MethodCalendarEvents:
		var p calendarEventsReq
		if err := unmarshalParams(req.Params, &p); err != nil {
			return nil, err
		}
		out, err := api.CalendarEvents(ctx, p.From, p.To)
		if err != nil {
			return nil, err
		}
		if out == nil {
			out = []Fact{}
		}
		return marshalResult(out), nil

	case MethodRecentNudges:
		var p nReq
		if err := unmarshalParams(req.Params, &p); err != nil {
			return nil, err
		}
		out, err := api.RecentNudges(ctx, p.N)
		if err != nil {
			return nil, err
		}
		if out == nil {
			out = []Nudge{}
		}
		return marshalResult(out), nil

	case MethodWriteNote:
		var p writeNoteReq
		if err := unmarshalParams(req.Params, &p); err != nil {
			return nil, err
		}
		id, err := api.WriteNote(ctx, p.Ts, p.Text, p.Embedding, p.Source)
		return marshalResult(idResp{ID: id}), err

	case MethodQueryNotes:
		var p queryNotesReq
		if err := unmarshalParams(req.Params, &p); err != nil {
			return nil, err
		}
		out, err := api.QueryNotes(ctx, p.Embedding, p.K)
		if err != nil {
			return nil, err
		}
		if out == nil {
			out = []Note{}
		}
		return marshalResult(out), nil

	case MethodRecentNotes:
		var p nReq
		if err := unmarshalParams(req.Params, &p); err != nil {
			return nil, err
		}
		out, err := api.RecentNotes(ctx, p.N)
		if err != nil {
			return nil, err
		}
		if out == nil {
			out = []Note{}
		}
		return marshalResult(out), nil

	case MethodProposeTool:
		var p proposeToolReq
		if err := unmarshalParams(req.Params, &p); err != nil {
			return nil, err
		}
		ok, err := api.ProposeTool(ctx, p.Name, p.Utterance, p.Scope, p.Ts)
		if err != nil {
			return nil, err
		}
		return marshalResult(proposeToolResp{Proposed: ok}), nil

	case MethodEnableTool:
		var p enableToolReq
		if err := unmarshalParams(req.Params, &p); err != nil {
			return nil, err
		}
		return marshalResult(nil), api.EnableTool(ctx, p.Name, p.Cmd, p.Destructive, p.Scope, p.Ts)

	case MethodDisableTool:
		var p disableToolReq
		if err := unmarshalParams(req.Params, &p); err != nil {
			return nil, err
		}
		return marshalResult(nil), api.DisableTool(ctx, p.Name)

	case MethodLookupTool:
		var p lookupToolReq
		if err := unmarshalParams(req.Params, &p); err != nil {
			return nil, err
		}
		t, err := api.LookupTool(ctx, p.Name)
		if err != nil {
			return nil, err
		}
		return marshalResult(t), nil

	case MethodListTools:
		var p listToolsReq
		if err := unmarshalParams(req.Params, &p); err != nil {
			return nil, err
		}
		out, err := api.ListTools(ctx, p.Status)
		if err != nil {
			return nil, err
		}
		if out == nil {
			out = []Tool{}
		}
		return marshalResult(listToolsResp{Tools: out}), nil

	case MethodDeleteTool:
		var p disableToolReq
		if err := unmarshalParams(req.Params, &p); err != nil {
			return nil, err
		}
		return marshalResult(nil), api.DeleteTool(ctx, p.Name)

	case MethodListProposedRoutines:
		out, err := api.ListProposedRoutines(ctx)
		if err != nil {
			return nil, err
		}
		if out == nil {
			out = []ProposedRoutine{}
		}
		return marshalResult(listProposedRoutinesResp{Routines: out}), nil

	case MethodDismissProposedRoutine:
		var p dismissProposedRoutineReq
		if err := unmarshalParams(req.Params, &p); err != nil {
			return nil, err
		}
		return marshalResult(nil), api.DismissProposedRoutine(ctx, p.ID)

	case MethodRevertFact:
		var p struct {
			Key string `json:"key"`
		}
		if err := unmarshalParams(req.Params, &p); err != nil {
			return nil, err
		}
		newID, err := api.RevertFact(ctx, p.Key)
		if err != nil {
			return nil, err
		}
		return marshalResult(map[string]int64{"new_id": newID}), nil

	case MethodChat:
		var p chatReq
		if err := unmarshalParams(req.Params, &p); err != nil {
			return nil, err
		}
		reply, err := api.Chat(ctx, p.Text)
		if err != nil {
			return nil, err
		}
		return marshalResult(chatResp{Reply: reply}), nil

	case MethodTickTrace:
		t, err := api.TickTrace(ctx)
		if err != nil {
			return nil, err
		}
		return marshalResult(t), nil

	case MethodAssertStepUp:
		if s.StepUp != nil {
			return marshalResult(nil), s.StepUp(ctx)
		}
		return nil, fmt.Errorf("%w: %s", ErrUnknownMethod, req.Method)

	case MethodStoreEncryptionKey:
		if s.WrapKeyFn != nil {
			var p storeEncryptionKeyReq
			if err := unmarshalParams(req.Params, &p); err != nil {
				return nil, err
			}
			return marshalResult(nil), s.WrapKeyFn(ctx, p.PublicKey)
		}
		return nil, fmt.Errorf("%w: %s", ErrUnknownMethod, req.Method)

	case MethodUnlock:
		if s.UnlockFn != nil {
			var p unlockReq
			if err := unmarshalParams(req.Params, &p); err != nil {
				return nil, err
			}
			return marshalResult(nil), s.UnlockFn(ctx, p.PublicKey)
		}
		return nil, fmt.Errorf("%w: %s", ErrUnknownMethod, req.Method)

	default:
		return nil, fmt.Errorf("%w: %s", ErrUnknownMethod, req.Method)
	}
}

func unmarshalParams(raw json.RawMessage, v any) error {
	if len(raw) == 0 {
		raw = []byte("null")
	}
	if err := json.Unmarshal(raw, v); err != nil {
		return fmt.Errorf("%w: %v", ErrBadParams, err)
	}
	return nil
}

func marshalResult(v any) json.RawMessage {
	if v == nil {
		return json.RawMessage("null")
	}
	b, _ := json.Marshal(v)
	return b
}

// Close stops accepting and waits for in-flight connections to drain. The
// socket file is removed so a restart can rebind cleanly. Idempotent.
func (s *Server) Close() error {
	select {
	case <-s.done:
		return nil
	default:
		close(s.done)
	}
	err := s.ln.Close()
	// Under accept lock: after the listener closes, no new Accept can complete,
	// so no new wg.Add will be called. The Wait is safe to observe the wg
	// counter because any in-flight Accept that already got a conn either
	// already called wg.Add (before releasing the lock) or will see the closed
	// listener error and not call wg.Add at all.
	s.accept.Lock()
	s.wg.Wait()
	s.accept.Unlock()
	_ = os.Remove(s.path)
	return err
}

// Path returns the filesystem path of the listening socket.
func (s *Server) Path() string { return s.path }

// SetAPI atomically replaces the CoreAPI the server dispatches to. Used by
// the daemon's unlock path: in locked mode a dummy API returns errors for all
// store methods; after unlock, the real store API is swapped in. Safe to call
// while the server is serving (dispatch loads api once per request via atomic).
func (s *Server) SetAPI(api CoreAPI) { s.api.Store(api) }

func parentDir(p string) string {
	if i := lastIndexByte(p, '/'); i >= 0 {
		if i == 0 {
			return "/"
		}
		return p[:i]
	}
	return "."
}

func lastIndexByte(s string, b byte) int {
	for i := len(s) - 1; i >= 0; i-- {
		if s[i] == b {
			return i
		}
	}
	return -1
}

// peerCaller — read SO_PEERCRED off a unix conn to identify the connecting
// process. Returns ok=false on a non-unix conn or a platform without
// SO_PEERCRED; the caller then proceeds without a Caller (the socket perms
// already proved same-user). Linux only today; on other platforms this floors
// to "unknown caller" rather than failing — the wire still works.
func peerCaller(c net.Conn) (Caller, bool) {
	uc, ok := c.(*net.UnixConn)
	if !ok {
		return Caller{}, false
	}
	raw, err := uc.SyscallConn()
	if err != nil {
		return Caller{}, false
	}
	var cred *unix.Ucred
	ctrlErr := raw.Control(func(fd uintptr) {
		cred, err = unix.GetsockoptUcred(int(fd), unix.SOL_SOCKET, unix.SO_PEERCRED)
	})
	if ctrlErr != nil || err != nil || cred == nil {
		return Caller{}, false
	}
	return Caller{Uid: int32(cred.Uid), Pid: int32(cred.Pid)}, true
}