// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
// SPDX-License-Identifier: MIT

package nfs4server

import (
	"sync"
	"time"

	"sourcedock.dev/petrbalvin/nfs/internal/nfs4"
)

// A grace is the reclaim window of one handler: it opens when the handler
// starts and closes after the configured period. The server recovers no
// state across restarts, so a fresh window means every reclaim attempt
// inside it is answered, and every attempt after it is NFS4ERR_NO_GRACE.
type grace struct {
	mu   sync.Mutex
	end  time.Time
	done map[uint64]bool
}

func newGrace(period time.Duration) *grace {
	return &grace{end: time.Now().Add(period), done: make(map[uint64]bool)}
}

// active reports whether the reclaim window still runs.
func (g *grace) active(now time.Time) bool {
	g.mu.Lock()
	defer g.mu.Unlock()
	return now.Before(g.end)
}

// reclaimOKFor reports whether the client may reclaim: inside the
// window and without an earlier RECLAIM_COMPLETE. The status names the
// refusal: NO_GRACE for a closed window, COMPLETE_ALREADY for a client
// that announced it was done.
func (g *grace) reclaimOKFor(clientid uint64, now time.Time) (bool, uint32) {
	g.mu.Lock()
	defer g.mu.Unlock()
	if !now.Before(g.end) {
		return false, nfs4.ErrNoGrace
	}
	if g.done[clientid] {
		return false, nfs4.ErrCompleteAlready
	}
	return true, 0
}

// complete records the client's RECLAIM_COMPLETE and reports whether this
// was the first announcement.
func (g *grace) complete(clientid uint64, now time.Time) bool {
	g.mu.Lock()
	defer g.mu.Unlock()
	if g.done[clientid] {
		return false
	}
	g.done[clientid] = true
	return true
}