package agent

import (
	"path/filepath"
	"sync"
)

// Recovery and result-journal instances share a root but are constructed by
// different call/recovery paths. Locks exist only while a path is in use; they
// are not a permanent identity history and do not serialize independent files.
type privateStateLock struct {
	mu    sync.Mutex
	users int
}

var privateStateLocks = struct {
	sync.Mutex
	paths map[string]*privateStateLock
}{paths: make(map[string]*privateStateLock)}

func holdPrivateState(path string) (func(), error) {
	key, err := filepath.Abs(path)
	if err != nil {
		return nil, err
	}
	privateStateLocks.Lock()
	lock := privateStateLocks.paths[key]
	if lock == nil {
		lock = &privateStateLock{}
		privateStateLocks.paths[key] = lock
	}
	lock.users++
	privateStateLocks.Unlock()
	lock.mu.Lock()
	return func() {
		lock.mu.Unlock()
		privateStateLocks.Lock()
		lock.users--
		if lock.users == 0 {
			delete(privateStateLocks.paths, key)
		}
		privateStateLocks.Unlock()
	}, nil
}