lock.gno

 1package arena
 2
 3import (
 4	"chain/runtime"
 5	"strconv"
 6	"time"
 7)
 8
 9// guard binds the session that signed the transaction to match id, held in m, saving the
10// caller's record only when its locks change.
11func guard(fromUser bool, caller address, m record, id int) {
12	session, expires, ok := signingSession(fromUser)
13	if !ok {
14		return
15	}
16	if caller != m.challenger && caller != m.acceptor {
17		panic("not a player")
18	}
19	p := loadPlayer(caller)
20	if p.lock(session, expires, id, false, time.Now().Unix()) {
21		savePlayer(caller, p)
22	}
23}
24
25// join adds match id to the caller's record and binds the session that signed the
26// transaction to it, refused when that session is bound to a match already.
27func join(fromUser bool, caller address, id int) {
28	p := loadPlayer(caller)
29	if session, expires, ok := signingSession(fromUser); ok {
30		p.lock(session, expires, id, true, time.Now().Unix())
31	}
32	p.add(id)
33	savePlayer(caller, p)
34}
35
36// signingSession returns the signing session key and its expiry when fromUser: a session
37// signs the whole transaction, so a call through another realm is left unchecked.
38func signingSession(fromUser bool) (address, int64, bool) {
39	if !fromUser {
40		return "", 0, false
41	}
42	session, expires, _, ok := runtime.GetSessionInfo()
43	return session, expires, ok
44}
45
46// lock binds session to match id in p's locks, panicking when it is refused, and reports
47// whether the locks changed.
48func (p *playerRecord) lock(session address, expires int64, id int, opening bool, now int64) bool {
49	locks, changed, refusal := lockSession(p.locks, session, expires, id, opening, now)
50	if refusal != "" {
51		panic(refusal)
52	}
53	p.locks = locks
54	return changed
55}
56
57// lockSession binds session to match id, refused when bound to another, or any when opening.
58// It drops expired locks and any lock its key holds under another expiry (Unix seconds, 0 never).
59func lockSession(locks []sessionLock, session address, expires int64, id int, opening bool, now int64) (kept []sessionLock, changed bool, refusal string) {
60	for _, l := range locks {
61		expired := l.expires != 0 && l.expires <= now
62		stale := l.session == session && l.expires != expires
63		if !expired && !stale {
64			kept = append(kept, l)
65		}
66	}
67	changed = len(kept) != len(locks)
68	for _, l := range kept {
69		if l.session != session {
70			continue
71		}
72		if opening || l.id != id {
73			return kept, changed, "session locked to match " + strconv.Itoa(l.id)
74		}
75		return kept, changed, ""
76	}
77	return append(kept, sessionLock{session: session, id: id, expires: expires}), true, ""
78}