package calls

import (
	"crypto/sha256"
	"encoding/hex"
	"testing"
)

// Review W-4: the subject was bound into the hub session key in the
// Task 4 fix round with a reason — "the key then cannot survive the
// person it belongs to" — and nothing tested it. Dropping the subject
// left the whole suite green.
//
// A sign-out-and-in test over HTTP does not gate this: re-signing-in
// hands the browser a new cookie value, so the key would change with or
// without the subject in the hash. What the claim is actually about is
// the same cookie value under a different person, which is why this is
// a test of the derivation rather than of a request.
func TestTheHubSessionKeyBindsTheSubjectTheSaltAndTheCookie(t *testing.T) {
	const (
		salt   = "boot-salt"
		who    = "person@example.com"
		cookie = "a-session-cookie-value"
	)
	base := hubSessionKey(salt, who, cookie)

	// Two tabs of one browser: the same key, which is what one peer per
	// room and its takeover need (§4.2).
	if again := hubSessionKey(salt, who, cookie); again != base {
		t.Fatal("the same session did not derive the same key")
	}

	for _, c := range []struct {
		what              string
		salt, who, cookie string
		why               string
	}{
		{"subject", salt, "someone.else@example.com", cookie,
			"a cookie value reused under another person would inherit the room"},
		{"salt", "another-boot", who, cookie,
			"the key would still name a participation from before a restart"},
		{"cookie", salt, who, "another-session-cookie",
			"two browsers of one person would collide, and §4.4 allows four streams per person"},
	} {
		if got := hubSessionKey(c.salt, c.who, c.cookie); got == base {
			t.Fatalf("changing the %s did not change the key: %s", c.what, c.why)
		}
	}

	// And the key is not a credential: it is neither the cookie value
	// nor a bare hash of it, so a hub key on its own reaches nothing.
	if base == cookie {
		t.Fatal("the key is the session cookie value")
	}
	bare := sha256.Sum256([]byte(cookie))
	if base == hex.EncodeToString(bare[:]) {
		t.Fatal("the key is an unsalted hash of the session cookie value")
	}
	if len(base) != 64 {
		t.Fatalf("the key is %d characters, want 64 hex", len(base))
	}
}