From 941bdcafad2ed0f2e1c590f2c79acb3a4ddb1ebe Mon Sep 17 00:00:00 2001
From: Conner Fromknecht <conner@mit.edu>
Date: Tue, 24 Apr 2018 18:09:51 -0700
Subject: [PATCH] htlcswitch/hodl/flags: adds flags signifying switch
 breakpoints

---
 htlcswitch/hodl/flags.go | 111 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 111 insertions(+)
 create mode 100644 htlcswitch/hodl/flags.go

diff --git a/htlcswitch/hodl/flags.go b/htlcswitch/hodl/flags.go
new file mode 100644
index 000000000..688999f3c
--- /dev/null
+++ b/htlcswitch/hodl/flags.go
@@ -0,0 +1,111 @@
+package hodl
+
+import "fmt"
+
+// MaskNone represents the empty Mask, in which no breakpoints are
+// active.
+const MaskNone = Mask(0)
+
+type (
+	// Flag represents a single breakpoint where an HTLC should be dropped
+	// during forwarding. Flags can be composed into a Mask to express more
+	// complex combinations.
+	Flag uint32
+
+	// Mask is a bitvector combining multiple Flags that can be queried to
+	// see which breakpoints are active.
+	Mask uint32
+)
+
+const (
+	// ExitSettle drops an incoming ADD for which we are the exit node,
+	// before processing in the link.
+	ExitSettle Flag = 1 << iota
+
+	// AddIncoming drops an incoming ADD before processing if we are not
+	// the exit node.
+	AddIncoming
+
+	// SettleIncoming drops an incoming SETTLE before processing if we
+	// are not the exit node.
+	SettleIncoming
+
+	// FailIncoming drops an incoming FAIL before processing if we are
+	// not the exit node.
+	FailIncoming
+
+	// TODO(conner): add  modes for switch breakpoints
+
+	// AddOutgoing drops an outgoing ADD before it is added to the
+	// in-memory commitment state of the link.
+	AddOutgoing
+
+	// SettleOutgoing drops an SETTLE before it is added to the
+	// in-memory commitment state of the link.
+	SettleOutgoing
+
+	// FailOutgoing drops an outgoing FAIL before is is added to the
+	// in-memory commitment state of the link.
+	FailOutgoing
+
+	// Commit drops all HTLC after any outgoing circuits have been
+	// opened, but before the in-memory commitment state is persisted.
+	Commit
+)
+
+// String returns a human-readable identifier for a given Flag.
+func (f Flag) String() string {
+	switch f {
+	case ExitSettle:
+		return "ExitSettle"
+	case AddIncoming:
+		return "AddIncoming"
+	case SettleIncoming:
+		return "SettleIncoming"
+	case FailIncoming:
+		return "FailIncoming"
+	case AddOutgoing:
+		return "AddOutgoing"
+	case SettleOutgoing:
+		return "SettleOutgoing"
+	case FailOutgoing:
+		return "FailOutgoing"
+	case Commit:
+		return "Commit"
+	default:
+		return "UnknownHodlFlag"
+	}
+}
+
+// Warning generates a warning message to log if a particular breakpoint is
+// triggered during execution.
+func (f Flag) Warning() string {
+	var msg string
+	switch f {
+	case ExitSettle:
+		msg = "will not attempt to settle ADD with sender"
+	case AddIncoming:
+		msg = "will not attempt to forward ADD to switch"
+	case SettleIncoming:
+		msg = "will not attempt to forward SETTLE to switch"
+	case FailIncoming:
+		msg = "will not attempt to forward FAIL to switch"
+	case AddOutgoing:
+		msg = "will not update channel state with downstream ADD"
+	case SettleOutgoing:
+		msg = "will not update channel state with downstream SETTLE"
+	case FailOutgoing:
+		msg = "will not update channel state with downstream FAIL"
+	case Commit:
+		msg = "will not commit pending channel updates"
+	default:
+		msg = "incorrect hodl flag usage"
+	}
+
+	return fmt.Sprintf("%s mode enabled -- %s", f, msg)
+}
+
+// Mask returns the Mask consisting solely of this Flag.
+func (f Flag) Mask() Mask {
+	return Mask(f)
+}