vsp: Recalculate ticket live/expiry heights.

Previously the live & expiry heights were only being set once upon
feePayment initialization, which meant that an unmined ticket added to
the VSP client would have heights set to zero forever.

With this change, if either of the values are found to be zero, we check
if the ticket has been mined yet and the heights are recalculated to
their correct values if so.

internal/vsp/feepayment.go

@@ -137,6 +137,47 @@ func parseTicket(ticket *wire.MsgTx, params *chaincfg.Params) (
 	return
 }
 
+// calcHeights checks if the ticket has been mined, and if so, sets the live
+// height and expiry height fields. Should be called with mutex already held.
+func (fp *feePayment) calcHeights() {
+	_, minedHeight, err := fp.client.wallet.TxBlock(fp.ctx, &fp.ticketHash)
+	if err != nil {
+		// This is not expected to ever error, as the ticket has already been
+		// fetched from the wallet at least one before this point is reached.
+		fp.client.log.Errorf("Failed to query block which mines ticket: %v", err)
+		return
+	}
+
+	if minedHeight < 2 {
+		return
+	}
+
+	// Note the off-by-one; this is correct. Tickets become live one block after
+	// the params would indicate.
+	fp.ticketLive = minedHeight + int32(fp.params.TicketMaturity) + 1
+	fp.ticketExpires = fp.ticketLive + int32(fp.params.TicketExpiry)
+}
+
+// expiryHeight returns the height at which the ticket expires. Returns zero if
+// the block is not yet mined. Should be called with mutex already held.
+func (fp *feePayment) expiryHeight() int32 {
+	if fp.ticketExpires == 0 {
+		fp.calcHeights()
+	}
+
+	return fp.ticketExpires
+}
+
+// liveHeight returns the height at which the ticket becomes live. Returns zero
+// if the block is not yet mined. Should be called with mutex already held.
+func (fp *feePayment) liveHeight() int32 {
+	if fp.ticketLive == 0 {
+		fp.calcHeights()
+	}
+
+	return fp.ticketLive
+}
+
 func (fp *feePayment) ticketSpent() bool {
 	ctx := fp.ctx
 	ticketOut := wire.OutPoint{Hash: fp.ticketHash, Index: 0, Tree: 1}
@@ -150,7 +191,7 @@ func (fp *feePayment) ticketExpired() bool {
 	_, tipHeight := w.MainChainTip(ctx)
 
 	fp.mu.Lock()
-	expires := fp.ticketExpires
+	expires := fp.expiryHeight()
 	fp.mu.Unlock()
 
 	return expires > 0 && tipHeight >= expires
@@ -232,20 +273,6 @@ func (c *Client) feePayment(ctx context.Context, ticketHash *chainhash.Hash, pai
 		return nil
 	}
 
-	_, ticketHeight, err := w.TxBlock(ctx, ticketHash)
-	if err != nil {
-		// This is not expected to ever error, as the ticket was fetched
-		// from the wallet in the above call.
-		fp.client.log.Errorf("failed to query block which mines ticket: %v", err)
-		return nil
-	}
-	if ticketHeight >= 2 {
-		// Note the off-by-one; this is correct.  Tickets become live
-		// one block after the params would indicate.
-		fp.ticketLive = ticketHeight + int32(c.params.TicketMaturity) + 1
-		fp.ticketExpires = fp.ticketLive + int32(c.params.TicketExpiry)
-	}
-
 	fp.votingAddr, fp.commitmentAddr, err = parseTicket(ticket, c.params)
 	if err != nil {
 		fp.client.log.Errorf("%v is not a ticket: %v", ticketHash, err)
@@ -326,8 +353,8 @@ func (fp *feePayment) next() time.Duration {
 	_, tipHeight := w.MainChainTip(fp.ctx)
 
 	fp.mu.Lock()
-	ticketLive := fp.ticketLive
-	ticketExpires := fp.ticketExpires
+	ticketLive := fp.liveHeight()
+	ticketExpires := fp.expiryHeight()
 	fp.mu.Unlock()
 
 	var jitter time.Duration