Improve bound and cache update checks

cmd/stellar-rpc/internal/db/cursor.go

@@ -130,8 +130,8 @@ var (
 	//nolint:gochecknoglobals
 	MaxCursor = Cursor{
 		Ledger: math.MaxInt32,
-		Tx:     math.MaxInt32,
-		Op:     math.MaxInt32,
+		Tx:     toid.TransactionMask,
+		Op:     toid.OperationMask,
 		Event:  math.MaxUint32,
 	}
 )

cmd/stellar-rpc/internal/db/cursor_test.go

@@ -108,3 +108,10 @@ func TestCursorCmp(t *testing.T) {
 		}
 	}
 }
+
+func TestMaxCursor(t *testing.T) {
+	str := MaxCursor.String()
+	cursor, err := ParseCursor(str)
+	require.NoError(t, err)
+	assert.Equal(t, MaxCursor, cursor)
+}

cmd/stellar-rpc/internal/db/db.go

@@ -156,8 +156,8 @@ func getLatestLedgerSequence(ctx context.Context, ledgerReader LedgerReader, cac
 	// Add missing ledger sequence and close time to the top cache.
 	// Otherwise, the write-through cache won't get updated until the first ingestion commit
 	cache.Lock()
-	if cache.latestLedgerSeq == 0 {
-		// Only update the cache if the value is missing (0), otherwise
+	if cache.latestLedgerSeq == 0 || cache.latestLedgerSeq < ledgerRange.LastLedger.Sequence {
+		// Only update the cache if the value is missing or lower, otherwise
 		// we may end up overwriting the entry with an older version
 		cache.latestLedgerSeq = ledgerRange.LastLedger.Sequence
 		cache.latestLedgerCloseTime = ledgerRange.LastLedger.CloseTime

cmd/stellar-rpc/internal/db/ledger.go

@@ -3,6 +3,7 @@ package db
 import (
 	"context"
 	"database/sql"
+	"errors"
 	"fmt"
 
 	sq "github.com/Masterminds/squirrel"
@@ -63,6 +64,9 @@ func (l ledgerReaderTx) GetLedgerRange(ctx context.Context) (ledgerbucketwindow.
 func (l ledgerReaderTx) BatchGetLedgers(ctx context.Context, sequence uint32,
 	batchSize uint,
 ) ([]xdr.LedgerCloseMeta, error) {
+	if batchSize < 1 {
+		return nil, errors.New("batch size must be greater than zero")
+	}
 	sql := sq.Select("meta").
 		From(ledgerCloseMetaTableName).
 		Where(sq.And{

cmd/stellar-rpc/internal/methods/get_events.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
-	"math"
 	"strings"
 	"time"
 
@@ -124,10 +123,16 @@ func (g *GetEventsRequest) Valid(maxLimit uint) error {
 		if g.StartLedger != 0 || g.EndLedger != 0 {
 			return errors.New("ledger ranges and cursor cannot both be set")
 		}
-	} else if g.StartLedger <= 0 {
+	}
+
+	if g.StartLedger <= 0 {
 		return errors.New("startLedger must be positive")
 	}
 
+	if g.EndLedger < g.StartLedger {
+		return errors.New("startLedger must be >= endLedger")
+	}
+
 	if g.Pagination != nil && g.Pagination.Limit > maxLimit {
 		return fmt.Errorf("limit must not exceed %d", maxLimit)
 	}
@@ -524,7 +529,9 @@ func (h eventsRPCHandler) getEvents(ctx context.Context, request GetEventsReques
 		// cursor represents end of the search window if events does not reach limit
 		// here endLedger is always exclusive when fetching events
 		// so search window is max Cursor value with endLedger - 1
-		cursor = db.Cursor{Ledger: endLedger - 1, Tx: math.MaxUint32, Event: math.MaxUint32 - 1}.String()
+		maxCursor := db.MaxCursor
+		maxCursor.Event = endLedger - 1
+		cursor = maxCursor.String()
 	}
 
 	return GetEventsResponse{

cmd/stellar-rpc/internal/methods/get_transactions.go

@@ -40,7 +40,8 @@ func (req GetTransactionsRequest) isValid(maxLimit uint, ledgerRange ledgerbucke
 		if req.StartLedger != 0 {
 			return errors.New("startLedger and cursor cannot both be set")
 		}
-	} else if req.StartLedger < ledgerRange.FirstLedger.Sequence || req.StartLedger > ledgerRange.LastLedger.Sequence {
+	}
+	if req.StartLedger < ledgerRange.FirstLedger.Sequence || req.StartLedger > ledgerRange.LastLedger.Sequence {
 		return fmt.Errorf(
 			"start ledger must be between the oldest ledger: %d and the latest ledger: %d for this rpc instance",
 			ledgerRange.FirstLedger.Sequence,