From 416ae197ad6490db03a5159349d214c484179325 Mon Sep 17 00:00:00 2001
From: Jared Wasinger <j-wasinger@hotmail.com>
Date: Mon, 6 May 2024 06:24:49 -0700
Subject: [PATCH] eth/downloader: panic if sync cycle configured with unknown
 sync mode.  remove LightSync mode definition.

---
 eth/downloader/beaconsync.go |  6 +++++-
 eth/downloader/modes.go      | 15 ++++-----------
 2 files changed, 9 insertions(+), 12 deletions(-)

diff --git a/eth/downloader/beaconsync.go b/eth/downloader/beaconsync.go
index 3ce78b046c..57c6eee40a 100644
--- a/eth/downloader/beaconsync.go
+++ b/eth/downloader/beaconsync.go
@@ -201,6 +201,8 @@ func (d *Downloader) findBeaconAncestor() (uint64, error) {
 		chainHead = d.blockchain.CurrentBlock()
 	case SnapSync:
 		chainHead = d.blockchain.CurrentSnapBlock()
+	default:
+		panic("unknown sync mode")
 	}
 	number := chainHead.Number.Uint64()
 
@@ -220,7 +222,7 @@ func (d *Downloader) findBeaconAncestor() (uint64, error) {
 	case SnapSync:
 		linked = d.blockchain.HasFastBlock(beaconTail.ParentHash, beaconTail.Number.Uint64()-1)
 	default:
-		linked = d.blockchain.HasHeader(beaconTail.ParentHash, beaconTail.Number.Uint64()-1)
+		panic("unknown sync mode")
 	}
 	if !linked {
 		// This is a programming error. The chain backfiller was called with a
@@ -254,6 +256,8 @@ func (d *Downloader) findBeaconAncestor() (uint64, error) {
 			known = d.blockchain.HasBlock(h.Hash(), n)
 		case SnapSync:
 			known = d.blockchain.HasFastBlock(h.Hash(), n)
+		default:
+			panic("unknown sync mode")
 		}
 		if !known {
 			end = check
diff --git a/eth/downloader/modes.go b/eth/downloader/modes.go
index 7de908849e..9d8e1f313c 100644
--- a/eth/downloader/modes.go
+++ b/eth/downloader/modes.go
@@ -23,13 +23,12 @@ import "fmt"
 type SyncMode uint32
 
 const (
-	FullSync  SyncMode = iota // Synchronise the entire blockchain history from full blocks
-	SnapSync                  // Download the chain and the state via compact snapshots
-	LightSync                 // Download only the headers and terminate afterwards
+	FullSync SyncMode = iota // Synchronise the entire blockchain history from full blocks
+	SnapSync                 // Download the chain and the state via compact snapshots
 )
 
 func (mode SyncMode) IsValid() bool {
-	return mode >= FullSync && mode < LightSync
+	return mode == FullSync || mode == SnapSync
 }
 
 // String implements the stringer interface.
@@ -39,8 +38,6 @@ func (mode SyncMode) String() string {
 		return "full"
 	case SnapSync:
 		return "snap"
-	case LightSync:
-		return "light"
 	default:
 		return "unknown"
 	}
@@ -52,8 +49,6 @@ func (mode SyncMode) MarshalText() ([]byte, error) {
 		return []byte("full"), nil
 	case SnapSync:
 		return []byte("snap"), nil
-	case LightSync:
-		return []byte("light"), nil
 	default:
 		return nil, fmt.Errorf("unknown sync mode %d", mode)
 	}
@@ -65,10 +60,8 @@ func (mode *SyncMode) UnmarshalText(text []byte) error {
 		*mode = FullSync
 	case "snap":
 		*mode = SnapSync
-	case "light":
-		*mode = LightSync
 	default:
-		return fmt.Errorf(`unknown sync mode %q, want "full", "snap" or "light"`, text)
+		return fmt.Errorf(`unknown sync mode %q, want "full" or "snap"`, text)
 	}
 	return nil
 }