fix(l1): always use fullsync if db had data (#5196)

**Motivation**

When the db had data, we should fullsync, not override the user's data

**Description**

- Changes the fullsync option instead of snap to be any number instead
of `MIN_FULL_BLOCKS`

Author: fedacking

crates/networking/p2p/sync.rs

@@ -47,7 +47,7 @@ use tokio_util::sync::CancellationToken;
 use tracing::{debug, error, info, warn};
 
 /// The minimum amount of blocks from the head that we want to full sync during a snap sync
-const MIN_FULL_BLOCKS: usize = 64;
+const MIN_FULL_BLOCKS: u64 = 10_000;
 /// Amount of blocks to execute in a single batch during FullSync
 const EXECUTE_BATCH_SIZE_DEFAULT: usize = 1024;
 /// Amount of seconds between blocks
@@ -288,17 +288,16 @@ impl Syncer {
             current_head = last_block_hash;
             current_head_number = last_block_number;
 
-            // If the sync head is less than 64 blocks away from our current head switch to full-sync
-            if sync_head_found {
-                let latest_block_number = store.get_latest_block_number().await?;
-                if last_block_number.saturating_sub(latest_block_number) < MIN_FULL_BLOCKS as u64 {
-                    // Too few blocks for a snap sync, switching to full sync
-                    debug!(
-                        "Sync head is less than {MIN_FULL_BLOCKS} blocks away, switching to FullSync"
-                    );
-                    self.snap_enabled.store(false, Ordering::Relaxed);
-                    return self.sync_cycle_full(sync_head, store.clone()).await;
-                }
+            // If the sync head is not 0 we search to fullsync
+            let head_found = sync_head_found && store.get_latest_block_number().await? > 0;
+            // Or the head is very close to 0
+            let head_close_to_0 = last_block_number < MIN_FULL_BLOCKS;
+
+            if head_found || head_close_to_0 {
+                // Too few blocks for a snap sync, switching to full sync
+                info!("Sync head is found, switching to FullSync");
+                self.snap_enabled.store(false, Ordering::Relaxed);
+                return self.sync_cycle_full(sync_head, store.clone()).await;
             }
 
             // Discard the first header as we already have it

crates/networking/rpc/engine/fork_choice.rs

@@ -4,7 +4,6 @@ use ethrex_blockchain::{
     payload::{BuildPayloadArgs, create_payload},
 };
 use ethrex_common::types::{BlockHeader, ELASTICITY_MULTIPLIER};
-use ethrex_p2p::sync::SyncMode;
 use serde_json::Value;
 use tracing::{info, warn};
 
@@ -215,6 +214,7 @@ async fn handle_forkchoice(
         ));
     }
 
+    /*   Revert #4985
     if context.syncer.sync_mode() == SyncMode::Snap {
         // Don't trigger a sync if the block is already canonical
         if context
@@ -229,7 +229,7 @@ async fn handle_forkchoice(
                 .sync_to_head(fork_choice_state.head_block_hash);
             return Ok((None, PayloadStatus::syncing().into()));
         }
-    }
+    } */
 
     match apply_fork_choice(
         &context.storage,