(BEDS-561) adapt return struct

backend/go.mod

@@ -64,7 +64,7 @@ require (
 	github.com/prysmaticlabs/go-ssz v0.0.0-20210121151755-f6208871c388
 	github.com/rocket-pool/rocketpool-go v1.8.3-0.20240618173422-783b8668f5b4
 	github.com/rocket-pool/smartnode v1.13.6
-	github.com/shopspring/decimal v1.3.1
+	github.com/shopspring/decimal v1.4.0
 	github.com/sirupsen/logrus v1.9.3
 	github.com/stretchr/testify v1.9.0
 	github.com/syndtr/goleveldb v1.0.1-0.20220721030215-126854af5e6d

backend/go.sum

@@ -873,6 +873,8 @@ github.com/shopspring/decimal v0.0.0-20180709203117-cd690d0c9e24/go.mod h1:M+9Nz
 github.com/shopspring/decimal v1.2.0/go.mod h1:DKyhrW/HYNuLGql+MJL6WCR6knT2jwCFRcu2hWCYk4o=
 github.com/shopspring/decimal v1.3.1 h1:2Usl1nmF/WZucqkFZhnfFYxxxu8LG21F6nPQBE5gKV8=
 github.com/shopspring/decimal v1.3.1/go.mod h1:DKyhrW/HYNuLGql+MJL6WCR6knT2jwCFRcu2hWCYk4o=
+github.com/shopspring/decimal v1.4.0 h1:bxl37RwXBklmTi0C79JfXCEBD1cqqHt0bbgBAGFp81k=
+github.com/shopspring/decimal v1.4.0/go.mod h1:gawqmDU56v4yIKSwfBSFip1HdCCXN8/+DMd9qYNcwME=
 github.com/shurcooL/sanitized_anchor_name v1.0.0/go.mod h1:1NzhyTcUVG4SuEtjjoZeVRXNmyL/1OwPU0+IJeTBvfc=
 github.com/sirupsen/logrus v1.4.1/go.mod h1:ni0Sbl8bgC9z8RoU9G6nDWqqs/fq4eDPysMBDgk/93Q=
 github.com/sirupsen/logrus v1.4.2/go.mod h1:tLMulIdttU9McNUspp0xgXVQah82FyeX6MwdIuYE2rE=

backend/pkg/api/data_access/header.go

@@ -1,9 +1,15 @@
 package dataaccess
 
 import (
+	"context"
+	"database/sql"
+	"fmt"
+
 	t "github.com/gobitfly/beaconchain/pkg/api/types"
 	"github.com/gobitfly/beaconchain/pkg/commons/cache"
+	"github.com/gobitfly/beaconchain/pkg/commons/log"
 	"github.com/gobitfly/beaconchain/pkg/commons/price"
+	"github.com/gobitfly/beaconchain/pkg/commons/utils"
 )
 
 func (d *DataAccessService) GetLatestSlot() (uint64, error) {
@@ -26,6 +32,43 @@ func (d *DataAccessService) GetBlockHeightAt(slot uint64) (uint64, error) {
 	return d.dummy.GetBlockHeightAt(slot)
 }
 
+// returns the block number of the latest existing block at or before the given slot
+func (d *DataAccessService) GetLatestBlockHeightForSlot(ctx context.Context, slot uint64) (uint64, error) {
+	query := `SELECT MAX(exec_block_number) FROM blocks WHERE slot <= $1`
+	res := uint64(0)
+	err := d.alloyReader.GetContext(ctx, &res, query, slot)
+	if err != nil {
+		if err == sql.ErrNoRows {
+			log.Warnf("no EL block found at or before slot %d", slot)
+			return 0, nil
+		}
+		return 0, fmt.Errorf("failed to get latest existing block height at or before slot %d: %w", slot, err)
+	}
+	return res, nil
+}
+
+func (d *DataAccessService) GetLatestBlockHeightsForEpoch(ctx context.Context, epoch uint64) ([]uint64, error) {
+	// use 2 epochs as safety margin
+	query := `
+	WITH recent_blocks AS (
+		SELECT slot, exec_block_number
+		FROM blocks
+		WHERE slot < $1
+		ORDER BY slot DESC
+		LIMIT $2 * 2
+	)
+	SELECT MAX(exec_block_number) OVER (ORDER BY slot) AS block
+	FROM recent_blocks
+	ORDER BY slot DESC
+	LIMIT $2`
+	res := []uint64{}
+	err := d.alloyReader.SelectContext(ctx, &res, query, (epoch+1)*utils.Config.Chain.ClConfig.SlotsPerEpoch, utils.Config.Chain.ClConfig.SlotsPerEpoch)
+	if err != nil {
+		return nil, fmt.Errorf("failed to get latest existing block heights for slots in epoch %d: %w", epoch, err)
+	}
+	return res, nil
+}
+
 func (d *DataAccessService) GetLatestExchangeRates() ([]t.EthConversionRate, error) {
 	result := []t.EthConversionRate{}