get root height of a flow sporked network through binary search

rootheight.go

package main

import (
	"fmt"

	flowclient "github.com/onflow/flow-go-sdk/client"
	"google.golang.org/grpc"
)

import (
	"context"
)

func panicIfErr(err error) {
	if err != nil {
		panic(err)
	}
}

func main() {
	client, err := flowclient.New("access-001.devnet16.nodes.onflow.org:9000", grpc.WithInsecure())
	panicIfErr(err)
	err = client.Ping(context.Background())
	panicIfErr(err)

	latestBlock, err := client.GetLatestBlockHeader(context.Background(), true)
	panicIfErr(err)

	min := uint64(0)
	max := latestBlock.Height
	for min < max-1 {
		mid := (min + max) / 2
		_, err := client.GetBlockByHeight(context.Background(), mid)
		if err != nil {
			// not exist, go for mid - max
			min = mid
			continue
		}
		// exists, go for min - mid
		max = mid
	}
	fmt.Printf("root height: %d\n", max)
}