Golang : Get final balance from bit coin address example



Tags : golang bit-coin btc blockchain final-balance

Here is an example of how to query blockchain.info to get the final balance(amount) with a given bitcoin transaction address. Some e-commerce merchants start to accept bitcoin instead of fiat money and this application can be useful in verifying the amount received before issuing a receipt and sending out the goods.

Basically what this program below does is to get the final balance of a transaction with the given bitcoin address. You can incorporate this code below into your e-commerce application to check for the bitcoin payment.

NOTE: The only known weakness in this program is that it relies on the HTML id final_balance when parsing the HTML nodes to retrieve the BTC amount. IF the id final_balance is removed from blockchain.info website, this program will break.

Here you go!


 package main

 import (
 "fmt"
 "golang.org/x/net/html"
 "io/ioutil"
 "net/http"
 "os"
 "strings"
 )

 func Get(httpClient *http.Client, url string) (resp *http.Response, err error) {
 req, err := http.NewRequest("GET", url, nil)
 resp, err = httpClient.Do(req)
 return
 }

 func GetHtmlBody(httpClient *http.Client, url string) (string, error) {
 response, err := Get(httpClient, url)
 defer response.Body.Close()
 htmlBody, err := ioutil.ReadAll(response.Body)
 body := string(htmlBody)
 return body, err
 }

 func main() {
 if len(os.Args) != 2 {
 fmt.Printf("Usage : %s <bitcoin transaction address>\n", os.Args[0])
 os.Exit(0)
 }

 // randomly pick one or two addresses from https://blockchain.info/blocks
 //bitcoinAddress := "152f1muMCNa7goXYhYAQC61hxEgGacmncB"
 bitcoinAddress := os.Args[1]

 fmt.Println("Querying Bitcoin address : ", bitcoinAddress)

 if bitcoinAddress == "" {
 fmt.Println("Bitcoin address cannot be empty!")
 os.Exit(0)
 }

 client := &http.Client{}
 body, err := GetHtmlBody(client, "https://blockchain.info/address/"+bitcoinAddress)
 if err != nil {
 fmt.Println(err)
 }
 htmlBody := string(body)

 // adapted from https://godoc.org/golang.org/x/net/html#Parse
 doc, err := html.Parse(strings.NewReader(htmlBody))
 if err != nil {
 fmt.Println(err)
 }

 var f func(*html.Node)
 f = func(n *html.Node) {
 if n.Type == html.ElementNode && n.Data == "td" {
 for _, attr := range n.Attr {
 if attr.Key == "id" && attr.Val == "final_balance" {
 if n.FirstChild != nil && n.FirstChild.FirstChild != nil {

 spanNode := n.FirstChild.FirstChild
 if spanNode.Data == "span" {
 if spanNode.FirstChild == nil {
 // do nothing
 }
 balance := spanNode.FirstChild.Data
 fmt.Println("Final balance: ", balance)
 break
 }

 }

 }
 }
 }
 for c := n.FirstChild; c != nil; c = c.NextSibling {
 f(c)
 }
 }
 f(doc)
 }

Sample output with bit coin transaction addresses randomly picked up from https://blockchain.info/blocks

$ ./queryblockchain 1KFHE7w8BhaENAswwryaoccDb6qcT6DbYY

Querying Bitcoin address : 1KFHE7w8BhaENAswwryaoccDb6qcT6DbYY

Final balance: 1,342.4838477 BTC

$ ./queryblockchain 1JyiMwNfLcXHztZVMQJ5UWH6cJEyL24jKR

Querying Bitcoin address : 1JyiMwNfLcXHztZVMQJ5UWH6cJEyL24jKR

Final balance: 0 BTC

$ ./queryblockchain 152f1muMCNa7goXYhYAQC61hxEgGacmncB

Querying Bitcoin address : 152f1muMCNa7goXYhYAQC61hxEgGacmncB

Final balance: 4,356.19141589 BTC

References:

https://godoc.org/golang.org/x/net/html#Parse

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  See also : Cash Flow : 50 days to pay your credit card debt



Tags : golang bit-coin btc blockchain final-balance

By Adam Ng

IF you gain some knowledge or the information here solved your programming problem. Please consider donating to the less fortunate or some charities that you like. Apart from donation, planting trees, volunteering or reducing your carbon footprint will be great too.


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