JeffDeCola/my-go-examples

// my-go-examples single-node-blockchain-with-REST guts.go

package main

import (
    "crypto/sha256"
    "encoding/hex"
    "strconv"
    "time"
)

// GET HASH
// SHA256 hasing
func calculateBlockHash(block BlockStruct) string {

    record := strconv.Itoa(block.Index) + block.Timestamp + block.Data + block.PrevHash
    h := sha256.New()
    h.Write([]byte(record))
    hashed := h.Sum(nil)
    return hex.EncodeToString(hashed)

}

// CHECK THAT A NEW BLOCK IS VALID
func isBlockValid(checkBlock, oldBlock BlockStruct) bool {

    // Check index
    if oldBlock.Index+1 != checkBlock.Index {
        return false
    }

    // Compare the hash matches
    if oldBlock.Hash != checkBlock.PrevHash {
        return false
    }

    // Recalculate Hash to check
    if calculateBlockHash(checkBlock) != checkBlock.Hash {
        return false
    }

    return true
}

// CREATE NEW BLOCK
func createNewBlock(oldBlock BlockStruct, data string) BlockStruct {

    var newBlock BlockStruct

    t := time.Now()

    newBlock.Index = oldBlock.Index + 1
    newBlock.Timestamp = t.String()
    newBlock.Data = data
    newBlock.PrevHash = oldBlock.Hash
    newBlock.Hash = calculateBlockHash(newBlock)

    return newBlock
}