Adding some comments to the block_header module and changing the data…

… type of the sha256 variables

src/block/block_header.rs

@@ -17,14 +17,21 @@ use chrono::{DateTime, Utc};
 */
 #[derive(Debug)]
 pub struct BlockHeader {
-    pub block_id: String,
-    pub txs_merkle_root: String,
+    // block_id is intended to store the sha256 hash of the previous block's header, as in bitcoin
+    pub block_id: String, //[u8; 32],
+    // the block's transactions merkle root, intended also to store a sha256 hash
+    // both the block_id and txs_merkle_root content is garanteed to store a 32 bytes value
+    // in the "new()" method
+    pub txs_merkle_root: String, //[u8; 32],
+    // intended to include information about the time the block was mined
     pub timestamp: DateTime<Utc>,
-    pub nonce: u32
+    pub target_hash: String, //[u8; 32],
+    // value to be adjusted in order to find the pre image for the sha256 hash below the target 
+    pub nonce: u32,
 }
 
 impl BlockHeader {
-    pub fn new(block_id: String, txs_merkle_root: String, timestamp: DateTime<Utc>, nonce: u32) -> BlockHeader {
+    pub fn new(block_id: String, txs_merkle_root: String, timestamp: DateTime<Utc>, nonce: u32) -> Self {
         // I did not find a better way of representing the block id and merkle root other than
         // String for now, so it uses the following control flows to avoid having "hashes" 
         //different than 32 bytes.
@@ -35,13 +42,18 @@ impl BlockHeader {
             panic!("The txs_merkle_root parameter needs to be a 32 bytes length string");
         }
 
-        BlockHeader {
+        Self {
             block_id, 
-            txs_merkle_root, 
+            txs_merkle_root,
+            target_hash: String::from("0000ffff00000000000000000000000000000000000000000000000000000000"),
             timestamp,
             nonce
         }
     }
+
+    pub fn get_block_header_sha256sum() -> String{
+        String::from("Hello World")
+    }
 }
 
 impl fmt::Display for BlockHeader {