Implement proof-of-work

Using blacke2s: https://docs.rs/blake2/0.9.1/blake2/
Using this guy's hash checker https://gist.github.com/gkbrk/2e4835e3a17b3fb6e1e7

blacke2s with 5 bits 0 can mine a block between 20 seconds to 359 during
my tests, hope it'll be fun

1 files changed, 35 insertions, 0 deletions

diff --git a/examples/mining.rs b/examples/mining.rs
new file mode 100644
index 0000000..56e33f3
--- /dev/null
+++ b/examples/mining.rs
@@ -0,0 +1,35 @@
+use chrono::NaiveDate;
+use gradecoin::schema::NakedBlock;
+use serde_json;
+use std::time::Instant;
+
+use blake2::{Blake2s, Digest};
+
+pub fn main() {
+    let mut b = NakedBlock {
+        transaction_list: vec![
+            "hash_value".to_owned(),
+        ],
+        nonce: 0,
+        timestamp: NaiveDate::from_ymd(2021, 04, 08).and_hms(12, 30, 30),
+    };
+
+    let now = Instant::now();
+
+    for nonce in 0..u32::MAX {
+        b.nonce = nonce;
+
+        let j = serde_json::to_vec(&b).unwrap();
+
+        let result = Blake2s::digest(&j);
+
+        let first_five = result[31] as i32 + result[30] as i32 + (result[29] << 4) as i32;
+
+        if first_five == 0 {
+            println!("{} - {:x}\n{:?}", nonce, result, b);
+            break;
+        }
+    }
+
+    println!("it took {} seconds", now.elapsed().as_secs());
+}