From 00494d4963ad393a271d1fada55fe04c6b0293a3 Mon Sep 17 00:00:00 2001
From: Deirdre Connolly <deirdre@zfnd.org>
Date: Tue, 24 Sep 2019 14:16:41 -0400
Subject: [PATCH] Block and BlockHeader types

---
 zebra-chain/Cargo.toml   |  5 +--
 zebra-chain/src/block.rs | 66 ++++++++++++++++++++++++++++++++++++++--
 2 files changed, 66 insertions(+), 5 deletions(-)

diff --git a/zebra-chain/Cargo.toml b/zebra-chain/Cargo.toml
index a319a2f02..7587a6be7 100644
--- a/zebra-chain/Cargo.toml
+++ b/zebra-chain/Cargo.toml
@@ -7,6 +7,7 @@ edition = "2018"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-sha2 = "0.8"
 byteorder = "1.3"
-failure = "0.1"
\ No newline at end of file
+chrono = "0.4"
+failure = "0.1"
+sha2 = "0.8"
diff --git a/zebra-chain/src/block.rs b/zebra-chain/src/block.rs
index 6fca28c4e..1c26afdfe 100644
--- a/zebra-chain/src/block.rs
+++ b/zebra-chain/src/block.rs
@@ -1,6 +1,66 @@
 //! Definitions of block datastructures.
 
-/// A block in your blockchain.
-pub struct Block {}
+use crate::transaction::Transaction;
+use chrono::{DateTime, Utc};
 
-impl Block {}
+/// Block header
+pub struct BlockHeader {
+    /// A SHA-256d hash in internal byte order of the previous block’s
+    /// header. This ensures no previous block can be changed without
+    /// also changing this block’s header .
+    previous_block_hash: [u8; 32],
+
+    /// A SHA-256d hash in internal byte order. The merkle root is
+    /// derived from the hashes of all transactions included in this
+    /// block, ensuring that none of those transactions can be modied
+    /// without modifying the header.
+    merkle_root_hash: [u8; 32],
+
+    /// [Sapling onward] The root LEBS2OSP256(rt) of the Sapling note
+    /// commitment tree corresponding to the nal Sapling treestate of
+    /// this block.
+    // TODO: replace type with custom SaplingRoot or similar type
+    // hash_final_sapling_root: [u8; 32],
+
+    /// The block timestamp is a Unix epoch time (UTC) when the miner
+    /// started hashing the header (according to the miner).
+    time: DateTime<Utc>,
+
+    /// An encoded version of the target threshold this block’s header
+    /// hash must be less than or equal to, in the same nBits format
+    /// used by Bitcoin.
+    ///
+    /// For a block at block height height, bits MUST be equal to
+    /// ThresholdBits(height).
+    ///
+    /// [Bitcoin-nBits](https://bitcoin.org/en/developer-reference#target-nbits)
+    // pzec has their own wrapper around u32 for this field:
+    // https://github.com/ZcashFoundation/zebra/blob/master/zebra-primitives/src/compact.rs
+    bits: u32,
+
+    /// An arbitrary field that miners can change to modify the header
+    /// hash in order to produce a hash less than or equal to the
+    /// target threshold.
+    nonce: [u8; 32],
+
+    /// The Equihash solution.
+    // The solution size when serialized should be in bytes ('always 1344').
+    solution: [u8; 1344],
+}
+
+impl BlockHeader {
+    /// Get the SHA-256d hash in internal byte order of this block header.
+    pub fn hash(&self) -> [u8; 32] {
+        unimplemented!();
+    }
+}
+
+/// A block in your blockchain.
+pub struct Block {
+    /// First 80 bytes of the block as defined by the encoding used by
+    /// "block" messages
+    pub header: BlockHeader,
+
+    ///
+    pub transactions: Vec<Transaction>,
+}