From e6fd8cc0f20da457563892dd5f114f9836f4b209 Mon Sep 17 00:00:00 2001
From: Lex Berezhny <lex@damoti.com>
Date: Wed, 15 Aug 2018 15:23:00 -0400
Subject: [PATCH] wip new header stuff

---
 lbrynet/wallet/header.py | 83 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 83 insertions(+)
 create mode 100644 lbrynet/wallet/header.py

diff --git a/lbrynet/wallet/header.py b/lbrynet/wallet/header.py
new file mode 100644
index 000000000..d1e37c723
--- /dev/null
+++ b/lbrynet/wallet/header.py
@@ -0,0 +1,83 @@
+import struct
+from typing import Optional
+from binascii import hexlify, unhexlify
+
+from torba.baseheader import BaseHeaders, ArithUint256
+from torba.hash import sha512, double_sha256, ripemd160
+
+
+class Headers(BaseHeaders):
+
+    header_size = 112
+    chunk_size = 10**16
+
+    max_target = 0x0000ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
+    genesis_hash = b'9c89283ba0f3227f6c03b70216b9f665f0118d5e0fa729cedf4fb34d6a34f463'
+    target_timespan = 150
+
+    @property
+    def claim_trie_root(self):
+        return self[self.height]['claim_trie_root']
+
+    @staticmethod
+    def serialize(header):
+        return b''.join([
+            struct.pack('<I', header['version']),
+            unhexlify(header['prev_block_hash'])[::-1],
+            unhexlify(header['merkle_root'])[::-1],
+            unhexlify(header['claim_trie_root'])[::-1],
+            struct.pack('<III', header['timestamp'], header['bits'], header['nonce'])
+        ])
+
+    @staticmethod
+    def deserialize(height, header):
+        version, = struct.unpack('<I', header[:4])
+        timestamp, bits, nonce = struct.unpack('<III', header[100:112])
+        return {
+            'version': version,
+            'prev_block_hash': hexlify(header[4:36][::-1]),
+            'merkle_root': hexlify(header[36:68][::-1]),
+            'claim_trie_root': hexlify(header[68:100][::-1]),
+            'timestamp': timestamp,
+            'bits': bits,
+            'nonce': nonce,
+            'block_height': height,
+        }
+
+    def get_next_block_target(self, max_target: ArithUint256, previous: Optional[dict],
+                              current: Optional[dict]) -> ArithUint256:
+        # https://github.com/lbryio/lbrycrd/blob/master/src/lbry.cpp
+        if previous is None and current is None:
+            return max_target
+        if previous is None:
+            previous = current
+        actual_timespan = current['timestamp'] - previous['timestamp']
+        modulated_timespan = self.target_timespan + int((actual_timespan - self.target_timespan) / 8)
+        minimum_timespan = self.target_timespan - int(self.target_timespan / 8)  # 150 - 18 = 132
+        maximum_timespan = self.target_timespan + int(self.target_timespan / 2)  # 150 + 75 = 225
+        clamped_timespan = max(minimum_timespan, min(modulated_timespan, maximum_timespan))
+        target = ArithUint256.from_compact(current['bits'])
+        new_target = min(max_target, (target * clamped_timespan) / self.target_timespan)
+        return new_target
+
+    @classmethod
+    def get_proof_of_work(cls, header_hash: bytes):
+        return super().get_proof_of_work(
+            cls.header_hash_to_pow_hash(header_hash)
+        )
+
+    @staticmethod
+    def header_hash_to_pow_hash(header_hash: bytes):
+        header_hash_bytes = unhexlify(header_hash)[::-1]
+        h = sha512(header_hash_bytes)
+        pow_hash = double_sha256(
+            ripemd160(h[:len(h) // 2]) +
+            ripemd160(h[len(h) // 2:])
+        )
+        return hexlify(pow_hash[::-1])
+
+
+class UnvalidatedHeaders(Headers):
+    validate_difficulty = False
+    max_target = 0x7fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
+    genesis_hash = b'6e3fcf1299d4ec5d79c3a4c91d624a4acf9e2e173d95a1a0504f677669687556'