Implements inner hash validation

Implements: #15 (closed)

lib/block/validation/local/inner_hash.ex

+defmodule Block.Validation.Local.InnerHash do
+  def valid(block) do
+    computed_hash = :crypto.hash(:sha256, _get_raw_inner_part(block))
+      |> Base.encode16()
+      |> String.upcase()
+
+    computed_hash == block["inner_hash"]
+  end
+
+  @doc """
+  Convert the given `list` into suitable format for hashing
+
+  Concat a '\n' at the end of each element from `list` and joins the table.
+
+  Returns: string 
+  """
+  def _string_of_list(list) do
+    (list || []) 
+      |> Enum.map(fn i -> i <> "\n" end)
+      |> Enum.join
+  end
+
+
+  @doc """
+  Prepare given `block` for hashing and return computed string
+
+  Returns: string
+  """
+  def _get_raw_inner_part(block) do
+    """
+    Version: #{block["version"]}
+    Type: Block
+    Currency: #{block["currency"]}
+    Number: #{block["number"]}
+    PoWMin: #{block["powMin"]}
+    Time: #{block["time"]}
+    MedianTime: #{block["medianTime"]}
+    #{ if block["dividend"] do "UniversalDividend: #{block["dividend"]}\n" end }\
+    UnitBase: #{block["unitBase"]}
+    Issuer: #{block["issuer"]}
+    IssuersFrame: #{block["issuersFrame"]}
+    IssuersFrameVar: #{block["issuersFrameVar"]}
+    DifferentIssuersCount: #{block["issuersCount"]}
+    #{ if block["previousHash"] do "PreviousHash: #{block["previousHash"]}\n" end }\
+    #{ if block["previousIssuer"] do "PreviousIssuer: #{block["previousIssuer"]}\n" end }\
+    #{ if block["parameters"] do "Parameters: #{block["parameters"]}\n" end }\
+    MembersCount: #{block["membersCount"]}
+    Identities:
+    #{_string_of_list block["identities"]}\
+    Joiners:
+    #{_string_of_list block["joiners"]}\
+    Actives:
+    #{_string_of_list block["actives"]}\
+    Leavers:
+    #{_string_of_list block["leavers"]}\
+    Revoked:
+    #{_string_of_list block["revoked"]}\
+    Excluded:
+    #{_string_of_list block["excluded"]}\
+    Certifications:
+    #{_string_of_list block["certifications"]}\
+    Transactions:
+    #{_string_of_list block["transactions"]}\
+    """
+  end
+end
+