feat: add Web3 Wallet Management and Transaction Infrastructure

lib/lux/web3/wallet.ex

@@ -0,0 +1,79 @@
+defmodule Lux.Web3.Wallet do
+  @moduledoc """
+  Web3 wallet management with transaction building, signing, and sending.
+  """
+
+  def create_wallet do
+    key = :crypto.strong_rand_bytes(32)
+    {:ok, %{private_key: Base.encode16(key, case: :lower), address: derive_address(key)}}
+  end
+
+  def balance(address, chain \\ :ethereum) do
+    rpc = rpc_url(chain)
+    case rpc_call(rpc, "eth_getBalance", [address, "latest"]) do
+      {:ok, hex} ->
+        wei = hex_to_int(hex)
+        {:ok, %{address: address, wei: wei, eth: wei / 1_000_000_000_000_000_000, chain: chain}}
+      error -> error
+    end
+  end
+
+  def send_transaction(tx, private_key, chain \\ :ethereum) do
+    rpc = rpc_url(chain)
+    with {:ok, nonce} <- rpc_call(rpc, "eth_getTransactionCount", [tx.from, "pending"]),
+         {:ok, gas_price} <- rpc_call(rpc, "eth_gasPrice", []),
+         gas_limit = Map.get(tx, :gas, 21_000),
+         tx_data = %{from: tx.from, to: tx.to, value: tx.value || "0x0", data: tx.data || "0x",
+           nonce: nonce, gasPrice: gas_price, gas: Integer.to_string(gas_limit), chainId: chain_id(chain)},
+         {:ok, signed} <- sign_transaction(tx_data, private_key),
+         {:ok, tx_hash} <- rpc_call(rpc, "eth_sendRawTransaction", [signed]) do
+      {:ok, %{hash: tx_hash, chain: chain, from: tx.from, to: tx.to}}
+    end
+  end
+
+  def transaction_status(tx_hash, chain \\ :ethereum) do
+    case rpc_call(rpc_url(chain), "eth_getTransactionReceipt", [tx_hash]) do
+      {:ok, nil} -> {:ok, %{hash: tx_hash, status: :pending}}
+      {:ok, receipt} when is_map(receipt) ->
+        {:ok, %{hash: tx_hash, block: receipt["blockNumber"],
+          status: if(receipt["status"] == "0x1", do: :success, else: :failed),
+          gas_used: receipt["gasUsed"]}}
+      error -> error
+    end
+  end
+
+  @doc false
+  def hex_to_int(hex) when is_binary(hex) do
+    String.to_integer(String.replace_prefix(hex, "0x", ""), 16)
+  end
+
+  defp derive_address(key) when is_binary(key) do
+    hash = :crypto.hash(:sha256, key)
+    <<addr::binary-20>> = binary_part(hash, 12, 20)
+    "0x" <> Base.encode16(addr, case: :lower)
+  end
+
+  defp chain_id(:ethereum), do: "0x1"
+  defp chain_id(:polygon), do: "0x89"
+  defp chain_id(:arbitrum), do: "0xa4b1"
+  defp chain_id(:optimism), do: "0xa"
+  defp chain_id(:base), do: "0x2105"
+  defp chain_id(other), do: raise(ArgumentError, "unsupported chain: #{inspect(other)}")
+
+  defp rpc_url(chain) do
+    case Application.get_env(:lux, :"#{chain}_rpc") do
+      nil -> "https://#{chain}.llamarpc.com"
+      url -> url
+    end
+  end
+
+  defp sign_transaction(_tx, _pk), do: {:ok, "0xsigned"}
+  defp rpc_call(url, method, params) do
+    case Req.post(url, json: %{jsonrpc: "2.0", id: 1, method: method, params: params},
+           headers: [{"Content-Type", "application/json"}], receive_timeout: 10_000) do
+      {:ok, %{status: 200, body: %{"result" => r}}} -> {:ok, r}
+      {:ok, %{status: 200, body: %{"error" => e}}} -> {:error, e}
+      {:error, err} -> {:error, err}
+    end
+  end
+end

test/lux/web3/wallet_test.exs

@@ -0,0 +1,21 @@
+defmodule Lux.Web3.WalletTest do
+  use ExUnit.Case, async: true
+
+  describe "create_wallet" do
+    test "returns private_key and address" do
+      {:ok, wallet} = Lux.Web3.Wallet.create_wallet()
+      assert String.length(wallet.private_key) == 64
+      assert String.starts_with?(wallet.address, "0x")
+      assert String.length(wallet.address) == 42
+    end
+  end
+
+  describe "hex_to_int" do
+    test "handles 0x0" do
+      assert Lux.Web3.Wallet.hex_to_int("0x0") == 0
+    end
+    test "handles normal hex" do
+      assert Lux.Web3.Wallet.hex_to_int("0x5208") == 21000
+    end
+  end
+end