add faucet support

.env.sample

@@ -5,5 +5,9 @@ GOERLI_ENDPOINT=https://eth-goerli.g.alchemy.com/v2/<your-api-key>
 DARWINIA_ENDPOINT=http://g1.dev.darwinia.network:10000
 CRAB_ENDPOINT=https://crab-rpc.darwinia.network
 PANGOLIN_ENDPOINT=https://pangolin-rpc.darwinia.network
+PANGORO_ENDPOINT=https://pangoro-rpc.darwinia.network
 # mongodb
 MONGODB_URI=mongodb+srv://<username>:<password>@<cluster-url>/goerli_pangolin?retryWrites=true&w=majority
+# faucet
+DROP_PRIVATE_KEY=
+DROP_ADDRESS=

src/faucet.rb

@@ -0,0 +1,94 @@
+require "mongo"
+require "eth"
+require "json"
+include Eth
+require "dotenv/load"
+
+def get_nonce(eth_client, address)
+  eth_client.eth_get_transaction_count(address)["result"].to_i(16)
+end
+
+# address:index, network:index, dropped_at, username
+def drop_allowed?(mongo_client, address, network)
+  db = mongo_client[:drops]
+  drop = db.find({ address: address.downcase, network: network }).first
+
+  !drop || drop[:dropped_at] + 24 * 60 * 60 < Time.now.to_i
+end
+
+def do_drop(evm_client, address, network)
+  tx = build_drop_tx(evm_client, address, network)
+  evm_client.eth_send_raw_transaction(tx.hex)["result"]
+end
+
+def build_drop_tx(evm_client, address, network)
+  payload = {
+    chain_id: network == "pangolin" ? 43 : 45,
+    nonce: get_nonce(evm_client, "#{ENV["DROP_ADDRESS"]}"),
+    gas_price: 2000 * Eth::Unit::GWEI,
+    gas_limit: 210_000,
+    to: address,
+    value: 50 * Eth::Unit::ETHER,
+  }
+  tx = Eth::Tx.new payload
+  signer_key = Eth::Key.new priv: "#{ENV["DROP_PRIVATE_KEY"]}"
+  tx.sign signer_key
+  tx
+end
+
+def insert_or_update_drop_record(mongo_client, address, network, username, tx_hash)
+  db = mongo_client[:drops]
+
+  drop = db.find({ address: address.downcase, network: network }).first
+
+  if drop
+    db.update_one(
+      { address: address.downcase, network: network }, 
+      { "$set" => { dropped_at: Time.now.to_i, username: username, tx_hash: tx_hash } }
+    )
+  else 
+    db.insert_one({
+      address: address.downcase,
+      network: network,
+      dropped_at: Time.now.to_i,
+      username: username,
+      tx_hash: tx_hash
+    }) 
+  end
+end
+
+def drop(evm_client, mongo_client, address, network, username)
+  tx_hash = do_drop(evm_client, address, network)
+  insert_or_update_drop_record(mongo_client, address, network, username, tx_hash)
+  tx_hash
+end
+
+# channel for 
+def run_drop(address, network, username)
+  mongo_client = Mongo::Client.new(
+    ENV["MONGODB_URI"],
+    server_api: {
+      version: "1",
+    },
+  )
+
+  if drop_allowed?(mongo_client, address, network)
+    evm_client = 
+      if network == "pangolin"
+        Eth::Client::Http.new(ENV["PANGOLIN_ENDPOINT"])
+      else
+        Eth::Client::Http.new(ENV["PANGORO_ENDPOINT"])
+      end
+
+    drop(evm_client, mongo_client, address, network, username)
+  else
+    raise "Drop not allowed"
+  end
+end
+
+# client = Eth::Client::Http.new("https://pangolin-rpc.darwinia.network")
+# tx = build_drop_tx(client, "0xDa97bC5EE02F33B92A0665620fFE956E21BAEf0f", "pangolin")
+# # puts tx.hash
+# # puts client.eth_send_raw_transaction(tx.hex)["result"]
+
+# puts run_drop("0xDa97bC5EE02F33B92A0665620fFE956E21BAEf0f", "pangolin", "test")

src/server.rb

@@ -9,13 +9,38 @@
 require_relative "./utils"
 require_relative "./storage"
 require_relative "./account"
+require_relative "./faucet"
 
 config = get_config
 
 get "/" do
   "Hello Darwinia!"
 end
 
+post "/faucet" do
+  network = params["network"] ||= "pangolin"
+  if not %w[pangolin pangoro].include?(network.downcase)
+    raise_with(
+      404,
+      "network #{network} not found, only `pangolin` and `pangoro` are supported",
+    )
+  end
+
+  # TODO: check the address is valid
+  address = params["address"]
+  unless address
+    raise_with(400, "address is required")
+  end
+  if address !~ /^0x[0-9a-fA-F]{40}$/
+    raise_with(400, "address is invalid")
+  end
+
+  username = params["username"]
+
+  tx_hash = run_drop(address, network, username)
+  render_json tx_hash
+end
+
 ##############################################################################
 # Darwinia & Crab's supplies
 ##############################################################################