Move max_buy and ask_spread into config

Max-buy and spread is not something that one would configure on every run.
More convenient to keep this in the config.

The max-buy Bitcoin value was adapted to `0.02` which is more reasonable for mainnet.
Activated feature `serde-float` to serialize the spread (Decimal) as float instead of string.

```
...

[maker]
max_buy_btc = 0.02
ask_spread = 0.02
```

CHANGELOG.md

@@ -41,6 +41,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   2. Buy amount sent by CLI exceeds maximum buy amount accepted by ASB
   3. ASB is running in resume-only mode and does not accept incoming swap requests
 
+### Changed
+
+- The ASB's `--max-buy`  and `ask-spread` parameter were removed in favour of entries in the config file.
+  The initial setup includes setting these two values now.
+
 ## [0.5.0] - 2021-04-17
 
 ### Changed

swap/Cargo.toml

@@ -40,7 +40,7 @@ proptest = "1"
 rand = "0.7"
 rand_chacha = "0.2"
 reqwest = { version = "0.11", features = [ "rustls-tls", "stream", "socks" ], default-features = false }
-rust_decimal = "1"
+rust_decimal = { version = "1", features = [ "serde-float" ] }
 rust_decimal_macros = "1"
 serde = { version = "1", features = [ "derive" ] }
 serde_cbor = "0.11"

swap/src/asb/command.rs

@@ -1,7 +1,5 @@
 use crate::bitcoin::Amount;
-use bitcoin::util::amount::ParseAmountError;
-use bitcoin::{Address, Denomination};
-use rust_decimal::Decimal;
+use bitcoin::Address;
 use std::path::PathBuf;
 use uuid::Uuid;
 
@@ -28,15 +26,6 @@ pub struct Arguments {
 pub enum Command {
     #[structopt(about = "Main command to run the ASB.")]
     Start {
-        #[structopt(long = "max-buy-btc", help = "The maximum amount of BTC the ASB is willing to buy.", default_value = "0.005", parse(try_from_str = parse_btc))]
-        max_buy: Amount,
-        #[structopt(
-            long = "ask-spread",
-            help = "The spread in percent that should be applied to the asking price.",
-            default_value = "0.02"
-        )]
-        ask_spread: Decimal,
-
         #[structopt(
             long = "resume-only",
             help = "For maintenance only. When set, no new swap requests will be accepted, but existing unfinished swaps will be resumed."
@@ -124,7 +113,3 @@ pub struct RecoverCommandParams {
     )]
     pub force: bool,
 }
-
-fn parse_btc(s: &str) -> Result<Amount, ParseAmountError> {
-    Amount::from_str_in(s, Denomination::Bitcoin)
-}

swap/src/asb/config.rs

@@ -1,10 +1,12 @@
 use crate::fs::{ensure_directory_exists, system_config_dir, system_data_dir};
 use crate::tor::{DEFAULT_CONTROL_PORT, DEFAULT_SOCKS5_PORT};
-use anyhow::{Context, Result};
+use anyhow::{bail, Context, Result};
 use config::ConfigError;
 use dialoguer::theme::ColorfulTheme;
 use dialoguer::Input;
 use libp2p::core::Multiaddr;
+use rust_decimal::prelude::FromPrimitive;
+use rust_decimal::Decimal;
 use serde::{Deserialize, Serialize};
 use std::ffi::OsStr;
 use std::fs;
@@ -18,6 +20,9 @@ const DEFAULT_ELECTRUM_RPC_URL: &str = "ssl://electrum.blockstream.info:60002";
 const DEFAULT_MONERO_WALLET_RPC_TESTNET_URL: &str = "http://127.0.0.1:38083/json_rpc";
 const DEFAULT_BITCOIN_CONFIRMATION_TARGET: usize = 3;
 
+const DEFAULT_MAX_BUY_AMOUNT: f64 = 0.02f64;
+const DEFAULT_SPREAD: f64 = 0.02f64;
+
 #[derive(Clone, Debug, serde::Serialize, serde::Deserialize, PartialEq)]
 pub struct Config {
     pub data: Data,
@@ -25,6 +30,7 @@ pub struct Config {
     pub bitcoin: Bitcoin,
     pub monero: Monero,
     pub tor: TorConf,
+    pub maker: Maker,
 }
 
 impl Config {
@@ -72,6 +78,14 @@ pub struct TorConf {
     pub socks5_port: u16,
 }
 
+#[derive(Clone, Debug, Deserialize, PartialEq, Serialize)]
+#[serde(deny_unknown_fields)]
+pub struct Maker {
+    #[serde(with = "::bitcoin::util::amount::serde::as_btc")]
+    pub max_buy_btc: bitcoin::Amount,
+    pub ask_spread: Decimal,
+}
+
 impl Default for TorConf {
     fn default() -> Self {
         Self {
@@ -186,6 +200,21 @@ pub fn query_user_for_initial_testnet_config() -> Result<Config> {
         .default(DEFAULT_SOCKS5_PORT.to_owned())
         .interact_text()?;
 
+    let max_buy = Input::with_theme(&ColorfulTheme::default())
+        .with_prompt("Enter maximum Bitcoin amount you are willing to accept per swap or hit enter to use default.")
+        .default(DEFAULT_MAX_BUY_AMOUNT)
+        .interact_text()?;
+    let max_buy = bitcoin::Amount::from_btc(max_buy)?;
+
+    let ask_spread = Input::with_theme(&ColorfulTheme::default())
+        .with_prompt("Enter spread (in percent; value between 0.x and 1.0) to be used on top of the market rate or hit enter to use default.")
+        .default(DEFAULT_SPREAD)
+        .interact_text()?;
+    if !(0.0..=1.0).contains(&ask_spread) {
+        bail!(format!("Invalid spread {}. For the spread value floating point number in interval [0..1] are allowed.", ask_spread))
+    }
+    let ask_spread = Decimal::from_f64(ask_spread).context("Unable to parse spread")?;
+
     println!();
 
     Ok(Config {
@@ -204,6 +233,10 @@ pub fn query_user_for_initial_testnet_config() -> Result<Config> {
             control_port: tor_control_port,
             socks5_port: tor_socks5_port,
         },
+        maker: Maker {
+            max_buy_btc: max_buy,
+            ask_spread,
+        },
     })
 }
 
@@ -237,6 +270,10 @@ mod tests {
                 wallet_rpc_url: Url::from_str(DEFAULT_MONERO_WALLET_RPC_TESTNET_URL).unwrap(),
             },
             tor: Default::default(),
+            maker: Maker {
+                max_buy_btc: bitcoin::Amount::from_btc(DEFAULT_MAX_BUY_AMOUNT).unwrap(),
+                ask_spread: Decimal::from_f64(DEFAULT_SPREAD).unwrap(),
+            },
         };
 
         initial_setup(config_path.clone(), || Ok(expected.clone())).unwrap();

swap/src/bin/asb.rs

@@ -79,11 +79,7 @@ async fn main() -> Result<()> {
     let env_config = env::Testnet::get_config();
 
     match opt.cmd {
-        Command::Start {
-            max_buy,
-            ask_spread,
-            resume_only,
-        } => {
+        Command::Start { resume_only } => {
             let bitcoin_wallet = init_bitcoin_wallet(&config, &seed, env_config).await?;
             let monero_wallet = init_monero_wallet(&config, env_config).await?;
 
@@ -122,12 +118,12 @@ async fn main() -> Result<()> {
 
             let current_balance = monero_wallet.get_balance().await?;
             let lock_fee = monero_wallet.static_tx_fee_estimate();
-            let kraken_rate = KrakenRate::new(ask_spread, kraken_price_updates);
+            let kraken_rate = KrakenRate::new(config.maker.ask_spread, kraken_price_updates);
             let mut swarm = swarm::alice(
                 &seed,
                 current_balance,
                 lock_fee,
-                max_buy,
+                config.maker.max_buy_btc,
                 kraken_rate.clone(),
                 resume_only,
             )?;
@@ -144,7 +140,7 @@ async fn main() -> Result<()> {
                 Arc::new(monero_wallet),
                 Arc::new(db),
                 kraken_rate,
-                max_buy,
+                config.maker.max_buy_btc,
             )
             .unwrap();