refactor(config): remove legacy configuration formats and values

Deprecates and removes support for legacy configuration formats to
simplify the codebase and enforce modern standards. This change
standardizes date handling and limit definitions across the bot.

Key changes:
- Removed support for legacy comma-separated `end_date` (YYYY,M,D) in
  favor of ISO-8601 (YYYY-MM-DD).
- Removed support for `-1` as an "unlimited" value for
  `max_active_amount` and `max_offer_size`.
- Updated `max_active_amount` to use `None` (null) for unlimited
  lending, enforced via Pydantic validation.
- Standardized `max_offer_size` to use `0` for unlimited offer sizes.
- Updated documentation and sample configurations to reflect the
  removal of legacy options.
- Refactored internal logic in `Data`, `Lending`, and `MaxToLend`
  modules to handle the new configuration schema.
- Updated test suite to verify strict validation and correct behavior
  with the new defaults.

BREAKING CHANGE: Configuration files using the `YYYY,M,D` date format or
`-1` for unlimited limits will now fail validation. Users must update
their `config.toml` to use `YYYY-MM-DD` and `0` or omit the limit keys.

Author: Carton

config_sample_advanced.toml

@@ -27,7 +27,6 @@ keep_stuck_orders = true
 hide_coins = true
 
 # Stop opening loans after this date approaches. Preferred format: YYYY-MM-DD.
-# Legacy YYYY,M,D is still accepted.
 # end_date = "2026-12-25"
 
 # Auto-transfer funds from exchange balance to lending balance.
@@ -52,12 +51,10 @@ min_loan_size = 0.01
 
 # Total active lending cap for each currency:
 # omit = unlimited, 0 = disable this currency, >0 = cap in coin units.
-# Legacy -1 is still accepted as unlimited.
 # max_active_amount = 5000
 
 # Single offer size cap:
 # omit or 0 = unlimited, >0 = cap each offer in coin units.
-# Legacy -1 is still accepted as unlimited.
 # max_offer_size = 1000
 
 # Strategy selection: "FRR" (Bitfinex only) or "Spread".

docs/configuration.rst

@@ -271,8 +271,7 @@ Very few situations require you to change these settings.
 
     - Default value: Disabled
     - Uncomment to enable.
-    - Preferred format: ``YYYY-MM-DD``.
-    - Legacy ``YYYY,M,D`` values are still accepted for existing configs.
+    - Format: ``YYYY-MM-DD``.
 
 Config per Coin
 ---------------
@@ -306,7 +305,6 @@ Max Active Amount (Limit Total Lending)
         - Omitted = Unlimited (no restriction on total lending)
         - ``0`` = Disabled (skip this coin entirely, equivalent to not listing it in ``all_currencies``)
         - ``> 0`` = Limit (cap total lending to this amount in coin units)
-        - ``-1`` = Legacy unlimited value, still accepted for backward compatibility
     - This is useful when you want to maintain a reserve or limit exposure for a specific currency.
     - The limit applies to the total amount currently lent out (active loans). If you have 10000 USD and set ``max_active_amount = 5000``, the bot will only lend up to 5000 USD total.
     - Example: If you have ``max_active_amount = 1000`` for USD and currently have 800 USD lent out, the bot will only offer up to 200 USD more in new loans.
@@ -328,7 +326,6 @@ Max Offer Size (Smooth Lending Over Time)
     - Allowed values:
         - Omitted or ``0`` = Unlimited (standard spreading applies)
         - ``> 0`` = Limit (cap each individual offer to this amount)
-        - ``-1`` = Legacy unlimited value, still accepted for backward compatibility
     - If set to >0, no individual loan offer will exceed this amount. Unused balance remains in your wallet and will be offered in the next bot cycle (e.g. 60 seconds later). This effectively creates a Dollar Cost Averaging (DCA) effect, smoothing out your lending rates over time.
 
     Example configuration:

src/lendingbot/modules/Configuration.py

@@ -107,14 +107,14 @@ def convert_percent_to_decimal(cls, v: Decimal) -> Decimal:
 
     min_loan_size: Decimal = Field(Decimal("0.01"), ge=Decimal("0.005"))
     # max_active_amount: Limits total lending for this currency.
-    #   -1 = unlimited (no limit on total lending)
-    #    0 = disabled (skip this coin entirely, equivalent to not including in all_currencies)
-    #   >0 = limit (cap total lending to this amount in coin units, e.g., 1000 USD)
-    max_active_amount: Decimal = Decimal("-1")
+    #   None = unlimited (no limit on total lending)
+    #      0 = disabled (skip this coin entirely, equivalent to not including in all_currencies)
+    #     >0 = limit (cap total lending to this amount in coin units, e.g., 1000 USD)
+    max_active_amount: Decimal | None = Field(default=None, ge=Decimal("0"))
     # max_offer_size: Limits the maximum amount of a *single* loan offer.
-    #   0 or -1 = unlimited (no limit on single offer size)
+    #   0 = unlimited (no limit on single offer size)
     #   >0 = limit (cap single offer to this amount in coin units, e.g., 1000 USD)
-    max_offer_size: Decimal = Decimal("0")
+    max_offer_size: Decimal = Field(Decimal("0"), ge=Decimal("0"))
 
     # Strategy
     strategy: LendingStrategy = LendingStrategy.SPREAD

src/lendingbot/modules/Data.py

@@ -63,11 +63,7 @@ def get_max_duration(end_date: str, context: str) -> int | str:
         return ""
     try:
         now_time = datetime.date.today()
-        if "-" in end_date:
-            end_time = datetime.date.fromisoformat(end_date)
-        else:
-            config_date = [int(x) for x in end_date.split(",")]
-            end_time = datetime.date(*config_date)  # legacy format: YEAR,MONTH,DAY
+        end_time = datetime.date.fromisoformat(end_date)
         diff_days = (end_time - now_time).days
         if context == "order":
             return diff_days  # Order needs int

src/lendingbot/modules/Lending.py

@@ -577,7 +577,7 @@ def construct_orders(
         new_order_rates = sorted(set(order_rates))
         new_order_amounts = []
 
-        cur_max_offer_size = Decimal("-1")
+        cur_max_offer_size = Decimal("0")
         if cfg := self.coin_cfg.get(cur):
             cur_max_offer_size = cfg.max_offer_size
 

src/lendingbot/modules/MaxToLend.py

@@ -49,14 +49,14 @@ def amount_to_lend(
     if log is None:
         return lending_balance
 
-    cur_max_active_amount = Decimal("-1")
+    cur_max_active_amount: Decimal | None = None
 
     if cfg := coin_cfg.get(active_cur):
         cur_max_active_amount = cfg.max_active_amount
 
     # Check max_active_amount limit first (absolute cap on total lending)
-    # max_active_amount: -1 = unlimited, 0 = disabled (handled elsewhere), > 0 = limit
-    if cur_max_active_amount > 0:
+    # max_active_amount: None = unlimited, 0 = disabled (handled elsewhere), > 0 = limit
+    if cur_max_active_amount is not None and cur_max_active_amount > 0:
         # Calculate how much more we can lend without exceeding max_active_amount
         # total_lent = currently lent out (active loans)
         # lending_balance = available to lend (not yet offered)

tests/test_Configuration.py

@@ -184,36 +184,35 @@ def test_basic_sample_uses_defaults_for_omitted_optional_settings(self) -> None:
         self.assertEqual(config.bot.period_active, 60)
         self.assertEqual(config.bot.request_timeout, 30)
         self.assertEqual(config.bot.web.host, "127.0.0.1")
-        self.assertEqual(config.get_coin_config("USD").max_active_amount, Decimal("-1"))
+        self.assertIsNone(config.get_coin_config("USD").max_active_amount)
         self.assertEqual(config.get_coin_config("USD").max_offer_size, Decimal("0"))
 
     def test_max_active_amount_semantics(self) -> None:
         default_cfg = Conf.CoinConfig()
-        legacy_unlimited_cfg = Conf.CoinConfig(max_active_amount=Decimal("-1"))
         disabled_cfg = Conf.CoinConfig(max_active_amount=Decimal("0"))
         capped_cfg = Conf.CoinConfig(max_active_amount=Decimal("5000"))
 
-        self.assertEqual(default_cfg.max_active_amount, Decimal("-1"))
-        self.assertEqual(legacy_unlimited_cfg.max_active_amount, Decimal("-1"))
+        self.assertIsNone(default_cfg.max_active_amount)
         self.assertEqual(disabled_cfg.max_active_amount, Decimal("0"))
         self.assertEqual(capped_cfg.max_active_amount, Decimal("5000"))
 
+        with self.assertRaises(ValidationError):
+            Conf.CoinConfig(max_active_amount=Decimal("-1"))
+
     def test_max_offer_size_semantics(self) -> None:
         default_cfg = Conf.CoinConfig()
-        legacy_unlimited_cfg = Conf.CoinConfig(max_offer_size=Decimal("-1"))
         zero_unlimited_cfg = Conf.CoinConfig(max_offer_size=Decimal("0"))
         capped_cfg = Conf.CoinConfig(max_offer_size=Decimal("100"))
 
         self.assertEqual(default_cfg.max_offer_size, Decimal("0"))
-        self.assertEqual(legacy_unlimited_cfg.max_offer_size, Decimal("-1"))
         self.assertEqual(zero_unlimited_cfg.max_offer_size, Decimal("0"))
         self.assertEqual(capped_cfg.max_offer_size, Decimal("100"))
 
+        with self.assertRaises(ValidationError):
+            Conf.CoinConfig(max_offer_size=Decimal("-1"))
+
     def test_end_date_accepts_documented_dash_format(self) -> None:
-        self.assertEqual(
-            get_max_duration("2999-12-31", "order"),
-            get_max_duration("2999,12,31", "order"),
-        )
+        assert isinstance(get_max_duration("2999-12-31", "order"), int)
 
     def test_typed_plugin_defaults(self) -> None:
         config = Conf.RootConfig()

tests/test_Data.py

@@ -59,14 +59,14 @@ def test_get_max_duration_empty_date(self) -> None:
     def test_get_max_duration_order_context(self) -> None:
         """Test get_max_duration with order context returns int"""
         # Use a date far in the future to ensure positive days
-        future_date = "2030,12,31"
+        future_date = "2030-12-31"
         result = get_max_duration(future_date, "order")
         assert isinstance(result, int)
         assert result > 0
 
     def test_get_max_duration_status_context(self) -> None:
         """Test get_max_duration with status context returns string"""
-        future_date = "2030,12,31"
+        future_date = "2030-12-31"
         result = get_max_duration(future_date, "status")
         assert isinstance(result, str)
         assert "Days Remaining" in result

tests/test_Data_core.py

@@ -43,7 +43,7 @@ def test_get_max_duration(self, data_module):
         # Use real dates to avoid mock hell
         today = datetime.date.today()
         tomorrow = today + datetime.timedelta(days=1)
-        end_date_str = f"{tomorrow.year},{tomorrow.month},{tomorrow.day}"
+        end_date_str = tomorrow.isoformat()
 
         assert data_module.get_max_duration(end_date_str, "order") == 1
         assert data_module.get_max_duration(end_date_str, "status") == " - Days Remaining: 1"

tests/test_LendingEngine.py

@@ -279,7 +279,7 @@ def test_calculate_duration_with_end_date(self, engine, mock_data):
 
     def test_construct_orders_max_offer_size_unlimited(self, engine):
         engine.initialize()
-        engine.coin_cfg["BTC"].max_offer_size = Decimal("-1")
+        engine.coin_cfg["BTC"].max_offer_size = Decimal("0")
         # Ensure spread allows 3 orders
         engine.spread_lend = 3
         # Mock gap rates