Add annotations for decimal utilty.

Author: Qiu-INJ

src/injective/utils.py

@@ -1,7 +1,35 @@
 from decimal import Decimal
+"""
+One thing you may need to pay more attention to is how to deal with decimals in injective exchange. 
+As we all known, different crypto currecies require diffrent decimal precisions. 
+Separately, ERC-20 tokens(e.g. INJ) have decimals of 18 or another number(like 6 for USDT and USDC).
+So in injective system that means ** having 1 INJ is 1e18 inj ** and that ** 1 USDT is actually 100000 peggy0xdac17f958d2ee523a2206206994597c13d831ec7**.
 
+For spot markets, a price reflects the ** relative exchange rate ** between two tokens.
+If the tokens have the same decimal scale, that's great since the prices 
+become interpretable e.g. USDT/USDC (both have 6 decimals e.g. for USDT https://etherscan.io/address/0xdac17f958d2ee523a2206206994597c13d831ec7#readContract) 
+or MATIC/INJ (both have 18 decimals) since the decimals cancel out.
+Prices however start to look wonky once you have exchanges between two tokens of different decimals, which unfortunately is most pairs with USDT or USDC denominations.
+As such, I've created some simple utility functions by keeping a hardcoded dictionary in injective-py and you can aslo achieve such utilities by yourself
+(e.g. you can use external API like Alchemy's getTokenMetadata to fetch decimal of base and quote asset).
 
+So for INJ/USDT of 6.9, the price you end up getting is 6.9*10 ^ (6 - 18) = 6.9e-12.
+Note that this market also happens to have a MinPriceTickSize of 1e-15.
+This makes sense since since it's defining the minimum price increment of the relative exchange of INJ to USDT.
+Note that this market also happens to have a MinQuantityTickSize of 1e15.
+This also makes sense since it refers to the minimum INJ quantity tick size each order must have, which is 1e15/1e18 = 0.001 INJ.
+"""
 def price_float_to_string(price, base_decimals, quote_decimals, precision=18) -> str:
+    """transfer price[float] to string which satisfies what injective exchange backend requires
+
+    Args:
+        price ([float]): normal price, you can read it directly in exchange front-end
+        base_decimals ([int]): decimal of base asset
+        quote_decimals ([int]): quote asset's decimal
+        precision (int, optional): [description]. Defaults to 18.
+    Returns: 
+        str: relative price for base asset and quote asset. For INJ/USDT of 6.9, the price you end up getting is 6.9*10 ^ (6 - 18) = 6.9e-12.
+    """
     scale = Decimal(quote_decimals - base_decimals)
     exchange_price = Decimal(price) * pow(10, scale)
     price_string = ("{:."+str(precision)+"f}").format(exchange_price)
@@ -10,6 +38,16 @@ def price_float_to_string(price, base_decimals, quote_decimals, precision=18) ->
 
 
 def quantity_float_to_string(quantity, base_decimals, precision=18) -> str:
+    """transfer quantity[float] to string which satisfies what injective exchange backend requires
+
+    Args:
+        quantity ([type]):  normal quantity, you can read it in exchange front-end
+        base_decimals ([type]): decimal of base asset
+        precision (int, optional): [description]. Defaults to 18.
+
+    Returns:
+        str:  acutally quanity of base asset[data type: string] For 1 INJ, the quantity you end up is 1e18 inj
+    """
     scale = Decimal(base_decimals)
     exchange_quantity = Decimal(quantity) * pow(10, scale)
     quantity_string = ("{:."+str(precision)+"f}").format(exchange_quantity)
@@ -18,11 +56,30 @@ def quantity_float_to_string(quantity, base_decimals, precision=18) -> str:
 
 
 def price_string_to_float(price_string, base_decimals, quote_decimals) -> float:
+    """
+    Args:
+        price_string ([type]): price with string data type that injective-exchange backend returns
+        base_decimals ([type]): decimal of base asset
+        quote_decimals ([type]): decimal of quote asset
+
+    Returns:
+        float: actual price what you can read directly from front-end.
+        For 6.9e-12 inj/peggy0xdac17f958d2ee523a2206206994597c13d831ec7**, the price you end up getting is 6.9 INJ/USDT.
+    """
     scale = float(base_decimals - quote_decimals)
     return float(price_string) * pow(10, scale)
 
 
 def quantity_string_to_float(quantity_string, base_decimals) -> float:
+    """
+
+    Args:
+        quantity_string ([type]): quantity string that injective-exchange backend returns
+        base_decimals ([type]): decimal of base asset
+
+    Returns:
+        float: actually quantity, for 1e18 inj, you will get 1 INJ
+    """
     scale = float(0 - base_decimals)
     return float(quantity_string) * pow(10, scale)