fix: adding file to calculate price per share of a token

yearn/prices/pps.py

@@ -0,0 +1,64 @@
+from brownie import chain
+
+from cachetools.func import ttl_cache
+from yearn.utils import Singleton
+from yearn.networks import Network
+from yearn.exceptions import UnsupportedNetwork
+from yearn.utils import contract
+import yearn.prices.magic as magic
+import logging
+
+logger = logging.getLogger(__name__)
+
+
+networks = [ Network.Mainnet, Network.Fantom, Network.Arbitrum ]
+assets = {
+    Network.Mainnet: {
+      "0x03403154afc09Ce8e44C3B185C82C6aD5f86b9ab": 12429262,
+    }
+}
+
+class PricePerShare(metaclass=Singleton):
+    def __init__(self):
+        if chain.id not in networks:
+            raise UnsupportedNetwork('pps is not supported on this network')
+
+
+    def token_wants_pps_price(self, asset, block=None):
+        if asset not in assets[chain.id].keys():
+            return False
+
+        base_block = next(iter(assets[chain.id][asset]))
+        if not block or not base_block:
+            # "0x03403154afc09Ce8e44C3B185C82C6aD5f86b9ab": None
+            # *always* use the pps logic
+            return True
+        else:
+            # "0x03403154afc09Ce8e44C3B185C82C6aD5f86b9ab": 12429262
+            # check if the pps logic should be used based on the given block
+            return block <= base_block
+
+
+    @ttl_cache(maxsize=None, ttl=600)
+    def get_price(self, asset, block=None):
+        base_block = next(iter(assets[chain.id][asset]))
+        if not base_block:
+            base_block = block
+
+        try:
+            asset_contract = contract(asset)
+            decimals = asset_contract.decimals()
+            ppfs = asset_contract.getPricePerFullShare(block_identifier=base_block) / 10**decimals
+            underlying = asset_contract.token()
+            want_price = magic.get_price(underlying, block=block)
+            return ppfs * want_price
+        except ValueError as e:
+            logger.error(e)
+            return None
+
+
+pps = None
+try:
+    pps = PricePerShare()
+except UnsupportedNetwork:
+    pass