1 files changed, 91 insertions, 0 deletions
diff --git a/packages/contract-wrappers/src/stores/balance_proxy_allowance_lazy_store.ts b/packages/contract-wrappers/src/stores/balance_proxy_allowance_lazy_store.ts
new file mode 100644
index 000000000..614195157
--- /dev/null
+++ b/packages/contract-wrappers/src/stores/balance_proxy_allowance_lazy_store.ts
@@ -0,0 +1,91 @@
+import { AbstractBalanceAndProxyAllowanceFetcher } from '@0xproject/order-utils';
+import { BlockParamLiteral } from '@0xproject/types';
+import { BigNumber } from '@0xproject/utils';
+import * as _ from 'lodash';
+
+import { TokenWrapper } from '../contract_wrappers/token_wrapper';
+
+/**
+ * Copy on read store for balances/proxyAllowances of tokens/accounts
+ */
+export class BalanceAndProxyAllowanceLazyStore implements AbstractBalanceAndProxyAllowanceFetcher {
+    private _tokenWrapper: TokenWrapper;
+    private _defaultBlock: BlockParamLiteral;
+    private _balance: {
+        [tokenAddress: string]: {
+            [userAddress: string]: BigNumber;
+        };
+    };
+    private _proxyAllowance: {
+        [tokenAddress: string]: {
+            [userAddress: string]: BigNumber;
+        };
+    };
+    constructor(token: TokenWrapper, defaultBlock: BlockParamLiteral) {
+        this._tokenWrapper = token;
+        this._defaultBlock = defaultBlock;
+        this._balance = {};
+        this._proxyAllowance = {};
+    }
+    public async getBalanceAsync(tokenAddress: string, userAddress: string): Promise<BigNumber> {
+        if (_.isUndefined(this._balance[tokenAddress]) || _.isUndefined(this._balance[tokenAddress][userAddress])) {
+            const methodOpts = {
+                defaultBlock: this._defaultBlock,
+            };
+            const balance = await this._tokenWrapper.getBalanceAsync(tokenAddress, userAddress, methodOpts);
+            this.setBalance(tokenAddress, userAddress, balance);
+        }
+        const cachedBalance = this._balance[tokenAddress][userAddress];
+        return cachedBalance;
+    }
+    public setBalance(tokenAddress: string, userAddress: string, balance: BigNumber): void {
+        if (_.isUndefined(this._balance[tokenAddress])) {
+            this._balance[tokenAddress] = {};
+        }
+        this._balance[tokenAddress][userAddress] = balance;
+    }
+    public deleteBalance(tokenAddress: string, userAddress: string): void {
+        if (!_.isUndefined(this._balance[tokenAddress])) {
+            delete this._balance[tokenAddress][userAddress];
+            if (_.isEmpty(this._balance[tokenAddress])) {
+                delete this._balance[tokenAddress];
+            }
+        }
+    }
+    public async getProxyAllowanceAsync(tokenAddress: string, userAddress: string): Promise<BigNumber> {
+        if (
+            _.isUndefined(this._proxyAllowance[tokenAddress]) ||
+            _.isUndefined(this._proxyAllowance[tokenAddress][userAddress])
+        ) {
+            const methodOpts = {
+                defaultBlock: this._defaultBlock,
+            };
+            const proxyAllowance = await this._tokenWrapper.getProxyAllowanceAsync(
+                tokenAddress,
+                userAddress,
+                methodOpts,
+            );
+            this.setProxyAllowance(tokenAddress, userAddress, proxyAllowance);
+        }
+        const cachedProxyAllowance = this._proxyAllowance[tokenAddress][userAddress];
+        return cachedProxyAllowance;
+    }
+    public setProxyAllowance(tokenAddress: string, userAddress: string, proxyAllowance: BigNumber): void {
+        if (_.isUndefined(this._proxyAllowance[tokenAddress])) {
+            this._proxyAllowance[tokenAddress] = {};
+        }
+        this._proxyAllowance[tokenAddress][userAddress] = proxyAllowance;
+    }
+    public deleteProxyAllowance(tokenAddress: string, userAddress: string): void {
+        if (!_.isUndefined(this._proxyAllowance[tokenAddress])) {
+            delete this._proxyAllowance[tokenAddress][userAddress];
+            if (_.isEmpty(this._proxyAllowance[tokenAddress])) {
+                delete this._proxyAllowance[tokenAddress];
+            }
+        }
+    }
+    public deleteAll(): void {
+        this._balance = {};
+        this._proxyAllowance = {};
+    }
+}