1 files changed, 82 insertions, 0 deletions
diff --git a/packages/0x.js/src/stores/balance_proxy_allowance_lazy_store.ts b/packages/0x.js/src/stores/balance_proxy_allowance_lazy_store.ts
new file mode 100644
index 000000000..c83e61606
--- /dev/null
+++ b/packages/0x.js/src/stores/balance_proxy_allowance_lazy_store.ts
@@ -0,0 +1,82 @@
+import * as _ from 'lodash';
+import * as Web3 from 'web3';
+import {BigNumber} from 'bignumber.js';
+import {TokenWrapper} from '../contract_wrappers/token_wrapper';
+import {BlockParamLiteral} from '../types';
+
+/**
+ * Copy on read store for balances/proxyAllowances of tokens/accounts
+ */
+export class BalanceAndProxyAllowanceLazyStore {
+    private token: TokenWrapper;
+    private balance: {
+        [tokenAddress: string]: {
+            [userAddress: string]: BigNumber,
+        },
+    };
+    private proxyAllowance: {
+        [tokenAddress: string]: {
+            [userAddress: string]: BigNumber,
+        },
+    };
+    constructor(token: TokenWrapper) {
+        this.token = token;
+        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: BlockParamLiteral.Pending,
+            };
+            const balance = await this.token.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: BlockParamLiteral.Pending,
+            };
+            const proxyAllowance = await this.token.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 = {};
+    }
+}