From f690cd852401b038e1b2b1f61f10741c92a9911e Mon Sep 17 00:00:00 2001
From: Igor Kamyshev <igor@kamyshev.me>
Date: Sat, 2 Mar 2019 21:43:39 +0200
Subject: [PATCH] feat(converter): add more solidity to cinversation

---
 .../money/application/CurrencyConverter.ts    | 41 +++++++++++--------
 .../money/domain/ExchangeRateRepository.ts    | 11 +++++
 2 files changed, 36 insertions(+), 16 deletions(-)

diff --git a/back/src/money/application/CurrencyConverter.ts b/back/src/money/application/CurrencyConverter.ts
index fd848f35..01746ec5 100644
--- a/back/src/money/application/CurrencyConverter.ts
+++ b/back/src/money/application/CurrencyConverter.ts
@@ -7,6 +7,7 @@ import { Currency } from '@shared/enum/Currency'
 import { ExchangeRate } from '../domain/ExchangeRate.entity'
 import { ExchangeRateRepository } from '../domain/ExchangeRateRepository'
 import { ExchangeRateApi } from '../insfrastructure/ExchangeRateApi'
+import { Option } from 'tsoption'
 
 @Injectable()
 export class CurrencyConverter {
@@ -16,6 +17,14 @@ export class CurrencyConverter {
     private readonly entitySaver: EntitySaver,
   ) {}
 
+  public async convertApproximately(
+    from: Currency,
+    to: Currency,
+    amount: number,
+  ): Promise<number> {
+    return 0
+  }
+
   public async convert(
     from: Currency,
     to: Currency,
@@ -28,22 +37,22 @@ export class CurrencyConverter {
 
     const normalizedDate = startOfHour(when)
 
-    const rate = await this.getExchangeRate(from, to, normalizedDate).catch(
-      async e => {
-        // if correct rate getting failed, we can return the closest available rate
-        const closestRate = await this.exchangeRateRepo.findClosest(
-          from,
-          to,
-          normalizedDate,
-        )
-
-        if (closestRate.nonEmpty()) {
-          return closestRate.get().rate
-        }
-
-        throw e
-      },
-    )
+    const tryTo = (promiseRate: Promise<Option<ExchangeRate>>) => async (
+      e: Error,
+    ) => {
+      const optionalRate = await promiseRate
+
+      if (optionalRate.nonEmpty()) {
+        return optionalRate.get().rate
+      }
+
+      throw e
+    }
+
+    const rate = await this.getExchangeRate(from, to, normalizedDate)
+      .catch(tryTo(this.exchangeRateRepo.findClosest(from, to, normalizedDate)))
+      .catch(() => this.fetchExchangeRate(from, to, new Date()))
+      .catch(tryTo(this.exchangeRateRepo.findLast(from, to)))
 
     return Math.round(amount * rate)
   }
diff --git a/back/src/money/domain/ExchangeRateRepository.ts b/back/src/money/domain/ExchangeRateRepository.ts
index fb45ed74..2f6826f8 100644
--- a/back/src/money/domain/ExchangeRateRepository.ts
+++ b/back/src/money/domain/ExchangeRateRepository.ts
@@ -31,6 +31,17 @@ class ExchangeRateRepo {
       .then(this.toOption)
   }
 
+  public async findLast(
+    from: Currency,
+    to: Currency,
+  ): Promise<Option<ExchangeRate>> {
+    return this.createFromToQueryBuilder('rate')
+      .orderBy('rate.collectAt', 'DESC')
+      .setParameters({ from, to })
+      .getOne()
+      .then(this.toOption)
+  }
+
   public async findClosest(
     from: Currency,
     to: Currency,