refactor(chart): Move functions to separate files or folders to improve code structure.

chart/function/create_chart.py

@@ -0,0 +1,54 @@
+from datetime import datetime
+
+from matplotlib import pyplot as plt
+
+from chart.function.gen_unique_name import generate_unique_name
+from ..database.server import create_pool
+
+async def create_chart(from_currency: str, conv_currency: str, start_date: str, end_date: str) -> (str, None):
+    pool = await create_pool()
+
+    start_date_obj = datetime.strptime(start_date, '%Y-%m-%d').date()
+    end_date_obj = datetime.strptime(end_date, '%Y-%m-%d').date()
+
+    async with pool.acquire() as conn:
+        data = await conn.fetch(
+            'SELECT date, rate FROM currency '
+            'WHERE (date BETWEEN $1 AND $2) AND from_currency = $3 AND conv_currency = $4',
+            start_date_obj,
+            end_date_obj,
+            from_currency.upper(),
+            conv_currency.upper()
+        )
+
+    if not data or len(data) <= 1:
+        return None
+
+    date, rate = [], []
+
+    for row in data:
+        date.append(str(row['date']))
+        rate.append(row['rate'])
+
+    if rate[0] < rate[-1]:
+        plt.plot(date, rate, color='green', marker='o')
+    elif rate[0] > rate[-1]:
+        plt.plot(date, rate, color='red', marker='o')
+    else:
+        plt.plot(date, rate, color='grey')
+
+    plt.xlabel('Date')
+    plt.ylabel('Rate')
+
+    fig = plt.gcf()
+    fig.set_size_inches(18.5, 9.5)
+
+    name = await generate_unique_name(
+        f'{from_currency.upper()}_{conv_currency.upper()}',
+        datetime.now()
+    )
+
+    fig.savefig(f'../charts/{name}.png')
+    fig.clear()
+
+    return name