Create app/chart_generator.py

app/chart_generator.py

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+"""
+Generates and visualizes market data charts correlated with news events.
+"""
+import io
+import base64
+import pandas as pd
+import matplotlib.pyplot as plt
+import matplotlib.dates as mdates
+
+def generate_price_chart(price_data: list, event_timestamp: pd.Timestamp, entity: str) -> str:
+    """
+    Generates a base64-encoded price chart image with an event annotation.
+
+    Args:
+        price_data: A list of [timestamp, price] pairs from CoinGecko.
+        event_timestamp: The timestamp of the news event.
+        entity: The cryptocurrency entity (e.g., 'Bitcoin').
+
+    Returns:
+        A base64 encoded string of the PNG chart image.
+    """
+    if not price_data:
+        return ""
+
+    # Use a dark theme for the chart
+    plt.style.use('dark_background')
+    
+    # Create a pandas DataFrame
+    df = pd.DataFrame(price_data, columns=['timestamp', 'price'])
+    df['timestamp'] = pd.to_datetime(df['timestamp'], unit='ms')
+    df = df.set_index('timestamp')
+
+    fig, ax = plt.subplots(figsize=(10, 4))
+    
+    # Plot the price data
+    ax.plot(df.index, df['price'], color='cyan', linewidth=2)
+
+    # Annotate the event
+    try:
+        event_price = df.asof(event_timestamp)['price']
+        ax.axvline(event_timestamp, color='red', linestyle='--', linewidth=1.5, label=f'Event: {entity}')
+        ax.plot(event_timestamp, event_price, 'ro', markersize=8) # Red dot on the event
+        ax.annotate(f'Event',
+                    xy=(event_timestamp, event_price),
+                    xytext=(event_timestamp, event_price * 1.01),
+                    ha='center',
+                    arrowprops=dict(facecolor='white', shrink=0.05, width=1, headwidth=4),
+                    bbox=dict(boxstyle='round,pad=0.3', fc='yellow', ec='k', lw=1, alpha=0.8),
+                    color='black'
+                   )
+    except KeyError:
+        # Event timestamp might be out of range
+        ax.axvline(event_timestamp, color='red', linestyle='--', linewidth=1.5)
+
+    # Formatting the chart
+    ax.set_title(f'{entity.upper()} Price Action around Event', fontsize=14)
+    ax.set_ylabel('Price (USD)')
+    ax.grid(True, linestyle='--', alpha=0.3)
+    fig.autofmt_xdate()
+    ax.xaxis.set_major_formatter(mdates.DateFormatter('%H:%M'))
+    ax.tick_params(axis='x', rotation=45)
+    plt.tight_layout()
+
+    # Save to an in-memory buffer
+    buf = io.BytesIO()
+    fig.savefig(buf, format='png', transparent=True)
+    buf.seek(0)
+    img_base64 = base64.b64encode(buf.read()).decode('utf-8')
+    plt.close(fig)
+
+    return f"data:image/png;base64,{img_base64}"