"""
Export Service — CSV, Excel, and PDF generation for transactions and reports.
Memory-efficient exports:
- CSV: streaming generator (rows written one at a time, never all in memory)
- Excel: openpyxl write-only mode + DB yield_per(500) avoids loading the full
result set into Python at once
"""
import io
import csv
from datetime import date
from flask import current_app
from app.models.transaction import Transaction
# ── CSV export ────────────────────────────────────────────────────────────────
def transactions_csv_stream(query):
"""
Generator that yields CSV text one row at a time.
Pass the SQLAlchemy *query* (not a list) — rows are fetched in 500-row batches.
Use with Flask's stream_with_context() for a true streaming response.
"""
buf = io.StringIO()
writer = csv.writer(buf)
writer.writerow(['Date', 'Type', 'Description', 'Category', 'Account', 'Amount', 'Notes'])
yield buf.getvalue()
buf.seek(0); buf.truncate()
for txn in query.yield_per(500):
writer.writerow([
txn.date.strftime('%Y-%m-%d'),
txn.transaction_type,
txn.description,
txn.category.name if txn.category else '',
txn.account.name if txn.account else '',
float(txn.amount),
txn.notes or '',
])
yield buf.getvalue()
buf.seek(0); buf.truncate()
# ── Excel export ──────────────────────────────────────────────────────────────
def transactions_to_excel(query, period_label='Transactions'):
"""
Return Excel bytes built from a SQLAlchemy *query* using openpyxl write-only
mode. Rows are fetched 500 at a time so the full result set is never held in
Python memory simultaneously.
"""
from openpyxl import Workbook
from openpyxl.styles import Font, PatternFill, Alignment
from openpyxl.cell import WriteOnlyCell
from openpyxl.utils import get_column_letter
symbol = current_app.config.get('APP_CURRENCY_SYMBOL', '$')
wb = Workbook(write_only=True)
ws = wb.create_sheet(title=period_label[:31])
col_widths = [12, 10, 40, 18, 18, 16, 30]
for i, w in enumerate(col_widths, 1):
ws.column_dimensions[get_column_letter(i)].width = w
header_fill = PatternFill(start_color='0F172A', end_color='0F172A', fill_type='solid')
header_font = Font(color='F1F5F9', bold=True, size=10)
headers = ['Date', 'Type', 'Description', 'Category', 'Account',
f'Amount ({symbol})', 'Notes']
header_row = []
for h in headers:
c = WriteOnlyCell(ws, value=h)
c.font = header_font
c.fill = header_fill
header_row.append(c)
ws.append(header_row)
income_fill = PatternFill(start_color='F0FDF4', end_color='F0FDF4', fill_type='solid')
expense_fill = PatternFill(start_color='FFF7F7', end_color='FFF7F7', fill_type='solid')
row_font = Font(size=10)
amt_fmt = '#,##0.00'
running_total = 0.0
for txn in query.yield_per(500):
fill = income_fill if txn.transaction_type == 'income' else expense_fill
amt = float(txn.amount)
running_total += amt
row_vals = [
txn.date.strftime('%Y-%m-%d'),
txn.transaction_type.title(),
txn.description,
txn.category.name if txn.category else '',
txn.account.name if txn.account else '',
amt,
txn.notes or '',
]
row = []
for col_idx, value in enumerate(row_vals, 1):
c = WriteOnlyCell(ws, value=value)
c.font = row_font
c.fill = fill
if col_idx == 6:
c.number_format = amt_fmt
c.alignment = Alignment(horizontal='right')
row.append(c)
ws.append(row)
# Totals row — plain cells (write-only, no random access)
total_lbl = WriteOnlyCell(ws, value='TOTAL')
total_lbl.font = Font(bold=True, size=10)
total_val = WriteOnlyCell(ws, value=running_total)
total_val.font = Font(bold=True, size=10)
total_val.number_format = amt_fmt
total_val.alignment = Alignment(horizontal='right')
ws.append(['', '', '', '', total_lbl, total_val, ''])
output = io.BytesIO()
wb.save(output)
output.seek(0)
return output.read()
# ── PDF export ────────────────────────────────────────────────────────────────
def report_to_pdf(html_content):
"""Convert HTML string to PDF bytes using WeasyPrint."""
try:
from weasyprint import HTML, CSS
pdf = HTML(string=html_content).write_pdf()
return pdf
except Exception as e:
import logging
logging.getLogger(__name__).error(f'[export] PDF generation failed: {e}')
return None
def build_report_html(report_data, report_type, currency_symbol='$'):
"""Build a clean HTML string for PDF export."""
today = date.today().strftime('%B %d, %Y')
period = report_data.get('period', '')
income = report_data.get('income', 0)
expense = report_data.get('expense', 0)
net = report_data.get('net', 0)
savings_rate = report_data.get('savings_rate', 0)
def fmt(v):
return f"{currency_symbol}{abs(float(v)):,.2f}"
# Expense categories table rows
cat_rows = ''
total_exp = sum(c['total'] for c in report_data.get('expense_categories', []))
for cat in report_data.get('expense_categories', []):
pct = round(cat['total'] / total_exp * 100, 1) if total_exp > 0 else 0
cat_rows += f'''
| {cat['name']} |
{fmt(cat['total'])} |
{pct}% |
'''
html = f'''
Personal Finance Report — {period}
Generated {today}
Savings Rate
{savings_rate}%
Expense Breakdown
| Category | Amount | % of Total |
|---|
{cat_rows or '| No expenses |
'}
'''
return html