Refactor invoice generation into reusable sections

src/invoice.py

@@ -83,24 +83,12 @@ def _profile_sections(profile):
             [line for line in to_info if line.strip()])
 
 
-def generate_invoice(buffer, invoice_data):
-    """Create the PDF invoice into ``buffer``."""
-    doc = SimpleDocTemplate(
-        buffer,
-        pagesize=LETTER,
-        rightMargin=40,
-        leftMargin=40,
-        topMargin=40,
-        bottomMargin=40,
-    )
-    styles = getSampleStyleSheet()
-    styles.add(ParagraphStyle(name="RightAlign", parent=styles["Normal"], alignment=TA_RIGHT))
-    styles.add(ParagraphStyle(name="Heading", parent=styles["Heading1"], fontSize=16, spaceAfter=10))
-    styles.add(ParagraphStyle(name="SubHeading", parent=styles["Heading2"], fontSize=12, spaceAfter=8))
-
-    elements = []
-    elements.append(Paragraph("Recharge Services Invoice", styles["Heading"]))
-    elements.append(Spacer(1, 12))
+def _header_elements(invoice_data, styles):
+    """Return flowables for the invoice header section."""
+    elements = [
+        Paragraph("Recharge Services Invoice", styles["Heading"]),
+        Spacer(1, 12),
+    ]
 
     header_table_data = [
         [
@@ -113,8 +101,7 @@ def generate_invoice(buffer, invoice_data):
         ],
     ]
     header_table = Table(header_table_data, colWidths=[250, 250])
-    elements.append(header_table)
-    elements.append(Spacer(1, 20))
+    elements.extend([header_table, Spacer(1, 20)])
 
     elements.append(Paragraph("<b>From (Billed By)</b>", styles["SubHeading"]))
     for line in invoice_data["from_info"]:
@@ -126,7 +113,12 @@ def generate_invoice(buffer, invoice_data):
         elements.append(Paragraph(line, styles["Normal"]))
     elements.append(Spacer(1, 20))
 
-    elements.append(Paragraph("<b>Invoice Summary</b>", styles["SubHeading"]))
+    return elements
+
+
+def _table_elements(invoice_data, styles):
+    """Return flowables for the invoice summary table."""
+    elements = [Paragraph("<b>Invoice Summary</b>", styles["SubHeading"])]
     table_data = [["Description", "Billing Period", "Qty / Units", "Rate", "Amount"]]
     for item in invoice_data["items"]:
         table_data.append(
@@ -155,18 +147,21 @@ def generate_invoice(buffer, invoice_data):
             ]
         )
     )
-    elements.append(table)
-    elements.append(Spacer(1, 20))
+    elements.extend([table, Spacer(1, 20)])
+    return elements
 
-    elements.append(Paragraph("Payment Instructions", styles["SubHeading"]))
+
+def _note_elements(invoice_data, styles):
+    """Return flowables for payment instructions and notes."""
+    elements = [Paragraph("Payment Instructions", styles["SubHeading"])]
     for line in invoice_data["bank_info"]:
         elements.append(Paragraph(line, styles["Normal"]))
     elements.append(Spacer(1, 20))
 
     elements.append(Paragraph("Notes", styles["SubHeading"]))
     elements.append(Paragraph(invoice_data["notes"], styles["Normal"]))
-
     elements.append(Spacer(1, 20))
+
     elements.append(
         Paragraph(
             "Generated by Recharge Management System on "
@@ -175,6 +170,28 @@ def generate_invoice(buffer, invoice_data):
             styles["Normal"],
         )
     )
+    return elements
+
+
+def generate_invoice(buffer, invoice_data):
+    """Create the PDF invoice into ``buffer``."""
+    doc = SimpleDocTemplate(
+        buffer,
+        pagesize=LETTER,
+        rightMargin=40,
+        leftMargin=40,
+        topMargin=40,
+        bottomMargin=40,
+    )
+    styles = getSampleStyleSheet()
+    styles.add(ParagraphStyle(name="RightAlign", parent=styles["Normal"], alignment=TA_RIGHT))
+    styles.add(ParagraphStyle(name="Heading", parent=styles["Heading1"], fontSize=16, spaceAfter=10))
+    styles.add(ParagraphStyle(name="SubHeading", parent=styles["Heading2"], fontSize=12, spaceAfter=8))
+
+    elements = []
+    elements.extend(_header_elements(invoice_data, styles))
+    elements.extend(_table_elements(invoice_data, styles))
+    elements.extend(_note_elements(invoice_data, styles))
 
     doc.build(elements)