Offer defaults from the latest invoice PDF and add days-off deduction

Parse existing Invoice_*.pdf files (PyMuPDF) for the invoice number and
"Work performed" period, then default the next period to the 14 days
after the latest one, the number to <month><letter>/<year> with the
letter incrementing within the month, and the amount to 7250 EUR.
Also add an optional days-off deduction at the derived daily rate and
ask before overwriting an existing PDF.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

invoicer.py

@@ -4,6 +4,7 @@
 from __future__ import annotations
 
 import os
+import re
 import sys
 from dataclasses import dataclass
 from datetime import date, datetime, timedelta
@@ -64,12 +65,110 @@ LIGHT_GRAY = HexColor("#EAEAEA")
 TABLE_HEAD = HexColor("#4A4A4A")
 
 
+WORKDAYS_PER_WEEK = 5
+PERIOD_DAYS = 14
+DEFAULT_AMOUNT = 7250.0
+INVOICE_GLOB = "Invoice_*.pdf"
+
+NUMBER_RE = re.compile(r"#\s*(\d+)([a-z])/(\d{4})")
+PERIOD_RE = re.compile(
+    r"Work performed from\s+(\d{1,2}\.\d{1,2}\.\d{4})\.?\s*-\s*(\d{1,2}\.\d{1,2}\.\d{4})\.?"
+)
+
+
+@dataclass
+class PastInvoice:
+    path: Path
+    month: int
+    letter: str
+    year: int
+    period_start: date
+    period_end: date
+
+    @property
+    def number(self) -> str:
+        return f"{self.month}{self.letter}/{self.year}"
+
+
+def read_pdf_text(path: Path) -> str:
+    import fitz  # PyMuPDF
+
+    with fitz.open(str(path)) as doc:
+        return "\n".join(page.get_text() for page in doc)
+
+
+def parse_invoice_pdf(path: Path) -> PastInvoice | None:
+    try:
+        text = read_pdf_text(path)
+    except Exception:
+        return None
+    num = NUMBER_RE.search(text)
+    per = PERIOD_RE.search(text)
+    if not num or not per:
+        return None
+    try:
+        start = parse_date(per.group(1))
+        end = parse_date(per.group(2))
+    except ValueError:
+        return None
+    return PastInvoice(
+        path=path,
+        month=int(num.group(1)),
+        letter=num.group(2),
+        year=int(num.group(3)),
+        period_start=start,
+        period_end=end,
+    )
+
+
+def load_past_invoices(folder: Path) -> list[PastInvoice]:
+    invoices = [parse_invoice_pdf(p) for p in folder.glob(INVOICE_GLOB)]
+    return sorted((i for i in invoices if i), key=lambda i: (i.period_end, i.path.stat().st_mtime))
+
+
+def latest_invoice(invoices: list[PastInvoice]) -> PastInvoice | None:
+    return invoices[-1] if invoices else None
+
+
+def next_invoice_number(invoices: list[PastInvoice], period_end: date) -> str:
+    """Number = <month of period end><letter>/<year>; letter increments within the month."""
+    letters = [
+        i.letter
+        for i in invoices
+        if i.month == period_end.month and i.year == period_end.year
+    ]
+    letter = chr(ord(max(letters)) + 1) if letters else "a"
+    return f"{period_end.month}{letter}/{period_end.year}"
+
+
 @dataclass
 class InvoiceInputs:
     number: str
     period_start: date
     period_end: date
     total_amount: float
+    days_off: int = 0
+
+    @property
+    def weeks(self) -> int:
+        days = (self.period_end - self.period_start).days + 1
+        return max(1, round(days / 7))
+
+    @property
+    def workdays(self) -> int:
+        return self.weeks * WORKDAYS_PER_WEEK
+
+    @property
+    def daily_rate(self) -> float:
+        return round(self.total_amount / self.workdays, 2)
+
+    @property
+    def days_off_amount(self) -> float:
+        return round(self.days_off * self.daily_rate, 2)
+
+    @property
+    def net_total(self) -> float:
+        return round(self.total_amount - self.days_off_amount, 2)
 
     @property
     def issue_date(self) -> date:
@@ -77,12 +176,24 @@ class InvoiceInputs:
 
     @property
     def due_date(self) -> date:
-        return self.issue_date + timedelta(days=5)
+        d = self.issue_date
+        added = 0
+        while added < 5:
+            d += timedelta(days=1)
+            if d.weekday() < 5:
+                added += 1
+        return d
 
 
-def prompt_str(label: str, validator=None) -> str:
+def with_default(label: str, default: str | None) -> str:
+    return f"{label} [{default}]: " if default is not None else f"{label}: "
+
+
+def prompt_str(label: str, validator=None, default: str | None = None) -> str:
     while True:
-        value = input(f"{label}: ").strip()
+        value = input(with_default(label, default)).strip()
+        if not value and default is not None:
+            return default
         if not value:
             print("  Value required.")
             continue
@@ -103,18 +214,23 @@ def parse_date(s: str) -> date:
     raise ValueError("expected YYYY-MM-DD, DD.MM.YYYY, or DD/MM/YYYY")
 
 
-def prompt_date(label: str) -> date:
+def prompt_date(label: str, default: date | None = None) -> date:
     while True:
-        raw = input(f"{label}: ").strip()
+        raw = input(with_default(label, default.isoformat() if default else None)).strip()
+        if not raw and default is not None:
+            return default
         try:
             return parse_date(raw)
         except ValueError as e:
             print(f"  {e}")
 
 
-def prompt_amount(label: str) -> float:
+def prompt_amount(label: str, default: float | None = None) -> float:
     while True:
-        raw = input(f"{label}: ").strip().replace(",", ".").replace("€", "").replace(" ", "")
+        shown = f"{default:g}" if default is not None else None
+        raw = input(with_default(label, shown)).strip().replace(",", ".").replace("€", "").replace(" ", "")
+        if not raw and default is not None:
+            return default
         try:
             value = float(raw)
             if value <= 0:
@@ -124,20 +240,60 @@ def prompt_amount(label: str) -> float:
             print("  Enter a positive number, e.g. 7250 or 7250.00")
 
 
-def gather_inputs() -> InvoiceInputs:
+def prompt_int(label: str, max_value: int | None = None, default: int | None = None) -> int:
+    while True:
+        raw = input(with_default(label, str(default) if default is not None else None)).strip()
+        if not raw and default is not None:
+            return default
+        try:
+            value = int(raw)
+            if value < 0:
+                raise ValueError
+        except ValueError:
+            print("  Enter a whole number, e.g. 0 or 2")
+            continue
+        if max_value is not None and value > max_value:
+            print(f"  Must be between 0 and {max_value}.")
+            continue
+        return value
+
+
+def gather_inputs(folder: Path) -> InvoiceInputs:
     print("KBR4 invoice generator — Audact AI Ltd")
     print("-" * 40)
-    number = prompt_str("Invoice number (e.g. 1/2026)")
+    past = load_past_invoices(folder)
+    last = latest_invoice(past)
+    default_start = default_end = None
+    if last:
+        print(
+            f"Last invoice: {last.number} ({last.path.name}), "
+            f"work performed {fmt_date_dotted(last.period_start)} - {fmt_date_dotted(last.period_end)}"
+        )
+        default_start = last.period_end + timedelta(days=1)
+        default_end = default_start + timedelta(days=PERIOD_DAYS - 1)
+    else:
+        print(f"No previous {INVOICE_GLOB} found in {folder}; no period/number defaults.")
     print("Invoice period (two-week range, in arrears):")
-    start = prompt_date("  Period start (YYYY-MM-DD)")
+    start = prompt_date("  Period start (YYYY-MM-DD)", default=default_start)
+    if default_end is not None and start != default_start:
+        default_end = start + timedelta(days=PERIOD_DAYS - 1)
     while True:
-        end = prompt_date("  Period end   (YYYY-MM-DD)")
+        end = prompt_date("  Period end   (YYYY-MM-DD)", default=default_end)
         if end < start:
             print("  End must be on or after start.")
             continue
         break
-    total = prompt_amount("Total amount in EUR")
+    number = prompt_str("Invoice number (e.g. 1a/2026)", default=next_invoice_number(past, end))
-    return InvoiceInputs(number=number, period_start=start, period_end=end, total_amount=total)
+    total = prompt_amount("Total amount in EUR", default=DEFAULT_AMOUNT)
+    inv = InvoiceInputs(number=number, period_start=start, period_end=end, total_amount=total)
+    print(
+        f"Period spans {inv.weeks} week(s) = {inv.workdays} workdays "
+        f"at {fmt_money(inv.daily_rate)}/day."
+    )
+    inv.days_off = prompt_int(
+        f"Days off in this period (0-{inv.workdays})", max_value=inv.workdays, default=0
+    )
+    return inv
 
 
 def fmt_money(amount: float) -> str:
@@ -244,7 +400,7 @@ def render_pdf(inv: InvoiceInputs, output_path: Path) -> None:
     c.setFillColor(black)
     c.setFont("Helvetica-Bold", 11)
     c.drawRightString(meta_label_x, meta_y, "Balance Due:")
-    c.drawRightString(meta_value_x, meta_y, fmt_money(inv.total_amount))
+    c.drawRightString(meta_value_x, meta_y, fmt_money(inv.net_total))
 
     table_top = min(bill_y, bal_box_y) - 30
     row_h = 22
@@ -264,7 +420,7 @@ def render_pdf(inv: InvoiceInputs, output_path: Path) -> None:
     c.drawRightString(rate_right, text_y, "Rate")
     c.drawRightString(amount_right, text_y, "Amount")
 
-    weeks = 2
+    weeks = inv.weeks
     rate = round(inv.total_amount / weeks, 2)
     amount = inv.total_amount
 
@@ -273,7 +429,7 @@ def render_pdf(inv: InvoiceInputs, output_path: Path) -> None:
     c.setFont("Helvetica-Bold", 10)
     c.drawString(item_x, row_y, LINE_ITEM_DESCRIPTION_LINES[0])
     c.setFont("Helvetica", 10)
-    c.drawRightString(qty_right, row_y, f"{weeks} weeks")
+    c.drawRightString(qty_right, row_y, f"{weeks} week{'s' if weeks != 1 else ''}")
     c.drawRightString(rate_right, row_y, fmt_money(rate))
     c.drawRightString(amount_right, row_y, fmt_money(amount))
     if len(LINE_ITEM_DESCRIPTION_LINES) > 1:
@@ -283,6 +439,22 @@ def render_pdf(inv: InvoiceInputs, output_path: Path) -> None:
             row_y -= 13
             c.drawString(item_x, row_y, extra)
 
+    if inv.days_off > 0:
+        row_y -= 24
+        day_word = "day" if inv.days_off == 1 else "days"
+        c.setFillColor(black)
+        c.setFont("Helvetica-Bold", 10)
+        c.drawString(item_x, row_y, "Days off")
+        c.setFont("Helvetica", 10)
+        c.setFillColor(GRAY)
+        c.drawString(item_x, row_y - 13, "Deduction for time not worked")
+        c.setFillColor(black)
+        c.setFont("Helvetica", 10)
+        c.drawRightString(qty_right, row_y, f"{inv.days_off} {day_word}")
+        c.drawRightString(rate_right, row_y, fmt_money(inv.daily_rate))
+        c.drawRightString(amount_right, row_y, f"-{fmt_money(inv.days_off_amount)}")
+        row_y -= 13
+
     totals_y = row_y - 50
     label_x = margin_r - 110
     value_x = margin_r
@@ -291,6 +463,12 @@ def render_pdf(inv: InvoiceInputs, output_path: Path) -> None:
     c.drawRightString(label_x, totals_y, "Subtotal:")
     c.setFillColor(black)
     c.drawRightString(value_x, totals_y, fmt_money(amount))
+    if inv.days_off > 0:
+        totals_y -= 16
+        c.setFillColor(GRAY)
+        c.drawRightString(label_x, totals_y, "Days off:")
+        c.setFillColor(black)
+        c.drawRightString(value_x, totals_y, f"-{fmt_money(inv.days_off_amount)}")
     totals_y -= 16
     c.setFillColor(GRAY)
     c.drawRightString(label_x, totals_y, "Tax (0%):")
@@ -301,7 +479,7 @@ def render_pdf(inv: InvoiceInputs, output_path: Path) -> None:
     c.drawRightString(label_x, totals_y, "Total:")
     c.setFillColor(black)
     c.setFont("Helvetica-Bold", 10.5)
-    c.drawRightString(value_x, totals_y, fmt_money(amount))
+    c.drawRightString(value_x, totals_y, fmt_money(inv.net_total))
 
     notes_y = totals_y - 50
     c.setFillColor(GRAY)
@@ -315,6 +493,14 @@ def render_pdf(inv: InvoiceInputs, output_path: Path) -> None:
         notes_y,
         f"Work performed from {fmt_date_dotted(inv.period_start)} - {fmt_date_dotted(inv.period_end)}",
     )
+    if inv.days_off > 0:
+        day_word = "day" if inv.days_off == 1 else "days"
+        notes_y -= 13
+        c.drawString(
+            margin_l,
+            notes_y,
+            f"{inv.days_off} {day_word} off deducted at {fmt_money(inv.daily_rate)}/day.",
+        )
     notes_y -= 13
     c.drawString(
         margin_l,
@@ -361,19 +547,28 @@ def render_pdf(inv: InvoiceInputs, output_path: Path) -> None:
 
 
 def main() -> int:
+    folder = Path.cwd()
     try:
-        inv = gather_inputs()
+        inv = gather_inputs(folder)
     except (KeyboardInterrupt, EOFError):
         print()
         return 130
 
-    output_path = Path.cwd() / safe_filename(inv.number)
+    output_path = folder / safe_filename(inv.number)
+    if output_path.exists():
+        answer = input(f"{output_path.name} already exists. Overwrite? [y/N]: ").strip().lower()
+        if answer not in ("y", "yes"):
+            print("Aborted.")
+            return 1
     render_pdf(inv, output_path)
     print()
     print(f"Wrote {output_path}")
     print(f"  Issue date: {fmt_date_long(inv.issue_date)}")
     print(f"  Due date:   {fmt_date_long(inv.due_date)}")
-    print(f"  Total:      {fmt_money(inv.total_amount)}")
+    print(f"  Subtotal:   {fmt_money(inv.total_amount)}")
+    if inv.days_off > 0:
+        print(f"  Days off:   {inv.days_off} (-{fmt_money(inv.days_off_amount)})")
+    print(f"  Total:      {fmt_money(inv.net_total)}")
     return 0