#!/usr/bin/env python3
"""Generate a KBR4 invoice PDF for Audact AI Ltd."""

from __future__ import annotations

import os
import re
import sys
from dataclasses import dataclass
from datetime import date, datetime, timedelta
from pathlib import Path

from reportlab.lib.colors import HexColor, black, white
from reportlab.lib.pagesizes import A4
from reportlab.lib.utils import ImageReader
from reportlab.pdfgen import canvas


SUPPLIER = {
    "name": "Kompanija Broj 4 D.O.O.",
    "address_lines": ["Hakije Turajlica 2", "71000 Sarajevo", "Bosnia and Herzegovina"],
    "tax_id": "4202962240000",
    "vat_id": "202962240000",
}

CUSTOMER = {
    "name": "Audact AI Ltd",
    "address_lines": [
        "71-75 Shelton Street",
        "Covent Garden",
        "London WC2H 9JQ",
        "United Kingdom",
    ],
    "company_no": "17059133",
}

PAYMENT = {
    "iban": "BA391610000270960005",
    "swift": "RZBABA2S",
    "beneficiary_name": "KOMPANIJA BROJ 4 DOO SARAJEVO",
    "beneficiary_address": [
        "HAKIJE TURAJLICA BROJ 2",
        "71000 Sarajevo",
        "Bosnia and Herzegovina",
    ],
    "bank_name": "RAIFFEISEN BANK DD BOSNA I HERCEGOVINA",
    "bank_address": [
        "ZMAJA OD BOSNE BB",
        "71000 SARAJEVO",
        "Bosnia and Herzegovina",
    ],
}

LINE_ITEM_DESCRIPTION_LINES = [
    "Technical leadership and development services",
    "for the Audact platform",
]

ASSETS_DIR = Path(__file__).resolve().parent / "assets"
LOGO_PATH = ASSETS_DIR / "logo.png"

DARK = HexColor("#3F3F3F")
GRAY = HexColor("#7A7A7A")
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:
        return date.today()

    @property
    def due_date(self) -> date:
        d = self.issue_date
        added = 0
        while added < 5:
            d += timedelta(days=1)
            if d.weekday() < 5:
                added += 1
        return d


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(with_default(label, default)).strip()
        if not value and default is not None:
            return default
        if not value:
            print("  Value required.")
            continue
        if validator:
            err = validator(value)
            if err:
                print(f"  {err}")
                continue
        return value


def parse_date(s: str) -> date:
    for fmt in ("%Y-%m-%d", "%d.%m.%Y", "%d/%m/%Y"):
        try:
            return datetime.strptime(s, fmt).date()
        except ValueError:
            continue
    raise ValueError("expected YYYY-MM-DD, DD.MM.YYYY, or DD/MM/YYYY")


def prompt_date(label: str, default: date | None = None) -> date:
    while True:
        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, default: float | None = None) -> float:
    while True:
        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:
                raise ValueError
            return value
        except ValueError:
            print("  Enter a positive number, e.g. 7250 or 7250.00")


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)
    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)", 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)", default=default_end)
        if end < start:
            print("  End must be on or after start.")
            continue
        break
    number = prompt_str("Invoice number (e.g. 1a/2026)", default=next_invoice_number(past, end))
    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:
    return f"€{amount:,.2f}"


def fmt_date_long(d: date) -> str:
    return d.strftime("%b ") + str(d.day) + d.strftime(", %Y")


def fmt_date_dotted(d: date) -> str:
    return f"{d.day}.{d.month}.{d.year}."


def safe_filename(invoice_number: str) -> str:
    cleaned = invoice_number.replace("/", "_").replace("\\", "_").replace(" ", "_")
    return f"Invoice_{cleaned}.pdf"


def render_pdf(inv: InvoiceInputs, output_path: Path) -> None:
    page_w, page_h = A4
    c = canvas.Canvas(str(output_path), pagesize=A4)
    c.setTitle(f"Invoice {inv.number}")
    c.setAuthor(SUPPLIER["name"])

    margin_l = 50
    margin_r = page_w - 50

    y_top = page_h - 60

    if LOGO_PATH.exists():
        logo = ImageReader(str(LOGO_PATH))
        lw, lh = logo.getSize()
        target_w = 110
        target_h = target_w * lh / lw
        c.drawImage(
            logo,
            margin_l,
            y_top - target_h + 10,
            width=target_w,
            height=target_h,
            mask="auto",
            preserveAspectRatio=True,
        )

    c.setFillColor(DARK)
    c.setFont("Helvetica", 30)
    c.drawRightString(margin_r, y_top, "INVOICE")
    c.setFont("Helvetica", 11)
    c.setFillColor(GRAY)
    c.drawRightString(margin_r, y_top - 18, f"# {inv.number}")

    y = y_top - 35
    c.setFillColor(black)
    c.setFont("Helvetica-Bold", 10.5)
    c.drawString(margin_l, y, SUPPLIER["name"])
    c.setFont("Helvetica", 9.5)
    y -= 13
    for line in SUPPLIER["address_lines"]:
        c.drawString(margin_l, y, line)
        y -= 12
    c.drawString(margin_l, y, f"TAX ID: {SUPPLIER['tax_id']}")
    y -= 12
    c.drawString(margin_l, y, f"VAT ID: {SUPPLIER['vat_id']}")
    y -= 24

    bill_top = y
    c.setFillColor(GRAY)
    c.setFont("Helvetica", 9)
    c.drawString(margin_l, bill_top, "Bill To:")
    bill_y = bill_top - 13
    c.setFillColor(black)
    c.setFont("Helvetica-Bold", 10.5)
    c.drawString(margin_l, bill_y, CUSTOMER["name"])
    c.setFont("Helvetica", 9.5)
    bill_y -= 13
    for line in CUSTOMER["address_lines"]:
        c.drawString(margin_l, bill_y, line)
        bill_y -= 12
    c.drawString(margin_l, bill_y, f"Company No: {CUSTOMER['company_no']}")
    bill_y -= 12

    meta_label_x = margin_r - 110
    meta_value_x = margin_r
    meta_y = y_top - 60

    c.setFillColor(GRAY)
    c.setFont("Helvetica", 9.5)
    c.drawRightString(meta_label_x, meta_y, "Date:")
    c.setFillColor(black)
    c.drawRightString(meta_value_x, meta_y, fmt_date_long(inv.issue_date))

    meta_y -= 18
    c.setFillColor(GRAY)
    c.drawRightString(meta_label_x, meta_y, "Due Date:")
    c.setFillColor(black)
    c.drawRightString(meta_value_x, meta_y, fmt_date_long(inv.due_date))

    meta_y -= 22
    bal_box_h = 26
    bal_box_y = meta_y - bal_box_h + 14
    c.setFillColor(LIGHT_GRAY)
    c.rect(margin_r - 230, bal_box_y, 230, bal_box_h, stroke=0, fill=1)
    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.net_total))

    table_top = min(bill_y, bal_box_y) - 30
    row_h = 22

    header_y = table_top
    c.setFillColor(TABLE_HEAD)
    c.rect(margin_l, header_y - row_h + 6, margin_r - margin_l, row_h, stroke=0, fill=1)
    c.setFillColor(white)
    c.setFont("Helvetica", 10)
    item_x = margin_l + 8
    qty_right = margin_l + 320
    rate_right = margin_l + 410
    amount_right = margin_r - 8
    text_y = header_y - row_h + 12
    c.drawString(item_x, text_y, "Item")
    c.drawRightString(qty_right, text_y, "Quantity")
    c.drawRightString(rate_right, text_y, "Rate")
    c.drawRightString(amount_right, text_y, "Amount")

    weeks = inv.weeks
    rate = round(inv.total_amount / weeks, 2)
    amount = inv.total_amount

    row_y = header_y - row_h - 8
    c.setFillColor(black)
    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} 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:
        c.setFont("Helvetica-Bold", 10)
        c.setFillColor(black)
        for extra in LINE_ITEM_DESCRIPTION_LINES[1:]:
            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
    c.setFillColor(GRAY)
    c.setFont("Helvetica", 10)
    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%):")
    c.setFillColor(black)
    c.drawRightString(value_x, totals_y, fmt_money(0))
    totals_y -= 16
    c.setFillColor(GRAY)
    c.drawRightString(label_x, totals_y, "Total:")
    c.setFillColor(black)
    c.setFont("Helvetica-Bold", 10.5)
    c.drawRightString(value_x, totals_y, fmt_money(inv.net_total))

    notes_y = totals_y - 50
    c.setFillColor(GRAY)
    c.setFont("Helvetica", 9)
    c.drawString(margin_l, notes_y, "Notes:")
    notes_y -= 13
    c.setFillColor(black)
    c.setFont("Helvetica", 9.5)
    c.drawString(
        margin_l,
        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,
        notes_y,
        "VAT reverse charge - Article 196 of Council Directive 2006/112/EC.",
    )

    terms_y = notes_y - 24
    c.setFillColor(GRAY)
    c.setFont("Helvetica", 9)
    c.drawString(margin_l, terms_y, "Terms:")
    terms_y -= 13
    c.setFillColor(black)
    c.setFont("Helvetica", 9.5)
    c.drawString(margin_l, terms_y, "Pay by wire transfer:")
    terms_y -= 18
    c.drawString(margin_l, terms_y, f"IBAN CODE: {PAYMENT['iban']}")
    terms_y -= 12
    c.drawString(margin_l, terms_y, f"SWIFT CODE: {PAYMENT['swift']}")
    terms_y -= 18

    def draw_block(label: str, lines: list[str], y_start: int) -> int:
        c.setFillColor(GRAY)
        c.setFont("Helvetica", 9)
        c.drawString(margin_l, y_start, label)
        y_start -= 12
        c.setFillColor(black)
        c.setFont("Helvetica", 9.5)
        for ln in lines:
            c.drawString(margin_l, y_start, ln)
            y_start -= 12
        return y_start - 8

    terms_y = draw_block("Beneficary Name:", [PAYMENT["beneficiary_name"]], terms_y)
    terms_y = draw_block("Beneficary Address:", PAYMENT["beneficiary_address"], terms_y)
    terms_y = draw_block(
        "Beneficary Bank:",
        [PAYMENT["bank_name"], *PAYMENT["bank_address"]],
        terms_y,
    )

    c.showPage()
    c.save()


def main() -> int:
    folder = Path.cwd()
    try:
        inv = gather_inputs(folder)
    except (KeyboardInterrupt, EOFError):
        print()
        return 130

    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"  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


if __name__ == "__main__":
    sys.exit(main())