"""Daily paper-filing batch cover sheet + merged print job.

For the Standard (no-login) CMS filing path we batch all signed, not-yet-mailed
filings each postal working day and mail one Priority Mail envelope per
destination agency (the provider's MAC, or the NPI Enumerator in Fargo). This
module builds, for one destination/day:

  1. a **cover sheet** PDF — sender (Performance West), destination agency +
     address, batch date, enclosed count, and a per-item manifest
     (order# / provider / NPI / form type); and
  2. a **merged print job** PDF — the cover sheet followed by every enclosed
     signed filing, ready to print and drop in one envelope.

Only reportlab + pypdf are required (already used across document_gen).
"""
from __future__ import annotations

import io
import logging
from datetime import date

LOG = logging.getLogger("document_gen.batch_cover_sheet")

PW_SENDER = (
    "Performance West Inc.",
    "Provider Enrollment Filings",
    "filings@performancewest.net  |  (888) 411-0383",
)


def build_cover_sheet(
    *,
    destination_name: str,
    destination_address_lines: tuple[str, ...] | list[str],
    batch_date: date,
    items: list[dict],
) -> bytes:
    """Render the batch cover sheet PDF.

    ``items`` = list of dicts with keys: order_number, provider, npi, form.
    Returns PDF bytes.
    """
    from reportlab.lib.pagesizes import letter
    from reportlab.lib.units import inch
    from reportlab.lib.colors import HexColor
    from reportlab.pdfgen import canvas
    from reportlab.lib.utils import simpleSplit

    buf = io.BytesIO()
    c = canvas.Canvas(buf, pagesize=letter)
    w, h = letter
    teal = HexColor("#0f766e")
    gray = HexColor("#444444")
    x = inch
    y = h - inch

    # Header band
    c.setFillColor(teal)
    c.rect(0, h - 0.9 * inch, w, 0.9 * inch, fill=1, stroke=0)
    c.setFillColor(HexColor("#ffffff"))
    c.setFont("Helvetica-Bold", 18)
    c.drawString(x, h - 0.6 * inch, "Provider Enrollment Filing Transmittal")
    y = h - 1.3 * inch

    # Sender
    c.setFillColor(gray)
    c.setFont("Helvetica-Bold", 10)
    c.drawString(x, y, "FROM")
    y -= 14
    c.setFont("Helvetica", 10)
    for line in PW_SENDER:
        c.drawString(x, y, line)
        y -= 13
    y -= 8

    # Destination
    c.setFont("Helvetica-Bold", 10)
    c.drawString(x, y, "TO")
    y -= 14
    c.setFont("Helvetica", 10)
    c.drawString(x, y, destination_name)
    y -= 13
    for line in destination_address_lines:
        c.drawString(x, y, line)
        y -= 13
    y -= 8

    # Batch meta
    c.setFont("Helvetica-Bold", 10)
    c.drawString(x, y, f"Date: {batch_date.isoformat()}")
    c.drawString(x + 3 * inch, y, f"Enclosed filings: {len(items)}")
    y -= 22

    # Divider
    c.setStrokeColor(HexColor("#cccccc"))
    c.line(x, y, w - inch, y)
    y -= 18

    # Manifest header
    c.setFont("Helvetica-Bold", 9)
    cols = [(x, "ORDER"), (x + 1.4 * inch, "PROVIDER"),
            (x + 4.0 * inch, "NPI"), (x + 5.3 * inch, "FORM")]
    for cx, label in cols:
        c.drawString(cx, y, label)
    y -= 4
    c.line(x, y, w - inch, y)
    y -= 14

    c.setFont("Helvetica", 9)
    for it in items:
        if y < inch:  # new page
            c.showPage()
            y = h - inch
            c.setFont("Helvetica", 9)
        provider = (it.get("provider") or "")[:34]
        c.drawString(cols[0][0], y, str(it.get("order_number") or ""))
        c.drawString(cols[1][0], y, provider)
        c.drawString(cols[2][0], y, str(it.get("npi") or ""))
        c.drawString(cols[3][0], y, str(it.get("form") or "").upper())
        y -= 13

    # Footer note
    y = max(y - 20, 0.7 * inch)
    c.setFont("Helvetica-Oblique", 8)
    c.setFillColor(gray)
    note = ("This transmittal accompanies the signed provider enrollment "
            "applications enclosed. Each application bears the provider's "
            "certification signature. Questions: filings@performancewest.net.")
    for line in simpleSplit(note, "Helvetica-Oblique", 8, w - 2 * inch):
        c.drawString(x, y, line)
        y -= 11

    c.showPage()
    c.save()
    return buf.getvalue()


def merge_batch_pdf(cover_sheet: bytes, filing_pdfs: list[bytes]) -> bytes:
    """Merge the cover sheet + all enclosed signed filings into one print job."""
    from pypdf import PdfReader, PdfWriter

    writer = PdfWriter()
    writer.append(PdfReader(io.BytesIO(cover_sheet)))
    for pdf in filing_pdfs:
        try:
            writer.append(PdfReader(io.BytesIO(pdf)))
        except Exception as exc:  # one bad PDF shouldn't sink the batch
            LOG.error("[batch] skipping unreadable filing PDF: %s", exc)
    out = io.BytesIO()
    writer.write(out)
    return out.getvalue()