"""Excel export service for Berichtswesen files.

Generates .xlsx files in the exact format used by the DAK Zweitmeinungs-Portal
Berichtswesen, matching the structure of historical files (2023-2026).

The workbook contains 4 sheets:
  1. Auswertung KW gesamt     - Overall weekly summary + year comparison
  2. Auswertung nach Fachgebieten - Weekly breakdown by Fallgruppe
  3. Auswertung Gutachten     - Gutachten details (Alternative/Bestaetigung)
  4. Auswertung ICD onko      - ICD code frequency listing
"""

from __future__ import annotations

from io import BytesIO
from typing import Any

from openpyxl import Workbook
from openpyxl.styles import Alignment, Font, PatternFill
from openpyxl.utils import get_column_letter

# ---------------------------------------------------------------------------
# Styles matching the reference Berichtswesen files
# ---------------------------------------------------------------------------

# Header row fill: theme colour 0 with tint -0.15 (light grey).
# openpyxl cannot replicate theme-based tints portably, so we use a concrete
# grey that closely matches the rendered colour in the original files.
HEADER_FILL = PatternFill(start_color="FFD9D9D9", end_color="FFD9D9D9", fill_type="solid")
BOLD_FONT = Font(bold=True)
HEADER_FONT = Font(bold=True, name="Calibri", size=11)
TITLE_FONT = Font(bold=True, name="Calibri", size=12)
PCT_FORMAT = "0.0%"

# Fallgruppe keys in canonical order
FALLGRUPPEN = ["onko", "kardio", "intensiv", "galle", "sd"]
FALLGRUPPEN_LABELS = {
    "onko": "Fallgruppe onko",
    "kardio": "Fallgruppe kardio",
    "intensiv": "Fallgruppe intensiv",
    "galle": "Fallgruppe Gallenblase",
    "sd": "Fallgruppe Schilddr\u00fcse",
}

MAX_KW = 52  # always output 52 rows


def generate_berichtswesen_xlsx(
    report_data: dict[str, Any],
    jahr: int,
    vorjahr_data: dict[str, Any] | None = None,
) -> bytes:
    """Generate a Berichtswesen Excel file.

    Args:
        report_data: Output from ``report_service.generate_full_report()``.
            Expected keys: ``sheet1``, ``sheet2``, ``sheet3``, ``icd_codes``.
        jahr: The report year.
        vorjahr_data: Previous-year summary data for the year-over-year
            comparison block on Sheet 1.  Structure same as *report_data*
            ``sheet1`` (i.e. containing ``totals`` and ``weeks``).

    Returns:
        The ``.xlsx`` file contents as *bytes*.
    """
    wb = Workbook()

    _write_sheet1_kw_gesamt(wb, report_data.get("sheet1", {}), jahr, vorjahr_data)
    _write_sheet2_fachgebiete(wb, report_data.get("sheet2", {}), jahr)
    _write_sheet3_gutachten(wb, report_data.get("sheet3", {}), jahr)
    # ICD codes live inside sheet5
    sheet5 = report_data.get("sheet5", {})
    icd_codes = sheet5.get("icd_codes", []) if isinstance(sheet5, dict) else []
    _write_sheet4_icd_onko(wb, icd_codes, jahr)

    # Remove the default empty sheet created by Workbook()
    if "Sheet" in wb.sheetnames:
        del wb["Sheet"]

    buf = BytesIO()
    wb.save(buf)
    return buf.getvalue()


# ---------------------------------------------------------------------------
# Internal helpers
# ---------------------------------------------------------------------------

def _safe(val: Any, default: int = 0) -> int:
    """Return *val* as int, falling back to *default*."""
    if val is None:
        return default
    try:
        return int(val)
    except (TypeError, ValueError):
        return default


def _pct(numerator: int, denominator: int) -> float | None:
    """Return fraction or *None* if denominator is zero."""
    if denominator == 0:
        return None
    return numerator / denominator


def _apply_header_style(ws, row: int, min_col: int, max_col: int) -> None:
    """Apply header fill + bold font to a row range."""
    for col in range(min_col, max_col + 1):
        cell = ws.cell(row=row, column=col)
        cell.fill = HEADER_FILL
        cell.font = HEADER_FONT


def _auto_col_width(ws, min_col: int = 1, max_col: int | None = None, min_width: float = 8.0) -> None:
    """Set column widths based on content length, with a sensible minimum."""
    if max_col is None:
        max_col = ws.max_column or 1
    for col in range(min_col, max_col + 1):
        max_len = min_width
        col_letter = get_column_letter(col)
        for row in range(1, (ws.max_row or 1) + 1):
            val = ws.cell(row=row, column=col).value
            if val is not None:
                cell_len = len(str(val)) + 2
                if cell_len > max_len:
                    max_len = cell_len
        # Cap at reasonable width
        ws.column_dimensions[col_letter].width = min(max_len, 35)


def _weeks_lookup(weeks: list[dict]) -> dict[int, dict]:
    """Convert a list of week dicts to ``{kw: dict}`` for fast lookup."""
    return {w["kw"]: w for w in weeks} if weeks else {}


# ---------------------------------------------------------------------------
# Sheet 1: Auswertung KW gesamt
# ---------------------------------------------------------------------------

def _write_sheet1_kw_gesamt(
    wb: Workbook,
    data: dict[str, Any],
    jahr: int,
    vorjahr_data: dict[str, Any] | None,
) -> None:
    """Write the 'Auswertung KW gesamt' sheet.

    Layout (matching reference files):
      Row 1:  A1 = "Gesamtuebersicht"
      Row 2:  C2 = <jahr>,  E2 = <vorjahr>
      Row 3:  A3 = "Gesamtzahl an Erstberatungen", C3 = count, E3 = vorjahr
      Row 4:  A4 = "Anzahl Ablehnungen",           C4 = count, D4 = %, E4 = vorjahr, F4 = %
      Row 5:  A5 = "Anzahl versendeter Unterlagen", C5 = count, D5 = %, E5 = vorjahr, F5 = %
      Row 6:  A6 = "Anzahl keine Rueckmeldung",     C6 = count, D6 = %, E6 = vorjahr, F6 = %
      Row 7:  A7 = "Anzahl erstellter Gutachten",   C7 = count, D7 = %, E7 = vorjahr, F7 = %
      Row 8-9: (empty)
      Row 10: Column headers (KW | Erstberatungen | Unterlagen | Ablehnung | Keine Rueckmeldung | Gutachten)
      Row 11-62: KW 1-52 data
      Row 63: Summe row
    """
    ws = wb.create_sheet(title="Auswertung KW gesamt")

    totals = data.get("summary", {})
    weeks = _weeks_lookup(data.get("weekly", []))

    erst = _safe(totals.get("erstberatungen"))
    abl = _safe(totals.get("ablehnungen"))
    unt = _safe(totals.get("unterlagen"))
    keine_rm = _safe(totals.get("keine_rueckmeldung"))
    gutachten = _safe(totals.get("gutachten"))

    # Vorjahr totals
    vj = vorjahr_data or {}
    vj_totals = vj.get("summary", {}) if isinstance(vj, dict) else {}
    vj_erst = _safe(vj_totals.get("erstberatungen"))
    vj_abl = _safe(vj_totals.get("ablehnungen"))
    vj_unt = _safe(vj_totals.get("unterlagen"))
    vj_keine = _safe(vj_totals.get("keine_rueckmeldung"))
    vj_ga = _safe(vj_totals.get("gutachten"))

    # --- Title ---
    ws["A1"] = "Gesamt\u00fcbersicht"
    ws["A1"].font = TITLE_FONT

    # --- Year headers ---
    ws["C2"] = jahr
    ws["E2"] = jahr - 1

    # --- Summary rows ---
    summary_rows = [
        ("Gesamtzahl an Erstberatungen", erst, None, vj_erst, None),
        ("Anzahl Ablehnungen", abl, _pct(abl, erst), vj_abl, _pct(vj_abl, vj_erst)),
        ("Anzahl versendeter Unterlagen", unt, _pct(unt, erst), vj_unt, _pct(vj_unt, vj_erst)),
        ("Anzahl keine R\u00fcckmeldung", keine_rm, _pct(keine_rm, erst), vj_keine, _pct(vj_keine, vj_erst)),
        ("Anzahl erstellter Gutachten", gutachten, _pct(gutachten, erst), vj_ga, _pct(vj_ga, vj_erst)),
    ]
    for i, (label, val, pct, vj_val, vj_pct) in enumerate(summary_rows):
        row = 3 + i
        ws.cell(row=row, column=1, value=label)
        ws.cell(row=row, column=3, value=val)
        if pct is not None:
            c = ws.cell(row=row, column=4, value=pct)
            c.number_format = PCT_FORMAT
        if vj_val:
            ws.cell(row=row, column=5, value=vj_val)
        if vj_pct is not None:
            c = ws.cell(row=row, column=6, value=vj_pct)
            c.number_format = PCT_FORMAT

    # --- Column headers (row 10) ---
    headers = ["KW", "Anzahl an Erstberatungen", "Unterlagen", "Ablehnung", "Keine R\u00fcckmeldung", "Gutachten"]
    for ci, h in enumerate(headers, start=1):
        ws.cell(row=10, column=ci, value=h)
    _apply_header_style(ws, 10, 1, 6)

    # --- Weekly data (rows 11-62) ---
    for kw in range(1, MAX_KW + 1):
        row = 10 + kw  # row 11 = KW 1
        w = weeks.get(kw, {})
        ws.cell(row=row, column=1, value=kw)
        ws.cell(row=row, column=2, value=_safe(w.get("erstberatungen")))
        ws.cell(row=row, column=3, value=_safe(w.get("unterlagen")))
        ws.cell(row=row, column=4, value=_safe(w.get("ablehnungen")))
        ws.cell(row=row, column=5, value=_safe(w.get("keine_rm")))
        ws.cell(row=row, column=6, value=_safe(w.get("gutachten")))

    # --- Summe row (row 63) ---
    summe_row = 10 + MAX_KW + 1  # 63
    ws.cell(row=summe_row, column=1, value="Summe")
    ws.cell(row=summe_row, column=2, value=erst)
    ws.cell(row=summe_row, column=3, value=unt)
    ws.cell(row=summe_row, column=4, value=abl)
    ws.cell(row=summe_row, column=5, value=keine_rm)
    ws.cell(row=summe_row, column=6, value=gutachten)
    _apply_header_style(ws, summe_row, 1, 6)

    # --- Column widths ---
    ws.column_dimensions["A"].width = 10
    ws.column_dimensions["B"].width = 24
    ws.column_dimensions["C"].width = 12
    ws.column_dimensions["D"].width = 12
    ws.column_dimensions["E"].width = 20
    ws.column_dimensions["F"].width = 12


# ---------------------------------------------------------------------------
# Sheet 2: Auswertung nach Fachgebieten
# ---------------------------------------------------------------------------

def _write_sheet2_fachgebiete(
    wb: Workbook,
    data: dict[str, Any],
    jahr: int,
) -> None:
    """Write the 'Auswertung nach Fachgebieten' sheet.

    Layout:
      Row 1:  A1 = "Uebersicht nach Fallgruppen"
      Row 3:  Merged group headers (B3:D3, E3:G3, H3:J3, K3:M3, N3:P3)
      Row 4:  Sub-headers: KW | Anzahl | Gutachten | Keine RM/Ablehnung  (x5)
      Row 5-56: KW 1-52 data
      Row 57: Summe row
    """
    ws = wb.create_sheet(title="Auswertung nach Fachgebieten")

    weeks = _weeks_lookup(data.get("weekly", []))

    # --- Title ---
    ws["A1"] = "\u00dcbersicht nach Fallgruppen"
    ws["A1"].font = TITLE_FONT

    # --- Group headers (row 3) with merged cells ---
    group_start_cols = [2, 5, 8, 11, 14]  # B, E, H, K, N
    for fg_key, start_col in zip(FALLGRUPPEN, group_start_cols):
        label = FALLGRUPPEN_LABELS[fg_key]
        cell = ws.cell(row=3, column=start_col, value=label)
        cell.fill = HEADER_FILL
        cell.font = HEADER_FONT
        cell.alignment = Alignment(horizontal="center")
        # Merge across 3 columns
        end_col = start_col + 2
        ws.merge_cells(
            start_row=3, start_column=start_col,
            end_row=3, end_column=end_col,
        )
        # Apply fill to merged cells too
        for c in range(start_col, end_col + 1):
            ws.cell(row=3, column=c).fill = HEADER_FILL

    # --- Sub-headers (row 4) ---
    ws.cell(row=4, column=1, value="KW")
    for start_col in group_start_cols:
        ws.cell(row=4, column=start_col, value="Anzahl")
        ws.cell(row=4, column=start_col + 1, value="Gutachten")
        ws.cell(row=4, column=start_col + 2, value="Keine R\u00fcckmeldung/Ablehnung")
    _apply_header_style(ws, 4, 1, 16)

    # --- Weekly data (rows 5-56) ---
    sums = {fg: {"anzahl": 0, "gutachten": 0, "keine_rm": 0} for fg in FALLGRUPPEN}

    for kw in range(1, MAX_KW + 1):
        row = 4 + kw  # row 5 = KW 1
        w = weeks.get(kw, {})
        ws.cell(row=row, column=1, value=kw)

        for fg_key, start_col in zip(FALLGRUPPEN, group_start_cols):
            fg_data = w.get(fg_key, {})
            anz = _safe(fg_data.get("anzahl"))
            ga = _safe(fg_data.get("gutachten"))
            keine = _safe(fg_data.get("keine_rm"))

            ws.cell(row=row, column=start_col, value=anz)
            ws.cell(row=row, column=start_col + 1, value=ga)
            ws.cell(row=row, column=start_col + 2, value=keine)

            sums[fg_key]["anzahl"] += anz
            sums[fg_key]["gutachten"] += ga
            sums[fg_key]["keine_rm"] += keine

    # --- Summe row (row 57) ---
    summe_row = 4 + MAX_KW + 1  # 57
    for fg_key, start_col in zip(FALLGRUPPEN, group_start_cols):
        ws.cell(row=summe_row, column=start_col, value=sums[fg_key]["anzahl"])
        ws.cell(row=summe_row, column=start_col + 1, value=sums[fg_key]["gutachten"])
        ws.cell(row=summe_row, column=start_col + 2, value=sums[fg_key]["keine_rm"])
    _apply_header_style(ws, summe_row, 1, 16)

    # --- Column widths ---
    ws.column_dimensions["A"].width = 6
    for start_col in group_start_cols:
        ws.column_dimensions[get_column_letter(start_col)].width = 8
        ws.column_dimensions[get_column_letter(start_col + 1)].width = 10
        ws.column_dimensions[get_column_letter(start_col + 2)].width = 14


# ---------------------------------------------------------------------------
# Sheet 3: Auswertung Gutachten
# ---------------------------------------------------------------------------

def _write_sheet3_gutachten(
    wb: Workbook,
    data: dict[str, Any],
    jahr: int,
) -> None:
    """Write the 'Auswertung Gutachten' sheet.

    Layout:
      Row 1:  A1 = "Uebersicht nach Fallgruppen"
      Row 3:  Group headers: Gesamt (B3) + 5 Fallgruppen
      Row 4:  Sub-headers: KW | Gutachten | Alternative | Bestaetigung  (x6)
      Row 5-56: KW 1-52 data
      Row 57: Summe row
    """
    ws = wb.create_sheet(title="Auswertung Gutachten")

    weeks = _weeks_lookup(data.get("weekly", []))

    # --- Title ---
    ws["A1"] = "\u00dcbersicht nach Fallgruppen"
    ws["A1"].font = TITLE_FONT

    # --- Group headers (row 3) ---
    # Gesamt: B3 (no merge since it's a single-column-start group header,
    # but in the reference the Gesamt label sits in B3 without a merge)
    cell = ws.cell(row=3, column=2, value="Gesamt")
    cell.fill = HEADER_FILL
    cell.font = HEADER_FONT
    cell.alignment = Alignment(horizontal="center")

    # Fallgruppen start at columns E, H, K, N, Q (each 3 cols wide)
    fg_start_cols = [5, 8, 11, 14, 17]
    for fg_key, start_col in zip(FALLGRUPPEN, fg_start_cols):
        label = FALLGRUPPEN_LABELS[fg_key]
        cell = ws.cell(row=3, column=start_col, value=label)
        cell.fill = HEADER_FILL
        cell.font = HEADER_FONT
        cell.alignment = Alignment(horizontal="center")
        # Merge: the reference merges first 2 of 3 columns (E3:F3, H3:I3, etc.)
        end_col = start_col + 1
        ws.merge_cells(
            start_row=3, start_column=start_col,
            end_row=3, end_column=end_col,
        )
        for c in range(start_col, end_col + 1):
            ws.cell(row=3, column=c).fill = HEADER_FILL

    # --- Sub-headers (row 4) ---
    ws.cell(row=4, column=1, value="KW")

    # Gesamt columns: B=Gutachten, C=Alternative, D=Bestaetigung
    ws.cell(row=4, column=2, value="Gutachten")
    ws.cell(row=4, column=3, value="Alternative")
    ws.cell(row=4, column=4, value="Best\u00e4tigung")

    for start_col in fg_start_cols:
        ws.cell(row=4, column=start_col, value="Gutachten")
        ws.cell(row=4, column=start_col + 1, value="Alternative")
        ws.cell(row=4, column=start_col + 2, value="Best\u00e4tigung")
    _apply_header_style(ws, 4, 1, 19)

    # --- Weekly data (rows 5-56) ---
    sums_gesamt = {"gutachten": 0, "alternative": 0, "bestaetigung": 0}
    sums_fg = {fg: {"gutachten": 0, "alternative": 0, "bestaetigung": 0} for fg in FALLGRUPPEN}

    for kw in range(1, MAX_KW + 1):
        row = 4 + kw
        w = weeks.get(kw, {})
        ws.cell(row=row, column=1, value=kw)

        # Gesamt
        gesamt = w.get("gesamt", {})
        g_ges = _safe(gesamt.get("gutachten"))
        g_alt = _safe(gesamt.get("alternative"))
        g_best = _safe(gesamt.get("bestaetigung"))
        ws.cell(row=row, column=2, value=g_ges)
        ws.cell(row=row, column=3, value=g_alt)
        ws.cell(row=row, column=4, value=g_best)
        sums_gesamt["gutachten"] += g_ges
        sums_gesamt["alternative"] += g_alt
        sums_gesamt["bestaetigung"] += g_best

        # Per Fallgruppe
        for fg_key, start_col in zip(FALLGRUPPEN, fg_start_cols):
            fg_data = w.get(fg_key, {})
            ga = _safe(fg_data.get("gutachten"))
            alt = _safe(fg_data.get("alternative"))
            best = _safe(fg_data.get("bestaetigung"))
            ws.cell(row=row, column=start_col, value=ga)
            ws.cell(row=row, column=start_col + 1, value=alt)
            ws.cell(row=row, column=start_col + 2, value=best)
            sums_fg[fg_key]["gutachten"] += ga
            sums_fg[fg_key]["alternative"] += alt
            sums_fg[fg_key]["bestaetigung"] += best

    # --- Summe row (row 57) ---
    summe_row = 4 + MAX_KW + 1
    ws.cell(row=summe_row, column=2, value=sums_gesamt["gutachten"])
    ws.cell(row=summe_row, column=3, value=sums_gesamt["alternative"])
    ws.cell(row=summe_row, column=4, value=sums_gesamt["bestaetigung"])
    for fg_key, start_col in zip(FALLGRUPPEN, fg_start_cols):
        ws.cell(row=summe_row, column=start_col, value=sums_fg[fg_key]["gutachten"])
        ws.cell(row=summe_row, column=start_col + 1, value=sums_fg[fg_key]["alternative"])
        ws.cell(row=summe_row, column=start_col + 2, value=sums_fg[fg_key]["bestaetigung"])
    _apply_header_style(ws, summe_row, 1, 19)

    # --- Column widths ---
    ws.column_dimensions["A"].width = 6
    for col in range(2, 20):
        ws.column_dimensions[get_column_letter(col)].width = 12


# ---------------------------------------------------------------------------
# Sheet 4: Auswertung ICD onko
# ---------------------------------------------------------------------------

def _write_sheet4_icd_onko(
    wb: Workbook,
    icd_data: list[dict[str, Any]],
    jahr: int,
) -> None:
    """Write the 'Auswertung ICD onko' sheet.

    Layout:
      Row 1:  A1 = "ICD", B1 = "Anzahl von ICD"
      Row 2:  A2 = "ICD", B2 = "AnzahlvonICD"  (pivot-table artefact in originals)
      Row 3+: ICD code | count  (sorted by count descending)
    """
    ws = wb.create_sheet(title="Auswertung ICD onko")

    # Header row (matches reference format exactly)
    ws["A1"] = "ICD"
    ws["B1"] = "Anzahl von ICD"
    ws["A1"].font = HEADER_FONT
    ws["B1"].font = HEADER_FONT

    # Second "header" row (artefact from pivot table in originals)
    ws["A2"] = "ICD"
    ws["B2"] = "AnzahlvonICD"

    # Sort by count descending
    sorted_icd = sorted(icd_data, key=lambda x: _safe(x.get("count")), reverse=True)

    for i, entry in enumerate(sorted_icd):
        row = 3 + i
        ws.cell(row=row, column=1, value=entry.get("icd", ""))
        ws.cell(row=row, column=2, value=_safe(entry.get("count")))

    # Column widths
    ws.column_dimensions["A"].width = 12
    ws.column_dimensions["B"].width = 16