"""Excel-Export der Auswertung (mehrere Tabellenblätter)."""
import io
import json

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

from . import analytics, db

HEAD_FILL = PatternFill("solid", fgColor="0B6E4F")
HEAD_FONT = Font(color="FFFFFF", bold=True)


def _style_header(ws, ncols):
    for c in range(1, ncols + 1):
        cell = ws.cell(row=1, column=c)
        cell.fill = HEAD_FILL
        cell.font = HEAD_FONT
        cell.alignment = Alignment(vertical="center")
    ws.freeze_panes = "A2"


def _autosize(ws, max_width=60):
    for col in ws.columns:
        length = max((len(str(c.value)) for c in col if c.value is not None), default=8)
        ws.column_dimensions[get_column_letter(col[0].column)].width = min(length + 2, max_width)


def build_workbook(period_days=None) -> bytes:
    m = analytics.compute(period_days)
    h = m["humanize"]
    wb = Workbook()

    # --- KPIs ---
    ws = wb.active
    ws.title = "KPIs"
    ws.append(["Kennzahl", "Wert"])
    rows = [
        ("Tickets gesamt", m["total"]),
        ("offen", m["open"]),
        ("geschlossen", m["closed"]),
        ("eskaliert", m["escalated"]),
        ("Ø Reaktionszeit", h(m["response"]["avg"])),
        ("Median Reaktionszeit", h(m["response"]["median"])),
        ("Ø Lösungszeit", h(m["resolution"]["avg"])),
        ("Median Lösungszeit", h(m["resolution"]["median"])),
        ("Ø Alter offener Tickets (Tage)",
         round(m["open_age_avg_days"], 1) if m["open_age_avg_days"] else "–"),
    ]
    for r in rows:
        ws.append(list(r))
    _style_header(ws, 2)
    _autosize(ws)

    # --- Verteilungen ---
    ws = wb.create_sheet("Verteilungen")
    ws.append(["Kategorie", "Wert", "Anzahl"])
    for label, data in (("Status", m["by_state"]), ("Priorität", m["by_priority"]),
                        ("Gruppe", m["by_group"]), ("Bearbeiter", m["by_owner"])):
        for key, cnt in data:
            ws.append([label, key, cnt])
    _style_header(ws, 3)
    _autosize(ws)

    # --- Monatswerte ---
    ws = wb.create_sheet("Monatswerte")
    ws.append(["Monat", "erstellt", "geschlossen"])
    for row in m["monthly"]:
        ws.append([row["month"], row["created"], row["closed"]])
    _style_header(ws, 3)
    _autosize(ws)

    # --- Tickets ---
    ws = wb.create_sheet("Tickets")
    cols = ["Nummer", "Titel", "Status", "Priorität", "Gruppe", "Bearbeiter",
            "Artikel", "erstellt", "1. Reaktion", "geschlossen", "zuletzt geändert"]
    ws.append(cols)
    with db.get_conn() as conn:
        for r in conn.execute("SELECT raw_json FROM tickets ORDER BY zammad_updated_at DESC"):
            t = json.loads(r["raw_json"])
            ws.append([
                t.get("number"), t.get("title"), t.get("state"), t.get("priority"),
                t.get("group"), t.get("owner"), t.get("article_count"),
                _d(t.get("created_at")), _d(t.get("first_response_at")),
                _d(t.get("last_close_at")), _d(t.get("updated_at")),
            ])
    _style_header(ws, len(cols))
    _autosize(ws)

    # --- Änderungen ---
    ws = wb.create_sheet("Änderungen")
    ws.append(["Zeitpunkt", "Ticket", "Titel", "Feld", "alt", "neu", "Detail"])
    with db.get_conn() as conn:
        for c in conn.execute(
            "SELECT detected_at, ticket_number, ticket_title, label, old_value, "
            "new_value, detail FROM changes ORDER BY detected_at DESC LIMIT 5000"
        ):
            ws.append([_d(c["detected_at"]), c["ticket_number"], c["ticket_title"],
                       c["label"], c["old_value"], c["new_value"], c["detail"]])
    _style_header(ws, 7)
    _autosize(ws)

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


def _d(value):
    if not value:
        return ""
    return str(value).replace("T", " ")[:16]