"""Génération des feuilles de poste (PDF).

Module isolé, fonction pure (`generate_position_sheets_pdf`) : aucun accès
base ici — voir `app/api/position_sheets.py` pour l'assemblage des données.

Une page par poste et par jour, listant les créneaux du jour avec les
bénévoles affectés et leur téléphone — à imprimer et afficher sur place.
Complément des badges (`app/badges/pdf.py`) : un badge identifie un
bénévole, une feuille identifie un poste pour la journée.
"""

import datetime as dt
import io
from dataclasses import dataclass

from reportlab.lib import colors
from reportlab.lib.pagesizes import A4
from reportlab.lib.styles import ParagraphStyle, getSampleStyleSheet
from reportlab.lib.units import mm
from reportlab.platypus import (
    PageBreak,
    Paragraph,
    SimpleDocTemplate,
    Spacer,
    Table,
    TableStyle,
)

_WEEKDAYS_FR = ["Lundi", "Mardi", "Mercredi", "Jeudi", "Vendredi", "Samedi", "Dimanche"]
_MONTHS_FR = [
    "janvier", "février", "mars", "avril", "mai", "juin",
    "juillet", "août", "septembre", "octobre", "novembre", "décembre",
]


def _format_day_fr(date: dt.date) -> str:
    return f"{_WEEKDAYS_FR[date.weekday()]} {date.day} {_MONTHS_FR[date.month - 1]} {date.year}"


@dataclass(frozen=True)
class SheetVolunteer:
    name: str
    phone: str | None


@dataclass(frozen=True)
class SheetShift:
    starts_at: dt.datetime
    ends_at: dt.datetime
    min_staff: int
    ideal_staff: int
    volunteers: tuple[SheetVolunteer, ...]

    @property
    def understaffed(self) -> bool:
        return len(self.volunteers) < self.min_staff


@dataclass(frozen=True)
class PositionDaySheet:
    """Une page : un poste, un jour, ses créneaux triés chronologiquement."""

    position_name: str
    position_location: str | None
    date: dt.date
    shifts: tuple[SheetShift, ...]
    # None si le poste n'a pas (encore) de référent désigné
    # (`Position.lead_account_id`).
    referent_name: str | None = None
    referent_phone: str | None = None


def _styles() -> dict[str, ParagraphStyle]:
    base = getSampleStyleSheet()
    return {
        "title": ParagraphStyle(
            "SheetTitle", parent=base["Title"], alignment=0, fontSize=22, spaceAfter=2
        ),
        "subtitle": ParagraphStyle(
            "SheetSubtitle", parent=base["Normal"],
            fontSize=12, textColor=colors.grey, spaceAfter=4,
        ),
        "referent": ParagraphStyle(
            "SheetReferent", parent=base["Normal"],
            fontSize=11.5, fontName="Helvetica-Bold", spaceAfter=16,
        ),
        "shiftHeader": ParagraphStyle(
            "ShiftHeader", parent=base["Heading3"], fontSize=13, spaceBefore=12, spaceAfter=4
        ),
        "shiftHeaderWarning": ParagraphStyle(
            "ShiftHeaderWarning", parent=base["Heading3"],
            fontSize=13, spaceBefore=12, spaceAfter=4, textColor=colors.HexColor("#b23a1f"),
        ),
        "normal": base["Normal"],
    }


def _shift_table(shift: SheetShift) -> Table:
    rows = [["Bénévole", "Téléphone"]] + [
        [v.name, v.phone or "—"] for v in shift.volunteers
    ]
    table = Table(rows, colWidths=[110 * mm, 55 * mm])
    table.setStyle(
        TableStyle(
            [
                ("FONTNAME", (0, 0), (-1, 0), "Helvetica-Bold"),
                ("FONTSIZE", (0, 0), (-1, -1), 10.5),
                ("TOPPADDING", (0, 0), (-1, -1), 5),
                ("BOTTOMPADDING", (0, 0), (-1, -1), 5),
                ("LINEBELOW", (0, 0), (-1, 0), 0.75, colors.black),
                ("GRID", (0, 1), (-1, -1), 0.25, colors.lightgrey),
            ]
        )
    )
    return table


def generate_position_sheets_pdf(sheets: list[PositionDaySheet]) -> bytes:
    styles = _styles()
    buffer = io.BytesIO()
    doc = SimpleDocTemplate(
        buffer, pagesize=A4,
        leftMargin=18 * mm, rightMargin=18 * mm, topMargin=16 * mm, bottomMargin=16 * mm,
    )

    story = []
    for i, sheet in enumerate(sheets):
        if i > 0:
            story.append(PageBreak())
        story.append(Paragraph(sheet.position_name, styles["title"]))
        subtitle = _format_day_fr(sheet.date)
        if sheet.position_location:
            subtitle += f" — {sheet.position_location}"
        story.append(Paragraph(subtitle, styles["subtitle"]))

        if sheet.referent_name:
            referent_line = f"Référent : {sheet.referent_name}"
            if sheet.referent_phone:
                referent_line += f" — {sheet.referent_phone}"
            story.append(Paragraph(referent_line, styles["referent"]))
        else:
            story.append(Paragraph("Référent : à désigner", styles["referent"]))

        if not sheet.shifts:
            story.append(Paragraph("Aucun créneau ce jour-là.", styles["normal"]))
            continue

        for shift in sheet.shifts:
            header = (
                f"{shift.starts_at:%H:%M} – {shift.ends_at:%H:%M}"
                f"  ({len(shift.volunteers)}/{shift.ideal_staff})"
            )
            if shift.understaffed:
                header += "  ⚠ sous l'effectif minimal"
            style = styles["shiftHeaderWarning"] if shift.understaffed else styles["shiftHeader"]
            story.append(Paragraph(header, style))
            if shift.volunteers:
                story.append(_shift_table(shift))
            else:
                story.append(Paragraph("Personne affecté pour l'instant.", styles["normal"]))
        story.append(Spacer(1, 0))

    doc.build(story)
    return buffer.getvalue()