"""Write mileage itineraries to Excel workbooks.

This module uses :mod:`openpyxl` to construct a workbook with one sheet
per month. Each row corresponds to a single hop between recognised
sites. Columns follow the specification used by the EveryHR system:

* ``Date`` – calendar date in ISO format (YYYY-MM-DD).
* ``Purpose`` – free text summarising the journey, e.g. ``"Travel from
  Home to Lingwood Primary Academy 13.2mi"``.
* ``Miles`` – numeric value rounded to one decimal place.
* ``Vehicle`` – the vehicle descriptor configured for the user.
* ``Job Role`` – the job role of the user.
* ``From`` – friendly label of the origin site.
* ``To`` – friendly label of the destination site.
* ``Notes`` – blank for manual additions.

Rows are grouped by month (YYYY-MM). Each sheet is named after the
month and contains a header row followed by one row per hop in
chronological order.
"""

from __future__ import annotations

import os
from collections import defaultdict
from datetime import date
from typing import Dict, Iterable, List, Tuple

from openpyxl import Workbook
from openpyxl.utils import get_column_letter

from ..logic.detect_itinerary import Hop, SiteConfig


def build_monthly_rows(hops: Iterable[Hop], site_config: SiteConfig, distance_resolver) -> Dict[str, List[Tuple[str, str, float, str, str, str, str, str]]]:
    """Prepare rows grouped by month for Excel output.

    Parameters
    ----------
    hops : iterable of :class:`Hop`
        The hops produced by itinerary detection.
    site_config : :class:`SiteConfig`
        Used to look up friendly labels for canonical site names.
    distance_resolver : object
        An object with a ``resolve(origin_name, dest_name, origin_coords, dest_coords)``
        method that returns a distance in miles. See
        :class:`~mileage_logger.distance.resolve.DistanceResolver`.

    Returns
    -------
    dict mapping str -> list of tuples
        Keys are month strings in the form ``YYYY-MM``. Values are
        lists of tuples containing the data for each row: (date_str,
        purpose, miles, vehicle, job_role, from_label, to_label, notes).
    """

    rows_by_month: Dict[str, List[Tuple[str, str, float, str, str, str, str, str]]] = defaultdict(list)
    for hop in hops:
        month_key = hop.date.strftime("%Y-%m")  # Keep YYYY-MM for sheet naming
        origin_site = site_config.by_canonical.get(hop.origin)
        dest_site = site_config.by_canonical.get(hop.destination)
        if origin_site is None or dest_site is None:
            continue
        # Resolve distance
        dist = distance_resolver.resolve(
            hop.origin,
            hop.destination,
            (origin_site.lat, origin_site.lon),
            (dest_site.lat, dest_site.lon),
        )
        # Build purpose string
        purpose = f"Travel from {origin_site.label} to {dest_site.label} {dist:.1f}mi"
        rows_by_month[month_key].append(
            (
                hop.date.strftime("%d/%m/%Y"),  # Change date format here
                purpose,
                dist,
                distance_resolver.vehicle_label if hasattr(distance_resolver, "vehicle_label") else "SH11 DRV (Own 1.6CC Diesel Car/Van)",
                distance_resolver.job_role if hasattr(distance_resolver, "job_role") else "ICT Technician",
                origin_site.label,
                dest_site.label,
                "",
            )
        )

    return rows_by_month


def write_monthly_workbook(rows_by_month: Dict[str, List[Tuple[str, str, float, str, str, str, str, str]]], output_path: str) -> None:
    """Write the grouped rows into an Excel workbook.

    Parameters
    ----------
    rows_by_month : dict
        Mapping from month strings to lists of row tuples as returned
        by :func:`build_monthly_rows`.
    output_path : str
        Path of the Excel workbook to write. Any existing file will be
        overwritten.
    """

    wb = Workbook()
    # Remove the default sheet created by openpyxl
    default_sheet = wb.active
    wb.remove(default_sheet)
    for month, rows in sorted(rows_by_month.items()):
        ws = wb.create_sheet(title=month)
        # Write header
        header = ["Date", "Purpose", "Miles", "Vehicle", "Job Role", "From", "To", "Notes"]
        ws.append(header)
        for row in rows:
            ws.append(list(row))
        # Autosize columns (approximate)
        for col_idx in range(1, len(header) + 1):
            column_letter = get_column_letter(col_idx)
            max_length = max(
                len(str(ws.cell(row=r + 1, column=col_idx).value)) for r in range(len(rows) + 1)
            )
            # Add a little extra padding
            ws.column_dimensions[column_letter].width = max_length + 2
    # Ensure directory exists
    os.makedirs(os.path.dirname(output_path), exist_ok=True)
    wb.save(output_path)