"""Render ``.xlsx`` workbooks as HTML tables for the viewer (#xlsx).

Read-only: formulas are shown as their text (``data_only=False``) so a
round-trip through the viewer never depends on Excel's cached values.
Write-side lives in ``backend.services.mutations.edit_xlsx_cells``.
"""

from __future__ import annotations

import html
from datetime import date, datetime
from pathlib import Path
from typing import Any

from openpyxl import load_workbook
from openpyxl.utils import get_column_letter

# ponytail: hard caps bound the rendered grid (500 rows x 40 cols per sheet).
# Raise them, or paginate per sheet, if a real workbook needs more.
MAX_ROWS = 500
MAX_COLS = 40


def _fmt(value: Any) -> str:
    if value is None:
        return ""
    if isinstance(value, datetime):
        return value.strftime("%Y-%m-%d %H:%M")
    if isinstance(value, date):
        return value.isoformat()
    return str(value)


def _trim(grid: list[list[str]]) -> list[list[str]]:
    """Drop trailing empty rows and columns (openpyxl pads to max_col)."""
    while grid and not any(grid[-1]):
        grid.pop()
    if not grid:
        return grid
    width = 0
    for row in grid:
        for i in range(len(row) - 1, -1, -1):
            if row[i]:
                width = max(width, i + 1)
                break
    return [row[:width] for row in grid]


def _table(grid: list[list[str]]) -> str:
    if not grid:
        return "<p><em>Feuille vide</em></p>"
    n_cols = max(len(row) for row in grid)
    out = [
        (
            '<div class="csv-table-wrapper"><table class="csv-table xlsx-table">'
            '<thead><tr><th class="xlsx-corner"></th>'
        )
    ]
    out += [f"<th>{get_column_letter(c)}</th>" for c in range(1, n_cols + 1)]
    out.append("</tr></thead><tbody>")
    for r, row in enumerate(grid, start=1):
        out.append(f'<tr><th class="xlsx-rownum">{r}</th>')
        for c, val in enumerate(row, start=1):
            ref = f"{get_column_letter(c)}{r}"
            out.append(f'<td data-cell="{ref}">{html.escape(val)}</td>')
        out.append("</tr>")
    out.append("</tbody></table></div>")
    return "".join(out)


def render_sheets(file_path: Path) -> list[dict[str, str]]:
    """Return ``[{"name": sheet_title, "html": table_html}, ...]``."""
    wb = load_workbook(str(file_path), read_only=True, data_only=False)
    try:
        sheets = []
        for ws in wb.worksheets:
            grid = [
                [_fmt(v) for v in row]
                for row in ws.iter_rows(
                    min_row=1, max_row=MAX_ROWS, max_col=MAX_COLS, values_only=True
                )
            ]
            sheets.append({"name": ws.title, "html": _table(_trim(grid))})
        return sheets
    finally:
        wb.close()