ObsiGate/backend/xlsx_reader.py

"""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``.

:func:`inspect_workbook` lists the workbook features that an openpyxl
round-trip would drop (#153 A1) so the UI can warn before saving.

#153 A16 — :func:`render_sheets` also accepts ``.xlsm`` (macros preserved on
save via ``keep_vba``), ``.xls`` (xlrd) and ``.ods`` (odfpy), both served
read-only; :func:`render_csv_table` turns a CSV into the same table shape.
"""

from __future__ import annotations

import html
import logging
import re
import zipfile
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

logger = logging.getLogger("obsigate.xlsx_reader")

# 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

# #153 A9 — window size served by ``read_sheet_window()`` (lazy per-sheet
# loading). The endpoint is bounded so a single request can never ask for the
# whole workbook back in one JSON payload; the UI pages through the rest.
MAX_WINDOW_ROWS = 1_000
DEFAULT_WINDOW_ROWS = 200

# #153 A1 — workbook parts openpyxl does not re-serialize on load+save.
# Verified against openpyxl 3.1.5: charts, images, drawings and pivot tables
# DO survive the round-trip, so they are deliberately absent from this map.
LOSSY_PARTS: dict[str, tuple[str, ...]] = {
    "slicers": ("xl/slicers/", "xl/slicerCaches/", "xl/timelines/"),
    "form_controls": ("xl/ctrlProps/", "xl/activeX/"),
    "connections": ("xl/queryTables/", "xl/connections.xml"),
    "custom_xml": ("customXml/",),
    "signature": ("_xmlsignatures/",),
    "rich_comments": ("xl/threadedComments/", "xl/persons/"),
    "macros": ("xl/vbaProject.bin",),
}

# A formula cell carrying its last computed result: ``<f>…</f><v>…</v>``.
# openpyxl writes an EMPTY ``<v></v>`` itself, hence the ``[^<]`` guard: only a
# non-empty value counts. openpyxl keeps the formula but drops the cached result,
# so any reader using ``data_only=True`` (pandas, converters) sees ``None`` until
# Excel recalculates.
_CACHED_FORMULA_RE = re.compile(rb"<f[ >][^<]*</f>\s*<v>[^<]")

# Sheet XML scanned by the cached-formula probe (CPU guard, like MAX_REPLACE_FILE_BYTES).
_MAX_PROBE_BYTES = 8_000_000

# #153 A5 — ceiling on the text handed to the TF-IDF / semantic index. A workbook
# is a data dump, not prose: indexing every cell would flood the inverted index
# and bury the notes. Sheet names + the first rows are enough to make a
# spreadsheet findable by its headers.
MAX_INDEX_CHARS = 5_000
_INDEX_ROWS_PER_SHEET = 20
MAX_INDEX_SHEETS = 20

# #153 A15 — reading styles is a second (non-read_only) pass on the sheet XML.
# Bounded like everything else: a cell must be INSIDE the rendered window to
# deserve an inline style, so a huge workbook never triggers a huge payload.
# Only data-driven fragments are emitted: the hex values come from the file,
# never from a hardcoded color table.


def _cell_fragments(cell: Any) -> tuple[list[str], str | None]:
    """Inline CSS fragments of one cell plus its horizontal alignment.

    Fixed, color-first order: the API contract documents ``color:...`` as the
    first fragment of a styled cell. Only data-driven values are emitted —
    every hex comes from the workbook itself, never a hardcoded table.
    """
    fragments: list[str] = []
    font = cell.font
    if font and font.color is not None and isinstance(font.color.rgb, str):
        # ARGB from the workbook itself — never a hardcoded table.
        rgb = font.color.rgb
        if len(rgb) == 8 and rgb != "FF000000":
            fragments.append(f"color:#{rgb[2:].lower()}")
    fill = cell.fill
    if fill and fill.fgColor is not None and isinstance(fill.fgColor.rgb, str):
        rgb = fill.fgColor.rgb
        if len(rgb) == 8 and rgb not in ("00000000", "FFFFFFFF"):
            fragments.append(f"background:#{rgb[2:].lower()}")
    if font and font.bold:
        fragments.append("font-weight:600")
    if font and font.italic:
        fragments.append("font-style:italic")
    fmt = cell.number_format
    if fmt and fmt not in ("General", "@"):
        # A custom number format is signalled typographically (mono font)
        # rather than rendered: the displayed value already carries the
        # formatting from _fmt(). Single quotes: the fragment lands inside a
        # double-quoted HTML attribute.
        fragments.append("font-family:'JetBrains Mono',monospace")
    alignment = cell.alignment
    align = alignment.horizontal if alignment else None
    return fragments, (align if align in ("left", "right", "center") else None)


def _sheet_style_maps(ws: Any) -> tuple[dict[str, str], dict[str, str]]:
    """Flat ``{ref: css}`` and ``{ref: align}`` maps of one worksheet.

    The flat string is what the API serves and what the viewer applies
    verbatim to ``td.style``; a plain cell is simply absent from the map.
    ``left`` is the table default and never included. Bounded by
    ``MAX_ROWS x MAX_COLS`` like the render itself.
    """
    styles: dict[str, str] = {}
    aligns: dict[str, str] = {}
    for row in ws.iter_rows(min_row=1, max_row=MAX_ROWS, max_col=MAX_COLS):
        for cell in row:
            if cell.value is None and cell.number_format == "General":
                continue
            fragments, align = _cell_fragments(cell)
            if fragments:
                styles[cell.coordinate] = ";".join(fragments)
            if align and align != "left":
                aligns[cell.coordinate] = align
    return styles, aligns


def read_sheet_styles(file_path: Path, sheet: str) -> dict[str, dict[str, Any]]:
    """Return ``{ref: {style, align}}`` for the styled cells of one sheet.

    ``style`` is the flat CSS fragment the viewer applies verbatim and
    ``align`` the horizontal text-align when it is not the table default.
    Normal (non-streaming) load — styles are unavailable in read_only mode;
    a failure yields ``{}`` so the viewer falls back to the plain rendering.
    """
    meta = read_workbook_meta(file_path).get(sheet, {})
    styles_map = meta.get("styles", {})
    aligns = meta.get("aligns", {})
    out: dict[str, dict[str, Any]] = {}
    for ref, css in styles_map.items():
        entry: dict[str, Any] = {"style": css}
        if ref in aligns:
            entry["align"] = aligns[ref]
        out[ref] = entry
    return out


def read_sheet_merges(file_path: Path, sheet: str) -> list[str]:
    """Return the merged ranges of one sheet as ``A1:C3`` strings."""
    try:
        # Styles and merges are only fully materialised in normal mode
        # (read_only=True leaves merged_cells empty).
        wb = load_workbook(str(file_path))
    except Exception:
        return []
    try:
        if sheet not in wb.sheetnames:
            return []
        merged = getattr(wb[sheet], "merged_cells", None)
        ranges = getattr(merged, "ranges", None) or []
        return [str(r) for r in ranges]
    except Exception:
        logger.debug("xlsx merges unavailable", exc_info=True)
        return []
    finally:
        wb.close()


def read_sheet_freeze(file_path: Path, sheet: str) -> str:
    """Return the freeze-panes anchor of one sheet ('' when not frozen).

    Normal (non-streaming) load: `freeze_panes` is NOT materialised on
    ReadOnlyWorksheet in openpyxl 3.1.x — read_only=True always yields ''.
    """
    try:
        wb = load_workbook(str(file_path))
    except Exception:
        return ""
    try:
        if sheet not in wb.sheetnames:
            return ""
        return str(getattr(wb[sheet], "freeze_panes", None) or "")
    except Exception:
        return ""
    finally:
        wb.close()


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 _cell_cached(cached: list[list[str]] | None, r: int, c: int) -> str:
    """Return the cached result for a 0-based cell, or ``""``.

    The shadow grid is read positionally and may be narrower than the formula
    grid (``_trim`` collapses the trailing empty columns of each grid
    independently), so every lookup is bounds-checked rather than assumed.
    """
    if not cached or r >= len(cached):
        return ""
    row = cached[r]
    return row[c] if c < len(row) else ""


def _table(
    grid: list[list[str]],
    cached: list[list[str]] | None = None,
    row_offset: int = 0,
    styles: dict[str, dict[str, Any]] | None = None,
) -> str:
    """Render a grid as an HTML table.

    ``cached`` is the same grid read with ``data_only=True`` (#153 A12): where a
    formula cell still carries its last computed result, it is shown as a
    discreet second line (``<span class="xlsx-cached">``) so the user sees the
    number Excel last calculated instead of only the formula text. The span
    carries ``data-cached-value`` and is titled client-side from
    ``xlsx.cached_value_title`` — the backend never emits UI text.

    ``row_offset`` is the number of rows skipped before this grid (#153 A9): the
    row numbers and the ``data-cell`` references must stay the real A1
    coordinates of the sheet, not of the window.

    ``styles`` maps A1 references to ``{style, align}`` fragments (#153 A15:
    bold, italic, background, alignment) — the backend only reads the
    workbook, the fragments are built from it and always data-driven, never
    hardcoded colors. A plain ``str`` value is tolerated (legacy callers).
    """
    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=row_offset + 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}"
            meta = (styles or {}).get(ref)
            if meta is None:
                style_attr = ""
            else:
                # Legacy callers may still pass a bare CSS string.
                if isinstance(meta, str):
                    meta = {"style": meta}
                fragment = meta.get("style", "")
                align = meta.get("align")
                if align and align not in ("left",):
                    # left is the table default; only non-default alignments
                    # need an explicit declaration.
                    fragment = f"{fragment};text-align:{align}" if fragment else f"text-align:{align}"
                style_attr = f' style="{fragment}"' if fragment else ""
            # The cached result only makes sense for a formula cell: on a plain
            # value cell the two reads are identical and showing both would
            # duplicate the text.
            shadow = ""
            if cached is not None and val.startswith("="):
                # `c` is 1-based (A1 notation) and `r` too, while the grid is
                # 0-based: translate both.
                cval = _cell_cached(cached, r - 1, c - 1)
                if cval and cval != val:
                    # The tooltip is translated client-side from
                    # `xlsx.cached_value_title`; never hardcode UI text here.
                    shadow = (
                        f'<span class="xlsx-cached" data-cached-value="1">'
                        f"{html.escape(cval)}</span>"
                    )
            out.append(
                f'<td data-cell="{ref}"{style_attr}>{html.escape(val)}{shadow}</td>'
            )
        out.append("</tr>")
    out.append("</tbody></table></div>")
    return "".join(out)


def _has_cached_formulas(zf: zipfile.ZipFile) -> bool:
    """True when at least one formula cell still carries its computed value."""
    budget = _MAX_PROBE_BYTES
    for name in zf.namelist():
        if not name.startswith("xl/worksheets/sheet") or not name.endswith(".xml"):
            continue
        try:
            with zf.open(name) as fh:
                while budget > 0:
                    chunk = fh.read(65536)
                    if not chunk:
                        break
                    budget -= len(chunk)
                    if _CACHED_FORMULA_RE.search(chunk):
                        return True
        except (KeyError, OSError, zipfile.BadZipFile):
            continue
    return False


def inspect_workbook(file_path: Path) -> list[str]:
    """Return the sorted keys of :data:`LOSSY_PARTS` present in *file_path*.

    Read-only inspection of the OPC package (central directory + a bounded scan
    of the sheet XML). Never raises: an unreadable or encrypted workbook simply
    yields ``[]`` and the save path keeps its current behaviour.

    ``cached_values`` is a synthetic key: openpyxl keeps the formula but drops
    the cached result, so the workbook stays correct once Excel recalculates it.
    """
    try:
        with zipfile.ZipFile(file_path) as zf:
            names = set(zf.namelist())
            found = {
                key
                for key, prefixes in LOSSY_PARTS.items()
                if any(name.startswith(prefix) for name in names for prefix in prefixes)
            }
            if _has_cached_formulas(zf):
                found.add("cached_values")
            return sorted(found)
    except (OSError, zipfile.BadZipFile):
        return []


def read_workbook_meta(file_path: Path) -> dict[str, dict[str, Any]]:
    """Return ``{sheet: {styles, aligns, merges, freeze}}`` for every sheet.

    One normal (non-streaming) load serves the three A15 metadata maps: the
    fragments are the workbook's own values, a failure yields ``{}`` per sheet
    so the viewer keeps its plain rendering. Styles are read with
    ``data_only=False`` — the edited value is the formula, not its result.
    """
    try:
        wb = load_workbook(str(file_path), data_only=False)
    except Exception:
        return {}
    out: dict[str, dict[str, Any]] = {}
    try:
        for ws in wb.worksheets:
            styles, aligns = _sheet_style_maps(ws)
            merged = getattr(ws, "merged_cells", None)
            ranges = getattr(merged, "ranges", None) or []
            out[ws.title] = {
                "styles": styles,
                "aligns": aligns,
                "merges": [str(r) for r in ranges],
                "freeze": str(getattr(ws, "freeze_panes", None) or ""),
            }
        return out
    except Exception:
        logger.debug("xlsx meta unavailable", exc_info=True)
        for t in wb.sheetnames:
            out.setdefault(t, {"styles": {}, "aligns": {}, "merges": [], "freeze": ""})
        return out
    finally:
        wb.close()


def render_sheets(file_path: Path) -> list[dict[str, Any]]:
    """Return one dict per sheet: ``{name, html, rows, cols, total_*, truncated}``.

    Reads the workbook twice: once with ``data_only=False`` for the formulas
    (what the user must edit) and, when any formula carries a cached result
    (#153 A12), once with ``data_only=True`` to show what Excel last computed.
    The second pass is skipped entirely when the archive holds no cached value,
    so the common case still costs a single load.

    ``total_rows``/``total_cols`` are the dimensions the sheet declares and
    ``truncated`` says whether the hard caps actually cut it (#153 A8) — the
    viewer needs both to stop silently hiding the tail of a sheet.
    """
    wb = load_workbook(str(file_path), read_only=True, data_only=False)
    try:
        formulas = [_sheet_grid(ws) for ws in wb.worksheets]
        titles = [ws.title for ws in wb.worksheets]
        extents = [_sheet_extent(ws) for ws in wb.worksheets]
    finally:
        wb.close()

    cached: list[list[list[str]]] | None = None
    if _has_cached_values(file_path):
        cached = _read_cached_grids(file_path, titles)

    # #153 A15 — one extra normal-mode load serves the styles/merges/freeze
    # metadata of every sheet; the HTML then carries the fragments itself.
    meta = read_workbook_meta(file_path)

    sheets = []
    for i, title in enumerate(titles):
        grid = _trim(formulas[i])
        # The shadow grid is NOT trimmed independently: _trim drops the
        # trailing empty columns of each grid on its own width, which would
        # shift every cached value left of its formula. Indexing it
        # positionally against the untrimmed grid keeps the two aligned.
        shadow = cached[i] if cached is not None and i < len(cached) else None
        total_rows, total_cols = extents[i]
        sheet_meta = meta.get(title, {})
        sheets.append(
            {
                "name": title,
                "html": _table(grid, shadow, styles=sheet_meta.get("styles")),
                "rows": len(grid),
                "cols": max((len(r) for r in grid), default=0),
                "total_rows": total_rows,
                "total_cols": total_cols,
                # Coverage, not display size: `rows`/`cols` are post-trim (a
                # sheet of 3 filled cells in a 500-row block renders 1x1), and
                # the client must announce the cap it stopped at, not how many
                # cells happen to be non-empty.
                "max_rows": MAX_ROWS,
                "max_cols": MAX_COLS,
                # A sheet is truncated when the caps, not the trailing blanks,
                # decided its shape: comparing against the *rendered* size would
                # flag every sheet carrying a few empty formatted rows.
                "truncated": total_rows > MAX_ROWS or total_cols > MAX_COLS,
                "styles": sheet_meta.get("styles", {}),
                "aligns": sheet_meta.get("aligns", {}),
                "merges": sheet_meta.get("merges", []),
                "freeze": sheet_meta.get("freeze", ""),
            }
        )
    return sheets


def read_sheet_window(
    file_path: Path,
    sheet: str,
    offset: int = 0,
    limit: int = DEFAULT_WINDOW_ROWS,
) -> dict[str, Any] | None:
    """Return a window of rows of one sheet, or ``None`` if the sheet is unknown.

    Backs the lazy per-sheet loading of #153 A9: the viewer asks for the rows
    it is about to display instead of shipping every sheet in the initial file
    payload. ``offset`` is 0-based; the row numbers and the ``data-cell``
    references in the returned ``html`` are the real A1 coordinates of the
    sheet, so a window is indistinguishable from a full render.

    ``limit`` is clamped to :data:`MAX_WINDOW_ROWS`. Raises nothing: an unknown
    sheet yields ``None`` and a broken workbook propagates the caller's usual
    500.
    """
    offset = max(int(offset), 0)
    limit = min(max(int(limit), 1), MAX_WINDOW_ROWS)

    wb = load_workbook(str(file_path), read_only=True, data_only=False)
    try:
        if sheet not in wb.sheetnames:
            return None
        ws = wb[sheet]
        total_rows, total_cols = _sheet_extent(ws)
        grid = _trim(
            _sheet_grid(ws, min_row=offset + 1, max_row=offset + limit)
        )
    finally:
        wb.close()

    shadow: list[list[str]] | None = None
    # Same A12 rule as the full render: the second read only happens when the
    # archive really holds cached results.
    if _has_cached_values(file_path):
        shadow = _read_cached_window(file_path, sheet, offset, limit)
    # #153 A15 — same metadata as the full render, so a lazy window is
    # indistinguishable from it (styles in the HTML, merges/freeze for the
    # client-side spanning).
    meta = read_workbook_meta(file_path).get(sheet, {})
    return {
        "sheet": sheet,
        "offset": offset,
        "limit": limit,
        "rows": len(grid),
        "cols": max((len(r) for r in grid), default=0),
        "total_rows": total_rows,
        "total_cols": total_cols,
        "max_rows": MAX_ROWS,
        "max_cols": MAX_COLS,
        "truncated": total_rows > MAX_ROWS or total_cols > MAX_COLS,
        "has_more": offset + len(grid) < total_rows,
        "html": _table(grid, shadow, row_offset=offset, styles=meta.get("styles")),
        "styles": meta.get("styles", {}),
        "aligns": meta.get("aligns", {}),
        "merges": meta.get("merges", []),
        "freeze": meta.get("freeze", ""),
    }


def _read_cached_window(
    file_path: Path, sheet: str, offset: int, limit: int
) -> list[list[str]] | None:
    """``data_only=True`` grid for one window, or ``None`` if unavailable.

    Best effort like :func:`_read_cached_grids`: a workbook Excel opens but
    openpyxl cannot re-read must still display (formulas only).
    """
    try:
        wb = load_workbook(str(file_path), read_only=True, data_only=True)
    except Exception:
        return None
    try:
        if sheet not in wb.sheetnames:
            return None
        return _sheet_grid(
            wb[sheet], min_row=offset + 1, max_row=offset + limit
        )
    except Exception:
        logger.debug("xlsx cached window unavailable", exc_info=True)
        return None
    finally:
        wb.close()


def _sheet_extent(ws: Any) -> tuple[int, int]:
    """Rows and columns the worksheet declares, never negative.

    ``max_row``/``max_column`` come from the sheet's dimension record; a
    hand-edited file may omit it, hence the defensive coercion.
    """
    try:
        rows = max(int(getattr(ws, "max_row", 0) or 0), 0)
    except (TypeError, ValueError):
        rows = 0
    try:
        cols = max(int(getattr(ws, "max_column", 0) or 0), 0)
    except (TypeError, ValueError):
        cols = 0
    return rows, cols


def _sheet_grid(
    ws: Any, min_row: int = 1, max_row: int = MAX_ROWS, max_col: int = MAX_COLS
) -> list[list[str]]:
    """Read a worksheet window into a grid of formatted strings, bounded by the caps."""
    return [
        [_fmt(v) for v in row]
        for row in ws.iter_rows(
            min_row=min_row, max_row=max_row, max_col=max_col, values_only=True
        )
    ]


def _has_cached_values(file_path: Path) -> bool:
    """True when the archive holds at least one ``<f>…</f><v>…</v>``."""
    try:
        with zipfile.ZipFile(file_path) as zf:
            return _has_cached_formulas(zf)
    except (OSError, zipfile.BadZipFile):
        return False


def _read_cached_grids(
    file_path: Path, titles: list[str]
) -> list[list[list[str]]] | None:
    """Read every sheet with ``data_only=True`` (what Excel last computed).

    Best effort: returns ``None`` on any failure so the viewer falls back to the
    formula-only rendering. A workbook Excel opens but openpyxl cannot re-read
    must still display.
    """
    try:
        wb = load_workbook(str(file_path), read_only=True, data_only=True)
    except Exception:
        return None
    try:
        grids = [_sheet_grid(ws) for ws in wb.worksheets]
        if [ws.title for ws in wb.worksheets] != titles:
            return None
        return grids
    except Exception:
        logger.debug("xlsx cached values unavailable", exc_info=True)
        return None
    finally:
        wb.close()


def extract_indexable_text(file_path: Path) -> str:
    """Return searchable text for the TF-IDF / semantic index (#153 A5).

    Sheet names plus the first :data:`_INDEX_ROWS_PER_SHEET` rows of each
    sheet, capped at :data:`MAX_INDEX_CHARS`. Rows are tab-joined so a search
    for a header matches the sheet it belongs to.

    Never raises: a corrupt, encrypted or unsupported workbook yields ``""`` so
    the file still gets indexed by name (same contract as :func:`inspect_workbook`).
    """
    chunks: list[str] = []
    budget = MAX_INDEX_CHARS
    try:
        wb = load_workbook(str(file_path), read_only=True, data_only=True)
    except Exception:
        # Encrypted (BadZipFile) or not a real workbook: name-only indexing.
        return ""
    try:
        for ws in wb.worksheets[:MAX_INDEX_SHEETS]:
            if budget <= 0:
                break
            # The sheet title alone is a strong signal ("Recettes", "Budget").
            block = [ws.title]
            for row in ws.iter_rows(
                min_row=1, max_row=_INDEX_ROWS_PER_SHEET, max_col=MAX_COLS, values_only=True
            ):
                cells = [_fmt(v) for v in row]
                # Skip blank rows instead of emitting runs of tabs.
                if not any(c.strip() for c in cells):
                    continue
                block.append("\t".join(cells).rstrip())
            text = "\n".join(block)
            chunks.append(text[:budget])
            budget -= len(text)
    except Exception:
        # Truncated but still useful: keep whatever was collected.
        pass
    finally:
        wb.close()
    return "\n".join(c for c in chunks if c).strip()


# ── #153 A16 — additional spreadsheet formats ───────────────────────────────


def render_csv_table(raw: str, *, delimiter: str = ",") -> str:
    """Render CSV text as the same HTML table shape the xlsx viewer consumes.

    Row numbers replace the A1 column: a CSV has no fixed column count, so
    the first row is a plain data row like the others (the viewer offers the
    toolbar either way). Every cell is HTML-escaped at render time.
    """
    import csv as csv_mod
    import io as io_mod

    reader = csv_mod.reader(io_mod.StringIO(raw), delimiter=delimiter)
    try:
        rows = [row for row in reader]
    except csv_mod.Error:
        # A malformed CSV still renders: each line becomes a one-cell row.
        rows = [[line] for line in raw.splitlines()]
    if not rows:
        return "<p><em>Feuille vide</em></p>"
    n_cols = max(len(r) for r in rows)
    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(rows, start=1):
        out.append(f'<tr><th class="xlsx-rownum">{r}</th>')
        for c in range(1, n_cols + 1):
            val = row[c - 1] if c - 1 < len(row) else ""
            out.append(f'<td data-cell="{get_column_letter(c)}{r}">{html.escape(val)}</td>')
        out.append("</tr>")
    out.append("</tbody></table></div>")
    return "".join(out)


def render_legacy_workbook(file_path: Path, ext: str) -> list[dict[str, Any]]:
    """Render ``.xls``/``.ods`` sheets with the same dict shape as xlsx.

    Read-only formats (#153 A16): ``styles``/``aligns``/``merges``/``freeze``
    are served empty so the client-side wiring keeps one code path. Raises
    nothing to the render path: an unreadable file yields one error sheet.
    """
    name = file_path.name
    try:
        if ext == ".xls":
            import xlrd

            book = xlrd.open_workbook(str(file_path))
            titles = book.sheet_names()
            grids = []
            for si in range(book.nsheets):
                sh = book.sheet_by_index(si)
                grid = [
                    [_fmt(sh.cell_value(r, c)) for c in range(min(sh.ncols, MAX_COLS))]
                    for r in range(min(sh.nrows, MAX_ROWS))
                ]
                grids.append(_trim(grid))
            total = [(sh.nrows, sh.ncols) for sh in (book.sheet_by_index(i) for i in range(book.nsheets))]
        elif ext == ".ods":
            from odf.opendocument import load as odf_load
            from odf.table import Table, TableCell, TableRow
            from odf.teletype import extractText

            doc = odf_load(str(file_path))
            titles = []
            grids = []
            total = []
            for table in doc.getElementsByType(Table):
                title = table.getAttribute("name") or f"Feuille {len(titles) + 1}"
                titles.append(title)
                grid = []
                for row in table.getElementsByType(TableRow)[:MAX_ROWS]:
                    row_cells = row.getElementsByType(TableCell)
                    values: list[str] = []
                    for tc in row_cells[:MAX_COLS]:
                        repeat = int(tc.getAttribute("numbercolumnsrepeated") or 1)
                        values.extend([extractText(tc)] * min(repeat, MAX_COLS - len(values)))
                    grid.append(values)
                grids.append(_trim(grid))
                total.append((len(grid), max((len(r) for r in grid), default=0)))
        else:
            raise ValueError(f"Unsupported legacy format: {ext}")
    except Exception as exc:
        logger.warning("legacy workbook render failed for %s: %s", name, exc)
        return [
            {
                "name": name,
                "html": (
                    '<p><em>Feuille vide</em></p>'
                ),
                "rows": 0,
                "cols": 0,
                "total_rows": 0,
                "total_cols": 0,
                "max_rows": MAX_ROWS,
                "max_cols": MAX_COLS,
                "truncated": False,
                "styles": {},
                "aligns": {},
                "merges": [],
                "freeze": "",
            }
        ]

    sheets: list[dict[str, Any]] = []
    for i, title in enumerate(titles):
        grid = grids[i] if i < len(grids) else []
        t_rows, t_cols = total[i] if i < len(total) else (0, 0)
        sheets.append(
            {
                "name": title,
                "html": _table(grid),
                "rows": len(grid),
                "cols": max((len(r) for r in grid), default=0),
                "total_rows": t_rows,
                "total_cols": t_cols,
                "max_rows": MAX_ROWS,
                "max_cols": MAX_COLS,
                "truncated": t_rows > MAX_ROWS or t_cols > MAX_COLS,
                "styles": {},
                "aligns": {},
                "merges": [],
                "freeze": "",
            }
        )
    return sheets