from copy import deepcopy

from docx.oxml import CT_Tbl
from docx.oxml.ns import qn
from docx.shared import Length, Parented
from docx.table import Table, _Row, _Cell

from md2gost.util import create_element


def _twips(value) -> int:
    """Length or EMU-int → twips.

    python-docx ``Length + Length`` returns a bare ``int`` in EMUs, not twips.
    """
    if hasattr(value, "twips"):
        return int(value.twips)
    # bare int from Length arithmetic is EMU (1 twip = 635 EMU)
    return int(value) // 635


__all__ = [
    "create_table",
    "create_table_row",
    "create_table_cell",
    "apply_cell_merge",
]


def _set_table_width(table: Table, width: Length) -> None:
    """Force fixed table width (CT_Tbl.new_tbl leaves tblW auto/0 → Word shrinks table)."""
    tbl = table._tbl
    tblPr = tbl.tblPr
    if tblPr is None:
        tblPr = create_element("w:tblPr")
        tbl.insert(0, tblPr)
    for el in tblPr.findall(qn("w:tblW")):
        tblPr.remove(el)
    tblPr.append(create_element("w:tblW", {
        "w:type": "dxa",
        "w:w": str(_twips(width)),
    }))
    for el in tblPr.findall(qn("w:tblLayout")):
        tblPr.remove(el)
    tblPr.append(create_element("w:tblLayout", {"w:type": "fixed"}))
    for el in tblPr.findall(qn("w:tblInd")):
        tblPr.remove(el)
    tblPr.append(create_element("w:tblInd", {
        "w:type": "dxa",
        "w:w": "0",
    }))


def _sync_grid_cols(table: Table, cols: int, width: Length) -> None:
    tbl = table._tbl
    grid = tbl.tblGrid
    if grid is None:
        grid = create_element("w:tblGrid")
        tbl.insert(list(tbl).index(tbl.tblPr) + 1 if tbl.tblPr is not None else 0, grid)
    for el in list(grid.findall(qn("w:gridCol"))):
        grid.remove(el)
    col_w = max(_twips(width) // max(cols, 1), 1)
    for _ in range(cols):
        grid.append(create_element("w:gridCol", {"w:w": str(col_w)}))


def create_table(parent: Parented, rows: int, cols, width: Length, style="Table Grid"):
    table = Table(CT_Tbl.new_tbl(rows, cols, width), parent)
    table.style = style
    _set_table_width(table, width)
    _sync_grid_cols(table, cols, width)

    # google docs fix
    borders = parent.part.styles[style]._element.xpath("w:tblPr/w:tblBorders")
    if borders:
        tblPr = table._tbl.tblPr
        for el in tblPr.findall(qn("w:tblBorders")):
            tblPr.remove(el)
        tblPr.append(deepcopy(borders[0]))
    for i in range(rows):
        for j in range(cols):
            cell = table.cell(i, j)
            cell._element.remove(cell.paragraphs[0]._element)
            table.cell(i, j)._element.tcPr.append(create_element("w:shd", {
                "w:fill": "auto", "w:val": "clear"
            }))

    return table


def create_table_row(parent: Table, *, header: bool = False):
    children = [create_element("w:cantSplit")]
    if header:
        children.append(create_element("w:tblHeader"))
    row = _Row(create_element("w:tr"), parent)
    row._tr.insert(0, create_element("w:trPr", children))
    return row


def create_table_cell(parent: _Row, width: Length):
    cell = _Cell(create_element("w:tc"), parent)
    cell.width = width
    return cell


def apply_cell_merge(cell: _Cell, v_merge: str | None = None, grid_span: int | None = None) -> None:
    """Apply Word OXML vertical merge and/or horizontal gridSpan on a cell.

    v_merge: ``restart`` | ``continue`` | None
    grid_span: column span (>= 2) or None
    """
    tc = cell._tc
    tcPr = tc.get_or_add_tcPr()
    if v_merge == "restart":
        tcPr.append(create_element("w:vMerge", {"w:val": "restart"}))
    elif v_merge == "continue":
        tcPr.append(create_element("w:vMerge"))
    if grid_span and grid_span > 1:
        tcPr.append(create_element("w:gridSpan", {"w:val": str(grid_span)}))