"""Generate a root ``.kicad_sch`` that ties multiple SCH_PAGE files into one
hierarchical project.

EPRO2 multi-page schematics live as N standalone ``SCH_PAGE`` docs all
referencing the same ``SCH`` doc through ``META.schematic``. When we exported
each page as its own ``.kicad_sch`` and ran ``kicad-cli sch erc`` against it
in isolation, every cross-sheet net showed up as ``label_dangling`` /
``pin_not_connected`` because single-sheet ERC can't see the matching
endpoint on a sibling page.

Hierarchical mode fixes that:
  - Root .kicad_sch carries one ``(sheet ...)`` block per child page,
    each with a uuid the root assigns and a ``Sheetfile`` pointing at the
    child filename in the same directory.
  - Each child .kicad_sch declares its position in the hierarchy with
    ``(sheet_instances (path "/<assigned_uuid>" (page "<n>")))`` so KiCad
    can bind it to the root.
  - With both halves wired up, ``kicad-cli sch erc <root>`` walks the whole
    project, resolving global_labels across pages.

Usage:
    Build a list of (filename, page_title, assigned_uuid) tuples — one per
    child — *before* writing the children, then pass it here to emit the
    root. The same uuid you stored in this list goes into the child writer
    via its ``sheet_path="/<uuid>"`` argument.
"""

from __future__ import annotations

import uuid as _uuid
from dataclasses import dataclass

from .sexpr import Sym, to_sexpr

KICAD_SCH_VERSION = 20231120
KICAD_GENERATOR = "facere-epro2"


@dataclass
class ChildSheet:
    """One child entry in a root sheet.

    ``filename`` is relative to the root .kicad_sch's directory.
    ``sheet_uuid`` is the uuid the root assigns to this child; the child's
    own (sheet_instances) must echo it back as ``"/<sheet_uuid>"``.
    """

    filename: str
    title: str
    sheet_uuid: str


def new_sheet_uuid() -> str:
    return str(_uuid.uuid4())


def _font(size: float = 1.27) -> list:
    return [Sym("effects"), [Sym("font"), [Sym("size"), size, size]],
            [Sym("justify"), Sym("left"), Sym("bottom")]]


def _file_font(size: float = 1.27) -> list:
    return [Sym("effects"), [Sym("font"), [Sym("size"), size, size]],
            [Sym("justify"), Sym("left"), Sym("top")]]


def write_root_sheet(
    title: str,
    children: list[ChildSheet],
    *,
    project_name: str = "facere",
    grid_origin_mm: tuple[float, float] = (38.1, 38.1),
    box_size_mm: tuple[float, float] = (50.8, 25.4),
    box_pitch_mm: tuple[float, float] = (63.5, 38.1),
    columns: int = 3,
) -> str:
    """Render a root ``.kicad_sch`` listing ``children`` as ``(sheet ...)`` blocks.

    The boxes are laid out on a simple ``columns``-wide grid so they don't
    overlap on the canvas; visual layout is irrelevant to ERC but KiCad's
    GUI needs non-zero positions/sizes for the sheet to be visible/editable.
    """
    elements: list = []
    bw, bh = box_size_mm
    px, py = box_pitch_mm
    ox, oy = grid_origin_mm

    for idx, child in enumerate(children):
        col = idx % columns
        row = idx // columns
        x = ox + col * px
        y = oy + row * py
        page_num = idx + 2  # root is page 1, children start at 2

        elements.append([
            Sym("sheet"),
            [Sym("at"), x, y],
            [Sym("size"), bw, bh],
            [Sym("stroke"), [Sym("width"), 0.1524], [Sym("type"), Sym("solid")]],
            [Sym("fill"), [Sym("color"), 0, 0, 0, 0.0]],
            [Sym("uuid"), child.sheet_uuid],
            [Sym("property"), "Sheetname", child.title,
                [Sym("at"), x, y - 0.5, 0], _font()],
            [Sym("property"), "Sheetfile", child.filename,
                [Sym("at"), x, y + bh + 0.5, 0], _file_font()],
            [Sym("instances"),
                [Sym("project"), project_name,
                    [Sym("path"), "/", [Sym("page"), str(page_num)]]]],
        ])

    sch: list = [
        Sym("kicad_sch"),
        [Sym("version"), KICAD_SCH_VERSION],
        [Sym("generator"), KICAD_GENERATOR],
        [Sym("uuid"), new_sheet_uuid()],
        [Sym("paper"), "A4"],
        [Sym("title_block"),
            [Sym("title"), title],
            [Sym("comment"), 1, f"hierarchical root for {len(children)} child sheet(s)"]],
        [Sym("lib_symbols")],
        *elements,
        [Sym("sheet_instances"),
            [Sym("path"), "/", [Sym("page"), "1"]]],
    ]
    return to_sexpr(sch, pretty=True)