FabledScribe/src/scribe/mcp/tools/design_systems.py

"""Design system + token MCP tools — wrappers over services/design_systems.py.

A design system is a stylesheet held as records: a named set of tokens with an
optional parent, so a family system carries the house style and an app system
carries only what it changes. Precedence by name along the parent chain IS the
CSS cascade, which is why "what does this app alter?" is a plain list rather
than a diff.

Parity with the REST surface is a rule, not a nicety (see
`tests/test_routes_design_systems.py`): an agent and a browser are two callers
of one service.

Sentinels, matching the milestone/task tool conventions:
  - title="" / description="" / etc. -> "leave unchanged" on update
  - parent_id / design_system_id: 0 = leave unchanged, -1 = clear, positive = set
    (three states, because clearing a parent is a real operation and not the
    same as omitting the argument)
  - order_index=-1 -> "leave unchanged" (0 is a valid order_index)
"""
from __future__ import annotations

from scribe.mcp._context import current_user_id
from scribe.services import design_systems as ds_svc
from scribe.services.design_systems import DesignSystemCycle


async def create_design_system(
    title: str,
    description: str = "",
    guidance: str = "",
    parent_id: int = 0,
) -> dict:
    """Create a design system, optionally inheriting from another.

    Args:
        title: What this system is, e.g. "FabledSword" or "Scribe" (required).
        description: What it covers and when it applies.
        guidance: The narrative a token table cannot hold — aesthetic, voice and
            tone, what is deliberately out of scope. Markdown, free-form.
        parent_id: Inherit from this system — it holds the defaults this one
            overrides. Omit (0) for a top-level "family" system, which is what
            a first design system usually is.
    """
    uid = current_user_id()
    system = await ds_svc.create_design_system(
        uid,
        title=title,
        description=description or None,
        guidance=guidance or None,
        parent_id=parent_id or None,
    )
    if system is None:
        raise ValueError(f"parent design system {parent_id} not found or not writable")
    return system.to_dict()


async def list_design_systems() -> dict:
    """List your design systems. An empty list is normal — most installs have none."""
    uid = current_user_id()
    rows = await ds_svc.list_design_systems(uid)
    return {"design_systems": [s.to_dict() for s in rows]}


async def get_design_system(design_system_id: int) -> dict:
    """Fetch a design system plus its OWN tokens — i.e. what it changes.

    For what it actually resolves to once inheritance is applied, use
    `resolve_design_system`. The two answer different questions and a system
    that overrides nothing has an empty token list but a full resolved set.
    """
    uid = current_user_id()
    system = await ds_svc.get_design_system(uid, design_system_id)
    if system is None:
        raise ValueError(f"design system {design_system_id} not found")
    tokens = await ds_svc.list_tokens(uid, design_system_id)
    return {
        "design_system": system.to_dict(),
        "tokens": [t.to_dict() for t in tokens],
    }


async def resolve_design_system(design_system_id: int) -> dict:
    """The EFFECTIVE token set — everything inherited, with this system's on top.

    Each token carries `origin_by_mode` (which system supplied each mode's
    value) and `contributions` (every system that offered one, deepest first —
    so entry 0 won and the rest were shadowed). Reach for this when you need to
    know what a value actually IS; reach for `get_design_system` when you need
    to know what this system CHANGES.
    """
    uid = current_user_id()
    resolved = await ds_svc.resolve_design_system(uid, design_system_id)
    if resolved is None:
        raise ValueError(f"design system {design_system_id} not found")
    return {
        "design_system_id": design_system_id,
        "tokens": [t.to_dict() for t in resolved],
    }


async def update_design_system(
    design_system_id: int,
    title: str = "",
    description: str = "",
    guidance: str = "",
    parent_id: int = 0,
) -> dict:
    """Update a design system.

    Args:
        design_system_id: The system to update.
        title: New title, or "" to leave unchanged.
        description: New description, or "" to leave unchanged.
        guidance: New guidance prose, or "" to leave unchanged.
        parent_id: 0 = leave unchanged, -1 = clear (make this a top-level
            family system), positive = inherit from that system. A parent that
            already inherits from this system is refused — that would be a loop.
    """
    uid = current_user_id()
    fields: dict = {}
    if title:
        fields["title"] = title
    if description:
        fields["description"] = description
    if guidance:
        fields["guidance"] = guidance
    if parent_id:
        fields["parent_id"] = None if parent_id == -1 else parent_id
    try:
        system = await ds_svc.update_design_system(uid, design_system_id, **fields)
    except DesignSystemCycle as exc:
        raise ValueError(str(exc)) from exc
    if system is None:
        raise ValueError(f"design system {design_system_id} not found or not writable")
    return system.to_dict()


async def delete_design_system(design_system_id: int) -> dict:
    """Soft-delete a design system (recoverable).

    Systems that inherited from it become top-level systems keeping their own
    tokens — deleting a family does not delete the apps under it.
    """
    uid = current_user_id()
    if not await ds_svc.delete_design_system(uid, design_system_id):
        raise ValueError(f"design system {design_system_id} not found or not writable")
    return {"message": f"Design system {design_system_id} deleted."}


async def get_design_system_stylesheet(
    design_system_id: int,
    root_selector: str = ":root",
) -> dict:
    """The master CSS sheet a design system generates.

    Purpose tokens only — this sheet declares what values MEAN and styles no
    elements. Components (buttons, tables, input schemes) are SNIPPETS that
    reference these names, so a value is stated once and reused rather than
    restated per element. Reach for this when you need the tokens a snippet is
    allowed to use.

    Also returns `valueless` (tokens the system names but has no value for) and
    `duplicates` (values declared under more than one name — a deliberate alias,
    or one idea recorded twice).

    Args:
        design_system_id: The system to render.
        root_selector: Selector for the base layer. Defaults to `:root`; pass a
            container selector to scope the sheet to a preview region.
    """
    uid = current_user_id()
    result = await ds_svc.stylesheet_for_system(uid, design_system_id, root_selector)
    if result is None:
        raise ValueError(f"design system {design_system_id} not found")
    return result


async def check_snippets_against_design_system(
    design_system_id: int,
    project_id: int = 0,
) -> dict:
    """Which recorded snippets disagree with a design system's sheet.

    Snippets are the component layer — buttons, tables, input schemes — and they
    are supposed to use the tags the sheet declares. Three findings per snippet,
    each currently silent in the codebase:

      unknown             `var(--x)` where the system has no `--x`. Renders as
                          NOTHING: no error, no failing test, just an element
                          that quietly isn't styled.
      superseded_literals a literal the sheet says to stop writing, paired with
                          the token to write instead.
      local_definitions   custom properties the snippet mints for itself rather
                          than using shared ones — the bloat a shared sheet
                          exists to prevent.

    Snippets with nothing to report are omitted. Reach for this before writing
    or reviewing component CSS.

    Args:
        design_system_id: The system whose sheet is authoritative.
        project_id: Narrow to one project, or 0 for every project.
    """
    uid = current_user_id()
    result = await ds_svc.check_snippets_against_system(
        uid, design_system_id, project_id
    )
    if result is None:
        raise ValueError(f"design system {design_system_id} not found")
    return result


async def import_design_system_from_rulebook(
    design_system_id: int,
    rulebook_id: int,
    apply: bool = False,
) -> dict:
    """Seed a design system from a rulebook that describes one in prose.

    Reads the rulebook's colour and token declarations and proposes the tokens
    they add up to — joining "Obsidian #14171A" in one rule to `--fs-obsidian`
    in another, since neither alone is a token.

    Defaults to a PREVIEW. An import is a proposal: rulebooks are written
    aspirationally and some of what they describe was never built, so read
    `proposed` before setting apply=True. Every entry carries the rule and
    sentence it came from so the claim can be checked rather than trusted.

    Existing token names are never overwritten — a second run fills gaps and
    lists the rest under `skipped`, so it is safe to repeat.

    Args:
        design_system_id: The system to seed.
        rulebook_id: The rulebook to read.
        apply: False (default) previews; True writes the tokens.
    """
    uid = current_user_id()
    report = await ds_svc.import_from_rulebook(
        uid, design_system_id, rulebook_id, apply=apply,
    )
    if report is None:
        raise ValueError(
            f"design system {design_system_id} not writable, or rulebook "
            f"{rulebook_id} not readable"
        )
    return report


# ── Tokens ──────────────────────────────────────────────────────────────

async def create_design_token(
    design_system_id: int,
    name: str,
    value_by_mode: dict | None = None,
    group_name: str = "",
    purpose: str = "",
    rationale: str = "",
    supersedes: list | None = None,
    order_index: int = 0,
) -> dict:
    """Add a token to a design system.

    Args:
        design_system_id: The system that owns this token.
        name: The custom-property name, e.g. "--fs-obsidian" (required).
        value_by_mode: Values keyed by mode, e.g.
            {"base": "#f7f5ef", "dark": "#14171a"}. Use "base" for the value
            that applies when no mode is more specific; a token that is not
            mode-dependent needs only "base". In a system WITH a parent, an
            omitted mode is inherited rather than blanked.
        group_name: Free-text grouping — "surface", "text", "radius", whatever
            this system's own vocabulary is.
        purpose: What the token is for, e.g. "page bg, deepest surface".
        rationale: WHY it is this value — a different question from purpose.
            "Success equals Moss, aligned by design" is a rationale; "page bg,
            deepest surface" is a purpose.
        supersedes: Literal values this token should be used INSTEAD OF, e.g.
            ["#fff", "#ffffff"]. This is how a design system records what a
            prohibition was trying to say — not "white is banned" but "write
            this token instead". Declare it rather than expecting it to be
            inferred: a superseded literal and the token's own value are
            usually different values, so nothing can connect them by matching.
        order_index: Display position within its group.
    """
    uid = current_user_id()
    token = await ds_svc.create_token(
        uid,
        design_system_id=design_system_id,
        name=name,
        value_by_mode=value_by_mode,
        group_name=group_name or None,
        purpose=purpose or None,
        rationale=rationale or None,
        supersedes=supersedes,
        order_index=order_index,
    )
    if token is None:
        raise ValueError(f"design system {design_system_id} not found or not writable")
    return token.to_dict()


async def list_design_tokens(design_system_id: int) -> dict:
    """A design system's OWN tokens — its override set, not its effective set."""
    uid = current_user_id()
    rows = await ds_svc.list_tokens(uid, design_system_id)
    return {"tokens": [t.to_dict() for t in rows]}


async def update_design_token(
    token_id: int,
    name: str = "",
    value_by_mode: dict | None = None,
    group_name: str = "",
    purpose: str = "",
    rationale: str = "",
    supersedes: list | None = None,
    order_index: int = -1,
) -> dict:
    """Update a token. Empty/None args leave a field unchanged.

    `value_by_mode` and `supersedes` REPLACE their whole value rather than
    merging into it, so send every entry you want the token to keep. Pass `[]`
    to clear `supersedes` entirely.
    """
    uid = current_user_id()
    fields: dict = {}
    if name:
        fields["name"] = name
    if value_by_mode is not None:
        fields["value_by_mode"] = value_by_mode
    if group_name:
        fields["group_name"] = group_name
    if purpose:
        fields["purpose"] = purpose
    if rationale:
        fields["rationale"] = rationale
    # `is not None`, not truthiness: `[]` is a meaningful edit (drop every
    # superseded literal) and would otherwise be unreachable.
    if supersedes is not None:
        fields["supersedes"] = supersedes
    if order_index >= 0:
        fields["order_index"] = order_index
    token = await ds_svc.update_token(uid, token_id, **fields)
    if token is None:
        raise ValueError(f"design token {token_id} not found or not writable")
    return token.to_dict()


async def delete_design_token(token_id: int) -> dict:
    """Soft-delete a token (recoverable).

    In a system with a parent this restores inheritance: the token stops being
    overridden here and resolves to the parent's value again.
    """
    uid = current_user_id()
    if not await ds_svc.delete_token(uid, token_id):
        raise ValueError(f"design token {token_id} not found or not writable")
    return {"message": f"Design token {token_id} deleted."}


async def set_project_design_system(project_id: int, design_system_id: int = 0) -> dict:
    """Point a project at a design system.

    Args:
        project_id: The project to style.
        design_system_id: The system it uses, or -1 to clear it. Pointing at a
            system only requires READ access to it — consuming a design system
            is not changing it.
    """
    uid = current_user_id()
    target = None if design_system_id == -1 else design_system_id
    ok = await ds_svc.set_project_design_system(uid, project_id, target)
    if not ok:
        raise ValueError(
            f"project {project_id} not writable, or design system "
            f"{design_system_id} not found"
        )
    return {"project_id": project_id, "design_system_id": target}


def register(mcp) -> None:
    for fn in (
        create_design_system,
        list_design_systems,
        get_design_system,
        resolve_design_system,
        update_design_system,
        delete_design_system,
        get_design_system_stylesheet,
        check_snippets_against_design_system,
        import_design_system_from_rulebook,
        create_design_token,
        list_design_tokens,
        update_design_token,
        delete_design_token,
        set_project_design_system,
    ):
        mcp.tool(name=fn.__name__)(fn)