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
from scribe.services.design_starter_roles import (
    ALL_GROUPS,
    DEFAULT_TOKEN_PREFIX,
    describe_groups,
)


async def create_design_system(
    title: str,
    description: str = "",
    guidance: str = "",
    parent_id: int = 0,
    starter_role_groups: list[str] | None = None,
    token_prefix: str = "",
) -> dict:
    """Create a design system, optionally inheriting from another.

    This — not a rulebook — is where visual standards live: a token can be
    inherited, resolved per mode, rendered to a stylesheet and checked against
    code, and none of that survives being written as rule prose. Once a
    project points at one (set_project_design_system), treat it as binding for
    that project's UI work.

    Args:
        title: What this system is — a house style, or one app within it
            (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.
        starter_role_groups: Seed the system with named but VALUELESS token
            roles, so there is something to reach for before a literal gets
            written instead. Call list_starter_role_groups() for the catalogue.
            Pass ["all"] for every group. Omit for none — a system with three
            hand-written tokens is a legitimate design system.
        token_prefix: Naming convention for the seeded roles, e.g. "--fs-".
            Defaults to a neutral "--ds-"; pass the install's own if it has one.
            Ignored when no starter groups are requested.
    """
    uid = current_user_id()
    groups = starter_role_groups
    if groups and len(groups) == 1 and groups[0] == "all":
        groups = list(ALL_GROUPS)
    system = await ds_svc.create_design_system(
        uid,
        title=title,
        description=description or None,
        guidance=guidance or None,
        parent_id=parent_id or None,
        starter_role_groups=groups,
        token_prefix=token_prefix or DEFAULT_TOKEN_PREFIX,
    )
    if system is None:
        raise ValueError(f"parent design system {parent_id} not found or not writable")
    return system.to_dict()


async def list_starter_role_groups() -> dict:
    """The starter token ROLES offered at design-system creation.

    Roles, not values. Every group is a set of named questions — "page
    background, the deepest surface" — that the operator answers with their own
    palette. Nothing here carries a colour, because a default palette would be
    one install's taste shipped as product.

    Reach for this before create_design_system so the choice is informed, and
    pass the group names you want as `starter_role_groups`.
    """
    return {"groups": describe_groups(), "default_prefix": DEFAULT_TOKEN_PREFIX}


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.

    `resolved_guidance` is the prose to build UI from: the guidance of every
    system in the inheritance chain, outermost ancestor first, so the house
    style comes before this system's departures from it. `design_system`'s
    own `guidance` field is only the departures. Read `resolved_guidance`
    before writing UI; enter_project carries just the summary (#4045).
    """
    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)
    context = await ds_svc.design_context(uid, design_system_id)
    return {
        "design_system": system.to_dict(),
        "resolved_guidance": context["guidance"] if context else [],
        "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


# ── 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. "--surface-page" (required).
            Name it for its PURPOSE, not its value: a name like "--obsidian"
            or "--button-bg" stops being true the moment the value or the
            element changes.
        value_by_mode: Values keyed by mode, e.g.
            {"base": "#14171a", "light": "#f7f5ef"}. 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 background, deepest
            surface".
        rationale: WHY it is this value — a different question from purpose.
            "Deliberately the same value as the primary action colour" is a
            rationale; "page background, 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_starter_role_groups,
        list_design_systems,
        get_design_system,
        resolve_design_system,
        update_design_system,
        delete_design_system,
        get_design_system_stylesheet,
        check_snippets_against_design_system,
        create_design_token,
        list_design_tokens,
        update_design_token,
        delete_design_token,
        set_project_design_system,
    ):
        mcp.tool(name=fn.__name__)(fn)