"""Platforms — what a project is built on or ships as, and which projects are
which (milestone 463 step 2).

Membership is what makes "is this idea in family for that project?" a lookup
rather than a judgment: a family idea is for some platforms, and it reaches
every project that is a member of one of them.

Three ways a project becomes, or refuses to become, a member:

- **declared** — a person said so: at inception, or in the project's settings.
- **detected** — a marker file in a bound repo said so, found by the coverage
  refresh that already walks the repo archive.
- **rejected** — a person said NO. Kept as a row, so the next refresh does not
  detect it straight back.

The one invariant everything here protects: **detection only ever ADDS, and
only where nobody has answered.** It never overwrites a declared or rejected
row, and it never removes anything — not even a detected row whose marker has
since disappeared, because membership is what adoption rows hang off and a
platform flickering in and out with a repo's file tree would churn a ledger
of decisions nobody re-made.

The catalog itself is global, like the canonical area catalog, and for the
same reason writes to it are admin-only: a shared vocabulary anyone can extend
stops being shared. Reads are open to any signed-in user.
"""
from __future__ import annotations

import fnmatch
import logging
from datetime import datetime, timezone

from sqlalchemy import select

from scribe.models import async_session
from scribe.models.family import Platform, ProjectPlatform
from scribe.services import access
from scribe.services.canonical_systems import canonical_slug

logger = logging.getLogger(__name__)

# The states that make a project a member. `rejected` is an answer, not
# membership.
MEMBER_STATES = ("declared", "detected")
# What a person may set from a door. `detected` is the refresh's to write.
SETTABLE_STATES = ("declared", "rejected")


# --- the catalog -------------------------------------------------------------

async def list_platforms() -> list[Platform]:
    """The whole live catalog, in display order. Global — no owner filter."""
    async with async_session() as session:
        result = await session.execute(
            select(Platform)
            .where(Platform.deleted_at.is_(None))
            .order_by(Platform.order_index.asc(), Platform.name.asc())
        )
        return list(result.scalars().all())


def _clean_markers(markers) -> list[str]:
    """Markers as stored: stripped, non-empty strings, de-duplicated in order.
    Anything else is refused by the caller before it gets here."""
    seen: list[str] = []
    for m in markers or []:
        m = str(m).strip()
        if m and m not in seen:
            seen.append(m)
    return seen


def validate_markers(markers) -> str | None:
    """The error a markers value would earn, or None. Pure."""
    if markers is None:
        return None
    if not isinstance(markers, list) or not all(isinstance(m, str) for m in markers):
        return "markers must be a list of glob patterns"
    if any(m.strip().startswith("/") for m in markers):
        return "markers are repo-relative — no leading slash"
    return None


async def create_platform(
    user_id: int, name: str, *, description: str | None = None,
    markers: list[str] | None = None,
) -> Platform | dict | None:
    """Add a platform to the global catalog. Admin only.

    Duplicate-gated on the slug, so "Android App" cannot be added beside
    "Android app": the existing entry comes back instead of a second spelling
    of it. None means not permitted, or no usable name.
    """
    if not await access.is_instance_admin(user_id):
        return None
    slug = canonical_slug(name)
    if not slug:
        return None
    error = validate_markers(markers)
    if error:
        raise ValueError(error)
    async with async_session() as session:
        existing = await session.scalar(
            select(Platform).where(Platform.slug == slug, Platform.deleted_at.is_(None))
        )
        if existing is not None:
            return {
                "duplicate": True,
                "existing_id": existing.id,
                "message": (
                    f"'{existing.name}' (#{existing.id}) is already this platform — "
                    f"both names reduce to '{slug}'."
                ),
            }
        highest = await session.scalar(
            select(Platform.order_index).order_by(Platform.order_index.desc()).limit(1)
        )
        entry = Platform(
            name=" ".join(name.split()),
            slug=slug,
            description=description,
            markers=_clean_markers(markers),
            order_index=(highest or 0) + 1,
        )
        session.add(entry)
        await session.commit()
        await session.refresh(entry)
        return entry


async def update_platform(user_id: int, platform_id: int, **fields: object) -> Platform | None:
    """Rename, re-describe, re-order or re-mark a catalog entry. Admin only.

    A rename recomputes the slug — the display name and the match key must not
    disagree. Changing the slug of a platform projects already belong to is
    safe: membership is by id; only a backup carries the slug.
    """
    if not await access.is_instance_admin(user_id):
        return None
    if "markers" in fields:
        error = validate_markers(fields["markers"])
        if error:
            raise ValueError(error)
    async with async_session() as session:
        entry = await session.get(Platform, platform_id)
        if entry is None or entry.deleted_at is not None:
            return None
        if fields.get("name"):
            entry.name = " ".join(str(fields["name"]).split())
            entry.slug = canonical_slug(entry.name)
        if fields.get("description") is not None:
            entry.description = fields["description"] or None
        if fields.get("order_index") is not None:
            entry.order_index = int(fields["order_index"])
        if fields.get("markers") is not None:
            entry.markers = _clean_markers(fields["markers"])
        entry.updated_at = datetime.now(timezone.utc)
        await session.commit()
        await session.refresh(entry)
        return entry


async def resolve_slugs(slugs: list[str]) -> tuple[dict[str, int], list[str]]:
    """{slug: id} for the slugs the live catalog knows, and the ones it does
    not. Doors take slugs — readable, stable across installs, and the form an
    inception record and a backup both carry."""
    wanted = [s for s in dict.fromkeys(slugs or [])]
    if not wanted:
        return {}, []
    async with async_session() as session:
        rows = (await session.execute(
            select(Platform.slug, Platform.id).where(
                Platform.slug.in_(wanted), Platform.deleted_at.is_(None),
            )
        )).all()
    known = {slug: pid for slug, pid in rows}
    return known, [s for s in wanted if s not in known]


# --- detection (pure) --------------------------------------------------------

def marker_matches(marker: str, path: str) -> bool:
    """Whether one marker matches one repo-relative path.

    A marker with no slash matches a file's BASENAME anywhere in the tree
    (`go.mod`, `AndroidManifest.xml`, `vite.config.*`). A marker with a slash
    matches the whole repo-relative path (`.github/workflows/*`), so a
    directory-shaped marker cannot be satisfied by a same-named file
    somewhere else.
    """
    marker = marker.strip()
    if not marker:
        return False
    if "/" in marker:
        return fnmatch.fnmatchcase(path, marker)
    return fnmatch.fnmatchcase(path.rsplit("/", 1)[-1], marker)


def detect(catalog: list, paths: list[str]) -> list[int]:
    """The ids of every catalog platform at least one of whose markers matches
    at least one path. Pure, so it is testable against a fixture tree with no
    forge and no database. A platform with no markers is never detected —
    that is what declare-only means."""
    hits: list[int] = []
    for platform in catalog:
        markers = list(getattr(platform, "markers", None) or [])
        if markers and any(marker_matches(m, p) for m in markers for p in paths):
            hits.append(platform.id)
    return hits


# --- membership ----------------------------------------------------------------

async def project_platforms(user_id: int, project_id: int) -> list[dict] | None:
    """Every platform the project has an answer for, joined to the catalog.
    None when the caller cannot read the project.

    Rejected rows are included — a settings screen has to show "no" as well
    as "yes", or it cannot let anyone change their mind.
    """
    if not await access.can_read_project(user_id, project_id):
        return None
    async with async_session() as session:
        rows = (await session.execute(
            select(ProjectPlatform, Platform)
            .join(Platform, Platform.id == ProjectPlatform.platform_id)
            .where(ProjectPlatform.project_id == project_id, Platform.deleted_at.is_(None))
            .order_by(Platform.order_index.asc(), Platform.name.asc())
        )).all()
    return [
        {"id": p.id, "slug": p.slug, "name": p.name, "state": m.state}
        for m, p in rows
    ]


def members(platforms: list[dict]) -> list[dict]:
    """The rows of `project_platforms` that are membership — the brief form
    enter_project and get_project carry."""
    return [
        {"slug": p["slug"], "name": p["name"], "state": p["state"]}
        for p in platforms if p["state"] in MEMBER_STATES
    ]


def validate_updates(updates) -> str | None:
    """The error a set of membership answers would earn, or None. Pure.

    `updates` is {slug: "declared" | "rejected" | None}. None withdraws the
    answer — the row goes, and detection may add the platform again later.
    `detected` is not settable: it is what the refresh writes, and a person
    claiming it would erase the difference between the two."""
    if not isinstance(updates, dict):
        return "platforms must be an object of {slug: state}"
    for slug, state in updates.items():
        if not isinstance(slug, str) or not slug:
            return "each platform is named by its slug"
        if state is not None and state not in SETTABLE_STATES:
            return (
                f"'{state}' is not a state a person sets — use one of "
                f"{', '.join(SETTABLE_STATES)}, or null to withdraw the answer"
            )
    return None


async def set_project_platforms(
    user_id: int, project_id: int, updates: dict[str, str | None],
) -> list[dict]:
    """Apply a person's answers about a project's platforms. Write-gated on
    the project (rule 78). Platforms not named are left exactly as they are.

    Raises ValueError, naming the problem, on a malformed update, an unknown
    slug, or no write access — before anything is written, so the update
    applies whole or not at all.
    """
    error = validate_updates(updates)
    if error:
        raise ValueError(error)
    if not await access.can_write_project(user_id, project_id):
        raise ValueError(f"project {project_id} not found or no write access")
    known, unknown = await resolve_slugs(list(updates))
    if unknown:
        raise ValueError(f"unknown platform(s): {', '.join(unknown)} (list_platforms)")
    async with async_session() as session:
        existing = {
            row.platform_id: row for row in (await session.execute(
                select(ProjectPlatform).where(ProjectPlatform.project_id == project_id)
            )).scalars().all()
        }
        for slug, state in updates.items():
            pid = known[slug]
            row = existing.get(pid)
            if state is None:
                if row is not None:
                    await session.delete(row)
            elif row is None:
                session.add(ProjectPlatform(project_id=project_id, platform_id=pid, state=state))
            else:
                row.state = state
        await session.commit()
    return await project_platforms(user_id, project_id) or []


async def record_detected(project_id: int, platform_ids: list[int]) -> list[int]:
    """Add `detected` membership for each platform the project has NO answer
    for. Returns the ids actually added.

    The refresh's writer, so it takes no user: it runs on the owner's behalf
    inside a sync the owner's keyring authorised. It never updates or deletes
    a row — see the module docstring for why that is the whole contract.
    """
    if not platform_ids:
        return []
    async with async_session() as session:
        answered = set((await session.execute(
            select(ProjectPlatform.platform_id).where(
                ProjectPlatform.project_id == project_id,
            )
        )).scalars().all())
        added = [pid for pid in dict.fromkeys(platform_ids) if pid not in answered]
        for pid in added:
            session.add(ProjectPlatform(project_id=project_id, platform_id=pid, state="detected"))
        await session.commit()
    return added


async def detect_for_project(project_id: int, paths: list[str]) -> list[int]:
    """Run detection over a refresh's paths and record what is new. The
    coverage refresh's single call — it must not be able to fail that
    refresh, so the caller wraps it."""
    hits = detect(await list_platforms(), paths)
    added = await record_detected(project_id, hits)
    if added:
        logger.info("project %s: detected platform(s) %s", project_id, added)
    return added