"""Project management service."""
import logging
from datetime import datetime, timezone

from sqlalchemy import func, select

from fabledassistant.models import async_session
from fabledassistant.models.note import Note
from fabledassistant.models.project import Project, ProjectStatus

logger = logging.getLogger(__name__)


def _validate_status(status: str) -> str:
    """Coerce/validate a project status against ProjectStatus.

    Canonical gate so the MCP create/update_project path (which passes status
    straight through) can't persist an out-of-enum value — there's no DB CHECK.
    """
    try:
        return ProjectStatus(status).value
    except ValueError:
        raise ValueError(
            f"Invalid status: {status!r}. Must be one of: {[s.value for s in ProjectStatus]}"
        )


async def create_project(
    user_id: int,
    title: str,
    description: str = "",
    goal: str = "",
    color: str | None = None,
    status: str = "active",
) -> Project:
    status = _validate_status(status)
    async with async_session() as session:
        project = Project(
            user_id=user_id,
            title=title,
            description=description,
            goal=goal,
            color=color,
            status=status,
        )
        session.add(project)
        await session.commit()
        await session.refresh(project)
        return project


async def get_project(user_id: int, project_id: int) -> Project | None:
    async with async_session() as session:
        result = await session.execute(
            select(Project).where(
                Project.id == project_id, Project.user_id == user_id,
                Project.deleted_at.is_(None),
            )
        )
        return result.scalars().first()


async def get_project_by_title(user_id: int, title: str) -> Project | None:
    async with async_session() as session:
        result = await session.execute(
            select(Project).where(
                Project.user_id == user_id,
                func.lower(Project.title) == func.lower(title.strip()),
                Project.deleted_at.is_(None),
            ).limit(1)
        )
        return result.scalars().first()


async def get_or_create_project(user_id: int, title: str) -> Project:
    project = await get_project_by_title(user_id, title)
    if project:
        return project
    return await create_project(user_id, title=title)


async def list_projects(user_id: int, status: str | None = None) -> list[Project]:
    async with async_session() as session:
        query = select(Project).where(
            Project.user_id == user_id, Project.deleted_at.is_(None)
        )
        if status:
            query = query.where(Project.status == status)
        query = query.order_by(Project.updated_at.desc())
        result = await session.execute(query)
        return list(result.scalars().all())


async def update_project(user_id: int, project_id: int, **fields: object) -> Project | None:
    async with async_session() as session:
        result = await session.execute(
            select(Project).where(
                Project.id == project_id, Project.user_id == user_id,
                Project.deleted_at.is_(None),
            )
        )
        project = result.scalars().first()
        if project is None:
            return None
        if "status" in fields and fields["status"] is not None:
            fields["status"] = _validate_status(fields["status"])
        for key, value in fields.items():
            if hasattr(project, key):
                setattr(project, key, value)
        project.updated_at = datetime.now(timezone.utc)
        await session.commit()
        await session.refresh(project)
    return project


async def delete_project(user_id: int, project_id: int) -> bool:
    async with async_session() as session:
        result = await session.execute(
            select(Project).where(Project.id == project_id, Project.user_id == user_id)
        )
        project = result.scalars().first()
        if project is None:
            return False
        # Unlink notes (cascade handled by DB ON DELETE SET NULL, but we delete project here)
        await session.delete(project)
        await session.commit()
        return True


async def get_project_summary(user_id: int, project_id: int) -> dict:
    """Return task counts by status, note count, and last activity."""
    async with async_session() as session:
        # Task counts by status
        task_rows = await session.execute(
            select(Note.status, func.count(Note.id))
            .where(
                Note.user_id == user_id,
                Note.project_id == project_id,
                Note.status.isnot(None),
                Note.deleted_at.is_(None),
            )
            .group_by(Note.status)
        )
        # Initialise all three lifecycle keys to 0 so consumers can sum them
        # safely without `?? 0` guards. Frontend interface declares all three
        # as required; rendering `undefined + N` yields NaN.
        task_counts: dict[str, int] = {"todo": 0, "in_progress": 0, "done": 0}
        for status, count in task_rows.fetchall():
            task_counts[status] = count

        # Note count (non-tasks)
        note_count_result = await session.scalar(
            select(func.count(Note.id)).where(
                Note.user_id == user_id,
                Note.project_id == project_id,
                Note.status.is_(None),
                Note.deleted_at.is_(None),
            )
        )
        note_count = note_count_result or 0

        # Last activity
        last_activity_result = await session.scalar(
            select(func.max(Note.updated_at)).where(
                Note.user_id == user_id,
                Note.project_id == project_id,
            )
        )

        from fabledassistant.services.milestones import get_project_milestone_summary
        milestone_summary = await get_project_milestone_summary(user_id, project_id)

        return {
            "task_counts": task_counts,
            "note_count": note_count,
            "last_activity": last_activity_result.isoformat() if last_activity_result else None,
            "milestone_summary": milestone_summary,
        }


# ---------------------------------------------------------------------------
# Shared-access variants (honour ProjectShare in addition to ownership)
# ---------------------------------------------------------------------------

async def get_project_for_user(
    accessing_user_id: int, project_id: int
) -> tuple[Project, str] | None:
    """Returns (project, permission) if user has any access, else None."""
    from fabledassistant.services.access import get_project_permission
    perm = await get_project_permission(accessing_user_id, project_id)
    if perm is None:
        return None
    async with async_session() as session:
        project = await session.get(Project, project_id)
    return (project, perm) if project else None


async def list_projects_for_user(user_id: int, status: str | None = None) -> list[dict]:
    """Owned projects + shared projects, each dict has 'permission' field."""
    from fabledassistant.models.group import GroupMembership
    from fabledassistant.models.share import ProjectShare
    from fabledassistant.services.access import PERMISSION_RANK

    owned = await list_projects(user_id, status)
    owned_ids = {p.id for p in owned}

    result = []
    for p in owned:
        d = p.to_dict() if hasattr(p, "to_dict") else {"id": p.id, "title": p.title}
        d["permission"] = "owner"
        result.append(d)

    async with async_session() as session:
        user_group_ids = (await session.execute(
            select(GroupMembership.group_id).where(GroupMembership.user_id == user_id)
        )).scalars().all()

        shared_direct = (await session.execute(
            select(ProjectShare).where(ProjectShare.shared_with_user_id == user_id)
        )).scalars().all()

        shared_group: list[ProjectShare] = []
        if user_group_ids:
            shared_group = (await session.execute(
                select(ProjectShare).where(
                    ProjectShare.shared_with_group_id.in_(user_group_ids)
                )
            )).scalars().all()

    seen: dict[int, str] = {}
    for share in list(shared_direct) + list(shared_group):
        if share.project_id in owned_ids:
            continue
        prev = seen.get(share.project_id)
        if prev is None or PERMISSION_RANK[share.permission] > PERMISSION_RANK[prev]:
            seen[share.project_id] = share.permission

    for pid, perm in seen.items():
        if status:
            async with async_session() as session:
                proj = await session.get(Project, pid)
            if not proj or proj.status != status:
                continue
        else:
            async with async_session() as session:
                proj = await session.get(Project, pid)
        if proj:
            d = proj.to_dict() if hasattr(proj, "to_dict") else {"id": proj.id, "title": proj.title}
            d["permission"] = perm
            d["is_shared"] = True
            result.append(d)

    return result