"""ChangeProposal lifecycle: propose (assistant/contributor) → review → apply/reject.

The structural guarantee (CLAUDE.md #1): a proposal's operations are executed
ONLY by ``apply()``, which requires the actor be an editor and dispatches every
op through the normal editing services — so each change passes the privacy
engine and is audited as the approving human. ``propose()`` only inserts a
pending row; it performs no domain mutation. See docs/design/change-proposal.md.
"""

import uuid
from datetime import UTC, datetime

from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession

from app.models.change_proposal import ChangeProposal
from app.models.enums import (
    ChangeProposalOrigin,
    ChangeProposalStatus,
    CitationConfidence,
    ParentChildQualifier,
    RelationshipType,
)
from app.models.tree import Tree
from app.models.user import User
from app.services import (
    citation_service,
    event_service,
    name_service,
    person_service,
    privacy,
    relationship_service,
    source_service,
)
from app.services.exceptions import Conflict, Forbidden, NotFound


def _now() -> datetime:
    return datetime.now(UTC)


def _uuid(v) -> uuid.UUID | None:
    return uuid.UUID(str(v)) if v else None


async def _require_editor(session: AsyncSession, *, actor: User, tree: Tree) -> None:
    if not await privacy.can_edit_tree(session, user_id=actor.id, tree=tree):
        raise Forbidden("not an editor of this tree")


async def _require_member(session: AsyncSession, *, viewer_id: uuid.UUID, tree: Tree) -> None:
    # Proposals can reference unredacted facts → members only.
    if await privacy.get_membership_role(session, viewer_id, tree.id) is None:
        raise Forbidden("only members can see change proposals")


async def _load(
    session: AsyncSession, tree: Tree, proposal_id: uuid.UUID
) -> ChangeProposal:
    cp = (
        await session.execute(
            select(ChangeProposal).where(
                ChangeProposal.id == proposal_id,
                ChangeProposal.tree_id == tree.id,
                ChangeProposal.deleted_at.is_(None),
            )
        )
    ).scalar_one_or_none()
    if cp is None:
        raise NotFound("proposal not found")
    return cp


async def propose(
    session: AsyncSession,
    *,
    tree: Tree,
    origin: ChangeProposalOrigin,
    created_by: uuid.UUID | None,
    summary: str,
    rationale: str | None,
    operations: list[dict],
) -> ChangeProposal:
    """Insert a pending proposal. The ONLY mutation here is the proposal row — no
    tree data changes. (No edit-rights check: proposing isn't writing.)"""
    cp = ChangeProposal(
        tree_id=tree.id,
        origin=origin,
        created_by_user_id=created_by,
        summary=summary,
        rationale=rationale,
        operations=operations,
        status=ChangeProposalStatus.pending,
    )
    session.add(cp)
    await session.commit()
    await session.refresh(cp)
    return cp


async def list_proposals(
    session: AsyncSession,
    *,
    viewer_id: uuid.UUID,
    tree: Tree,
    status: ChangeProposalStatus | None = None,
) -> list[ChangeProposal]:
    await _require_member(session, viewer_id=viewer_id, tree=tree)
    stmt = select(ChangeProposal).where(
        ChangeProposal.tree_id == tree.id, ChangeProposal.deleted_at.is_(None)
    )
    if status is not None:
        stmt = stmt.where(ChangeProposal.status == status)
    stmt = stmt.order_by(ChangeProposal.created_at.desc())
    return list((await session.execute(stmt)).scalars().all())


async def get_proposal(
    session: AsyncSession, *, viewer_id: uuid.UUID, tree: Tree, proposal_id: uuid.UUID
) -> ChangeProposal:
    await _require_member(session, viewer_id=viewer_id, tree=tree)
    return await _load(session, tree, proposal_id)


async def reject(
    session: AsyncSession,
    *,
    actor: User,
    tree: Tree,
    proposal_id: uuid.UUID,
    note: str | None = None,
) -> ChangeProposal:
    await _require_editor(session, actor=actor, tree=tree)
    cp = await _load(session, tree, proposal_id)
    if cp.status is not ChangeProposalStatus.pending:
        raise Conflict("proposal is not pending")
    cp.status = ChangeProposalStatus.rejected
    cp.reviewed_by_user_id = actor.id
    cp.reviewed_at = _now()
    cp.review_note = note
    await session.commit()
    await session.refresh(cp)
    return cp


async def apply(
    session: AsyncSession,
    *,
    actor: User,
    tree: Tree,
    proposal_id: uuid.UUID,
    edited_operations: list[dict] | None = None,
) -> ChangeProposal:
    await _require_editor(session, actor=actor, tree=tree)
    cp = await _load(session, tree, proposal_id)
    if cp.status is not ChangeProposalStatus.pending:
        raise Conflict("proposal is not pending")
    ops = edited_operations if edited_operations is not None else list(cp.operations)
    try:
        for op in ops:
            await _dispatch(session, actor=actor, tree=tree, op=op)
    except Conflict:
        raise
    except Exception as exc:  # noqa: BLE001 — record the failure on the proposal
        err = f"{type(exc).__name__}: {exc}"[:2000]
        # The editing services raise (NotFound/Forbidden/validation) before
        # committing, so the transaction is clean — record the error and commit.
        # If a later op did write before failing, those ops already committed
        # (v1 isn't cross-op transactional; see the design note).
        cp = await _load(session, tree, proposal_id)
        cp.apply_error = err
        await session.commit()
        raise Conflict(f"could not apply proposal: {err}") from exc
    if edited_operations is not None:
        cp.operations = edited_operations
    cp.status = ChangeProposalStatus.applied
    cp.reviewed_by_user_id = actor.id
    cp.reviewed_at = _now()
    cp.apply_error = None
    await session.commit()
    await session.refresh(cp)
    return cp


async def delete_proposal(
    session: AsyncSession, *, actor: User, tree: Tree, proposal_id: uuid.UUID
) -> None:
    await _require_editor(session, actor=actor, tree=tree)
    cp = await _load(session, tree, proposal_id)
    cp.deleted_at = _now()
    await session.commit()


def _bad(entity_type: str, action: str) -> Conflict:
    return Conflict(f"unsupported operation '{action}' on '{entity_type}'")


async def _dispatch(session: AsyncSession, *, actor: User, tree: Tree, op: dict) -> None:
    """Route one operation through the matching editing service (privacy + audit)."""
    et = op.get("entity_type")
    action = op.get("op")
    payload = op.get("payload") or {}
    eid = op.get("entity_id")

    if et == "person":
        if action == "create":
            await person_service.create_person(
                session,
                actor=actor,
                tree=tree,
                given=payload.get("given"),
                surname=payload.get("surname"),
                gender=payload.get("gender"),
                is_living=payload.get("is_living"),
                notes=payload.get("notes"),
            )
        elif action == "update":
            await person_service.update_person(
                session, actor=actor, tree=tree, person_id=_uuid(eid), changes=payload
            )
        elif action == "delete":
            await person_service.delete_person(
                session,
                actor=actor,
                tree=tree,
                person_id=_uuid(eid),
                cascade=bool(payload.get("cascade", False)),
            )
        else:
            raise _bad(et, action)
    elif et == "event":
        if action == "create":
            await event_service.create_event(
                session,
                actor=actor,
                tree=tree,
                event_type=payload["event_type"],
                person_id=_uuid(payload.get("person_id")),
                relationship_id=_uuid(payload.get("relationship_id")),
                date_value=payload.get("date_value"),
                date_precision=payload.get("date_precision"),
                detail=payload.get("detail"),
                notes=payload.get("notes"),
            )
        elif action == "update":
            await event_service.update_event(
                session, actor=actor, tree=tree, event_id=_uuid(eid), changes=payload
            )
        elif action == "delete":
            await event_service.delete_event(
                session, actor=actor, tree=tree, event_id=_uuid(eid)
            )
        else:
            raise _bad(et, action)
    elif et == "relationship":
        if action == "create":
            await relationship_service.create_relationship(
                session,
                actor=actor,
                tree=tree,
                type=RelationshipType(payload["type"]),
                person_from_id=_uuid(payload["person_from_id"]),
                person_to_id=_uuid(payload["person_to_id"]),
                qualifier=ParentChildQualifier(payload["qualifier"])
                if payload.get("qualifier")
                else None,
                notes=payload.get("notes"),
            )
        elif action == "delete":
            await relationship_service.delete_relationship(
                session, actor=actor, tree=tree, relationship_id=_uuid(eid)
            )
        else:
            raise _bad(et, action)
    elif et == "name":
        if action == "create":
            await name_service.create_name(
                session,
                actor=actor,
                tree=tree,
                person_id=_uuid(payload["person_id"]),
                name_type=payload.get("name_type", "birth"),
                given=payload.get("given"),
                surname=payload.get("surname"),
                prefix=payload.get("prefix"),
                suffix=payload.get("suffix"),
                nickname=payload.get("nickname"),
                is_primary=bool(payload.get("is_primary", False)),
            )
        elif action == "update":
            changes = {k: v for k, v in payload.items() if k != "person_id"}
            await name_service.update_name(
                session,
                actor=actor,
                tree=tree,
                person_id=_uuid(payload["person_id"]),
                name_id=_uuid(eid),
                changes=changes,
            )
        elif action == "delete":
            await name_service.delete_name(
                session,
                actor=actor,
                tree=tree,
                person_id=_uuid(payload["person_id"]),
                name_id=_uuid(eid),
            )
        else:
            raise _bad(et, action)
    elif et == "source":
        if action == "create":
            await source_service.create_source(
                session,
                actor=actor,
                tree=tree,
                title=payload["title"],
                author=payload.get("author"),
                source_type=payload.get("source_type"),
                repository=payload.get("repository"),
                url=payload.get("url"),
                citation_text=payload.get("citation_text"),
                publication_info=payload.get("publication_info"),
                quality_note=payload.get("quality_note"),
            )
        elif action == "delete":
            await source_service.delete_source(
                session, actor=actor, tree=tree, source_id=_uuid(eid)
            )
        else:
            raise _bad(et, action)
    elif et == "citation":
        if action == "create":
            await citation_service.create_citation(
                session,
                actor=actor,
                tree=tree,
                source_id=_uuid(payload["source_id"]),
                person_id=_uuid(payload.get("person_id")),
                event_id=_uuid(payload.get("event_id")),
                name_id=_uuid(payload.get("name_id")),
                relationship_id=_uuid(payload.get("relationship_id")),
                page=payload.get("page"),
                detail=payload.get("detail"),
                confidence=CitationConfidence(payload["confidence"])
                if payload.get("confidence")
                else None,
            )
        elif action == "delete":
            await citation_service.delete_citation(
                session, actor=actor, tree=tree, citation_id=_uuid(eid)
            )
        else:
            raise _bad(et, action)
    else:
        raise Conflict(f"unsupported entity type '{et}'")