"""
Surgical forget — prune orphaned dead-ends from graph **and** vector stores.

After :mod:`falsify.tasks.propagate_refutation` marks nodes ``refuted`` /
``invalidated``, some of those nodes are still useful: they explain *why* a belief
changed (provenance) or they still feed a node that is alive. Others are pure
dead-ends with no surviving consumer. FALSIFY hard-deletes only the latter, from
both the graph (``delete_nodes``) and the vector index (``delete_data_points``), so a
subsequent ``recall()`` — and even a raw vector search — can never resurface them.

Orphan rule (REQUIREMENTS §1.5) — a node is FORGOTTEN iff ALL hold:
    (a) truth state is ``refuted`` or ``invalidated`` (never ``alive``/``superseded``;
        superseded nodes are kept as provenance), AND
    (b) no surviving ALIVE node reaches it via ``depends_on`` or ``supports``
        (it has no live consumer), AND
    (c) it is NOT the target of a ``supersedes`` edge FROM an alive node (such a node
        is the provenance anchor of the new truth and must be retained as a tombstone).

The asymmetry is deliberate and is what makes FALSIFY look *surgical*: in the demo the
orphaned Conclusion K is deleted, while the refuted Evidence E_qa is kept — flagged
red — because it is the supersedes-anchor of the new fact.
"""

from __future__ import annotations

import logging
from dataclasses import dataclass, field
from typing import Dict, List, Set

from falsify import graph_ops
from falsify.edges import CONSUMER_EDGE_TYPES, SUPERSEDES
from falsify.models import (
    Conclusion,
    Evidence,
    TruthState,
)

logger = logging.getLogger("falsify.forget")

_DELETABLE_STATES = {TruthState.REFUTED.value, TruthState.INVALIDATED.value}
_ALIVE = TruthState.ALIVE.value

# Vector collections FALSIFY writes to (``"{ClassName}_{embeddable_field}"``).
# Deleting an id from a collection it isn't in is a best-effort no-op.
_VECTOR_COLLECTIONS = [
    "Evidence_claim",
    "Conclusion_statement",
    "Hypothesis_statement",
    "Assertion_text",
    "InvestigationQuestion_question",
]


@dataclass
class ForgetResult:
    """Outcome of a forget pass.

    Attributes:
        forgotten: node ids hard-deleted from graph + vector.
        retained_provenance: refuted/invalidated ids deliberately kept (a supersedes
            anchor, or still feeding a live node).
        labels: id -> human label for the forgotten nodes (for demo output).
    """

    forgotten: List[str] = field(default_factory=list)
    retained_provenance: List[str] = field(default_factory=list)
    labels: Dict[str, str] = field(default_factory=dict)


async def _alive_consumer_exists(node_id: str, edges, truth: Dict[str, List[str]]) -> bool:
    """True if some ALIVE node reaches ``node_id`` via depends_on/supports.

    ``depends_on`` (Conclusion->Evidence) and ``supports`` (Evidence->Hypothesis) both
    point *from consumer to the thing consumed*, so an incoming edge's **source** is a
    consumer of ``node_id``.
    """
    nid = str(node_id)
    for rel in CONSUMER_EDGE_TYPES:
        for src, _props in graph_ops.incoming(nid, edges, rel):
            alignment = truth.get(str(src), [_ALIVE])
            if _ALIVE in alignment:
                return True
    return False


def _is_supersedes_anchor(node_id: str, edges, truth: Dict[str, List[str]]) -> bool:
    """True if ``node_id`` is the target of a ``supersedes`` edge from an ALIVE node.

    That alive source is the new, current truth; the target is its tombstone and must
    be retained as provenance.
    """
    nid = str(node_id)
    for src, _props in graph_ops.incoming(nid, edges, SUPERSEDES):
        alignment = truth.get(str(src), [_ALIVE])
        if _ALIVE in alignment:
            return True
    return False


async def cascade_forget(candidate_ids: List[str]) -> ForgetResult:
    """Delete truly-orphaned dead-ends among ``candidate_ids``; keep provenance.

    Args:
        candidate_ids: nodes marked refuted/invalidated by a preceding cascade.

    Returns:
        A :class:`ForgetResult`. Deleted nodes are removed from the graph and from
        every FALSIFY vector collection, so no retrieval path can resurface them.
    """
    result = ForgetResult()
    candidates = [str(c) for c in dict.fromkeys(candidate_ids) if c]
    if not candidates:
        return result

    nodes, edges = await graph_ops.load_graph()
    props_by_id = {str(nid): (props or {}) for nid, props in nodes}

    # Current truth for candidates + their neighbors (consumers/anchors).
    neighbor_ids: Set[str] = set(candidates)
    for cid in candidates:
        for rel in (*CONSUMER_EDGE_TYPES, SUPERSEDES):
            neighbor_ids.update(str(s) for s, _p in graph_ops.incoming(cid, edges, rel))
    truth = await graph_ops.get_truth(list(neighbor_ids))

    death_set: List[str] = []
    for cid in candidates:
        alignment = truth.get(cid, [_ALIVE])

        # (a) must be refuted/invalidated
        if not any(state in _DELETABLE_STATES for state in alignment):
            continue
        # (c) keep supersedes anchors (provenance tombstones)
        if _is_supersedes_anchor(cid, edges, truth):
            result.retained_provenance.append(cid)
            logger.info("retained %s as supersedes provenance anchor", cid)
            continue
        # (b) keep nodes that still feed a live consumer
        if await _alive_consumer_exists(cid, edges, truth):
            result.retained_provenance.append(cid)
            logger.info("retained %s (still feeds a live node)", cid)
            continue

        death_set.append(cid)
        result.labels[cid] = graph_ops.node_label(props_by_id.get(cid, {}))

    if not death_set:
        logger.info("forget pass: nothing orphaned; %d provenance nodes retained",
                    len(result.retained_provenance))
        return result

    # Hard-delete from graph + all vector collections in one batch.
    deleted = await graph_ops.delete_from_both_stores(death_set, _VECTOR_COLLECTIONS)
    result.forgotten = death_set
    logger.info(
        "forget pass: hard-deleted %d orphan(s) from graph + vector; retained %d provenance",
        deleted,
        len(result.retained_provenance),
    )
    return result