"""Shared, pure helpers for locating and inspecting structured-world nodes.

A *world* (``docs/02`` §6) is a plain JSON-serializable mapping —
``plot_world_v1`` / ``geometry_world_v1`` / ``table_world_v1``. Both the C2
mutation suite (``docs/02`` §7.3) and the P5 intervention operators
(``docs/02`` §10) need to find a node by stable id, tell the world kinds apart,
and hash a world deterministically. Those helpers live here once so the two
layers stay consistent and neither reaches into the other's privates.

Everything here is **read-only** over the passed world and never mutates it; the
caller is responsible for ``copy.deepcopy`` when it wants a mutable copy (see
:func:`clone_world`).
"""

from __future__ import annotations

import copy
from typing import Any

from ..hashing import canonical_json_hash
from .base import World

# The reserved top-level marker a transformed world carries to record which
# semantic nodes a renderer must hide (``docs/02`` §10.1 REDACT_SOLID_V1). It is
# intentionally namespaced so executors — which read only ``series`` /
# ``constraints`` / ``rows`` — ignore it, while the renderer (P6) reads it.
NODE_VISIBILITY_KEY = "_node_visibility"


def clone_world(world: World) -> World:
    """A deep, independent copy of ``world`` (the source stays immutable)."""
    return copy.deepcopy(world)


def hidden_nodes(world: World) -> frozenset[str]:
    """The node ids a world marks hidden (``frozenset()`` when none).

    A pure read of the reserved :data:`NODE_VISIBILITY_KEY` map; executors
    ignore it, the renderer (P6) consumes it for REDACT_SOLID_V1 (§10.1).
    """
    vis = world.get(NODE_VISIBILITY_KEY, {}) or {}
    return frozenset(nid for nid, state in vis.items() if state == "hidden")


def world_sha256(world: World) -> str:
    """Content-addressed hash of a world (canonical-JSON, deterministic).

    The same world bytes always reproduce the same hash, so a transformed
    world's identity is byte-stable across runs (``docs/07`` §7 P5 gate:
    "seed/operation → same transformed world hash").
    """
    return canonical_json_hash(world)


def world_kind(world: World) -> str:
    """The world family: ``"plot"`` / ``"table"`` / ``"geometry"`` / ``"unknown"``."""
    if is_plot(world):
        return "plot"
    if is_table(world):
        return "table"
    if is_geometry(world):
        return "geometry"
    return "unknown"


def is_plot(world: World) -> bool:
    return "series" in world


def is_table(world: World) -> bool:
    return "rows" in world


def is_geometry(world: World) -> bool:
    return "constraints" in world or "entities" in world


def looks_numeric(text: Any) -> bool:
    """True if ``text`` parses as an exact number (``Fraction``-compatible)."""
    from ..dsl.ast import parse_number  # local: avoids a dsl import cycle at load

    try:
        parse_number(str(text))
    except (ValueError, ZeroDivisionError):
        return False
    return True


# --- node locators ---------------------------------------------------------


def find_point(world: World, pid: str) -> tuple[int, int, dict[str, Any]] | None:
    """Locate a plot point by id → ``(series_idx, point_idx, point_dict)``."""
    for sidx, s in enumerate(world.get("series", []) or []):
        for pidx, p in enumerate(s.get("points", []) or []):
            if isinstance(p, dict) and p.get("id") == pid:
                return sidx, pidx, p
    return None


def find_series(world: World, sid: str) -> tuple[int, dict[str, Any]] | None:
    for sidx, s in enumerate(world.get("series", []) or []):
        if isinstance(s, dict) and s.get("id") == sid:
            return sidx, s
    return None


def find_row(world: World, rid: str) -> tuple[int, dict[str, Any]] | None:
    for ridx, r in enumerate(world.get("rows", []) or []):
        if isinstance(r, dict) and r.get("id") == rid:
            return ridx, r
    return None


def find_stating_constraint(world: World, entity: str) -> tuple[int, dict[str, Any]] | None:
    """The constraint that states ``entity``'s value (``MeasureOf``/``Equals``)."""
    for cidx, c in enumerate(world.get("constraints", []) or []):
        if not isinstance(c, dict):
            continue
        pred = c.get("predicate")
        args = c.get("args") or []
        if pred == "MeasureOf" and len(args) >= 2 and str(args[0]) == entity:
            return cidx, c
        if pred == "Equals" and len(args) == 2:
            a, b = str(args[0]), str(args[1])
            if a == entity and looks_numeric(b):
                return cidx, c
            if b == entity and looks_numeric(a):
                return cidx, c
    return None


def node_kind(world: World, node_id: str) -> str | None:
    """The semantic kind of a node id: ``point``/``series``/``row``/``entity``/``constraint``.

    ``None`` when the id is not present. Used by CONTROL_MATCHED_V1 to match on
    visual type (``docs/02`` §10.5) via a semantic proxy (no pixels until P6).
    """
    if is_plot(world):
        if find_point(world, node_id) is not None:
            return "point"
        if find_series(world, node_id) is not None:
            return "series"
    if is_table(world) and find_row(world, node_id) is not None:
        return "row"
    if is_geometry(world):
        if find_stating_constraint(world, node_id) is not None:
            return "constraint"
        if any(e.get("id") == node_id for e in world.get("entities", []) or []):
            return "entity"
    return None


__all__ = [
    "NODE_VISIBILITY_KEY",
    "clone_world",
    "find_point",
    "find_row",
    "find_series",
    "find_stating_constraint",
    "hidden_nodes",
    "is_geometry",
    "is_plot",
    "is_table",
    "looks_numeric",
    "node_kind",
    "world_kind",
    "world_sha256",
]