"""Constraint / world feasibility checks for interventions (``docs/02`` §10).

CLEAN_DELETE_V1 (§10.3) and SUBSTITUTE_V1 on a geometry world (§10.4 "geometry:
constraint satisfiable") must reject a transformation that leaves the world
ill-formed — a dangling reference after a delete, or a contradictory stating
constraint after a substitute. Full theorem-proving satisfiability is the P13
reference executor's job; here "feasible" means **structurally well-formed and
free of direct contradictions** the executor would trip over: no dangling
entity references, no two stating constraints assigning different values to the
same entity, and the plot/table shape intact.

An infeasible world is reported via :class:`FeasibilityError` (a typed reject)
so an operator never emits a broken world silently (P5 gate: "invalid
geometry/plot mutation reject").
"""

from __future__ import annotations

from ..dsl.ast import Dsl, parse_number
from ..ingest.base import IngestError
from ..sources.base import World
from ..sources.world_ops import is_geometry, is_plot, is_table, looks_numeric


class FeasibilityError(IngestError):
    """A world is ill-formed / self-contradictory after a transformation."""


def is_feasible(world: World, *, dsl: Dsl) -> bool:
    """True iff ``world`` is structurally well-formed for ``dsl``.

    Raises :class:`FeasibilityError` (carrying the reason) when infeasible, so a
    caller can distinguish "reject" from "feasible". Returns ``True`` otherwise.
    """
    if is_plot(world):
        _check_plot(world)
    elif is_table(world):
        _check_table(world)
    elif is_geometry(world):
        _check_geometry(world)
    else:
        raise FeasibilityError(f"unknown world shape for dsl {dsl!r}")
    return True


def _check_plot(world: World) -> None:
    series = world.get("series", []) or []
    if not isinstance(series, list):
        raise FeasibilityError("plot world `series` is not a list")
    seen_points: set[str] = set()
    for s in series:
        if not isinstance(s, dict) or not s.get("id"):
            raise FeasibilityError("plot series missing an id")
        for p in s.get("points", []) or []:
            if not isinstance(p, dict) or not p.get("id"):
                raise FeasibilityError("plot point missing an id")
            if "x" not in p or "y" not in p:
                raise FeasibilityError(f"plot point {p.get('id')} missing x/y")
            if p["id"] in seen_points:
                raise FeasibilityError(f"duplicate plot point id {p['id']}")
            seen_points.add(p["id"])


def _check_table(world: World) -> None:
    rows = world.get("rows", []) or []
    if not isinstance(rows, list):
        raise FeasibilityError("table world `rows` is not a list")
    seen: set[str] = set()
    for r in rows:
        if not isinstance(r, dict) or not r.get("id"):
            raise FeasibilityError("table row missing an id")
        if r["id"] in seen:
            raise FeasibilityError(f"duplicate table row id {r['id']}")
        seen.add(r["id"])


def _check_geometry(world: World) -> None:
    entities = world.get("entities", []) or []
    entity_ids = {str(e.get("id")) for e in entities if isinstance(e, dict) and e.get("id")}
    constraints = world.get("constraints", []) or []
    if not isinstance(constraints, list):
        raise FeasibilityError("geometry world `constraints` is not a list")

    # 1. No dangling non-numeric reference: every string arg that is not a
    #    numeric literal must name a known entity.
    for c in constraints:
        if not isinstance(c, dict) or not c.get("predicate"):
            raise FeasibilityError("geometry constraint missing a predicate")
        for arg in c.get("args", []) or []:
            if isinstance(arg, str) and not looks_numeric(arg) and arg not in entity_ids:
                raise FeasibilityError(
                    f"constraint {c.get('predicate')} references unknown entity {arg!r}"
                )

    # 2. No conflicting stating constraints: at most one value per entity from
    #    MeasureOf / Equals (a substitute that creates a second, different value
    #    is a direct contradiction the executor cannot resolve).
    stated: dict[str, str] = {}
    for c in constraints:
        pred = c.get("predicate")
        args = c.get("args") or []
        if pred == "MeasureOf" and len(args) >= 2 and looks_numeric(args[1]):
            _record_stated(stated, str(args[0]), str(args[1]), pred)
        elif pred == "Equals" and len(args) == 2:
            if looks_numeric(args[1]) and not looks_numeric(args[0]):
                _record_stated(stated, str(args[0]), str(args[1]), pred)
            elif looks_numeric(args[0]) and not looks_numeric(args[1]):
                _record_stated(stated, str(args[1]), str(args[0]), pred)


def _record_stated(stated: dict[str, str], entity: str, value: str, pred: str) -> None:
    canonical = _num(value)
    if entity in stated and stated[entity] != canonical:
        raise FeasibilityError(
            f"entity {entity!r} is stated twice with conflicting values "
            f"({stated[entity]} vs {canonical}) via {pred}"
        )
    stated[entity] = canonical


def _num(text: str) -> str:
    try:
        return str(parse_number(text))
    except (ValueError, ZeroDivisionError):
        return text


__all__ = ["FeasibilityError", "is_feasible"]