# domain/validator.py - V7.4 (DOMAIN-AWARE CONSISTENCY GATE)
"""
V7.4 ConsistencyGate: Domain-Aware Validation.

Validates by StepType — NOT by string shape.

  ALGEBRAIC → sympy.sympify() (existing behaviour, unchanged)
  GEOMETRY  → structural validation of payload (list[str])
  NUMERIC   → {future expansion point}

CTO directive:
  - Geometry steps must NEVER reach sympify (Category Error prevention)
  - Geometry gets its own structural validator, not a "skip blind"
  - expression is display-only — validation uses payload for geometry
"""
import sympy
import logging
from typing import List, Tuple
from domain.step_types import StepType, SignedStep

logger = logging.getLogger(__name__)


class ConsistencyGate:
    """
    V7.4 Wall 3: Post-Execution Domain-Aware Consistency Gate.

    Receives the list of SignedStep objects from the Deterministic Solver and
    verifies structural and logical integrity before passing to the Renderer.

    Checks performed (all domains):
    1. Non-empty: at least one signed step exists.
    2. Hash integrity: every step has a non-empty SHA256 hash.
    3a. ALGEBRAIC: expression is SymPy-parseable (sympy.sympify).
    3b. GEOMETRY:  payload is a non-empty list[str] (structural validation).
    """

    @staticmethod
    def _validate_algebraic(step: SignedStep) -> Tuple[bool, str]:
        """
        Validates an ALGEBRAIC step by attempting sympy.sympify on each
        sub-expression (split on " OR " for multi-solution results).
        """
        expr_str = step.expression
        if not expr_str:
            logger.error(f"[CONSISTENCY_GATE] Step '{step.id}' has an empty expression.")
            return False, f"EMPTY_EXPRESSION:{step.id}"

        parts = [p.strip() for p in expr_str.split(" OR ")]
        for part in parts:
            try:
                sympy.sympify(part)
            except Exception as e:
                logger.error(
                    f"[CONSISTENCY_GATE] Step '{step.id}' expression not parseable: "
                    f"'{part}' — {e}"
                )
                return False, f"UNPARSEABLE_EXPRESSION:{step.id}"
        return True, ""

    @staticmethod
    def _validate_geometry(step: SignedStep) -> Tuple[bool, str]:
        """
        Validates a GEOMETRY step structurally via payload.

        Geometry output (points, distances, labels) is NOT SymPy-parseable.
        We verify:
          - payload is a non-empty list
          - every element is a string
        Hash integrity (checked earlier) is the cryptographic guarantee.
        """
        payload = step.payload
        if not isinstance(payload, list) or len(payload) == 0:
            logger.error(
                f"[CONSISTENCY_GATE] Geometry step '{step.id}' has empty or non-list payload."
            )
            return False, f"GEOMETRY_EMPTY_PAYLOAD:{step.id}"
        if not all(isinstance(p, str) for p in payload):
            logger.error(
                f"[CONSISTENCY_GATE] Geometry step '{step.id}' payload contains non-string items."
            )
            return False, f"GEOMETRY_INVALID_PAYLOAD_TYPE:{step.id}"
        logger.info(
            f"[CONSISTENCY_GATE] Geometry step '{step.id}' passed structural validation "
            f"({len(payload)} point(s))."
        )
        return True, ""

    @staticmethod
    def validate(
        signed_steps: List,
        ast_registry: dict,
        problem_id: str
    ) -> Tuple[bool, str]:
        """
        Returns (True, "") if all checks pass.
        Returns (False, reason) if any check fails → caller must Fail Closed.

        Accepts both SignedStep objects and legacy dicts for backwards compatibility
        during any partial migration.
        """
        # Check 1: Non-empty output
        if not signed_steps:
            logger.error("[CONSISTENCY_GATE] No signed steps produced by solver.")
            return False, "EMPTY_SOLVER_OUTPUT"

        for step in signed_steps:
            step_id = step.get("id", "?") if hasattr(step, "get") else step.get("id", "?")

            # Check 2: Hash presence
            h = step.get("hash", "") if hasattr(step, "get") else step.get("hash", "")
            if not h or len(h) < 10:
                logger.error(f"[CONSISTENCY_GATE] Step '{step_id}' is missing a valid SHA256 hash.")
                return False, f"MISSING_HASH:{step_id}"

            # Check 3: Domain-aware expression / payload validation
            step_type = step.get("step_type") if hasattr(step, "get") else None

            if step_type == StepType.GEOMETRY:
                ok, reason = ConsistencyGate._validate_geometry(step)
                if not ok:
                    return False, reason

            elif step_type == StepType.ALGEBRAIC or step_type is None:
                # None = legacy dict without step_type → treat as ALGEBRAIC (backwards compat)
                expr_str = step.get("expression", "")
                if not expr_str:
                    logger.error(f"[CONSISTENCY_GATE] Step '{step_id}' has an empty expression.")
                    return False, f"EMPTY_EXPRESSION:{step_id}"
                parts = [p.strip() for p in expr_str.split(" OR ")]
                for part in parts:
                    try:
                        sympy.sympify(part)
                    except Exception as e:
                        logger.error(
                            f"[CONSISTENCY_GATE] Step '{step_id}' expression not parseable: "
                            f"'{part}' — {e}"
                        )
                        return False, f"UNPARSEABLE_EXPRESSION:{step_id}"

            # StepType.NUMERIC → future expansion point
            # Other unknown types → pass through (hash check is the integrity guarantee)

        logger.info(
            f"[CONSISTENCY_GATE] ✅ {len(signed_steps)} signed steps passed all checks "
            f"for problem '{problem_id}'."
        )
        return True, ""