from __future__ import annotations

from copy import deepcopy
from pathlib import Path
import re
from typing import Any


def _last_executable_prefix(
    cdsl: dict[str, Any],
    failed_feature_id: str | None,
    output: Path,
) -> dict[str, Any] | None:
    """Bind and export the longest verified prefix before a failed feature."""
    from .selector_binding import bind_candidate_selectors
    from engine.cdsl_engine.runtime import rebuild_cdsl

    features = list(cdsl.get("features") or [])
    failed_index = next(
        (index for index, feature in enumerate(features) if feature.get("id") == failed_feature_id),
        len(features),
    )
    for feature_count in range(failed_index, 0, -1):
        prefix = deepcopy(cdsl)
        prefix["features"] = features[:feature_count]
        try:
            bound_prefix, _binding = bind_candidate_selectors(prefix)
            result = rebuild_cdsl(bound_prefix, output, strict=True)
        except Exception:
            continue
        return {
            "failed_feature_id": failed_feature_id,
            "feature_count": feature_count,
            "last_feature_id": str(features[feature_count - 1].get("id") or ""),
            "bound_cdsl": bound_prefix,
            "result": result,
        }
    return None


def _failed_feature_id(error: Exception) -> str | None:
    diagnostic = getattr(error, "diagnostic", None)
    feature_id = getattr(diagnostic, "feature_id", None)
    if isinstance(feature_id, str) and feature_id:
        return feature_id
    match = re.match(r"([^:\s]+): ", str(error))
    return match.group(1) if match else None


def rebuild_candidate(cdsl: dict[str, Any], output: Path) -> dict[str, Any]:
    from engine.cdsl_engine.runtime import analyze_cdsl, rebuild_cdsl
    from .selector_binding import bind_candidate_selectors
    analysis = analyze_cdsl(cdsl)
    analysis_dict = analysis.as_dict() if hasattr(analysis, "as_dict") else {"runtime_eligible": analysis.runtime_eligible}
    if not analysis.runtime_eligible:
        return {"status": "runtime_ineligible", "analysis": analysis_dict}
    bound: dict[str, Any] | None = None
    try:
        bound, binding = bind_candidate_selectors(cdsl)
        result = rebuild_cdsl(bound, output, strict=True)
        return {"status": "rebuilt", "analysis": analysis_dict, "selector_binding": binding, "bound_cdsl": bound, "result": result}
    except Exception as exc:
        detail = {"type": type(exc).__name__, "message": str(exc)}
        if hasattr(exc, "selector_resolutions"): detail["selector_resolutions"] = exc.selector_resolutions
        prefix = _last_executable_prefix(cdsl, _failed_feature_id(exc), output)
        result = {"status": "rebuild_failed", "analysis": analysis_dict, "error": detail}
        if bound is not None: result["bound_cdsl"] = bound
        if prefix is not None: result["last_executable_prefix"] = prefix
        return result