import json
import re
from pathlib import Path
from typing import List, Optional, Union


def _extract_recommendation_items(text: str) -> List[str]:
    """Extract compact recommendation items from numbered or bulleted text."""
    if not isinstance(text, str):
        return []

    items: List[str] = []
    for raw_line in text.splitlines():
        line = raw_line.strip()
        if not line:
            continue
        if re.match(r"^\d+\.\s+", line) or line.startswith("- ") or line.startswith("•"):
            items.append(line)
    return items


def build_meta_recommendation_context_lines(
    results_dir: Union[str, Path],
    max_current_items: int = 5,
    max_delta_items: int = 3,
) -> Optional[List[str]]:
    """
    Build prompt lines describing current evolution-agent strategy from meta memory.

    Reads `meta_memory.json` under results_dir and returns a compact section with:
    - current recommendations used by the evolution loop
    - best-effort delta vs the previous recommendation refresh
    """
    base_path = Path(results_dir)
    if base_path.name == "meta_memory.json":
        meta_path = base_path
    else:
        meta_path = base_path / "meta_memory.json"
    if not meta_path.exists():
        return None

    try:
        with open(meta_path, "r", encoding="utf-8") as f:
            meta_data = json.load(f)
    except Exception:
        return None

    current_recs = meta_data.get("meta_recommendations")
    history = meta_data.get("meta_recommendations_history", [])
    if not isinstance(current_recs, str) or not current_recs.strip():
        return None

    latest_items = _extract_recommendation_items(current_recs)
    previous_recs = history[-2] if isinstance(history, list) and len(history) >= 2 else ""
    previous_items = set(_extract_recommendation_items(previous_recs))
    improvement_items = [item for item in latest_items if item not in previous_items]

    context_lines: List[str] = [
        "",
        "🧭 Evolution Agent Strategy Context (from meta memory):",
        f"- Source: {meta_path}",
        "- Current recommendations used by evolution agent:",
    ]

    if latest_items:
        for item in latest_items[:max_current_items]:
            context_lines.append(f"  {item}")
    else:
        trimmed = current_recs.strip().replace("\n", " ")
        if len(trimmed) > 1200:
            trimmed = trimmed[:1200] + "..."
        context_lines.append(f"  {trimmed}")

    context_lines.append("- Latest recommendation updates since previous refresh:")
    if improvement_items:
        for item in improvement_items[:max_delta_items]:
            context_lines.append(f"  {item}")
    else:
        context_lines.append(
            "  - No explicit delta detected (recommendations likely unchanged or reformatted)."
        )

    return context_lines