# -*- coding: utf-8 -*-
"""
collatz_compute_survival_rate.py

Compute survival rate (coefficient of contraction) for a noyau.
Outputs |B_m| and q = |B_m| / (2 * |R_{m-1}|) when previous noyau is available.

Usage: python collatz_compute_survival_rate.py --noyau PATH [--previous PATH]
"""

from __future__ import annotations
import argparse
import json
from pathlib import Path


def load_noyau(path: str) -> tuple[list[int], int]:
    """Load noyau from JSON, return (residues, palier)."""
    data = json.loads(Path(path).read_text(encoding="utf-8"))
    if isinstance(data, list):
        residues = [int(x) for x in data]
        palier = max(n.bit_length() for n in residues) if residues else 0
        return residues, palier
    if isinstance(data, dict):
        for key in ("noyau", "residues", "uncovered"):
            if key in data and isinstance(data[key], list):
                residues = [int(x) for x in data[key]]
                palier = data.get("palier", max(n.bit_length() for n in residues) if residues else 0)
                return residues, palier
    raise ValueError(f"Cannot load noyau from {path}")


def main() -> None:
    ap = argparse.ArgumentParser(description="Compute survival rate of noyau")
    ap.add_argument("--noyau", required=True, help="Path to noyau JSON")
    ap.add_argument("--previous", help="Path to previous noyau (for q = |B_m| / 2|R_{m-1}|)")
    args = ap.parse_args()

    residues, palier = load_noyau(args.noyau)
    size = len(residues)

    lines = [
        f"# Survival rate: {Path(args.noyau).name}",
        "",
        f"- |B_{{m}}| = {size}",
        f"- palier m ≈ {palier}",
        "",
    ]

    if args.previous and Path(args.previous).exists():
        prev_residues, prev_palier = load_noyau(args.previous)
        prev_size = len(prev_residues)
        denom = 2 * prev_size
        q = size / denom if denom else 0
        lines.extend([
            f"- |R_{{m-1}}| = {prev_size}",
            f"- q = |B_m| / (2|R_{{m-1}}|) = {q:.6f}",
            "",
        ])

    print("\n".join(lines))


if __name__ == "__main__":
    main()