"""Shared helpers for the example solvers: load the challenge, write wavs, write submission JSON."""
from __future__ import annotations

import json
import platform
from pathlib import Path

import numpy as np
from scipy.io import wavfile


def load_challenge(path: Path) -> dict:
    with open(path) as f:
        return json.load(f)


def write_wav(path: Path, samples_si: np.ndarray, challenge: dict) -> None:
    """Write pointwise samples of the SI signal, divided by signal_scale, as float32."""
    out = challenge["output"]
    scaled = np.asarray(samples_si, dtype=np.float64) / float(out["signal_scale"])
    path.parent.mkdir(parents=True, exist_ok=True)
    wavfile.write(path, int(out["sample_rate_hz"]), scaled.astype(np.float32))


def hardware_string() -> str:
    cpu = platform.processor() or platform.machine()
    try:
        with open("/proc/cpuinfo") as f:
            for line in f:
                if line.startswith("model name"):
                    cpu = line.split(":", 1)[1].strip()
                    break
    except OSError:
        pass
    return f"{cpu}, single thread, Python {platform.python_version()} + numpy {np.__version__}"


def pluck_load_q(p: dict) -> float:
    """Total load Q (a slope, force over tension) giving pluck height h at x_p."""
    return p["h"] / (p["x_p"] * (p["L"] - p["x_p"]) / p["L"] - p["w"] * (0.25 - 1.0 / np.pi**2))


def initial_shape(x: np.ndarray, p: dict) -> np.ndarray:
    """u_0(x): static equilibrium under the raised-cosine finger load, from the challenge spec."""
    L, xp, w = p["L"], p["x_p"], p["w"]
    Q = pluck_load_q(p)
    tri = np.where(x <= xp, x * (L - xp) / L, xp * (L - x) / L)
    y = x - xp
    cap = np.zeros_like(x)
    m = np.abs(y) <= w
    ym = y[m]
    cap[m] = ym * (ym > 0) - (1.0 / (2.0 * w)) * ((ym + w) ** 2 / 2.0 - (w**2 / np.pi**2) * (1.0 + np.cos(np.pi * ym / w)))
    return Q * (tri + cap)