"""Auto-tune parametri PM2D da analisi del template.

Analizza la ROI del modello e suggerisce valori ragionevoli per i principali
parametri del `LineShapeMatcher`, tenendo conto di:

- **distribuzione magnitude del gradiente** → soglie `weak_grad` / `strong_grad`
- **numero di edge utili** → `num_features`
- **dimensione template** → `pyramid_levels`, `spread_radius`
- **simmetria rotazionale** (autocorrelazione su rotazione) → `angle_range_deg`
- **entropia orientamenti** → suggerimento `min_score`

Ritorna dict con i key esatti del form `edit_params`.
"""

from __future__ import annotations

import cv2
import numpy as np


def _to_gray(img: np.ndarray) -> np.ndarray:
    if img.ndim == 3:
        return cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
    return img


def detect_rotational_symmetry(
    gray: np.ndarray, step_deg: float = 5.0, corr_thresh: float = 0.75,
) -> dict:
    """Rileva simmetria rotazionale su edge map (più robusto a sfondo uniforme).

    Ritorna dict con:
      - order: int, 1=nessuna, 2=180°, 3=120°, 4=90°, 6=60°, 8=45°
      - period_deg: float, periodo minimo di simmetria (360/order)
      - confidence: float [0..1], correlazione minima tra rotazioni equivalenti
    """
    h, w = gray.shape
    # Usa magnitude gradiente (rotation-invariant rispetto a bg uniforme)
    gx = cv2.Sobel(gray, cv2.CV_32F, 1, 0, ksize=3)
    gy = cv2.Sobel(gray, cv2.CV_32F, 0, 1, ksize=3)
    mag = cv2.magnitude(gx, gy).astype(np.float32)

    center = (w / 2.0, h / 2.0)
    ref = mag

    correlations: list[tuple[float, float]] = []
    for ang in np.arange(step_deg, 360.0, step_deg):
        M = cv2.getRotationMatrix2D(center, float(ang), 1.0)
        rot = cv2.warpAffine(
            mag, M, (w, h), borderValue=0.0,
        )
        rm = ref - ref.mean()
        rs = rot - rot.mean()
        denom = np.sqrt((rm * rm).sum() * (rs * rs).sum()) + 1e-9
        c = float((rm * rs).sum() / denom)
        correlations.append((float(ang), c))

    # Candidati simmetria: 2,3,4,6,8 (90/45)
    candidates = [2, 3, 4, 6, 8]
    best_order = 1
    best_conf = 0.0
    for order in candidates:
        period = 360.0 / order
        # Verifica che ALLE rotazioni n*period (n=1..order-1) ci sia alta corr
        corrs = []
        for n in range(1, order):
            target = period * n
            # trova angolo più vicino in correlations
            closest = min(correlations, key=lambda p: abs(p[0] - target))
            if abs(closest[0] - target) > step_deg * 1.5:
                corrs.append(0.0)
            else:
                corrs.append(closest[1])
        conf = min(corrs) if corrs else 0.0
        if conf >= corr_thresh and conf > best_conf:
            best_order = order
            best_conf = conf
    return {
        "order": best_order,
        "period_deg": 360.0 / best_order,
        "confidence": best_conf,
    }


def analyze_gradients(gray: np.ndarray) -> dict:
    """Statistiche magnitude / orientation gradiente."""
    gx = cv2.Sobel(gray, cv2.CV_32F, 1, 0, ksize=3)
    gy = cv2.Sobel(gray, cv2.CV_32F, 0, 1, ksize=3)
    mag = cv2.magnitude(gx, gy)

    # Percentili magnitude
    p50 = float(np.percentile(mag, 50))
    p80 = float(np.percentile(mag, 80))
    p95 = float(np.percentile(mag, 95))
    mag_max = float(mag.max())

    # Numero pixel "forti"
    strong_pct = float((mag > p95).sum()) / mag.size
    weak_pct = float((mag > p50).sum()) / mag.size

    # Entropia orientamenti (solo pixel forti)
    ang = np.arctan2(gy, gx)
    ang_mod = np.where(ang < 0, ang + np.pi, ang)
    mask = mag > p80
    if mask.sum() > 10:
        bins_count, _ = np.histogram(
            ang_mod[mask], bins=16, range=(0, np.pi),
        )
        p = bins_count / (bins_count.sum() + 1e-9)
        ent = float(-np.sum(p * np.log(p + 1e-9)) / np.log(16))
    else:
        ent = 0.0

    return {
        "p50": p50, "p80": p80, "p95": p95, "mag_max": mag_max,
        "strong_pct": strong_pct, "weak_pct": weak_pct,
        "orient_entropy": ent,
        "n_pixels": mag.size,
        "n_strong": int((mag > p95).sum()),
    }


def auto_tune(template_bgr: np.ndarray, mask: np.ndarray | None = None) -> dict:
    """Analizza template e ritorna dict parametri suggeriti.

    Chiavi compatibili con edit_params PARAM_SCHEMA.
    """
    gray = _to_gray(template_bgr)
    h, w = gray.shape
    if mask is not None:
        # Zero fuori maschera per statistiche
        gray_for_stats = np.where(mask > 0, gray, int(np.median(gray))).astype(np.uint8)
    else:
        gray_for_stats = gray

    stats = analyze_gradients(gray_for_stats)
    sym = detect_rotational_symmetry(gray_for_stats)

    # Soglie magnitude: usa percentili per robustezza illuminazione.
    # Target: strong_grad ~= valore a percentile 80-90 in assoluto, ma
    # clamp per compatibilità uint8 (Sobel può sforare).
    strong_grad = float(np.clip(stats["p80"], 20.0, 100.0))
    weak_grad = float(np.clip(strong_grad * 0.5, 10.0, 60.0))

    # num_features: 1 feature ogni ~25 px forti, clamp 48..192
    target_feat = int(np.clip(stats["n_strong"] / 25, 48, 192))

    # pyramid_levels in base alla dimensione minima
    min_side = min(h, w)
    if min_side < 60:
        pyr = 1
    elif min_side < 120:
        pyr = 2
    elif min_side < 320:
        pyr = 3
    else:
        pyr = 4

    # spread_radius proporzionale a risoluzione + pyramid (tolleranza ~1% dim)
    spread_radius = int(np.clip(max(3, min_side * 0.02), 3, 8))

    # angle range ridotto se simmetria rotazionale
    angle_max = 360.0 / sym["order"] if sym["order"] > 1 else 360.0

    # min_score: se entropia orient alta → template distintivo → soglia alta ok
    # se entropia bassa → template ambiguo → soglia più permissiva
    if stats["orient_entropy"] > 0.75:
        min_score = 0.65
    elif stats["orient_entropy"] > 0.55:
        min_score = 0.55
    else:
        min_score = 0.45

    # angle step: 5° default; se simmetria, mantengo step ma range ridotto
    angle_step = 5.0

    return {
        "backend": "line",
        "angle_min": 0.0,
        "angle_max": angle_max,
        "angle_step": angle_step,
        "scale_min": 1.0,
        "scale_max": 1.0,
        "scale_step": 0.1,
        "min_score": round(min_score, 2),
        "max_matches": 25,
        "nms_radius": 0,
        "num_features": target_feat,
        "weak_grad": round(weak_grad, 1),
        "strong_grad": round(strong_grad, 1),
        "spread_radius": spread_radius,
        "pyramid_levels": pyr,
        "verify_threshold": 0.4,
        # meta (non in PARAM_SCHEMA, usato per log)
        "_symmetry_order": sym["order"],
        "_symmetry_conf": round(sym["confidence"], 2),
        "_orient_entropy": round(stats["orient_entropy"], 2),
    }


def summarize(tune: dict) -> str:
    """Stringa one-line delle scelte principali."""
    so = tune.get("_symmetry_order", 1)
    sc = tune.get("_symmetry_conf", 0)
    ent = tune.get("_orient_entropy", 0)
    return (
        f"sym={so}x (conf={sc:.2f})  entropia={ent:.2f}  "
        f"feat={tune['num_features']}  pyr={tune['pyramid_levels']}  "
        f"grad={tune['weak_grad']:.0f}/{tune['strong_grad']:.0f}  "
        f"ang=[0..{tune['angle_max']:.0f}]@{tune['angle_step']:.0f}d  "
        f"min_score={tune['min_score']}"
    )