src/metrics.py

"""Metrics computation for unlearning experiments."""
import numpy as np
from scipy import stats
from scipy.special import digamma, polygamma
from typing import Dict, List, Tuple, Optional
from collections import defaultdict

from src.graph_utils import build_adjacency, get_deletion_neighborhood, get_blocks_at_distance


# ============================================================
# Parameter distance / influence
# ============================================================

def compute_block_param_vector(params: dict, node_type: str, idx: int, model_family: str) -> np.ndarray:
    """Extract flat parameter vector for a single block."""
    if model_family == 'poisson_gamma':
        if node_type == 'user':
            return np.concatenate([params['a'][idx], params['b'][idx]])
        else:
            return np.concatenate([params['c'][idx], params['d'][idx]])
    elif model_family == 'gaussian_gaussian':
        if node_type == 'user':
            return np.concatenate([params['m_U'][idx], params['s_U'][idx]])
        else:
            return np.concatenate([params['m_V'][idx], params['s_V'][idx]])
    elif model_family == 'gaussian_gamma_map':
        if node_type == 'user':
            return params['alpha'][idx].copy()
        else:
            return params['beta'][idx].copy()
    else:
        raise ValueError(f"Unknown model family: {model_family}")


def compute_all_param_vector(params: dict, model_family: str) -> np.ndarray:
    """Flatten all parameters into a single vector."""
    if model_family == 'poisson_gamma':
        return np.concatenate([params['a'].ravel(), params['b'].ravel(), 
                               params['c'].ravel(), params['d'].ravel()])
    elif model_family == 'gaussian_gaussian':
        return np.concatenate([params['m_U'].ravel(), params['s_U'].ravel(),
                               params['m_V'].ravel(), params['s_V'].ravel()])
    elif model_family == 'gaussian_gamma_map':
        return np.concatenate([params['alpha'].ravel(), params['beta'].ravel()])
    else:
        raise ValueError(f"Unknown model family: {model_family}")


def compute_deletion_influence_by_distance(full_params, exact_params, edge_to_remove,
                                            edges, N, M, model_family, max_radius=6):
    """Compute deletion influence Delta_u(z) = ||lambda_u^* - lambda_u^{\\z}||
    grouped by graph distance from seed set."""
    user_to_items, item_to_users, _ = build_adjacency(edges, N, M)
    distances = get_deletion_neighborhood(edge_to_remove, user_to_items, item_to_users, 
                                           N, M, max_radius)
    blocks_by_dist = get_blocks_at_distance(distances, N)
    
    influence_by_dist = {}
    for dist, blocks in blocks_by_dist.items():
        influences = []
        for node_type, idx in blocks:
            v_full = compute_block_param_vector(full_params, node_type, idx, model_family)
            v_exact = compute_block_param_vector(exact_params, node_type, idx, model_family)
            delta = np.linalg.norm(v_full - v_exact)
            influences.append(delta)
        influence_by_dist[dist] = {
            'mean': float(np.mean(influences)),
            'std': float(np.std(influences)),
            'median': float(np.median(influences)),
            'max': float(np.max(influences)),
            'n_blocks': len(influences),
            'values': [float(v) for v in influences],
        }
    
    return influence_by_dist


def fit_exponential_decay(influence_by_dist: dict, min_shells: int = 3, eps: float = 1e-12):
    """Fit log(Delta(r)) = alpha - mu * r."""
    distances = sorted(influence_by_dist.keys())
    r_vals = []
    log_vals = []
    
    for r in distances:
        mean_inf = influence_by_dist[r]['mean']
        if mean_inf > eps and influence_by_dist[r]['n_blocks'] >= 2:
            r_vals.append(r)
            log_vals.append(np.log(mean_inf + eps))
    
    if len(r_vals) < min_shells:
        return {
            'mu_emp': None,
            'intercept': None,
            'r_squared': None,
            'n_shells': len(r_vals),
            'valid': False,
        }
    
    r_arr = np.array(r_vals, dtype=float)
    log_arr = np.array(log_vals)
    
    slope, intercept, r_value, p_value, std_err = stats.linregress(r_arr, log_arr)
    
    return {
        'mu_emp': float(-slope),
        'intercept': float(intercept),
        'r_squared': float(r_value ** 2),
        'n_shells': len(r_vals),
        'p_value': float(p_value),
        'std_err': float(std_err),
        'valid': True,
    }


# ============================================================
# Local approximation error
# ============================================================

def compute_local_error(local_params, exact_params, model_family):
    """Err_R(z) = ||lambda^(R)_local - lambda^{\\z}||"""
    v_local = compute_all_param_vector(local_params, model_family)
    v_exact = compute_all_param_vector(exact_params, model_family)
    
    err = np.linalg.norm(v_local - v_exact)
    rel_err = err / (1.0 + np.linalg.norm(v_exact))
    
    return {
        'param_error': float(err),
        'relative_error': float(rel_err),
    }


# ============================================================
# ELBO / objective gap
# ============================================================

def compute_objective_gap(model, edges_without, exact_params, approx_params):
    """Gap_R = L_{\\z}(lambda^{\\z}) - L_{\\z}(lambda^(R))."""
    try:
        obj_exact = model.compute_elbo(edges_without, exact_params) if hasattr(model, 'compute_elbo') \
            else model.compute_objective(edges_without, exact_params)
        obj_approx = model.compute_elbo(edges_without, approx_params) if hasattr(model, 'compute_elbo') \
            else model.compute_objective(edges_without, approx_params)
        return float(obj_exact - obj_approx)
    except Exception as e:
        return None


# ============================================================
# Weighted interaction statistics (chi)
# ============================================================

def compute_chi_poisson_gamma(edge_to_remove, edges, params, N, M, K,
                               a0=0.3, b0=1.0, c0=0.3, d0=1.0):
    """Compute chi statistics for Poisson-Gamma model."""
    a, b, c, d = params['a'], params['b'], params['c'], params['d']
    
    # Compute constants
    a_min = np.min(a[a > 0]) if np.any(a > 0) else a0
    b_min = np.min(b[b > 0]) if np.any(b > 0) else b0
    c_min = np.min(c[c > 0]) if np.any(c > 0) else c0
    d_min = np.min(d[d > 0]) if np.any(d > 0) else d0
    a_max = np.max(a)
    c_max = np.max(c)
    
    C_x = 0.5 * polygamma(1, max(c_min, 1e-3)) + 0.5 / max(d_min, 1e-6)
    C_0 = 1.0 / max(d_min, 1e-6) + c_max / max(d_min**2, 1e-12)
    
    C_tilde_x = 0.5 * polygamma(1, max(a_min, 1e-3)) + 0.5 / max(b_min, 1e-6)
    C_tilde_0 = 1.0 / max(b_min, 1e-6) + a_max / max(b_min**2, 1e-12)
    
    # Build adjacency
    user_to_items = defaultdict(list)
    item_to_users = defaultdict(list)
    edge_dict = {}
    for i, j, x in edges:
        user_to_items[i].append(j)
        item_to_users[j].append(i)
        edge_dict[(i, j)] = x
    
    i_del, j_del, x_del = edge_to_remove
    
    # chi_i
    chi_i = sum(C_x * edge_dict.get((i_del, j), 0) + C_0 for j in user_to_items.get(i_del, []))
    
    # chi_tilde_j
    chi_tilde_j = sum(C_tilde_x * edge_dict.get((i, j_del), 0) + C_tilde_0 
                      for i in item_to_users.get(j_del, []))
    
    chi_max = max(chi_i, chi_tilde_j)
    chi_sum = chi_i + chi_tilde_j
    
    # Empirical alternatives
    seed_degree = len(user_to_items.get(i_del, [])) + len(item_to_users.get(j_del, []))
    seed_count_sum = sum(edge_dict.get((i_del, j), 0) for j in user_to_items.get(i_del, [])) + \
                     sum(edge_dict.get((i, j_del), 0) for i in item_to_users.get(j_del, []))
    
    return {
        'chi_i': float(chi_i),
        'chi_tilde_j': float(chi_tilde_j),
        'chi_max': float(chi_max),
        'chi_sum': float(chi_sum),
        'seed_degree': int(seed_degree),
        'seed_count_sum': float(seed_count_sum),
        'C_x': float(C_x),
        'C_0': float(C_0),
        'C_tilde_x': float(C_tilde_x),
        'C_tilde_0': float(C_tilde_0),
    }


def compute_chi_gaussian(edge_to_remove, edges, params, N, M, K, sigma_x,
                          model_family='gaussian_gaussian'):
    """Compute interaction proxy for Gaussian models."""
    user_to_items = defaultdict(list)
    item_to_users = defaultdict(list)
    edge_dict = {}
    for i, j, x in edges:
        user_to_items[i].append(j)
        item_to_users[j].append(i)
        edge_dict[(i, j)] = x
    
    i_del, j_del, x_del = edge_to_remove
    prec_x = 1.0 / (sigma_x ** 2)
    
    if model_family == 'gaussian_gaussian':
        m_U, s_U = params['m_U'], params['s_U']
        m_V, s_V = params['m_V'], params['s_V']
        
        chi_i = sum(prec_x * np.sum(m_V[j]**2 + s_V[j]) for j in user_to_items.get(i_del, []))
        chi_tilde_j = sum(prec_x * np.sum(m_U[i]**2 + s_U[i]) for i in item_to_users.get(j_del, []))
    elif model_family == 'gaussian_gamma_map':
        from src.model import GaussianGammaMAP
        sp = lambda x: np.log1p(np.exp(np.clip(x, -20, 20)))
        U = sp(params['alpha'])
        V = sp(params['beta'])
        
        chi_i = sum(prec_x * np.sum(V[j]**2) for j in user_to_items.get(i_del, []))
        chi_tilde_j = sum(prec_x * np.sum(U[i]**2) for i in item_to_users.get(j_del, []))
    
    chi_max = max(chi_i, chi_tilde_j)
    chi_sum = chi_i + chi_tilde_j
    
    seed_degree = len(user_to_items.get(i_del, [])) + len(item_to_users.get(j_del, []))
    
    return {
        'chi_i': float(chi_i),
        'chi_tilde_j': float(chi_tilde_j),
        'chi_max': float(chi_max),
        'chi_sum': float(chi_sum),
        'seed_degree': int(seed_degree),
    }


# ============================================================
# Gradient interference proxy
# ============================================================

def compute_gradient_interference(full_params, exact_params, local_params, model_family):
    """Compute gradient interference proxy.
    
    g_del = lambda^* - lambda^{\\z}
    g_ret = lambda^{\\z} - lambda^(R)_local
    I(z) = |sum_u <g_del_u, g_ret_u>|
    """
    v_full = compute_all_param_vector(full_params, model_family)
    v_exact = compute_all_param_vector(exact_params, model_family)
    v_local = compute_all_param_vector(local_params, model_family)
    
    g_del = v_full - v_exact
    g_ret = v_exact - v_local
    
    raw_interference = float(np.abs(np.dot(g_del, g_ret)))
    
    norm_del = np.linalg.norm(g_del)
    norm_ret = np.linalg.norm(g_ret)
    eps = 1e-12
    cosine_interference = raw_interference / (norm_del * norm_ret + eps)
    
    return {
        'interference_raw': float(raw_interference),
        'interference_cosine': float(cosine_interference),
        'g_del_norm': float(norm_del),
        'g_ret_norm': float(norm_ret),
    }


# ============================================================
# Full metrics for one deletion
# ============================================================

def compute_all_metrics(full_params, exact_params, local_params_by_radius,
                        warm_start_params, one_step_params,
                        edge_to_remove, edges, N, M, K,
                        model_family, model=None, radii=[1, 2, 3, 4],
                        model_kwargs=None):
    """Compute all metrics for one deletion."""
    results = {}
    
    # Influence by distance
    influence = compute_deletion_influence_by_distance(
        full_params, exact_params, edge_to_remove, edges, N, M, model_family, 
        max_radius=max(radii) + 2)
    results['influence_by_distance'] = {str(k): v['mean'] for k, v in influence.items()}
    results['influence_by_distance_full'] = influence
    
    # Decay fit
    decay = fit_exponential_decay(influence)
    results['empirical_decay_mu'] = decay['mu_emp']
    results['empirical_decay_r2'] = decay['r_squared']
    results['decay_valid'] = decay['valid']
    
    # Chi statistics
    if model_kwargs is None:
        model_kwargs = {}
    
    if model_family == 'poisson_gamma':
        chi = compute_chi_poisson_gamma(
            edge_to_remove, edges, full_params, N, M, K,
            a0=model_kwargs.get('a0', 0.3), b0=model_kwargs.get('b0', 1.0),
            c0=model_kwargs.get('c0', 0.3), d0=model_kwargs.get('d0', 1.0))
    else:
        chi = compute_chi_gaussian(
            edge_to_remove, edges, full_params, N, M, K,
            sigma_x=model_kwargs.get('sigma_x', 1.0), model_family=model_family)
    
    results['chi_seed_max'] = chi['chi_max']
    results['chi_seed_sum'] = chi['chi_sum']
    results['seed_degree'] = chi['seed_degree']
    
    # Local errors by radius
    for R in radii:
        if R in local_params_by_radius:
            err = compute_local_error(local_params_by_radius[R], exact_params, model_family)
            results[f'error_R{R}'] = err['param_error']
            results[f'rel_error_R{R}'] = err['relative_error']
            
            # Interference
            interf = compute_gradient_interference(
                full_params, exact_params, local_params_by_radius[R], model_family)
            results[f'interference_raw_R{R}'] = interf['interference_raw']
            results[f'interference_cosine_R{R}'] = interf['interference_cosine']
    
    # Warm start error
    if warm_start_params is not None:
        ws_err = compute_local_error(warm_start_params, exact_params, model_family)
        results['error_warm_start'] = ws_err['param_error']
        results['rel_error_warm_start'] = ws_err['relative_error']
    
    # One-step error
    if one_step_params is not None:
        os_err = compute_local_error(one_step_params, exact_params, model_family)
        results['error_one_step'] = os_err['param_error']
        results['rel_error_one_step'] = os_err['relative_error']
    
    return results


# ============================================================
# Bootstrap confidence intervals
# ============================================================

def bootstrap_ci(values, n_boot=1000, ci=0.95, seed=42):
    """Compute bootstrap CI for mean."""
    rng = np.random.RandomState(seed)
    values = np.array(values)
    values = values[np.isfinite(values)]
    if len(values) < 3:
        return {'mean': float(np.mean(values)) if len(values) > 0 else 0,
                'ci_low': float(np.nan), 'ci_high': float(np.nan),
                'se': float(np.nan), 'n': len(values)}
    
    boot_means = np.array([
        np.mean(rng.choice(values, len(values), replace=True))
        for _ in range(n_boot)
    ])
    
    alpha = (1 - ci) / 2
    ci_low = float(np.percentile(boot_means, 100 * alpha))
    ci_high = float(np.percentile(boot_means, 100 * (1 - alpha)))
    
    return {
        'mean': float(np.mean(values)),
        'ci_low': ci_low,
        'ci_high': ci_high,
        'se': float(np.std(boot_means)),
        'n': len(values),
    }


def compute_bootstrap_summary(df, group_cols, metric_cols, n_boot=1000):
    """Compute bootstrap CIs for all metrics grouped by specified columns."""
    import pandas as pd
    rows = []
    
    available_groups = [c for c in group_cols if c in df.columns]
    if not available_groups:
        groups = [('all', df)]
    else:
        groups = df.groupby(available_groups)
    
    for grp_name, grp_df in groups:
        row = {}
        if isinstance(grp_name, tuple):
            for col, val in zip(available_groups, grp_name):
                row[col] = val
        elif available_groups:
            row[available_groups[0]] = grp_name
        
        for col in metric_cols:
            if col in grp_df.columns:
                vals = grp_df[col].dropna().values
                ci = bootstrap_ci(vals, n_boot=n_boot)
                row[f'{col}_mean'] = ci['mean']
                row[f'{col}_ci_low'] = ci['ci_low']
                row[f'{col}_ci_high'] = ci['ci_high']
                row[f'{col}_se'] = ci['se']
                row[f'{col}_n'] = ci['n']
        
        rows.append(row)
    
    return pd.DataFrame(rows)