chore: export repeated methods into lib

lib/features.py

@@ -0,0 +1,125 @@
+"""Unified featurization utilities for trajectory -> feature vector conversion
+Used by both experiments/ml/ and sim/rl/ components
+"""
+import numpy as np
+from collections import defaultdict
+from typing import List, Dict, Callable, Optional, Any, Set
+from datetime import datetime
+
+
+def transition_histogram(events: List, state_fn: Callable, max_states: int = 50) -> np.ndarray:
+    """compute normalized histogram of state transitions in trajectory
+    events: list of event objects/dicts
+    state_fn: function mapping event -> state string
+    max_states: maximum dimensions for histogram
+    """
+    if len(events) < 2:
+        return np.zeros(max_states, dtype=np.float32)
+    states = [state_fn(e) for e in events]
+    trans_counts = defaultdict(int)
+    for s, s_next in zip(states, states[1:]):
+        trans_counts[(s, s_next)] += 1
+    total = sum(trans_counts.values())
+    hist = np.array(list(trans_counts.values())[:max_states], dtype=np.float32)
+    hist = np.pad(hist, (0, max(0, max_states - len(hist))))
+    return hist / (total + 1e-10)
+
+
+def temporal_signature(events: List, ts_fn: Callable) -> np.ndarray:
+    """extract temporal features: mean/std/skew of inter-event times plus count
+    events: list of event objects/dicts
+    ts_fn: function mapping event -> timestamp (float seconds)
+    returns: [mean_dt, std_dt, skew, n_intervals] array
+    """
+    if len(events) < 2:
+        return np.zeros(4, dtype=np.float32)
+    times = sorted([ts_fn(e) for e in events])
+    diffs = np.diff(times).astype(np.float32)
+    if len(diffs) == 0:
+        return np.zeros(4, dtype=np.float32)
+    mean_dt, std_dt = np.mean(diffs), np.std(diffs) + 1e-10
+    skew = np.mean(((diffs - mean_dt) / std_dt) ** 3) if std_dt > 1e-8 else 0.0
+    return np.array([mean_dt, std_dt, skew, len(diffs)], dtype=np.float32)
+
+
+def state_coverage(events: List, state_fn: Callable, mdp_states: Set[str]) -> float:
+    """fraction of MDP states visited by trajectory
+    events: list of event objects/dicts
+    state_fn: function mapping event -> state string
+    mdp_states: set of all possible MDP states
+    """
+    if not mdp_states:
+        return 0.0
+    visited = set(state_fn(e) for e in events)
+    return len(visited & mdp_states) / len(mdp_states)
+
+
+def transition_entropy(events: List, state_fn: Callable) -> float:
+    """compute entropy of transition distribution (randomness of navigation)
+    higher entropy = more random browsing pattern
+    """
+    if len(events) < 2:
+        return 0.0
+    states = [state_fn(e) for e in events]
+    trans_counts = defaultdict(int)
+    for s, s_next in zip(states, states[1:]):
+        trans_counts[(s, s_next)] += 1
+    total = sum(trans_counts.values())
+    probs = [c / total for c in trans_counts.values()]
+    return -sum(p * np.log(p + 1e-10) for p in probs)
+
+
+def event_type_distribution(events: List, event_name_fn: Callable) -> np.ndarray:
+    """compute proportions of different event type categories
+    returns: [page_view_ratio, hover_ratio, cart_ratio, purchase_ratio]
+    """
+    if not events:
+        return np.zeros(4, dtype=np.float32)
+    n = len(events)
+    names = [event_name_fn(e).lower() for e in events]
+    return np.array([
+        sum(1 for nm in names if 'page' in nm or 'view' in nm) / n,
+        sum(1 for nm in names if 'hover' in nm) / n,
+        sum(1 for nm in names if 'cart' in nm) / n,
+        sum(1 for nm in names if 'purchase' in nm or 'checkout' in nm) / n
+    ], dtype=np.float32)
+
+
+def featurize_trajectory(events: List, state_fn: Callable, ts_fn: Callable,
+                         event_name_fn: Callable, mdp_states: Optional[Set[str]] = None,
+                         output_dim: int = 64) -> np.ndarray:
+    """convert trajectory to fixed-dimension feature vector
+    events: list of event objects/dicts
+    state_fn: function mapping event -> state string
+    ts_fn: function mapping event -> timestamp (float)
+    event_name_fn: function mapping event -> event name string
+    mdp_states: optional set of all MDP states for coverage calculation
+    output_dim: desired output dimension (will pad/truncate)
+    """
+    feats = []
+    feats.extend(transition_histogram(events, state_fn, max_states=40))  # 40 dims
+    feats.extend(temporal_signature(events, ts_fn))  # 4 dims
+    feats.append(state_coverage(events, state_fn, mdp_states or set()))  # 1 dim
+    feats.append(transition_entropy(events, state_fn))  # 1 dim
+    feats.append(float(len(events)))  # trajectory length
+    feats.append(float(len(set(state_fn(e) for e in events))))  # unique states
+    feats.extend(event_type_distribution(events, event_name_fn))  # 4 dims
+
+    feats = np.array(feats[:output_dim], dtype=np.float32)
+    if len(feats) < output_dim:
+        feats = np.pad(feats, (0, output_dim - len(feats)))
+    return feats
+
+
+def parse_timestamp(ts: Any) -> float:
+    """parse various timestamp formats to float seconds"""
+    if ts is None:
+        return 0.0
+    if isinstance(ts, (int, float)):
+        return float(ts)
+    if isinstance(ts, str):
+        try:
+            return datetime.fromisoformat(ts.replace('Z', '+00:00')).timestamp()
+        except ValueError:
+            return 0.0
+    return 0.0