compact_sets/src/graph.py

#!/usr/bin/env python
"""
PathFinder - finds paths through voice leading graphs.
"""

from __future__ import annotations
from dataclasses import dataclass
import networkx as nx
from random import choices, seed
from typing import Iterator

from .path import Path


@dataclass
class Candidate:
    """A candidate edge with raw factor scores."""

    edge: tuple
    edge_index: int
    graph_node: "Chord"
    scores: dict[str, float]
    weight: float = 0.0  # computed later by _compute_weights


class PathFinder:
    """Finds paths through voice leading graphs."""

    def __init__(self, graph: nx.MultiDiGraph):
        self.graph = graph

    def find_stochastic_path(
        self,
        start_chord: "Chord | None" = None,
        max_length: int = 100,
        weights_config: dict | None = None,
    ) -> Path:
        """Find a stochastic path through the graph.

        Returns:
            Path object containing output chords, graph chords, and metadata
        """
        if weights_config is None:
            weights_config = self._default_weights_config()

        chord = self._initialize_chords(start_chord)
        if not chord or chord[0] is None or len(self.graph.nodes()) == 0:
            return Path(chord[0] if chord else None, weights_config)

        original_chord = chord[0]

        path_obj = Path(original_chord, weights_config)
        path_obj.init_state(
            set(self.graph.nodes()), len(original_chord.pitches), original_chord
        )

        graph_node = original_chord

        for _ in range(max_length):
            out_edges = list(self.graph.out_edges(graph_node, data=True))

            if not out_edges:
                break

            # Build candidates with raw scores
            candidates = self._build_candidates(
                out_edges,
                path_obj.output_chords,
                weights_config,
                tuple(path_obj._voice_stay_count),
                path_obj.graph_chords,
                path_obj._cumulative_trans,
                path_obj._node_visit_counts,
            )

            # Compute weights from raw scores
            self._compute_weights(candidates, weights_config)

            # Filter out candidates with zero weight
            valid_candidates = [c for c in candidates if c.weight > 0]
            if not valid_candidates:
                break

            # Select using weighted choice
            chosen = choices(
                valid_candidates, weights=[c.weight for c in valid_candidates]
            )[0]

            # Use path.step() to handle all voice-leading and state updates
            path_obj.step(
                graph_node=chosen.graph_node,
                edge_data=chosen.edge[2],
                candidates=candidates,
                chosen_scores=chosen.scores,
            )

            graph_node = chosen.graph_node

        return path_obj

    def _build_candidates(
        self,
        out_edges: list,
        path: list["Chord"],
        config: dict,
        voice_stay_count: tuple[int, ...] | None,
        graph_path: list["Chord"] | None,
        cumulative_trans: "Pitch | None",
        node_visit_counts: dict | None,
    ) -> list["Candidate"]:
        """Build candidates with raw factor scores only."""
        if not out_edges:
            return []

        candidates = []
        for i, edge in enumerate(out_edges):
            edge_data = edge[2]

            # All factors - always compute verbatim
            direct_tuning = self._factor_direct_tuning(edge_data, config)
            voice_crossing = self._factor_voice_crossing(edge_data, config)
            melodic = self._factor_melodic_threshold(edge_data, config)
            contrary = self._factor_contrary_motion(edge_data, config)
            hamiltonian = self._factor_dca_hamiltonian(edge, node_visit_counts, config)
            dca_voice = self._factor_dca_voice_movement(
                edge, path, voice_stay_count, config, cumulative_trans
            )
            target = self._factor_target_range(edge, path, config, cumulative_trans)

            scores = {
                "direct_tuning": direct_tuning,
                "voice_crossing": voice_crossing,
                "melodic_threshold": melodic,
                "contrary_motion": contrary,
                "dca_hamiltonian": hamiltonian,
                "dca_voice_movement": dca_voice,
                "target_range": target,
            }

            candidates.append(Candidate(edge, i, edge[1], scores, 0.0))

        return candidates

    def _compute_weights(
        self,
        candidates: list["Candidate"],
        config: dict,
    ) -> list[float]:
        """Compute weights from raw scores for all candidates.

        Returns a list of weights, and updates each candidate's weight field.
        """
        if not candidates:
            return []

        # Collect raw values for normalization
        melodic_values = [c.scores.get("melodic_threshold", 0) for c in candidates]
        contrary_values = [c.scores.get("contrary_motion", 0) for c in candidates]
        hamiltonian_values = [c.scores.get("dca_hamiltonian", 0) for c in candidates]
        dca_values = [c.scores.get("dca_voice_movement", 0) for c in candidates]
        target_values = [c.scores.get("target_range", 0) for c in candidates]

        # Helper function for sum normalization
        def sum_normalize(values: list) -> list | None:
            """Normalize values to sum to 1. Returns None if no discrimination."""
            total = sum(values)
            if total == 0 or len(set(values)) <= 1:
                return None
            return [v / total for v in values]

        # Sum normalize each factor
        melodic_norm = sum_normalize(melodic_values)
        contrary_norm = sum_normalize(contrary_values)
        hamiltonian_norm = sum_normalize(hamiltonian_values)
        dca_norm = sum_normalize(dca_values)
        target_norm = sum_normalize(target_values)

        # Calculate weights for each candidate
        weights = []
        for i, candidate in enumerate(candidates):
            scores = candidate.scores
            w = 1.0

            # Hard factors (multiplicative - eliminates if 0)
            w *= scores.get("direct_tuning", 0)
            if w == 0:
                candidate.weight = 0.0
                weights.append(0.0)
                continue

            w *= scores.get("voice_crossing", 0)
            if w == 0:
                candidate.weight = 0.0
                weights.append(0.0)
                continue

            # Soft factors (sum normalized, then weighted)
            if melodic_norm:
                w += melodic_norm[i] * config.get("weight_melodic", 1)
            if contrary_norm:
                w += contrary_norm[i] * config.get("weight_contrary_motion", 0)
            if hamiltonian_norm:
                w += hamiltonian_norm[i] * config.get("weight_dca_hamiltonian", 1)
            if dca_norm:
                w += dca_norm[i] * config.get("weight_dca_voice_movement", 1)
            if target_norm:
                w += target_norm[i] * config.get("weight_target_range", 1)

            candidate.weight = w
            weights.append(w)

        return weights

    def _initialize_chords(self, start_chord: "Chord | None") -> tuple:
        """Initialize chord sequence."""
        if start_chord is not None:
            return (start_chord,)

        nodes = list(self.graph.nodes())
        if nodes:
            import random

            random.shuffle(nodes)

            weights_config = self._default_weights_config()
            weights_config["voice_crossing_allowed"] = False

            for chord in nodes[:50]:
                out_edges = list(self.graph.out_edges(chord, data=True))
                if len(out_edges) == 0:
                    continue

                candidates = self._build_candidates(
                    out_edges, [chord], weights_config, None, None, None, None
                )
                nonzero = sum(1 for c in candidates if c.weight > 0)

                if nonzero > 0:
                    return (chord,)

            return (nodes[0],)

        return (None,)

    def _default_weights_config(self) -> dict:
        """Default weights configuration."""
        return {
            "contrary_motion": True,
            "direct_tuning": True,
            "voice_crossing_allowed": False,
            "melodic_threshold_min": 0,
            "melodic_threshold_max": 500,
            "hamiltonian": True,
            "dca": 2.0,
            "target_range": False,
            "target_range_octaves": 2.0,
        }

    def _factor_melodic_threshold(self, edge_data: dict, config: dict) -> float:
        """Returns 1.0 if all voice movements are within melodic threshold, 0.0 otherwise."""
        # Check weight - if 0, return 1.0 (neutral)
        if config.get("weight_melodic", 1) == 0:
            return 1.0

        melodic_min = config.get("melodic_threshold_min", 0)
        melodic_max = config.get("melodic_threshold_max", float("inf"))

        cent_diffs = edge_data.get("cent_diffs", [])

        if melodic_min is not None or melodic_max is not None:
            for cents in cent_diffs:
                if melodic_min is not None and cents < melodic_min:
                    return 0.0
                if melodic_max is not None and cents > melodic_max:
                    return 0.0
        return 1.0

    def _factor_direct_tuning(self, edge_data: dict, config: dict) -> float:
        """Returns 1.0 if directly tunable (or disabled), 0.0 otherwise."""
        # Check weight - if 0, return 1.0 (neutral)
        if config.get("weight_direct_tuning", 1) == 0:
            return 1.0

        if config.get("direct_tuning", True):
            if edge_data.get("is_directly_tunable", False):
                return 1.0
            return 0.0
        return 1.0  # not configured, neutral

    def _factor_voice_crossing(self, edge_data: dict, config: dict) -> float:
        """Returns 1.0 if no voice crossing (or allowed), 0.0 if crossing and not allowed."""
        if config.get("voice_crossing_allowed", False):
            return 1.0

        if edge_data.get("voice_crossing", False):
            return 0.0
        return 1.0

    def _factor_contrary_motion(self, edge_data: dict, config: dict) -> float:
        """Returns factor based on contrary motion.

        Contrary motion: half of moving voices go one direction, half go opposite.
        Weighted by closeness to ideal half split.
        factor = 1.0 - (distance_from_half / half)
        """
        if config.get("weight_contrary_motion", 0) == 0:
            return 1.0

        cent_diffs = edge_data.get("cent_diffs", [])

        num_up = sum(1 for d in cent_diffs if d > 0)
        num_down = sum(1 for d in cent_diffs if d < 0)
        num_moving = num_up + num_down

        if num_moving < 2:
            return 0.0  # Need at least 2 moving voices for contrary motion

        ideal_up = num_moving / 2
        distance = abs(num_up - ideal_up)
        return max(0.0, 1.0 - (distance / ideal_up))

    def _factor_dca_hamiltonian(
        self, edge: tuple, node_visit_counts: dict | None, config: dict
    ) -> float:
        """Returns probability based on how long since node was last visited.

        DCA Hamiltonian: longer since visited = higher probability.
        Similar to DCA voice movement but for graph nodes.
        """
        if config.get("weight_dca_hamiltonian", 1) == 0:
            return 1.0

        if node_visit_counts is None:
            return 1.0

        destination = edge[1]
        if destination not in node_visit_counts:
            return 1.0

        visit_count = node_visit_counts[destination]
        max_count = max(node_visit_counts.values()) if node_visit_counts else 0

        if max_count == 0:
            return 1.0

        # Normalize by max squared - gives stronger discrimination
        return visit_count / (max_count**2)

    def _factor_dca_voice_movement(
        self,
        edge: tuple,
        path: list,
        voice_stay_count: tuple[int, ...] | None,
        config: dict,
        cumulative_trans: "Pitch | None",
    ) -> float:
        """Returns probability that voices will change.

        DCA = Dissonant Counterpoint Algorithm
        Probability = (sum of stay_counts for changing voices) / (sum of ALL stay_counts)

        Higher probability = more likely to choose edge where long-staying voices change.
        """
        if config.get("weight_dca_voice_movement", 1) == 0:
            return 1.0

        if voice_stay_count is None or len(path) == 0:
            return 1.0

        if cumulative_trans is None:
            return 1.0

        num_voices = len(voice_stay_count)
        if num_voices == 0:
            return 1.0

        current_chord = path[-1]
        edge_data = edge[2]
        next_graph_node = edge[1]
        trans = edge_data.get("transposition")
        if trans is not None:
            candidate_transposed = next_graph_node.transpose(
                cumulative_trans.transpose(trans)
            )
        else:
            candidate_transposed = next_graph_node.transpose(cumulative_trans)

        current_cents = [p.to_cents() for p in current_chord.pitches]
        candidate_cents = [p.to_cents() for p in candidate_transposed.pitches]

        sum_changing = 0
        sum_all = sum(voice_stay_count)

        if sum_all == 0:
            return 1.0

        for voice_idx in range(num_voices):
            if current_cents[voice_idx] != candidate_cents[voice_idx]:
                sum_changing += voice_stay_count[voice_idx]

        return sum_changing / sum_all

    def _factor_target_range(
        self,
        edge: tuple,
        path: list,
        config: dict,
        cumulative_trans: "Pitch | None",
    ) -> float:
        """Returns factor based on movement toward target.

        Target progresses based on position in path.
        Uses average cents of current chord for accurate targeting.
        Factor > 1.0 if moving toward target, < 1.0 if moving away.
        """
        if config.get("weight_target_range", 1) == 0:
            return 1.0

        if not config.get("target_range", False):
            return 1.0

        if len(path) == 0 or cumulative_trans is None:
            return 1.0

        target_octaves = config.get("target_range_octaves", 2.0)
        max_path = config.get("max_path", 50)
        target_cents = target_octaves * 1200

        start_avg_cents = sum(p.to_cents() for p in path[0].pitches) / len(
            path[0].pitches
        )
        progress = len(path) / max_path
        current_target = start_avg_cents + (progress * target_cents)

        current_chord = path[-1]
        current_avg_cents = sum(p.to_cents() for p in current_chord.pitches) / len(
            current_chord.pitches
        )

        edge_data = edge[2]
        next_graph_node = edge[1]
        edge_trans = edge_data.get("transposition")
        if edge_trans is not None:
            candidate_transposed = next_graph_node.transpose(
                cumulative_trans.transpose(edge_trans)
            )
        else:
            candidate_transposed = next_graph_node.transpose(cumulative_trans)
        candidate_avg_cents = sum(
            p.to_cents() for p in candidate_transposed.pitches
        ) / len(candidate_transposed.pitches)

        if current_target <= 0:
            return 1.0

        dist_before = abs(current_avg_cents - current_target)
        dist_after = abs(candidate_avg_cents - current_target)

        if dist_before == 0:
            return 1.0

        if dist_after < dist_before:
            return 1.0 + (dist_before - dist_after) / dist_before
        elif dist_after > dist_before:
            return max(0.1, 1.0 - (dist_after - dist_before) / dist_before)
        else:
            return 1.0

    def is_hamiltonian(self, path: list["Chord"]) -> bool:
        """Check if a path is Hamiltonian (visits all nodes exactly once)."""
        return len(path) == len(self.graph.nodes()) and len(set(path)) == len(path)