compact_sets/src/path.py

#!/usr/bin/env python
"""
Path and PathStep classes for storing path state from PathFinder.
"""

from __future__ import annotations
from dataclasses import dataclass, field
from typing import TYPE_CHECKING, Any

from .pitch import Pitch
from .chord import Chord

if TYPE_CHECKING:
    from .graph import Candidate


@dataclass
class PathStep:
    """Stores data for a single step in the path."""

    graph_node: Chord
    output_chord: Chord
    transposition: Pitch | None = None
    movements: dict[int, int] = field(default_factory=dict)
    scores: dict[str, float] = field(default_factory=dict)
    candidates: list["Candidate"] = field(default_factory=list)
    node_visit_counts: dict | None = None
    voice_stay_count: tuple[int, ...] | None = None


class Path:
    """Stores the complete state of a generated path."""

    def __init__(
        self, initial_chord: Chord | None, weights_config: dict[str, Any] | None = None
    ):
        self.initial_chord = initial_chord
        self.steps: list[PathStep] = []
        self.weights_config = weights_config if weights_config is not None else {}

        # State for tracking
        self._node_visit_counts: dict = {}
        self._voice_stay_count: list[int] = []
        self._voice_map: list[int] = []  # which voice is at each position
        self._cumulative_trans: Pitch | None = None  # cumulative transposition

    def init_state(
        self, graph_nodes: set, num_voices: int, initial_chord: Chord
    ) -> None:
        """Initialize state after graph is known."""
        self._node_visit_counts = {node: 0 for node in graph_nodes}
        self._node_visit_counts[initial_chord] = 0
        self._voice_stay_count = [0] * num_voices
        self._voice_map = list(range(num_voices))  # voice i at position i

        dims = initial_chord.dims
        self._cumulative_trans = Pitch(tuple(0 for _ in range(len(dims))), dims)

    def step(
        self,
        graph_node: "Chord",
        edge_data: dict,
        candidates: list["Candidate"],
        chosen_scores: dict[str, float] | None = None,
    ) -> PathStep:
        """Process a step: update state, compute output, return step.

        Takes graph_node and edge_data, handles all voice-leading internally.
        """
        # Get edge information
        trans = edge_data.get("transposition")
        movement = edge_data.get("movements", {})

        # Update cumulative transposition
        if trans is not None:
            self._cumulative_trans = self._cumulative_trans.transpose(trans)

        # Transpose the graph node
        transposed = graph_node.transpose(self._cumulative_trans)

        # Update voice map based on movement
        new_voice_map = [None] * len(self._voice_map)
        for src_idx, dest_idx in movement.items():
            new_voice_map[dest_idx] = self._voice_map[src_idx]
        self._voice_map = new_voice_map

        # Reorder pitches according to voice map
        reordered_pitches = tuple(
            transposed.pitches[self._voice_map[i]] for i in range(len(self._voice_map))
        )
        output_chord = Chord(reordered_pitches, graph_node.dims)

        # Get previous output chord
        prev_output_chord = self.output_chords[-1]

        # Increment all node visit counts
        for node in self._node_visit_counts:
            self._node_visit_counts[node] += 1

        # Update voice stay counts (comparing same voice, not position)
        for voice_idx in range(len(self._voice_stay_count)):
            # Find which position this voice was at in previous chord
            prev_voice_pos = None
            for pos, voice in enumerate(self._voice_map):
                if voice == voice_idx:
                    prev_voice_pos = pos
                    break

            # Current position of this voice
            curr_voice_pos = voice_idx

            if prev_voice_pos is not None:
                prev_cents = prev_output_chord.pitches[prev_voice_pos].to_cents()
            else:
                prev_cents = None

            curr_cents = output_chord.pitches[curr_voice_pos].to_cents()

            if prev_cents is not None and prev_cents == curr_cents:
                self._voice_stay_count[voice_idx] += 1
            else:
                self._voice_stay_count[voice_idx] = 0

        # Create step with current state
        step = PathStep(
            graph_node=graph_node,
            output_chord=output_chord,
            transposition=trans,
            movements=movement,
            scores=chosen_scores if chosen_scores is not None else {},
            candidates=candidates,
            node_visit_counts=dict(self._node_visit_counts),
            voice_stay_count=tuple(self._voice_stay_count),
        )

        # Reset visit count for this node
        self._node_visit_counts[graph_node] = 0

        self.steps.append(step)
        return step

    @property
    def graph_chords(self) -> list[Chord]:
        """Get list of graph nodes (original chords)."""
        return [self.initial_chord] + [step.graph_node for step in self.steps]

    @property
    def output_chords(self) -> list[Chord]:
        """Get list of output chords (transposed)."""
        return [self.initial_chord] + [step.output_chord for step in self.steps]

    def __len__(self) -> int:
        """Total number of chords in path."""
        return len(self.steps) + 1

    def __iter__(self):
        """Iterate over output chords."""
        return iter(self.output_chords)

    def __getitem__(self, index: int) -> Chord:
        """Get output chord by index."""
        return self.output_chords[index]