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

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


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,
    ) -> tuple[list["Chord"], list["Chord"]]:
        """Find a stochastic path through the graph.

        Returns:
            Tuple of (path, graph_path) where:
            - path: list of output Chord objects (transposed)
            - graph_path: list of original graph Chord objects (untransposed)
        """
        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 [], []

        original_chord = chord[0]
        graph_node = original_chord
        output_chord = original_chord

        path = [output_chord]
        last_graph_nodes = (graph_node,)

        graph_path = [graph_node]

        from .pitch import Pitch

        dims = output_chord.dims
        cumulative_trans = Pitch(tuple(0 for _ in range(len(dims))), dims)

        num_voices = len(output_chord.pitches)
        voice_map = list(range(num_voices))

        voice_stay_count = [0] * num_voices

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

            if not out_edges:
                break

            weights = self._calculate_edge_weights(
                out_edges,
                path,
                last_graph_nodes,
                weights_config,
                tuple(voice_stay_count),
                graph_path,
                cumulative_trans,
            )

            edge = choices(out_edges, weights=weights)[0]
            next_graph_node = edge[1]
            trans = edge[2].get("transposition")
            movement = edge[2].get("movements", {})

            new_voice_map = [None] * num_voices
            for src_idx, dest_idx in movement.items():
                new_voice_map[dest_idx] = voice_map[src_idx]
            voice_map = new_voice_map

            if trans is not None:
                cumulative_trans = cumulative_trans.transpose(trans)

            transposed = next_graph_node.transpose(cumulative_trans)

            reordered_pitches = tuple(
                transposed.pitches[voice_map[i]] for i in range(num_voices)
            )
            from .chord import Chord

            output_chord = Chord(reordered_pitches, dims)

            for voice_idx in range(num_voices):
                curr_cents = path[-1].pitches[voice_idx].to_cents()
                next_cents = output_chord.pitches[voice_idx].to_cents()
                if curr_cents == next_cents:
                    voice_stay_count[voice_idx] += 1
                else:
                    voice_stay_count[voice_idx] = 0

            graph_node = next_graph_node
            graph_path.append(graph_node)

            path.append(output_chord)
            last_graph_nodes = last_graph_nodes + (graph_node,)
            if len(last_graph_nodes) > 2:
                last_graph_nodes = last_graph_nodes[-2:]

        return path, graph_path

    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

                weights = self._calculate_edge_weights(
                    out_edges, [chord], (chord,), weights_config, None
                )
                nonzero = sum(1 for w in weights if w > 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 _calculate_edge_weights(
        self,
        out_edges: list,
        path: list["Chord"],
        last_chords: tuple["Chord", ...],
        config: dict,
        voice_stay_count: tuple[int, ...] | None = None,
        graph_path: list["Chord"] | None = None,
        cumulative_trans: "Pitch | None" = None,
    ) -> list[float]:
        """Calculate weights for edges based on configuration.

        Uses hybrid approach:
        - Hard factors (direct tuning, voice crossing): multiplication (eliminate if factor fails)
        - Soft factors (melodic, contrary, hamiltonian, dca, target range): weighted sum
        """
        weights = []

        for edge_idx, edge in enumerate(out_edges):
            w = 1.0  # base weight
            edge_data = edge[2]

            # Hard factors (multiplication - eliminate edge if factor = 0)
            # Direct tuning
            direct_tuning_factor = self._factor_direct_tuning(edge_data, config)
            w *= direct_tuning_factor

            if w == 0:
                weights.append(0)
                continue

            # Voice crossing
            voice_crossing_factor = self._factor_voice_crossing(edge_data, config)
            w *= voice_crossing_factor

            if w == 0:
                weights.append(0)
                continue

            # Soft factors (weighted sum)
            w += self._factor_melodic_threshold(edge_data, config) * config.get(
                "weight_melodic", 1
            )
            w += self._factor_contrary_motion(edge_data, config) * config.get(
                "weight_contrary_motion", 0
            )
            w += self._factor_hamiltonian(edge, graph_path, config) * config.get(
                "weight_hamiltonian", 1
            )

            w += self._factor_dca(
                edge, path, voice_stay_count, config, cumulative_trans
            ) * config.get("weight_dca", 1)
            w += self._factor_target_range(
                edge, path, config, cumulative_trans
            ) * config.get("weight_target_range", 1)

            weights.append(w)

        return weights

    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_hamiltonian(
        self, edge: tuple, graph_path: list | None, config: dict
    ) -> float:
        """Returns 1.0 if destination not visited, lower if already visited."""
        # Check weight - if 0, return 1.0 (neutral)
        if config.get("weight_hamiltonian", 1) == 0:
            return 1.0

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

        destination = edge[1]
        if graph_path and destination in graph_path:
            return 0.1  # penalize revisiting
        return 1.0

    def _factor_dca(
        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", 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)