from collections import defaultdict, deque
from pathlib import Path
from threading import Lock
from typing import List, Optional
from typing_extensions import Self
import yaml

from app.const import CONFIG_DIR


class PipelineManager:
    _instance = None
    _lock = Lock()

    def __new__(cls, pipeline_setup_path: Optional[Path] = None) -> Self:
        with cls._lock:
            if cls._instance is None:
                setup_path = Path(pipeline_setup_path or (CONFIG_DIR / "pipeline_settings.yaml"))
                cls._instance = super(PipelineManager, cls).__new__(cls)
                cls._instance.build(setup_path)
        return cls._instance
    
    def build(self, pipeline_setup_path: Path):

        with open(pipeline_setup_path, "r", encoding='utf8') as f:
            self.pipeline_setup = yaml.safe_load(f)

        self._nodes = []
        self._node_map = {}
        for key in self.pipeline_setup:
            setattr(self, key, self.pipeline_setup[key])
            self._nodes.append(key)
            self._node_map[key] = self.pipeline_setup[key]
        
        self._topological_sort()

    def _topological_sort(self):
        graph = defaultdict(list)
        in_degree = {node: 0 for node in self._nodes}

        for key, setup in self._node_map.items():
            for dep in setup["dependencies"]:
                graph[dep].append(key)
                in_degree[key] += 1
        
        queue = deque([node for node in self._nodes if in_degree[node] == 0])
        sorted_order = []

        while queue:
            current = queue.popleft()
            sorted_order.append(current)
            for neighbor in graph[current]:
                in_degree[neighbor] -= 1
                if in_degree[neighbor] == 0:
                    queue.append(neighbor)
        
        if len(sorted_order) != len(self._nodes):
            raise ValueError("Cycle detected in pipeline dependencies")
        self._nodes = sorted_order

    def get_node_config(self, node_name: str) -> dict:
        if hasattr(self, node_name):
            return getattr(self, node_name)
        raise ValueError(f"Node {node_name} not found in pipeline configuration")

    @property
    def nodes(self):
        return self._nodes
    
    @property
    def node_map(self):
        return self._node_map