use crate::error::OpossumError;
use crate::optic_node::{OpticNode, Optical};
use petgraph::algo::*;
use petgraph::prelude::{DiGraph, EdgeIndex, NodeIndex};

type Result<T> = std::result::Result<T, OpossumError>;

#[derive(Default)]
pub struct NodeGroup {
    g: DiGraph<OpticNode, ()>,
}

impl NodeGroup {
    pub fn new() -> Self {
        Self::default()
    }
    /// Add a given [`OpticNode`] to the graph of this [`NodeGroup`].
    ///
    /// This command just adds an [`OpticNode`] but does not connect it to existing nodes in the (sub-)graph. The given node is
    /// consumed (owned) by the [`NodeGroup`].
    pub fn add_node(&mut self, node: OpticNode) -> NodeIndex {
        self.g.add_node(node)
    }
    /// Connect (already existing) nodes denoted by the respective `NodeIndex`.
    ///
    /// Both node indices must exist. Otherwise an [`OpticSceneryError`] is returned. In addition, connections are
    /// rejected and an [`OpticSceneryError`] is returned, if the graph would form a cycle (loop in the graph).
    pub fn connect_nodes(
        &mut self,
        src_node: NodeIndex,
        target_node: NodeIndex,
    ) -> Result<EdgeIndex> {
        if self.g.node_weight(src_node).is_none() {
            return Err(OpossumError);
        }
        if self.g.node_weight(target_node).is_none() {
            return Err(OpossumError);
        }
        let edge_index = self.g.add_edge(src_node, target_node, ());
        if is_cyclic_directed(&self.g) {
            self.g.remove_edge(edge_index);
            return Err(OpossumError);
        }
        Ok(edge_index)
    }
}

impl Optical for NodeGroup {
    fn node_type(&self) -> &str {
        "group"
    }

    fn to_dot(&self, node_index: &str, name: &str, inverted: bool) -> String {
        let inv_string = if inverted { "(inv)" } else { "" };
        let mut dot_string = format!(
            "  subgraph \"cluster_{}\" {{\n    label=\"{}{}\"\n",
            node_index, name, inv_string
        );
        for node_idx in self.g.node_indices() {
            let node = self.g.node_weight(node_idx).unwrap();
            dot_string += &node.to_dot(&format!("    {}_i{}", node_index, node_idx.index()));
        }
        for edge in self.g.edge_indices() {
            let end_nodes = self.g.edge_endpoints(edge).unwrap();
            dot_string.push_str(&format!(
                "      {}_i{} -> {}_i{}\n",
                node_index,
                end_nodes.0.index(),
                node_index,
                end_nodes.1.index()
            ));
        }
        dot_string += "  }\n";
        dot_string
    }
}