// Copyright © 2020 Intel Corporation
//
// SPDX-License-Identifier: Apache-2.0

use std::collections::HashMap;
use std::sync::{Arc, Mutex};
use vm_device::Resource;
use vm_migration::Migratable;

#[derive(Clone, Serialize, Deserialize)]
pub struct DeviceNode {
    pub id: String,
    pub resources: Vec<Resource>,
    pub parent: Option<String>,
    pub children: Vec<String>,
    #[serde(skip)]
    pub migratable: Option<Arc<Mutex<dyn Migratable>>>,
    pub pci_bdf: Option<u32>,
}

impl DeviceNode {
    pub fn new(id: String, migratable: Option<Arc<Mutex<dyn Migratable>>>) -> Self {
        DeviceNode {
            id,
            resources: Vec::new(),
            parent: None,
            children: Vec::new(),
            migratable,
            pci_bdf: None,
        }
    }
}

#[macro_export]
macro_rules! device_node {
    ($id:ident) => {
        DeviceNode::new($id.clone(), None)
    };
    ($id:ident, $device:ident) => {
        DeviceNode::new(
            $id.clone(),
            Some(Arc::clone(&$device) as Arc<Mutex<dyn Migratable>>),
        )
    };
}

#[derive(Clone, Default, Serialize, Deserialize)]
pub struct DeviceTree(HashMap<String, DeviceNode>);

impl DeviceTree {
    pub fn new() -> Self {
        DeviceTree(HashMap::new())
    }
    pub fn get(&self, k: &str) -> Option<&DeviceNode> {
        self.0.get(k)
    }
    pub fn get_mut(&mut self, k: &str) -> Option<&mut DeviceNode> {
        self.0.get_mut(k)
    }
    pub fn insert(&mut self, k: String, v: DeviceNode) -> Option<DeviceNode> {
        self.0.insert(k, v)
    }
    pub fn remove(&mut self, k: &str) -> Option<DeviceNode> {
        self.0.remove(k)
    }
    pub fn iter(&self) -> std::collections::hash_map::Iter<String, DeviceNode> {
        self.0.iter()
    }
    pub fn breadth_first_traversal(&self) -> BftIter {
        BftIter::new(&self.0)
    }
}

// Breadth first traversal iterator.
pub struct BftIter<'a> {
    nodes: Vec<&'a DeviceNode>,
}

impl<'a> BftIter<'a> {
    fn new(hash_map: &'a HashMap<String, DeviceNode>) -> Self {
        let mut nodes = Vec::new();

        for (_, node) in hash_map.iter() {
            if node.parent.is_none() {
                nodes.push(node);
            }
        }

        let mut node_layer = nodes.as_slice();
        loop {
            let mut next_node_layer = Vec::new();

            for node in node_layer.iter() {
                for child_node_id in node.children.iter() {
                    if let Some(child_node) = hash_map.get(child_node_id) {
                        next_node_layer.push(child_node);
                    }
                }
            }

            if next_node_layer.is_empty() {
                break;
            }

            let pos = nodes.len();
            nodes.extend(next_node_layer);

            node_layer = &nodes[pos..];
        }

        BftIter { nodes }
    }
}

impl<'a> Iterator for BftIter<'a> {
    type Item = &'a DeviceNode;

    fn next(&mut self) -> Option<Self::Item> {
        if self.nodes.is_empty() {
            None
        } else {
            Some(self.nodes.remove(0))
        }
    }
}

impl<'a> DoubleEndedIterator for BftIter<'a> {
    fn next_back(&mut self) -> Option<Self::Item> {
        self.nodes.pop()
    }
}

#[cfg(test)]
mod tests {
    use super::{DeviceNode, DeviceTree};

    #[test]
    fn test_device_tree() {
        test_block!(tb, "", {
            // Check new()
            let mut device_tree = DeviceTree::new();
            aver_eq!(tb, device_tree.0.len(), 0);

            // Check insert()
            let id = String::from("id1");
            device_tree.insert(id.clone(), DeviceNode::new(id.clone(), None));
            aver_eq!(tb, device_tree.0.len(), 1);
            let node = device_tree.0.get(&id);
            aver!(tb, node.is_some());
            let node = node.unwrap();
            aver_eq!(tb, node.id, id);

            // Check get()
            let id2 = String::from("id2");
            aver!(tb, device_tree.get(&id).is_some());
            aver!(tb, device_tree.get(&id2).is_none());

            // Check get_mut()
            let node = device_tree.get_mut(&id).unwrap();
            node.id = id2.clone();
            let node = device_tree.0.get(&id).unwrap();
            aver_eq!(tb, node.id, id2);

            // Check remove()
            let node = device_tree.remove(&id).unwrap();
            aver_eq!(tb, node.id, id2);
            aver_eq!(tb, device_tree.0.len(), 0);

            // Check iter()
            let disk_id = String::from("disk0");
            let net_id = String::from("net0");
            let rng_id = String::from("rng0");
            let device_list = vec![
                (disk_id.clone(), device_node!(disk_id)),
                (net_id.clone(), device_node!(net_id)),
                (rng_id.clone(), device_node!(rng_id)),
            ];
            device_tree.0.extend(device_list);
            for (id, node) in device_tree.iter() {
                if id == &disk_id {
                    aver_eq!(tb, node.id, disk_id);
                } else if id == &net_id {
                    aver_eq!(tb, node.id, net_id);
                } else if id == &rng_id {
                    aver_eq!(tb, node.id, rng_id);
                } else {
                    aver!(tb, false);
                }
            }

            // Check breadth_first_traversal() based on the following hierarchy
            //
            // 0
            // | \
            // 1  2
            // |  | \
            // 3  4  5
            //
            let mut device_tree = DeviceTree::new();
            let child_1_id = String::from("child1");
            let child_2_id = String::from("child2");
            let child_3_id = String::from("child3");
            let parent_1_id = String::from("parent1");
            let parent_2_id = String::from("parent2");
            let root_id = String::from("root");
            let mut child_1_node = device_node!(child_1_id);
            let mut child_2_node = device_node!(child_2_id);
            let mut child_3_node = device_node!(child_3_id);
            let mut parent_1_node = device_node!(parent_1_id);
            let mut parent_2_node = device_node!(parent_2_id);
            let mut root_node = device_node!(root_id);
            child_1_node.parent = Some(parent_1_id.clone());
            child_2_node.parent = Some(parent_2_id.clone());
            child_3_node.parent = Some(parent_2_id.clone());
            parent_1_node.children = vec![child_1_id.clone()];
            parent_1_node.parent = Some(root_id.clone());
            parent_2_node.children = vec![child_2_id.clone(), child_3_id.clone()];
            parent_2_node.parent = Some(root_id.clone());
            root_node.children = vec![parent_1_id.clone(), parent_2_id.clone()];
            let device_list = vec![
                (child_1_id.clone(), child_1_node),
                (child_2_id.clone(), child_2_node),
                (child_3_id.clone(), child_3_node),
                (parent_1_id.clone(), parent_1_node),
                (parent_2_id.clone(), parent_2_node),
                (root_id.clone(), root_node),
            ];
            device_tree.0.extend(device_list);

            let iter_vec = device_tree
                .breadth_first_traversal()
                .collect::<Vec<&DeviceNode>>();
            aver_eq!(tb, iter_vec.len(), 6);
            aver_eq!(tb, iter_vec[0].id, root_id);
            aver_eq!(tb, iter_vec[1].id, parent_1_id);
            aver_eq!(tb, iter_vec[2].id, parent_2_id);
            aver_eq!(tb, iter_vec[3].id, child_1_id);
            aver_eq!(tb, iter_vec[4].id, child_2_id);
            aver_eq!(tb, iter_vec[5].id, child_3_id);

            let iter_vec = device_tree
                .breadth_first_traversal()
                .rev()
                .collect::<Vec<&DeviceNode>>();
            aver_eq!(tb, iter_vec.len(), 6);
            aver_eq!(tb, iter_vec[5].id, root_id);
            aver_eq!(tb, iter_vec[4].id, parent_1_id);
            aver_eq!(tb, iter_vec[3].id, parent_2_id);
            aver_eq!(tb, iter_vec[2].id, child_1_id);
            aver_eq!(tb, iter_vec[1].id, child_2_id);
            aver_eq!(tb, iter_vec[0].id, child_3_id);

            Ok(())
        })
    }
}