use std::collections::HashMap;
use std::sync::{Arc, RwLock};

use file_route::FileRoute;
use id::{Id, get_id};
use message_session::{Message, MessageSession};
use partition::Partition;
use project::Project;
use rbx::{RbxInstance, RbxTree};
use vfs_session::{VfsSession, FileItem, FileChange};

// TODO: Rethink data structure and insertion/update behavior. Maybe break some
// pieces off into a new object?
fn file_to_instances(
    file_item: &FileItem,
    partition: &Partition,
    tree: &mut RbxTree,
    instances_by_route: &mut HashMap<FileRoute, Id>,
    parent_id: Option<Id>,
) -> (Id, Vec<Id>) {
    match file_item {
        FileItem::File { contents, route } => {
            let primary_id = match instances_by_route.get(&file_item.get_route()) {
                Some(&id) => id,
                None => {
                    let id = get_id();
                    instances_by_route.insert(route.clone(), id);

                    id
                },
            };

            // This is placeholder logic; this whole function is!
            let (class_name, property_key, name) = {
                let file_name = route.route.last().unwrap_or(&route.partition);

                fn strip_suffix<'a>(source: &'a str, suffix: &'static str) -> &'a str {
                    &source[..source.len() - suffix.len()]
                }

                if file_name.ends_with(".client.lua") {
                    ("LocalScript", "Source", strip_suffix(&file_name, ".client.lua"))
                } else if file_name.ends_with(".server.lua") {
                    ("Script", "Source", strip_suffix(&file_name, ".server.lua"))
                } else if file_name.ends_with(".lua") {
                    ("ModuleScript", "Source", strip_suffix(&file_name, ".lua"))
                } else {
                    // TODO: Error/warn/skip instead of falling back
                    ("StringValue", "Value", file_name.as_str())
                }
            };

            let mut properties = HashMap::new();
            properties.insert(property_key.to_string(), contents.clone());

            tree.insert_instance(primary_id, RbxInstance {
                name: name.to_string(),
                class_name: class_name.to_string(),
                properties,
                children: Vec::new(),
                parent: parent_id,
            });

            (primary_id, vec![primary_id])
        },
        FileItem::Directory { children, route } => {
            let primary_id = match instances_by_route.get(&file_item.get_route()) {
                Some(&id) => id,
                None => {
                    let id = get_id();
                    instances_by_route.insert(route.clone(), id);

                    id
                },
            };

            let mut child_ids = Vec::new();

            let mut changed_ids = vec![primary_id];

            for child_file_item in children.values() {
                let (child_id, mut child_changed_ids) = file_to_instances(child_file_item, partition, tree, instances_by_route, Some(primary_id));

                child_ids.push(child_id);
                changed_ids.push(child_id);

                // TODO: Should I stop using drain on Vecs of Copyable types?
                for id in child_changed_ids.drain(..) {
                    changed_ids.push(id);
                }
            }

            tree.insert_instance(primary_id, RbxInstance {
                name: route.name(partition).to_string(),
                class_name: "Folder".to_string(),
                properties: HashMap::new(),
                children: child_ids,
                parent: parent_id,
            });

            (primary_id, changed_ids)
        },
    }
}

pub struct RbxSession {
    project: Project,

    vfs_session: Arc<RwLock<VfsSession>>,

    message_session: MessageSession,

    /// The RbxInstance that represents each partition.
    // TODO: Can this be removed in favor of instances_by_route?
    pub partition_instances: HashMap<String, Id>,

    /// Keeps track of all of the instances in the tree
    pub tree: RbxTree,

    /// A map from files in the VFS to instances loaded in the session.
    instances_by_route: HashMap<FileRoute, Id>,
}

impl RbxSession {
    pub fn new(project: Project, vfs_session: Arc<RwLock<VfsSession>>, message_session: MessageSession) -> RbxSession {
        RbxSession {
            project,
            vfs_session,
            message_session,
            partition_instances: HashMap::new(),
            tree: RbxTree::new(),
            instances_by_route: HashMap::new(),
        }
    }

    pub fn read_partitions(&mut self) {
        let vfs_session_arc = self.vfs_session.clone();
        let vfs_session = vfs_session_arc.read().unwrap();

        for partition in self.project.partitions.values() {
            let route = FileRoute {
                partition: partition.name.clone(),
                route: Vec::new(),
            };
            let file_item = vfs_session.get_by_route(&route).unwrap();

            let parent_id = match route.parent() {
                Some(parent_route) => match self.instances_by_route.get(&parent_route) {
                    Some(&parent_id) => Some(parent_id),
                    None => None,
                },
                None => None,
            };

            let (root_id, _) = file_to_instances(file_item, partition, &mut self.tree, &mut self.instances_by_route, parent_id);

            self.partition_instances.insert(partition.name.clone(), root_id);
        }
    }

    pub fn handle_change(&mut self, change: &FileChange) {
        let vfs_session_arc = self.vfs_session.clone();
        let vfs_session = vfs_session_arc.read().unwrap();

        match change {
            FileChange::Created(route) | FileChange::Updated(route) => {
                let file_item = vfs_session.get_by_route(route).unwrap();
                let partition = self.project.partitions.get(&route.partition).unwrap();

                let parent_id = match route.parent() {
                    Some(parent_route) => match self.instances_by_route.get(&parent_route) {
                        Some(&parent_id) => Some(parent_id),
                        None => None,
                    },
                    None => None,
                };

                let (_, changed_ids) = file_to_instances(file_item, partition, &mut self.tree, &mut self.instances_by_route, parent_id);

                let messages = changed_ids
                    .iter()
                    .map(|&id| Message::InstanceChanged { id })
                    .collect::<Vec<_>>();

                self.message_session.push_messages(&messages);
            },
            FileChange::Deleted(route) => {
                match self.instances_by_route.get(route) {
                    Some(&id) => {
                        self.tree.delete_instance(id);
                        self.instances_by_route.remove(route);
                        self.message_session.push_messages(&[Message::InstanceChanged { id }]);
                    },
                    None => (),
                }
            },
            FileChange::Moved(from_route, to_route) => {
                let mut messages = Vec::new();

                match self.instances_by_route.get(from_route) {
                    Some(&id) => {
                        self.tree.delete_instance(id);
                        self.instances_by_route.remove(from_route);
                        messages.push(Message::InstanceChanged { id });
                    },
                    None => (),
                }

                let file_item = vfs_session.get_by_route(to_route).unwrap();
                let partition = self.project.partitions.get(&to_route.partition).unwrap();

                let parent_id = match to_route.parent() {
                    Some(parent_route) => match self.instances_by_route.get(&parent_route) {
                        Some(&parent_id) => Some(parent_id),
                        None => None,
                    },
                    None => None,
                };

                let (_, changed_ids) = file_to_instances(file_item, partition, &mut self.tree, &mut self.instances_by_route, parent_id);

                for id in changed_ids {
                    messages.push(Message::InstanceChanged { id });
                }

                self.message_session.push_messages(&messages);
            },
        }
    }
}