use super::*;
use std::path::PathBuf;
use std::collections::HashMap;
use std::io;

use futures::prelude::*;
use futures::future::join_all;
use futures::future::BoxFuture;

use tokio::task::JoinHandle;
use tokio::fs;

use data::INode;
use data::FsInfo;
use state::State;
use data::INodeInfoGraph;
use config::Config;

async fn process_entry(entry: &tokio::fs::DirEntry, parent: INode) -> io::Result<FsInfo>
{
    let meta = entry.metadata().await?;
    if meta.is_dir()
    {
	Ok(FsInfo::Directory(parent))
    } else if meta.is_file()
    {
	Ok(FsInfo::File(meta.len(), parent))
    } else
    {
	Err(io::Error::new(io::ErrorKind::Other, "Unknown file type"))
    }
}

/// Walk on all paths in this state, then return a joined map of all
///
/// # Panics
/// If there are any more held references to `state`.
pub async fn work_on_all(state: State) -> (INodeInfoGraph, Config)
{
    let comp_children = join_all(state.config().paths.iter().map(|path| {
	let path = path.clone();
	async  {
	    match tokio::fs::symlink_metadata(&path).await {
		Ok(meta) => {
		    let inode = meta.inode();
		    tokio::spawn(walk(state.clone(), path, inode)).await
			.ok()
		},
		Err(err) => {
		    cfg_eprintln!(state.config(), "Failed to stat root {:?}: {}", path, err);
		    None
		},
	    }
	}
    })).await;

    // All children have completed here. Unwrap cache
    let (ino_map, cfg) = {
	let (cache, cfg) = state.try_into_cache().unwrap();
	(cache.try_complete().await.unwrap(), cfg)
    };
    let mut output = HashMap::with_capacity(ino_map.len());

    for path_comp in comp_children
    {
	if let Some(res) = path_comp
	{
	    output.extend(res);
	}
    }

    (INodeInfoGraph::new(
	ino_map,
	output,
    ), cfg)
}

/// Walk this directory.
///
/// # Returns
/// A *unjoined* map of relative paths and `INode`s inserted into the state's `Cache`.
/// The caller must join its `root` with these paths to provide a normalized map.
/// Recusrive calls to `walk` handle this automatically.
fn walk(state: State, root: PathBuf, root_ino: INode) -> BoxFuture<'static, HashMap<PathBuf, INode>>
{
    let mut output = HashMap::new();
    let mut children: Vec<JoinHandle<HashMap<PathBuf, INode>>> = Vec::new();
    async move {
	{
	    let _guard = state.lock().enter().await;

	    cfg_println!(state.config(), " -> {:?}", root); //TODO: Flag to disable this?

	    match fs::read_dir(&root).await
	    {
		Ok(mut dir) => {
		    while let Some(entry) = dir.next().await
		    {
			match entry
			{
			    Ok(entry) => {
				let ino = entry.inode();
				// Check cache for this
				if state.cache().get(&ino).await.is_none() {
				    // Not added, process.
				    match process_entry(&entry, root_ino).await {
					Ok(fsinfo) => {
					    let path = entry.path();
					    if fsinfo.is_dir()
					    {
						if let Some(next) = state.deeper()
						{
						    children.push(tokio::spawn(
							walk(next, path.clone(), ino)
						    ));
						}
					    }
					    output.insert(path, ino);
					    let mut cache = state.cache_sub();
					    cache.insert(ino, fsinfo).await;
        				},
					Err(err) => cfg_eprintln!(state.config(), "Failed to stat {:?}: {}", entry.path(), err),
				    }
				}
			    },
			    Err(err) => cfg_eprintln!(state.config(), "Walking {:?} failed: {}", root, err),
			}
		    }
		},
		Err(err) => cfg_eprintln!(state.config(), "Failed to walk {:?}: {}", root, err),
	    }
	    // drop work guard here
	}
	// Join all children
	for child in join_all(children.into_iter()).await
	{
	    if let Ok(map) = child
	    {
		output.extend(map);
	    } else {
		cfg_eprintln!(state.config(), "Child panic");
	    }
	}
	
	output
    }.boxed()
}