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extern crate handlebars;
extern crate rustc_serialize;
extern crate notify;
#[macro_use] extern crate log;

use std::sync::{Arc, RwLock};
use std::sync::mpsc::channel;
use std::{io, thread};
use std::fs::{self};
use std::path::Path;

use rustc_serialize::json::ToJson;
use notify::{RecommendedWatcher, Error, Watcher};
use handlebars::{RenderError, Handlebars};

//".hbs"
pub struct TemplateEngine {
    handlebars: RwLock<Box<Handlebars>>,
    template_dir: String,
    extension: String,
}

impl TemplateEngine {
    pub fn new(template_dir: &str, extension: &str) -> Arc<Self> {
        let engine = Arc::new(TemplateEngine {
            handlebars: RwLock::new(Box::new(Handlebars::new())),
            template_dir: String::from(template_dir),
            extension: String::from(extension),
        });
        engine.reload();
        engine.watch();
        engine
    }
    pub fn render<T: ToJson + Sized>(&self, name: &str, data: &T) -> Result<String, RenderError> {
        let handlebars = self.handlebars.read().unwrap();
        handlebars.render(name, data)
    }
    fn reload(&self) {
        let mut handlebars = self.handlebars.write().unwrap();
        handlebars.clear_templates();
        let files = self.collect_files();
        debug!("reload templates start");
        for file in files {
            let name = file.trim_left_matches(&self.template_dir).trim_right_matches(&self.extension);
            match handlebars.register_template_file(&name, &Path::new(&file)) {
                Err(e) => {
                    panic!("error:{}",e);
                },
                Ok(_) => {
                    debug!("{}->{}", name, file);
                }
            }
        }
        debug!("reload templates end");
    }

    fn collect_files(&self) -> Vec<String> {
        let mut vec: Vec<String> = Vec::new();
        fn _collect(dir: &Path, vec: &mut Vec<String>) -> io::Result<()> {
            if dir.exists() && try!(fs::metadata(dir)).is_dir() {
                for entry in try!(fs::read_dir(dir)) {
                    let entry = try!(entry);
                    if try!(fs::metadata(entry.path())).is_dir() {
                        try!(_collect(&entry.path(), vec));
                    } else {
                        let path = entry.path();
                        if let Some(extension) = path.extension().map(|s| s.to_str().unwrap()) {
                            if extension == "hbs" {
                                vec.push(format!("{}", path.to_string_lossy()));
                            }
                        }
                    }
                }
            }
            Ok(())
        }
        _collect(Path::new(&self.template_dir), &mut vec).unwrap();
        vec
    }
}

trait Watchable {
    fn watch(&self);
}

impl Watchable for Arc<TemplateEngine> {
    fn watch(&self) {
        fn _watch(engine: &Arc<TemplateEngine>) -> Result<(), Error> {
            let (tx, rx) = channel();
            let mut watcher: RecommendedWatcher = try!(Watcher::new(tx));
            let p = Path::new(&engine.template_dir);
            try!(watcher.watch(p));
            loop {
                let _ = rx.recv();
                info!("Template directory changed");
                engine.reload();
            }
        }
        let engine = self.clone();
        thread::spawn(move || {
            match _watch(&engine) {
                Ok(_) => (),
                Err(e) => {
                    warn!("Failed to watch directory: {:?}", e);
                    panic!("error watch:{}",e);
                }
            }
        });
    }
}