use std::error::Error;
use std::sync::{RwLock, RwLockWriteGuard};

use iron::headers::ContentType;
use iron::modifier::Modifier;
use iron::prelude::*;
use iron::status;
use iron::{typemap, AfterMiddleware};
use plugin::Plugin as PluginFor;

use handlebars::{to_json, Handlebars, TemplateRenderError};
use serde::ser::Serialize as ToJson;
use serde_json::value::Value as Json;

use source::{Source, SourceError};

#[derive(Clone)]
pub struct Template {
    name: Option<String>,
    content: Option<String>,
    value: Json,
}

impl Template {
    /// render some template from pre-registered templates
    pub fn new<T: ToJson>(name: &str, value: T) -> Template {
        Template {
            name: Some(name.to_string()),
            value: to_json(&value),
            content: None,
        }
    }

    /// render some template with temporary template string
    pub fn with<T: ToJson>(content: &str, value: T) -> Template {
        Template {
            name: None,
            value: to_json(&value),
            content: Some(content.to_string()),
        }
    }
}

/// The handlebars template engine
pub struct HandlebarsEngine {
    pub sources: Vec<Box<dyn Source + Send + Sync>>,
    pub registry: RwLock<Box<Handlebars>>,
}

impl typemap::Key for HandlebarsEngine {
    type Value = Template;
}

impl Modifier<Response> for Template {
    fn modify(self, resp: &mut Response) {
        resp.extensions.insert::<HandlebarsEngine>(self);
    }
}

impl PluginFor<Response> for HandlebarsEngine {
    type Error = ();

    fn eval(resp: &mut Response) -> Result<Template, ()> {
        match resp.extensions.get::<HandlebarsEngine>() {
            Some(t) => Ok(t.clone()),
            None => Err(()),
        }
    }
}

impl HandlebarsEngine {
    /// create a handlebars template engine
    pub fn new() -> HandlebarsEngine {
        HandlebarsEngine {
            sources: Vec::new(),
            registry: RwLock::new(Box::new(Handlebars::new())),
        }
    }

    /// create a handlebars template engine from existed handlebars registry
    pub fn from(reg: Handlebars) -> HandlebarsEngine {
        HandlebarsEngine {
            sources: Vec::new(),
            registry: RwLock::new(Box::new(reg)),
        }
    }

    /// add a template source
    pub fn add(&mut self, source: Box<dyn Source + Send + Sync>) {
        self.sources.push(source);
    }

    /// load template from registered sources
    pub fn reload(&self) -> Result<(), SourceError> {
        let mut hbs = self.handlebars_mut();
        hbs.clear_templates();
        for s in self.sources.iter() {
            try!(s.load(&mut hbs))
        }
        Ok(())
    }

    /// access internal handlebars registry, useful to register custom helpers
    pub fn handlebars_mut(&self) -> RwLockWriteGuard<Box<Handlebars>> {
        self.registry.write().unwrap()
    }
}

impl AfterMiddleware for HandlebarsEngine {
    fn after(&self, _: &mut Request, mut resp: Response) -> IronResult<Response> {
        let page_wrapper = resp.extensions.remove::<HandlebarsEngine>().and_then(|h| {
            let hbs = self.registry.read().unwrap();
            if let Some(ref name) = h.name {
                Some(
                    hbs.render(name, &h.value)
                        .map_err(TemplateRenderError::from),
                )
            } else if let Some(ref content) = h.content {
                Some(hbs.render_template(content, &h.value))
            } else {
                None
            }
        });

        match page_wrapper {
            Some(page_result) => match page_result {
                Ok(page) => {
                    if !resp.headers.has::<ContentType>() {
                        resp.headers.set(ContentType::html());
                    }
                    resp.set_mut(page);
                    Ok(resp)
                }
                Err(e) => {
                    info!("{}", e.description());
                    Err(IronError::new(e, status::InternalServerError))
                }
            },
            None => Ok(resp),
        }
    }

    fn catch(&self, req: &mut Request, mut err: IronError) -> IronResult<Response> {
        err.response = try!(self.after(req, err.response));
        Err(err)
    }
}

#[cfg(test)]
mod test {
    use handlebars::{Context, Handlebars, Helper, Output, RenderContext, RenderError};
    use iron::prelude::*;
    use middleware::*;
    use std::collections::BTreeMap;

    fn hello_world() -> IronResult<Response> {
        let resp = Response::new();

        let mut data = BTreeMap::new();
        data.insert("title".to_owned(), "Handlebars on Iron".to_owned());

        Ok(resp.set(Template::new("index", data)))
    }

    fn hello_world2() -> IronResult<Response> {
        let resp = Response::new();

        let mut data = BTreeMap::new();
        data.insert("title".to_owned(), "Handlebars on Iron".to_owned());

        Ok(resp.set(Template::with("{{title}}", data)))
    }

    #[test]
    fn test_resp_set() {
        let mut resp = hello_world().ok().expect("response expected");

        // use response plugin to retrieve a cloned template for testing
        match resp.get::<HandlebarsEngine>() {
            Ok(h) => {
                assert_eq!(h.name.unwrap(), "index".to_string());
                assert_eq!(
                    h.value
                        .as_object()
                        .unwrap()
                        .get(&"title".to_string())
                        .unwrap()
                        .as_str()
                        .unwrap(),
                    "Handlebars on Iron"
                );
            }
            _ => panic!("template expected"),
        }
    }

    #[test]
    fn test_resp_set2() {
        let mut resp = hello_world2().ok().expect("response expected");

        // use response plugin to retrieve a cloned template for testing
        match resp.get::<HandlebarsEngine>() {
            Ok(h) => {
                assert_eq!(h.content.unwrap(), "{{title}}".to_string());
                assert_eq!(
                    h.value
                        .as_object()
                        .unwrap()
                        .get(&"title".to_string())
                        .unwrap()
                        .as_str()
                        .unwrap(),
                    "Handlebars on Iron"
                );
            }
            _ => panic!("template expected"),
        }
    }

    #[test]
    fn test_register_helper() {
        let hbs = HandlebarsEngine::new();
        let mut reg = hbs.handlebars_mut();
        reg.register_helper(
            "ignore",
            Box::new(
                |_: &Helper,
                 _: &Handlebars,
                 _: &Context,
                 _: &mut RenderContext,
                 _: &mut dyn Output|
                 -> Result<(), RenderError> { Ok(()) },
            ),
        );
    }
}