extern crate rustc_serialize;

use self::rustc_serialize::json::{Json, ToJson};
use std::path::PathBuf;
use std::collections::BTreeMap;

#[derive(Debug, Clone)]
pub enum BookItem {
    Chapter(String, Chapter), // String = section
    Affix(Chapter),
    Spacer,
}

#[derive(Debug, Clone)]
pub struct Chapter {
    pub name: String,
    pub path: PathBuf,
    pub sub_items: Vec<BookItem>,
}

#[derive(Debug, Clone)]
pub struct BookItems<'a> {
    pub items: &'a [BookItem],
    pub current_index: usize,
    pub stack: Vec<(&'a [BookItem], usize)>,
}


impl Chapter {

    pub fn new(name: String, path: PathBuf) -> Self {

        Chapter {
            name: name,
            path: path,
            sub_items: vec![],
        }
    }
}


impl ToJson for Chapter {

    fn to_json(&self) -> Json {
        let mut m: BTreeMap<String, Json> = BTreeMap::new();
        m.insert("name".to_string(), self.name.to_json());
        m.insert("path".to_string(),self.path.to_str()
            .expect("Json conversion failed for path").to_json()
        );
        m.to_json()
    }
}



// Shamelessly copied from Rustbook
// (https://github.com/rust-lang/rust/blob/master/src/rustbook/book.rs)
impl<'a> Iterator for BookItems<'a> {
    type Item = &'a BookItem;

    fn next(&mut self) -> Option<&'a BookItem> {
        loop {
            if self.current_index >= self.items.len() {
                match self.stack.pop() {
                    None => return None,
                    Some((parent_items, parent_idx)) => {
                        self.items = parent_items;
                        self.current_index = parent_idx + 1;
                    }
                }
            } else {
                let cur = self.items.get(self.current_index).unwrap();

                match cur {
                    &BookItem::Chapter(_, ref ch) | &BookItem::Affix(ref ch) => {
                        self.stack.push((self.items, self.current_index));
                        self.items = &ch.sub_items[..];
                        self.current_index = 0;
                    },
                    &BookItem::Spacer => {
                        self.current_index += 1;
                    }
                }

                return Some(cur)
            }
        }
    }
}