use std::rc::Rc;
use std::error::Error;
use std::collections::HashMap;

use ::rasterizer::Font;
use ::{FontAtlas, Scale};
use ::texture::{Buffer2d, Bitmap};

#[derive(PartialEq, Eq, Hash)]
struct FaceKey {
    name: String,
    scale: Scale,
}

pub struct CachedFaceData<B> where B: Buffer2d {
    buffer: B,
    atlas: FontAtlas,
    line_height: f32,
}

#[derive(Debug)]
pub enum CacheError {
    NoSuchFont(String)
}

pub struct Cache<'a, B> where B: Buffer2d {
    fonts: HashMap<String, Font<'a>>,
    faces: HashMap<FaceKey, CachedFaceData<B>>,
    upload_queue: Vec<FaceKey>,
}

impl<'a, B> Cache<'a, B> where B: Buffer2d {
    pub fn new() -> Cache<'a, B> {
        Cache {
            fonts: HashMap::new(),
            faces: HashMap::new(),
            upload_queue: Vec::new(),
        }
    }

    pub fn add_font<S>(&mut self, name: S, font: Font<'a>) where S: Into<String> {
        self.fonts.insert(name.into(), font);
    }

    pub fn build_face<I, F>(&mut self, name: &str, scale: f32,
            chars: I, buffer_transform: F) -> Result<(), CacheError>
        where I: Iterator<Item=char>,
              F: Fn(Bitmap<u8>) -> Result<B, CacheError>
    {
        let key = FaceKey {name: String::from(name), scale: Scale(scale)};
        if self.faces.contains_key(&key) {
            return Ok(());
        }

        match self.fonts.get(name) {
            Some(font) => {
                let face_data = CachedFaceData::new(font, scale, chars, buffer_transform)?;
                self.faces.insert(key, face_data);

                Ok(())
            },
            None => Err(CacheError::NoSuchFont(name.into())),
        }
    }
}

impl<B> CachedFaceData<B> where B: Buffer2d {
    pub fn new<I, F>(font: &Font, scale: f32, chars: I, buffer_transform: F)
            -> Result<CachedFaceData<B>, CacheError>
        where I: Iterator<Item=char>,
              F: Fn(Bitmap<u8>) -> Result<B, CacheError>
    {
        let (atlas, bitmap, line_height): (FontAtlas, Bitmap<u8>, f32) = font.make_atlas(chars, scale, 1, 256, 256);

        let bitmap = buffer_transform(bitmap)?;

        Ok(CachedFaceData {
            buffer: bitmap,
            atlas: atlas,
            line_height: line_height,
        })
    }
}