use std::path::{PathBuf, Path};
use std::fs;
use std::io;
use std::io::{Read, Seek};
use image::io::Reader as ImageReader;
use image::error::ImageError;
use image::imageops;
use serde::Serialize;

use crate::context::Context;

#[derive(Debug)]
pub enum LoadError {
    Io(io::Error),
    ExifParser(exif::Error)
}

#[derive(Debug)]
pub enum ConversionError {
    Io(io::Error),
    ImageError(ImageError),
}

#[derive(Debug, Serialize)]
pub struct Picture {
    pub taken: Option<String>,
    hash: String,
    pub path: PathBuf,
}

pub struct Converter<'a> {
    imgdata: Option<image::DynamicImage>,
    pic: &'a Picture,
}

fn hash_reader<R: Read>(reader: &mut R) -> Result<String, io::Error> {
    let mut hash = md5::Context::new();
    let mut buff = [0; 1024];

    loop {
        let count = reader.read(&mut buff)?;
        if count == 0 {
            // Reached end, stopping
            break
        }

        hash.consume(&buff[..count])
    }

    Ok(format!("{:?}", hash.compute()))
}

impl Picture {
    /// Hash file content and load exif data.
    pub fn new_from_file(path: &Path) -> Result<Self, LoadError> {
        let file = fs::File::open(path)?;
        let mut reader = io::BufReader::new(&file);

        let taken = match exif::Reader::new().read_from_container(&mut reader) {
            Ok(exif) => exif.get_field(exif::Tag::DateTimeOriginal, exif::In::PRIMARY)
                .map(|field| field.display_value().with_unit(&exif).to_string()),
            Err(err) => {
                println!("Could not load exif data for {}: {}", path.to_str().unwrap(), err);
                None
            }
        };

        // Move back to start of file for hashing
        reader.seek(io::SeekFrom::Start(0))?;

        Ok(Picture {
            taken,
            hash: hash_reader(&mut reader)?,
            path: path.to_path_buf(),
        })
    }

    pub fn convert(&self) -> Result<Converter, ConversionError> {
        Ok(Converter {
            imgdata: None,
            pic: self,
        })
    }
}

impl Converter<'_> {
    fn convert_image(&mut self, size: u32, dest: &Path) -> Result<(), ImageError> {
        let scaled = self.get_imgdata()?.resize(
            size,
            std::u32::MAX,
            imageops::FilterType::Lanczos3);

        scaled.save(dest)
    }

    fn get_imgdata(&mut self) -> Result<&image::DynamicImage, ImageError> {
        let picpath = &self.pic.path;

        match self.imgdata {
            None => self.imgdata = Some(
                ImageReader::open(picpath)?.decode()?
                ),
            _ => ()
        }

        Ok(self.imgdata.as_ref().unwrap())
    }

    pub fn get_size(&mut self, ctx: &Context, size: u32) -> Result<PathBuf, ImageError> {
        let hash = md5::compute(format!("{},{},{}", size, ctx.options.ext, self.pic.hash));
        let name = format!("{:?}.{}", hash, ctx.options.ext);
        let path = ctx.imgdir.join(name);

        match path.exists() {
            true => {
                println!("Image of size {} already exists", size);
                Ok(path)
            },
            false => {
                println!("Scaling image to size {}", size);
                self.convert_image(size, &path)?;
                Ok(path)
            }
        }
    }
}

impl From<io::Error> for LoadError {
    fn from(error: io::Error) -> Self {
        Self::Io(error)
    }
}

impl From<exif::Error> for LoadError {
    fn from(error: exif::Error) -> Self {
        Self::ExifParser(error)
    }
}

impl From<io::Error> for ConversionError {
    fn from(error: io::Error) -> Self {
        Self::Io(error)
    }
}

impl From<ImageError> for ConversionError {
    fn from(error: ImageError) -> Self {
        Self::ImageError(error)
    }
}