//! This module contains functions that often are more convenient to use than the raw OpenSlide
//! wrappers
//!

use std::path::Path;
use std::collections::HashMap;
use std::fmt::{Display, Debug};
use std::cmp::PartialOrd;

use failure::{err_msg, Error};
use image::{RgbaImage};
use num::{Num, ToPrimitive, Unsigned, Integer};
use num::zero;

use ::{
    utils,
    bindings,
    properties,
};

/// A convenient OpenSlide object with the ordinary OpenSlide functions as methods
///
/// This wraps the bindings found in the bindings module, but has a more (in my opinion) convenient
/// API for rust. It also contains some other convenience methods.
#[derive(Clone)]
pub struct OpenSlide {
    osr: *const bindings::OpenSlideT,
    pub properties: properties::Properties,
}

impl Drop for OpenSlide {
    /// This method is called when the object in dropped, and tries to close the slide.
    fn drop(
        &mut self
    ) {
        bindings::close(self.osr);
    }
}

impl OpenSlide {
    /// This method tries to open the slide at the given filename location.
    ///
    /// This function can be expensive; avoid calling it unnecessarily. For example, a tile server
    /// should not create a new object on every tile request. Instead, it should maintain a cache
    /// of OpenSlide objects and reuse them when possible.
    pub fn new(
        filename: &Path
    ) -> Result<OpenSlide, Error> {
        if !filename.exists() {
            return Err(err_msg(format!("Error: Nonexisting path: {}", filename.display())));
        }

        let osr = bindings::open(filename.to_str().ok_or(err_msg("Error: Path to &str"))?)?;

        let mut property_map = HashMap::<String, String>::new();
        for name in bindings::get_property_names(osr)? {
            property_map.insert(name.clone(), bindings::get_property_value(osr, &name)?);
        }
        let properties = properties::Properties::new(&property_map);

        Ok(OpenSlide {
            osr: osr,
            properties: properties,
        })
    }

    /// Get the number of levels in the whole slide image.
    pub fn get_level_count(
        &self
    ) -> Result<u32, Error> {
        let num_levels = bindings::get_level_count(self.osr)?;

        if num_levels < -1 {
            Err(err_msg(format!("Error: Number of levels is {}, this is an unknown error from OpenSlide. \
                                 OpenSlide returns -1 if an error occured. \
                                 See OpenSlide C API documentation.", num_levels)))
        } else if num_levels == -1 {
            Err(err_msg("Error: Number of levels is -1, this is a known error from OpenSlide. \
                         OpenSlide returns -1 if an error occured. \
                         See OpenSlide C API documentation."))
        } else {
            Ok(num_levels as u32)
        }
    }

    /// Get the dimensions of level 0 (the largest level).
    ///
    /// This method returns the (width, height) number of pixels of the level 0 whole slide image.
    ///
    /// This is the same as calling get_level_dimensions(level) with level=0.
    pub fn get_level0_dimensions(
        &self
    ) -> Result<(u64, u64), Error> {
        let (width, height) = bindings::get_level0_dimensions(self.osr)?;

        if width < -1 {
            return Err(err_msg(format!("Error: Width is {}, this is an unknown error from OpenSlide. \
                                        OpenSlide returns -1 if an error occured. \
                                        See OpenSlide C API documentation.", width)))
        } else if width == -1 {
            return Err(err_msg("Error: Width is -1, this is a known error from OpenSlide. \
                                OpenSlide returns -1 if an error occured. \
                                See OpenSlide C API documentation."))
        }

        if height < -1 {
            return Err(err_msg(format!("Error: Height is {}, this is an unknown error from OpenSlide. \
                                        OpenSlide returns -1 if an error occured. \
                                        See OpenSlide C API documentation.", width)))
        } else if height == -1 {
            return Err(err_msg("Error: Height is -1, this is a known error from OpenSlide. \
                                OpenSlide returns -1 if an error occured. \
                                See OpenSlide C API documentation."))
        }

        Ok((width as u64, height as u64))
    }

    /// Get the dimensions of level 0 (the largest level).
    ///
    /// This method returns the (width, height) number of pixels of the whole slide image at the
    /// specified level. Returns an error if the level is invalid
    pub fn get_level_dimensions<T: Integer + ToPrimitive + Debug + Display + Clone + Copy>(
        &self,
        level: T,
    ) -> Result<(u64, u64), Error> {

        let max_num_levels = self.get_level_count()?;
        if level.to_u32().ok_or(err_msg("Conversion to primitive error"))? > max_num_levels {
            return Err(err_msg(format!("Error: Specified level {} is larger than the max slide level {}",
                                       level, max_num_levels)));
        }

        let (width, height) = bindings::get_level_dimensions(self.osr, level.to_i32().ok_or(err_msg("Conversion to primitive error"))?)?;

        if width < -1 {
            return Err(err_msg(format!("Error: Width is {}, this is an unknown error from OpenSlide. \
                                        OpenSlide returns -1 if an error occured. \
                                        See OpenSlide C API documentation.", width)))
        } else if width == -1 {
            return Err(err_msg("Error: Width is -1, this is a known error from openslide. \
                                OpenSlide returns -1 if an error occured. \
                                See OpenSlide C API documentation."))
        }

        if height < -1 {
            return Err(err_msg(format!("Error: Height is {}, this is an unknown error from OpenSlide. \
                                        OpenSlide returns -1 if an error occured. \
                                        See OpenSlide C API documentation.", width)))
        } else if height == -1 {
            return Err(err_msg("Error: Height is -1, this is a known error from openslide. \
                                OpenSlide returns -1 if an error occured. \
                                See OpenSlide C API documentation."))
        }

        Ok((width as u64, height as u64))
    }

    /// Get the downsampling factor of a given level.
    pub fn get_level_downsample<T: Integer + Unsigned + ToPrimitive + Debug + Display + Clone + Copy>(
        &self,
        level: T,
    ) -> Result<f64, Error> {

        let max_num_levels = self.get_level_count()?;
        if level.to_u32().ok_or(err_msg("Conversion to primitive error"))? > max_num_levels {
            return Err(err_msg(format!("Error: Specified level {} is larger than the max slide level {}",
                                       level, max_num_levels)));
        }

        let downsample_factor = bindings::get_level_downsample(self.osr, level.to_i32().ok_or(err_msg("Conversion to primitive error"))?)?;

        if downsample_factor < 0.0 {
            return Err(err_msg(format!("Error: Downsample factor is {}, this is an error from \
                                        OpenSlide. OpenSlide returns -1.0 if an error occured. \
                                        See OpenSlide C API documentation.", downsample_factor)))
        }

        Ok(downsample_factor)
    }

    /// Get the best level to use for displaying the given downsample factor.
    pub fn get_best_level_for_downsample<T: Num + ToPrimitive + PartialOrd + Debug + Display + Clone + Copy>(
        &self,
        downsample_factor: T,
    ) -> Result<u32, Error> {

        if downsample_factor < zero() {
            return Err(err_msg(format!("Error: Only non-negative downsample factor is allowed. \
                                        You specified {}. ", downsample_factor)))
        }

        let level = bindings::get_best_level_for_downsample(self.osr, downsample_factor.to_f64().ok_or(err_msg("Conversion to primitive error"))?)?;

        if level < -1 {
            Err(err_msg(format!("Error: Returned level is {}, this is an unknown error from OpenSlide. \
                                 OpenSlide returns -1 if an error occured. \
                                 See OpenSlide C API documentation.", level)))
        } else if level == -1 {
            Err(err_msg("Error: Returned level is -1, this is a known error from openslide. \
                         OpenSlide returns -1 if an error occured. \
                         See OpenSlide C API documentation."))
        } else {
            Ok(level as u32)
        }
    }

    /// Return (new_height, new_width) where
    ///
    /// new_height = min(height, max_height)
    /// new_width = min(width, max_width)
    ///
    /// and max_{height, width} are computed based on the top left corner coordinates and the
    /// dimensions of the image.
    fn get_feasible_dimensions<T: Integer + Unsigned + ToPrimitive + Debug + Display + Clone + Copy>(
        &self,
        top_left_lvl0_row: T,
        top_left_lvl0_col: T,
        level: T,
        height: T,
        width: T,
    ) -> Result<(u64, u64), Error> {
        let (max_width, max_height) = self.get_level_dimensions(level)?;
        let downsample_factor = self.get_level_downsample(level)?;

        let tl_row_this_lvl = top_left_lvl0_row.to_f64().ok_or(err_msg("Conversion to primitive error"))? /
                              downsample_factor;
        let tl_col_this_lvl = top_left_lvl0_col.to_f64().ok_or(err_msg("Conversion to primitive error"))? /
                              downsample_factor;

        let new_height = height.to_u64()
                               .ok_or(err_msg("conversion to primitive error"))?
                               .min(max_height - tl_row_this_lvl.round() as u64);
        let new_width = width.to_u64()
                             .ok_or(err_msg("Conversion to primitive error"))?
                             .min(max_width - tl_col_this_lvl.round() as u64);

        if new_height < height.to_u64().ok_or(err_msg("conversion to primitive error"))? {
            println!("WARNING: Requested region height is changed from {} to {} in order to fit",
                     height, new_height);
        }
        if new_width < width.to_u64().ok_or(err_msg("conversion to primitive error"))? {
            println!("WARNING: Requested region width is changed from {} to {} in order to fit",
                     width, new_width);
        }

        if new_height > max_height {
            return Err(err_msg(format!("Requested height {} exceeds maximum {}", height, max_height)))
        }

        if new_width > max_width {
            return Err(err_msg(format!("Requested width {} exceeds maximum {}", width, max_width)))
        }

        Ok((new_height, new_width))
    }

    /// Copy pre-multiplied ARGB data from a whole slide image.
    ///
    /// This function reads and decompresses a region of a whole slide image into an RGBA image
    ///
    /// Args:
    ///     top_left_lvl0_row: Row coordinate (increasing downwards) of top left pixel position
    ///     top_left_lvl0_col: Column coordinate (increasing to the right) of top left pixel
    ///                        position
    ///     level: At which level to grab the region from
    ///     height: Height in pixels of the outputted region
    ///     width: Width in pixels of the outputted region
    pub fn read_region<T: Integer + Unsigned + ToPrimitive + Debug + Display + Clone + Copy>(
        &self,
        top_left_lvl0_row: T,
        top_left_lvl0_col: T,
        level: T,
        height: T,
        width: T,
    ) -> Result<RgbaImage, Error> {

        let (height, width) = self.get_feasible_dimensions(top_left_lvl0_row,
                                                           top_left_lvl0_col,
                                                           level,
                                                           height,
                                                           width)?;

        let buffer = bindings::read_region(self.osr,
                                           top_left_lvl0_col.to_i64().ok_or(err_msg("Conversion to primitive error"))?,
                                           top_left_lvl0_row.to_i64().ok_or(err_msg("Conversion to primitive error"))?,
                                           level.to_i32().ok_or(err_msg("Conversion to primitive error"))?,
                                           width.to_i64().ok_or(err_msg("Conversion to primitive error"))?,
                                           height.to_i64().ok_or(err_msg("Conversion to primitive error"))?)?;
        let word_repr = utils::WordRepresentation::BigEndian;
        utils::decode_buffer(&buffer, height, width, word_repr)
    }

    /// Get a dictionary of properties associated with the current slide
    ///
    /// There are some standard properties to every slide, but also a lot of vendor-specific
    /// properties. This method returns a HashMap with all key-value pairs of the properties
    /// associated with the slide.
    pub fn get_properties(
        &self
    ) -> Result<HashMap<String, String>, Error> {
        let mut properties = HashMap::<String, String>::new();
        for name in bindings::get_property_names(self.osr)? {
            properties.insert(name.clone(), bindings::get_property_value(self.osr, &name)?);
        }
        Ok(properties)
    }
}