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use num_traits::{Float};
use std::str::FromStr;
use std::num::{ParseFloatError};
use slice_of_array::prelude::*;

#[derive(Debug)]
pub struct CubeLut <T: Float> {
    pub title: String,
    pub kind: LutKind,
    pub domain_min: [T;3],
    pub domain_max: [T;3],
    pub size: usize,
    pub data: Vec<[T;3]>
}

#[derive(Debug, PartialEq)]
pub enum LutKind {
    One,
    Three,
}

#[derive(Debug, PartialEq)]
pub enum LutError {
    SizeLine,
    Title,
    Size(usize),
    DomainMin(usize),
    DomainMax(usize),
    DataRed(usize),
    DataGreen(usize),
    DataBlue(usize),
    DataLine(usize),
}

impl <T: Float + FromStr<Err=ParseFloatError>> CubeLut<T> {

    pub fn flatten_data(&self) -> &[T] {
        self.data.flat()
    }

    pub fn from_str(txt:&str) -> Result<Self, LutError> {
        let mut title:Option<String> = None;
        let mut kind:Option<LutKind> = None;
        let mut domain_min = [T::zero();3];
        let mut domain_max = [T::one();3];
        let mut size:usize = 0;

        //non-empty and non-comment lines 
        let lines = txt
            .lines()
            .filter(|line| {
                match line.chars().next() {
                    None => false,
                    Some('#') => false,
                    _ => true
                }
            });

        let mut data:Vec<[T;3]> = Vec::with_capacity(lines.clone().count());

        for (line_number, line) in lines.enumerate() {
            let mut parts = line.split_whitespace();
            let first = parts.next();
            
            let mut get_size = |line_number| -> Result<usize, LutError> {
                parts.next().and_then(|value| value.parse::<usize>().ok()).ok_or(LutError::Size(line_number))
            };

            match first {
                Some("TITLE") => {
                    title = Some(parts.collect::<Vec<&str>>().join(" "));
                },
                Some("DOMAIN_MIN") => {
                    match parse_domain(parts) {
                        None =>  return Err(LutError::DomainMin(line_number)),
                        Some(values) => domain_min.copy_from_slice(&values)
                    }
                },
                Some("DOMAIN_MAX") => {
                    match parse_domain(parts) {
                        None =>  return Err(LutError::DomainMax(line_number)),
                        Some(values) => domain_max.copy_from_slice(&values)
                    }
                },
                Some("LUT_1D_SIZE") => {
                    kind = Some(LutKind::One);
                    size = get_size(line_number)?;
                }
                Some("LUT_3D_SIZE") => {
                    kind = Some(LutKind::Three);
                    size = get_size(line_number)?;
                }
                _ => { 
                    match (first, parts.next(), parts.next()) {
                        (Some(r), Some(g), Some(b)) => {
                            let r = r.parse::<T>().map_err(|_| LutError::DataRed(line_number))?;
                            let g = g.parse::<T>().map_err(|_| LutError::DataGreen(line_number))?;
                            let b = b.parse::<T>().map_err(|_| LutError::DataBlue(line_number))?;
                            data.push([r, g, b]);
                        },
                        _ => {
                            return Err(LutError::DataLine(line_number));
                        }
                    }
                }
            }
        }


        if size == 0 {
            return Err(LutError::SizeLine)
        }

        let kind = kind.unwrap(); //there can't be a valid kind unless there's a valid size

        let title = title.ok_or(LutError::Title)?;


        Ok(Self {
            title,
            kind,
            domain_min,
            domain_max,
            size,
            data
        })
    }
}


fn parse_domain<'a, N: Float + FromStr<Err=ParseFloatError>, T: Iterator<Item=&'a str>>(parts:T) -> Option<Vec<N>> {
    let values = 
        parts
        .map(|value| value.parse::<N>())
        .collect::<Result<Vec<N>, std::num::ParseFloatError>>();

    match values {
        Ok(values) => {
            if values.len() < 3 {
                None 
            } else {
                Some(values)
            }
        },
        Err(_) => {
            None 
        }
    }
}