use crate::{comparison::BetterThanOperator, fitness::FitnessFunction};

#[derive(Clone, Debug)]
pub struct Population<TChromosome> {
    population: Vec<TChromosome>
}

#[derive(Clone, Debug)]
pub struct EvaluatedChromosome<TChromosome, TResult> {
    pub chromosome: TChromosome,
    pub evaluation: TResult,
}

#[derive(Clone, Debug)]
pub struct EvaluatedPopulation<TChromosome, TResult> {
    pub population: Vec<EvaluatedChromosome<TChromosome, TResult>>
}

impl<TChromosome> Population<TChromosome> {
    pub fn empty() -> Self {
        Self {
            population: vec![]
        }
    }

    pub fn from_vec(vec: Vec<TChromosome>) -> Self {
        Self {
            population: vec
        }
    }

    pub fn from_iterator(iter: impl Iterator<Item = TChromosome>) -> Self {
        Self::from_vec(iter.collect())
    }

    pub fn evaluate<T: FitnessFunction<In = TChromosome>>(self, func: &T) -> Result<EvaluatedPopulation<TChromosome, T::Out>, T::Err> {
        EvaluatedPopulation::evaluate(
            self.population,
            func
        )
    }

    pub fn join(&mut self, mut offsprings: Population<TChromosome>) {
        self.population.append(&mut offsprings.population);
    }

    pub fn into_iter(self) -> impl Iterator<Item = TChromosome> {
        self.population.into_iter()
    }

    pub fn iter(&self) -> impl Iterator<Item = &TChromosome> {
        self.population.iter()
    }

    pub fn iter_mut(&mut self) -> impl Iterator<Item = &mut TChromosome> {
        self.population.iter_mut()
    }
}

impl<TInput, TResult> EvaluatedChromosome<TInput, TResult> {
    pub fn deconstruct(self) -> (TInput, TResult) {
        (self.chromosome, self.evaluation)
    }
}

impl<TChromosome, TResult> EvaluatedPopulation<TChromosome, TResult> {
    pub fn empty() -> Self {
        Self {
            population: vec![]
        }
    }

    pub fn new() -> Self {
        Self {
            population: vec![]
        }
    }

    pub fn evaluate<T: FitnessFunction<In = TChromosome, Out = TResult>>(chromosomes: Vec<TChromosome>, func: &T) -> Result<Self, T::Err> {
        func.fit_population(chromosomes)
            .map(|population| Self::from_vec(population))
    }

    pub fn from_vec(vec: Vec<EvaluatedChromosome<TChromosome, TResult>>) -> Self {
        Self {
            population: vec
        }
    }

    pub fn best_candidate(&self, better_than: &impl BetterThanOperator<TResult>) -> &EvaluatedChromosome<TChromosome, TResult> {
        let mut best_so_far = &self.population[0];
        for individual in self.population.iter().skip(1) {
            if better_than.better_than(&individual.evaluation, &best_so_far.evaluation) {
                best_so_far = individual;
            }
        }

        best_so_far
    }

    pub fn split_at(self, len: usize) -> (Self, Self) {
        let mut left = self.population;
        let right = left.split_off(len);

        (
            Self::from_vec(left),
            Self::from_vec(right),
        )
    }

    pub fn add(&mut self, c: EvaluatedChromosome<TChromosome, TResult>) {
        self.population.push(c)
    }

    pub fn deconstruct(self) -> Vec<EvaluatedChromosome<TChromosome, TResult>> {
        self.population
    }

    pub fn nonevaluated(self) -> Population<TChromosome> {
        Population::from_vec(self.deconstruct()
                             .into_iter()
                             .map(|individual| individual.chromosome)
                             .collect::<Vec<_>>())
    }

    pub fn join(&mut self, mut offsprings: EvaluatedPopulation<TChromosome, TResult>) {
        self.population.append(&mut offsprings.population);
    }

    pub fn iter(&self) -> impl Iterator<Item = &EvaluatedChromosome<TChromosome, TResult>> {
        self.population.iter()
    }

    pub fn iter_mut(&mut self) -> impl Iterator<Item = &mut EvaluatedChromosome<TChromosome, TResult>> {
        self.population.iter_mut()
    }

}

impl<TChromosome, TResult: Copy> EvaluatedPopulation<TChromosome, TResult> {
    pub fn evaluations_vec(&self) -> Vec<TResult> {
        self.population
            .iter()
            .map(|individual| individual.evaluation)
            .collect()
    }
}