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use std::f64;

static R: f64 = 6372.8;

#[derive(Copy, Clone, Debug)]
pub struct Point {
    pub lat: f64,
    pub lon: f64,
}

pub struct Measure {
    pub distance: f64,
}

#[derive(Default, Debug)]
pub struct Matrix {
    pub distances: Vec<f64>,
}

impl Matrix {
    pub fn add_distance(&mut self, measure: Measure) {
        self.distances.push(measure.distance);
    }

    pub fn add_distances(&mut self, distances: Vec<f64>) {
        for distance in distances {
            self.distances.push(distance);
        }
    }
}

pub fn haversine(origin: Point, destination: Point) -> Measure {
    let diff = origin.lon - destination.lon;
    let ori_lon = diff.to_radians();
    let ori_lat = origin.lat.to_radians();
    let dest_lat = destination.lat.to_radians();
    let dz: f64 = ori_lat.sin() - dest_lat.sin();
    let dx: f64 = ori_lon.cos() * ori_lat.cos() - dest_lat.cos();
    let dy: f64 = ori_lon.sin() * ori_lat.cos();
    let dist: f64 = ((dx * dx + dy * dy + dz * dz).sqrt() / 2.0).asin() * 2.0 * R;
    Measure { distance: dist }
}

pub fn one_to_many(origin: Point, destinations: Vec<Point>) -> Matrix {
    let mut matrix: Matrix = Matrix::default();
    let origin_distance: Measure = haversine(origin, origin);
    matrix.add_distance(origin_distance);
    for destination in destinations {
        let measure = haversine(origin, destination);
        matrix.add_distance(measure);
    }
    matrix
}

fn one_to_many_with_origin(origin: Point, destinations: Vec<Point>) -> Matrix {
    let mut matrix: Matrix = Matrix::default();
    for destination in destinations {
        let measure = haversine(origin, destination);
        matrix.add_distance(measure);
    }
    matrix
}

pub fn many_to_many(destinations: Vec<Point>) -> Matrix {
    let mut matrix: Matrix = Matrix::default();
    destinations.iter().for_each(|origin| {
        let sub_matrix = one_to_many_with_origin(*origin, destinations.clone());
        matrix.add_distances(sub_matrix.distances);
    });
    matrix
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn it_works_for_one_point() {
        let origin: Point = Point {
            lat: 36.12,
            lon: -86.67,
        };
        let destination: Point = Point {
            lat: 33.94,
            lon: -118.4,
        };
        let measure: Measure = haversine(origin, destination);
        assert_eq!(measure.distance, 2887.2599506071106);
    }

    #[test]
    fn it_works_for_one_point_again() {
        let origin: Point = Point {
            lat: 39.472978,
            lon: -0.375203,
        };
        let destination: Point = Point {
            lat: 38.967161,
            lon: -0.184759,
        };

        let measure = haversine(origin, destination);
        assert_eq!(measure.distance, 58.604658305034434);
    }

    #[test]
    fn it_works_for_one_point_to_many() {
        let origin: Point = Point {
            lat: 39.472978,
            lon: -0.375203,
        };
        let mut destinations: Vec<Point> = Vec::new();
        destinations.push(Point {
            lat: 38.967161,
            lon: -0.184759,
        });
        destinations.push(Point {
            lat: 33.94,
            lon: -118.4,
        });

        let matrix = one_to_many(origin, destinations);
        assert_eq!(
            matrix.distances,
            [0.0, 58.604658305034434, 9665.831848220572]
        );
    }

    #[test]
    fn it_works_for_many_to_many() {
        let mut destinations: Vec<Point> = Vec::new();
        destinations.push(Point {
            lat: 39.472978,
            lon: -0.375203,
        });

        destinations.push(Point {
            lat: 38.967161,
            lon: -0.184759,
        });
        destinations.push(Point {
            lat: 33.94,
            lon: -118.4,
        });

        let matrix = many_to_many(destinations);
        assert_eq!(
            matrix.distances,
            [
                0.0,
                58.604658305034434,
                9665.831848220572,
                58.60465830503454,
                0.0,
                9716.147344492676,
                9665.831848220572,
                9716.147344492676,
                0.0
            ]
        );
    }
}