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use crate::{polygon, CoordNum, Coordinate, Line, Polygon};

/// A bounded 2D area whose three vertices are defined by
/// `Coordinate`s. The semantics and validity are that of
/// the equivalent [`Polygon`]; in addition, the three
/// vertices must not be collinear and they must be distinct.
#[derive(Copy, Clone, Debug, Hash, Eq, PartialEq)]
#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
pub struct Triangle<T: CoordNum>(pub Coordinate<T>, pub Coordinate<T>, pub Coordinate<T>);

impl<T: CoordNum> Triangle<T> {
    pub fn to_array(&self) -> [Coordinate<T>; 3] {
        [self.0, self.1, self.2]
    }

    pub fn to_lines(&self) -> [Line<T>; 3] {
        [
            Line::new(self.0, self.1),
            Line::new(self.1, self.2),
            Line::new(self.2, self.0),
        ]
    }

    /// Create a `Polygon` from the `Triangle`.
    ///
    /// # Examples
    ///
    /// ```rust
    /// use geo_types::{Coordinate, Triangle, polygon};
    ///
    /// let triangle = Triangle(
    ///     Coordinate { x: 0., y: 0. },
    ///     Coordinate { x: 10., y: 20. },
    ///     Coordinate { x: 20., y: -10. },
    /// );
    ///
    /// assert_eq!(
    ///     triangle.to_polygon(),
    ///     polygon![
    ///         (x: 0., y: 0.),
    ///         (x: 10., y: 20.),
    ///         (x: 20., y: -10.),
    ///         (x: 0., y: 0.),
    ///     ],
    /// );
    /// ```
    pub fn to_polygon(self) -> Polygon<T> {
        polygon![self.0, self.1, self.2, self.0]
    }
}

impl<IC: Into<Coordinate<T>> + Copy, T: CoordNum> From<[IC; 3]> for Triangle<T> {
    fn from(array: [IC; 3]) -> Triangle<T> {
        Triangle(array[0].into(), array[1].into(), array[2].into())
    }
}