use crate::{Coordinate, CoordinateType, Line, Point, Triangle};
use std::iter::FromIterator;
use std::ops::{Index, IndexMut};

/// An ordered collection of two or more
/// [`Coordinate`s](struct.Coordinate.html), representing a
/// path between locations.
///
/// # Semantics
///
/// A `LineString` is _closed_ if it is empty, or if the
/// first and last coordinates are the same. The _boundary_
/// of a `LineString` is empty if closed, and otherwise the
/// end points. The _interior_ is the (infinite) set of all
/// points along the linestring _not including_ the
/// boundary. A `LineString` is _simple_ if it does not
/// intersect except possibly at the first and last
/// coordinates. A simple and closed `LineString` is a
/// `LinearRing` as defined in the OGC-SFA (but is not a
/// separate type here).
///
/// # Validity
///
/// A `LineString` is valid if it is either empty or
/// contains 2 or more coordinates. Further, a closed
/// `LineString` must not self intersect. Note that the
/// validity is not enforced, and the operations and
/// predicates are undefined on invalid linestrings.
///
/// # Examples
///
/// Create a `LineString` by calling it directly:
///
/// ```
/// use geo_types::{Coordinate, LineString};
///
/// let line_string = LineString(vec![
///     Coordinate { x: 0., y: 0. },
///     Coordinate { x: 10., y: 0. },
/// ]);
/// ```
///
/// Converting a `Vec` of `Coordinate`-like things:
///
/// ```
/// use geo_types::LineString;
///
/// let line_string: LineString<f32> = vec![(0., 0.), (10., 0.)].into();
/// ```
///
/// ```
/// use geo_types::LineString;
///
/// let line_string: LineString<f64> = vec![[0., 0.], [10., 0.]].into();
/// ```
//
/// Or `collect`ing from a `Coordinate` iterator
///
/// ```
/// use geo_types::{Coordinate, LineString};
///
/// let mut coords_iter =
///     vec![Coordinate { x: 0., y: 0. }, Coordinate { x: 10., y: 0. }].into_iter();
///
/// let line_string: LineString<f32> = coords_iter.collect();
/// ```
///
/// You can iterate over the coordinates in the `LineString`:
///
/// ```
/// use geo_types::{Coordinate, LineString};
///
/// let line_string = LineString(vec![
///     Coordinate { x: 0., y: 0. },
///     Coordinate { x: 10., y: 0. },
/// ]);
///
/// for coord in line_string {
///     println!("Coordinate x = {}, y = {}", coord.x, coord.y);
/// }
/// ```
///
/// You can also iterate over the coordinates in the `LineString` as `Point`s:
///
/// ```
/// use geo_types::{Coordinate, LineString};
///
/// let line_string = LineString(vec![
///     Coordinate { x: 0., y: 0. },
///     Coordinate { x: 10., y: 0. },
/// ]);
///
/// for point in line_string.points_iter() {
///     println!("Point x = {}, y = {}", point.x(), point.y());
/// }
/// ```

#[derive(Eq, PartialEq, Clone, Debug, Hash)]
#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
pub struct LineString<T>(pub Vec<Coordinate<T>>)
where
    T: CoordinateType;

/// A `Point` iterator returned by the `points_iter` method
pub struct PointsIter<'a, T: CoordinateType + 'a>(::std::slice::Iter<'a, Coordinate<T>>);

impl<'a, T: CoordinateType> Iterator for PointsIter<'a, T> {
    type Item = Point<T>;

    fn next(&mut self) -> Option<Self::Item> {
        self.0.next().map(|c| Point(*c))
    }
}

impl<'a, T: CoordinateType> DoubleEndedIterator for PointsIter<'a, T> {
    fn next_back(&mut self) -> Option<Self::Item> {
        self.0.next_back().map(|c| Point(*c))
    }
}

impl<T: CoordinateType> LineString<T> {
    /// Return an iterator yielding the coordinates of a `LineString` as `Point`s
    pub fn points_iter(&self) -> PointsIter<T> {
        PointsIter(self.0.iter())
    }

    /// Return the coordinates of a `LineString` as a `Vec` of `Point`s
    pub fn into_points(self) -> Vec<Point<T>> {
        self.0.into_iter().map(Point).collect()
    }

    /// Return an iterator yielding one `Line` for each line segment
    /// in the `LineString`.
    ///
    /// # Examples
    ///
    /// ```
    /// use geo_types::{Coordinate, Line, LineString};
    ///
    /// let mut coords = vec![(0., 0.), (5., 0.), (7., 9.)];
    /// let line_string: LineString<f32> = coords.into_iter().collect();
    ///
    /// let mut lines = line_string.lines();
    /// assert_eq!(
    ///     Some(Line::new(
    ///         Coordinate { x: 0., y: 0. },
    ///         Coordinate { x: 5., y: 0. }
    ///     )),
    ///     lines.next()
    /// );
    /// assert_eq!(
    ///     Some(Line::new(
    ///         Coordinate { x: 5., y: 0. },
    ///         Coordinate { x: 7., y: 9. }
    ///     )),
    ///     lines.next()
    /// );
    /// assert!(lines.next().is_none());
    /// ```
    pub fn lines<'a>(&'a self) -> impl ExactSizeIterator + Iterator<Item = Line<T>> + 'a {
        self.0.windows(2).map(|w| {
            // slice::windows(N) is guaranteed to yield a slice with exactly N elements
            unsafe { Line::new(*w.get_unchecked(0), *w.get_unchecked(1)) }
        })
    }

    /// An iterator which yields the coordinates of a `LineString` as `Triangle`s
    pub fn triangles<'a>(&'a self) -> impl ExactSizeIterator + Iterator<Item = Triangle<T>> + 'a {
        self.0.windows(3).map(|w| {
            // slice::windows(N) is guaranteed to yield a slice with exactly N elements
            unsafe {
                Triangle(
                    *w.get_unchecked(0),
                    *w.get_unchecked(1),
                    *w.get_unchecked(2),
                )
            }
        })
    }

    /// Close the `LineString`. Specifically, if the `LineString` has at least one coordinate, and
    /// the value of the first coordinate does not equal the value of the last coordinate, then a
    /// new coordinate is added to the end with the value of the first coordinate.
    pub fn close(&mut self) {
        if !self.is_closed() {
            // by definition, we treat empty LineString's as closed.
            debug_assert!(self.0.len() > 0);
            self.0.push(self.0[0]);
        }
    }

    /// Return the number of coordinates in the `LineString`.
    ///
    /// # Examples
    ///
    /// ```
    /// use geo_types::LineString;
    ///
    /// let mut coords = vec![(0., 0.), (5., 0.), (7., 9.)];
    /// let line_string: LineString<f32> = coords.into_iter().collect();
    /// assert_eq!(3, line_string.num_coords());
    /// ```
    pub fn num_coords(&self) -> usize {
        self.0.len()
    }

    /// Checks if the linestring is closed; i.e. it is
    /// either empty or, the first and last points are the
    /// same.
    ///
    /// # Examples
    ///
    /// ```
    /// use geo_types::LineString;
    ///
    /// let mut coords = vec![(0., 0.), (5., 0.), (0., 0.)];
    /// let line_string: LineString<f32> = coords.into_iter().collect();
    /// assert!(line_string.is_closed());
    /// ```
    ///
    /// Note that we diverge from some libraries (JTS et al), which have a LinearRing type,
    /// separate from LineString. Those libraries treat an empty LinearRing as closed, by
    /// definition, while treating an empty LineString as open. Since we don't have a separate
    /// LinearRing type, and use a LineString in its place, we adopt the JTS LinearRing `is_closed`
    /// behavior in all places, that is, we consider an empty LineString as closed.
    ///
    /// This is expected when used in the context of a Polygon.exterior and elswhere; And there
    /// seems to be no reason to maintain the separate behavior for LineStrings used in
    /// non-LinearRing contexts.
    pub fn is_closed(&self) -> bool {
        self.0.first() == self.0.last()
    }
}

/// Turn a `Vec` of `Point`-like objects into a `LineString`.
impl<T: CoordinateType, IC: Into<Coordinate<T>>> From<Vec<IC>> for LineString<T> {
    fn from(v: Vec<IC>) -> Self {
        LineString(v.into_iter().map(|c| c.into()).collect())
    }
}

/// Turn an iterator of `Point`-like objects into a `LineString`.
impl<T: CoordinateType, IC: Into<Coordinate<T>>> FromIterator<IC> for LineString<T> {
    fn from_iter<I: IntoIterator<Item = IC>>(iter: I) -> Self {
        LineString(iter.into_iter().map(|c| c.into()).collect())
    }
}

/// Iterate over all the [Coordinate](struct.Coordinates.html)s in this `LineString`.
impl<T: CoordinateType> IntoIterator for LineString<T> {
    type Item = Coordinate<T>;
    type IntoIter = ::std::vec::IntoIter<Coordinate<T>>;

    fn into_iter(self) -> Self::IntoIter {
        self.0.into_iter()
    }
}

/// Mutably iterate over all the [Coordinate](struct.Coordinates.html)s in this `LineString`.
impl<'a, T: CoordinateType> IntoIterator for &'a mut LineString<T> {
    type Item = &'a mut Coordinate<T>;
    type IntoIter = ::std::slice::IterMut<'a, Coordinate<T>>;

    fn into_iter(self) -> ::std::slice::IterMut<'a, Coordinate<T>> {
        self.0.iter_mut()
    }
}

impl<T: CoordinateType> Index<usize> for LineString<T> {
    type Output = Coordinate<T>;

    fn index(&self, index: usize) -> &Coordinate<T> {
        self.0.index(index)
    }
}

impl<T: CoordinateType> IndexMut<usize> for LineString<T> {
    fn index_mut(&mut self, index: usize) -> &mut Coordinate<T> {
        self.0.index_mut(index)
    }
}

#[cfg(feature = "rstar")]
impl<T> ::rstar::RTreeObject for LineString<T>
where
    T: ::num_traits::Float + ::rstar::RTreeNum,
{
    type Envelope = ::rstar::AABB<Point<T>>;

    fn envelope(&self) -> Self::Envelope {
        use num_traits::Bounded;
        let bounding_rect = crate::private_utils::line_string_bounding_rect(self);
        match bounding_rect {
            None => ::rstar::AABB::from_corners(
                Point::new(Bounded::min_value(), Bounded::min_value()),
                Point::new(Bounded::max_value(), Bounded::max_value()),
            ),
            Some(b) => ::rstar::AABB::from_corners(
                Point::new(b.min().x, b.min().y),
                Point::new(b.max().x, b.max().y),
            ),
        }
    }
}

#[cfg(feature = "rstar")]
impl<T> ::rstar::PointDistance for LineString<T>
where
    T: ::num_traits::Float + ::rstar::RTreeNum,
{
    fn distance_2(&self, point: &Point<T>) -> T {
        let d = crate::private_utils::point_line_string_euclidean_distance(*point, self);
        if d == T::zero() {
            d
        } else {
            d.powi(2)
        }
    }
}