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use types::{MultiPoint, Point, LineString, MultiLineString, MultiPolygon, Polygon, Geometry, GeometryCollection};
use postgis;
use postgis::ewkb::{GeometryT, GeometryCollectionT};

/// Creates geometry from a PostGIS type.
///
/// Note that PostGIS databases can store data under any spatial
/// reference system - not just WGS84. No attempt is made to convert
/// data between reference systems.
pub trait FromPostgis<T> {
    fn from_postgis(T) -> Self;
}

impl<'a, T> FromPostgis<&'a T> for Point<f64> where T: postgis::Point {
    fn from_postgis(pt: &'a T) -> Self {
        Point::new(pt.x(), pt.y())
    }
}
impl<'a, T> FromPostgis<&'a T> for LineString<f64> where T: postgis::LineString<'a> {
    fn from_postgis(ls: &'a T) -> Self {
        let ret = ls.points()
            .map(|x| Point::from_postgis(x))
            .collect();
        LineString(ret)
    }
}
impl<'a, T> FromPostgis<&'a T> for Option<Polygon<f64>> where T: postgis::Polygon<'a> {
    /// This returns an `Option`, because it's possible for a PostGIS `Polygon`
    /// to contain zero rings, which makes for an invalid `geo::Polygon`.
    fn from_postgis(poly: &'a T) -> Self {
        let mut rings = poly.rings()
            .map(|x| LineString::from_postgis(x))
            .collect::<Vec<_>>();
        if rings.len() == 0 {
            return None;
        }
        let exterior = rings.remove(0);
        Some(Polygon {
            exterior,
            interiors: rings
        })
    }
}
impl<'a, T> FromPostgis<&'a T> for MultiPoint<f64> where T: postgis::MultiPoint<'a> {
    fn from_postgis(mp: &'a T) -> Self {
        let ret = mp.points()
            .map(|x| Point::from_postgis(x))
            .collect();
        MultiPoint(ret)
    }
}
impl<'a, T> FromPostgis<&'a T> for MultiLineString<f64> where T: postgis::MultiLineString<'a> {
    fn from_postgis(mp: &'a T) -> Self {
        let ret = mp.lines()
            .map(|x| LineString::from_postgis(x))
            .collect();
        MultiLineString(ret)
    }
}
impl<'a, T> FromPostgis<&'a T> for MultiPolygon<f64> where T: postgis::MultiPolygon<'a> {
    /// This implementation discards PostGIS polygons that don't convert
    /// (return `None` when `from_postgis()` is called on them).
    fn from_postgis(mp: &'a T) -> Self {
        let ret = mp.polygons()
            .filter_map(|x| Option::from_postgis(x))
            .collect();
        MultiPolygon(ret)
    }
}
impl<'a, T> FromPostgis<&'a GeometryCollectionT<T>> for GeometryCollection<f64> where T: postgis::Point + postgis::ewkb::EwkbRead {
    /// This implementation discards geometries that don't convert
    /// (return `None` when `from_postgis()` is called on them).
    fn from_postgis(gc: &'a GeometryCollectionT<T>) -> Self {
        let geoms = gc.geometries.iter()
            .filter_map(|x| Option::from_postgis(x))
            .collect();
        GeometryCollection(geoms)
    }
}
impl<'a, T> FromPostgis<&'a GeometryT<T>> for Option<Geometry<f64>> where T: postgis::Point + postgis::ewkb::EwkbRead {
    /// This returns an `Option`, because the supplied geometry
    /// could be an invalid `Polygon`.
    fn from_postgis(geo: &'a GeometryT<T>) -> Self {
        Some(match *geo {
            GeometryT::Point(ref p) => Geometry::Point(Point::from_postgis(p)),
            GeometryT::LineString(ref ls) => Geometry::LineString(LineString::from_postgis(ls)),
            GeometryT::Polygon(ref p) => match Option::from_postgis(p) {
                Some(p) => Geometry::Polygon(p),
                None => return None
            },
            GeometryT::MultiPoint(ref p) => Geometry::MultiPoint(MultiPoint::from_postgis(p)),
            GeometryT::MultiLineString(ref p) => Geometry::MultiLineString(MultiLineString::from_postgis(p)),
            GeometryT::MultiPolygon(ref p) => Geometry::MultiPolygon(MultiPolygon::from_postgis(p)),
            GeometryT::GeometryCollection(ref p) => Geometry::GeometryCollection(GeometryCollection::from_postgis(p))
        })
    }
}