//! Path building utilities.
//!
//! ## `PathBuilder` or `SvgPathBuilder`
//!
//! Path can be built via either of two abstractions:
//!
//! - [PathBuilder](trait.PathBuilder.html) is a simple and efficient interface which
//!   does not deal with any ambiguous cases.
//! - [SvgPathBuilder](trait.SvgPathBuilder.html) is a higher-level interface that
//!   follows SVG's specification, removing the the burden of dealing with special cases
//!   from the user at a run-time cost.
//!
//! `SvgPathBuilder` may be a better choice when interactive with SVG, or dealing with arbitrary
//! input. `PathBuilder`. `PathBuilder` is probably a more useful trait to implement when creating
//! a new path data structure since all `PathBuilder` implementations automatically get an
//! `SvgPathBuilder` adapter (see the `with_svg` method). It may also make sense to use the
//! `PathBuilder` API when following a specification that behaves like SVG paths or when no
//! performance can be traded for convenience.
//!
//! ## Examples
//!
//! The following example shows how to create a simple path using the
//! [PathBuilder](trait.PathBuilder.html) interface.
//!
//! ```
//! use lyon_path::{Path, geom::point};
//!
//! let mut builder = Path::builder();
//!
//! // All sub-paths *must* have be contained in a being/end pair.
//! builder.begin(point(0.0, 0.0));
//! builder.line_to(point(1.0, 0.0));
//! builder.quadratic_bezier_to(point(2.0, 0.0), point(2.0, 1.0));
//! builder.end(false);
//!
//! builder.begin(point(10.0, 0.0));
//! builder.cubic_bezier_to(point(12.0, 2.0), point(11.0, 2.0), point(5.0, 0.0));
//! builder.close(); // close() is equivalent to end(true).
//!
//! let path = builder.build();
//! ```
//!
//! The same path can be built using the `SvgPathBuilder` API:
//!
//! ```
//! use lyon_path::{Path, geom::{point, vector}, builder::SvgPathBuilder};
//!
//! // Use the SVG adapter.
//! let mut builder = Path::builder().with_svg();
//!
//! // All sub-paths *must* have be contained in a being/end pair.
//! builder.move_to(point(0.0, 0.0));
//! builder.line_to(point(1.0, 0.0));
//! builder.quadratic_bezier_to(point(2.0, 0.0), point(2.0, 1.0));
//! // No need to explicitly end a sub-path.
//!
//! builder.move_to(point(10.0, 0.0));
//! builder.relative_cubic_bezier_to(vector(2.0, 2.0), vector(1.0, 2.0), vector(-5.0, 0.0));
//! builder.close();
//!
//! let path = builder.build();
//! ```
//!
//! Implementors of the `PathBuilder` trait automatically gain access to a few other adapters.
//! For example a builder that approximates curves with a sequence of line segments:
//!
//! ```
//! use lyon_path::{Path, traits::PathBuilder, geom::point};
//!
//! let tolerance = 0.05;// maximum distance between a curve and its approximation.
//! let mut builder = Path::builder().flattened(tolerance);
//!
//! builder.begin(point(0.0, 0.0));
//! builder.quadratic_bezier_to(point(1.0, 0.0), point(1.0, 1.0));
//! builder.end(true);
//!
//! // The resulting path contains only Begin, Line and End events.
//! let path = builder.build();
//! ```
//!

use crate::events::PathEvent;
use crate::geom::{Arc, ArcFlags, SvgArc, LineSegment, traits::Transformation};
use crate::math::*;
use crate::polygon::Polygon;
use crate::path::Verb;
use crate::{EndpointId, Winding};

use std::marker::Sized;
use std::iter::IntoIterator;

/// The radius of each corner of a rounded rectangle.
#[derive(Copy, Clone)]
pub struct BorderRadii {
    pub top_left: f32,
    pub top_right: f32,
    pub bottom_left: f32,
    pub bottom_right: f32,
}

impl BorderRadii {
    pub fn new(radius: f32) -> Self {
        let r = radius.abs();
        BorderRadii {
            top_left: r,
            top_right: r,
            bottom_left: r,
            bottom_right: r,
        }
    }
}

/// The base path building interface.
///
/// Unlike `SvgPathBuilder`, this interface strictly requires sub-paths to be manually
/// started and ended (See the `begin` and `end` methods).
/// All positions are provided in absolute coordinates.
///
/// The goal of this interface is to abstract over simple and fast implementations that
/// do not deal with corner cases such as adding segments without starting a sub-path.
///
/// More elaborate interfaces are built on top of the provided primitives. In particular,
/// the `SvgPathBuilder` trait providing more permissive and richer interface is
/// automatically implemented via the `WithSvg` adapter (See the `with_svg` method).
pub trait PathBuilder {
    /// Starts a new sub-path at a given position.
    ///
    /// There must be no sub-path in progress when this method is called.
    /// `at` becomes the current position of the sub-path.
    fn begin(&mut self, at: Point) -> EndpointId;

    /// Ends the current sub path.
    ///
    /// A sub-path must be in progress when this method is called.
    /// After this method is called, there is no sub-path in progress until
    /// `begin` is called again.
    fn end(&mut self, close: bool);

    /// Closes the current sub path.
    ///
    /// Shorthand for `builder.end(true)`.
    fn close(&mut self) {
        self.end(true)
    }

    /// Adds a line segment to the current sub-path.
    ///
    /// A sub-path must be in progress when this method is called.
    fn line_to(&mut self, to: Point) -> EndpointId;

    /// Adds a quadratic bézier curve to the current sub-path.
    ///
    /// A sub-path must be in progress when this method is called.
    fn quadratic_bezier_to(&mut self, ctrl: Point, to: Point) -> EndpointId;

    /// Adds a cubic bézier curve to the current sub-path.
    ///
    /// A sub-path must be in progress when this method is called.
    fn cubic_bezier_to(&mut self, ctrl1: Point, ctrl2: Point, to: Point) -> EndpointId;

    /// Hints at the builder that a certain number of endpoints and control
    /// points will be added.
    ///
    /// The Builder implementation may use this information to pre-allocate
    /// memory as an optimization.
    fn reserve(&mut self, _endpoints: usize, _ctrl_points: usize) {}

    /// Applies the provided path event.
    ///
    /// By default this calls one of `begin`, `end`, `line`, `quadratic_bezier_segment`,
    /// or `cubic_bezier_segment` according to the path event.
    ///
    /// The requirements for each method apply to the corresponding event.
    fn path_event(&mut self, event: PathEvent) {
        match event {
            PathEvent::Begin { at } => {
                self.begin(at);
            }
            PathEvent::Line { to, .. } => {
                self.line_to(to);
            }
            PathEvent::Quadratic { ctrl, to, .. } => {
                self.quadratic_bezier_to(ctrl, to);
            }
            PathEvent::Cubic { ctrl1, ctrl2, to, .. } => {
                self.cubic_bezier_to(ctrl1, ctrl2, to);
            }
            PathEvent::End { close, .. } => {
                self.end(close);
            }
        }
    }

    /// Adds events from an iterator.
    fn extend<Evts>(&mut self, events: Evts)
    where
        Evts: IntoIterator<Item = PathEvent>
    {
        for evt in events.into_iter() {
            self.path_event(evt)
        }
    }

    /// Adds a sub-path from a polygon.
    ///
    /// There must be no sub-path in progress when this method is called.
    /// No sub-path is in progress after the method is called.
    fn add_polygon(&mut self, polygon: Polygon<Point>) {
        if polygon.points.is_empty() {
            return;
        }

        self.reserve(polygon.points.len(), 0);

        self.begin(polygon.points[0]);
        for p in &polygon.points[1..] {
            self.line_to(*p);
        }

        self.end(polygon.closed);
    }

    /// Adds a sub-path containing a single point.
    ///
    /// There must be no sub-path in progress when this method is called.
    /// No sub-path is in progress after the method is called.
    fn add_point(&mut self, at: Point) -> EndpointId {
        let id = self.begin(at);
        self.end(false);

        id
    }

    /// Adds a sub-path containing a single line segment.
    ///
    /// There must be no sub-path in progress when this method is called.
    /// No sub-path is in progress after the method is called.
    fn add_line_segment(&mut self, line: &LineSegment<f32>) -> (EndpointId, EndpointId) {
        let a = self.begin(line.from);
        let b = self.line_to(line.to);
        self.end(false);

        (a, b)
    }

    /// Adds a sub-path containing an ellipse.
    ///
    /// There must be no sub-path in progress when this method is called.
    /// No sub-path is in progress after the method is called.
    fn add_ellipse(&mut self, center: Point, radii: Vector, x_rotation: Angle, winding: Winding) {
        let dir = match winding {
            Winding::Positive => 1.0,
            Winding::Negative => -1.0,
        };

        use std::f32::consts::PI;
        let arc = Arc {
            center,
            radii,
            x_rotation,
            start_angle: Angle::radians(0.0),
            sweep_angle: Angle::radians(2.0 * PI) * dir,
        };

        self.begin(arc.sample(0.0));
        arc.for_each_quadratic_bezier(&mut |curve| {
            self.quadratic_bezier_to(curve.ctrl, curve.to);
        });
        self.end(true);
    }

    /// Adds a sub-path containing a circle.
    ///
    /// There must be no sub-path in progress when this method is called.
    /// No sub-path is in progress after the method is called.
    fn add_circle(&mut self, center: Point, radius: f32, winding: Winding)
    where
        Self: Sized
    {
        add_circle(self, center, radius, winding);
    }

    /// Adds a sub-path containing a rectangle.
    ///
    /// There must be no sub-path in progress when this method is called.
    /// No sub-path is in progress after the method is called.
    fn add_rectangle(&mut self, rect: &Rect, winding: Winding) {
        match winding {
            Winding::Positive => self.add_polygon(Polygon {
                points: &[
                    rect.min(),
                    point(rect.max_x(), rect.min_y()),
                    rect.max(),
                    point(rect.min_x(), rect.max_y()),
                ],
                closed: true,
            }),
            Winding::Negative => self.add_polygon(Polygon {
                points: &[
                    rect.min(),
                    point(rect.min_x(), rect.max_y()),
                    rect.max(),
                    point(rect.max_x(), rect.min_y()),
                ],
                closed: true,
            }),
        };
    }

    /// Adds a sub-path containing a rectangle.
    ///
    /// There must be no sub-path in progress when this method is called.
    /// No sub-path is in progress after the method is called.
    fn add_rounded_rectangle(&mut self, rect: &Rect, radii: &BorderRadii, winding: Winding)
    where
        Self: Sized
    {
        add_rounded_rectangle(self, rect, radii, winding);
    }

    /// Returns a builder that approximates all curves with sequences of line segments.
    fn flattened(self, tolerance: f32) -> Flattened<Self>
    where
        Self: Sized,
    {
        Flattened::new(self, tolerance)
    }

    /// Returns a builder that applies the given transformation to all positions.
    fn transformed<Transform>(self, transform: Transform) -> Transformed<Self, Transform>
    where
        Self: Sized,
        Transform: Transformation<f32>
    {
        Transformed::new(self, transform)
    }

    /// Returns a builder that support SVG commands.
    ///
    /// This must be called before starting to add any sub-path.
    fn with_svg(self) -> WithSvg<Self>
    where
        Self: Sized,
    {
        WithSvg::new(self)
    }
}

/// A path building interface that tries to stay close to SVG's path specification.
/// https://svgwg.org/specs/paths/
///
/// Some of the wording in the documentation of this trait is borrowed from the SVG
/// specification.
///
/// Unlike `PathBuilder`, implementations of this trait are expected to deal with
/// various corners cases such as adding segments without starting a sub-path.
pub trait SvgPathBuilder {
    /// Start a new sub-path at the given position.
    ///
    /// Corresponding SVG command: `M`.
    ///
    /// This command establishes a new initial point and a new current point. The effect
    /// is as if the "pen" were lifted and moved to a new location.
    /// If a sub-path is in progress, it is ended without being closed.
    fn move_to(&mut self, to: Point);

    /// ends the current sub-path by connecting it back to its initial point.
    ///
    /// Corresponding SVG command: `Z`.
    ///
    /// A straight line is drawn from the current point to the initial point of the
    /// current sub-path.
    /// The current position is set to the initial position of the sub-path that was
    /// closed.
    fn close(&mut self);

    /// Adds a line segment to the current sub-path.
    ///
    /// Corresponding SVG command: `L`.
    ///
    /// The segment starts at the builder's current position.
    /// If this is the very first command of the path (the builder therefore does not
    /// have a current position), the `line_to` command is replaced with a `move_to(to)`.
    fn line_to(&mut self, to: Point);

    /// Adds a quadratic bézier segment to the current sub-path.
    ///
    /// Corresponding SVG command: `Q`.
    ///
    /// The segment starts at the builder's current position.
    /// If this is the very first command of the path (the builder therefore does not
    /// have a current position), the `quadratic_bezier_to` command is replaced with
    /// a `move_to(to)`.
    fn quadratic_bezier_to(&mut self, ctrl: Point, to: Point);

    /// Adds a cubic bézier segment to the current sub-path.
    ///
    /// Corresponding SVG command: `C`.
    ///
    /// The segment starts at the builder's current position.
    /// If this is the very first command of the path (the builder therefore does not
    /// have a current position), the `cubic_bezier_to` command is replaced with
    /// a `move_to(to)`.
    fn cubic_bezier_to(&mut self, ctrl1: Point, ctrl2: Point, to: Point);

    /// Equivalent to `move_to` in relative coordinates.
    ///
    /// Corresponding SVG command: `m`.
    ///
    /// the provided coordinates are offsets relative to the current position of
    /// the builder.
    fn relative_move_to(&mut self, to: Vector);

    /// Equivalent to `line_to` in relative coordinates.
    ///
    /// Corresponding SVG command: `l`.
    ///
    /// the provided coordinates are offsets relative to the current position of
    /// the builder.
    fn relative_line_to(&mut self, to: Vector);

    /// Equivalent to `quadratic_bezier_to` in relative coordinates.
    ///
    /// Corresponding SVG command: `q`.
    ///
    /// the provided coordinates are offsets relative to the current position of
    /// the builder.
    fn relative_quadratic_bezier_to(&mut self, ctrl: Vector, to: Vector);

    /// Equivalent to `cubic_bezier_to` in relative coordinates.
    ///
    /// the provided coordinates are offsets relative to the current position of
    /// the builder.
    fn relative_cubic_bezier_to(&mut self, ctrl1: Vector, ctrl2: Vector, to: Vector);

    /// Equivalent to `cubic_bezier_to` with implicit first control point.
    ///
    /// Corresponding SVG command: `S`.
    ///
    /// The first control point is assumed to be the reflection of the second
    /// control point on the previous command relative to the current point.
    /// If there is no previous command or if the previous command was not a
    /// cubic bézier segment, the first control point is coincident with
    /// the current position.
    fn smooth_cubic_bezier_to(&mut self, ctrl2: Point, to: Point);

    /// Equivalent to `smooth_cubic_bezier_to` in relative coordinates.
    ///
    /// Corresponding SVG command: `s`.
    ///
    /// the provided coordinates are offsets relative to the current position of
    /// the builder.
    fn smooth_relative_cubic_bezier_to(&mut self, ctrl2: Vector, to: Vector);

    /// Equivalent to `quadratic_bezier_to` with implicit control point.
    ///
    /// Corresponding SVG command: `T`.
    ///
    /// The control point is assumed to be the reflection of the control
    /// point on the previous command relative to the current point.
    /// If there is no previous command or if the previous command was not a
    /// quadratic bézier segment, a line segment is added instead.
    fn smooth_quadratic_bezier_to(&mut self, to: Point);

    /// Equivalent to `smooth_quadratic_bezier_to` in relative coordinates.
    ///
    /// Corresponding SVG command: `t`.
    ///
    /// the provided coordinates are offsets relative to the current position of
    /// the builder.
    fn smooth_relative_quadratic_bezier_to(&mut self, to: Vector);

    /// Adds an horizontal line segment.
    ///
    /// Corresponding SVG command: `L`.
    ///
    /// Equivalent to `line_to`, using the y coordinate of the current position.
    fn horizontal_line_to(&mut self, x: f32);

    /// Adds an horizontal line segment in relative coordinates.
    ///
    /// Corresponding SVG command: `l`.
    ///
    /// Equivalent to `line_to`, using the y coordinate of the current position.
    /// `dx` is the horizontal offset relative to the current position.
    fn relative_horizontal_line_to(&mut self, dx: f32);

    /// Adds a vertical line segment.
    ///
    /// Corresponding SVG command: `V`.
    ///
    /// Equivalent to `line_to`, using the x coordinate of the current position.
    fn vertical_line_to(&mut self, y: f32);

    /// Adds a vertical line segment in relative coordinates.
    ///
    /// Corresponding SVG command: `v`.
    ///
    /// Equivalent to `line_to`, using the y coordinate of the current position.
    /// `dy` is the horizontal offset relative to the current position.
    fn relative_vertical_line_to(&mut self, dy: f32);

    /// Adds an elliptical arc.
    ///
    /// Corresponding SVG command: `A`.
    ///
    /// The arc starts at the current point and ends at `to`.
    /// The size and orientation of the ellipse are defined by `radii` and an `x_rotation`,
    /// which indicates how the ellipse as a whole is rotated relative to the current coordinate
    /// system. The center of the ellipse is calculated automatically to satisfy the constraints
    /// imposed by the other parameters. the arc `flags` contribute to the automatic calculations
    /// and help determine how the arc is built.
    fn arc_to(&mut self, radii: Vector, x_rotation: Angle, flags: ArcFlags, to: Point);

    /// Equivalent to `arc_to` in relative coordinates.
    ///
    /// Corresponding SVG command: `a`.
    ///
    /// the provided `to` coordinates are offsets relative to the current position of
    /// the builder.
    fn relative_arc_to(&mut self, radii: Vector, x_rotation: Angle, flags: ArcFlags, to: Vector);

    /// Hints at the builder that a certain number of endpoints and control
    /// points will be added.
    ///
    /// The Builder implementation may use this information to pre-allocate
    /// memory as an optimization.
    fn reserve(&mut self, _endpoints: usize, _ctrl_points: usize) {}

    /// Adds a sub-path from a polygon.
    ///
    /// There must be no sub-path in progress when this method is called.
    /// No sub-path is in progress after the method is called.
    fn add_polygon(&mut self, polygon: Polygon<Point>) {
        if polygon.points.is_empty() {
            return;
        }

        self.reserve(polygon.points.len(), 0);

        self.move_to(polygon.points[0]);
        for p in &polygon.points[1..] {
            self.line_to(*p);
        }

        if polygon.closed {
            self.close();
        }
    }
}

/// Builds a path.
///
/// This trait is separate from `PathBuilder` and `SvgPathBuilder` to allow them to
/// be used as trait object (which isn't possible when a method returns an associated
/// type).
pub trait Build {
    /// The type of object that is created by this builder.
    type PathType;

    /// Builds a path object and resets the builder so that it can be used again.
    fn build(self) -> Self::PathType;
}


/// A Builder that approximates curves with successions of line segments.
pub struct Flattened<Builder> {
    builder: Builder,
    current_position: Point,
    tolerance: f32,
}

impl<Builder: Build> Build for Flattened<Builder> {
    type PathType = Builder::PathType;

    fn build(self) -> Builder::PathType {
        self.builder.build()
    }
}

impl<Builder: PathBuilder> PathBuilder for Flattened<Builder> {

    fn begin(&mut self, at: Point) -> EndpointId {
        self.current_position = at;
        self.builder.begin(at)
    }

    fn end(&mut self, close: bool) {
        self.builder.end(close)
    }

    fn line_to(&mut self, to: Point) -> EndpointId {
        let id = self.builder.line_to(to);
        self.current_position = to;

        id
    }

    fn quadratic_bezier_to(&mut self, ctrl: Point, to: Point) -> EndpointId {
        let id = crate::private::flatten_quadratic_bezier(self.tolerance, self.current_position, ctrl, to, self);
        self.current_position = to;

        id
    }

    fn cubic_bezier_to(&mut self, ctrl1: Point, ctrl2: Point, to: Point) -> EndpointId {
        let id = crate::private::flatten_cubic_bezier(self.tolerance, self.current_position, ctrl1, ctrl2, to, self);
        self.current_position = to;

        id
    }

    fn reserve(&mut self, endpoints: usize, ctrl_points: usize) {
        self.builder.reserve(endpoints + ctrl_points * 4, 0);
    }
}

impl<Builder: PathBuilder> Flattened<Builder> {
    pub fn new(builder: Builder, tolerance: f32) -> Flattened<Builder> {
        Flattened {
            builder,
            current_position: point(0.0, 0.0),
            tolerance,
        }
    }

    pub fn build(self) -> Builder::PathType where Builder: Build {
        self.builder.build()
    }

    pub fn set_tolerance(&mut self, tolerance: f32) {
        self.tolerance = tolerance
    }
}

/// Builds a path with a transformation applied.
pub struct Transformed<Builder, Transform> {
    builder: Builder,
    transform: Transform,
}

impl<Builder, Transform> Transformed<Builder, Transform> {
    #[inline]
    pub fn new(builder: Builder, transform: Transform) -> Self {
        Transformed {
            builder,
            transform,
        }
    }

    #[inline]
    pub fn set_transform(&mut self, transform: Transform) {
        self.transform = transform;
    }
}

impl<Builder: Build, Transform> Build for Transformed<Builder, Transform> {
    type PathType = Builder::PathType;

    #[inline]
    fn build(self) -> Builder::PathType {
        self.builder.build()
    }
}

impl<Builder, Transform> PathBuilder for Transformed<Builder, Transform>
where
    Builder: PathBuilder,
    Transform: Transformation<f32>,
{
    #[inline]
    fn begin(&mut self, at: Point) -> EndpointId {
        self.builder.begin(self.transform.transform_point(at))
    }

    #[inline]
    fn end(&mut self, close: bool) {
        self.builder.end(close)
    }

    #[inline]
    fn line_to(&mut self, to: Point) -> EndpointId {
        self.builder.line_to(self.transform.transform_point(to))
    }

    #[inline]
    fn quadratic_bezier_to(&mut self, ctrl: Point, to: Point) -> EndpointId {
        self.builder.quadratic_bezier_to(
            self.transform.transform_point(ctrl),
            self.transform.transform_point(to),
        )
    }

    #[inline]
    fn cubic_bezier_to(&mut self, ctrl1: Point, ctrl2: Point, to: Point) -> EndpointId {
        self.builder.cubic_bezier_to(
            self.transform.transform_point(ctrl1),
            self.transform.transform_point(ctrl2),
            self.transform.transform_point(to),
        )
    }

    #[inline]
    fn reserve(&mut self, endpoints: usize, ctrl_points: usize) {
        self.builder.reserve(endpoints, ctrl_points);
    }
}

/// Implements an SVG-like building interface on top of a PathBuilder.
pub struct WithSvg<Builder: PathBuilder> {
    builder: Builder,

    first_position: Point,
    current_position: Point,
    last_ctrl: Point,
    last_cmd: Verb,
    need_moveto: bool,
    is_empty: bool,
}

impl<Builder: PathBuilder> WithSvg<Builder> {

    pub fn new(builder: Builder) -> Self {
        WithSvg {
            builder,
            first_position: point(0.0, 0.0),
            current_position: point(0.0, 0.0),
            last_ctrl: point(0.0, 0.0),
            need_moveto: true,
            is_empty: true,
            last_cmd: Verb::End,
        }
    }

    pub fn build(mut self) -> Builder::PathType where Builder: Build {
        self.end_if_needed();
        self.builder.build()
    }

    pub fn flattened(self, tolerance: f32) -> WithSvg<Flattened<Builder>> {
        WithSvg::new(Flattened::new(self.builder, tolerance))
    }

    pub fn transformed<Transform>(self, transform: Transform) -> WithSvg<Transformed<Builder, Transform>>
    where
        Transform: Transformation<f32>
    {
        WithSvg::new(Transformed::new(self.builder, transform))
    }

    pub fn move_to(&mut self, to: Point) -> EndpointId {
        self.end_if_needed();

        let id = self.builder.begin(to);

        self.is_empty = false;
        self.need_moveto = false;
        self.first_position = to;
        self.current_position = to;
        self.last_cmd = Verb::Begin;

        id
    }

    pub fn line_to(&mut self, to: Point) -> EndpointId {
        if let Some(id) = self.begin_if_needed(&to) {
            return id;
        }

        self.current_position = to;
        self.last_cmd = Verb::LineTo;

        self.builder.line_to(to)
    }

    pub fn close(&mut self) {
        if self.need_moveto {
            return;
        }

        // Relative path ops tend to accumulate small floating point imprecisions
        // which results in the last segment ending almost but not quite at the
        // start of the sub-path, causing a new edge to be inserted which often
        // intersects with the first or last edge. This can affect algorithms that
        // Don't handle self-intersecting paths.
        // Deal with this by snapping the last point if it is very close to the
        // start of the sub path.
        //
        // TODO
        // if let Some(p) = self.builder.points.last_mut() {
        //     let d = (*p - self.first_position).abs();
        //     if d.x + d.y < 0.0001 {
        //         *p = self.first_position;
        //     }
        // }

        self.current_position = self.first_position;
        self.need_moveto = true;
        self.last_cmd = Verb::Close;

        self.builder.close();
    }

    pub fn quadratic_bezier_to(&mut self, ctrl: Point, to: Point) -> EndpointId {
        if let Some(id) = self.begin_if_needed(&to) {
            return id;
        }

        self.current_position = to;
        self.last_cmd = Verb::QuadraticTo;
        self.last_ctrl = ctrl;

        self.builder.quadratic_bezier_to(ctrl, to)
    }

    pub fn cubic_bezier_to(&mut self, ctrl1: Point, ctrl2: Point, to: Point) -> EndpointId {
        if let Some(id) = self.begin_if_needed(&to) {
            return id;
        }

        self.current_position = to;
        self.last_cmd = Verb::CubicTo;
        self.last_ctrl = ctrl2;

        self.builder.cubic_bezier_to(ctrl1, ctrl2, to)
    }

    pub fn arc(&mut self, center: Point, radii: Vector, sweep_angle: Angle, x_rotation: Angle) {
        nan_check(center);
        nan_check(radii.to_point());
        debug_assert!(!sweep_angle.get().is_nan());
        debug_assert!(!x_rotation.get().is_nan());

        let start_angle = (self.current_position - center).angle_from_x_axis() - x_rotation;
        let arc = Arc {
            start_angle,
            center,
            radii,
            sweep_angle,
            x_rotation,
        };

        // If the current position is not on the arc, move or line to the beginning of the
        // arc.
        let arc_start = arc.from();
        if self.need_moveto {
            self.move_to(arc_start);
        } else if (arc_start - self.current_position).square_length() < 0.01 {
            self.builder.line_to(arc_start);
        }

        arc.for_each_quadratic_bezier(&mut |curve| {
            self.builder.quadratic_bezier_to(curve.ctrl, curve.to);
        });

        self.last_ctrl = self.current_position;
    }

    /// Ensures the current sub-path has a moveto command.
    ///
    /// Returns an ID if the command should be skipped and the ID returned instead.
    #[inline(always)]
    fn begin_if_needed(&mut self, default: &Point) -> Option<EndpointId> {
        if self.need_moveto {
            return self.insert_move_to(default)
        }

        None
    }

    #[inline(never)]
    fn insert_move_to(&mut self, default: &Point) -> Option<EndpointId> {
        if self.is_empty {
            return Some(self.move_to(*default))
        }

        self.move_to(self.first_position);

        None
    }

    fn end_if_needed(&mut self) {
        if (self.last_cmd as u8) <= (Verb::Begin as u8) {
            self.builder.end(false);
        }
    }

    pub fn current_position(&self) -> Point {
        self.current_position
    }

    pub fn reserve(&mut self, endpoints: usize, ctrl_points: usize) {
        self.builder.reserve(endpoints, ctrl_points);
    }

    fn get_smooth_cubic_ctrl(&self) -> Point {
        match self.last_cmd {
            Verb::CubicTo => self.current_position + (self.current_position - self.last_ctrl),
            _ => self.current_position,
        }
    }

    fn get_smooth_quadratic_ctrl(&self) -> Point {
        match self.last_cmd {
            Verb::QuadraticTo => self.current_position + (self.current_position - self.last_ctrl),
            _ => self.current_position,
        }
    }

    fn relative_to_absolute(&self, v: Vector) -> Point {
        self.current_position + v
    }
}

impl<Builder, Transform> WithSvg<Transformed<Builder, Transform>>
where
    Builder: PathBuilder,
    Transform: Transformation<f32>,
{
    #[inline]
    pub fn set_transform(&mut self, transform: Transform) {
        self.builder.set_transform(transform);
    }
}


impl<Builder: PathBuilder + Build> Build for WithSvg<Builder> {
    type PathType = Builder::PathType;

    fn build(mut self) -> Builder::PathType {
        self.end_if_needed();
        self.builder.build()
    }
}

impl<Builder: PathBuilder> SvgPathBuilder for WithSvg<Builder> {
    fn move_to(&mut self, to: Point) {
        self.move_to(to);
    }

    fn line_to(&mut self, to: Point) {
        self.line_to(to);
    }

    fn quadratic_bezier_to(&mut self, ctrl: Point, to: Point) {
        self.quadratic_bezier_to(ctrl, to);
    }

    fn cubic_bezier_to(&mut self, ctrl1: Point, ctrl2: Point, to: Point) {
        self.cubic_bezier_to(ctrl1, ctrl2, to);
    }

    fn close(&mut self) {
        self.close();
    }

    fn relative_move_to(&mut self, to: Vector) {
        let to = self.relative_to_absolute(to);
        self.move_to(to);
    }

    fn relative_line_to(&mut self, to: Vector) {
        let to = self.relative_to_absolute(to);
        self.line_to(to);
    }

    fn relative_quadratic_bezier_to(&mut self, ctrl: Vector, to: Vector) {
        let ctrl = self.relative_to_absolute(ctrl);
        let to = self.relative_to_absolute(to);
        self.builder.quadratic_bezier_to(ctrl, to);
    }

    fn relative_cubic_bezier_to(&mut self, ctrl1: Vector, ctrl2: Vector, to: Vector) {
        let to = self.relative_to_absolute(to);
        let ctrl1 = self.relative_to_absolute(ctrl1);
        let ctrl2 = self.relative_to_absolute(ctrl2);
        self.cubic_bezier_to(ctrl1, ctrl2, to);
    }

    fn smooth_cubic_bezier_to(&mut self, ctrl2: Point, to: Point) {
        let ctrl1 = self.get_smooth_cubic_ctrl();
        self.cubic_bezier_to(ctrl1, ctrl2, to);
    }

    fn smooth_relative_cubic_bezier_to(&mut self, ctrl2: Vector, to: Vector) {
        let ctrl1 = self.get_smooth_cubic_ctrl();
        let ctrl2 = self.relative_to_absolute(ctrl2);
        let to = self.relative_to_absolute(to);
        self.cubic_bezier_to(ctrl1, ctrl2, to);
    }

    fn smooth_quadratic_bezier_to(&mut self, to: Point) {
        let ctrl = self.get_smooth_quadratic_ctrl();
        self.quadratic_bezier_to(ctrl, to);
    }

    fn smooth_relative_quadratic_bezier_to(&mut self, to: Vector) {
        let ctrl = self.get_smooth_quadratic_ctrl();
        let to = self.relative_to_absolute(to);
        self.quadratic_bezier_to(ctrl, to);
    }

    fn horizontal_line_to(&mut self, x: f32) {
        let y = self.current_position.y;
        self.line_to(point(x, y));
    }

    fn relative_horizontal_line_to(&mut self, dx: f32) {
        let p = self.current_position;
        self.line_to(point(p.x + dx, p.y));
    }

    fn vertical_line_to(&mut self, y: f32) {
        let x = self.current_position.x;
        self.line_to(point(x, y));
    }

    fn relative_vertical_line_to(&mut self, dy: f32) {
        let p = self.current_position;
        self.line_to(point(p.x, p.y + dy));
    }

    fn arc_to(&mut self, radii: Vector, x_rotation: Angle, flags: ArcFlags, to: Point) {
        let arc = SvgArc {
            from: self.current_position,
            to,
            radii,
            x_rotation,
            flags: ArcFlags {
                large_arc: flags.large_arc,
                sweep: flags.sweep,
            },
        }.to_arc();

        self.arc(arc.center, arc.radii, arc.sweep_angle, arc.x_rotation);
    }

    fn relative_arc_to(&mut self, radii: Vector, x_rotation: Angle, flags: ArcFlags, to: Vector) {
        let to = self.relative_to_absolute(to);
        self.arc_to(radii, x_rotation, flags, to);
    }

    fn reserve(&mut self, endpoints: usize, ctrl_points: usize) {
        self.builder.reserve(endpoints, ctrl_points);
    }
}

/// Tessellate the stroke for an axis-aligned rounded rectangle.
fn add_circle<Builder: PathBuilder>(
    builder: &mut Builder,
    center: Point,
    radius: f32,
    winding: Winding,
) {
    let radius = radius.abs();
    let dir = match winding {
        Winding::Positive => 1.0,
        Winding::Negative => -1.0,
    };

    let tan_pi_over_8 = 0.41421356237;
    let cos_pi_over_4 = 0.70710678118;
    let d = radius * tan_pi_over_8;

    builder.begin(center + vector(-radius, 0.0));

    let ctrl_0 = center + vector(-radius, -d * dir);
    let mid_0 = center + vector(-1.0, -dir) * radius * cos_pi_over_4;
    let ctrl_1 = center + vector(-d, -radius * dir);
    let mid_1 = center + vector(0.0, -radius * dir);
    builder.quadratic_bezier_to(ctrl_0, mid_0);
    builder.quadratic_bezier_to(ctrl_1, mid_1);

    let ctrl_0 = center + vector(d, -radius * dir);
    let mid_0 = center + vector(1.0, -dir) * radius * cos_pi_over_4;
    let ctrl_1 = center + vector(radius, -d * dir);
    let mid_1 = center + vector(radius, 0.0);
    builder.quadratic_bezier_to(ctrl_0, mid_0);
    builder.quadratic_bezier_to(ctrl_1, mid_1);

    let ctrl_0 = center + vector(radius, d * dir);
    let mid_0 = center + vector(1.0, dir) * radius * cos_pi_over_4;
    let ctrl_1 = center + vector(d, radius * dir);
    let mid_1 = center + vector(0.0, radius * dir);
    builder.quadratic_bezier_to(ctrl_0, mid_0);
    builder.quadratic_bezier_to(ctrl_1, mid_1);

    let ctrl_0 = center + vector(-d, radius * dir);
    let mid_0 = center + vector(-1.0, dir) * radius * cos_pi_over_4;
    let ctrl_1 = center + vector(-radius, d * dir);
    let mid_1 = center + vector(-radius, 0.0);
    builder.quadratic_bezier_to(ctrl_0, mid_0);
    builder.quadratic_bezier_to(ctrl_1, mid_1);

    builder.close();
}

/// Tessellate the stroke for an axis-aligned rounded rectangle.
fn add_rounded_rectangle<Builder: PathBuilder>(
    builder: &mut Builder,
    rect: &Rect,
    radii: &BorderRadii,
    winding: Winding,
) {
    let w = rect.size.width;
    let h = rect.size.height;
    let x_min = rect.min_x();
    let y_min = rect.min_y();
    let x_max = rect.max_x();
    let y_max = rect.max_y();
    let min_wh = w.min(h);
    let mut tl = radii.top_left.abs().min(min_wh);
    let mut tr = radii.top_right.abs().min(min_wh);
    let mut bl = radii.bottom_left.abs().min(min_wh);
    let mut br = radii.bottom_right.abs().min(min_wh);

    // clamp border radii if they don't fit in the rectangle.
    if tl + tr > w {
        let x = (tl + tr - w) * 0.5;
        tl -= x;
        tr -= x;
    }
    if bl + br > w {
        let x = (bl + br - w) * 0.5;
        bl -= x;
        br -= x;
    }
    if tr + br > h {
        let x = (tr + br - h) * 0.5;
        tr -= x;
        br -= x;
    }
    if tl + bl > h {
        let x = (tl + bl - h) * 0.5;
        tl -= x;
        bl -= x;
    }

    let tan_pi_over_8 = 0.41421356237;
    let cos_pi_over_4 = 0.70710678118;

    let tl_d = tl * tan_pi_over_8;
    let tl_corner = point(x_min, y_min);

    let tr_d = tr * tan_pi_over_8;
    let tr_corner = point(x_max, y_min);

    let br_d = br * tan_pi_over_8;
    let br_corner = point(x_max, y_max);

    let bl_d = bl * tan_pi_over_8;
    let bl_corner = point(x_min, y_max);

    let points = [
        point(x_min, y_min + tl),
        tl_corner + vector(0.0, tl - tl_d),
        tl_corner + vector(1.0, 1.0) * tl * (1.0 - cos_pi_over_4),
        tl_corner + vector(tl - tl_d, 0.0),
        tl_corner + vector(tl, 0.0),
        point(x_max - tr, y_min),
        tr_corner + vector(-tr + tr_d, 0.0),
        tr_corner + vector(-1.0, 1.0) * tr * (1.0 - cos_pi_over_4),
        tr_corner + vector(0.0, tr - tr_d),
        tr_corner + vector(0.0, tr),
        point(x_max, y_max - br),
        br_corner + vector(0.0, -br + br_d),
        br_corner + vector(-1.0, -1.0) * br * (1.0 - cos_pi_over_4),
        br_corner + vector(-br + br_d, 0.0),
        br_corner + vector(-br, 0.0),
        point(x_min + bl, y_max),
        bl_corner + vector(bl - bl_d, 0.0),
        bl_corner + vector(1.0, -1.0) * bl * (1.0 - cos_pi_over_4),
        bl_corner + vector(0.0, -bl + bl_d),
        bl_corner + vector(0.0, -bl),
    ];

    if winding == Winding::Positive {
        builder.begin(points[0]);
        if tl > 0.0 {
            builder.quadratic_bezier_to(points[1], points[2]);
            builder.quadratic_bezier_to(points[3], points[4]);
        }
        builder.line_to(points[5]);
        if tl > 0.0 {
            builder.quadratic_bezier_to(points[6], points[7]);
            builder.quadratic_bezier_to(points[8], points[9]);
        }
        builder.line_to(points[10]);
        if br > 0.0 {
            builder.quadratic_bezier_to(points[11], points[12]);
            builder.quadratic_bezier_to(points[13], points[14]);
        }
        builder.line_to(points[15]);
        if bl > 0.0 {
            builder.quadratic_bezier_to(points[16], points[17]);
            builder.quadratic_bezier_to(points[18], points[19]);
        }
        builder.end(true);
    } else {
        builder.begin(points[19]);
        if bl > 0.0 {
            builder.quadratic_bezier_to(points[18], points[17]);
            builder.quadratic_bezier_to(points[16], points[15]);
        }
        builder.line_to(points[14]);
        if br > 0.0 {
            builder.quadratic_bezier_to(points[13], points[12]);
            builder.quadratic_bezier_to(points[11], points[10]);
        }
        builder.line_to(points[9]);
        if tl > 0.0 {
            builder.quadratic_bezier_to(points[8], points[7]);
            builder.quadratic_bezier_to(points[6], points[5]);
        }
        builder.line_to(points[4]);
        if tl > 0.0 {
            builder.quadratic_bezier_to(points[3], points[2]);
            builder.quadratic_bezier_to(points[1], points[0]);
        }
        builder.end(true);
    }
}

#[inline]
fn nan_check(p: Point) {
    debug_assert!(p.x.is_finite());
    debug_assert!(p.y.is_finite());
}

#[test]
fn svg_builder_line_to_after_close() {
    use crate::Path;
    use crate::PathEvent;

    let mut p = Path::svg_builder();
    p.line_to(point(1.0, 0.0));
    p.close();
    p.line_to(point(2.0, 0.0));

    let path = p.build();
    let mut it = path.iter();
    assert_eq!(
        it.next(),
        Some(PathEvent::Begin {
            at: point(1.0, 0.0)
        })
    );
    assert_eq!(
        it.next(),
        Some(PathEvent::End {
            last: point(1.0, 0.0),
            first: point(1.0, 0.0),
            close: true
        })
    );
    assert_eq!(
        it.next(),
        Some(PathEvent::Begin {
            at: point(1.0, 0.0)
        })
    );
    assert_eq!(
        it.next(),
        Some(PathEvent::Line {
            from: point(1.0, 0.0),
            to: point(2.0, 0.0)
        })
    );
    assert_eq!(
        it.next(),
        Some(PathEvent::End {
            last: point(2.0, 0.0),
            first: point(1.0, 0.0),
            close: false
        })
    );
    assert_eq!(it.next(), None);
}