/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

//! Specified values.
//!
//! TODO(emilio): Enhance docs.

use app_units::Au;
use context::QuirksMode;
use cssparser::{self, Parser, Token};
use euclid::size::Size2D;
use itoa;
use parser::{ParserContext, Parse};
use self::grid::TrackSizeOrRepeat;
use self::url::SpecifiedUrl;
use std::ascii::AsciiExt;
use std::f32;
use std::fmt;
use std::io::Write;
use style_traits::ToCss;
use style_traits::values::specified::AllowedNumericType;
use super::{Auto, CSSFloat, CSSInteger, Either, None_};
use super::computed::{self, Context};
use super::computed::{Shadow as ComputedShadow, ToComputedValue};
use super::generics::BorderRadiusSize as GenericBorderRadiusSize;
use super::generics::grid::{TrackBreadth as GenericTrackBreadth, TrackSize as GenericTrackSize};
use super::generics::grid::TrackList as GenericTrackList;
use values::specified::calc::CalcNode;

#[cfg(feature = "gecko")]
pub use self::align::{AlignItems, AlignJustifyContent, AlignJustifySelf, JustifyItems};
pub use self::background::BackgroundSize;
pub use self::border::{BorderImageSlice, BorderImageWidth, BorderImageWidthSide};
pub use self::color::Color;
pub use self::rect::LengthOrNumberRect;
pub use super::generics::grid::GridLine;
pub use self::image::{ColorStop, EndingShape as GradientEndingShape, Gradient};
pub use self::image::{GradientItem, GradientKind, Image, ImageRect, ImageLayer};
pub use self::length::AbsoluteLength;
pub use self::length::{FontRelativeLength, ViewportPercentageLength, CharacterWidth, Length, CalcLengthOrPercentage};
pub use self::length::{Percentage, LengthOrNone, LengthOrNumber, LengthOrPercentage, LengthOrPercentageOrAuto};
pub use self::length::{LengthOrPercentageOrNone, LengthOrPercentageOrAutoOrContent, NoCalcLength};
pub use self::length::{MaxLength, MozLength};
pub use self::position::{Position, PositionComponent};

#[cfg(feature = "gecko")]
pub mod align;
pub mod background;
pub mod basic_shape;
pub mod border;
pub mod calc;
pub mod color;
pub mod grid;
pub mod image;
pub mod length;
pub mod position;
pub mod rect;

/// Common handling for the specified value CSS url() values.
pub mod url {
use cssparser::Parser;
use parser::{Parse, ParserContext};
use values::computed::ComputedValueAsSpecified;

#[cfg(feature = "servo")]
pub use ::servo::url::*;
#[cfg(feature = "gecko")]
pub use ::gecko::url::*;

impl Parse for SpecifiedUrl {
    fn parse(context: &ParserContext, input: &mut Parser) -> Result<Self, ()> {
        let url = try!(input.expect_url());
        Self::parse_from_string(url, context)
    }
}

impl Eq for SpecifiedUrl {}

// TODO(emilio): Maybe consider ComputedUrl to save a word in style structs?
impl ComputedValueAsSpecified for SpecifiedUrl {}

no_viewport_percentage!(SpecifiedUrl);
}

#[derive(Clone, PartialEq, Debug)]
#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
#[allow(missing_docs)]
pub struct CSSColor {
    pub parsed: Color,
    pub authored: Option<Box<str>>,
}

impl Parse for CSSColor {
    fn parse(context: &ParserContext, input: &mut Parser) -> Result<Self, ()> {
        Self::parse_quirky(context, input, AllowQuirks::No)
    }
}

impl CSSColor {
    /// Parse a color, with quirks.
    ///
    /// https://quirks.spec.whatwg.org/#the-hashless-hex-color-quirk
    pub fn parse_quirky(context: &ParserContext,
                        input: &mut Parser,
                        allow_quirks: AllowQuirks)
                        -> Result<Self, ()> {
        let start_position = input.position();
        let authored = match input.next() {
            Ok(Token::Ident(s)) => Some(s.into_owned().into_boxed_str()),
            _ => None,
        };
        input.reset(start_position);
        if let Ok(parsed) = input.try(|i| Parse::parse(context, i)) {
            return Ok(CSSColor {
                parsed: parsed,
                authored: authored,
            });
        }
        if !allow_quirks.allowed(context.quirks_mode) {
            return Err(());
        }
        let (number, dimension) = match input.next()? {
            Token::Number(number) => {
                (number, None)
            },
            Token::Dimension(number, dimension) => {
                (number, Some(dimension))
            },
            Token::Ident(ident) => {
                if ident.len() != 3 && ident.len() != 6 {
                    return Err(());
                }
                return cssparser::Color::parse_hash(ident.as_bytes()).map(|color| {
                    Self {
                        parsed: color.into(),
                        authored: None
                    }
                });
            }
            _ => {
                return Err(());
            },
        };
        let value = number.int_value.ok_or(())?;
        if value < 0 {
            return Err(());
        }
        let length = if value <= 9 {
            1
        } else if value <= 99 {
            2
        } else if value <= 999 {
            3
        } else if value <= 9999 {
            4
        } else if value <= 99999 {
            5
        } else if value <= 999999 {
            6
        } else {
            return Err(())
        };
        let total = length + dimension.as_ref().map_or(0, |d| d.len());
        if total > 6 {
            return Err(());
        }
        let mut serialization = [b'0'; 6];
        let space_padding = 6 - total;
        let mut written = space_padding;
        written += itoa::write(&mut serialization[written..], value).unwrap();
        if let Some(dimension) = dimension {
            written += (&mut serialization[written..]).write(dimension.as_bytes()).unwrap();
        }
        debug_assert!(written == 6);
        Ok(CSSColor {
            parsed: cssparser::Color::parse_hash(&serialization).map(From::from)?,
            authored: None,
        })
    }
}

no_viewport_percentage!(CSSColor);

impl ToCss for CSSColor {
    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
        match self.authored {
            Some(ref s) => dest.write_str(s),
            None => self.parsed.to_css(dest),
        }
    }
}

impl From<Color> for CSSColor {
    fn from(color: Color) -> Self {
        CSSColor {
            parsed: color,
            authored: None,
        }
    }
}

impl CSSColor {
    #[inline]
    /// Returns currentcolor value.
    pub fn currentcolor() -> CSSColor {
        Color::CurrentColor.into()
    }

    #[inline]
    /// Returns transparent value.
    pub fn transparent() -> CSSColor {
        // We should probably set authored to "transparent", but maybe it doesn't matter.
        Color::RGBA(cssparser::RGBA::transparent()).into()
    }
}

#[derive(Clone, PartialEq, Debug)]
#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
#[allow(missing_docs)]
pub struct CSSRGBA {
    pub parsed: cssparser::RGBA,
    pub authored: Option<Box<str>>,
}

no_viewport_percentage!(CSSRGBA);

impl ToCss for CSSRGBA {
    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
        match self.authored {
            Some(ref s) => dest.write_str(s),
            None => self.parsed.to_css(dest),
        }
    }
}

/// Parse an `<integer>` value, handling `calc()` correctly.
pub fn parse_integer(context: &ParserContext, input: &mut Parser) -> Result<Integer, ()> {
    match try!(input.next()) {
        Token::Number(ref value) => value.int_value.ok_or(()).map(Integer::new),
        Token::Function(ref name) if name.eq_ignore_ascii_case("calc") => {
            let result = try!(input.parse_nested_block(|i| {
                CalcNode::parse_integer(context, i)
            }));

            Ok(Integer::from_calc(result))
        }
        _ => Err(())
    }
}

/// Parse a `<number>` value, handling `calc()` correctly, and without length
/// limitations.
pub fn parse_number(context: &ParserContext, input: &mut Parser) -> Result<Number, ()> {
    parse_number_with_clamping_mode(context, input, AllowedNumericType::All)
}

/// Parse a `<number>` value, with a given clamping mode.
pub fn parse_number_with_clamping_mode(context: &ParserContext,
                                       input: &mut Parser,
                                       clamping_mode: AllowedNumericType)
                                       -> Result<Number, ()> {
    match try!(input.next()) {
        Token::Number(ref value) if clamping_mode.is_ok(value.value) => {
            Ok(Number {
                value: value.value.min(f32::MAX).max(f32::MIN),
                calc_clamping_mode: None,
            })
        },
        Token::Function(ref name) if name.eq_ignore_ascii_case("calc") => {
            let result = try!(input.parse_nested_block(|i| {
                CalcNode::parse_number(context, i)
            }));

            Ok(Number {
                value: result.min(f32::MAX).max(f32::MIN),
                calc_clamping_mode: Some(clamping_mode),
            })
        }
        _ => Err(())
    }
}

/// The specified value of `BorderRadiusSize`
pub type BorderRadiusSize = GenericBorderRadiusSize<LengthOrPercentage>;

impl Parse for BorderRadiusSize {
    #[inline]
    fn parse(context: &ParserContext, input: &mut Parser) -> Result<Self, ()> {
        let first = try!(LengthOrPercentage::parse_non_negative(context, input));
        let second = input.try(|i| LengthOrPercentage::parse_non_negative(context, i))
            .unwrap_or_else(|()| first.clone());
        Ok(GenericBorderRadiusSize(Size2D::new(first, second)))
    }
}

#[derive(Clone, Copy, Debug, HasViewportPercentage, PartialEq)]
#[cfg_attr(feature = "servo", derive(HeapSizeOf, Deserialize, Serialize))]
/// An angle consisting of a value and a unit.
///
/// Computed Angle is essentially same as specified angle except calc
/// value serialization. Therefore we are using computed Angle enum
/// to hold the value and unit type.
pub struct Angle {
    value: computed::Angle,
    was_calc: bool,
}

impl ToCss for Angle {
    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
        if self.was_calc {
            dest.write_str("calc(")?;
        }
        self.value.to_css(dest)?;
        if self.was_calc {
            dest.write_str(")")?;
        }
        Ok(())
    }
}

impl ToComputedValue for Angle {
    type ComputedValue = computed::Angle;

    fn to_computed_value(&self, _context: &Context) -> Self::ComputedValue {
        self.value
    }

    fn from_computed_value(computed: &Self::ComputedValue) -> Self {
        Angle {
            value: *computed,
            was_calc: false,
        }
    }
}

impl Angle {
    /// Returns an angle with the given value in degrees.
    pub fn from_degrees(value: CSSFloat, was_calc: bool) -> Self {
        Angle { value: computed::Angle::Degree(value), was_calc: was_calc }
    }

    /// Returns an angle with the given value in gradians.
    pub fn from_gradians(value: CSSFloat, was_calc: bool) -> Self {
        Angle { value: computed::Angle::Gradian(value), was_calc: was_calc }
    }

    /// Returns an angle with the given value in turns.
    pub fn from_turns(value: CSSFloat, was_calc: bool) -> Self {
        Angle { value: computed::Angle::Turn(value), was_calc: was_calc }
    }

    /// Returns an angle with the given value in radians.
    pub fn from_radians(value: CSSFloat, was_calc: bool) -> Self {
        Angle { value: computed::Angle::Radian(value), was_calc: was_calc }
    }

    #[inline]
    #[allow(missing_docs)]
    pub fn radians(self) -> f32 {
        self.value.radians()
    }

    /// Returns an angle value that represents zero.
    pub fn zero() -> Self {
        Self::from_degrees(0.0, false)
    }

    /// Returns an `Angle` parsed from a `calc()` expression.
    pub fn from_calc(radians: CSSFloat) -> Self {
        Angle {
            value: computed::Angle::Radian(radians),
            was_calc: true,
        }
    }
}

impl Parse for Angle {
    /// Parses an angle according to CSS-VALUES § 6.1.
    fn parse(context: &ParserContext, input: &mut Parser) -> Result<Self, ()> {
        match try!(input.next()) {
            Token::Dimension(ref value, ref unit) => {
                Angle::parse_dimension(value.value,
                                       unit,
                                       /* from_calc = */ false)
            }
            Token::Function(ref name) if name.eq_ignore_ascii_case("calc") => {
                input.parse_nested_block(|i| CalcNode::parse_angle(context, i))
            }
            _ => Err(())
        }
    }
}

impl Angle {
    /// Parse an `<angle>` value given a value and an unit.
    pub fn parse_dimension(
        value: CSSFloat,
        unit: &str,
        from_calc: bool)
        -> Result<Angle, ()>
    {
        let angle = match_ignore_ascii_case! { unit,
            "deg" => Angle::from_degrees(value, from_calc),
            "grad" => Angle::from_gradians(value, from_calc),
            "turn" => Angle::from_turns(value, from_calc),
            "rad" => Angle::from_radians(value, from_calc),
             _ => return Err(())
        };
        Ok(angle)
    }
    /// Parse an angle, including unitless 0 degree.
    ///
    /// Note that numbers without any AngleUnit, including unitless 0 angle,
    /// should be invalid. However, some properties still accept unitless 0
    /// angle and stores it as '0deg'.
    ///
    /// We can remove this and get back to the unified version Angle::parse once
    /// https://github.com/w3c/csswg-drafts/issues/1162 is resolved.
    pub fn parse_with_unitless(context: &ParserContext, input: &mut Parser) -> Result<Self, ()> {
        match try!(input.next()) {
            Token::Dimension(ref value, ref unit) => {
                Angle::parse_dimension(value.value,
                                       unit,
                                       /* from_calc = */ false)
            }
            Token::Number(ref value) if value.value == 0. => Ok(Angle::zero()),
            Token::Function(ref name) if name.eq_ignore_ascii_case("calc") => {
                input.parse_nested_block(|i| CalcNode::parse_angle(context, i))
            }
            _ => Err(())
        }
    }
}

#[allow(missing_docs)]
pub fn parse_border_radius(context: &ParserContext, input: &mut Parser) -> Result<BorderRadiusSize, ()> {
    input.try(|i| BorderRadiusSize::parse(context, i)).or_else(|_| {
        match_ignore_ascii_case! { &try!(input.expect_ident()),
            "thin" => Ok(BorderRadiusSize::circle(
                             LengthOrPercentage::Length(NoCalcLength::from_px(1.)))),
            "medium" => Ok(BorderRadiusSize::circle(
                               LengthOrPercentage::Length(NoCalcLength::from_px(3.)))),
            "thick" => Ok(BorderRadiusSize::circle(
                              LengthOrPercentage::Length(NoCalcLength::from_px(5.)))),
            _ => Err(())
        }
    })
}

#[allow(missing_docs)]
pub fn parse_border_width(context: &ParserContext, input: &mut Parser) -> Result<Length, ()> {
    input.try(|i| Length::parse_non_negative(context, i)).or_else(|()| {
        match_ignore_ascii_case! { &try!(input.expect_ident()),
            "thin" => Ok(Length::from_px(1.)),
            "medium" => Ok(Length::from_px(3.)),
            "thick" => Ok(Length::from_px(5.)),
            _ => Err(())
        }
    })
}

#[derive(Clone, Debug, HasViewportPercentage, PartialEq)]
#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
#[allow(missing_docs)]
pub enum BorderWidth {
    Thin,
    Medium,
    Thick,
    Width(Length),
}

impl Parse for BorderWidth {
    fn parse(context: &ParserContext, input: &mut Parser) -> Result<BorderWidth, ()> {
        Self::parse_quirky(context, input, AllowQuirks::No)
    }
}

impl BorderWidth {
    /// Parses a border width, allowing quirks.
    pub fn parse_quirky(context: &ParserContext,
                        input: &mut Parser,
                        allow_quirks: AllowQuirks)
                        -> Result<BorderWidth, ()> {
        match input.try(|i| Length::parse_non_negative_quirky(context, i, allow_quirks)) {
            Ok(length) => Ok(BorderWidth::Width(length)),
            Err(_) => match_ignore_ascii_case! { &try!(input.expect_ident()),
               "thin" => Ok(BorderWidth::Thin),
               "medium" => Ok(BorderWidth::Medium),
               "thick" => Ok(BorderWidth::Thick),
               _ => Err(())
            }
        }
    }
}

impl BorderWidth {
    #[allow(missing_docs)]
    pub fn from_length(length: Length) -> Self {
        BorderWidth::Width(length)
    }
}

impl ToCss for BorderWidth {
    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
        match *self {
            BorderWidth::Thin => dest.write_str("thin"),
            BorderWidth::Medium => dest.write_str("medium"),
            BorderWidth::Thick => dest.write_str("thick"),
            BorderWidth::Width(ref length) => length.to_css(dest)
        }
    }
}

impl ToComputedValue for BorderWidth {
    type ComputedValue = Au;

    #[inline]
    fn to_computed_value(&self, context: &Context) -> Self::ComputedValue {
        // We choose the pixel length of the keyword values the same as both spec and gecko.
        // Spec: https://drafts.csswg.org/css-backgrounds-3/#line-width
        // Gecko: https://bugzilla.mozilla.org/show_bug.cgi?id=1312155#c0
        match *self {
            BorderWidth::Thin => Length::from_px(1.).to_computed_value(context),
            BorderWidth::Medium => Length::from_px(3.).to_computed_value(context),
            BorderWidth::Thick => Length::from_px(5.).to_computed_value(context),
            BorderWidth::Width(ref length) => length.to_computed_value(context)
        }
    }

    #[inline]
    fn from_computed_value(computed: &Self::ComputedValue) -> Self {
        BorderWidth::Width(ToComputedValue::from_computed_value(computed))
    }
}

// The integer values here correspond to the border conflict resolution rules in CSS 2.1 §
// 17.6.2.1. Higher values override lower values.
define_numbered_css_keyword_enum! { BorderStyle:
    "none" => none = -1,
    "solid" => solid = 6,
    "double" => double = 7,
    "dotted" => dotted = 4,
    "dashed" => dashed = 5,
    "hidden" => hidden = -2,
    "groove" => groove = 1,
    "ridge" => ridge = 3,
    "inset" => inset = 0,
    "outset" => outset = 2,
}

no_viewport_percentage!(BorderStyle);

impl BorderStyle {
    /// Whether this border style is either none or hidden.
    pub fn none_or_hidden(&self) -> bool {
        matches!(*self, BorderStyle::none | BorderStyle::hidden)
    }
}

/// A time in seconds according to CSS-VALUES § 6.2.
#[derive(Clone, Copy, Debug, PartialEq, PartialOrd)]
#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
pub struct Time {
    seconds: CSSFloat,
    was_calc: bool,
}

impl Time {
    /// Return a `<time>` value that represents `seconds` seconds.
    pub fn from_seconds(seconds: CSSFloat) -> Self {
        Time {
            seconds: seconds,
            was_calc: false,
        }
    }

    /// Returns a time that represents a duration of zero.
    pub fn zero() -> Self {
        Self::from_seconds(0.0)
    }

    /// Returns the time in fractional seconds.
    pub fn seconds(self) -> CSSFloat {
        self.seconds
    }

    /// Parses a time according to CSS-VALUES § 6.2.
    pub fn parse_dimension(
        value: CSSFloat,
        unit: &str,
        from_calc: bool)
        -> Result<Time, ()>
    {
        let seconds = match_ignore_ascii_case! { unit,
            "s" => value,
            "ms" => value / 1000.0,
            _ => return Err(()),
        };

        Ok(Time {
            seconds: seconds,
            was_calc: from_calc,
        })
    }

    /// Returns a `Time` value from a CSS `calc()` expression.
    pub fn from_calc(seconds: CSSFloat) -> Self {
        Time {
            seconds: seconds,
            was_calc: true,
        }
    }

    fn parse_with_clamping_mode(context: &ParserContext,
                                input: &mut Parser,
                                clamping_mode: AllowedNumericType) -> Result<Self, ()> {
        match input.next() {
            Ok(Token::Dimension(ref value, ref unit)) if clamping_mode.is_ok(value.value) => {
                Time::parse_dimension(value.value, &unit, /* from_calc = */ false)
            }
            Ok(Token::Function(ref name)) if name.eq_ignore_ascii_case("calc") => {
                match input.parse_nested_block(|i| CalcNode::parse_time(context, i)) {
                    Ok(time) if clamping_mode.is_ok(time.seconds) => Ok(time),
                    _ => Err(()),
                }
            }
            _ => Err(())
        }
    }

    /// Parse <time> that values are non-negative.
    pub fn parse_non_negative(context: &ParserContext, input: &mut Parser) -> Result<Self, ()> {
        Self::parse_with_clamping_mode(context, input, AllowedNumericType::NonNegative)
    }
}

impl ToComputedValue for Time {
    type ComputedValue = computed::Time;

    fn to_computed_value(&self, _context: &Context) -> Self::ComputedValue {
        computed::Time::from_seconds(self.seconds())
    }

    fn from_computed_value(computed: &Self::ComputedValue) -> Self {
        Time {
            seconds: computed.seconds(),
            was_calc: false,
        }
    }
}

impl Parse for Time {
    fn parse(context: &ParserContext, input: &mut Parser) -> Result<Self, ()> {
        Self::parse_with_clamping_mode(context, input, AllowedNumericType::All)
    }
}

impl ToCss for Time {
    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
        if self.was_calc {
            dest.write_str("calc(")?;
        }
        write!(dest, "{}s", self.seconds)?;
        if self.was_calc {
            dest.write_str(")")?;
        }
        Ok(())
    }
}

#[derive(Clone, Copy, Debug, PartialEq, PartialOrd)]
#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
#[allow(missing_docs)]
pub struct Number {
    /// The numeric value itself.
    value: CSSFloat,
    /// If this number came from a calc() expression, this tells how clamping
    /// should be done on the value.
    calc_clamping_mode: Option<AllowedNumericType>,
}

no_viewport_percentage!(Number);

impl Parse for Number {
    fn parse(context: &ParserContext, input: &mut Parser) -> Result<Self, ()> {
        parse_number(context, input)
    }
}

impl Number {
    /// Returns a new number with the value `val`.
    pub fn new(val: CSSFloat) -> Self {
        Number {
            value: val,
            calc_clamping_mode: None,
        }
    }

    /// Returns the numeric value, clamped if needed.
    pub fn get(&self) -> f32 {
        self.calc_clamping_mode.map_or(self.value, |mode| mode.clamp(self.value))
    }

    #[allow(missing_docs)]
    pub fn parse_non_negative(context: &ParserContext, input: &mut Parser) -> Result<Number, ()> {
        if context.parsing_mode.allows_all_numeric_values() {
            parse_number(context, input)
        } else {
            parse_number_with_clamping_mode(context, input, AllowedNumericType::NonNegative)
        }
    }

    #[allow(missing_docs)]
    pub fn parse_at_least_one(context: &ParserContext, input: &mut Parser) -> Result<Number, ()> {
        if context.parsing_mode.allows_all_numeric_values() {
            parse_number(context, input)
        } else {
            parse_number_with_clamping_mode(context, input, AllowedNumericType::AtLeastOne)
        }
    }
}

impl ToComputedValue for Number {
    type ComputedValue = CSSFloat;

    #[inline]
    fn to_computed_value(&self, _: &Context) -> CSSFloat { self.get() }

    #[inline]
    fn from_computed_value(computed: &CSSFloat) -> Self {
        Number {
            value: *computed,
            calc_clamping_mode: None,
        }
    }
}

impl ToCss for Number {
    fn to_css<W>(&self, dest: &mut W) -> fmt::Result
        where W: fmt::Write,
    {
        if self.calc_clamping_mode.is_some() {
            dest.write_str("calc(")?;
        }
        self.value.to_css(dest)?;
        if self.calc_clamping_mode.is_some() {
            dest.write_str(")")?;
        }
        Ok(())
    }
}

/// <number-percentage>
/// Accepts only non-negative numbers.
#[derive(Clone, Copy, Debug, PartialEq)]
#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
#[allow(missing_docs)]
pub enum NumberOrPercentage {
    Percentage(Percentage),
    Number(Number),
}

no_viewport_percentage!(NumberOrPercentage);

impl NumberOrPercentage {
    fn parse_with_clamping_mode(context: &ParserContext,
                                input: &mut Parser,
                                type_: AllowedNumericType)
                                -> Result<Self, ()> {
        if let Ok(per) = input.try(|i| Percentage::parse_with_clamping_mode(i, type_)) {
            return Ok(NumberOrPercentage::Percentage(per));
        }

        parse_number_with_clamping_mode(context, input, type_).map(NumberOrPercentage::Number)
    }

    /// Parse a non-negative number or percentage.
    pub fn parse_non_negative(context: &ParserContext, input: &mut Parser) -> Result<Self, ()> {
        Self::parse_with_clamping_mode(context, input, AllowedNumericType::NonNegative)
    }
}

impl Parse for NumberOrPercentage {
    fn parse(context: &ParserContext, input: &mut Parser) -> Result<Self, ()> {
        Self::parse_with_clamping_mode(context, input, AllowedNumericType::All)
    }
}

impl ToCss for NumberOrPercentage {
    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
        match *self {
            NumberOrPercentage::Percentage(percentage) => percentage.to_css(dest),
            NumberOrPercentage::Number(number) => number.to_css(dest),
        }
    }
}

#[derive(Clone, Copy, Debug, PartialEq, PartialOrd)]
#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
#[allow(missing_docs)]
pub struct Opacity(Number);

no_viewport_percentage!(Opacity);

impl Parse for Opacity {
    fn parse(context: &ParserContext, input: &mut Parser) -> Result<Self, ()> {
        parse_number(context, input).map(Opacity)
    }
}

impl ToComputedValue for Opacity {
    type ComputedValue = CSSFloat;

    #[inline]
    fn to_computed_value(&self, context: &Context) -> CSSFloat {
        self.0.to_computed_value(context).min(1.0).max(0.0)
    }

    #[inline]
    fn from_computed_value(computed: &CSSFloat) -> Self {
        Opacity(Number::from_computed_value(computed))
    }
}

impl ToCss for Opacity {
    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
        self.0.to_css(dest)
    }
}

#[derive(Clone, Copy, Debug, PartialEq, PartialOrd)]
#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
#[allow(missing_docs)]
pub struct Integer {
    value: CSSInteger,
    was_calc: bool,
}

impl Integer {
    /// Trivially constructs a new `Integer` value.
    pub fn new(val: CSSInteger) -> Self {
        Integer {
            value: val,
            was_calc: false,
        }
    }

    /// Returns the integer value associated with this value.
    pub fn value(&self) -> CSSInteger {
        self.value
    }

    /// Trivially constructs a new integer value from a `calc()` expression.
    fn from_calc(val: CSSInteger) -> Self {
        Integer {
            value: val,
            was_calc: true,
        }
    }
}

no_viewport_percentage!(Integer);

impl Parse for Integer {
    fn parse(context: &ParserContext, input: &mut Parser) -> Result<Self, ()> {
        parse_integer(context, input)
    }
}

impl Integer {
    #[allow(missing_docs)]
    pub fn parse_with_minimum(context: &ParserContext, input: &mut Parser, min: i32) -> Result<Integer, ()> {
        match parse_integer(context, input) {
            Ok(value) if value.value() >= min => Ok(value),
            _ => Err(()),
        }
    }

    #[allow(missing_docs)]
    pub fn parse_non_negative(context: &ParserContext, input: &mut Parser) -> Result<Integer, ()> {
        Integer::parse_with_minimum(context, input, 0)
    }

    #[allow(missing_docs)]
    pub fn parse_positive(context: &ParserContext, input: &mut Parser) -> Result<Integer, ()> {
        Integer::parse_with_minimum(context, input, 1)
    }
}

impl ToComputedValue for Integer {
    type ComputedValue = i32;

    #[inline]
    fn to_computed_value(&self, _: &Context) -> i32 { self.value }

    #[inline]
    fn from_computed_value(computed: &i32) -> Self {
        Integer::new(*computed)
    }
}

impl ToCss for Integer {
    fn to_css<W>(&self, dest: &mut W) -> fmt::Result
        where W: fmt::Write,
    {
        if self.was_calc {
            dest.write_str("calc(")?;
        }
        write!(dest, "{}", self.value)?;
        if self.was_calc {
            dest.write_str(")")?;
        }
        Ok(())
    }
}

/// <integer> | auto
pub type IntegerOrAuto = Either<Integer, Auto>;

impl IntegerOrAuto {
    #[allow(missing_docs)]
    pub fn parse_positive(context: &ParserContext,
                          input: &mut Parser)
                          -> Result<IntegerOrAuto, ()> {
        match IntegerOrAuto::parse(context, input) {
            Ok(Either::First(integer)) if integer.value() <= 0 => Err(()),
            result => result,
        }
    }
}

#[allow(missing_docs)]
pub type UrlOrNone = Either<SpecifiedUrl, None_>;

/// The specified value of a grid `<track-breadth>`
pub type TrackBreadth = GenericTrackBreadth<LengthOrPercentage>;

/// The specified value of a grid `<track-size>`
pub type TrackSize = GenericTrackSize<LengthOrPercentage>;

/// The specified value of a grid `<track-list>`
/// (could also be `<auto-track-list>` or `<explicit-track-list>`)
pub type TrackList = GenericTrackList<TrackSizeOrRepeat>;

/// `<track-list> | none`
pub type TrackListOrNone = Either<TrackList, None_>;

#[derive(Clone, Debug, HasViewportPercentage, PartialEq)]
#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
#[allow(missing_docs)]
pub struct Shadow {
    pub offset_x: Length,
    pub offset_y: Length,
    pub blur_radius: Length,
    pub spread_radius: Length,
    pub color: Option<CSSColor>,
    pub inset: bool,
}

impl ToComputedValue for Shadow {
    type ComputedValue = ComputedShadow;

    #[inline]
    fn to_computed_value(&self, context: &Context) -> Self::ComputedValue {
        ComputedShadow {
            offset_x: self.offset_x.to_computed_value(context),
            offset_y: self.offset_y.to_computed_value(context),
            blur_radius: self.blur_radius.to_computed_value(context),
            spread_radius: self.spread_radius.to_computed_value(context),
            color: self.color
                        .as_ref()
                        .map(|color| color.to_computed_value(context))
                        .unwrap_or(cssparser::Color::CurrentColor),
            inset: self.inset,
        }
    }

    #[inline]
    fn from_computed_value(computed: &ComputedShadow) -> Self {
        Shadow {
            offset_x: ToComputedValue::from_computed_value(&computed.offset_x),
            offset_y: ToComputedValue::from_computed_value(&computed.offset_y),
            blur_radius: ToComputedValue::from_computed_value(&computed.blur_radius),
            spread_radius: ToComputedValue::from_computed_value(&computed.spread_radius),
            color: Some(ToComputedValue::from_computed_value(&computed.color)),
            inset: computed.inset,
        }
    }
}

impl Shadow {
    // disable_spread_and_inset is for filter: drop-shadow(...)
    #[allow(missing_docs)]
    pub fn parse(context: &ParserContext, input: &mut Parser, disable_spread_and_inset: bool) -> Result<Shadow, ()> {
        let mut lengths = [Length::zero(), Length::zero(), Length::zero(), Length::zero()];
        let mut lengths_parsed = false;
        let mut color = None;
        let mut inset = false;

        loop {
            if !inset && !disable_spread_and_inset {
                if input.try(|input| input.expect_ident_matching("inset")).is_ok() {
                    inset = true;
                    continue
                }
            }
            if !lengths_parsed {
                if let Ok(value) = input.try(|i| Length::parse(context, i)) {
                    lengths[0] = value;
                    lengths[1] = try!(Length::parse(context, input));
                    if let Ok(value) = input.try(|i| Length::parse_non_negative(context, i)) {
                        lengths[2] = value;
                        if !disable_spread_and_inset {
                            if let Ok(value) = input.try(|i| Length::parse(context, i)) {
                                lengths[3] = value;
                            }
                        }
                    }
                    lengths_parsed = true;
                    continue
                }
            }
            if color.is_none() {
                if let Ok(value) = input.try(|i| CSSColor::parse(context, i)) {
                    color = Some(value);
                    continue
                }
            }
            break
        }

        // Lengths must be specified.
        if !lengths_parsed {
            return Err(())
        }

        debug_assert!(!disable_spread_and_inset || lengths[3] == Length::zero());
        Ok(Shadow {
            offset_x: lengths[0].take(),
            offset_y: lengths[1].take(),
            blur_radius: lengths[2].take(),
            spread_radius: lengths[3].take(),
            color: color,
            inset: inset,
        })
    }
}

no_viewport_percentage!(SVGPaint);

/// An SVG paint value
///
/// https://www.w3.org/TR/SVG2/painting.html#SpecifyingPaint
#[derive(Debug, Clone, PartialEq)]
#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
pub struct SVGPaint {
    /// The paint source
    pub kind: SVGPaintKind,
    /// The fallback color
    pub fallback: Option<CSSColor>,
}

/// An SVG paint value without the fallback
///
/// Whereas the spec only allows PaintServer
/// to have a fallback, Gecko lets the context
/// properties have a fallback as well.
#[derive(Debug, Clone, PartialEq)]
#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
pub enum SVGPaintKind {
    /// `none`
    None,
    /// `<color>`
    Color(CSSColor),
    /// `url(...)`
    PaintServer(SpecifiedUrl),
    /// `context-fill`
    ContextFill,
    /// `context-stroke`
    ContextStroke,
}

impl SVGPaintKind {
    fn parse_ident(input: &mut Parser) -> Result<Self, ()> {
        Ok(match_ignore_ascii_case! { &input.expect_ident()?,
            "none" => SVGPaintKind::None,
            "context-fill" => SVGPaintKind::ContextFill,
            "context-stroke" => SVGPaintKind::ContextStroke,
            _ => return Err(())
        })
    }
}

impl Parse for SVGPaint {
    fn parse(context: &ParserContext, input: &mut Parser) -> Result<Self, ()> {
        if let Ok(url) = input.try(|i| SpecifiedUrl::parse(context, i)) {
            let fallback = input.try(|i| CSSColor::parse(context, i));
            Ok(SVGPaint {
                kind: SVGPaintKind::PaintServer(url),
                fallback: fallback.ok(),
            })
        } else if let Ok(kind) = input.try(SVGPaintKind::parse_ident) {
            if kind == SVGPaintKind::None {
                Ok(SVGPaint {
                    kind: kind,
                    fallback: None,
                })
            } else {
                let fallback = input.try(|i| CSSColor::parse(context, i));
                Ok(SVGPaint {
                    kind: kind,
                    fallback: fallback.ok(),
                })
            }
        } else if let Ok(color) = input.try(|i| CSSColor::parse(context, i)) {
            Ok(SVGPaint {
                kind: SVGPaintKind::Color(color),
                fallback: None,
            })
        } else {
            Err(())
        }
    }
}

impl ToCss for SVGPaintKind {
    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
        match *self {
            SVGPaintKind::None => dest.write_str("none"),
            SVGPaintKind::ContextStroke => dest.write_str("context-stroke"),
            SVGPaintKind::ContextFill => dest.write_str("context-fill"),
            SVGPaintKind::Color(ref color) => color.to_css(dest),
            SVGPaintKind::PaintServer(ref server) => server.to_css(dest),
        }
    }
}

impl ToCss for SVGPaint {
    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
        self.kind.to_css(dest)?;
        if let Some(ref fallback) = self.fallback {
            fallback.to_css(dest)?;
        }
        Ok(())
    }
}


impl ToComputedValue for SVGPaint {
    type ComputedValue = super::computed::SVGPaint;

    #[inline]
    fn to_computed_value(&self, context: &Context) -> Self::ComputedValue {
        super::computed::SVGPaint {
            kind: self.kind.to_computed_value(context),
            fallback: self.fallback.as_ref().map(|f| f.to_computed_value(context))
        }
    }

    #[inline]
    fn from_computed_value(computed: &Self::ComputedValue) -> Self {
        SVGPaint {
            kind: ToComputedValue::from_computed_value(&computed.kind),
            fallback: computed.fallback.as_ref().map(ToComputedValue::from_computed_value)
        }
    }
}

impl ToComputedValue for SVGPaintKind {
    type ComputedValue = super::computed::SVGPaintKind;

    #[inline]
    fn to_computed_value(&self, context: &Context) -> Self::ComputedValue {
        match *self {
            SVGPaintKind::None => super::computed::SVGPaintKind::None,
            SVGPaintKind::ContextStroke => super::computed::SVGPaintKind::ContextStroke,
            SVGPaintKind::ContextFill => super::computed::SVGPaintKind::ContextFill,
            SVGPaintKind::Color(ref color) => {
                super::computed::SVGPaintKind::Color(color.to_computed_value(context))
            }
            SVGPaintKind::PaintServer(ref server) => {
                super::computed::SVGPaintKind::PaintServer(server.to_computed_value(context))
            }
        }
    }

    #[inline]
    fn from_computed_value(computed: &Self::ComputedValue) -> Self {
        match *computed {
            super::computed::SVGPaintKind::None => SVGPaintKind::None,
            super::computed::SVGPaintKind::ContextStroke => SVGPaintKind::ContextStroke,
            super::computed::SVGPaintKind::ContextFill => SVGPaintKind::ContextFill,
            super::computed::SVGPaintKind::Color(ref color) => {
                SVGPaintKind::Color(ToComputedValue::from_computed_value(color))
            }
            super::computed::SVGPaintKind::PaintServer(ref server) => {
                SVGPaintKind::PaintServer(ToComputedValue::from_computed_value(server))
            }
        }
    }
}

/// <length> | <percentage> | <number>
pub type LengthOrPercentageOrNumber = Either<Number, LengthOrPercentage>;

impl LengthOrPercentageOrNumber {
    /// parse a <length-percentage> | <number> enforcing that the contents aren't negative
    pub fn parse_non_negative(context: &ParserContext, input: &mut Parser) -> Result<Self, ()> {
        // NB: Parse numbers before Lengths so we are consistent about how to
        // recognize and serialize "0".
        if let Ok(num) = input.try(|i| Number::parse_non_negative(context, i)) {
            return Ok(Either::First(num))
        }

        LengthOrPercentage::parse_non_negative(context, input).map(Either::Second)
    }
}

#[derive(Clone, Debug, HasViewportPercentage, PartialEq)]
#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
/// rect(<top>, <left>, <bottom>, <right>) used by clip and image-region
pub struct ClipRect {
    /// <top> (<length> | <auto>)
    pub top: Option<Length>,
    /// <right> (<length> | <auto>)
    pub right: Option<Length>,
    /// <bottom> (<length> | <auto>)
    pub bottom: Option<Length>,
    /// <left> (<length> | <auto>)
    pub left: Option<Length>,
}


impl ToCss for ClipRect {
    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
        try!(dest.write_str("rect("));

        if let Some(ref top) = self.top {
            try!(top.to_css(dest));
            try!(dest.write_str(", "));
        } else {
            try!(dest.write_str("auto, "));
        }

        if let Some(ref right) = self.right {
            try!(right.to_css(dest));
            try!(dest.write_str(", "));
        } else {
            try!(dest.write_str("auto, "));
        }

        if let Some(ref bottom) = self.bottom {
            try!(bottom.to_css(dest));
            try!(dest.write_str(", "));
        } else {
            try!(dest.write_str("auto, "));
        }

        if let Some(ref left) = self.left {
            try!(left.to_css(dest));
        } else {
            try!(dest.write_str("auto"));
        }

        try!(dest.write_str(")"));
        Ok(())
    }
}

impl ToComputedValue for ClipRect {
    type ComputedValue = super::computed::ClipRect;

    #[inline]
    fn to_computed_value(&self, context: &Context) -> super::computed::ClipRect {
        super::computed::ClipRect {
            top: self.top.as_ref().map(|top| top.to_computed_value(context)),
            right: self.right.as_ref().map(|right| right.to_computed_value(context)),
            bottom: self.bottom.as_ref().map(|bottom| bottom.to_computed_value(context)),
            left: self.left.as_ref().map(|left| left.to_computed_value(context)),
        }
    }

    #[inline]
    fn from_computed_value(computed: &super::computed::ClipRect) -> Self {
        ClipRect {
            top: computed.top.map(|top| ToComputedValue::from_computed_value(&top)),
            right: computed.right.map(|right| ToComputedValue::from_computed_value(&right)),
            bottom: computed.bottom.map(|bottom| ToComputedValue::from_computed_value(&bottom)),
            left: computed.left.map(|left| ToComputedValue::from_computed_value(&left)),
        }
    }
}

impl Parse for ClipRect {
    fn parse(context: &ParserContext, input: &mut Parser) -> Result<Self, ()> {
        Self::parse_quirky(context, input, AllowQuirks::No)
    }
}

impl ClipRect {
    /// Parses a rect(<top>, <left>, <bottom>, <right>), allowing quirks.
    pub fn parse_quirky(context: &ParserContext, input: &mut Parser,
                    allow_quirks: AllowQuirks) -> Result<Self, ()> {
        use values::specified::Length;

        fn parse_argument(context: &ParserContext, input: &mut Parser,
                          allow_quirks: AllowQuirks) -> Result<Option<Length>, ()> {
            if input.try(|input| input.expect_ident_matching("auto")).is_ok() {
                Ok(None)
            } else {
                Length::parse_quirky(context, input, allow_quirks).map(Some)
            }
        }

        if !try!(input.expect_function()).eq_ignore_ascii_case("rect") {
            return Err(())
        }

        input.parse_nested_block(|input| {
            let top = try!(parse_argument(context, input, allow_quirks));
            let right;
            let bottom;
            let left;

            if input.try(|input| input.expect_comma()).is_ok() {
                right = try!(parse_argument(context, input, allow_quirks));
                try!(input.expect_comma());
                bottom = try!(parse_argument(context, input, allow_quirks));
                try!(input.expect_comma());
                left = try!(parse_argument(context, input, allow_quirks));
            } else {
                right = try!(parse_argument(context, input, allow_quirks));
                bottom = try!(parse_argument(context, input, allow_quirks));
                left = try!(parse_argument(context, input, allow_quirks));
            }
            Ok(ClipRect {
                top: top,
                right: right,
                bottom: bottom,
                left: left,
            })
        })
    }
}

/// rect(...) | auto
pub type ClipRectOrAuto = Either<ClipRect, Auto>;

impl ClipRectOrAuto {
    /// Parses a ClipRect or Auto, allowing quirks.
    pub fn parse_quirky(context: &ParserContext, input: &mut Parser,
                        allow_quirks: AllowQuirks) -> Result<Self, ()> {
        if let Ok(v) = input.try(|i| ClipRect::parse_quirky(context, i, allow_quirks)) {
            Ok(Either::First(v))
        } else {
            Auto::parse(context, input).map(Either::Second)
        }
    }
}

/// <color> | auto
pub type ColorOrAuto = Either<CSSColor, Auto>;

/// Whether quirks are allowed in this context.
#[derive(Clone, Copy, PartialEq)]
pub enum AllowQuirks {
    /// Quirks are allowed.
    Yes,
    /// Quirks are not allowed.
    No,
}

impl AllowQuirks {
    /// Returns `true` if quirks are allowed in this context.
    pub fn allowed(self, quirks_mode: QuirksMode) -> bool {
        self == AllowQuirks::Yes && quirks_mode == QuirksMode::Quirks
    }
}