/* 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 https://mozilla.org/MPL/2.0/. */

//! Keyframes: https://drafts.csswg.org/css-animations/#keyframes

use crate::error_reporting::ContextualParseError;
use crate::parser::ParserContext;
use crate::properties::{
    longhands::{
        animation_composition::single_value::SpecifiedValue as SpecifiedComposition,
        transition_timing_function::single_value::SpecifiedValue as SpecifiedTimingFunction,
    },
    parse_property_declaration_list, LonghandId, PropertyDeclaration, PropertyDeclarationBlock,
    PropertyDeclarationId, PropertyDeclarationIdSet,
};
use crate::shared_lock::{DeepCloneWithLock, SharedRwLock, SharedRwLockReadGuard};
use crate::shared_lock::{Locked, ToCssWithGuard};
use crate::str::CssStringWriter;
use crate::stylesheets::rule_parser::VendorPrefix;
use crate::stylesheets::{CssRuleType, StylesheetContents};
use crate::values::{serialize_percentage, KeyframesName};
use cssparser::{
    parse_one_rule, AtRuleParser, DeclarationParser, Parser, ParserInput, ParserState,
    QualifiedRuleParser, RuleBodyItemParser, RuleBodyParser, SourceLocation, Token,
};
use servo_arc::Arc;
use std::borrow::Cow;
use std::fmt::{self, Write};
use style_traits::{CssWriter, ParseError, ParsingMode, StyleParseErrorKind, ToCss};

/// A [`@keyframes`][keyframes] rule.
///
/// [keyframes]: https://drafts.csswg.org/css-animations/#keyframes
#[derive(Debug, ToShmem)]
pub struct KeyframesRule {
    /// The name of the current animation.
    pub name: KeyframesName,
    /// The keyframes specified for this CSS rule.
    pub keyframes: Vec<Arc<Locked<Keyframe>>>,
    /// Vendor prefix type the @keyframes has.
    pub vendor_prefix: Option<VendorPrefix>,
    /// The line and column of the rule's source code.
    pub source_location: SourceLocation,
}

impl ToCssWithGuard for KeyframesRule {
    // Serialization of KeyframesRule is not specced.
    fn to_css(&self, guard: &SharedRwLockReadGuard, dest: &mut CssStringWriter) -> fmt::Result {
        dest.write_str("@keyframes ")?;
        self.name.to_css(&mut CssWriter::new(dest))?;
        dest.write_str(" {")?;
        let iter = self.keyframes.iter();
        for lock in iter {
            dest.write_str("\n")?;
            let keyframe = lock.read_with(&guard);
            keyframe.to_css(guard, dest)?;
        }
        dest.write_str("\n}")
    }
}

impl KeyframesRule {
    /// Returns the index of the last keyframe that matches the given selector.
    /// If the selector is not valid, or no keyframe is found, returns None.
    ///
    /// Related spec:
    /// <https://drafts.csswg.org/css-animations-1/#interface-csskeyframesrule-findrule>
    pub fn find_rule(&self, guard: &SharedRwLockReadGuard, selector: &str) -> Option<usize> {
        let mut input = ParserInput::new(selector);
        if let Ok(selector) = Parser::new(&mut input).parse_entirely(KeyframeSelector::parse) {
            for (i, keyframe) in self.keyframes.iter().enumerate().rev() {
                if keyframe.read_with(guard).selector == selector {
                    return Some(i);
                }
            }
        }
        None
    }
}

impl DeepCloneWithLock for KeyframesRule {
    fn deep_clone_with_lock(
        &self,
        lock: &SharedRwLock,
        guard: &SharedRwLockReadGuard,
    ) -> Self {
        KeyframesRule {
            name: self.name.clone(),
            keyframes: self
                .keyframes
                .iter()
                .map(|x| {
                    Arc::new(
                        lock.wrap(x.read_with(guard).deep_clone_with_lock(lock, guard)),
                    )
                })
                .collect(),
            vendor_prefix: self.vendor_prefix.clone(),
            source_location: self.source_location.clone(),
        }
    }
}

/// A number from 0 to 1, indicating the percentage of the animation when this
/// keyframe should run.
#[derive(Clone, Copy, Debug, MallocSizeOf, PartialEq, PartialOrd, ToShmem)]
pub struct KeyframePercentage(pub f32);

impl ::std::cmp::Ord for KeyframePercentage {
    #[inline]
    fn cmp(&self, other: &Self) -> ::std::cmp::Ordering {
        // We know we have a number from 0 to 1, so unwrap() here is safe.
        self.0.partial_cmp(&other.0).unwrap()
    }
}

impl ::std::cmp::Eq for KeyframePercentage {}

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

impl KeyframePercentage {
    /// Trivially constructs a new `KeyframePercentage`.
    #[inline]
    pub fn new(value: f32) -> KeyframePercentage {
        debug_assert!(value >= 0. && value <= 1.);
        KeyframePercentage(value)
    }

    fn parse<'i, 't>(input: &mut Parser<'i, 't>) -> Result<KeyframePercentage, ParseError<'i>> {
        let token = input.next()?.clone();
        match token {
            Token::Ident(ref identifier) if identifier.as_ref().eq_ignore_ascii_case("from") => {
                Ok(KeyframePercentage::new(0.))
            },
            Token::Ident(ref identifier) if identifier.as_ref().eq_ignore_ascii_case("to") => {
                Ok(KeyframePercentage::new(1.))
            },
            Token::Percentage {
                unit_value: percentage,
                ..
            } if percentage >= 0. && percentage <= 1. => Ok(KeyframePercentage::new(percentage)),
            _ => Err(input.new_unexpected_token_error(token)),
        }
    }
}

/// A keyframes selector is a list of percentages or from/to symbols, which are
/// converted at parse time to percentages.
#[derive(Clone, Debug, Eq, PartialEq, ToCss, ToShmem)]
#[css(comma)]
pub struct KeyframeSelector(#[css(iterable)] Vec<KeyframePercentage>);

impl KeyframeSelector {
    /// Return the list of percentages this selector contains.
    #[inline]
    pub fn percentages(&self) -> &[KeyframePercentage] {
        &self.0
    }

    /// A dummy public function so we can write a unit test for this.
    pub fn new_for_unit_testing(percentages: Vec<KeyframePercentage>) -> KeyframeSelector {
        KeyframeSelector(percentages)
    }

    /// Parse a keyframe selector from CSS input.
    pub fn parse<'i, 't>(input: &mut Parser<'i, 't>) -> Result<Self, ParseError<'i>> {
        input
            .parse_comma_separated(KeyframePercentage::parse)
            .map(KeyframeSelector)
    }
}

/// A keyframe.
#[derive(Debug, ToShmem)]
pub struct Keyframe {
    /// The selector this keyframe was specified from.
    pub selector: KeyframeSelector,

    /// The declaration block that was declared inside this keyframe.
    ///
    /// Note that `!important` rules in keyframes don't apply, but we keep this
    /// `Arc` just for convenience.
    pub block: Arc<Locked<PropertyDeclarationBlock>>,

    /// The line and column of the rule's source code.
    pub source_location: SourceLocation,
}

impl ToCssWithGuard for Keyframe {
    fn to_css(&self, guard: &SharedRwLockReadGuard, dest: &mut CssStringWriter) -> fmt::Result {
        self.selector.to_css(&mut CssWriter::new(dest))?;
        dest.write_str(" { ")?;
        self.block.read_with(guard).to_css(dest)?;
        dest.write_str(" }")?;
        Ok(())
    }
}

impl Keyframe {
    /// Parse a CSS keyframe.
    pub fn parse<'i>(
        css: &'i str,
        parent_stylesheet_contents: &StylesheetContents,
        lock: &SharedRwLock,
    ) -> Result<Arc<Locked<Self>>, ParseError<'i>> {
        let url_data = parent_stylesheet_contents.url_data.read();
        let namespaces = parent_stylesheet_contents.namespaces.read();
        let mut context = ParserContext::new(
            parent_stylesheet_contents.origin,
            &url_data,
            Some(CssRuleType::Keyframe),
            ParsingMode::DEFAULT,
            parent_stylesheet_contents.quirks_mode,
            Cow::Borrowed(&*namespaces),
            None,
            None,
        );
        let mut input = ParserInput::new(css);
        let mut input = Parser::new(&mut input);

        let mut rule_parser = KeyframeListParser {
            context: &mut context,
            shared_lock: &lock,
        };
        parse_one_rule(&mut input, &mut rule_parser)
    }
}

impl DeepCloneWithLock for Keyframe {
    /// Deep clones this Keyframe.
    fn deep_clone_with_lock(
        &self,
        lock: &SharedRwLock,
        guard: &SharedRwLockReadGuard,
    ) -> Keyframe {
        Keyframe {
            selector: self.selector.clone(),
            block: Arc::new(lock.wrap(self.block.read_with(guard).clone())),
            source_location: self.source_location.clone(),
        }
    }
}

/// A keyframes step value. This can be a synthetised keyframes animation, that
/// is, one autogenerated from the current computed values, or a list of
/// declarations to apply.
///
/// TODO: Find a better name for this?
#[derive(Clone, Debug, MallocSizeOf)]
pub enum KeyframesStepValue {
    /// A step formed by a declaration block specified by the CSS.
    Declarations {
        /// The declaration block per se.
        #[cfg_attr(
            feature = "gecko",
            ignore_malloc_size_of = "XXX: Primary ref, measure if DMD says it's worthwhile"
        )]
        #[cfg_attr(feature = "servo", ignore_malloc_size_of = "Arc")]
        block: Arc<Locked<PropertyDeclarationBlock>>,
    },
    /// A synthetic step computed from the current computed values at the time
    /// of the animation.
    ComputedValues,
}

/// A single step from a keyframe animation.
#[derive(Clone, Debug, MallocSizeOf)]
pub struct KeyframesStep {
    /// The percentage of the animation duration when this step starts.
    pub start_percentage: KeyframePercentage,
    /// Declarations that will determine the final style during the step, or
    /// `ComputedValues` if this is an autogenerated step.
    pub value: KeyframesStepValue,
    /// Whether an animation-timing-function declaration exists in the list of
    /// declarations.
    ///
    /// This is used to know when to override the keyframe animation style.
    pub declared_timing_function: bool,
    /// Whether an animation-composition declaration exists in the list of
    /// declarations.
    ///
    /// This is used to know when to override the keyframe animation style.
    pub declared_composition: bool,
}

impl KeyframesStep {
    #[inline]
    fn new(
        start_percentage: KeyframePercentage,
        value: KeyframesStepValue,
        guard: &SharedRwLockReadGuard,
    ) -> Self {
        let mut declared_timing_function = false;
        let mut declared_composition = false;
        if let KeyframesStepValue::Declarations { ref block } = value {
            for prop_decl in block.read_with(guard).declarations().iter() {
                match *prop_decl {
                    PropertyDeclaration::AnimationTimingFunction(..) => {
                        declared_timing_function = true;
                    },
                    PropertyDeclaration::AnimationComposition(..) => {
                        declared_composition = true;
                    },
                    _ => continue,
                }
                // Don't need to continue the loop if both are found.
                if declared_timing_function && declared_composition {
                    break;
                }
            }
        }

        KeyframesStep {
            start_percentage,
            value,
            declared_timing_function,
            declared_composition,
        }
    }

    /// Return specified PropertyDeclaration.
    #[inline]
    fn get_declared_property<'a>(
        &'a self,
        guard: &'a SharedRwLockReadGuard,
        property: LonghandId,
    ) -> Option<&'a PropertyDeclaration> {
        match self.value {
            KeyframesStepValue::Declarations { ref block } => {
                let guard = block.read_with(guard);
                let (declaration, _) = guard
                    .get(PropertyDeclarationId::Longhand(property))
                    .unwrap();
                match *declaration {
                    PropertyDeclaration::CSSWideKeyword(..) => None,
                    // FIXME: Bug 1710735: Support css variable in @keyframes rule.
                    PropertyDeclaration::WithVariables(..) => None,
                    _ => Some(declaration),
                }
            },
            KeyframesStepValue::ComputedValues => {
                panic!("Shouldn't happen to set this property in missing keyframes")
            },
        }
    }

    /// Return specified TransitionTimingFunction if this KeyframesSteps has
    /// 'animation-timing-function'.
    pub fn get_animation_timing_function(
        &self,
        guard: &SharedRwLockReadGuard,
    ) -> Option<SpecifiedTimingFunction> {
        if !self.declared_timing_function {
            return None;
        }

        self.get_declared_property(guard, LonghandId::AnimationTimingFunction)
            .map(|decl| {
                match *decl {
                    PropertyDeclaration::AnimationTimingFunction(ref value) => {
                        // Use the first value
                        value.0[0].clone()
                    },
                    _ => unreachable!("Unexpected PropertyDeclaration"),
                }
            })
    }

    /// Return CompositeOperation if this KeyframesSteps has 'animation-composition'.
    pub fn get_animation_composition(
        &self,
        guard: &SharedRwLockReadGuard,
    ) -> Option<SpecifiedComposition> {
        if !self.declared_composition {
            return None;
        }

        self.get_declared_property(guard, LonghandId::AnimationComposition)
            .map(|decl| {
                match *decl {
                    PropertyDeclaration::AnimationComposition(ref value) => {
                        // Use the first value
                        value.0[0].clone()
                    },
                    _ => unreachable!("Unexpected PropertyDeclaration"),
                }
            })
    }
}

/// This structure represents a list of animation steps computed from the list
/// of keyframes, in order.
///
/// It only takes into account animable properties.
#[derive(Clone, Debug, MallocSizeOf)]
pub struct KeyframesAnimation {
    /// The difference steps of the animation.
    pub steps: Vec<KeyframesStep>,
    /// The properties that change in this animation.
    pub properties_changed: PropertyDeclarationIdSet,
    /// Vendor prefix type the @keyframes has.
    pub vendor_prefix: Option<VendorPrefix>,
}

/// Get all the animated properties in a keyframes animation.
fn get_animated_properties(
    keyframes: &[Arc<Locked<Keyframe>>],
    guard: &SharedRwLockReadGuard,
) -> PropertyDeclarationIdSet {
    let mut ret = PropertyDeclarationIdSet::default();
    // NB: declarations are already deduplicated, so we don't have to check for
    // it here.
    for keyframe in keyframes {
        let keyframe = keyframe.read_with(&guard);
        let block = keyframe.block.read_with(guard);
        // CSS Animations spec clearly defines that properties with !important
        // in keyframe rules are invalid and ignored, but it's still ambiguous
        // whether we should drop the !important properties or retain the
        // properties when they are set via CSSOM. So we assume there might
        // be properties with !important in keyframe rules here.
        // See the spec issue https://github.com/w3c/csswg-drafts/issues/1824
        for declaration in block.normal_declaration_iter() {
            let declaration_id = declaration.id();

            if declaration_id == PropertyDeclarationId::Longhand(LonghandId::Display) {
                continue;
            }

            if !declaration_id.is_animatable() {
                continue;
            }

            ret.insert(declaration_id);
        }
    }

    ret
}

impl KeyframesAnimation {
    /// Create a keyframes animation from a given list of keyframes.
    ///
    /// This will return a keyframe animation with empty steps and
    /// properties_changed if the list of keyframes is empty, or there are no
    /// animated properties obtained from the keyframes.
    ///
    /// Otherwise, this will compute and sort the steps used for the animation,
    /// and return the animation object.
    pub fn from_keyframes(
        keyframes: &[Arc<Locked<Keyframe>>],
        vendor_prefix: Option<VendorPrefix>,
        guard: &SharedRwLockReadGuard,
    ) -> Self {
        let mut result = KeyframesAnimation {
            steps: vec![],
            properties_changed: PropertyDeclarationIdSet::default(),
            vendor_prefix,
        };

        if keyframes.is_empty() {
            return result;
        }

        result.properties_changed = get_animated_properties(keyframes, guard);
        if result.properties_changed.is_empty() {
            return result;
        }

        for keyframe in keyframes {
            let keyframe = keyframe.read_with(&guard);
            for percentage in keyframe.selector.0.iter() {
                result.steps.push(KeyframesStep::new(
                    *percentage,
                    KeyframesStepValue::Declarations {
                        block: keyframe.block.clone(),
                    },
                    guard,
                ));
            }
        }

        // Sort by the start percentage, so we can easily find a frame.
        result.steps.sort_by_key(|step| step.start_percentage);

        // Prepend autogenerated keyframes if appropriate.
        if result.steps[0].start_percentage.0 != 0. {
            result.steps.insert(
                0,
                KeyframesStep::new(
                    KeyframePercentage::new(0.),
                    KeyframesStepValue::ComputedValues,
                    guard,
                ),
            );
        }

        if result.steps.last().unwrap().start_percentage.0 != 1. {
            result.steps.push(KeyframesStep::new(
                KeyframePercentage::new(1.),
                KeyframesStepValue::ComputedValues,
                guard,
            ));
        }

        result
    }
}

/// Parses a keyframes list, like:
/// 0%, 50% {
///     width: 50%;
/// }
///
/// 40%, 60%, 100% {
///     width: 100%;
/// }
struct KeyframeListParser<'a, 'b> {
    context: &'a mut ParserContext<'b>,
    shared_lock: &'a SharedRwLock,
}

/// Parses a keyframe list from CSS input.
pub fn parse_keyframe_list<'a>(
    context: &mut ParserContext<'a>,
    input: &mut Parser,
    shared_lock: &SharedRwLock,
) -> Vec<Arc<Locked<Keyframe>>> {
    let mut parser = KeyframeListParser {
        context,
        shared_lock,
    };
    RuleBodyParser::new(input, &mut parser)
        .filter_map(Result::ok)
        .collect()
}

impl<'a, 'b, 'i> AtRuleParser<'i> for KeyframeListParser<'a, 'b> {
    type Prelude = ();
    type AtRule = Arc<Locked<Keyframe>>;
    type Error = StyleParseErrorKind<'i>;
}

impl<'a, 'b, 'i> DeclarationParser<'i> for KeyframeListParser<'a, 'b> {
    type Declaration = Arc<Locked<Keyframe>>;
    type Error = StyleParseErrorKind<'i>;
}

impl<'a, 'b, 'i> QualifiedRuleParser<'i> for KeyframeListParser<'a, 'b> {
    type Prelude = KeyframeSelector;
    type QualifiedRule = Arc<Locked<Keyframe>>;
    type Error = StyleParseErrorKind<'i>;

    fn parse_prelude<'t>(
        &mut self,
        input: &mut Parser<'i, 't>,
    ) -> Result<Self::Prelude, ParseError<'i>> {
        let start_position = input.position();
        KeyframeSelector::parse(input).map_err(|e| {
            let location = e.location;
            let error = ContextualParseError::InvalidKeyframeRule(
                input.slice_from(start_position),
                e.clone(),
            );
            self.context.log_css_error(location, error);
            e
        })
    }

    fn parse_block<'t>(
        &mut self,
        selector: Self::Prelude,
        start: &ParserState,
        input: &mut Parser<'i, 't>,
    ) -> Result<Self::QualifiedRule, ParseError<'i>> {
        let block = self.context.nest_for_rule(CssRuleType::Keyframe, |p| {
            parse_property_declaration_list(&p, input, &[])
        });
        Ok(Arc::new(self.shared_lock.wrap(Keyframe {
            selector,
            block: Arc::new(self.shared_lock.wrap(block)),
            source_location: start.source_location(),
        })))
    }
}

impl<'a, 'b, 'i> RuleBodyItemParser<'i, Arc<Locked<Keyframe>>, StyleParseErrorKind<'i>>
    for KeyframeListParser<'a, 'b>
{
    fn parse_qualified(&self) -> bool {
        true
    }
    fn parse_declarations(&self) -> bool {
        false
    }
}