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//! The `@media` rule.

use super::Location;
use super::{CssRuleList, MinifyContext};
use crate::error::{MinifyError, PrinterError};
use crate::media_query::MediaList;
use crate::printer::Printer;
use crate::rules::{StyleContext, ToCssWithContext};
use crate::traits::ToCss;

/// A [@media](https://drafts.csswg.org/css-conditional-3/#at-media) rule.
#[derive(Debug, PartialEq, Clone)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct MediaRule<'i> {
  /// The media query list.
  #[cfg_attr(feature = "serde", serde(borrow))]
  pub query: MediaList<'i>,
  /// The rules within the `@media` rule.
  pub rules: CssRuleList<'i>,
  /// The location of the rule in the source file.
  pub loc: Location,
}

impl<'i> MediaRule<'i> {
  pub(crate) fn minify(
    &mut self,
    context: &mut MinifyContext<'_, 'i>,
    parent_is_unused: bool,
  ) -> Result<bool, MinifyError> {
    self.rules.minify(context, parent_is_unused)?;

    if let Some(custom_media) = &context.custom_media {
      self.query.transform_custom_media(self.loc, custom_media)?;
    }

    Ok(self.rules.0.is_empty() || self.query.never_matches())
  }
}

impl<'a, 'i> ToCssWithContext<'a, 'i> for MediaRule<'i> {
  fn to_css_with_context<W>(
    &self,
    dest: &mut Printer<W>,
    context: Option<&StyleContext<'a, 'i>>,
  ) -> Result<(), PrinterError>
  where
    W: std::fmt::Write,
  {
    // If the media query always matches, we can just output the nested rules.
    if dest.minify && self.query.always_matches() {
      self.rules.to_css_with_context(dest, context)?;
      return Ok(());
    }

    dest.add_mapping(self.loc);
    dest.write_str("@media ")?;
    self.query.to_css(dest)?;
    dest.whitespace()?;
    dest.write_char('{')?;
    dest.indent();
    dest.newline()?;
    self.rules.to_css_with_context(dest, context)?;
    dest.dedent();
    dest.newline()?;
    dest.write_char('}')
  }
}