Merge pull request #428 from brave/code_structure_2

Code structure follow up

src/filters/abstract_network.rs

@@ -0,0 +1,256 @@
+use memchr::memrchr as find_char_reverse;
+
+use super::network::NetworkFilterError;
+
+use once_cell::sync::Lazy;
+use regex::Regex;
+
+/// For now, only support `$removeparam` with simple alphanumeric/dash/underscore patterns.
+static VALID_PARAM: Lazy<Regex> = Lazy::new(|| Regex::new(r"^[a-zA-Z0-9_\-]+$").unwrap());
+
+#[derive(Clone, Copy)]
+pub(crate) enum NetworkFilterLeftAnchor {
+    /// A `||` token, which represents a match to the start of a domain or subdomain segment.
+    DoublePipe,
+    /// A `|` token, which represents a match to the exact start of the URL.
+    SinglePipe,
+}
+
+#[derive(Clone, Copy)]
+pub(crate) enum NetworkFilterRightAnchor {
+    /// A `|` token, which represents a match to the exact end of the URL.
+    SinglePipe,
+}
+
+/// Pattern for a network filter, describing what URLs to match against.
+#[derive(Clone)]
+pub(crate) struct NetworkFilterPattern {
+    pub(crate) left_anchor: Option<NetworkFilterLeftAnchor>,
+    pub(crate) pattern: String,
+    pub(crate) right_anchor: Option<NetworkFilterRightAnchor>,
+}
+
+/// Any option that appears on the right side of a network filter as initiated by a `$` character.
+/// All `bool` arguments below are `true` if the option stands alone, or `false` if the option is
+/// negated using a prepended `~`.
+#[derive(Clone)]
+pub(crate) enum NetworkFilterOption {
+    Domain(Vec<(bool, String)>),
+    Badfilter,
+    Important,
+    MatchCase,
+    ThirdParty(bool),
+    FirstParty(bool),
+    Tag(String),
+    Redirect(String),
+    RedirectRule(String),
+    Csp(Option<String>),
+    Removeparam(String),
+    Generichide,
+    Document,
+    Image(bool),
+    Media(bool),
+    Object(bool),
+    Other(bool),
+    Ping(bool),
+    Script(bool),
+    Stylesheet(bool),
+    Subdocument(bool),
+    XmlHttpRequest(bool),
+    Websocket(bool),
+    Font(bool),
+}
+
+impl NetworkFilterOption {
+    pub fn is_content_type(&self) -> bool {
+        matches!(
+            self,
+            Self::Document
+                | Self::Image(..)
+                | Self::Media(..)
+                | Self::Object(..)
+                | Self::Other(..)
+                | Self::Ping(..)
+                | Self::Script(..)
+                | Self::Stylesheet(..)
+                | Self::Subdocument(..)
+                | Self::XmlHttpRequest(..)
+                | Self::Websocket(..)
+                | Self::Font(..)
+        )
+    }
+
+    pub fn is_redirection(&self) -> bool {
+        matches!(self, Self::Redirect(..) | Self::RedirectRule(..))
+    }
+}
+
+/// Abstract syntax representation of a network filter. This representation can fully specify the
+/// string representation of a filter as written, with the exception of aliased options like `1p`
+/// or `ghide`. This allows separation of concerns between parsing and interpretation.
+pub(crate) struct AbstractNetworkFilter {
+    pub(crate) exception: bool,
+    pub(crate) pattern: NetworkFilterPattern,
+    pub(crate) options: Option<Vec<NetworkFilterOption>>,
+}
+
+impl AbstractNetworkFilter {
+    pub(crate) fn parse(line: &str) -> Result<Self, NetworkFilterError> {
+        let mut filter_index_start: usize = 0;
+        let mut filter_index_end: usize = line.len();
+
+        let mut exception = false;
+        if line.starts_with("@@") {
+            filter_index_start += 2;
+            exception = true;
+        }
+
+        let maybe_options_index: Option<usize> = find_char_reverse(b'$', line.as_bytes());
+
+        let mut options = None;
+        if let Some(options_index) = maybe_options_index {
+            filter_index_end = options_index;
+
+            // slicing here is safe; the first byte after '$' will be a character boundary
+            let raw_options = &line[filter_index_end + 1..];
+
+            options = Some(parse_filter_options(raw_options)?);
+        }
+
+        let left_anchor = if line[filter_index_start..].starts_with("||") {
+            filter_index_start += 2;
+            Some(NetworkFilterLeftAnchor::DoublePipe)
+        } else if line[filter_index_start..].starts_with('|') {
+            filter_index_start += 1;
+            Some(NetworkFilterLeftAnchor::SinglePipe)
+        } else {
+            None
+        };
+
+        let right_anchor = if filter_index_end > 0
+            && filter_index_end > filter_index_start
+            && line[..filter_index_end].ends_with('|')
+        {
+            filter_index_end -= 1;
+            Some(NetworkFilterRightAnchor::SinglePipe)
+        } else {
+            None
+        };
+
+        let pattern = &line[filter_index_start..filter_index_end];
+
+        Ok(AbstractNetworkFilter {
+            exception,
+            pattern: NetworkFilterPattern {
+                left_anchor,
+                pattern: pattern.to_string(),
+                right_anchor,
+            },
+            options,
+        })
+    }
+}
+
+fn parse_filter_options(raw_options: &str) -> Result<Vec<NetworkFilterOption>, NetworkFilterError> {
+    let mut result = vec![];
+
+    for raw_option in raw_options.split(',') {
+        // Check for negation: ~option
+        let negation = raw_option.starts_with('~');
+        let maybe_negated_option = raw_option.trim_start_matches('~');
+
+        // Check for options: option=value1|value2
+        let mut option_and_values = maybe_negated_option.splitn(2, '=');
+        let (option, value) = (
+            option_and_values.next().unwrap(),
+            option_and_values.next().unwrap_or_default(),
+        );
+
+        result.push(match (option, negation) {
+            ("domain", _) | ("from", _) => {
+                let domains: Vec<(bool, String)> = value
+                    .split('|')
+                    .map(|domain| {
+                        if let Some(negated_domain) = domain.strip_prefix('~') {
+                            (false, negated_domain.to_string())
+                        } else {
+                            (true, domain.to_string())
+                        }
+                    })
+                    .filter(|(_, d)| !(d.starts_with('/') && d.ends_with('/')))
+                    .collect();
+                if domains.is_empty() {
+                    return Err(NetworkFilterError::NoSupportedDomains);
+                }
+                NetworkFilterOption::Domain(domains)
+            }
+            ("badfilter", true) => return Err(NetworkFilterError::NegatedBadFilter),
+            ("badfilter", false) => NetworkFilterOption::Badfilter,
+            ("important", true) => return Err(NetworkFilterError::NegatedImportant),
+            ("important", false) => NetworkFilterOption::Important,
+            ("match-case", true) => return Err(NetworkFilterError::NegatedOptionMatchCase),
+            ("match-case", false) => NetworkFilterOption::MatchCase,
+            ("third-party", negated) | ("3p", negated) => NetworkFilterOption::ThirdParty(!negated),
+            ("first-party", negated) | ("1p", negated) => NetworkFilterOption::FirstParty(!negated),
+            ("tag", true) => return Err(NetworkFilterError::NegatedTag),
+            ("tag", false) => NetworkFilterOption::Tag(String::from(value)),
+            ("redirect", true) => return Err(NetworkFilterError::NegatedRedirection),
+            ("redirect", false) => {
+                // Ignore this filter if no redirection resource is specified
+                if value.is_empty() {
+                    return Err(NetworkFilterError::EmptyRedirection);
+                }
+
+                NetworkFilterOption::Redirect(String::from(value))
+            }
+            ("redirect-rule", true) => return Err(NetworkFilterError::NegatedRedirection),
+            ("redirect-rule", false) => {
+                if value.is_empty() {
+                    return Err(NetworkFilterError::EmptyRedirection);
+                }
+
+                NetworkFilterOption::RedirectRule(String::from(value))
+            }
+            ("csp", _) => NetworkFilterOption::Csp(if !value.is_empty() {
+                Some(String::from(value))
+            } else {
+                None
+            }),
+            ("removeparam", true) => return Err(NetworkFilterError::NegatedRemoveparam),
+            ("removeparam", false) => {
+                if value.is_empty() {
+                    return Err(NetworkFilterError::EmptyRemoveparam);
+                }
+                if !VALID_PARAM.is_match(value) {
+                    return Err(NetworkFilterError::RemoveparamRegexUnsupported);
+                }
+                NetworkFilterOption::Removeparam(String::from(value))
+            }
+            ("generichide", true) | ("ghide", true) => {
+                return Err(NetworkFilterError::NegatedGenericHide)
+            }
+            ("generichide", false) | ("ghide", false) => NetworkFilterOption::Generichide,
+            ("document", true) | ("doc", true) => return Err(NetworkFilterError::NegatedDocument),
+            ("document", false) | ("doc", false) => NetworkFilterOption::Document,
+            ("image", negated) => NetworkFilterOption::Image(!negated),
+            ("media", negated) => NetworkFilterOption::Media(!negated),
+            ("object", negated) | ("object-subrequest", negated) => {
+                NetworkFilterOption::Object(!negated)
+            }
+            ("other", negated) => NetworkFilterOption::Other(!negated),
+            ("ping", negated) | ("beacon", negated) => NetworkFilterOption::Ping(!negated),
+            ("script", negated) => NetworkFilterOption::Script(!negated),
+            ("stylesheet", negated) | ("css", negated) => NetworkFilterOption::Stylesheet(!negated),
+            ("subdocument", negated) | ("frame", negated) => {
+                NetworkFilterOption::Subdocument(!negated)
+            }
+            ("xmlhttprequest", negated) | ("xhr", negated) => {
+                NetworkFilterOption::XmlHttpRequest(!negated)
+            }
+            ("websocket", negated) => NetworkFilterOption::Websocket(!negated),
+            ("font", negated) => NetworkFilterOption::Font(!negated),
+            (_, _) => return Err(NetworkFilterError::UnrecognisedOption),
+        });
+    }
+    Ok(result)
+}

src/filters/mod.rs

@@ -1,4 +1,5 @@
 //! Contains representations and standalone behaviors of individual filter rules.
 
+mod abstract_network;
 pub mod cosmetic;
 pub mod network;