Implement push rule evaluation in Rust. (#13838)

rust/src/push/utils.rs

@@ -0,0 +1,215 @@
+// Copyright 2022 The Matrix.org Foundation C.I.C.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+use anyhow::bail;
+use anyhow::Context;
+use anyhow::Error;
+use lazy_static::lazy_static;
+use regex;
+use regex::Regex;
+use regex::RegexBuilder;
+
+lazy_static! {
+    /// Matches runs of non-wildcard characters followed by wildcard characters.
+    static ref WILDCARD_RUN: Regex = Regex::new(r"([^\?\*]*)([\?\*]*)").expect("valid regex");
+}
+
+/// Extract the localpart from a Matrix style ID
+pub(crate) fn get_localpart_from_id(id: &str) -> Result<&str, Error> {
+    let (localpart, _) = id
+        .split_once(':')
+        .with_context(|| format!("ID does not contain colon: {id}"))?;
+
+    // We need to strip off the first character, which is the ID type.
+    if localpart.is_empty() {
+        bail!("Invalid ID {id}");
+    }
+
+    Ok(&localpart[1..])
+}
+
+/// Used by `glob_to_regex` to specify what to match the regex against.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum GlobMatchType {
+    /// The generated regex will match against the entire input.
+    Whole,
+    /// The generated regex will match against words.
+    Word,
+}
+
+/// Convert a "glob" style expression to a regex, anchoring either to the entire
+/// input or to individual words.
+pub fn glob_to_regex(glob: &str, match_type: GlobMatchType) -> Result<Regex, Error> {
+    let mut chunks = Vec::new();
+
+    // Patterns with wildcards must be simplified to avoid performance cliffs
+    // - The glob `?**?**?` is equivalent to the glob `???*`
+    // - The glob `???*` is equivalent to the regex `.{3,}`
+    for captures in WILDCARD_RUN.captures_iter(glob) {
+        if let Some(chunk) = captures.get(1) {
+            chunks.push(regex::escape(chunk.as_str()));
+        }
+
+        if let Some(wildcards) = captures.get(2) {
+            if wildcards.as_str() == "" {
+                continue;
+            }
+
+            let question_marks = wildcards.as_str().chars().filter(|c| *c == '?').count();
+
+            if wildcards.as_str().contains('*') {
+                chunks.push(format!(".{{{question_marks},}}"));
+            } else {
+                chunks.push(format!(".{{{question_marks}}}"));
+            }
+        }
+    }
+
+    let joined = chunks.join("");
+
+    let regex_str = match match_type {
+        GlobMatchType::Whole => format!(r"\A{joined}\z"),
+
+        // `^|\W` and `\W|$` handle the case where `pattern` starts or ends with a non-word
+        // character.
+        GlobMatchType::Word => format!(r"(?:^|\b|\W){joined}(?:\b|\W|$)"),
+    };
+
+    Ok(RegexBuilder::new(&regex_str)
+        .case_insensitive(true)
+        .build()?)
+}
+
+/// Compiles the glob into a `Matcher`.
+pub fn get_glob_matcher(glob: &str, match_type: GlobMatchType) -> Result<Matcher, Error> {
+    // There are a number of shortcuts we can make if the glob doesn't contain a
+    // wild card.
+    let matcher = if glob.contains(['*', '?']) {
+        let regex = glob_to_regex(glob, match_type)?;
+        Matcher::Regex(regex)
+    } else if match_type == GlobMatchType::Whole {
+        // If there aren't any wildcards and we're matching the whole thing,
+        // then we simply can do a case-insensitive string match.
+        Matcher::Whole(glob.to_lowercase())
+    } else {
+        // Otherwise, if we're matching against words then can first check
+        // if the haystack contains the glob at all.
+        Matcher::Word {
+            word: glob.to_lowercase(),
+            regex: None,
+        }
+    };
+
+    Ok(matcher)
+}
+
+/// Matches against a glob
+pub enum Matcher {
+    /// Plain regex matching.
+    Regex(Regex),
+
+    /// Case-insensitive equality.
+    Whole(String),
+
+    /// Word matching. `regex` is a cache of calling [`glob_to_regex`] on word.
+    Word { word: String, regex: Option<Regex> },
+}
+
+impl Matcher {
+    /// Checks if the glob matches the given haystack.
+    pub fn is_match(&mut self, haystack: &str) -> Result<bool, Error> {
+        // We want to to do case-insensitive matching, so we convert to
+        // lowercase first.
+        let haystack = haystack.to_lowercase();
+
+        match self {
+            Matcher::Regex(regex) => Ok(regex.is_match(&haystack)),
+            Matcher::Whole(whole) => Ok(whole == &haystack),
+            Matcher::Word { word, regex } => {
+                // If we're looking for a literal word, then we first check if
+                // the haystack contains the word as a substring.
+                if !haystack.contains(&*word) {
+                    return Ok(false);
+                }
+
+                // If it does contain the word as a substring, then we need to
+                // check if it is an actual word by testing it against the regex.
+                let regex = if let Some(regex) = regex {
+                    regex
+                } else {
+                    let compiled_regex = glob_to_regex(word, GlobMatchType::Word)?;
+                    regex.insert(compiled_regex)
+                };
+
+                Ok(regex.is_match(&haystack))
+            }
+        }
+    }
+}
+
+#[test]
+fn test_get_domain_from_id() {
+    get_localpart_from_id("").unwrap_err();
+    get_localpart_from_id(":").unwrap_err();
+    get_localpart_from_id(":asd").unwrap_err();
+    get_localpart_from_id("::as::asad").unwrap_err();
+
+    assert_eq!(get_localpart_from_id("@test:foo").unwrap(), "test");
+    assert_eq!(get_localpart_from_id("@:").unwrap(), "");
+    assert_eq!(get_localpart_from_id("@test:foo:907").unwrap(), "test");
+}
+
+#[test]
+fn tset_glob() -> Result<(), Error> {
+    assert_eq!(
+        glob_to_regex("simple", GlobMatchType::Whole)?.as_str(),
+        r"\Asimple\z"
+    );
+    assert_eq!(
+        glob_to_regex("simple*", GlobMatchType::Whole)?.as_str(),
+        r"\Asimple.{0,}\z"
+    );
+    assert_eq!(
+        glob_to_regex("simple?", GlobMatchType::Whole)?.as_str(),
+        r"\Asimple.{1}\z"
+    );
+    assert_eq!(
+        glob_to_regex("simple?*?*", GlobMatchType::Whole)?.as_str(),
+        r"\Asimple.{2,}\z"
+    );
+    assert_eq!(
+        glob_to_regex("simple???", GlobMatchType::Whole)?.as_str(),
+        r"\Asimple.{3}\z"
+    );
+
+    assert_eq!(
+        glob_to_regex("escape.", GlobMatchType::Whole)?.as_str(),
+        r"\Aescape\.\z"
+    );
+
+    assert!(glob_to_regex("simple", GlobMatchType::Whole)?.is_match("simple"));
+    assert!(!glob_to_regex("simple", GlobMatchType::Whole)?.is_match("simples"));
+    assert!(glob_to_regex("simple*", GlobMatchType::Whole)?.is_match("simples"));
+    assert!(glob_to_regex("simple?", GlobMatchType::Whole)?.is_match("simples"));
+    assert!(glob_to_regex("simple*", GlobMatchType::Whole)?.is_match("simple"));
+
+    assert!(glob_to_regex("simple", GlobMatchType::Word)?.is_match("some simple."));
+    assert!(glob_to_regex("simple", GlobMatchType::Word)?.is_match("simple"));
+    assert!(!glob_to_regex("simple", GlobMatchType::Word)?.is_match("simples"));
+
+    assert!(glob_to_regex("@user:foo", GlobMatchType::Word)?.is_match("Some @user:foo test"));
+    assert!(glob_to_regex("@user:foo", GlobMatchType::Word)?.is_match("@user:foo"));
+
+    Ok(())
+}