feat: strip prefixes and suffixes in links (#5486)

src/common/LinkParser.hpp

@@ -4,43 +4,126 @@
 
 #include <optional>
 
-namespace chatterino {
+namespace chatterino::linkparser {
 
-struct ParsedLink {
+/// @brief Represents a parsed link
+///
+/// A parsed link is represented as views over the source string for its
+/// different segments. In this simplified model, a link consists of an optional
+/// @a protocol, a mandatory @a host and an optional @a rest. These segments are
+/// always next to eachother in the input string, however together, they don't
+/// span the whole input as it could contain prefixes or suffixes.
+///
+/// Prefixes and suffixes are almost identical to the ones in GitHub Flavored
+/// Markdown (GFM - https://github.github.com/gfm/#autolinks-extension-).
+/// The main differences are that '_' isn't a valid suffix and parentheses
+/// aren't counted (e.g. "(a.com/(foo)! would result in "a.com/(foo").
+/// Matching is done case insensitive (e.g. "HTTp://a.com" would be valid).
+///
+/// A @a protocol can either be empty, "http://", or "https://".
+/// A @a host can either be an IPv4 address or a hostname. The hostname must end
+/// in a valid top level domain. Otherwise, there are no restrictions on it.
+/// The @a rest can start with an optional port followed by either a '/', '?',
+/// or '#'.
+///
+/// @b Example
+///
+/// ```text
+/// (https://wiki.chatterino.com/Help/#overview)
+/// ▏▏proto ▕       host        ▏     rest     ▏▏
+/// ▏▏                link                     ▏▏
+/// ▏                source                     ▏
+/// ```
+struct Parsed {
     /// The parsed protocol of the link. Can be empty.
     ///
+    /// ```text
     /// https://www.forsen.tv/commands
-    /// ^------^
+    /// ▏╌╌╌╌╌╌▕
+    ///
+    /// www.forsen.tv/commands
+    /// (empty)
+    /// ```
     QStringView protocol;
 
     /// The parsed host of the link. Can not be empty.
     ///
+    /// ```text
     /// https://www.forsen.tv/commands
-    ///         ^-----------^
+    ///         ▏╌╌╌╌╌╌╌╌╌╌╌▕
+    /// ```
     QStringView host;
 
     /// The remainder of the link. Can be empty.
     ///
+    /// ```text
     /// https://www.forsen.tv/commands
-    ///                      ^-------^
+    ///                      ▏╌╌╌╌╌╌╌▕
+    ///
+    /// https://www.forsen.tv
+    /// (empty)
+    /// ```
     QStringView rest;
 
-    /// The original unparsed link.
+    /// The matched link. Can not be empty.
+    ///
+    /// ```text
+    /// (https://www.forsen.tv/commands)
+    ///  ▏╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌▕
+    /// ```
+    QStringView link;
+
+    /// Checks if the parsed link contains a prefix
+    bool hasPrefix(const QString &source) const noexcept
+    {
+        return this->link.begin() != source.begin();
+    }
+
+    /// The prefix before the parsed link inside @a source. May be empty.
+    ///
+    /// ```text
+    /// (https://www.forsen.tv/commands)
+    /// ^
     ///
     /// https://www.forsen.tv/commands
-    /// ^----------------------------^
-    QString source;
+    /// (empty)
+    /// ```
+    QStringView prefix(const QString &source) const noexcept
+    {
+        return {source.data(), this->link.begin()};
+    }
+
+    /// Checks if the parsed link contains a suffix
+    bool hasSuffix(const QString &source) const noexcept
+    {
+        return this->link.end() != source.end();
+    }
+
+    /// The suffix after the parsed link inside @a source. May be empty.
+    ///
+    /// ```text
+    /// (https://www.forsen.tv/commands)
+    ///                                ^
+    ///
+    /// https://www.forsen.tv/commands
+    /// (empty)
+    /// ```
+    QStringView suffix(const QString &source) const noexcept
+    {
+        return {
+            this->link.begin() + this->link.size(),
+            source.data() + source.length(),
+        };
+    }
 };
 
-class LinkParser
-{
-public:
-    explicit LinkParser(const QString &unparsedString);
+/// @brief Parses a link from @a source into its segments
+///
+/// If no link is contained in @a source, `std::nullopt` will be returned.
+/// The returned value is valid as long as @a source exists, as it contains
+/// views into @a source.
+///
+/// For the accepted links, see Parsed.
+std::optional<Parsed> parse(const QString &source) noexcept;
 
-    const std::optional<ParsedLink> &result() const;
-
-private:
-    std::optional<ParsedLink> result_{};
-};
-
-}  // namespace chatterino
+}  // namespace chatterino::linkparser