Add topic parsing.

source/from_str.rs

@@ -4,12 +4,13 @@ use std::str::FromStr;
 
 use {duplicate::duplicate_item, scraper::Html};
 
-use crate::{Group, GroupList, ParseError};
+use crate::{Group, GroupList, ParseError, Topic};
 
 #[duplicate_item(
   _Struct;
   [Group];
   [GroupList];
+  [Topic];
 )]
 impl FromStr for _Struct {
   type Err = ParseError;

source/lib.rs

@@ -28,9 +28,11 @@ pub(crate) mod error;
 pub(crate) mod from_str;
 pub(crate) mod group;
 pub(crate) mod group_list;
+pub(crate) mod topic;
 
 pub use {
   error::*,
   group::{Group, GroupWikiLink},
   group_list::{GroupList, GroupListSummary},
+  topic::*,
 };

source/selectors.rs

@@ -28,4 +28,28 @@ lazy_static! {
 
   /// Selector for group wiki links.
   pub static ref GROUP_WIKI_LINKS: Selector = selector(r#"#sidebar [href*="/wiki/"]"#);
+
+  /// Selector for the topic comment count.
+  pub static ref TOPIC_COMMENT_COUNT: Selector = selector(".topic-comments-header h2");
+
+  /// Selector for the topic full byline.
+  pub static ref TOPIC_FULL_BYLINE: Selector = selector(".topic-full-byline");
+
+  /// Selector for a link topic's content.
+  pub static ref TOPIC_FULL_LINK: Selector = selector(".topic-full-link a");
+
+  /// Selector for the topic tag elements.
+  pub static ref TOPIC_FULL_TAGS: Selector = selector(".topic-full-tags a");
+
+  /// Selector for a text topic's content.
+  pub static ref TOPIC_FULL_TEXT: Selector = selector(".topic-full-text");
+
+  /// Selector for the main topic `<article>`.
+  pub static ref TOPIC_MAIN_ARTICLE: Selector = selector("main > .topic-full");
+
+  /// Selector for a topic toast warning.
+  pub static ref TOPIC_TOAST_WARNING: Selector = selector(".toast.toast-warning");
+
+  /// Selector for the topic vote count.
+  pub static ref TOPIC_VOTE_COUNT: Selector = selector(".topic-voting-votes");
 }

source/topic.rs

@@ -0,0 +1,170 @@
+//! Parsing for `/~<group>/<topic-id>`.
+
+use scraper::Html;
+
+use crate::{
+  regexes::DUPLICATE_WHITESPACE_RE,
+  selectors::{
+    TOPIC_COMMENT_COUNT, TOPIC_FULL_BYLINE, TOPIC_FULL_LINK, TOPIC_FULL_TAGS,
+    TOPIC_FULL_TEXT, TOPIC_MAIN_ARTICLE, TOPIC_TOAST_WARNING, TOPIC_VOTE_COUNT,
+  },
+  utilities::select_first_element_text,
+  ParseError,
+};
+
+/// A Tildes topic.
+#[derive(Debug)]
+pub struct Topic {
+  /// The name of the author.
+  pub author: TopicAuthor,
+
+  /// The amount of comments the topic has. Comments themselves have to be
+  /// parsed separately.
+  pub comment_total: i32,
+
+  /// The content of the topic.
+  pub content: TopicContent,
+
+  /// The unique ID of the topic.
+  pub id: String,
+
+  /// Whether the topic is locked.
+  pub is_locked: bool,
+
+  /// Whether the topic is official (not yet implemented, is always false).
+  ///
+  /// TODO: Add is_official. This isn't possible right now because topics don't
+  /// have any indicator of being marked as official. The only place it's shown
+  /// is in the topic listing. See #787 in the Tildes issue tracker.
+  pub is_official: bool,
+
+  /// All tags applied to the topic.
+  pub tags: Vec<String>,
+
+  /// The amount of votes the topic has received.
+  pub vote_count: i32,
+}
+
+/// All the different ways a topic author can be represented.
+#[derive(Debug)]
+pub enum TopicAuthor {
+  /// The normal case, where the topic author is available.
+  Name(String),
+
+  /// The topic was posted by Tildes itself.
+  ///
+  /// Technically the user for this is [Tildes](https://tildes.net/user/tildes)
+  /// but in the topic it says "Automatically posted <date>" where the username
+  /// normally goes, so may as well special-case it here too.
+  Scheduled,
+
+  /// The user was banned, deleted their account or disassociated the topic from
+  /// their account.
+  Unknown,
+}
+
+/// The different types of content a topic can have.
+#[derive(Debug)]
+pub enum TopicContent {
+  /// The topic is a link topic pointing to an external site.
+  Link(String),
+
+  /// The topic is a text topic with a HTML body.
+  Text(String),
+
+  /// The topic's content is no longer available.
+  Unknown,
+}
+
+impl Topic {
+  /// Parses a [`Topic`] from a [`scraper::Html`] tree.
+  pub fn from_html(html: &Html) -> Result<Self, ParseError> {
+    let topic_article_element = html
+      .select(&TOPIC_MAIN_ARTICLE)
+      .next()
+      .ok_or(ParseError::MissingExpectedHtml)?;
+
+    let topic_byline =
+      select_first_element_text(topic_article_element, &TOPIC_FULL_BYLINE)
+        .map(|byline| {
+          DUPLICATE_WHITESPACE_RE
+            .replace_all(&byline, " ")
+            .to_string()
+        })
+        .ok_or(ParseError::MissingExpectedHtml)?;
+
+    let author = if topic_byline.starts_with("Automatically posted") {
+      TopicAuthor::Scheduled
+    } else if topic_byline.ends_with("unknown user") {
+      TopicAuthor::Unknown
+    } else {
+      TopicAuthor::Name(
+        topic_byline
+          .split(" ")
+          .last()
+          .ok_or(ParseError::MissingExpectedHtml)?
+          .to_string(),
+      )
+    };
+
+    let comment_total = if let Some(comment_total) =
+      select_first_element_text(topic_article_element, &TOPIC_COMMENT_COUNT)
+    {
+      comment_total
+        .split(" ")
+        .next()
+        .map(|count| count.parse::<i32>())
+        .ok_or(ParseError::MissingExpectedHtml)?
+        .map_err(|_| ParseError::MissingExpectedHtml)?
+    } else {
+      0
+    };
+
+    let content = if let Some(link_content) =
+      topic_article_element.select(&TOPIC_FULL_LINK).next()
+    {
+      TopicContent::Link(link_content.text().collect::<String>())
+    } else if let Some(text_content) =
+      topic_article_element.select(&TOPIC_FULL_TEXT).next()
+    {
+      TopicContent::Text(text_content.inner_html().trim().to_string())
+    } else {
+      TopicContent::Unknown
+    };
+
+    let id = topic_article_element
+      .value()
+      .id()
+      .ok_or(ParseError::MissingExpectedHtml)?[6..]
+      .to_string();
+
+    let is_locked =
+      select_first_element_text(topic_article_element, &TOPIC_TOAST_WARNING)
+        .map(|toast| toast.contains("This topic is locked."))
+        .unwrap_or_default();
+
+    let tags = topic_article_element
+      .select(&TOPIC_FULL_TAGS)
+      .map(|tag| tag.text().collect::<String>())
+      .collect::<Vec<_>>();
+
+    let vote_count =
+      select_first_element_text(topic_article_element, &TOPIC_VOTE_COUNT)
+        .map(|vote_count| vote_count.parse::<i32>())
+        .ok_or(ParseError::MissingExpectedHtml)?
+        .map_err(|_| ParseError::MissingExpectedHtml)?;
+
+    let topic = Topic {
+      author,
+      comment_total,
+      content,
+      id,
+      is_locked,
+      is_official: false, // TODO: Implement this once it can be done.
+      tags,
+      vote_count,
+    };
+
+    Ok(topic)
+  }
+}