Convert messages to Matrix's HTML format

Cargo.lock

@@ -848,6 +848,15 @@ dependencies = [
  "digest",
 ]
 
+[[package]]
+name = "html-escape"
+version = "0.2.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "816ea801a95538fc5f53c836697b3f8b64a9d664c4f0b91efe1fe7c92e4dbcb7"
+dependencies = [
+ "utf8-width",
+]
+
 [[package]]
 name = "http"
 version = "0.2.4"
@@ -1487,6 +1496,7 @@ dependencies = [
  "bincode",
  "discord_message_format",
  "env_logger",
+ "html-escape",
  "log",
  "matrix-sdk",
  "serde",
@@ -2811,6 +2821,12 @@ version = "0.7.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "09cc8ee72d2a9becf2f2febe0205bbed8fc6615b7cb429ad062dc7b7ddd036a9"
 
+[[package]]
+name = "utf8-width"
+version = "0.1.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7cf7d77f457ef8dfa11e4cd5933c5ddb5dc52a94664071951219a97710f0a32b"
+
 [[package]]
 name = "uuid"
 version = "0.8.2"

Cargo.toml

@@ -13,6 +13,7 @@ tokio = { version = "1.10.1", features = ["full"] }
 url = "2.2.2"
 log = "0.4.14"
 env_logger = "0.9.0"
+html-escape = "0.2.9"
 
 [dependencies.serenity]
 version = "0.10.9"

src/matrix.rs

@@ -20,7 +20,7 @@ use tokio::sync::mpsc;
 use url::Url;
 
 use crate::{
-    message_ast::{convert_plain, format_discord},
+    message_ast::{convert_plain, format_discord, format_matrix},
     messages::{MessageAuthor, MessageReference, SentMessage},
 };
 
@@ -131,10 +131,9 @@ pub async fn forward_to_matrix(
     if let Some(room) = client.get_joined_room(&room_id) {
         let event = room
             .send(
-                AnyMessageEventContent::RoomMessage(MessageEventContent::text_plain(
-                    format_discord(
-                        &message.content, // TODO: Format as HTML
-                    ),
+                AnyMessageEventContent::RoomMessage(MessageEventContent::text_html(
+                    format_discord(&message.content),
+                    format_matrix(&message.content),
                 )),
                 None,
             )

src/message_ast/convert_matrix.rs

@@ -0,0 +1,51 @@
+use super::{MessageContent, Styled};
+
+pub fn convert_matrix(message: &str) -> MessageContent {
+    todo!();
+}
+
+pub fn format_matrix(message_content: &MessageContent) -> String {
+    message_content
+        .iter()
+        .map(|component| match component {
+            Styled::Plain(text) => html_escape::encode_text(text).to_string(),
+            Styled::Link { target, text } => format!(
+                r#"<a href="{}">{}</a>"#,
+                html_escape::encode_quoted_attribute(target),
+                format_matrix(text)
+            ),
+
+            Styled::Italic(inner) => format!("<em>{}</em>", format_matrix(inner)),
+            Styled::Bold(inner) => format!("<strong>{}</strong>", format_matrix(inner)),
+            Styled::Strikethrough(inner) => format!("<del>{}</del>", format_matrix(inner)),
+            Styled::Underline(inner) => format!("<u>{}</u>", format_matrix(inner)),
+
+            Styled::Code(code) => format!("<code>{}</code>", html_escape::encode_text(code)),
+            Styled::CodeBlock { lang, source } => {
+                format!(
+                    r#"<pre><code{}>{}</code></pre>"#,
+                    lang.as_ref()
+                        .map(|lang| format!(
+                            r#" class="language-{}""#,
+                            html_escape::encode_quoted_attribute(lang)
+                        ))
+                        .unwrap_or("".to_string()),
+                    source,
+                )
+            }
+
+            Styled::Spoiler { reason, content } => format!(
+                "<span data-mx-spoiler{}>{}</span>",
+                reason
+                    .as_ref()
+                    .map(|reason| format!(r#"="{}""#, html_escape::encode_quoted_attribute(reason)))
+                    .unwrap_or("".to_string()),
+                format_matrix(content)
+            ),
+            Styled::HardBreak => "<br>".to_string(),
+            Styled::BlockQuote(inner) => {
+                format!("<blockquote>{}</blockquote>", format_matrix(inner))
+            }
+        })
+        .collect()
+}

src/message_ast/mod.rs

@@ -1,4 +1,5 @@
 mod convert_discord;
+mod convert_matrix;
 mod convert_plain;
 
 pub type MessageContent = Vec<Styled>;
@@ -31,4 +32,5 @@ pub enum Styled {
 }
 
 pub use convert_discord::{convert_discord, format_discord};
+pub use convert_matrix::{convert_matrix, format_matrix};
 pub use convert_plain::convert_plain;