Build translations from mdbook

Cargo.toml

@@ -17,7 +17,9 @@ pulldown-cmark = { version = "0.9.2", default-features = false }
 pulldown-cmark-to-cmark = "10.0.4"
 regex = "1.9.4"
 semver = "1.0.16"
+serde = "1.0.130"
 serde_json = "1.0.91"
+toml = "0.5.8"
 
 [dev-dependencies]
 pretty_assertions = "1.3.0"

src/main.rs

@@ -0,0 +1,80 @@
+use mdbook::renderer::RenderContext;
+use serde::Deserialize;
+use std::collections::BTreeMap;
+use std::io;
+
+#[derive(Deserialize)]
+struct I18nConfiguration {
+    languages: BTreeMap<String, String>,
+    default_language: Option<String>,
+
+    #[serde(default)]
+    translate_all_languages: bool,
+    #[serde(default)]
+    move_translations_to_html_directory: bool,
+}
+
+fn main() {
+    let mut stdin = io::stdin();
+
+    // Get the configs
+    let ctx = RenderContext::from_json(&mut stdin).unwrap();
+    let i18n_config: I18nConfiguration = ctx
+        .config
+        .get_deserialized_opt("output.i18n-helpers")
+        .unwrap()
+        .unwrap();
+
+    if !i18n_config.translate_all_languages {
+        return;
+    }
+
+    let mut mdbook = mdbook::MDBook::load(&ctx.root).expect("Failed to load book");
+    // Overwrite with current values from stdin.
+    mdbook.book = ctx.book.clone();
+    mdbook.config = ctx.config.clone();
+    mdbook.root = ctx.root.clone();
+
+    let book_config = mdbook
+        .config
+        .get_mut("output.i18n-helpers")
+        .expect("No output.i18n-helpers config in book.toml");
+    // Set translate_all_languages to false for nested builds to prevent infinite recursion.
+    book_config
+        .as_table_mut()
+        .expect("output.i18n-helpers config in book.toml is not a table")
+        .insert(
+            String::from("translate_all_languages"),
+            toml::Value::Boolean(false),
+        );
+
+    let output_directory = ctx.destination.parent().unwrap();
+    let default_language = &i18n_config.default_language;
+
+    for language in i18n_config.languages.keys() {
+        // Skip current language and default language.
+        if Some(language) == ctx.config.book.language.as_ref() {
+            continue;
+        }
+        if let Some(default_language) = default_language {
+            if default_language == language {
+                continue;
+            }
+        }
+        let translation_path = output_directory.join(language);
+
+        // Book doesn't implement clone, so we just mutate in place.
+        mdbook.config.book.language = Some(language.clone());
+        mdbook.config.book.multilingual = true;
+        mdbook.config.build.build_dir = translation_path;
+        mdbook.build().unwrap_or_else(|_| panic!("Failed to build translation for language: {}",
+            language));
+        if i18n_config.move_translations_to_html_directory {
+            std::fs::rename(
+                output_directory.join(language).join("html"),
+                output_directory.join("html").join(language),
+            )
+            .unwrap_or_else(|_| panic!("Failed to move translation for language {language} to output directory"));
+        }
+    }
+}