Change Serials to UUIDs, fix translation table

Languages now refer to other languages they are translated to through
an additional table rather than an array of identifiers. This ensures
no orphan identifier remains when a language is deleted.

The primary key of languages is now a unique identifier rather than
the name of the language itself. It now allows for multiple languages
to have the same name. Their unique identifier is now a v4 UUID.

Set Diesel to specific version 2.0.2, since 2.0 apparently does not
mean the latest version of 2.0.z and 2.0 has issues with its uuid
feature.

Cleanup and simplify some code.

Some more GraphQL documentation on available queries.

src/db/models/languages.rs

@@ -3,10 +3,12 @@ use diesel::prelude::*;
 use juniper::GraphQLEnum;
 use tracing::info;
 
+use uuid::Uuid;
+
 use super::super::schema;
 use super::users::User;
 
-use schema::{langandagents, languages};
+use schema::{langandagents, langtranslatesto, languages};
 
 #[derive(
     diesel_derive_enum::DbEnum, Debug, Clone, PartialEq, Eq, GraphQLEnum,
@@ -43,12 +45,12 @@ pub enum AgentLanguageRelation {
     Author,
 }
 
-#[derive(Queryable, Insertable, Debug, Clone, PartialEq, Eq)]
+#[derive(Queryable, Insertable, Debug, Clone)]
 pub struct Language {
+    id: Uuid,
     name: String,
     native: Option<String>,
     release: Release,
-    targetlanguage: Vec<Option<String>>,
     genre: Vec<Option<DictGenre>>,
     abstract_: Option<String>,
     created: chrono::NaiveDateTime,
@@ -67,7 +69,7 @@ impl Language {
         use schema::langandagents::dsl;
         match &mut context.conn() {
             Ok(conn) => dsl::langandagents
-                .filter(dsl::language.eq(self.name.clone()))
+                .filter(dsl::language.eq(self.id))
                 .filter(dsl::relationship.eq(relationship))
                 .load::<LangAndAgent>(conn)
                 .unwrap()
@@ -97,6 +99,11 @@ impl Language {
 
 #[juniper::graphql_object(Context = Database)]
 impl Language {
+    #[graphql(description = "Unique identifier of the language")]
+    fn id(&self) -> String {
+        self.id.to_string()
+    }
+
     #[graphql(
         description = "Name in the main target language (often English) of the described language"
     )]
@@ -119,23 +126,16 @@ impl Language {
         description = "Languages in which the current language is translated"
     )]
     fn target_language(&self, context: &Database) -> Vec<Language> {
-        use schema::languages::dsl;
+        use schema::langtranslatesto::dsl;
         match &mut context.conn() {
-            Ok(conn) => self
-                .targetlanguage
-                .clone()
+            Ok(conn) => dsl::langtranslatesto
+                .filter(dsl::langfrom.eq(self.id))
+                .load::<LangTranslatesTo>(conn)
+                .unwrap()
                 .into_iter()
-                .flatten()
-                .map(|l| dsl::languages.find(l).first::<Language>(conn))
-                .filter_map(|l| match l {
-                    Ok(language) => Some(language),
-                    Err(e) => {
-                        info!(
-                            "Failed to retrieve language from database: {:?}",
-                            e
-                        );
-                        None
-                    }
+                .flat_map(|l| {
+                    use schema::languages::dsl;
+                    dsl::languages.find(l.langto).first::<Language>(conn)
                 })
                 .collect::<Vec<Language>>(),
             Err(e) => {
@@ -223,6 +223,14 @@ impl Language {
 pub struct LangAndAgent {
     id: i32,
     agent: String,
-    language: String,
+    language: Uuid,
     relationship: AgentLanguageRelation,
 }
+
+#[derive(Queryable, Insertable, Debug, Clone, PartialEq, Eq)]
+#[diesel(table_name = langtranslatesto)]
+pub struct LangTranslatesTo {
+    id: i32,
+    langfrom: Uuid,
+    langto: Uuid,
+}