Canonicalize login and channel names.

Canonicalization does two things:

* It prevents duplicate names that differ only by case or only by normalization/encoding sequence; and
* It makes certain name-based comparisons "case-insensitive" (generalizing via Unicode's case-folding rules).

This change is complicated, as it means that every name now needs to be stored in two forms. Unfortunately, this is _very likely_ a breaking schema change. The migrations in this commit perform a best-effort attempt to canonicalize existing channel or login names, but it's likely any existing channels or logins with non-ASCII characters will not be canonicalize correctly. Since clients look at all channel names and all login names on boot, and since the code in this commit verifies canonicalization when reading from the database, this will effectively make the server un-usuable until any incorrectly-canonicalized values are either manually canonicalized, or removed

It might be possible to do better with [the `icu` sqlite3 extension][icu], but (a) I'm not convinced of that and (b) this commit is already huge; adding database extension support would make it far larger.

[icu]: https://sqlite.org/src/dir/ext/icu

For some references on why it's worth storing usernames this way, see <https://www.b-list.org/weblog/2018/nov/26/case/> and the refernced talk, as well as <https://www.b-list.org/weblog/2018/feb/11/usernames/>. Bennett's treatment of this issue is, to my eye, much more readable than the referenced Unicode technical reports, and I'm inclined to trust his opinion given that he maintains a widely-used, internet-facing user registration library for Django.

1 files changed, 134 insertions, 78 deletions

diff --git a/src/channel/repo.rs b/src/channel/repo.rs
index 3353bfd..4baa95b 100644
--- a/src/channel/repo.rs
+++ b/src/channel/repo.rs
@@ -1,9 +1,12 @@
+use futures::stream::{StreamExt as _, TryStreamExt as _};
 use sqlx::{sqlite::Sqlite, SqliteConnection, Transaction};
 
 use crate::{
-    channel::{Channel, History, Id, Name},
+    channel::{Channel, History, Id},
     clock::DateTime,
+    db::NotFound,
     event::{Instant, ResumePoint, Sequence},
+    name::{self, Name},
 };
 
 pub trait Provider {
@@ -21,132 +24,160 @@ pub struct Channels<'t>(&'t mut SqliteConnection);
 impl<'c> Channels<'c> {
     pub async fn create(&mut self, name: &Name, created: &Instant) -> Result<History, sqlx::Error> {
         let id = Id::generate();
-        let channel = sqlx::query!(
+        let name = name.clone();
+        let display_name = name.display();
+        let canonical_name = name.canonical();
+        let created = *created;
+
+        sqlx::query!(
             r#"
                 insert
-                into channel (id, name, created_at, created_sequence)
-                values ($1, $2, $3, $4)
-                returning
-                    id as "id: Id",
-                    name as "name!: Name", -- known non-null as we just set it
-                    created_at as "created_at: DateTime",
-                    created_sequence as "created_sequence: Sequence"
+                into channel (id, created_at, created_sequence)
+                values ($1, $2, $3)
             "#,
             id,
-            name,
             created.at,
             created.sequence,
         )
-        .map(|row| History {
+        .execute(&mut *self.0)
+        .await?;
+
+        sqlx::query!(
+            r#"
+                insert into channel_name (id, display_name, canonical_name)
+                values ($1, $2, $3)
+            "#,
+            id,
+            display_name,
+            canonical_name,
+        )
+        .execute(&mut *self.0)
+        .await?;
+
+        let channel = History {
             channel: Channel {
-                id: row.id,
-                name: row.name,
+                id,
+                name: name.clone(),
                 deleted_at: None,
             },
-            created: Instant::new(row.created_at, row.created_sequence),
+            created,
             deleted: None,
-        })
-        .fetch_one(&mut *self.0)
-        .await?;
+        };
 
         Ok(channel)
     }
 
-    pub async fn by_id(&mut self, channel: &Id) -> Result<History, sqlx::Error> {
+    pub async fn by_id(&mut self, channel: &Id) -> Result<History, LoadError> {
         let channel = sqlx::query!(
             r#"
                 select
                     id as "id: Id",
-                    channel.name as "name: Name",
+                    name.display_name as "display_name?: String",
+                    name.canonical_name as "canonical_name?: String",
                     channel.created_at as "created_at: DateTime",
                     channel.created_sequence as "created_sequence: Sequence",
                     deleted.deleted_at as "deleted_at?: DateTime",
                     deleted.deleted_sequence as "deleted_sequence?: Sequence"
                 from channel
+                left join channel_name as name
+                    using (id)
                 left join channel_deleted as deleted
                     using (id)
                 where id = $1
             "#,
             channel,
         )
-        .map(|row| History {
-            channel: Channel {
-                id: row.id,
-                name: row.name.unwrap_or_default(),
-                deleted_at: row.deleted_at,
-            },
-            created: Instant::new(row.created_at, row.created_sequence),
-            deleted: Instant::optional(row.deleted_at, row.deleted_sequence),
+        .map(|row| {
+            Ok::<_, name::Error>(History {
+                channel: Channel {
+                    id: row.id,
+                    name: Name::optional(row.display_name, row.canonical_name)?.unwrap_or_default(),
+                    deleted_at: row.deleted_at,
+                },
+                created: Instant::new(row.created_at, row.created_sequence),
+                deleted: Instant::optional(row.deleted_at, row.deleted_sequence),
+            })
         })
         .fetch_one(&mut *self.0)
-        .await?;
+        .await??;
 
         Ok(channel)
     }
 
-    pub async fn all(&mut self, resume_at: ResumePoint) -> Result<Vec<History>, sqlx::Error> {
+    pub async fn all(&mut self, resume_at: ResumePoint) -> Result<Vec<History>, LoadError> {
         let channels = sqlx::query!(
             r#"
                 select
                     id as "id: Id",
-                    channel.name as "name: Name",
+                    name.display_name as "display_name: String",
+                    name.canonical_name as "canonical_name: String",
                     channel.created_at as "created_at: DateTime",
                     channel.created_sequence as "created_sequence: Sequence",
-                    deleted.deleted_at as "deleted_at: DateTime",
-                    deleted.deleted_sequence as "deleted_sequence: Sequence"
+                    deleted.deleted_at as "deleted_at?: DateTime",
+                    deleted.deleted_sequence as "deleted_sequence?: Sequence"
                 from channel
+                left join channel_name as name
+                    using (id)
                 left join channel_deleted as deleted
                     using (id)
                 where coalesce(channel.created_sequence <= $1, true)
-                order by channel.name
+                order by name.canonical_name
             "#,
             resume_at,
         )
-        .map(|row| History {
-            channel: Channel {
-                id: row.id,
-                name: row.name.unwrap_or_default(),
-                deleted_at: row.deleted_at,
-            },
-            created: Instant::new(row.created_at, row.created_sequence),
-            deleted: Instant::optional(row.deleted_at, row.deleted_sequence),
+        .map(|row| {
+            Ok::<_, name::Error>(History {
+                channel: Channel {
+                    id: row.id,
+                    name: Name::optional(row.display_name, row.canonical_name)?.unwrap_or_default(),
+                    deleted_at: row.deleted_at,
+                },
+                created: Instant::new(row.created_at, row.created_sequence),
+                deleted: Instant::optional(row.deleted_at, row.deleted_sequence),
+            })
         })
-        .fetch_all(&mut *self.0)
+        .fetch(&mut *self.0)
+        .map(|res| Ok::<_, LoadError>(res??))
+        .try_collect()
         .await?;
 
         Ok(channels)
     }
 
-    pub async fn replay(
-        &mut self,
-        resume_at: Option<Sequence>,
-    ) -> Result<Vec<History>, sqlx::Error> {
+    pub async fn replay(&mut self, resume_at: Option<Sequence>) -> Result<Vec<History>, LoadError> {
         let channels = sqlx::query!(
             r#"
                 select
                     id as "id: Id",
-                    channel.name as "name: Name",
+                    name.display_name as "display_name: String",
+                    name.canonical_name as "canonical_name: String",
                     channel.created_at as "created_at: DateTime",
                     channel.created_sequence as "created_sequence: Sequence",
-                    deleted.deleted_at as "deleted_at: DateTime",
-                    deleted.deleted_sequence as "deleted_sequence: Sequence"
+                    deleted.deleted_at as "deleted_at?: DateTime",
+                    deleted.deleted_sequence as "deleted_sequence?: Sequence"
                 from channel
+                left join channel_name as name
+                    using (id)
                 left join channel_deleted as deleted
                     using (id)
                 where coalesce(channel.created_sequence > $1, true)
             "#,
             resume_at,
         )
-        .map(|row| History {
-            channel: Channel {
-                id: row.id,
-                name: row.name.unwrap_or_default(),
-                deleted_at: row.deleted_at,
-            },
-            created: Instant::new(row.created_at, row.created_sequence),
-            deleted: Instant::optional(row.deleted_at, row.deleted_sequence),
+        .map(|row| {
+            Ok::<_, name::Error>(History {
+                channel: Channel {
+                    id: row.id,
+                    name: Name::optional(row.display_name, row.canonical_name)?.unwrap_or_default(),
+                    deleted_at: row.deleted_at,
+                },
+                created: Instant::new(row.created_at, row.created_sequence),
+                deleted: Instant::optional(row.deleted_at, row.deleted_sequence),
+            })
         })
-        .fetch_all(&mut *self.0)
+        .fetch(&mut *self.0)
+        .map(|res| Ok::<_, LoadError>(res??))
+        .try_collect()
         .await?;
 
         Ok(channels)
@@ -156,19 +187,18 @@ impl<'c> Channels<'c> {
         &mut self,
         channel: &History,
         deleted: &Instant,
-    ) -> Result<History, sqlx::Error> {
+    ) -> Result<History, LoadError> {
         let id = channel.id();
-        sqlx::query_scalar!(
+        sqlx::query!(
             r#"
                 insert into channel_deleted (id, deleted_at, deleted_sequence)
                 values ($1, $2, $3)
-                returning 1 as "deleted: bool"
             "#,
             id,
             deleted.at,
             deleted.sequence,
         )
-        .fetch_one(&mut *self.0)
+        .execute(&mut *self.0)
         .await?;
 
         // Small social responsibility hack here: when a channel is deleted, its name is
@@ -179,16 +209,14 @@ impl<'c> Channels<'c> {
         // This also avoids the need for a separate name reservation table to ensure
         // that live channels have unique names, since the `channel` table's name field
         // is unique over non-null values.
-        sqlx::query_scalar!(
+        sqlx::query!(
             r#"
-                update channel
-                set name = null
+                delete from channel_name
                 where id = $1
-                returning 1 as "updated: bool"
             "#,
             id,
         )
-        .fetch_one(&mut *self.0)
+        .execute(&mut *self.0)
         .await?;
 
         let channel = self.by_id(id).await?;
@@ -230,38 +258,66 @@ impl<'c> Channels<'c> {
         Ok(())
     }
 
-    pub async fn expired(&mut self, expired_at: &DateTime) -> Result<Vec<History>, sqlx::Error> {
+    pub async fn expired(&mut self, expired_at: &DateTime) -> Result<Vec<History>, LoadError> {
         let channels = sqlx::query!(
             r#"
                 select
                     channel.id as "id: Id",
-                    channel.name as "name: Name",
+                    name.display_name as "display_name: String",
+                    name.canonical_name as "canonical_name: String",
                     channel.created_at as "created_at: DateTime",
                     channel.created_sequence as "created_sequence: Sequence",
                     deleted.deleted_at as "deleted_at?: DateTime",
                     deleted.deleted_sequence as "deleted_sequence?: Sequence"
                 from channel
+                left join channel_name as name
+                    using (id)
                 left join channel_deleted as deleted
                     using (id)
                 left join message
+                    on channel.id = message.channel
                 where channel.created_at < $1
                     and message.id is null
                     and deleted.id is null
             "#,
             expired_at,
         )
-        .map(|row| History {
-            channel: Channel {
-                id: row.id,
-                name: row.name.unwrap_or_default(),
-                deleted_at: row.deleted_at,
-            },
-            created: Instant::new(row.created_at, row.created_sequence),
-            deleted: Instant::optional(row.deleted_at, row.deleted_sequence),
+        .map(|row| {
+            Ok::<_, name::Error>(History {
+                channel: Channel {
+                    id: row.id,
+                    name: Name::optional(row.display_name, row.canonical_name)?.unwrap_or_default(),
+                    deleted_at: row.deleted_at,
+                },
+                created: Instant::new(row.created_at, row.created_sequence),
+                deleted: Instant::optional(row.deleted_at, row.deleted_sequence),
+            })
         })
-        .fetch_all(&mut *self.0)
+        .fetch(&mut *self.0)
+        .map(|res| Ok::<_, LoadError>(res??))
+        .try_collect()
         .await?;
 
         Ok(channels)
     }
 }
+
+#[derive(Debug, thiserror::Error)]
+#[error(transparent)]
+pub enum LoadError {
+    Database(#[from] sqlx::Error),
+    Name(#[from] name::Error),
+}
+
+impl<T> NotFound for Result<T, LoadError> {
+    type Ok = T;
+    type Error = LoadError;
+
+    fn optional(self) -> Result<Option<T>, LoadError> {
+        match self {
+            Ok(value) => Ok(Some(value)),
+            Err(LoadError::Database(sqlx::Error::RowNotFound)) => Ok(None),
+            Err(other) => Err(other),
+        }
+    }
+}