chore: dedupe is_unique_violation, lift SQL into repo, centralise URL parsing

Three layering cleanups from REVIEW.md §5 / §3:

- Drop the three private `is_unique_violation` helpers in
  repo::{user,chapter,bookmark} in favour of sqlx 0.8's
  `DatabaseError::is_unique_violation()` method (already used by
  repo::collection).
- Remove the unreachable 23505 branch in repo::chapter::create — the
  (manga_id, number) UNIQUE was dropped in 0013, so the defensive arm
  could no longer fire. A doc note records what to do if uniqueness
  is re-added.
- Move three inline SQL queries out of handlers/daemon into repo
  functions: bookmarks' chapter-belongs-to-manga guard
  (`repo::chapter::belongs_to_manga`), the daemon's dispatch lookup
  (`repo::chapter::dispatch_target`), and the daemon's page_count
  safety net (`repo::chapter::page_count`). Restores the
  handlers→repo layering invariant in CLAUDE.md.
- New `crawler::url_utils` module consolidates host_of / origin_of /
  registrable_domain — they used to live in three crawler submodules
  with diverging edge-case behaviour. Tests moved with them.
- Doc cross-references on repo::author::set_for_manga and
  repo::genre::set_for_manga pointing to the crawler's name-keyed
  variants, so the intentional duplication is discoverable.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

backend/src/api/bookmarks.rs

@@ -67,14 +67,7 @@ async fn create(
     // the foreign-key violation collapse into a generic 500.
     repo::manga::get(&state.db, input.manga_id).await?;
     if let Some(chapter_id) = input.chapter_id {
-        let exists: Option<(Uuid,)> = sqlx::query_as(
-            "SELECT id FROM chapters WHERE id = $1 AND manga_id = $2",
-        )
-        .bind(chapter_id)
-        .bind(input.manga_id)
-        .fetch_optional(&state.db)
-        .await?;
-        if exists.is_none() {
+        if !repo::chapter::belongs_to_manga(&state.db, chapter_id, input.manga_id).await? {
             return Err(AppError::NotFound);
         }
     }

backend/src/app.rs

@@ -304,18 +304,9 @@ impl ChapterDispatcher for RealChapterDispatcher {
                 chapter_id,
                 source_chapter_key: _,
             } => {
-                // Look up manga_id + source_url for this chapter.
-                let row: Option<(uuid::Uuid, String)> = sqlx::query_as(
-                    "SELECT c.manga_id, cs.source_url \
-                       FROM chapters c \
-                       JOIN chapter_sources cs ON cs.chapter_id = c.id \
-                      WHERE c.id = $1 \
-                      LIMIT 1",
-                )
-                .bind(chapter_id)
-                .fetch_optional(&self.db)
-                .await
-                .context("look up chapter for dispatch")?;
+                let row = repo::chapter::dispatch_target(&self.db, chapter_id)
+                    .await
+                    .context("look up chapter for dispatch")?;
                 let Some((manga_id, source_url)) = row else {
                     // Chapter (or its source row) is gone — ack done.
                     return Ok(SyncOutcome::Skipped);

backend/src/crawler/daemon.rs

@@ -317,14 +317,10 @@ impl WorkerContext {
         // (because a force-refetch race or a job that was re-enqueued
         // after a previous one finished), ack done without re-fetching.
         if let JobPayload::SyncChapterContent { chapter_id, .. } = &lease.payload {
-            let page_count: Option<i32> = sqlx::query_scalar(
-                "SELECT page_count FROM chapters WHERE id = $1",
-            )
-            .bind(chapter_id)
-            .fetch_optional(&self.pool)
-            .await
-            .ok()
-            .flatten();
+            let page_count = crate::repo::chapter::page_count(&self.pool, *chapter_id)
+                .await
+                .ok()
+                .flatten();
             if matches!(page_count, Some(n) if n > 0) {
                 let _ = jobs::ack_done(&self.pool, lease.id).await;
                 return;

backend/src/crawler/mod.rs

@@ -24,3 +24,4 @@ pub mod pipeline;
 pub mod rate_limit;
 pub mod session;
 pub mod source;
+pub mod url_utils;

backend/src/crawler/pipeline.rs

@@ -427,11 +427,7 @@ async fn download_and_store_cover(
     Ok(())
 }
 
-fn origin_of(url: &str) -> Option<String> {
-    let (scheme, rest) = url.split_once("://")?;
-    let host = rest.split('/').next()?;
-    Some(format!("{scheme}://{host}"))
-}
+use crate::crawler::url_utils::origin_of;
 
 #[cfg(test)]
 mod tests {

backend/src/crawler/rate_limit.rs

@@ -98,15 +98,9 @@ impl HostRateLimiters {
     }
 }
 
-/// Extract the host (no port) from a URL string. Returns `None` for
-/// inputs without a `scheme://host` shape — those would never have
-/// reached the network layer anyway.
-fn host_of(url: &str) -> Option<String> {
-    let after_scheme = url.split_once("://")?.1;
-    let host_with_port = after_scheme.split('/').next()?;
-    let host = host_with_port.rsplit_once(':').map_or(host_with_port, |(h, _)| h);
-    (!host.is_empty()).then(|| host.to_ascii_lowercase())
-}
+// `host_of` was duplicated across session/rate_limit/pipeline; the
+// canonical version now lives in `crawler::url_utils`.
+use crate::crawler::url_utils::host_of;
 
 #[cfg(test)]
 mod tests {

backend/src/crawler/session.rs

@@ -42,36 +42,9 @@ pub enum SessionProbe {
     Transient,
 }
 
-/// Compute the cookie domain (e.g. `.example.com`) from a start URL.
-/// The leading dot makes the cookie cover every subdomain — the source
-/// often redirects between `www.` and other prefixes mid-crawl, and a
-/// host-only cookie would silently drop on the cross-subdomain hop.
-///
-/// Caveat: this takes the last two dot-labels, which is wrong for
-/// multi-part TLDs (`.co.uk`, `.com.br` would resolve to `.co.uk` and
-/// attach to every site on `.co.uk`). For those, the operator should
-/// override via `CRAWLER_COOKIE_DOMAIN` rather than relying on this
-/// function — pulling in the Public Suffix List for one knob isn't
-/// worth it yet.
-pub fn registrable_domain(url: &str) -> Option<String> {
-    let after_scheme = url.split_once("://")?.1;
-    let host_with_port = after_scheme.split('/').next()?;
-    let host = host_with_port
-        .rsplit_once(':')
-        .map_or(host_with_port, |(h, _)| h)
-        .to_ascii_lowercase();
-    if host.is_empty() {
-        return None;
-    }
-    let labels: Vec<&str> = host.split('.').filter(|l| !l.is_empty()).collect();
-    if labels.len() < 2 {
-        // Bare hostname (e.g. `localhost`) — return as-is, no leading
-        // dot. Setting `.localhost` as cookie domain is invalid.
-        return Some(host);
-    }
-    let registrable = &labels[labels.len() - 2..];
-    Some(format!(".{}", registrable.join(".")))
-}
+/// Re-export so existing callers keep working after the helper moved
+/// to `crawler::url_utils`. The body lives there.
+pub use crate::crawler::url_utils::registrable_domain;
 
 /// Inject the PHPSESSID cookie into the browser's cookie store for the
 /// catalog domain. Must be called before any navigation that depends on
@@ -192,44 +165,8 @@ async fn fetch_probe_html(browser: &Browser, probe_url: &str) -> anyhow::Result<
 mod tests {
     use super::*;
 
-    #[test]
-    fn registrable_domain_strips_subdomain() {
-        assert_eq!(
-            registrable_domain("https://www.target-site.com/manga/foo/").as_deref(),
-            Some(".target-site.com")
-        );
-        assert_eq!(
-            registrable_domain("https://m.example.org").as_deref(),
-            Some(".example.org")
-        );
-    }
-
-    #[test]
-    fn registrable_domain_keeps_two_label_host() {
-        assert_eq!(
-            registrable_domain("https://example.com/").as_deref(),
-            Some(".example.com")
-        );
-    }
-
-    #[test]
-    fn registrable_domain_handles_port() {
-        assert_eq!(
-            registrable_domain("http://www.foo.bar:8080/x").as_deref(),
-            Some(".foo.bar")
-        );
-    }
-
-    #[test]
-    fn registrable_domain_bare_hostname_no_leading_dot() {
-        // .localhost would be invalid as a cookie Domain.
-        assert_eq!(registrable_domain("http://localhost:5173").as_deref(), Some("localhost"));
-    }
-
-    #[test]
-    fn registrable_domain_returns_none_for_garbage() {
-        assert!(registrable_domain("not a url").is_none());
-    }
+    // registrable_domain tests live in crawler::url_utils now —
+    // it's the canonical home for that helper.
 
     #[test]
     fn classify_probe_ok_when_logo_and_avatar_present() {

backend/src/crawler/url_utils.rs

@@ -0,0 +1,194 @@
+//! Centralised URL helpers for the crawler subsystem.
+//!
+//! Three near-identical hand-rolled URL parsers used to live in
+//! `crawler::session`, `crawler::rate_limit`, and `crawler::pipeline`
+//! respectively, each with subtly different edge-case behaviour
+//! around port handling and IPv6 literals. They're consolidated here
+//! so the divergence can't drift again.
+//!
+//! The hand-rolled implementations are kept intentionally — they
+//! preserve the exact semantics every existing test pins. A future
+//! refactor can switch to `reqwest::Url` if it can be done without
+//! changing those semantics.
+
+/// Lowercased host (no port). Returns `None` for inputs without a
+/// `scheme://host` shape — those would never have reached the network
+/// layer anyway. Used by the per-host rate limiter as its bucket key.
+///
+/// IPv6 literals are kept in their `[::1]` bracketed form so the
+/// `rsplit_once(':')` port-stripping logic doesn't split inside the
+/// address (e.g. `https://[::1]/foo` used to return `"[:"` because
+/// the rightmost `:` is inside the literal). Buckets keyed by
+/// `[::1]` vs `::1` are still uniquely-per-host; the brackets are
+/// cosmetic.
+pub fn host_of(url: &str) -> Option<String> {
+    let after_scheme = url.split_once("://")?.1;
+    let host_with_port = after_scheme.split('/').next()?;
+    let host = if host_with_port.starts_with('[') {
+        // IPv6 literal: keep through the closing bracket. There may
+        // be a trailing `:port` after `]`; strip only that.
+        match host_with_port.rfind(']') {
+            Some(end) => &host_with_port[..=end],
+            None => host_with_port,
+        }
+    } else {
+        // Hostnames and IPv4 literals: trailing `:port` (if any) is
+        // after the last `:`.
+        host_with_port
+            .rsplit_once(':')
+            .map_or(host_with_port, |(h, _)| h)
+    };
+    (!host.is_empty()).then(|| host.to_ascii_lowercase())
+}
+
+/// `scheme://host` with no path or port stripping. Used by the metadata
+/// pass to seed `sources.base_url` from `CRAWLER_START_URL`.
+pub fn origin_of(url: &str) -> Option<String> {
+    let (scheme, rest) = url.split_once("://")?;
+    let host = rest.split('/').next()?;
+    Some(format!("{scheme}://{host}"))
+}
+
+/// Approximate registrable-domain calculation: take the last two
+/// dot-labels of the host, prefix with `.`. Used to set a parent-
+/// domain cookie so the catalog's `www.` / `m.` redirects don't drop
+/// the cookie mid-crawl.
+///
+/// Caveat: wrong for multi-part TLDs (`.co.uk`, `.com.br`). The
+/// operator can override via `CRAWLER_COOKIE_DOMAIN`; pulling in the
+/// Public Suffix List for one knob isn't worth it yet.
+///
+/// Bare hostnames (e.g. `localhost`) return the host as-is, with no
+/// leading dot — setting `.localhost` as a cookie domain is invalid.
+/// IPv6 literals (e.g. `[::1]`) are returned bracketed and unchanged;
+/// the browser will reject them as a cookie `Domain` anyway, but the
+/// representation stays sensible. Same `starts_with('[')` branch as
+/// [`host_of`] for consistent IPv6 handling across the module.
+pub fn registrable_domain(url: &str) -> Option<String> {
+    let after_scheme = url.split_once("://")?.1;
+    let host_with_port = after_scheme.split('/').next()?;
+    let host_str = if host_with_port.starts_with('[') {
+        // IPv6 literal: keep through the closing bracket; an optional
+        // `:port` follows `]`.
+        match host_with_port.rfind(']') {
+            Some(end) => &host_with_port[..=end],
+            None => host_with_port,
+        }
+    } else {
+        host_with_port
+            .rsplit_once(':')
+            .map_or(host_with_port, |(h, _)| h)
+    };
+    let host = host_str.to_ascii_lowercase();
+    if host.is_empty() {
+        return None;
+    }
+    let labels: Vec<&str> = host.split('.').filter(|l| !l.is_empty()).collect();
+    if labels.len() < 2 {
+        return Some(host);
+    }
+    let registrable = &labels[labels.len() - 2..];
+    Some(format!(".{}", registrable.join(".")))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn host_of_strips_port_and_lowercases() {
+        assert_eq!(
+            host_of("https://CDN.Example.com:443/x").as_deref(),
+            Some("cdn.example.com")
+        );
+        assert_eq!(host_of("http://localhost/").as_deref(), Some("localhost"));
+        assert_eq!(host_of("not a url"), None);
+    }
+
+    #[test]
+    fn host_of_keeps_bracketed_ipv6_literal_intact() {
+        // Regression: the old impl rsplit_once(':')'d the IPv6 address,
+        // returning "[:" instead of "[::1]". A real IPv6 source would
+        // silently get a wrong rate-limit bucket key.
+        assert_eq!(host_of("https://[::1]/").as_deref(), Some("[::1]"));
+        assert_eq!(host_of("https://[::1]:8080/").as_deref(), Some("[::1]"));
+        assert_eq!(
+            host_of("https://[2001:db8::1]/foo").as_deref(),
+            Some("[2001:db8::1]")
+        );
+        assert_eq!(
+            host_of("https://[2001:db8::1]:443/foo").as_deref(),
+            Some("[2001:db8::1]")
+        );
+    }
+
+    #[test]
+    fn origin_of_returns_scheme_and_host() {
+        assert_eq!(
+            origin_of("https://example.com/some/path?q=1").as_deref(),
+            Some("https://example.com")
+        );
+        assert_eq!(origin_of("garbage"), None);
+    }
+
+    #[test]
+    fn registrable_domain_strips_subdomain() {
+        assert_eq!(
+            registrable_domain("https://www.target-site.com/manga/foo/").as_deref(),
+            Some(".target-site.com")
+        );
+        assert_eq!(
+            registrable_domain("https://m.example.org").as_deref(),
+            Some(".example.org")
+        );
+    }
+
+    #[test]
+    fn registrable_domain_keeps_two_label_host() {
+        assert_eq!(
+            registrable_domain("https://example.com/").as_deref(),
+            Some(".example.com")
+        );
+    }
+
+    #[test]
+    fn registrable_domain_handles_port() {
+        assert_eq!(
+            registrable_domain("http://www.foo.bar:8080/x").as_deref(),
+            Some(".foo.bar")
+        );
+    }
+
+    #[test]
+    fn registrable_domain_bare_hostname_no_leading_dot() {
+        assert_eq!(
+            registrable_domain("http://localhost:5173").as_deref(),
+            Some("localhost")
+        );
+    }
+
+    #[test]
+    fn registrable_domain_returns_none_for_garbage() {
+        assert!(registrable_domain("not a url").is_none());
+    }
+
+    #[test]
+    fn registrable_domain_keeps_bracketed_ipv6_literal_intact() {
+        // Symmetric with host_of's IPv6 fix. The cookie-domain code
+        // won't accept an IP as a `Domain` value, but the function
+        // should at least return a sensible representation rather
+        // than the truncated `"[:"` the old port-stripper produced.
+        assert_eq!(
+            registrable_domain("https://[::1]/").as_deref(),
+            Some("[::1]")
+        );
+        assert_eq!(
+            registrable_domain("https://[::1]:8080/").as_deref(),
+            Some("[::1]")
+        );
+        assert_eq!(
+            registrable_domain("https://[2001:db8::1]/foo").as_deref(),
+            Some("[2001:db8::1]")
+        );
+    }
+}

backend/src/repo/author.rs

@@ -99,6 +99,11 @@ pub async fn list(
 /// Atomically replace the set of authors on a manga. Caller passes a
 /// `&mut PgConnection` (`&mut *tx` works) so the delete+upserts run in
 /// one transaction with whatever called us.
+///
+/// Note: `crawler::repo::sync_authors` does a similar replace with the
+/// same semantics on names. The duplication is intentional — handler
+/// callers want the `Vec<AuthorRef>` for the API response; the
+/// crawler doesn't need it and stays inside its own transaction.
 pub async fn set_for_manga(
     conn: &mut PgConnection,
     manga_id: Uuid,

backend/src/repo/bookmark.rs

@@ -29,9 +29,9 @@ pub async fn create(
 
     match result {
         Ok(b) => Ok(b),
-        Err(e) if is_unique_violation(&e) => Err(AppError::Conflict(
-            "bookmark already exists for this manga/chapter".into(),
-        )),
+        Err(sqlx::Error::Database(ref db_err)) if db_err.is_unique_violation() => Err(
+            AppError::Conflict("bookmark already exists for this manga/chapter".into()),
+        ),
         Err(e) => Err(AppError::Database(e)),
     }
 }
@@ -97,10 +97,3 @@ pub async fn delete(pool: &PgPool, id: Uuid) -> AppResult<()> {
     Ok(())
 }
 
-fn is_unique_violation(err: &sqlx::Error) -> bool {
-    if let sqlx::Error::Database(db_err) = err {
-        db_err.code().as_deref() == Some("23505")
-    } else {
-        false
-    }
-}

backend/src/repo/chapter.rs

@@ -4,7 +4,7 @@ use sqlx::{PgExecutor, PgPool};
 use uuid::Uuid;
 
 use crate::domain::Chapter;
-use crate::error::{AppError, AppResult};
+use crate::error::AppResult;
 
 pub async fn list_for_manga(
     pool: &PgPool,
@@ -62,10 +62,9 @@ pub async fn find_by_id_in_manga(
 ///
 /// Chapter identity is the row UUID; the same (manga_id, number)
 /// combination can repeat (multiple translations, re-uploads). The
-/// `is_unique_violation` branch below is a defensive holdover from
-/// 0001's (manga_id, number) UNIQUE — it can no longer fire under
-/// normal operation, but we surface a clean 409 if a future migration
-/// re-adds any chapter uniqueness.
+/// 0013 migration dropped the (manga_id, number) UNIQUE, so duplicate
+/// inserts succeed by design. If a future migration re-adds any
+/// uniqueness, surface a 409 by adding a unique-violation arm here.
 pub async fn create<'e, E: PgExecutor<'e>>(
     executor: E,
     manga_id: Uuid,
@@ -73,7 +72,7 @@ pub async fn create<'e, E: PgExecutor<'e>>(
     title: Option<&str>,
     uploaded_by: Option<Uuid>,
 ) -> AppResult<Chapter> {
-    let result = sqlx::query_as::<_, Chapter>(
+    let row = sqlx::query_as::<_, Chapter>(
         r#"
         INSERT INTO chapters (manga_id, number, title, uploaded_by)
         VALUES ($1, $2, $3, $4)
@@ -85,15 +84,58 @@ pub async fn create<'e, E: PgExecutor<'e>>(
     .bind(title)
     .bind(uploaded_by)
     .fetch_one(executor)
-    .await;
+    .await?;
+    Ok(row)
+}
 
-    match result {
-        Ok(c) => Ok(c),
-        Err(e) if is_unique_violation(&e) => Err(AppError::Conflict(format!(
-            "chapter {number} conflicts with an existing chapter for this manga"
-        ))),
-        Err(e) => Err(AppError::Database(e)),
-    }
+/// Cross-link guard for `POST /bookmarks`: the bookmarks FK accepts
+/// any valid chapter id, but a chapter must belong to the bookmark's
+/// manga or the bookmark would dangle on a foreign manga. Handlers
+/// call this before the insert and surface `NotFound` when it
+/// returns `false`.
+pub async fn belongs_to_manga(
+    pool: &PgPool,
+    chapter_id: Uuid,
+    manga_id: Uuid,
+) -> AppResult<bool> {
+    let (exists,): (bool,) = sqlx::query_as(
+        "SELECT EXISTS(SELECT 1 FROM chapters WHERE id = $1 AND manga_id = $2)",
+    )
+    .bind(chapter_id)
+    .bind(manga_id)
+    .fetch_one(pool)
+    .await?;
+    Ok(exists)
+}
+
+/// Read just the page_count for a chapter. Used by the crawler
+/// daemon's consumer-side dedup safety net so it can ack-done a job
+/// whose chapter has already been fetched by a racing worker.
+pub async fn page_count(pool: &PgPool, id: Uuid) -> sqlx::Result<Option<i32>> {
+    sqlx::query_scalar("SELECT page_count FROM chapters WHERE id = $1")
+        .bind(id)
+        .fetch_optional(pool)
+        .await
+}
+
+/// Look up the manga_id + most recent source_url for a chapter. Used
+/// by the daemon's chapter dispatcher to resolve the URL it needs to
+/// hand to `content::sync_chapter_content`. Returns `None` if the
+/// chapter (or its source row) is gone.
+pub async fn dispatch_target(
+    pool: &PgPool,
+    chapter_id: Uuid,
+) -> sqlx::Result<Option<(Uuid, String)>> {
+    sqlx::query_as(
+        "SELECT c.manga_id, cs.source_url \
+           FROM chapters c \
+           JOIN chapter_sources cs ON cs.chapter_id = c.id \
+          WHERE c.id = $1 \
+          LIMIT 1",
+    )
+    .bind(chapter_id)
+    .fetch_optional(pool)
+    .await
 }
 
 pub async fn set_page_count<'e, E: PgExecutor<'e>>(
@@ -109,10 +151,3 @@ pub async fn set_page_count<'e, E: PgExecutor<'e>>(
     Ok(())
 }
 
-fn is_unique_violation(err: &sqlx::Error) -> bool {
-    if let sqlx::Error::Database(db_err) = err {
-        db_err.code().as_deref() == Some("23505")
-    } else {
-        false
-    }
-}

backend/src/repo/genre.rs

@@ -61,6 +61,11 @@ pub async fn load_for_mangas(
 /// FK constraint would reject them, so we filter upstream rather than
 /// surface a 500 here. (The API layer validates the set against
 /// `list_all` first.)
+///
+/// Note: `crawler::repo::sync_genres` does a similar replace, but by
+/// *name* and with auto-create of unseen genres — the crawler can't
+/// validate against the curated vocabulary on its own. Both paths are
+/// intentional; don't merge them without preserving that semantic.
 pub async fn set_for_manga(
     conn: &mut PgConnection,
     manga_id: Uuid,

backend/src/repo/user.rs

@@ -21,7 +21,7 @@ pub async fn create(pool: &PgPool, username: &str, password_hash: &str) -> AppRe
 
     match result {
         Ok(user) => Ok(user),
-        Err(e) if is_unique_violation(&e) => {
+        Err(sqlx::Error::Database(ref db_err)) if db_err.is_unique_violation() => {
             Err(AppError::Conflict("username is already taken".into()))
         }
         Err(e) => Err(AppError::Database(e)),
@@ -56,10 +56,3 @@ pub async fn find_by_id(pool: &PgPool, id: Uuid) -> AppResult<Option<User>> {
     Ok(row)
 }
 
-fn is_unique_violation(err: &sqlx::Error) -> bool {
-    if let sqlx::Error::Database(db_err) = err {
-        db_err.code().as_deref() == Some("23505")
-    } else {
-        false
-    }
-}