Storylines: the same site told several ways, one per visitor, counted

Any text a person reads may be a list, one entry per storyline, every
list the same length. A visitor is given one storyline for the whole
site and reads it on every page and in every mail about their case.
Records and events carry the storyline; GET /report gives counts per
bucket, storyline and state, and nothing else.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GT37Z1Xtfd9pUuQtMTg6Yt

src/content/mod.rs

@@ -13,12 +13,16 @@ use serde::{Deserialize, Serialize};
 // Loading is server-only; the rest is shared with the browser build.
 #[cfg(feature = "ssr")]
 mod gitea;
+#[cfg(feature = "ssr")]
+mod variants;
 mod handlers;
 mod markdown;
 mod validate;
 
 #[cfg(feature = "ssr")]
 pub use gitea::*;
+#[cfg(feature = "ssr")]
+pub use variants::*;
 pub use handlers::*;
 pub use markdown::*;
 pub use validate::*;
@@ -1073,6 +1077,25 @@ pub fn resolve_question(
 #[cfg(feature = "ssr")]
 pub fn build_questions(
     files: &[(String, String)],
+) -> anyhow::Result<std::collections::HashMap<String, Question>> {
+    // The first storyline, once every list of texts has been held to
+    // the site's arity (see `variants.rs`); the machinery reads this
+    // one, and `build_storylines` builds the rest for the visitors.
+    variants::arity(files)?;
+    build_one_storyline(&variants::storyline(files, 0))
+}
+
+/// Every storyline of the content, each a full map of questions.
+#[cfg(feature = "ssr")]
+pub fn build_storylines(files: &[(String, String)]) -> anyhow::Result<variants::Storylines<std::collections::HashMap<String, Question>>> {
+    let arity = variants::arity(files)?;
+    let each = (0..arity).map(|n| build_one_storyline(&variants::storyline(files, n))).collect::<anyhow::Result<Vec<_>>>()?;
+    Ok(variants::Storylines { each })
+}
+
+#[cfg(feature = "ssr")]
+fn build_one_storyline(
+    files: &[(String, String)],
 ) -> anyhow::Result<std::collections::HashMap<String, Question>> {
     // Sections first: (directory prefix, config), shallowest first so a
     // later (deeper) section overrides an outer one field-by-field.