structural refactor and codebase improvements

crates/application/src/import/get_session_state.rs

@@ -0,0 +1,43 @@
+//! Backs `handlers/import.rs::api_get_session` — a plain state query, not a
+//! redirect-driving gate (the API has nothing to redirect to; a missing
+//! session is just a 404).
+
+use domain::{
+    errors::DomainError,
+    value_objects::{ImportSessionId, UserId},
+};
+use uuid::Uuid;
+
+use crate::import::deps::GetSessionStateDeps;
+
+pub struct SessionState {
+    pub columns: Vec<String>,
+    pub has_mappings: bool,
+    pub row_count: usize,
+}
+
+pub async fn execute(
+    deps: &GetSessionStateDeps,
+    session_id: ImportSessionId,
+    user_id: Uuid,
+) -> Result<SessionState, DomainError> {
+    let user_id = UserId::from_uuid(user_id);
+    let session = deps
+        .import_session
+        .get(&session_id, &user_id)
+        .await?
+        .ok_or_else(|| DomainError::NotFound("session not found".into()))?;
+
+    let parsed = session.parsed_file.unwrap_or_default();
+    let row_count = parsed.rows.len();
+
+    Ok(SessionState {
+        columns: parsed.columns,
+        has_mappings: session.field_mappings.is_some(),
+        row_count,
+    })
+}
+
+#[cfg(test)]
+#[path = "tests/get_session_state.rs"]
+mod tests;