feat(gui): pure-logic helpers for Policy tab (mode mapping, violation grouping)

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

gui/src/main.rs

@@ -7,6 +7,7 @@ mod enroll_dialog;
 mod error;
 mod firstrun;
 mod keys_page;
+mod policy_form;
 
 const APP_ID: &str = "io.dangerousthings.AuthForge";
 

gui/src/policy_form.rs

@@ -0,0 +1,92 @@
+//! Pure helpers backing the Policy tab. Mode <-> combo index, violation
+//! grouping. Widget code calls these; nothing here touches GTK.
+//!
+//! `dead_code` allowances mirror `bus.rs` — these helpers are wired through
+//! `policy_page.rs` in Task 4; without the allow, this commit's `-D warnings`
+//! gate would reject the staged-but-unused symbols.
+
+#![allow(dead_code)]
+
+use authforge_common::types::{Mode, Violation};
+use std::collections::BTreeMap;
+
+pub(crate) const MODE_LABELS: &[(&str, Mode)] = &[
+    ("Disabled", Mode::Disabled),
+    ("Optional", Mode::Optional),
+    ("Required", Mode::Required),
+];
+
+pub(crate) fn mode_to_combo_index(m: Mode) -> u32 {
+    match m {
+        Mode::Disabled => 0,
+        Mode::Optional => 1,
+        Mode::Required => 2,
+    }
+}
+
+pub(crate) fn combo_index_to_mode(idx: u32) -> Mode {
+    match idx {
+        0 => Mode::Disabled,
+        1 => Mode::Optional,
+        _ => Mode::Required,
+    }
+}
+
+/// Group violations by stack, joining reasons with "; ". Used to render the
+/// inline AdwBanner content when `SetPolicy(force=false)` returns violations.
+pub(crate) fn group_violations_by_stack(vs: &[Violation]) -> BTreeMap<String, String> {
+    let mut by_stack: BTreeMap<String, Vec<String>> = BTreeMap::new();
+    for v in vs {
+        by_stack
+            .entry(v.stack.clone())
+            .or_default()
+            .push(format!("{}: {}", v.user, v.reason));
+    }
+    by_stack
+        .into_iter()
+        .map(|(k, vs)| (k, vs.join("; ")))
+        .collect()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn mode_combo_roundtrips() {
+        for m in [Mode::Disabled, Mode::Optional, Mode::Required] {
+            assert_eq!(combo_index_to_mode(mode_to_combo_index(m)), m);
+        }
+    }
+
+    #[test]
+    fn out_of_range_index_clamps_to_required() {
+        assert_eq!(combo_index_to_mode(99), Mode::Required);
+    }
+
+    #[test]
+    fn violations_group_by_stack() {
+        let vs = vec![
+            Violation {
+                user: "alice".into(),
+                stack: "sudo".into(),
+                reason: "no fido2".into(),
+            },
+            Violation {
+                user: "bob".into(),
+                stack: "sudo".into(),
+                reason: "no fido2".into(),
+            },
+            Violation {
+                user: "alice".into(),
+                stack: "sshd".into(),
+                reason: "no fido2".into(),
+            },
+        ];
+        let g = group_violations_by_stack(&vs);
+        assert_eq!(g.len(), 2);
+        assert!(g.get("sudo").unwrap().contains("alice"));
+        assert!(g.get("sudo").unwrap().contains("bob"));
+        assert_eq!(g.get("sshd").unwrap(), "alice: no fido2");
+    }
+}