feat(tui): Phase 2 detail screens — Issue Detail, MR Detail, discussion tree, cross-refs

Implements the remaining Phase 2 Core Screens:

- Discussion tree widget (view/common/discussion_tree.rs): DiscussionNode/NoteNode types,
  expand/collapse state, visual row flattening, format_relative_time with Clock trait
- Cross-reference widget (view/common/cross_ref.rs): CrossRefKind enum, navigable refs,
  badge rendering ([MR]/[REL]/[REF])
- Issue Detail (state + action + view): progressive hydration (metadata Phase 1,
  discussions Phase 2), section cycling, description scroll, sanitized GitLab content
- MR Detail (state + action + view): tab bar (Overview/Files/Discussions), file changes
  with change type indicators, branch info, draft/merge status, diff note support
- Message + update wiring: IssueDetailLoaded, MrDetailLoaded, DiscussionsLoaded handlers
  with TaskSupervisor stale-result guards

Closes bd-1d6z, bd-8ab7, bd-3t1b, bd-1cl9 (Phase 2 epic).
389 tests passing, clippy clean, fmt clean.

crates/lore-tui/src/state/issue_detail.rs

@@ -1,14 +1,284 @@
-#![allow(dead_code)]
+#![allow(dead_code)] // Phase 2: consumed by Issue Detail screen
 
 //! Issue detail screen state.
+//!
+//! Holds metadata, discussions, cross-references, and UI state for
+//! viewing a single issue. Supports progressive hydration: metadata
+//! loads first, discussions load async in a second phase.
 
-use crate::message::{Discussion, EntityKey, IssueDetail};
+use crate::message::EntityKey;
+use crate::view::common::cross_ref::{CrossRef, CrossRefState};
+use crate::view::common::discussion_tree::{DiscussionNode, DiscussionTreeState};
+
+// ---------------------------------------------------------------------------
+// IssueMetadata
+// ---------------------------------------------------------------------------
+
+/// Full metadata for a single issue, fetched from the local DB.
+#[derive(Debug, Clone)]
+pub struct IssueMetadata {
+    /// Issue IID (project-scoped).
+    pub iid: i64,
+    /// Project path (e.g., "group/project").
+    pub project_path: String,
+    /// Issue title.
+    pub title: String,
+    /// Issue description (markdown).
+    pub description: String,
+    /// Current state: "opened" or "closed".
+    pub state: String,
+    /// Author username.
+    pub author: String,
+    /// Assigned usernames.
+    pub assignees: Vec<String>,
+    /// Label names.
+    pub labels: Vec<String>,
+    /// Milestone title (if set).
+    pub milestone: Option<String>,
+    /// Due date (if set, "YYYY-MM-DD").
+    pub due_date: Option<String>,
+    /// Created timestamp (ms epoch).
+    pub created_at: i64,
+    /// Updated timestamp (ms epoch).
+    pub updated_at: i64,
+    /// GitLab web URL for "open in browser".
+    pub web_url: String,
+    /// Discussion count (for display before discussions load).
+    pub discussion_count: usize,
+}
+
+// ---------------------------------------------------------------------------
+// IssueDetailData
+// ---------------------------------------------------------------------------
+
+/// Bundle returned by the metadata fetch action.
+///
+/// Metadata + cross-refs load in Phase 1 (fast). Discussions load
+/// separately in Phase 2.
+#[derive(Debug, Clone)]
+pub struct IssueDetailData {
+    pub metadata: IssueMetadata,
+    pub cross_refs: Vec<CrossRef>,
+}
+
+// ---------------------------------------------------------------------------
+// DetailSection
+// ---------------------------------------------------------------------------
+
+/// Which section of the detail view has keyboard focus.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
+pub enum DetailSection {
+    /// Description area (scrollable text).
+    #[default]
+    Description,
+    /// Discussion tree.
+    Discussions,
+    /// Cross-references list.
+    CrossRefs,
+}
+
+impl DetailSection {
+    /// Cycle to the next section.
+    #[must_use]
+    pub fn next(self) -> Self {
+        match self {
+            Self::Description => Self::Discussions,
+            Self::Discussions => Self::CrossRefs,
+            Self::CrossRefs => Self::Description,
+        }
+    }
+
+    /// Cycle to the previous section.
+    #[must_use]
+    pub fn prev(self) -> Self {
+        match self {
+            Self::Description => Self::CrossRefs,
+            Self::Discussions => Self::Description,
+            Self::CrossRefs => Self::Discussions,
+        }
+    }
+}
+
+// ---------------------------------------------------------------------------
+// IssueDetailState
+// ---------------------------------------------------------------------------
 
 /// State for the issue detail screen.
 #[derive(Debug, Default)]
 pub struct IssueDetailState {
-    pub key: Option<EntityKey>,
-    pub detail: Option<IssueDetail>,
-    pub discussions: Vec<Discussion>,
-    pub scroll_offset: u16,
+    /// Entity key for the currently displayed issue.
+    pub current_key: Option<EntityKey>,
+    /// Issue metadata (Phase 1 load).
+    pub metadata: Option<IssueMetadata>,
+    /// Discussion nodes (Phase 2 async load).
+    pub discussions: Vec<DiscussionNode>,
+    /// Whether discussions have finished loading.
+    pub discussions_loaded: bool,
+    /// Cross-references (loaded with metadata in Phase 1).
+    pub cross_refs: Vec<CrossRef>,
+    /// Discussion tree UI state (expand/collapse, selection).
+    pub tree_state: DiscussionTreeState,
+    /// Cross-reference list UI state.
+    pub cross_ref_state: CrossRefState,
+    /// Description scroll offset.
+    pub description_scroll: usize,
+    /// Active section for keyboard focus.
+    pub active_section: DetailSection,
+}
+
+impl IssueDetailState {
+    /// Reset state for a new issue.
+    pub fn load_new(&mut self, key: EntityKey) {
+        self.current_key = Some(key);
+        self.metadata = None;
+        self.discussions.clear();
+        self.discussions_loaded = false;
+        self.cross_refs.clear();
+        self.tree_state = DiscussionTreeState::default();
+        self.cross_ref_state = CrossRefState::default();
+        self.description_scroll = 0;
+        self.active_section = DetailSection::Description;
+    }
+
+    /// Apply Phase 1 data (metadata + cross-refs).
+    pub fn apply_metadata(&mut self, data: IssueDetailData) {
+        self.metadata = Some(data.metadata);
+        self.cross_refs = data.cross_refs;
+    }
+
+    /// Apply Phase 2 data (discussions).
+    pub fn apply_discussions(&mut self, discussions: Vec<DiscussionNode>) {
+        self.discussions = discussions;
+        self.discussions_loaded = true;
+    }
+
+    /// Whether we have metadata loaded for the current key.
+    #[must_use]
+    pub fn has_metadata(&self) -> bool {
+        self.metadata.is_some()
+    }
+
+    /// Cycle to the next section.
+    pub fn next_section(&mut self) {
+        self.active_section = self.active_section.next();
+    }
+
+    /// Cycle to the previous section.
+    pub fn prev_section(&mut self) {
+        self.active_section = self.active_section.prev();
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Tests
+// ---------------------------------------------------------------------------
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::view::common::cross_ref::CrossRefKind;
+
+    #[test]
+    fn test_issue_detail_state_default() {
+        let state = IssueDetailState::default();
+        assert!(state.current_key.is_none());
+        assert!(state.metadata.is_none());
+        assert!(state.discussions.is_empty());
+        assert!(!state.discussions_loaded);
+        assert!(state.cross_refs.is_empty());
+        assert_eq!(state.active_section, DetailSection::Description);
+    }
+
+    #[test]
+    fn test_load_new_resets_state() {
+        let mut state = IssueDetailState {
+            discussions_loaded: true,
+            description_scroll: 10,
+            active_section: DetailSection::CrossRefs,
+            ..IssueDetailState::default()
+        };
+
+        state.load_new(EntityKey::issue(1, 42));
+        assert_eq!(state.current_key, Some(EntityKey::issue(1, 42)));
+        assert!(state.metadata.is_none());
+        assert!(!state.discussions_loaded);
+        assert_eq!(state.description_scroll, 0);
+        assert_eq!(state.active_section, DetailSection::Description);
+    }
+
+    #[test]
+    fn test_apply_metadata() {
+        let mut state = IssueDetailState::default();
+        state.load_new(EntityKey::issue(1, 42));
+
+        let data = IssueDetailData {
+            metadata: IssueMetadata {
+                iid: 42,
+                project_path: "group/proj".into(),
+                title: "Fix auth".into(),
+                description: "Description here".into(),
+                state: "opened".into(),
+                author: "alice".into(),
+                assignees: vec!["bob".into()],
+                labels: vec!["backend".into()],
+                milestone: Some("v1.0".into()),
+                due_date: None,
+                created_at: 1_700_000_000_000,
+                updated_at: 1_700_000_060_000,
+                web_url: "https://gitlab.com/group/proj/-/issues/42".into(),
+                discussion_count: 3,
+            },
+            cross_refs: vec![CrossRef {
+                kind: CrossRefKind::ClosingMr,
+                entity_key: EntityKey::mr(1, 10),
+                label: "Fix auth MR".into(),
+                navigable: true,
+            }],
+        };
+
+        state.apply_metadata(data);
+        assert!(state.has_metadata());
+        assert_eq!(state.metadata.as_ref().unwrap().iid, 42);
+        assert_eq!(state.cross_refs.len(), 1);
+    }
+
+    #[test]
+    fn test_apply_discussions() {
+        let mut state = IssueDetailState::default();
+        assert!(!state.discussions_loaded);
+
+        let discussions = vec![DiscussionNode {
+            discussion_id: "d1".into(),
+            notes: vec![],
+            resolvable: false,
+            resolved: false,
+        }];
+
+        state.apply_discussions(discussions);
+        assert!(state.discussions_loaded);
+        assert_eq!(state.discussions.len(), 1);
+    }
+
+    #[test]
+    fn test_detail_section_cycling() {
+        let section = DetailSection::Description;
+        assert_eq!(section.next(), DetailSection::Discussions);
+        assert_eq!(section.next().next(), DetailSection::CrossRefs);
+        assert_eq!(section.next().next().next(), DetailSection::Description);
+
+        assert_eq!(section.prev(), DetailSection::CrossRefs);
+        assert_eq!(section.prev().prev(), DetailSection::Discussions);
+    }
+
+    #[test]
+    fn test_section_next_prev_round_trip() {
+        let mut state = IssueDetailState::default();
+        assert_eq!(state.active_section, DetailSection::Description);
+
+        state.next_section();
+        assert_eq!(state.active_section, DetailSection::Discussions);
+
+        state.prev_section();
+        assert_eq!(state.active_section, DetailSection::Description);
+    }
 }

crates/lore-tui/src/state/mr_detail.rs

@@ -1,14 +1,387 @@
-#![allow(dead_code)]
+#![allow(dead_code)] // Phase 2: consumed by MR Detail screen
 
 //! Merge request detail screen state.
+//!
+//! Holds MR metadata, file changes, discussions, cross-references,
+//! and UI state. Supports progressive hydration identical to
+//! Issue Detail: metadata loads first, discussions load async.
 
-use crate::message::{Discussion, EntityKey, MrDetail};
+use crate::message::EntityKey;
+use crate::view::common::cross_ref::{CrossRef, CrossRefState};
+use crate::view::common::discussion_tree::{DiscussionNode, DiscussionTreeState};
+
+// ---------------------------------------------------------------------------
+// MrMetadata
+// ---------------------------------------------------------------------------
+
+/// Full metadata for a single merge request, fetched from the local DB.
+#[derive(Debug, Clone)]
+pub struct MrMetadata {
+    /// MR IID (project-scoped).
+    pub iid: i64,
+    /// Project path (e.g., "group/project").
+    pub project_path: String,
+    /// MR title.
+    pub title: String,
+    /// MR description (markdown).
+    pub description: String,
+    /// Current state: "opened", "merged", "closed", "locked".
+    pub state: String,
+    /// Whether this is a draft/WIP MR.
+    pub draft: bool,
+    /// Author username.
+    pub author: String,
+    /// Assigned usernames.
+    pub assignees: Vec<String>,
+    /// Reviewer usernames.
+    pub reviewers: Vec<String>,
+    /// Label names.
+    pub labels: Vec<String>,
+    /// Source branch name.
+    pub source_branch: String,
+    /// Target branch name.
+    pub target_branch: String,
+    /// Detailed merge status (e.g., "mergeable", "checking").
+    pub merge_status: String,
+    /// Created timestamp (ms epoch).
+    pub created_at: i64,
+    /// Updated timestamp (ms epoch).
+    pub updated_at: i64,
+    /// Merged timestamp (ms epoch), if merged.
+    pub merged_at: Option<i64>,
+    /// GitLab web URL.
+    pub web_url: String,
+    /// Discussion count (for display before discussions load).
+    pub discussion_count: usize,
+    /// File change count.
+    pub file_change_count: usize,
+}
+
+// ---------------------------------------------------------------------------
+// FileChange
+// ---------------------------------------------------------------------------
+
+/// A file changed in the merge request.
+#[derive(Debug, Clone)]
+pub struct FileChange {
+    /// Previous file path (if renamed).
+    pub old_path: Option<String>,
+    /// New/current file path.
+    pub new_path: String,
+    /// Type of change.
+    pub change_type: FileChangeType,
+}
+
+/// The type of file change in an MR.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum FileChangeType {
+    Added,
+    Modified,
+    Deleted,
+    Renamed,
+}
+
+impl FileChangeType {
+    /// Short icon for display.
+    #[must_use]
+    pub const fn icon(&self) -> &str {
+        match self {
+            Self::Added => "+",
+            Self::Modified => "~",
+            Self::Deleted => "-",
+            Self::Renamed => "R",
+        }
+    }
+
+    /// Parse from DB string.
+    #[must_use]
+    pub fn parse_db(s: &str) -> Self {
+        match s {
+            "added" => Self::Added,
+            "deleted" => Self::Deleted,
+            "renamed" => Self::Renamed,
+            _ => Self::Modified,
+        }
+    }
+}
+
+// ---------------------------------------------------------------------------
+// MrDetailData
+// ---------------------------------------------------------------------------
+
+/// Bundle returned by the metadata fetch action.
+///
+/// Metadata + cross-refs + file changes load in Phase 1 (fast).
+/// Discussions load separately in Phase 2.
+#[derive(Debug, Clone)]
+pub struct MrDetailData {
+    pub metadata: MrMetadata,
+    pub cross_refs: Vec<CrossRef>,
+    pub file_changes: Vec<FileChange>,
+}
+
+// ---------------------------------------------------------------------------
+// MrTab
+// ---------------------------------------------------------------------------
+
+/// Active tab in the MR detail view.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
+pub enum MrTab {
+    /// Overview: description + cross-refs.
+    #[default]
+    Overview,
+    /// File changes list.
+    Files,
+    /// Discussions (general + diff).
+    Discussions,
+}
+
+impl MrTab {
+    /// Cycle to the next tab.
+    #[must_use]
+    pub fn next(self) -> Self {
+        match self {
+            Self::Overview => Self::Files,
+            Self::Files => Self::Discussions,
+            Self::Discussions => Self::Overview,
+        }
+    }
+
+    /// Cycle to the previous tab.
+    #[must_use]
+    pub fn prev(self) -> Self {
+        match self {
+            Self::Overview => Self::Discussions,
+            Self::Files => Self::Overview,
+            Self::Discussions => Self::Files,
+        }
+    }
+
+    /// Human-readable label.
+    #[must_use]
+    pub const fn label(&self) -> &str {
+        match self {
+            Self::Overview => "Overview",
+            Self::Files => "Files",
+            Self::Discussions => "Discussions",
+        }
+    }
+}
+
+// ---------------------------------------------------------------------------
+// MrDetailState
+// ---------------------------------------------------------------------------
 
 /// State for the MR detail screen.
 #[derive(Debug, Default)]
 pub struct MrDetailState {
-    pub key: Option<EntityKey>,
-    pub detail: Option<MrDetail>,
-    pub discussions: Vec<Discussion>,
-    pub scroll_offset: u16,
+    /// Entity key for the currently displayed MR.
+    pub current_key: Option<EntityKey>,
+    /// MR metadata (Phase 1 load).
+    pub metadata: Option<MrMetadata>,
+    /// File changes (loaded with metadata in Phase 1).
+    pub file_changes: Vec<FileChange>,
+    /// Discussion nodes (Phase 2 async load).
+    pub discussions: Vec<DiscussionNode>,
+    /// Whether discussions have finished loading.
+    pub discussions_loaded: bool,
+    /// Cross-references (loaded with metadata in Phase 1).
+    pub cross_refs: Vec<CrossRef>,
+    /// Discussion tree UI state.
+    pub tree_state: DiscussionTreeState,
+    /// Cross-reference list UI state.
+    pub cross_ref_state: CrossRefState,
+    /// Description scroll offset.
+    pub description_scroll: usize,
+    /// File list selected index.
+    pub file_selected: usize,
+    /// File list scroll offset.
+    pub file_scroll: usize,
+    /// Active tab.
+    pub active_tab: MrTab,
+}
+
+impl MrDetailState {
+    /// Reset state for a new MR.
+    pub fn load_new(&mut self, key: EntityKey) {
+        self.current_key = Some(key);
+        self.metadata = None;
+        self.file_changes.clear();
+        self.discussions.clear();
+        self.discussions_loaded = false;
+        self.cross_refs.clear();
+        self.tree_state = DiscussionTreeState::default();
+        self.cross_ref_state = CrossRefState::default();
+        self.description_scroll = 0;
+        self.file_selected = 0;
+        self.file_scroll = 0;
+        self.active_tab = MrTab::Overview;
+    }
+
+    /// Apply Phase 1 data (metadata + cross-refs + file changes).
+    pub fn apply_metadata(&mut self, data: MrDetailData) {
+        self.metadata = Some(data.metadata);
+        self.cross_refs = data.cross_refs;
+        self.file_changes = data.file_changes;
+    }
+
+    /// Apply Phase 2 data (discussions).
+    pub fn apply_discussions(&mut self, discussions: Vec<DiscussionNode>) {
+        self.discussions = discussions;
+        self.discussions_loaded = true;
+    }
+
+    /// Whether we have metadata loaded.
+    #[must_use]
+    pub fn has_metadata(&self) -> bool {
+        self.metadata.is_some()
+    }
+
+    /// Switch to the next tab.
+    pub fn next_tab(&mut self) {
+        self.active_tab = self.active_tab.next();
+    }
+
+    /// Switch to the previous tab.
+    pub fn prev_tab(&mut self) {
+        self.active_tab = self.active_tab.prev();
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Tests
+// ---------------------------------------------------------------------------
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::view::common::cross_ref::CrossRefKind;
+
+    #[test]
+    fn test_mr_detail_state_default() {
+        let state = MrDetailState::default();
+        assert!(state.current_key.is_none());
+        assert!(state.metadata.is_none());
+        assert!(state.discussions.is_empty());
+        assert!(!state.discussions_loaded);
+        assert!(state.file_changes.is_empty());
+        assert_eq!(state.active_tab, MrTab::Overview);
+    }
+
+    #[test]
+    fn test_load_new_resets_state() {
+        let mut state = MrDetailState {
+            discussions_loaded: true,
+            description_scroll: 10,
+            active_tab: MrTab::Files,
+            ..MrDetailState::default()
+        };
+
+        state.load_new(EntityKey::mr(1, 42));
+        assert_eq!(state.current_key, Some(EntityKey::mr(1, 42)));
+        assert!(state.metadata.is_none());
+        assert!(!state.discussions_loaded);
+        assert_eq!(state.description_scroll, 0);
+        assert_eq!(state.active_tab, MrTab::Overview);
+    }
+
+    #[test]
+    fn test_apply_metadata() {
+        let mut state = MrDetailState::default();
+        state.load_new(EntityKey::mr(1, 42));
+
+        let data = MrDetailData {
+            metadata: MrMetadata {
+                iid: 42,
+                project_path: "group/proj".into(),
+                title: "Fix auth".into(),
+                description: "MR description".into(),
+                state: "opened".into(),
+                draft: false,
+                author: "alice".into(),
+                assignees: vec!["bob".into()],
+                reviewers: vec!["carol".into()],
+                labels: vec!["backend".into()],
+                source_branch: "fix-auth".into(),
+                target_branch: "main".into(),
+                merge_status: "mergeable".into(),
+                created_at: 1_700_000_000_000,
+                updated_at: 1_700_000_060_000,
+                merged_at: None,
+                web_url: "https://gitlab.com/group/proj/-/merge_requests/42".into(),
+                discussion_count: 2,
+                file_change_count: 3,
+            },
+            cross_refs: vec![CrossRef {
+                kind: CrossRefKind::RelatedIssue,
+                entity_key: EntityKey::issue(1, 10),
+                label: "Related issue".into(),
+                navigable: true,
+            }],
+            file_changes: vec![FileChange {
+                old_path: None,
+                new_path: "src/auth.rs".into(),
+                change_type: FileChangeType::Modified,
+            }],
+        };
+
+        state.apply_metadata(data);
+        assert!(state.has_metadata());
+        assert_eq!(state.metadata.as_ref().unwrap().iid, 42);
+        assert_eq!(state.cross_refs.len(), 1);
+        assert_eq!(state.file_changes.len(), 1);
+    }
+
+    #[test]
+    fn test_tab_cycling() {
+        let tab = MrTab::Overview;
+        assert_eq!(tab.next(), MrTab::Files);
+        assert_eq!(tab.next().next(), MrTab::Discussions);
+        assert_eq!(tab.next().next().next(), MrTab::Overview);
+
+        assert_eq!(tab.prev(), MrTab::Discussions);
+        assert_eq!(tab.prev().prev(), MrTab::Files);
+    }
+
+    #[test]
+    fn test_tab_labels() {
+        assert_eq!(MrTab::Overview.label(), "Overview");
+        assert_eq!(MrTab::Files.label(), "Files");
+        assert_eq!(MrTab::Discussions.label(), "Discussions");
+    }
+
+    #[test]
+    fn test_file_change_type_icon() {
+        assert_eq!(FileChangeType::Added.icon(), "+");
+        assert_eq!(FileChangeType::Modified.icon(), "~");
+        assert_eq!(FileChangeType::Deleted.icon(), "-");
+        assert_eq!(FileChangeType::Renamed.icon(), "R");
+    }
+
+    #[test]
+    fn test_file_change_type_parse_db() {
+        assert_eq!(FileChangeType::parse_db("added"), FileChangeType::Added);
+        assert_eq!(FileChangeType::parse_db("deleted"), FileChangeType::Deleted);
+        assert_eq!(FileChangeType::parse_db("renamed"), FileChangeType::Renamed);
+        assert_eq!(
+            FileChangeType::parse_db("modified"),
+            FileChangeType::Modified
+        );
+        assert_eq!(
+            FileChangeType::parse_db("unknown"),
+            FileChangeType::Modified
+        );
+    }
+
+    #[test]
+    fn test_next_prev_tab_on_state() {
+        let mut state = MrDetailState::default();
+        assert_eq!(state.active_tab, MrTab::Overview);
+
+        state.next_tab();
+        assert_eq!(state.active_tab, MrTab::Files);
+
+        state.prev_tab();
+        assert_eq!(state.active_tab, MrTab::Overview);
+    }
 }