multica/server/internal/handler/comment.go

package handler

import (
	"context"
	"encoding/json"
	"log/slog"
	"net/http"
	"strconv"
	"time"

	"github.com/go-chi/chi/v5"
	"github.com/jackc/pgx/v5/pgtype"
	"github.com/multica-ai/multica/server/internal/logger"
	"github.com/multica-ai/multica/server/internal/mention"
	"github.com/multica-ai/multica/server/internal/service"
	"github.com/multica-ai/multica/server/internal/util"
	db "github.com/multica-ai/multica/server/pkg/db/generated"
	"github.com/multica-ai/multica/server/pkg/protocol"
)

type CommentResponse struct {
	ID             string               `json:"id"`
	IssueID        string               `json:"issue_id"`
	AuthorType     string               `json:"author_type"`
	AuthorID       string               `json:"author_id"`
	Content        string               `json:"content"`
	Type           string               `json:"type"`
	ParentID       *string              `json:"parent_id"`
	CreatedAt      string               `json:"created_at"`
	UpdatedAt      string               `json:"updated_at"`
	ResolvedAt     *string              `json:"resolved_at"`
	ResolvedByType *string              `json:"resolved_by_type"`
	ResolvedByID   *string              `json:"resolved_by_id"`
	Reactions      []ReactionResponse   `json:"reactions"`
	Attachments    []AttachmentResponse `json:"attachments"`
}

func commentToResponse(c db.Comment, reactions []ReactionResponse, attachments []AttachmentResponse) CommentResponse {
	if reactions == nil {
		reactions = []ReactionResponse{}
	}
	if attachments == nil {
		attachments = []AttachmentResponse{}
	}
	return CommentResponse{
		ID:             uuidToString(c.ID),
		IssueID:        uuidToString(c.IssueID),
		AuthorType:     c.AuthorType,
		AuthorID:       uuidToString(c.AuthorID),
		Content:        c.Content,
		Type:           c.Type,
		ParentID:       uuidToPtr(c.ParentID),
		CreatedAt:      timestampToString(c.CreatedAt),
		UpdatedAt:      timestampToString(c.UpdatedAt),
		ResolvedAt:     timestampToPtr(c.ResolvedAt),
		ResolvedByType: textToPtr(c.ResolvedByType),
		ResolvedByID:   uuidToPtr(c.ResolvedByID),
		Reactions:      reactions,
		Attachments:    attachments,
	}
}

// commentHardCap bounds the comments returned per issue. Sized as a defensive
// safety net rather than a UX paging window: prod p99 is ~30 comments and
// the all-time max observed is ~1.1k, so 2000 leaves ~2x headroom while still
// preventing a runaway response if some user manages to accumulate a wild
// number of rows on a single issue.
const commentHardCap = 2000

// ListComments returns comments for an issue. The default behaviour is
// unchanged — full chronological dump capped at commentHardCap — so existing
// callers and the desktop UI keep working as-is. Three optional query params
// give agent-style readers a thread-aware view that scales to long issues
// without dragging every prior comment into context:
//
//   - thread=<comment-uuid> — return the root of the thread containing this
//     comment plus every descendant. The anchor may be a root or any reply;
//     the server walks up to the root via a recursive CTE, so callers do not
//     need to know whether the id they have is a root.
//   - recent=<N> — return the N most recently active threads (root + every
//     descendant per thread). A thread's recency is MAX(created_at) across
//     the whole subtree, so a stale-but-recently-replied thread ranks ahead
//     of an active-but-quiet one. Row-based "newest N comments" is
//     deliberately NOT exposed — it surfaces unrelated thread tails and
//     hides relevant history (#2340).
//   - before=<RFC3339> + before-id=<uuid> — thread cursor. The pair points at
//     a thread's (last_activity_at, root_id); the next page returns threads
//     strictly less recent. Both must be set together — a timestamp-only
//     cursor cannot tie-break two threads whose last_activity falls in the
//     same microsecond. The cursor for the next page is emitted via the
//     X-Multica-Next-Before / X-Multica-Next-Before-Id response headers.
//
// Combination rules (kept narrow on purpose — Elon flagged the matrix risk):
//
//   - thread is exclusive with recent and before/before-id. Asking for "the
//     most recent N within thread X" or "thread X but only before T" mixes
//     two different navigation models and is rejected with 400.
//   - thread may combine with since (incremental polling of one thread).
//   - recent may combine with before/before-id (scroll older threads) and
//     with since (recent activity in a window).
//   - since may combine with anything except (thread + recent / before).
//
// The response body is always chronological (oldest → newest); under recent
// that means threads are listed oldest-active first and the freshest thread
// sits at the tail, closest to "now" in an agent prompt.
func (h *Handler) ListComments(w http.ResponseWriter, r *http.Request) {
	issueID := chi.URLParam(r, "id")
	issue, ok := h.loadIssueForUser(w, r, issueID)
	if !ok {
		return
	}

	q := r.URL.Query()

	var sinceTime pgtype.Timestamptz
	if v := q.Get("since"); v != "" {
		t, err := time.Parse(time.RFC3339Nano, v)
		if err != nil {
			// Fall back to RFC3339 for backwards-compat with the original CLI.
			t, err = time.Parse(time.RFC3339, v)
			if err != nil {
				writeError(w, http.StatusBadRequest, "invalid since parameter; expected RFC3339 format")
				return
			}
		}
		sinceTime = pgtype.Timestamptz{Time: t, Valid: true}
	}

	threadStr := q.Get("thread")
	recentStr := q.Get("recent")
	beforeTimeStr := q.Get("before")
	beforeIDStr := q.Get("before_id")
	if beforeIDStr == "" {
		// Accept hyphenated alias to match CLI flag convention.
		beforeIDStr = q.Get("before-id")
	}

	// --- combination validation ----------------------------------------
	if threadStr != "" && recentStr != "" {
		writeError(w, http.StatusBadRequest, "thread and recent are mutually exclusive")
		return
	}
	if threadStr != "" && (beforeTimeStr != "" || beforeIDStr != "") {
		writeError(w, http.StatusBadRequest, "thread cannot be combined with before / before_id")
		return
	}
	if (beforeTimeStr == "") != (beforeIDStr == "") {
		writeError(w, http.StatusBadRequest, "before and before_id must be set together (composite cursor)")
		return
	}
	// Cursor only makes sense as "scroll older within a recent window". A
	// cursor without `recent` would otherwise be silently dropped by
	// fetchCommentsForList and fall back to the default / since path —
	// returning a full timeline that the caller did not ask for. Reject
	// loudly so the API surface matches the documented semantics.
	if beforeTimeStr != "" && recentStr == "" {
		writeError(w, http.StatusBadRequest, "before / before_id require recent (cursor scrolls within a recent window)")
		return
	}

	// --- parse cursor / recent ----------------------------------------
	var beforeCursor pgtype.Timestamptz
	var beforeUUID pgtype.UUID
	hasCursor := false
	if beforeTimeStr != "" {
		t, err := time.Parse(time.RFC3339Nano, beforeTimeStr)
		if err != nil {
			t, err = time.Parse(time.RFC3339, beforeTimeStr)
			if err != nil {
				writeError(w, http.StatusBadRequest, "invalid before parameter; expected RFC3339 format")
				return
			}
		}
		beforeCursor = pgtype.Timestamptz{Time: t, Valid: true}
		uuid, perr := util.ParseUUID(beforeIDStr)
		if perr != nil {
			writeError(w, http.StatusBadRequest, "invalid before_id parameter; expected UUID")
			return
		}
		beforeUUID = uuid
		hasCursor = true
	}

	recentN := 0
	if recentStr != "" {
		n, err := strconv.Atoi(recentStr)
		if err != nil || n <= 0 {
			writeError(w, http.StatusBadRequest, "invalid recent parameter; expected positive integer")
			return
		}
		if n > commentHardCap {
			n = commentHardCap
		}
		recentN = n
	}

	result, err := h.fetchCommentsForList(r.Context(), fetchCommentsArgs{
		Issue:        issue,
		Since:        sinceTime,
		ThreadAnchor: threadStr,
		RecentN:      recentN,
		HasCursor:    hasCursor,
		BeforeAt:     beforeCursor,
		BeforeID:     beforeUUID,
	})
	if err != nil {
		switch err {
		case errCommentThreadNotFound:
			writeError(w, http.StatusNotFound, "thread anchor not found in this issue")
			return
		case errCommentThreadBadID:
			writeError(w, http.StatusBadRequest, "invalid thread parameter; expected UUID")
			return
		default:
			writeError(w, http.StatusInternalServerError, "failed to list comments")
			return
		}
	}

	commentIDs := make([]pgtype.UUID, len(result.Comments))
	for i, c := range result.Comments {
		commentIDs[i] = c.ID
	}
	grouped := h.groupReactions(r, commentIDs)
	groupedAtt := h.groupAttachments(r, commentIDs)

	resp := make([]CommentResponse, len(result.Comments))
	for i, c := range result.Comments {
		cid := uuidToString(c.ID)
		resp[i] = commentToResponse(c, grouped[cid], groupedAtt[cid])
	}

	// Emit the next thread cursor as response headers when the recent page is
	// likely not the last one (returned a full page of threads). Headers stay
	// out of the JSON body so the default flat-array response shape — which
	// the desktop UI and existing callers depend on — is unchanged.
	if result.NextBefore != "" && result.NextBeforeID != "" {
		w.Header().Set("X-Multica-Next-Before", result.NextBefore)
		w.Header().Set("X-Multica-Next-Before-Id", result.NextBeforeID)
	}

	writeJSON(w, http.StatusOK, resp)
}

// fetchCommentsArgs bundles the parsed query params so fetchCommentsForList
// stays readable. Sentinel errors below let the caller turn DB-layer outcomes
// into the right HTTP status without leaking SQL details.
type fetchCommentsArgs struct {
	Issue        db.Issue
	Since        pgtype.Timestamptz
	ThreadAnchor string
	RecentN      int
	HasCursor    bool
	BeforeAt     pgtype.Timestamptz
	BeforeID     pgtype.UUID
}

// fetchCommentsResult carries both the materialised comments and (for the
// recent/thread-grouped path) the cursor to use for the next page. Cursor
// fields are empty strings when there is no next page or the path does not
// support cursors.
type fetchCommentsResult struct {
	Comments     []db.Comment
	NextBefore   string
	NextBeforeID string
}

var (
	errCommentThreadNotFound = &commentFetchError{"thread anchor not found"}
	errCommentThreadBadID    = &commentFetchError{"invalid thread anchor id"}
)

type commentFetchError struct{ msg string }

func (e *commentFetchError) Error() string { return e.msg }

func (h *Handler) fetchCommentsForList(ctx context.Context, args fetchCommentsArgs) (fetchCommentsResult, error) {
	issue := args.Issue

	// Thread-scoped read. Server resolves the anchor → root via recursive
	// CTE, so we don't have to assume two-layer flat threads here.
	if args.ThreadAnchor != "" {
		anchor, err := util.ParseUUID(args.ThreadAnchor)
		if err != nil {
			return fetchCommentsResult{}, errCommentThreadBadID
		}
		rows, err := h.Queries.ListThreadCommentsForIssue(ctx, db.ListThreadCommentsForIssueParams{
			AnchorID:    anchor,
			IssueID:     issue.ID,
			WorkspaceID: issue.WorkspaceID,
			RowLimit:    commentHardCap,
		})
		if err != nil {
			return fetchCommentsResult{}, err
		}
		if len(rows) == 0 {
			return fetchCommentsResult{}, errCommentThreadNotFound
		}
		out := make([]db.Comment, 0, len(rows))
		for _, r := range rows {
			if args.Since.Valid && !r.CreatedAt.Time.After(args.Since.Time) {
				continue
			}
			out = append(out, db.Comment{
				ID:             r.ID,
				IssueID:        r.IssueID,
				AuthorType:     r.AuthorType,
				AuthorID:       r.AuthorID,
				Content:        r.Content,
				Type:           r.Type,
				CreatedAt:      r.CreatedAt,
				UpdatedAt:      r.UpdatedAt,
				ParentID:       r.ParentID,
				WorkspaceID:    r.WorkspaceID,
				ResolvedAt:     r.ResolvedAt,
				ResolvedByType: r.ResolvedByType,
				ResolvedByID:   r.ResolvedByID,
			})
		}
		return fetchCommentsResult{Comments: out}, nil
	}

	// Thread-grouped recent read: N most recently active threads.
	if args.RecentN > 0 {
		rows, err := h.Queries.ListRecentThreadCommentsForIssue(ctx, db.ListRecentThreadCommentsForIssueParams{
			IssueID:     issue.ID,
			WorkspaceID: issue.WorkspaceID,
			HasCursor:   args.HasCursor,
			BeforeAt:    args.BeforeAt,
			BeforeID:    args.BeforeID,
			ThreadLimit: int32(args.RecentN),
		})
		if err != nil {
			return fetchCommentsResult{}, err
		}

		// The SQL already orders rows by (last_activity_at ASC, root_id ASC,
		// created_at ASC, id ASC), so the OLDEST-active thread sits at the
		// head and the FRESHEST thread at the tail. Walk the rows once to:
		//   1. Strip the thread-metadata columns down to db.Comment for the
		//      caller (uniform shape across paths).
		//   2. Count distinct threads in the page so we know whether a "next
		//      older page" is likely to exist.
		//   3. Capture the head thread's (last_activity_at, root_id) — that
		//      is the cursor for the next page (next page = threads strictly
		//      less recent than this one).
		comments := make([]db.Comment, 0, len(rows))
		var headRoot pgtype.UUID
		var headLast pgtype.Timestamptz
		seenRoot := map[string]struct{}{}
		for _, r := range rows {
			if !headRoot.Valid {
				headRoot = r.ThreadRootID
				headLast = r.ThreadLastActivityAt
			}
			seenRoot[uuidToString(r.ThreadRootID)] = struct{}{}
			// Since filter on the recent path: drop comments older than
			// `since`. Done in-memory so we keep the thread-grouped
			// semantics from the query (don't pre-filter rows before the
			// MAX(created_at) ranking — that would silently downgrade a
			// thread whose most recent activity falls inside the window).
			if args.Since.Valid && !r.CreatedAt.Time.After(args.Since.Time) {
				continue
			}
			comments = append(comments, db.Comment{
				ID:             r.ID,
				IssueID:        r.IssueID,
				AuthorType:     r.AuthorType,
				AuthorID:       r.AuthorID,
				Content:        r.Content,
				Type:           r.Type,
				CreatedAt:      r.CreatedAt,
				UpdatedAt:      r.UpdatedAt,
				ParentID:       r.ParentID,
				WorkspaceID:    r.WorkspaceID,
				ResolvedAt:     r.ResolvedAt,
				ResolvedByType: r.ResolvedByType,
				ResolvedByID:   r.ResolvedByID,
			})
		}

		// Only emit a cursor when the page is full. Fewer threads than
		// requested ⇒ the SELECT exhausted matching threads, so there is
		// no older page to scroll to.
		//
		// Additionally suppress the cursor when `since` is set and the head
		// thread's last_activity_at is already <= since. The pagination
		// walks threads in strictly decreasing last_activity_at, so every
		// older page has last_activity_at strictly less than the head's —
		// if the head itself can't satisfy `> since`, no older thread can
		// either. Predicating on the head (not on whether `comments` is
		// empty) also catches the mixed case where this page keeps rows
		// from fresher threads but the head thread is already past `since`.
		// Flagged by Elon in #2787's second review (MUL-2340 nit).
		out := fetchCommentsResult{Comments: comments}
		emitCursor := len(seenRoot) >= args.RecentN && headRoot.Valid && headLast.Valid
		if emitCursor && args.Since.Valid && !headLast.Time.After(args.Since.Time) {
			emitCursor = false
		}
		if emitCursor {
			out.NextBefore = headLast.Time.UTC().Format(time.RFC3339Nano)
			out.NextBeforeID = uuidToString(headRoot)
		}
		return out, nil
	}

	// Default + since paths preserved verbatim (no behavioural change for
	// existing callers).
	if args.Since.Valid {
		comments, err := h.Queries.ListCommentsSinceForIssue(ctx, db.ListCommentsSinceForIssueParams{
			IssueID:     issue.ID,
			WorkspaceID: issue.WorkspaceID,
			CreatedAt:   args.Since,
			Limit:       commentHardCap,
		})
		return fetchCommentsResult{Comments: comments}, err
	}
	comments, err := h.Queries.ListCommentsForIssue(ctx, db.ListCommentsForIssueParams{
		IssueID:     issue.ID,
		WorkspaceID: issue.WorkspaceID,
		Limit:       commentHardCap,
	})
	return fetchCommentsResult{Comments: comments}, err
}

type CreateCommentRequest struct {
	Content       string   `json:"content"`
	Type          string   `json:"type"`
	ParentID      *string  `json:"parent_id"`
	AttachmentIDs []string `json:"attachment_ids"`
}

func (h *Handler) CreateComment(w http.ResponseWriter, r *http.Request) {
	issueID := chi.URLParam(r, "id")
	issue, ok := h.loadIssueForUser(w, r, issueID)
	if !ok {
		return
	}

	userID, ok := requireUserID(w, r)
	if !ok {
		return
	}

	var req CreateCommentRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeError(w, http.StatusBadRequest, "invalid request body")
		return
	}

	if req.Content == "" {
		writeError(w, http.StatusBadRequest, "content is required")
		return
	}
	if req.Type == "" {
		req.Type = "comment"
	}

	var parentID pgtype.UUID
	var parentComment *db.Comment
	if req.ParentID != nil {
		var parsed pgtype.UUID
		parsed, ok = parseUUIDOrBadRequest(w, *req.ParentID, "parent_id")
		if !ok {
			return
		}
		parentID = parsed
		parent, err := h.Queries.GetComment(r.Context(), parentID)
		if err != nil || uuidToString(parent.IssueID) != uuidToString(issue.ID) {
			writeError(w, http.StatusBadRequest, "invalid parent comment")
			return
		}
		parentComment = &parent
	}

	attachmentIDs, ok := parseUUIDSliceOrBadRequest(w, req.AttachmentIDs, "attachment_ids")
	if !ok {
		return
	}

	// Determine author identity: agent (via X-Agent-ID header) or member.
	authorType, authorID := h.resolveActor(r, userID, uuidToString(issue.WorkspaceID))

	// Defense against resumed-session drift: when an agent posts from inside a
	// comment-triggered task AND the comment is being posted on that same
	// issue, the parent_id must exactly match the task's trigger comment.
	// Resumed Claude sessions otherwise carry forward a previous turn's
	// --parent UUID and silently misplace the reply.
	//
	// The task.IssueID scope is important: the CLI stamps X-Task-ID on every
	// request, so an agent legitimately commenting on a different issue must
	// not be blocked by its current task's trigger. Assignment-triggered
	// tasks (no TriggerCommentID) are also unaffected.
	if authorType == "agent" {
		if taskIDHeader := r.Header.Get("X-Task-ID"); taskIDHeader != "" {
			taskUUID, parseErr := util.ParseUUID(taskIDHeader)
			if parseErr == nil {
				task, err := h.Queries.GetAgentTask(r.Context(), taskUUID)
				if err == nil && task.IssueID.Valid && uuidToString(task.IssueID) == uuidToString(issue.ID) {
					if task.TriggerCommentID.Valid {
						if uuidToString(parentID) != uuidToString(task.TriggerCommentID) {
							writeError(w, http.StatusConflict,
								"parent_id must equal this task's trigger comment id ("+uuidToString(task.TriggerCommentID)+")")
							return
						}
					}
					noAction, checkErr := service.HasSquadLeaderNoActionEvaluationForTask(r.Context(), h.Queries, task)
					if checkErr != nil {
						slog.Warn("checking squad leader no_action evaluation failed", append(logger.RequestAttrs(r),
							"error", checkErr,
							"task_id", taskIDHeader,
							"issue_id", issueID,
						)...)
					} else if noAction {
						writeError(w, http.StatusConflict, "squad leader recorded no_action; comments are not allowed for this task")
						return
					}
				}
			}
		}
	}

	// Expand bare issue identifiers (e.g. MUL-117) into mention links.
	req.Content = mention.ExpandIssueIdentifiers(r.Context(), h.Queries, issue.WorkspaceID, req.Content)

	// NOTE: Comment content is stored as Markdown source. XSS is handled at the
	// rendering layer (rehype-sanitize) and at the editor layer
	// (@tiptap/markdown with html:false). Running an HTML sanitizer here would
	// entity-encode Markdown syntax characters (>, ", &, <) and corrupt the
	// source. See issue #1303 / discussion in MUL-1119, MUL-1125.

	comment, err := h.Queries.CreateComment(r.Context(), db.CreateCommentParams{
		IssueID:     issue.ID,
		WorkspaceID: issue.WorkspaceID,
		AuthorType:  authorType,
		AuthorID:    parseUUID(authorID),
		Content:     req.Content,
		Type:        req.Type,
		ParentID:    parentID,
	})
	if err != nil {
		slog.Warn("create comment failed", append(logger.RequestAttrs(r), "error", err, "issue_id", issueID)...)
		writeError(w, http.StatusInternalServerError, "failed to create comment: "+err.Error())
		return
	}

	// Link uploaded attachments to this comment.
	if len(attachmentIDs) > 0 {
		h.linkAttachmentsByIDs(r.Context(), comment.ID, issue.ID, attachmentIDs)
	}

	// Fetch linked attachments so the response includes them.
	groupedAtt := h.groupAttachments(r, []pgtype.UUID{comment.ID})
	resp := commentToResponse(comment, nil, groupedAtt[uuidToString(comment.ID)])
	slog.Info("comment created", append(logger.RequestAttrs(r), "comment_id", uuidToString(comment.ID), "issue_id", issueID)...)
	h.publish(protocol.EventCommentCreated, uuidToString(issue.WorkspaceID), authorType, authorID, map[string]any{
		"comment":             resp,
		"issue_title":         issue.Title,
		"issue_assignee_type": textToPtr(issue.AssigneeType),
		"issue_assignee_id":   uuidToPtr(issue.AssigneeID),
		"issue_status":        issue.Status,
	})

	// A reply in a resolved thread re-opens it. Done after CreateComment commits
	// so the reply is visible regardless of the unresolve outcome. Shared with
	// the agent task path (TaskService.createAgentComment) — both reply paths
	// must keep the resolved root in sync.
	h.TaskService.AutoUnresolveThreadOnReply(r.Context(), parentComment, uuidToString(issue.WorkspaceID), authorType, authorID)

	// If the issue is assigned to an agent with on_comment trigger, enqueue a new task.
	// Skip when the comment comes from the assigned agent itself to avoid loops.
	// Also skip when the comment @mentions others but not the assignee agent —
	// the user is talking to someone else, not requesting work from the assignee.
	// Also skip when replying in a member-started thread without mentioning the
	// assignee — the user is continuing a member-to-member conversation.
	if authorType == "member" && h.shouldEnqueueOnComment(r.Context(), issue) &&
		!h.commentMentionsOthersButNotAssignee(comment.Content, issue) &&
		!h.isReplyToMemberThread(r.Context(), parentComment, comment.Content, issue) {
		// Always use the current comment as the trigger so the agent reads
		// the actual new reply, not the thread root. Reply placement (flat
		// thread grouping) is handled downstream by createAgentComment,
		// which resolves parent_id to the thread root before posting. This
		// mirrors the mention path's behavior (see enqueueMentionedAgentTasks).
		if _, err := h.TaskService.EnqueueTaskForIssue(r.Context(), issue, comment.ID); err != nil {
			slog.Warn("enqueue agent task on comment failed", "issue_id", issueID, "error", err)
		}
	}

	// Squad trigger: if the issue is assigned to a squad, trigger the squad leader.
	// Skip when the comment author is the leader (prevent internal loops), or
	// when a member explicitly @mentions anyone (agent/member/squad/all) — that
	// counts as deliberate routing and the leader stays out.
	if h.shouldEnqueueSquadLeaderOnComment(r.Context(), issue, comment.Content, authorType, authorID) {
		h.enqueueSquadLeaderTask(r.Context(), issue, comment.ID, authorType, authorID)
	}

	// Trigger @mentioned agents: parse agent mentions and enqueue tasks for each.
	// Pass parentComment so that replies inherit mentions from the thread root.
	h.enqueueMentionedAgentTasks(r.Context(), issue, comment, parentComment, authorType, authorID)

	writeJSON(w, http.StatusCreated, resp)
}

// commentMentionsOthersButNotAssignee returns true if the comment @mentions
// anyone but does NOT @mention the issue's assignee agent. This is used to
// suppress the on_comment trigger when the user is directing their comment at
// someone else (e.g. sharing results with a colleague, asking another agent).
// @all is treated as a broadcast — it suppresses the trigger because the user
// is announcing to everyone, not specifically requesting work from the agent.
func (h *Handler) commentMentionsOthersButNotAssignee(content string, issue db.Issue) bool {
	mentions := util.ParseMentions(content)
	// Filter out issue mentions — they are cross-references, not @people.
	filtered := mentions[:0]
	for _, m := range mentions {
		if m.Type != "issue" {
			filtered = append(filtered, m)
		}
	}
	mentions = filtered
	if len(mentions) == 0 {
		return false // No mentions (or only issue refs) — normal on_comment behavior
	}
	// @all is a broadcast to all members — suppress agent trigger.
	if util.HasMentionAll(mentions) {
		return true
	}
	if !issue.AssigneeID.Valid {
		return true // No assignee — mentions target others
	}
	assigneeID := uuidToString(issue.AssigneeID)
	for _, m := range mentions {
		if m.ID == assigneeID {
			return false // Assignee is mentioned — allow trigger
		}
	}
	return true // Others mentioned but not assignee — suppress trigger
}

// isReplyToMemberThread returns true if the comment is a reply in a thread
// started by a member and does NOT @mention the issue's assignee agent.
// When a member replies in a member-started thread, they are most likely
// continuing a human conversation — not requesting work from the assigned agent.
// Replying to an agent-started thread, or explicitly @mentioning the assignee
// in the reply, still triggers on_comment as expected.
// If the parent (thread root) itself @mentions the assignee, the thread is
// considered a conversation with the agent, so replies are allowed to trigger.
// If the assigned agent has already replied in the thread, the member is
// conversing with the agent, so replies are allowed to trigger.
func (h *Handler) isReplyToMemberThread(ctx context.Context, parent *db.Comment, content string, issue db.Issue) bool {
	if parent == nil {
		return false // Not a reply — normal top-level comment
	}
	if parent.AuthorType != "member" {
		return false // Thread started by an agent — allow trigger
	}
	// Thread was started by a member. Suppress on_comment unless the reply
	// or the parent explicitly @mentions the assignee agent, or the agent
	// has already participated in this thread.
	if !issue.AssigneeID.Valid {
		return true // No assignee to mention
	}
	assigneeID := uuidToString(issue.AssigneeID)
	// Check current comment mentions.
	for _, m := range util.ParseMentions(content) {
		if m.ID == assigneeID {
			return false // Assignee explicitly mentioned in reply — allow trigger
		}
	}
	// Check parent (thread root) mentions — if the thread was started by
	// mentioning the assignee, replies continue that conversation.
	for _, m := range util.ParseMentions(parent.Content) {
		if m.ID == assigneeID {
			return false // Assignee mentioned in thread root — allow trigger
		}
	}
	// Check if the assigned agent has already replied in this thread —
	// if so, the member is continuing a conversation with the agent.
	if h.Queries != nil {
		hasReplied, err := h.Queries.HasAgentRepliedInThread(ctx, db.HasAgentRepliedInThreadParams{
			ParentID: parent.ID,
			AgentID:  issue.AssigneeID,
		})
		if err == nil && hasReplied {
			return false // Agent participated in thread — allow trigger
		}
	}
	return true // Reply to member thread without agent participation — suppress
}

// shouldInheritParentMentions decides whether a reply with no explicit
// mentions should inherit the parent (thread root) comment's mentions.
//
// Inheritance lets a member who started a thread by @mentioning an agent
// continue the conversation with that agent without re-typing the mention
// on every follow-up reply.
//
// It is intentionally narrow:
//
//   - Only when the reply contains zero mentions of its own. Any explicit
//     mention in the reply is a deliberate choice about who to involve.
//   - Only when the reply author is a member. Agent-authored replies must
//     never inherit, otherwise an agent posting in a thread whose root
//     mentioned another agent would re-trigger that agent and create a loop.
//   - Only when the parent author is a member. When an agent authors a
//     comment that @mentions another agent, it is typically a one-shot
//     delegation (e.g. an agent posting a PR completion that @mentions a
//     reviewer agent). Subsequent member follow-ups in the same thread are
//     directed at the assignee, not at the delegated agent — inheriting
//     would re-trigger the delegated agent on every plain reply.
func shouldInheritParentMentions(parentComment *db.Comment, replyMentions []util.Mention, replyAuthorType string) bool {
	if parentComment == nil {
		return false
	}
	if len(replyMentions) > 0 {
		return false
	}
	if replyAuthorType == "agent" {
		return false
	}
	return parentComment.AuthorType == "member"
}

// enqueueMentionedAgentTasks parses @agent mentions from comment content and
// enqueues a task for each mentioned agent. When parentComment is non-nil
// (i.e. the comment is a reply), mentions from the parent (thread root) are
// also included so that agents mentioned in the top-level comment are
// re-triggered by subsequent replies in the same thread — unless the reply
// explicitly @mentions only non-agent entities (members, issues), which
// signals the user is talking to other people and not the agent.
// Skips self-mentions, agents with on_mention trigger disabled, and private
// agents mentioned by non-owner members (only the agent owner or workspace
// admin/owner can mention a private agent).
// Note: no status gate here — @mention is an explicit action and should work
// even on done/cancelled issues (the agent can reopen the issue if needed).
func (h *Handler) enqueueMentionedAgentTasks(ctx context.Context, issue db.Issue, comment db.Comment, parentComment *db.Comment, authorType, authorID string) {
	wsID := uuidToString(issue.WorkspaceID)
	mentions := util.ParseMentions(comment.Content)
	if shouldInheritParentMentions(parentComment, mentions, authorType) {
		mentions = util.ParseMentions(parentComment.Content)
	}
	for _, m := range mentions {
		if m.Type == "squad" {
			// @squad mention → trigger the squad's leader agent.
			squadUUID := parseUUID(m.ID)
			squad, err := h.Queries.GetSquadInWorkspace(ctx, db.GetSquadInWorkspaceParams{
				ID:          squadUUID,
				WorkspaceID: issue.WorkspaceID,
			})
			if err != nil {
				continue
			}
			leaderID := squad.LeaderID
			// Prevent self-trigger only when the agent's last activity on this
			// issue was itself a leader task. An agent that holds both the
			// leader and a worker role in the squad must still wake its
			// leader role after posting a comment from its worker task.
			if authorType == "agent" && authorID == uuidToString(leaderID) &&
				h.lastTaskWasLeader(ctx, issue.ID, leaderID) {
				continue
			}
			// Verify leader agent is ready (has runtime, not archived).
			agent, err := h.Queries.GetAgentInWorkspace(ctx, db.GetAgentInWorkspaceParams{
				ID:          leaderID,
				WorkspaceID: issue.WorkspaceID,
			})
			if err != nil || !agent.RuntimeID.Valid || agent.ArchivedAt.Valid {
				continue
			}
			// Private-agent gate: prevent triggering a private leader via squad mention.
			if !h.canAccessPrivateAgent(ctx, agent, authorType, authorID, wsID) {
				continue
			}
			// Dedup: skip if leader already has a pending task for this issue.
			hasPending, err := h.Queries.HasPendingTaskForIssueAndAgent(ctx, db.HasPendingTaskForIssueAndAgentParams{
				IssueID: issue.ID,
				AgentID: leaderID,
			})
			if err != nil || hasPending {
				continue
			}
			if _, err := h.TaskService.EnqueueTaskForSquadLeader(ctx, issue, leaderID, comment.ID); err != nil {
				slog.Warn("enqueue squad leader mention task failed", "issue_id", uuidToString(issue.ID), "squad_id", m.ID, "error", err)
			}
			continue
		}
		if m.Type != "agent" {
			continue
		}
		// Prevent self-trigger: skip if the comment author is this agent.
		if authorType == "agent" && authorID == m.ID {
			continue
		}
		agentUUID := parseUUID(m.ID)
		// Load the agent scoped to the current issue's workspace. Using the
		// bare GetAgent here would let a mention resolve to an agent in a
		// different workspace, and the visibility check below would then be
		// applied against the wrong workspace's roles (a workspace owner in
		// THIS workspace would pass the gate for a private agent that lives
		// in someone else's workspace).
		agent, err := h.Queries.GetAgentInWorkspace(ctx, db.GetAgentInWorkspaceParams{
			ID:          agentUUID,
			WorkspaceID: issue.WorkspaceID,
		})
		if err != nil || !agent.RuntimeID.Valid || agent.ArchivedAt.Valid {
			continue
		}
		// Private-agent gate (member→private requires allowed_principals;
		// agent→agent always passes).
		if !h.canAccessPrivateAgent(ctx, agent, authorType, authorID, wsID) {
			continue
		}
		// Dedup: skip if this agent already has a pending task for this issue.
		hasPending, err := h.Queries.HasPendingTaskForIssueAndAgent(ctx, db.HasPendingTaskForIssueAndAgentParams{
			IssueID: issue.ID,
			AgentID: agentUUID,
		})
		if err != nil || hasPending {
			continue
		}
		// Always use the current comment as the trigger so the agent reads the
		// actual reply that mentioned it, not the thread root.
		if _, err := h.TaskService.EnqueueTaskForMention(ctx, issue, agentUUID, comment.ID); err != nil {
			slog.Warn("enqueue mention agent task failed", "issue_id", uuidToString(issue.ID), "agent_id", m.ID, "error", err)
		}
	}
}

func (h *Handler) UpdateComment(w http.ResponseWriter, r *http.Request) {
	commentId := chi.URLParam(r, "commentId")

	userID, ok := requireUserID(w, r)
	if !ok {
		return
	}
	commentUUID, ok := parseUUIDOrBadRequest(w, commentId, "comment id")
	if !ok {
		return
	}

	// Load comment scoped to current workspace.
	workspaceID := h.resolveWorkspaceID(r)
	wsUUID, ok := parseUUIDOrBadRequest(w, workspaceID, "workspace id")
	if !ok {
		return
	}
	existing, err := h.Queries.GetCommentInWorkspace(r.Context(), db.GetCommentInWorkspaceParams{
		ID:          commentUUID,
		WorkspaceID: wsUUID,
	})
	if err != nil {
		writeError(w, http.StatusNotFound, "comment not found")
		return
	}

	member, ok := h.workspaceMember(w, r, workspaceID)
	if !ok {
		return
	}

	actorType, actorID := h.resolveActor(r, userID, workspaceID)
	isAuthor := existing.AuthorType == actorType && uuidToString(existing.AuthorID) == actorID
	isAdmin := roleAllowed(member.Role, "owner", "admin")
	if !isAuthor && !isAdmin {
		writeError(w, http.StatusForbidden, "only comment author or admin can edit")
		return
	}

	var req struct {
		Content       string   `json:"content"`
		AttachmentIDs []string `json:"attachment_ids"`
	}
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeError(w, http.StatusBadRequest, "invalid request body")
		return
	}
	if req.Content == "" {
		writeError(w, http.StatusBadRequest, "content is required")
		return
	}

	attachmentIDs, ok := parseUUIDSliceOrBadRequest(w, req.AttachmentIDs, "attachment_ids")
	if !ok {
		return
	}

	// NOTE: See CreateComment — Markdown is sanitized at render/edit time, not here.

	comment, err := h.Queries.UpdateComment(r.Context(), db.UpdateCommentParams{
		ID:      commentUUID,
		Content: req.Content,
	})
	if err != nil {
		slog.Warn("update comment failed", append(logger.RequestAttrs(r), "error", err, "comment_id", commentId)...)
		writeError(w, http.StatusInternalServerError, "failed to update comment")
		return
	}

	// Bind any newly uploaded attachments referenced in the edited content so
	// they appear in the timeline's comment.attachments after refresh. Existing
	// attachments already point at this comment via the upload flow; passing
	// them again is a no-op at the SQL level.
	if len(attachmentIDs) > 0 {
		h.linkAttachmentsByIDs(r.Context(), comment.ID, existing.IssueID, attachmentIDs)
	}

	// Fetch reactions and attachments for the updated comment.
	grouped := h.groupReactions(r, []pgtype.UUID{comment.ID})
	groupedAtt := h.groupAttachments(r, []pgtype.UUID{comment.ID})
	cid := uuidToString(comment.ID)
	resp := commentToResponse(comment, grouped[cid], groupedAtt[cid])
	slog.Info("comment updated", append(logger.RequestAttrs(r), "comment_id", commentId)...)
	h.publish(protocol.EventCommentUpdated, workspaceID, actorType, actorID, map[string]any{"comment": resp})
	writeJSON(w, http.StatusOK, resp)
}

func (h *Handler) DeleteComment(w http.ResponseWriter, r *http.Request) {
	commentId := chi.URLParam(r, "commentId")

	userID, ok := requireUserID(w, r)
	if !ok {
		return
	}

	commentUUID, ok := parseUUIDOrBadRequest(w, commentId, "comment id")
	if !ok {
		return
	}

	// Load comment scoped to current workspace.
	workspaceID := h.resolveWorkspaceID(r)
	wsUUID, ok := parseUUIDOrBadRequest(w, workspaceID, "workspace id")
	if !ok {
		return
	}
	comment, err := h.Queries.GetCommentInWorkspace(r.Context(), db.GetCommentInWorkspaceParams{
		ID:          commentUUID,
		WorkspaceID: wsUUID,
	})
	if err != nil {
		writeError(w, http.StatusNotFound, "comment not found")
		return
	}

	member, ok := h.workspaceMember(w, r, workspaceID)
	if !ok {
		return
	}

	actorType, actorID := h.resolveActor(r, userID, workspaceID)
	isAuthor := comment.AuthorType == actorType && uuidToString(comment.AuthorID) == actorID
	isAdmin := roleAllowed(member.Role, "owner", "admin")
	if !isAuthor && !isAdmin {
		writeError(w, http.StatusForbidden, "only comment author or admin can delete")
		return
	}

	// Collect attachment URLs before CASCADE delete removes them.
	attachmentURLs, _ := h.Queries.ListAttachmentURLsByCommentID(r.Context(), comment.ID)

	// Cancel any active tasks triggered by this comment so the agent does not
	// run with the now-deleted content already embedded in its prompt. Must
	// run before DeleteComment because the FK ON DELETE SET NULL would
	// otherwise nullify trigger_comment_id and orphan those tasks in queued.
	if err := h.TaskService.CancelTasksByTriggerComment(r.Context(), comment.ID); err != nil {
		slog.Warn("cancel tasks for deleted trigger comment failed", append(logger.RequestAttrs(r), "error", err, "comment_id", commentId)...)
	}

	if err := h.Queries.DeleteComment(r.Context(), comment.ID); err != nil {
		slog.Warn("delete comment failed", append(logger.RequestAttrs(r), "error", err, "comment_id", commentId)...)
		writeError(w, http.StatusInternalServerError, "failed to delete comment")
		return
	}

	h.deleteS3Objects(r.Context(), attachmentURLs)
	slog.Info("comment deleted", append(logger.RequestAttrs(r), "comment_id", commentId, "issue_id", uuidToString(comment.IssueID))...)
	h.publish(protocol.EventCommentDeleted, workspaceID, actorType, actorID, map[string]any{
		"comment_id": uuidToString(comment.ID),
		"issue_id":   uuidToString(comment.IssueID),
	})
	w.WriteHeader(http.StatusNoContent)
}

// loadRootCommentForActor resolves a {commentId} URL param to a root comment in
// the caller's workspace. Returns the comment, the workspace UUID, the actor
// identity, and ok. Resolve / unresolve handlers share this scaffolding so the
// "must be a root comment" rule lives in one place.
func (h *Handler) loadRootCommentForActor(w http.ResponseWriter, r *http.Request) (db.Comment, string, string, string, bool) {
	commentId := chi.URLParam(r, "commentId")
	userID, ok := requireUserID(w, r)
	if !ok {
		return db.Comment{}, "", "", "", false
	}
	commentUUID, ok := parseUUIDOrBadRequest(w, commentId, "comment id")
	if !ok {
		return db.Comment{}, "", "", "", false
	}
	workspaceID := h.resolveWorkspaceID(r)
	wsUUID, ok := parseUUIDOrBadRequest(w, workspaceID, "workspace id")
	if !ok {
		return db.Comment{}, "", "", "", false
	}
	if _, ok := h.workspaceMember(w, r, workspaceID); !ok {
		return db.Comment{}, "", "", "", false
	}
	comment, err := h.Queries.GetCommentInWorkspace(r.Context(), db.GetCommentInWorkspaceParams{
		ID:          commentUUID,
		WorkspaceID: wsUUID,
	})
	if err != nil {
		writeError(w, http.StatusNotFound, "comment not found")
		return db.Comment{}, "", "", "", false
	}
	if comment.ParentID.Valid {
		writeError(w, http.StatusBadRequest, "only root comments can be resolved")
		return db.Comment{}, "", "", "", false
	}
	actorType, actorID := h.resolveActor(r, userID, workspaceID)
	return comment, workspaceID, actorType, actorID, true
}

func (h *Handler) ResolveComment(w http.ResponseWriter, r *http.Request) {
	comment, workspaceID, actorType, actorID, ok := h.loadRootCommentForActor(w, r)
	if !ok {
		return
	}
	wasResolved := comment.ResolvedAt.Valid

	actorUUID, err := util.ParseUUID(actorID)
	if err != nil {
		writeError(w, http.StatusBadRequest, "invalid actor id")
		return
	}
	updated, err := h.Queries.ResolveComment(r.Context(), db.ResolveCommentParams{
		ID:             comment.ID,
		ResolvedByType: pgtype.Text{String: actorType, Valid: true},
		ResolvedByID:   actorUUID,
	})
	if err != nil {
		slog.Warn("resolve comment failed", append(logger.RequestAttrs(r), "error", err, "comment_id", uuidToString(comment.ID))...)
		writeError(w, http.StatusInternalServerError, "failed to resolve comment")
		return
	}

	grouped := h.groupReactions(r, []pgtype.UUID{updated.ID})
	groupedAtt := h.groupAttachments(r, []pgtype.UUID{updated.ID})
	cid := uuidToString(updated.ID)
	resp := commentToResponse(updated, grouped[cid], groupedAtt[cid])

	// Suppress the event on a re-resolve no-op so consumers do not re-process
	// an unchanged thread (notifications, log spam).
	if !wasResolved {
		slog.Info("comment resolved", append(logger.RequestAttrs(r), "comment_id", cid)...)
		h.publish(protocol.EventCommentResolved, workspaceID, actorType, actorID, map[string]any{"comment": resp})
	}
	writeJSON(w, http.StatusOK, resp)
}

func (h *Handler) UnresolveComment(w http.ResponseWriter, r *http.Request) {
	comment, workspaceID, actorType, actorID, ok := h.loadRootCommentForActor(w, r)
	if !ok {
		return
	}
	wasResolved := comment.ResolvedAt.Valid

	updated, err := h.Queries.UnresolveComment(r.Context(), comment.ID)
	if err != nil {
		slog.Warn("unresolve comment failed", append(logger.RequestAttrs(r), "error", err, "comment_id", uuidToString(comment.ID))...)
		writeError(w, http.StatusInternalServerError, "failed to unresolve comment")
		return
	}

	grouped := h.groupReactions(r, []pgtype.UUID{updated.ID})
	groupedAtt := h.groupAttachments(r, []pgtype.UUID{updated.ID})
	cid := uuidToString(updated.ID)
	resp := commentToResponse(updated, grouped[cid], groupedAtt[cid])

	if wasResolved {
		slog.Info("comment unresolved", append(logger.RequestAttrs(r), "comment_id", cid)...)
		h.publish(protocol.EventCommentUnresolved, workspaceID, actorType, actorID, map[string]any{"comment": resp})
	}
	writeJSON(w, http.StatusOK, resp)
}