import SwiftUI

/// The read screen's comment thread — the phone's rendering of `CommentThread`, oldest first,
/// below the card's own content.
///
/// **The wording is the Mac's** (`CommentsHeader` / `CommentAuthorLine` in `CardCommentsLayout` —
/// pure, but homed in `Kanban/UI`, which the phone deliberately does not compile, so the two lines
/// are restated rather than imported): the header is "Comments · N" with the zero rendered as a
/// count rather than an absence, and the author line is "author · timestamp · edited" with each
/// absent segment dropped and the whole line dropped when there is neither a name nor a date to
/// hang "edited" from. Absent means absent — no "Unattributed" placeholder, no avatar: the file
/// deliberately carries no identity system, and the render must not invent one.
///
/// Read-only rows plus two doors: **Add Comment** under the thread opens the composer, and each
/// row's context menu carries **Edit** — both sheets, both transactional, both the containing
/// screen's to present. A posted comment's attachments render as read-only paperclip rows, the
/// Mac's own rule for chips outside an authoring surface.
struct CardCommentsSection: View {
    /// `nil` while the first read is in flight — the header and the Add button render, rows wait.
    let thread: CommentThread?
    let onAdd: () -> Void
    let onEdit: (Comment) -> Void

    var body: some View {
        VStack(alignment: .leading, spacing: 16) {
            Divider()

            Text("Comments · \(thread?.comments.count ?? 0)")
                .font(.subheadline.smallCaps().weight(.semibold))
                .foregroundStyle(.secondary)

            if let thread {
                ForEach(thread.comments) { comment in
                    CommentRow(comment: comment)
                        .contextMenu {
                            Button {
                                onEdit(comment)
                            } label: {
                                Label("Edit Comment", systemImage: "pencil")
                            }
                        }
                }
            }

            Button(action: onAdd) {
                Label("Add Comment", systemImage: "plus.bubble")
            }
        }
    }
}

/// One posted comment: author line, body through the same block renderer the card's own body
/// uses (a comment's Markdown is the card-body subset, so the renderer is shared by construction),
/// and the attachment listing.
private struct CommentRow: View {
    let comment: Comment

    var body: some View {
        VStack(alignment: .leading, spacing: 8) {
            if let line = authorLine {
                Text(line)
                    .font(.footnote)
                    .foregroundStyle(.secondary)
            }

            // Only a non-empty body reaches the renderer: `CardBodyView`'s empty case says
            // "No description", which is a card's word, not a comment's — an attachment-only
            // comment renders its chips alone.
            if !comment.body.isEmpty {
                CardBodyView(body: comment.body)
            }

            ForEach(comment.attachments, id: \.self) { name in
                Label(name, systemImage: "paperclip")
                    .font(.footnote)
                    .foregroundStyle(.secondary)
                    .lineLimit(1)
            }
        }
        .padding(12)
        .frame(maxWidth: .infinity, alignment: .leading)
        .background(Color(.secondarySystemBackground), in: RoundedRectangle(cornerRadius: 12))
    }

    /// `CommentAuthorLine.text(author:timestamp:isEdited:)`, restated. An empty `author` string is
    /// treated as absent for the Mac's reason: the Writer never writes `author: ""` (it omits the
    /// key), so one on disk is a hand edit, and a blank name beside a separator would be noise.
    private var authorLine: String? {
        var parts: [String] = []
        if let author = comment.author.value?.trimmingCharacters(in: .whitespacesAndNewlines),
           !author.isEmpty {
            parts.append(author)
        }
        if let created = comment.created.value {
            parts.append(created.formatted(date: .abbreviated, time: .shortened))
        }
        guard !parts.isEmpty else { return nil }
        if comment.isEdited {
            parts.append("edited")
        }
        return parts.joined(separator: " · ")
    }
}