-- allium: 1
-- bDS Navigation Menu
-- Scope: core (read for rendering), extension Bucket F (menu editor UI)
-- File-only model: no DB table. Loaded from meta/menu.opml into a
-- transient value, mutated in memory, written back to OPML on save.

surface MenuManagementSurface {
    facing _: MenuOperator

    provides:
        MenuLoadRequested(project_id)
        UpdateMenuRequested(items)
        SyncMenuFromFilesystemRequested(project_id)
}

value MenuItem {
    kind: page | submenu | category_archive | home
    label: String
    slug: String?                   -- pageSlug for page/home, categoryName for category_archive
    children: List<MenuItem>?       -- present only for submenu kind
}

value Menu {
    items: List<MenuItem>

    -- Derived
    home_entry: items.first         -- always home after normalization
}

surface MenuSurface {
    context menu: Menu

    exposes:
        menu.items.count
        menu.home_entry.label
}

invariant HomeAlwaysFirst {
    -- Normalization guarantees home is always the first item.
    -- UpdateMenu strips any home entries from input, then prepends one.
    for menu in Menus:
        menu.items.first.kind = home
}

invariant MenuPersistedAsOpml {
    -- meta/menu.opml is the sole persistent store (no DB table).
    -- OPML outline attributes: text (label), type (kind),
    --   pageSlug (slug for page/home), categoryName (slug for category_archive).
    -- Nested <outline> elements represent submenu children.
    parse_opml(read_file("meta/menu.opml")) = menu.items
}

rule LoadMenu {
    when: MenuLoadRequested(project_id)
    -- Reads meta/menu.opml; if file missing, returns default (home-only) menu.
    -- Normalizes: strips home entries from body, prepends canonical home.
    ensures: MenuLoaded(project_id, normalize(parse_opml_or_empty(project_id)))
}

rule UpdateMenu {
    when: UpdateMenuRequested(items)
    -- Normalizes Home entry: strips all home items, prepends canonical home.
    -- Writes normalized menu back to meta/menu.opml.
    let without_home = items where kind != home
    ensures: MenuFileWritten(normalize(without_home))
}

rule SyncMenuFromFilesystem {
    when: SyncMenuFromFilesystemRequested(project_id)
    -- Reloads menu from OPML, normalizes, writes back (round-trip repair).
    ensures: MenuLoaded(project_id, _)
    ensures: MenuFileWritten(_)
}