server <- function(input, output, session, db) {

  nav <- reactiveValues(
    screen    = "apiaries",
    apiary_id = NULL,
    colony_id = NULL
  )

  # ---- Module initialization ------------------------------------------------
  screen_apiaries_server("s_apiaries",   db = db, nav = nav)
  screen_colonies_server("s_colonies",   db = db, nav = nav)
  screen_colony_server("s_colony",       db = db, nav = nav)
  screen_inspection_server("s_insp",     db = db, nav = nav)
  screen_varroa_server("s_varroa",       db = db, nav = nav)
  screen_harvest_server("s_harvest",     db = db, nav = nav)
  screen_queen_server("s_queen",         db = db, nav = nav)
  screen_checklists_server("s_chklst",   db = db, nav = nav)
  screen_actions_server("s_actions",     db = db, nav = nav)
  screen_lineage_server("s_lineage",     db = db, nav = nav)
  screen_quick_insp_server("s_qinsp",   db = db, nav = nav)
  screen_bulk_action_server("s_bulk",   db = db, nav = nav)

  # ---- Navigation header ---------------------------------------------------
  BACK <- c(
    colonies         = "apiaries",
    colony           = "colonies",
    inspection       = "colony",
    varroa           = "colony",
    harvest          = "colony",
    queens           = "colony",
    checklists       = "colony",
    actions          = "colony",
    lineage          = "colonies",
    quick_inspection = "colonies",
    bulk_action      = "colonies"
  )

  output$nav_header <- renderUI({
    screen <- nav$screen
    if (screen == "apiaries") {
      return(shiny::div(
        class = "bk-header d-flex justify-content-between align-items-center",
        shiny::tags$h4("Beekeeper"),
        shiny::actionButton("btn_settings", shiny::icon("gear"),
          class = "btn btn-link bk-header-icon", title = "Einstellungen")
      ))
    }
    title <- switch(screen,
      colonies = {
        ap <- db_apiaries_get(db, nav$apiary_id)
        if (nrow(ap) > 0) ap$name[1] else "Stand"
      },
      colony = {
        co <- db_colonies_get(db, nav$colony_id)
        if (nrow(co) > 0) co$name[1] else "Volk"
      },
      inspection       = "Neue Durchsicht",
      quick_inspection = "Schnelldurchsicht",
      bulk_action      = "Sammelmaßnahme",
      varroa     = "Varroa",
      harvest    = "Honigernte",
      queens     = "Königin",
      checklists = "Checkliste",
      actions    = "Maßnahmen",
      lineage    = "Stammbaum",
      ""
    )
    shiny::div(
      class = "bk-header d-flex align-items-center gap-2",
      shiny::actionButton("nav_back", shiny::icon("arrow-left"),
        class = "btn btn-link bk-header-icon"
      ),
      shiny::tags$h5(class = "mb-0 flex-grow-1", title)
    )
  })

  observeEvent(input$nav_back, {
    target <- BACK[nav$screen]
    if (!is.na(target)) nav$screen <- target
  })

  observeEvent(input$keepalive_ping, {}, ignoreNULL = TRUE, ignoreInit = TRUE)

  # ---- Content switcher ----------------------------------------------------
  output$screen_content <- renderUI({
    switch(nav$screen,
      apiaries   = screen_apiaries_ui("s_apiaries"),
      colonies   = screen_colonies_ui("s_colonies"),
      colony     = screen_colony_ui("s_colony"),
      inspection = screen_inspection_ui("s_insp"),
      varroa     = screen_varroa_ui("s_varroa"),
      harvest    = screen_harvest_ui("s_harvest"),
      queens     = screen_queen_ui("s_queen"),
      checklists = screen_checklists_ui("s_chklst"),
      actions    = screen_actions_ui("s_actions"),
      lineage          = screen_lineage_ui("s_lineage"),
      quick_inspection = screen_quick_insp_ui("s_qinsp"),
      bulk_action      = screen_bulk_action_ui("s_bulk")
    )
  })
}