-- A message that slides up from the bottom edge, holds, then slides back down.
--
-- The card sits inside a scroll container of its own height whose content is twice that:
-- an empty strip above the card. Sliding is therefore ui.setScroll() on the tree already
-- laid out -- a delta on stored coordinates -- rather than a rebuild a frame, and the
-- container scissors the half of the card that has not arrived yet.
--
-- Whatever mounts the tree includes toast.node() and calls toast.draw(deltaMs); show()
-- rebuilds so the node exists, and hide() rebuilds to drop it.

local ui = require "ui"

local M = {}

local HEIGHT = 44
local MARGIN = 12
local SLIDE_MS = 180

local text, box
-- nil, or "in" / "hold" / "out" with the milliseconds spent in it.
local phase, elapsed, holdMs

---@param message string
---@param durationMs? integer How long the card holds before it slides away.
function M.show(message, durationMs)
  text, holdMs = message, durationMs or 1500
  phase, elapsed = "in", 0
  ui.rebuild()
end

function M.hide()
  if phase then
    phase, text, box = nil, nil, nil
    ui.rebuild()
  end
end

---@return NodeId|nil
function M.node()
  if not phase then
    return nil
  end
  box = ui.box {
    at = { x = MARGIN, y = screen.getHeight() - HEIGHT - MARGIN },
    w = screen.getWidth() - 2 * MARGIN,
    h = HEIGHT,
    scrollY = true,
    ui.box {
      w = "fill",
      ui.spacer { w = "fill", h = HEIGHT },
      ui.box {
        w = "fill",
        h = HEIGHT,
        align = "center",
        justify = "center",
        background = ui.theme.face,
        border = ui.theme.muted,
        ui.text(text),
      },
    },
  }
  return box
end

local function progress()
  if phase == "in" then
    return elapsed / SLIDE_MS
  elseif phase == "out" then
    return 1 - elapsed / SLIDE_MS
  end
  return 1
end

---Advances the slide. Safe to call every frame whether or not a toast is up.
---@param deltaMs integer
function M.draw(deltaMs)
  if not phase then
    return
  end
  elapsed = elapsed + deltaMs
  if phase == "in" and elapsed >= SLIDE_MS then
    phase, elapsed = "hold", 0
  elseif phase == "hold" and elapsed >= holdMs then
    phase, elapsed = "out", 0
  elseif phase == "out" and elapsed >= SLIDE_MS then
    M.hide()
    return
  end
  if box then
    ui.setScroll(box, 0, math.floor(HEIGHT * progress()))
  end
end

return M