ignore: refactoring and tests (#12460)

packages/app/src/components/titlebar-history.ts

@@ -0,0 +1,57 @@
+export const MAX_TITLEBAR_HISTORY = 100
+
+export type TitlebarAction = "back" | "forward" | undefined
+
+export type TitlebarHistory = {
+  stack: string[]
+  index: number
+  action: TitlebarAction
+}
+
+export function applyPath(state: TitlebarHistory, current: string, max = MAX_TITLEBAR_HISTORY): TitlebarHistory {
+  if (!state.stack.length) {
+    const stack = current === "/" ? ["/"] : ["/", current]
+    return { stack, index: stack.length - 1, action: undefined }
+  }
+
+  const active = state.stack[state.index]
+  if (current === active) {
+    if (!state.action) return state
+    return { ...state, action: undefined }
+  }
+
+  if (state.action) return { ...state, action: undefined }
+
+  return pushPath(state, current, max)
+}
+
+export function pushPath(state: TitlebarHistory, path: string, max = MAX_TITLEBAR_HISTORY): TitlebarHistory {
+  const stack = state.stack.slice(0, state.index + 1).concat(path)
+  const next = trimHistory(stack, stack.length - 1, max)
+  return { ...state, ...next, action: undefined }
+}
+
+export function trimHistory(stack: string[], index: number, max = MAX_TITLEBAR_HISTORY) {
+  if (stack.length <= max) return { stack, index }
+  const cut = stack.length - max
+  return {
+    stack: stack.slice(cut),
+    index: Math.max(0, index - cut),
+  }
+}
+
+export function backPath(state: TitlebarHistory) {
+  if (state.index <= 0) return
+  const index = state.index - 1
+  const to = state.stack[index]
+  if (!to) return
+  return { state: { ...state, index, action: "back" as const }, to }
+}
+
+export function forwardPath(state: TitlebarHistory) {
+  if (state.index >= state.stack.length - 1) return
+  const index = state.index + 1
+  const to = state.stack[index]
+  if (!to) return
+  return { state: { ...state, index, action: "forward" as const }, to }
+}