import { atom, computed, type ReadableAtom } from 'nanostores'

import {
  arraysEqual,
  insertUniqueId,
  persistBoolean,
  persistStringArray,
  storedBoolean,
  storedStringArray
} from '@/lib/storage'

import { $paneStates, ensurePaneRegistered, setPaneOpen, setPaneWidthOverride, togglePane } from './panes'

export const SIDEBAR_DEFAULT_WIDTH = 237
export const SIDEBAR_MAX_WIDTH = 360
export const FILE_BROWSER_DEFAULT_WIDTH = '17rem'
export const FILE_BROWSER_MIN_WIDTH = '14rem'
export const FILE_BROWSER_MAX_WIDTH = '20rem'

export const SIDEBAR_SESSIONS_PAGE_SIZE = 50

const SIDEBAR_PINNED_STORAGE_KEY = 'hermes.desktop.pinnedSessions'
const SIDEBAR_AGENTS_GROUPED_STORAGE_KEY = 'hermes.desktop.agentsGroupedByWorkspace'
const PANES_FLIPPED_STORAGE_KEY = 'hermes.desktop.panesFlipped'

export const CHAT_SIDEBAR_PANE_ID = 'chat-sidebar'
export const FILE_BROWSER_PANE_ID = 'file-browser'
export const RIGHT_RAIL_PREVIEW_TAB_ID = 'preview'

export type RightRailTabId = typeof RIGHT_RAIL_PREVIEW_TAB_ID | `file:${string}`

ensurePaneRegistered(CHAT_SIDEBAR_PANE_ID, { open: true })
ensurePaneRegistered(FILE_BROWSER_PANE_ID, { open: false })

export const $sidebarOpen: ReadableAtom<boolean> = computed(
  $paneStates,
  states => states[CHAT_SIDEBAR_PANE_ID]?.open ?? true
)

export const $fileBrowserOpen: ReadableAtom<boolean> = computed(
  $paneStates,
  states => states[FILE_BROWSER_PANE_ID]?.open ?? false
)

export const $rightRailActiveTabId = atom<RightRailTabId>(RIGHT_RAIL_PREVIEW_TAB_ID)

export const $sidebarWidth: ReadableAtom<number> = computed($paneStates, states => {
  const override = states[CHAT_SIDEBAR_PANE_ID]?.widthOverride

  return typeof override === 'number' ? override : SIDEBAR_DEFAULT_WIDTH
})

export const $pinnedSessionIds = atom(storedStringArray(SIDEBAR_PINNED_STORAGE_KEY))
export const $sidebarPinsOpen = atom(true)
export const $sidebarRecentsOpen = atom(true)
export const $sidebarAgentsGrouped = atom(storedBoolean(SIDEBAR_AGENTS_GROUPED_STORAGE_KEY, false))
// When true, the sessions sidebar moves to the right and the file browser +
// preview rail move to the left — a mirror of the default layout.
export const $panesFlipped = atom(storedBoolean(PANES_FLIPPED_STORAGE_KEY, false))
export const $isSidebarResizing = atom(false)
export const $sessionsLimit = atom(SIDEBAR_SESSIONS_PAGE_SIZE)

$pinnedSessionIds.subscribe(ids => persistStringArray(SIDEBAR_PINNED_STORAGE_KEY, [...ids]))
$sidebarAgentsGrouped.subscribe(grouped => persistBoolean(SIDEBAR_AGENTS_GROUPED_STORAGE_KEY, grouped))
$panesFlipped.subscribe(flipped => persistBoolean(PANES_FLIPPED_STORAGE_KEY, flipped))

export function setSidebarWidth(width: number) {
  const bounded = Math.min(SIDEBAR_MAX_WIDTH, Math.max(SIDEBAR_DEFAULT_WIDTH, width))
  setPaneWidthOverride(CHAT_SIDEBAR_PANE_ID, bounded)
}

export function setSidebarOpen(open: boolean) {
  setPaneOpen(CHAT_SIDEBAR_PANE_ID, open)
}

export function toggleSidebarOpen() {
  togglePane(CHAT_SIDEBAR_PANE_ID)
}

export function toggleFileBrowserOpen() {
  togglePane(FILE_BROWSER_PANE_ID)
}

export function togglePanesFlipped() {
  $panesFlipped.set(!$panesFlipped.get())
}

export function selectRightRailTab(id: RightRailTabId) {
  $rightRailActiveTabId.set(id)
}

export function setSidebarPinsOpen(open: boolean) {
  $sidebarPinsOpen.set(open)
}

export function setSidebarRecentsOpen(open: boolean) {
  $sidebarRecentsOpen.set(open)
}

export function setSidebarAgentsGrouped(grouped: boolean) {
  $sidebarAgentsGrouped.set(grouped)
}

export function setSidebarResizing(resizing: boolean) {
  $isSidebarResizing.set(resizing)
}

export function pinSession(sessionId: string, index?: number) {
  const prev = $pinnedSessionIds.get()
  const next = insertUniqueId(prev, sessionId, index ?? prev.filter(id => id !== sessionId).length)

  if (!arraysEqual(prev, next)) {
    $pinnedSessionIds.set(next)
  }
}

export function unpinSession(sessionId: string) {
  const prev = $pinnedSessionIds.get()
  const next = prev.filter(id => id !== sessionId)

  if (!arraysEqual(prev, next)) {
    $pinnedSessionIds.set(next)
  }
}

export function reorderPinnedSession(sessionId: string, targetIndex: number) {
  const prev = $pinnedSessionIds.get()

  if (!prev.includes(sessionId)) {
    return
  }

  const next = insertUniqueId(prev, sessionId, targetIndex)

  if (!arraysEqual(prev, next)) {
    $pinnedSessionIds.set(next)
  }
}

export function bumpSessionsLimit(step: number = SIDEBAR_SESSIONS_PAGE_SIZE) {
  const safeStep = Math.max(1, Math.floor(step))
  $sessionsLimit.set($sessionsLimit.get() + safeStep)
}

export function resetSessionsLimit() {
  if ($sessionsLimit.get() !== SIDEBAR_SESSIONS_PAGE_SIZE) {
    $sessionsLimit.set(SIDEBAR_SESSIONS_PAGE_SIZE)
  }
}
