/**
 * Desktop UI preferences — PearDock-style cache + FOUC localStorage mirror.
 *
 * Primary: ~/.config/peardata/cache/settings.json
 * Mirror:  localStorage peardata.settings.v1
 */
import fs from 'fs'
import path from 'path'
import { getPeardataCacheDir, getPeardataHome } from './paths.js'
import { atomicWriteJson } from './jsonCache.js'

export const SETTINGS_CACHE_VERSION = 1
export const SETTINGS_LOCALSTORAGE_KEY = 'peardata.settings.v1'

/** @typedef {{
 *   theme: 'dark'|'light',
 *   accent: string,
 *   density: 'comfortable'|'compact'|'spacious',
 *   sidebarCollapsed: boolean,
 *   notifyDesktop: boolean,
 *   comparePeers: boolean,
 *   chartPoints: number,
 *   defaultExplore: string,
 *   reduceMotion: boolean,
 *   metricsCardHeight: number,
 *   metricsDimSort: 'name'|'value',
 *   metricsCollapsed: string[],
 *   metricsChartTypes: Record<string, string>,
 *   metricsPinned: string[],
 *   metricsGroup: 'average'|'min'|'max'|'sum',
 *   metricsForcePlay: boolean,
 *   metricsFiltersOpen: boolean,
 *   reconnectMaxAttempts: number,
 *   autoRestorePeers: boolean,
 *   qvacOnboarded?: boolean,
 *   qvacProfile?: string,
 *   qvacMode?: string,
 *   qvacCacheDir?: string,
 *   qvacRag?: boolean,
 *   qvacIdleUnloadMin?: number,
 *   qvacSubAgents?: boolean,
 *   qvacMaxSubAgents?: number,
 *   qvacToolDepth?: 'auto'|'core'|'deep',
 *   qvacAutoNavigate?: 'off'|'ask'|'on',
 *   customDashboards?: Array<{
 *     id: string,
 *     name: string,
 *     description?: string,
 *     tiles: Array<{ id: string, chart: string, mode?: string, title?: string }>,
 *     createdAt?: number,
 *     updatedAt?: number,
 *   }>,
 *   activeDashboardId?: string|null,
 * }} UiSettings */

/** @returns {UiSettings} */
export function defaultSettings() {
  return {
    theme: 'dark',
    accent: 'teal',
    density: 'comfortable',
    sidebarCollapsed: false,
    notifyDesktop: true,
    comparePeers: false,
    chartPoints: 90,
    defaultExplore: 'system.io',
    reduceMotion: false,
    metricsCardHeight: 160,
    metricsDimSort: 'name',
    metricsCollapsed: [],
    metricsChartTypes: {},
    metricsPinned: [],
    metricsGroup: 'average',
    metricsForcePlay: false,
    metricsFiltersOpen: false,
    reconnectMaxAttempts: 20,
    autoRestorePeers: true,
    qvacOnboarded: false,
    qvacProfile: 'recommended',
    qvacMode: '',
    qvacCacheDir: '',
    qvacRag: true,
    qvacIdleUnloadMin: 30,
    qvacSubAgents: true,
    qvacMaxSubAgents: 3,
    qvacToolDepth: 'auto',
    /** off = never switch tabs; ask = confirm each time; on = always when tools request */
    qvacAutoNavigate: 'ask',
    customDashboards: [],
    activeDashboardId: null,
  }
}

export function getSettingsCachePath() {
  return path.join(getPeardataCacheDir(), 'settings.json')
}

/** @deprecated use getSettingsCachePath */
export function settingsPath() {
  return getSettingsCachePath()
}

function readSettingsFile(file) {
  try {
    if (!fs.existsSync(file)) return null
    const raw = JSON.parse(fs.readFileSync(file, 'utf8'))
    return raw?.settings || raw || null
  } catch {
    return null
  }
}

function migrateLegacySettings() {
  const candidates = [
    path.join(getPeardataHome(), 'ui-settings.json'),
    path.join(getPeardataHome(), 'cache', 'ui-settings.json'),
  ]
  for (const file of candidates) {
    const s = readSettingsFile(file)
    if (s && typeof s === 'object') return s
  }
  try {
    if (typeof localStorage !== 'undefined') {
      const boot = localStorage.getItem('peardata-ui-boot')
      if (boot) {
        const parsed = JSON.parse(boot)
        if (parsed?.theme) return { theme: parsed.theme }
      }
    }
  } catch {
    // ignore
  }
  return null
}

function readLocalStorageMirror() {
  try {
    if (typeof localStorage === 'undefined') return null
    const mir = localStorage.getItem(SETTINGS_LOCALSTORAGE_KEY)
    if (!mir) return null
    const parsed = JSON.parse(mir)
    return parsed && typeof parsed === 'object' ? parsed : null
  } catch {
    return null
  }
}

/** Side-effect free merge of defaults + disk/legacy/LS. Never writes. */
function peekSettings() {
  const defaults = defaultSettings()
  const fromFile =
    readSettingsFile(getSettingsCachePath()) ||
    migrateLegacySettings() ||
    readLocalStorageMirror()
  return { ...defaults, ...(fromFile || {}) }
}

/**
 * Persist settings envelope to disk + LS mirror. Does not call loadSettings.
 * @param {UiSettings} settings
 */
function persistSettings(settings) {
  const payload = {
    version: SETTINGS_CACHE_VERSION,
    updatedAt: new Date().toISOString(),
    settings,
  }
  try {
    atomicWriteJson(getSettingsCachePath(), payload)
  } catch {
    // ignore persistence failures
  }
  try {
    if (typeof localStorage !== 'undefined') {
      localStorage.setItem(SETTINGS_LOCALSTORAGE_KEY, JSON.stringify(settings))
      localStorage.setItem(
        'peardata-ui-boot',
        JSON.stringify({ theme: settings.theme })
      )
    }
  } catch {
    // ignore
  }
}

export function loadSettings() {
  const defaults = defaultSettings()
  const cached = readSettingsFile(getSettingsCachePath())
  if (cached && typeof cached === 'object') {
    return { ...defaults, ...cached }
  }

  const legacy = migrateLegacySettings()
  if (legacy) {
    const merged = { ...defaults, ...legacy }
    persistSettings(merged)
    return merged
  }

  const mir = readLocalStorageMirror()
  return { ...defaults, ...(mir || {}) }
}

/** @param {Partial<UiSettings>} patch */
export function saveSettings(patch) {
  const next = { ...peekSettings(), ...patch }
  persistSettings(next)
  return next
}

/**
 * @param {UiSettings} s
 */
export function applySettingsToDom(s) {
  const html = document.documentElement
  const body = document.body
  html.dataset.theme = s.theme
  body.dataset.theme = s.theme
  body.dataset.accent = s.accent || 'teal'
  body.dataset.density = s.density || 'comfortable'
  body.dataset.reduceMotion = s.reduceMotion ? '1' : '0'
  body.classList.toggle('sidebar-collapsed', Boolean(s.sidebarCollapsed))
}