/**
 * User initd config on the personal drive: disabled units and optional drop-in ordering.
 * Paths are logical VFS paths under $HOME.
 */

import b4a from 'b4a'

/** One unit per line; blank lines and `#…` comments ignored. */
export const BARE_INITD_DISABLED_FILE = '~/.config/bare-os/initd/disabled.txt'

/**
 * Optional `name.unit` files under this directory. Supports `[Unit]` keys:
 * After=, Requires=, Wants=, TimeoutStartSec=, TimeoutStopSec=, Restart=, RestartSec=, ExecStartPost=, SocketActivationIpc=,
 * IdleSec= (with SocketActivationIpc: stop after idle seconds; requires unit `stop`),
 * ReadinessPath= (VFS path until exists), or `exec:<execLine>` (bounded by ReadinessTimeoutSec=),
 * ConditionPathExists= (skip unit start if path missing), AssertPathExists= (fail start if path missing),
 * ConditionPathIsDirectory= / AssertPathIsDirectory= (same semantics for directories),
 * ReadinessTimeoutSec=,
 * ExecHealthCmd=, HealthIntervalSec=, HealthFailureThreshold=, BareMaxExecDepth=,
 * Before= (reverse edge: listed units start after this one), OnFailure= (execLine after restart exhausted),
 * FailureAction=exec|none (default exec when OnFailure is set),
 * RestartMaxAttempts= (1–32; overrides default 3 for Restart=on-failure|always).
 */
export const BARE_INITD_UNITS_DIR = '~/.config/bare-os/units'

/** `systemctl --user` style overrides (merged on top of {@link BARE_INITD_UNITS_DIR}). */
export const BARE_INITD_SYSTEMCTL_USER_UNITS_DIR = '~/.config/bare-init/units'

/**
 * Optional fragments: `~/.config/bare-os/units.d/<unitName>/*.conf` (sorted), merged after the main `.unit` and before {@link BARE_INITD_SYSTEMCTL_USER_UNITS_DIR}.
 */
export const BARE_INITD_UNITS_D_BASE = '~/.config/bare-os/units.d'

/**
 * Timer drop-ins: `[Timer]` with OnCalendar= (five cron fields), EveryMs=, or OnInactiveSec=
 * (seconds between end of last run and next start), optional Persistent=false (run once), ExecLine=.
 */
export const BARE_INITD_TIMERS_DIR = '~/.config/bare-os/timers'

/** Built-in ordering when no drop-in file exists (kernel-logger before cron). */
export const BARE_INITD_DEFAULT_AFTER = Object.freeze({
  'bare-cron': ['kernel-logger']
})

/**
 * @typedef {{
 *   after: string[],
 *   requires: string[],
 *   wants: string[],
 *   timeoutStartSec: number | null,
 *   timeoutStopSec: number | null,
 *   restart: string | null,
 *   restartSec: number | null,
 *   execStartPost: string | null,
 *   socketActivationIpc: string | null,
 *   idleSec: number | null,
 *   readinessPath: string | null,
 *   readinessTimeoutSec: number | null,
 *   execHealthCmd: string | null,
 *   healthIntervalSec: number | null,
 *   healthFailureThreshold: number | null,
 *   bareMaxExecDepth: number | null,
 *   before: string[],
 *   onFailure: string | null,
 *   failureAction: 'exec' | 'none',
 *   restartMaxAttempts: number | null,
 *   conditionPathExists: string | null,
 *   assertPathExists: string | null,
 *   conditionPathIsDirectory: string | null,
 *   assertPathIsDirectory: string | null
 * }} BareInitdUnitDropIn
 */

/** @returns {BareInitdUnitDropIn} */
export function emptyUnitDropIn() {
  return {
    after: [],
    requires: [],
    wants: [],
    timeoutStartSec: null,
    timeoutStopSec: null,
    restart: null,
    restartSec: null,
    execStartPost: null,
    socketActivationIpc: null,
    idleSec: null,
    readinessPath: null,
    readinessTimeoutSec: null,
    execHealthCmd: null,
    healthIntervalSec: null,
    healthFailureThreshold: null,
    bareMaxExecDepth: null,
    before: [],
    onFailure: null,
    failureAction: 'exec',
    restartMaxAttempts: null,
    conditionPathExists: null,
    assertPathExists: null,
    conditionPathIsDirectory: null,
    assertPathIsDirectory: null
  }
}

/**
 * @param {string} val
 * @returns {string[]}
 */
function parseList(val) {
  return val
    .split(/[\s,]+/)
    .map((s) => s.trim())
    .filter(Boolean)
}

/**
 * Parse a systemd-inspired `.unit` snippet (only `[Unit]` keys are honored).
 * @param {string} text
 * @returns {BareInitdUnitDropIn}
 */
export function parseUnitDropInText(text) {
  const out = emptyUnitDropIn()
  let section = ''
  for (const raw of text.split(/\r?\n/)) {
    const line = raw.trim()
    if (!line || line.startsWith('#')) continue
    if (/^\[[^\]]+\]$/.test(line)) {
      section = line.slice(1, -1).toLowerCase()
      continue
    }
    if (section !== 'unit') continue
    const eq = line.indexOf('=')
    if (eq < 1) continue
    const key = line.slice(0, eq).trim().toLowerCase()
    const val = line.slice(eq + 1).trim()
    if (key === 'after') out.after.push(...parseList(val))
    else if (key === 'requires') out.requires.push(...parseList(val))
    else if (key === 'wants') out.wants.push(...parseList(val))
    else if (key === 'timeoutstartsec') {
      const n = Number.parseInt(val, 10)
      if (Number.isFinite(n) && n > 0) out.timeoutStartSec = n
    } else if (key === 'timeoutstopsec') {
      const n = Number.parseInt(val, 10)
      if (Number.isFinite(n) && n > 0) out.timeoutStopSec = n
    } else if (key === 'restart') {
      out.restart = val.toLowerCase()
    } else if (key === 'restartsec') {
      const n = Number.parseInt(val, 10)
      if (Number.isFinite(n) && n >= 0) out.restartSec = n
    } else if (key === 'execstartpost') {
      out.execStartPost = val
    } else if (key === 'socketactivationipc') {
      if (/^[a-zA-Z0-9._-]+$/.test(val)) out.socketActivationIpc = val
    } else if (key === 'idlesec') {
      const n = Number.parseInt(val, 10)
      if (Number.isFinite(n) && n > 0 && n <= 86400) out.idleSec = n
    } else if (key === 'readinesspath') {
      if (val.trim()) out.readinessPath = val.trim()
    } else if (key === 'readinesstimeoutsec') {
      const n = Number.parseInt(val, 10)
      if (Number.isFinite(n) && n > 0) out.readinessTimeoutSec = n
    } else if (key === 'exechealthcmd') {
      if (val.trim()) out.execHealthCmd = val.trim()
    } else if (key === 'healthintervalsec') {
      const n = Number.parseInt(val, 10)
      if (Number.isFinite(n) && n > 0) out.healthIntervalSec = n
    } else if (key === 'healthfailurethreshold') {
      const n = Number.parseInt(val, 10)
      if (Number.isFinite(n) && n > 0) out.healthFailureThreshold = n
    } else if (key === 'baremaxexecdepth') {
      const n = Number.parseInt(val, 10)
      if (Number.isFinite(n) && n > 0) out.bareMaxExecDepth = n
    } else if (key === 'before') {
      out.before.push(...parseList(val))
    } else if (key === 'onfailure') {
      if (val.trim()) out.onFailure = val
    } else if (key === 'failureaction') {
      const v = val.toLowerCase()
      if (v === 'none') out.failureAction = 'none'
      else out.failureAction = 'exec'
    } else if (key === 'restartmaxattempts') {
      const n = Number.parseInt(val, 10)
      if (Number.isFinite(n) && n >= 1 && n <= 32) out.restartMaxAttempts = n
    } else if (key === 'conditionpathexists') {
      const t = val.trim()
      if (t.length > 0 && t.length <= 512) out.conditionPathExists = t
    } else if (key === 'assertpathexists') {
      const t = val.trim()
      if (t.length > 0 && t.length <= 512) out.assertPathExists = t
    } else if (key === 'conditionpathisdirectory') {
      const t = val.trim()
      if (t.length > 0 && t.length <= 512) out.conditionPathIsDirectory = t
    } else if (key === 'assertpathisdirectory') {
      const t = val.trim()
      if (t.length > 0 && t.length <= 512) out.assertPathIsDirectory = t
    }
  }
  out.after = [...new Set(out.after)]
  out.requires = [...new Set(out.requires)]
  out.wants = [...new Set(out.wants)]
  out.before = [...new Set(out.before)]
  return out
}

/**
 * @param {BareInitdUnitDropIn} base
 * @param {BareInitdUnitDropIn} user
 * @returns {BareInitdUnitDropIn}
 */
export function mergeUnitDropIns(base, user) {
  const pickArr = (u, b) =>
    u.length ? [...new Set(u)] : [...new Set(b)]
  return {
    after: pickArr(user.after, base.after),
    requires: pickArr(user.requires, base.requires),
    wants: pickArr(user.wants, base.wants),
    timeoutStartSec: user.timeoutStartSec ?? base.timeoutStartSec,
    timeoutStopSec: user.timeoutStopSec ?? base.timeoutStopSec,
    restart: user.restart ?? base.restart,
    restartSec: user.restartSec ?? base.restartSec,
    execStartPost: user.execStartPost ?? base.execStartPost,
    socketActivationIpc: user.socketActivationIpc ?? base.socketActivationIpc,
    idleSec: user.idleSec ?? base.idleSec,
    readinessPath: user.readinessPath ?? base.readinessPath,
    readinessTimeoutSec:
      user.readinessTimeoutSec ?? base.readinessTimeoutSec,
    execHealthCmd: user.execHealthCmd ?? base.execHealthCmd,
    healthIntervalSec: user.healthIntervalSec ?? base.healthIntervalSec,
    healthFailureThreshold:
      user.healthFailureThreshold ?? base.healthFailureThreshold,
    bareMaxExecDepth: user.bareMaxExecDepth ?? base.bareMaxExecDepth,
    before: pickArr(user.before, base.before),
    onFailure: user.onFailure ?? base.onFailure,
    failureAction: user.failureAction ?? base.failureAction,
    restartMaxAttempts: user.restartMaxAttempts ?? base.restartMaxAttempts,
    conditionPathExists:
      user.conditionPathExists ?? base.conditionPathExists,
    assertPathExists: user.assertPathExists ?? base.assertPathExists,
    conditionPathIsDirectory:
      user.conditionPathIsDirectory ?? base.conditionPathIsDirectory,
    assertPathIsDirectory:
      user.assertPathIsDirectory ?? base.assertPathIsDirectory
  }
}

/**
 * @param {{ readFile: (p: string) => Promise<Uint8Array | null> }} vfs
 * @param {string} logicalPath
 * @returns {Promise<BareInitdUnitDropIn>}
 */
export async function readUnitDropInFromPath(vfs, logicalPath) {
  try {
    const buf = await vfs.readFile(logicalPath)
    if (!buf) return emptyUnitDropIn()
    return parseUnitDropInText(b4a.toString(buf, 'utf8'))
  } catch {
    return emptyUnitDropIn()
  }
}

/**
 * @param {{ readFile: (p: string) => Promise<Uint8Array | null> }} vfs
 * @returns {Promise<Set<string>>}
 */
export async function readInitdDisabledSet(vfs) {
  const out = new Set()
  try {
    const buf = await vfs.readFile(BARE_INITD_DISABLED_FILE)
    if (!buf) return out
    const text = b4a.toString(buf, 'utf8')
    for (const line of text.split(/\r?\n/)) {
      const t = line.trim()
      if (!t || t.startsWith('#')) continue
      out.add(t)
    }
  } catch {
    /* missing file */
  }
  return out
}

/**
 * @param {{
 *   mkdir: (p: string, opts?: { recursive?: boolean }) => Promise<unknown>,
 *   writeFile: (p: string, buf: Uint8Array) => Promise<unknown>,
 *   unlink: (p: string) => Promise<unknown>
 * }} vfs
 * @param {Set<string>} disabled
 */
export async function writeInitdDisabledSet(vfs, disabled) {
  await vfs.mkdir('~/.config/bare-os/initd', { recursive: true })
  if (disabled.size === 0) {
    try {
      await vfs.unlink(BARE_INITD_DISABLED_FILE)
    } catch {
      /* absent */
    }
    return
  }
  const body = [...disabled].sort().join('\n') + '\n'
  await vfs.writeFile(BARE_INITD_DISABLED_FILE, b4a.from(body, 'utf8'))
}

/**
 * @param {{ readFile: (p: string) => Promise<Uint8Array | null>, readdir?: (p: string) => Promise<string[]> }} vfs
 * @param {string} unitName
 * @returns {Promise<BareInitdUnitDropIn>}
 */
export async function readUnitDropIn(vfs, unitName) {
  if (!/^[a-zA-Z0-9._-]+$/.test(unitName)) return emptyUnitDropIn()
  let merged = await readUnitDropInFromPath(
    vfs,
    `${BARE_INITD_UNITS_DIR}/${unitName}.unit`
  )
  const fragDir = `${BARE_INITD_UNITS_D_BASE}/${unitName}`
  if (typeof vfs.readdir === 'function') {
    try {
      const names = await vfs.readdir(fragDir)
      const confs = names
        .filter((n) => typeof n === 'string' && n.endsWith('.conf'))
        .sort()
      for (const n of confs) {
        const frag = await readUnitDropInFromPath(vfs, `${fragDir}/${n}`)
        merged = mergeUnitDropIns(merged, frag)
      }
    } catch {
      /* missing dir */
    }
  }
  const usr = await readUnitDropInFromPath(
    vfs,
    `${BARE_INITD_SYSTEMCTL_USER_UNITS_DIR}/${unitName}.unit`
  )
  return mergeUnitDropIns(merged, usr)
}

/**
 * @param {{ readFile: (p: string) => Promise<Uint8Array | null> }} vfs
 * @param {string} unitName
 * @returns {Promise<string[]>}
 */
export async function readUnitAfterFromDropIn(vfs, unitName) {
  const d = await readUnitDropIn(vfs, unitName)
  return d.after
}

/**
 * @param {{ readFile: (p: string) => Promise<Uint8Array | null> }} vfs
 * @param {{ name: string }[]} services
 * @param {Readonly<Record<string, string[]>>} defaultAfter
 * @returns {Promise<Map<string, BareInitdUnitDropIn>>}
 */
export async function loadInitdUnitDropIns(vfs, services, defaultAfter) {
  /** @type {Map<string, BareInitdUnitDropIn>} */
  const map = new Map()
  for (const s of services) {
    const fromFile = await readUnitDropIn(vfs, s.name)
    const def = defaultAfter[s.name] || []
    fromFile.after = [...new Set([...def, ...fromFile.after])]
    map.set(s.name, fromFile)
  }
  for (const [name, di] of map) {
    for (const b of di.before) {
      if (!/^[a-zA-Z0-9._-]+$/.test(b)) continue
      const target = map.get(b)
      if (target) {
        target.after = [...new Set([...target.after, name])]
      }
    }
  }
  return map
}

/**
 * @param {{ readFile: (p: string) => Promise<Uint8Array | null> }} vfs
 * @param {{ name: string }[]} services
 * @param {Readonly<Record<string, string[]>>} defaultAfter
 * @returns {Promise<Map<string, string[]>>}
 */
export async function loadInitdAfterMap(vfs, services, defaultAfter) {
  const full = await loadInitdUnitDropIns(vfs, services, defaultAfter)
  const map = new Map()
  for (const [k, v] of full) map.set(k, v.after)
  return map
}

/**
 * @template T extends { name: string }
 * @param {T[]} services
 * @param {Set<string>} disabled
 * @param {Map<string, string[]>} requiresMap
 */
function filterSatisfiedRequires(services, disabled, requiresMap) {
  const names = new Set(services.map((s) => s.name))
  return services.filter((s) => {
    for (const r of requiresMap.get(s.name) || []) {
      if (!names.has(r)) return false
      if (disabled.has(r)) return false
    }
    return true
  })
}

/**
 * Topological sort; cycles fall back to registration order for the remainder.
 * @template T extends { name: string }
 * @param {T[]} services
 * @param {Set<string>} disabled
 * @param {Map<string, string[]>} afterMap
 * @param {Map<string, string[]>} [requiresMap]
 * @param {Map<string, string[]>} [wantsMap]
 * @returns {T[]}
 */
export function sortServicesForBoot(
  services,
  disabled,
  afterMap,
  requiresMap,
  wantsMap
) {
  const reqM = requiresMap || new Map()
  const wanM = wantsMap || new Map()
  let active = services.filter((s) => !disabled.has(s.name))
  active = filterSatisfiedRequires(active, disabled, reqM)
  const nameSet = new Set(active.map((s) => s.name))
  /** @type {Map<string, Set<string>>} */
  const prereq = new Map()
  for (const s of active) {
    const inc = new Set()
    for (const a of afterMap.get(s.name) || []) {
      if (nameSet.has(a)) inc.add(a)
    }
    for (const r of reqM.get(s.name) || []) {
      if (nameSet.has(r)) inc.add(r)
    }
    for (const w of wanM.get(s.name) || []) {
      if (nameSet.has(w)) inc.add(w)
    }
    prereq.set(s.name, inc)
  }
  const remaining = new Set(active.map((s) => s.name))
  /** @type {T[]} */
  const ordered = []
  while (remaining.size) {
    const ready = [...remaining].filter((n) => {
      for (const p of prereq.get(n) || []) {
        if (remaining.has(p)) return false
      }
      return true
    })
    if (!ready.length) {
      const regOrder = active.map((s) => s.name).filter((n) => remaining.has(n))
      for (const n of regOrder) {
        const svc = active.find((s) => s.name === n)
        if (svc) ordered.push(svc)
        remaining.delete(n)
      }
      break
    }
    ready.sort()
    for (const n of ready) {
      const svc = active.find((s) => s.name === n)
      if (svc) ordered.push(svc)
      remaining.delete(n)
    }
  }
  return ordered
}

/**
 * @typedef {{
 *   kind: 'calendar',
 *   onCalendar: string,
 *   execLine: string,
 *   jitterSec: number
 * } | {
 *   kind: 'everyMs',
 *   everyMs: number,
 *   execLine: string,
 *   jitterSec: number
 * } | {
 *   kind: 'onInactiveSec',
 *   inactiveSec: number,
 *   execLine: string,
 *   jitterSec: number,
 *   persistent: boolean
 * }} BareOsTimerDropIn
 */

/**
 * Parse `~/.config/bare-os/timers/*.timer` — `[Timer]` with OnCalendar=, EveryMs=, or OnInactiveSec= and ExecLine=.
 * @param {string} text
 * @returns {BareOsTimerDropIn | null}
 */
export function parseBareOsTimerFile(text) {
  let onCalendar = ''
  /** @type {number | null} */
  let everyMs = null
  /** @type {number | null} */
  let inactiveSec = null
  let persistent = true
  /** @type {number | null} */
  let jitterSec = null
  let execLine = ''
  let section = ''
  for (const raw of text.split(/\r?\n/)) {
    const line = raw.trim()
    if (!line || line.startsWith('#')) continue
    if (/^\[[^\]]+\]$/.test(line)) {
      section = line.slice(1, -1).toLowerCase()
      continue
    }
    if (section !== 'timer') continue
    const eq = line.indexOf('=')
    if (eq < 1) continue
    const key = line.slice(0, eq).trim().toLowerCase()
    const val = line.slice(eq + 1).trim()
    if (key === 'oncalendar') onCalendar = val
    else if (key === 'everyms') {
      const n = Number.parseInt(val, 10)
      if (Number.isFinite(n) && n >= 1000 && n <= 86400000) everyMs = n
    } else if (key === 'oninactivesec') {
      const n = Number.parseInt(val, 10)
      if (Number.isFinite(n) && n >= 1 && n <= 86400) inactiveSec = n
    } else if (key === 'persistent') {
      const v = val.toLowerCase()
      persistent = !(
        v === '0' ||
        v === 'false' ||
        v === 'no' ||
        v === 'off'
      )
    } else if (key === 'jittersec') {
      const n = Number.parseInt(val, 10)
      if (Number.isFinite(n) && n >= 0 && n <= 86400) jitterSec = n
    } else if (key === 'execline') execLine = val
  }
  const el = execLine.trim()
  if (!el) return null
  const j = jitterSec != null ? jitterSec : 0
  if (everyMs != null)
    return { kind: 'everyMs', everyMs, execLine: el, jitterSec: j }
  if (inactiveSec != null)
    return {
      kind: 'onInactiveSec',
      inactiveSec,
      execLine: el,
      jitterSec: j,
      persistent
    }
  if (!onCalendar.trim()) return null
  return {
    kind: 'calendar',
    onCalendar: onCalendar.trim(),
    execLine: el,
    jitterSec: j
  }
}