/**
 * User crontab at ~/.crontab — five fields (minute hour dom month dow) + command.
 * Registered as bare-initd service `bare-cron`.
 */

import { registerBareInitdDisposer, registerBareService } from './bare-initd.js'

/** @param {Date} d */
function msToNextMinuteBoundary(d = new Date()) {
  return 60000 - (d.getSeconds() * 1000 + d.getMilliseconds())
}

/**
 * @param {string} spec
 * @param {number} value
 * @param {number} min
 * @param {number} max
 */
export function fieldMatches(spec, value, min, max) {
  const s = spec.trim()
  if (!s) return false
  for (const part of s.split(',')) {
    const p = part.trim()
    if (!p) continue
    if (partMatches(p, value, min, max)) return true
  }
  return false
}

/**
 * @param {string} p
 * @param {number} value
 * @param {number} min
 * @param {number} max
 */
function partMatches(p, value, min, max) {
  if (p === '*') return true
  const slash = p.indexOf('/')
  if (slash !== -1) {
    const range = p.slice(0, slash)
    const step = Number.parseInt(p.slice(slash + 1), 10)
    if (!Number.isFinite(step) || step < 1) return false
    let lo
    let hi
    if (range === '*') {
      lo = min
      hi = max
    } else if (range.includes('-')) {
      const [a, b] = range.split('-').map((x) => Number.parseInt(x.trim(), 10))
      lo = Math.min(a, b)
      hi = Math.max(a, b)
    } else {
      lo = hi = Number.parseInt(range, 10)
    }
    if (!Number.isFinite(lo) || !Number.isFinite(hi)) return false
    return value >= lo && value <= hi && (value - lo) % step === 0
  }
  if (p.includes('-')) {
    const [a, b] = p.split('-').map((x) => Number.parseInt(x.trim(), 10))
    const lo = Math.min(a, b)
    const hi = Math.max(a, b)
    return value >= lo && value <= hi
  }
  const n = Number.parseInt(p, 10)
  return Number.isFinite(n) && value === n
}

/**
 * @param {string} spec
 * @param {number} jsDow 0=Sun … 6=Sat (Date#getDay)
 */
export function dowFieldMatches(spec, jsDow) {
  const s = spec.trim()
  if (!s) return false
  for (const part of s.split(',')) {
    const p = part.trim()
    if (!p) continue
    if (dowPartMatches(p, jsDow)) return true
  }
  return false
}

/**
 * @param {string} p
 * @param {number} jsDow
 */
function dowPartMatches(p, jsDow) {
  if (p === '*') return true
  const slash = p.indexOf('/')
  if (slash !== -1) {
    const range = p.slice(0, slash)
    const step = Number.parseInt(p.slice(slash + 1), 10)
    if (!Number.isFinite(step) || step < 1) return false
    if (range === '*') {
      for (let js = 0; js <= 6; js += step) {
        if (jsDow === js) return true
      }
      return false
    }
    if (range.includes('-')) {
      const [a, b] = range.split('-').map((x) => Number.parseInt(x.trim(), 10))
      const lo = Math.min(a, b)
      const hi = Math.max(a, b)
      for (let k = lo; k <= hi; k++) {
        if ((k - lo) % step !== 0) continue
        const js = k === 7 ? 0 : k
        if (js >= 0 && js <= 6 && jsDow === js) return true
      }
      return false
    }
    const k = Number.parseInt(range.trim(), 10)
    if (!Number.isFinite(k)) return false
    const js = k === 7 ? 0 : k
    return js >= 0 && js <= 6 && jsDow === js
  }
  if (p.includes('-')) {
    const [a, b] = p.split('-').map((x) => Number.parseInt(x.trim(), 10))
    const lo = Math.min(a, b)
    const hi = Math.max(a, b)
    for (let k = lo; k <= hi; k++) {
      const js = k === 7 ? 0 : k
      if (js === jsDow) return true
    }
    return false
  }
  const n = Number.parseInt(p, 10)
  if (!Number.isFinite(n)) return false
  if (n === 7) return jsDow === 0
  return jsDow === n
}

/**
 * @param {string} line
 * @returns {{ minute: string, hour: string, dom: string, month: string, dow: string, command: string } | null}
 */
export function parseCronLine(line) {
  const t = line.trim()
  if (!t || t.startsWith('#')) return null
  const parts = t.split(/\s+/)
  if (parts.length < 6) return null
  const [minute, hour, dom, month, dow, ...rest] = parts
  const command = rest.join(' ')
  if (!command) return null
  return { minute, hour, dom, month, dow, command }
}

/**
 * @param {{ minute: string, hour: string, dom: string, month: string, dow: string }} job
 * @param {Date} date
 */
export function jobMatchesDate(job, date) {
  return (
    fieldMatches(job.minute, date.getMinutes(), 0, 59) &&
    fieldMatches(job.hour, date.getHours(), 0, 23) &&
    fieldMatches(job.dom, date.getDate(), 1, 31) &&
    fieldMatches(job.month, date.getMonth() + 1, 1, 12) &&
    dowFieldMatches(job.dow, date.getDay())
  )
}

/**
 * @param {Record<string, unknown>} ctx
 */
async function readUserCrontabText(ctx) {
  const vfs = ctx.vfs
  if (!vfs || typeof vfs.readFile !== 'function') return ''
  const home = vfs.env?.HOME || '/home/guest'
  const h = String(home).replace(/\/$/, '')
  const path = `${h}/.crontab`
  try {
    const b = await vfs.readFile(path)
    if (!b) return ''
    return ctx.b4a.toString(b)
  } catch {
    return ''
  }
}

/**
 * @param {Record<string, unknown>} ctx
 */
function startBareCron(ctx) {
  /** @type {Set<number>} */
  const running = new Set()
  let timeoutId = null
  let intervalId = null

  async function tick() {
    let text
    try {
      text = await readUserCrontabText(ctx)
    } catch {
      return
    }
    if (!text.trim()) return

    const lines = text.split(/\r?\n/)
    /** @type {{ lineIndex: number, minute: string, hour: string, dom: string, month: string, dow: string, command: string }[]} */
    const jobs = []
    for (let i = 0; i < lines.length; i++) {
      const job = parseCronLine(lines[i])
      if (job) jobs.push({ lineIndex: i, ...job })
    }

    const now = new Date()
    for (const job of jobs) {
      if (!jobMatchesDate(job, now)) continue
      const key = job.lineIndex
      if (running.has(key)) continue
      running.add(key)
      void (async () => {
        try {
          const execLine = ctx.execLine
          if (typeof execLine !== 'function') return
          await execLine(job.command)
        } catch (e) {
          const msg = e?.message || String(e)
          try {
            ctx.console?.error?.(`[bare-cron] ${msg}`)
          } catch {
            /* ignore */
          }
        } finally {
          running.delete(key)
        }
      })()
    }
  }

  registerBareInitdDisposer(() => {
    if (timeoutId != null) clearTimeout(timeoutId)
    if (intervalId != null) clearInterval(intervalId)
    timeoutId = null
    intervalId = null
  })

  const delay = msToNextMinuteBoundary()
  timeoutId = setTimeout(() => {
    timeoutId = null
    void tick()
    intervalId = setInterval(() => {
      void tick()
    }, 60000)
  }, delay)
}

registerBareService({
  name: 'bare-cron',
  start: startBareCron
})