/**
 * Declarative kernel boot stage graph for `/proc/bare_os/boot_graph.json`.
 * Mirrors the default sequence in kernel/init (trusted boot path).
 */

const DEFAULT_BOOT_STAGES = Object.freeze([
  'boot.policy',
  'os-release',
  'motd',
  'rc.profile',
  'rc',
  'rc.d',
  'rc.local',
  'kernel.d',
  'kernel.ext.d',
  'onboot',
  'session.banner',
  'kernel.selftest',
  'repl'
])

/**
 * @param {{ bootReadyJson?: () => string, stageMsHistogram?: Record<string, number> }} [opts]
 */
export function buildBareOsBootGraphProcJson(opts = {}) {
  const nodes = DEFAULT_BOOT_STAGES.map((id, i) => ({
    id,
    order: i,
    bootStage: bootStageForKernelLabel(id)
  }))
  /** @type {{ from: string, to: string, kind: string }[]} */
  const edges = []
  for (let i = 0; i < nodes.length - 1; i++) {
    edges.push({
      from: nodes[i].id,
      to: nodes[i + 1].id,
      kind: 'sequence'
    })
  }
  let ready = {}
  try {
    const t =
      opts.bootReadyJson && typeof opts.bootReadyJson === 'function'
        ? opts.bootReadyJson()
        : ''
    ready = t ? JSON.parse(String(t).trim() || '{}') : {}
  } catch {
    ready = {}
  }
  const hist =
    opts.stageMsHistogram && typeof opts.stageMsHistogram === 'object'
      ? opts.stageMsHistogram
      : {}
  return {
    schema: 1,
    note: 'Kernel boot stage edges (declarative); latency histogram is populated when journal export is enabled.',
    nodes,
    edges,
    stageMsHistogram: hist,
    bootReady: ready,
    atMs: Date.now()
  }
}

/**
 * @param {string} label
 */
function bootStageForKernelLabel(label) {
  const s = String(label || '').toLowerCase()
  if (s === 'boot.policy') return 'policy'
  if (s === 'os-release' || s === 'motd') return 'preflight'
  if (s.startsWith('rc') || s === 'kernel.d' || s === 'kernel.ext.d')
    return 'rc'
  if (s === 'onboot') return 'onboot'
  if (s.includes('selftest')) return 'selftest'
  if (s.includes('repl') || s.includes('banner')) return 'shell'
  return 'other'
}