/**
 * Lightweight local RAG for QVAC — no native embeddings required.
 * Keyword retrieval over guide snippets + live chart catalog.
 */

/** Built-in operator knowledge (subset of user-guide). */
const GUIDE_DOCS = [
  {
    id: 'guide:connect',
    title: 'Connect',
    text: 'Connect to a PearData agent with public key or pd1 invite. Viewer vs operator vs admin roles. Saved bookmarks restore agents. Active peer is used by all tools.',
  },
  {
    id: 'guide:charts',
    title: 'Charts',
    text: 'Metrics wall with sections TOC, play pause, time presets 1m 5m 15m 1h 6h, pin board, correlate brush, related metrics, chart types line area stacked bar pie, dimension legend.',
  },
  {
    id: 'guide:alerts',
    title: 'Alerts',
    text: 'Anomaly list with severity warning critical, Show jumps to chart, Correlate opens metric correlations around event time, silence TTL re-enables.',
  },
  {
    id: 'guide:processes',
    title: 'Processes',
    text: 'Live process table from /proc when PEARDATA_PROCESSES=1, sort by cpu rss, tree view, CSV export, open top process charts.',
  },
  {
    id: 'guide:logs',
    title: 'Logs',
    text: 'System logs journal default, anomalies source, audit admin, follow stream, search unit priority.',
  },
  {
    id: 'guide:retention',
    title: 'Data retention',
    text: 'Settings Data Manager hot tier0 warm tier1 HyperDB prune age disk budget. Longer chart windows may be sparse until samples accumulate.',
  },
  {
    id: 'guide:qvac',
    title: 'QVAC',
    text: 'Local AI copilot on desktop. Tools call agent RPC never invent metrics. Profiles lite recommended strong. Install @qvac/sdk for full LLM else tools-only fallback.',
  },
  {
    id: 'guide:fleet',
    title: 'Fleet',
    text: 'Multi-host roster set active reconnect forget. Parent collector aggregates child getHealth. getFleetHealth RPC.',
  },
  {
    id: 'guide:kpis',
    title: 'Core KPIs',
    text: 'system.cpu user system idle iowait, system.ram used, system.load load1, system.net received sent, system.io reads writes, mem.available.',
  },
]

/**
 * @param {string} text
 * @returns {string[]}
 */
function tokens(text) {
  return String(text || '')
    .toLowerCase()
    .split(/[^a-z0-9._-]+/)
    .filter((t) => t.length > 1)
}

/**
 * Build docs from chart catalog map.
 * @param {Record<string, object>} catalog
 * @param {number} [cap]
 */
export function catalogDocs(catalog, cap = 400) {
  /** @type {Array<{ id: string, title: string, text: string }>} */
  const docs = []
  for (const [id, meta] of Object.entries(catalog || {})) {
    if (docs.length >= cap) break
    const dims = Array.isArray(meta.dimensions)
      ? meta.dimensions
          .map((d) => (typeof d === 'string' ? d : d?.id || d?.name || ''))
          .filter(Boolean)
          .join(' ')
      : ''
    docs.push({
      id: `chart:${id}`,
      title: meta.title || id,
      text: [id, meta.title, meta.context, meta.family, meta.plugin, meta.units, dims]
        .filter(Boolean)
        .join(' '),
    })
  }
  return docs
}

/**
 * @param {string} query
 * @param {Array<{ id: string, title: string, text: string }>} docs
 * @param {number} [topK]
 */
export function retrieve(query, docs, topK = 6) {
  const qToks = tokens(query)
  if (!qToks.length || !docs?.length) return []
  /** @type {Array<{ id: string, title: string, text: string, score: number }>} */
  const scored = []
  for (const d of docs) {
    const hay = tokens(`${d.title} ${d.text}`)
    const set = new Set(hay)
    let score = 0
    for (const t of qToks) {
      if (set.has(t)) score += 2
      else if (hay.some((h) => h.includes(t) || t.includes(h))) score += 1
    }
    if (d.id.startsWith('chart:') && qToks.some((t) => d.id.includes(t))) score += 3
    if (score > 0) scored.push({ ...d, score })
  }
  scored.sort((a, b) => b.score - a.score || a.id.localeCompare(b.id))
  return scored.slice(0, topK)
}

/**
 * @param {{
 *   query: string,
 *   catalog?: Record<string, object>,
 *   topK?: number,
 *   includeGuide?: boolean,
 * }} opts
 */
export function buildRagContext(opts) {
  const docs = []
  if (opts.includeGuide !== false) docs.push(...GUIDE_DOCS)
  if (opts.catalog) docs.push(...catalogDocs(opts.catalog))
  const hits = retrieve(opts.query, docs, opts.topK ?? 6)
  if (!hits.length) return ''
  const lines = hits.map((h) => {
    const snippet = h.text.length > 180 ? h.text.slice(0, 177) + '…' : h.text
    return `- [${h.id}] ${h.title}: ${snippet}`
  })
  return `Relevant local knowledge (do not invent beyond tools + this context):\n${lines.join('\n')}`
}

export { GUIDE_DOCS }