/**
 * Chart display modes — how a metrics card should paint its series.
 *
 * Catalog agents emit chartType: line | area | stacked.
 * The desktop can also render bar / multibar / pie where they make sense.
 */

/** @typedef {'line'|'area'|'stacked'|'bar'|'multibar'|'pie'} ChartMode */

/** @type {ChartMode[]} */
export const CHART_MODES = ['line', 'area', 'stacked', 'bar', 'multibar', 'pie']

/** Short labels for the type toggle button */
export const CHART_MODE_LABEL = {
  line: 'line',
  area: 'area',
  stacked: 'stack',
  bar: 'bar',
  multibar: 'bars',
  pie: 'pie',
}

/**
 * @param {unknown} raw
 * @returns {ChartMode}
 */
export function normalizeChartMode(raw) {
  const m = String(raw || 'line')
    .trim()
    .toLowerCase()
    .replace(/[_-]/g, '')
  if (m === 'multibar' || m === 'bargroup') return 'multibar'
  if (m === 'stack') return 'stacked'
  if (CHART_MODES.includes(/** @type {ChartMode} */ (m))) {
    return /** @type {ChartMode} */ (m)
  }
  return 'line'
}

/**
 * Default mode from catalog metadata.
 * @param {object} [meta]
 * @returns {ChartMode}
 */
export function defaultModeFromMeta(meta = {}) {
  return normalizeChartMode(meta.chartType || meta.chart_type || 'line')
}

/**
 * @param {object} [meta]
 */
function dimCount(meta = {}) {
  const dims = meta.dimensions
  if (Array.isArray(dims)) return dims.length
  if (dims && typeof dims === 'object') return Object.keys(dims).length
  return 0
}

/**
 * Composition charts (parts of a whole) — pie / stacked are natural.
 * @param {object} [meta]
 */
export function isCompositionChart(meta = {}) {
  const mode = defaultModeFromMeta(meta)
  if (mode === 'stacked') return true
  const units = String(meta.units || '')
  if (/%|percentage|percent/i.test(units)) return true
  const id = String(meta.id || meta.name || '')
  // Common composition contexts
  if (/\.(cpu|ram|swap|slab|kernel|states|usage)$/i.test(id)) return true
  if (/^(system\.cpu|system\.ram|mem\.(swap|kernel|slab))/i.test(id)) return true
  return false
}

/**
 * Modes that make sense for this chart (catalog default first).
 * @param {object} [meta]
 * @returns {ChartMode[]}
 */
export function allowedModesFor(meta = {}) {
  const preferred = defaultModeFromMeta(meta)
  const n = dimCount(meta)
  const composition = isCompositionChart(meta)
  /** @type {Set<ChartMode>} */
  const set = new Set(['line', 'area'])

  if (n !== 1) set.add('stacked')
  set.add('bar')
  if (n === 0 || (n >= 2 && n <= 16)) set.add('multibar')
  if (composition || preferred === 'stacked') set.add('pie')

  // Always allow the catalog default
  set.add(preferred)

  const order = /** @type {ChartMode[]} */ ([
    preferred,
    ...CHART_MODES.filter((m) => m !== preferred && set.has(m)),
  ])
  return order
}

/**
 * Cycle to the next allowed mode.
 * @param {ChartMode|string} current
 * @param {object} [meta]
 * @returns {ChartMode}
 */
export function nextChartMode(current, meta = {}) {
  const allowed = allowedModesFor(meta)
  const cur = normalizeChartMode(current)
  const idx = allowed.indexOf(cur)
  return allowed[(idx < 0 ? 0 : idx + 1) % allowed.length]
}

/**
 * Human hint for tooltips / empty states.
 * @param {ChartMode|string} mode
 */
export function chartModeHint(mode) {
  switch (normalizeChartMode(mode)) {
    case 'area':
      return 'Filled time series — good for volume and rates'
    case 'stacked':
      return 'Stacked over time — parts of a whole'
    case 'bar':
      return 'Columns over time — compare magnitude per sample'
    case 'multibar':
      return 'Grouped bars — compare dimensions side by side'
    case 'pie':
      return 'Snapshot share — latest values as a whole'
    default:
      return 'Lines over time — independent series'
  }
}