/**
 * lib/detail-tab-strip.ts — SSOT of "how many triggers does the rendered
 * detail tab bar carry" and of the tab-budget thresholds.
 *
 * The rendered strip of a detail page is NOT the authored JSON: a unified
 * fiche (detail + form views, read-first — lib/edit-surface.ts) renders its
 * `tabs[]` as section cards ABOVE the bar, band-placed related tabs
 * (placement 'band', the derived default for `summary` —
 * lib/page-spec-related-tabs.relatedTabPlacementOf) render as cartouches
 * above the strip, and a legacy fiche whose only strip content is related
 * tabs gains ONE synthetic « info » trigger for its own fields. This module
 * mirrors scaffold-component's resolution (render/detail.ts) so the budget
 * rules count exactly what the reader sees — never re-encode any of it.
 *
 * Consumers:
 *   - create-screen/cli/derive-related-tabs check.ts — RTV-108 (the tab
 *     budget, PRD-133's engine)
 *   - create-prd/cli/derive-detail-summary          — PRD-134's engine (a
 *     crowded strip demands the summary band)
 *   - development/audit-dev-frontend               — DEV-UI-047 (unified
 *     catch-up) reads entityViewsFromPagespecFilenames
 */
import { parseRelatedTabs, relatedTabPlacementOf } from './page-spec-related-tabs.js'
import { pickUiDesignOverlay, resolveEditMode } from './ui-design-overlay.js'
import { resolveEditSurface, type EditSurface } from './edit-surface.js'

/** Above this rendered-trigger count the bar overflows the reader — warn. */
export const DETAIL_TAB_BUDGET_WARN = 7
/** Above this the fiche is a binder, not a fiche — err. */
export const DETAIL_TAB_BUDGET_ERR = 9
/** From this strip size on, a fiche without a summary band loses the record's
 *  identity/state as soon as the reader leaves the first tab (PRD-134). */
export const DETAIL_SUMMARY_DEMAND_THRESHOLD = 4

/** `<Entity>.<view>.md` — the pagespec filename convention (same family as
 *  audit-dev-frontend's DEV_UI_031_PAGESPEC_RE). */
const PAGESPEC_FILENAME_RE = /^([A-Z][A-Za-z0-9]*)\.([a-z][a-z-]*)\.md$/

/**
 * Group pagespec FILENAMES into the per-entity view set `resolveEditSurface`
 * consumes. Basenames only; non-matching names are skipped.
 */
export function entityViewsFromPagespecFilenames(
  filenames: Iterable<string>,
): Map<string, Set<string>> {
  const out = new Map<string, Set<string>>()
  for (const name of filenames) {
    const m = PAGESPEC_FILENAME_RE.exec(name)
    if (!m) continue
    let views = out.get(m[1])
    if (views === undefined) {
      views = new Set<string>()
      out.set(m[1], views)
    }
    views.add(m[2])
  }
  return out
}

export interface DetailStripResolution {
  /** The entity's edit surface — 'unified' zeroes the field-tab term. */
  surface: EditSurface
  /** Field tabs that RENDER as strip triggers (0 on a unified fiche). */
  fieldTabCount: number
  /** True when the legacy fiche synthesises the « info » trigger (no field
   *  tabs, ≥1 strip-placed related tab) — it IS a rendered trigger. */
  syntheticInfoTab: boolean
  /** Related tabs whose resolved placement is 'band' (no trigger). */
  bandCount: number
  /** Related tabs whose resolved placement is 'tab' (one trigger each). */
  stripRelatedCount: number
  /** Zod-rejected relatedTabs entries — RTV-104's findings, never budget mass. */
  rejectedCount: number
  /** Total triggers on the rendered bar: fieldTabCount + synthetic + stripRelated. */
  stripTotal: number
}

/**
 * Resolve the RENDERED tab bar of one `view: detail` pagespec block, mirroring
 * scaffold-component render/detail.ts exactly:
 *   - surface = resolveEditSurface(entityViews, resolveEditMode(block, overlay))
 *   - unified → tabs[] renders as section cards, field-tab term = 0
 *   - related tabs partition through relatedTabPlacementOf (band ⇒ no trigger)
 *   - legacy + no field tabs + ≥1 strip related ⇒ the synthetic « info » trigger
 * `entityViews` may be undefined (no filename inventory) — the surface then
 * resolves 'legacy', the renderer's own behaviour for an unknown view set.
 */
export function resolveDetailStrip(
  block: Record<string, unknown>,
  entityViews: Iterable<string> | undefined,
): DetailStripResolution {
  const surface = resolveEditSurface(entityViews, resolveEditMode(block, pickUiDesignOverlay(block)))

  const rawTabs = Array.isArray(block.tabs) ? block.tabs : []
  const authoredFieldTabs = rawTabs.length

  const { tabs, rejected } = parseRelatedTabs(block.relatedTabs)
  let bandCount = 0
  let stripRelatedCount = 0
  for (const tab of tabs) {
    if (relatedTabPlacementOf(tab) === 'band') bandCount++
    else stripRelatedCount++
  }

  const fieldTabCount = surface === 'unified' ? 0 : authoredFieldTabs
  const syntheticInfoTab = surface !== 'unified' && authoredFieldTabs === 0 && stripRelatedCount > 0

  return {
    surface,
    fieldTabCount,
    syntheticInfoTab,
    bandCount,
    stripRelatedCount,
    rejectedCount: rejected.length,
    stripTotal: fieldTabCount + (syntheticInfoTab ? 1 : 0) + stripRelatedCount,
  }
}