// Pure grouping/counting for the "Diese Antwort stützt sich auf" evidence header. No React, testable.
// Splits evidence into binding norms (Kernnormen) vs. soft-law guidance (Leitlinien) using the
// Legal-KG-owned `bindingness` fact (APEX rule) — the FE never derives bindingness itself. When the
// fact is absent it degrades to a neutral per-regulation breakdown (no norm/guidance labels, no
// fabricated legal classification).

import type { EvidenceUnit } from './contract'
import { resolveRegulation } from './regulation-display'

export type Bindingness = 'binding' | 'guidance' | 'unknown'

export interface FamilyGroup {
  key: string // stable family key (grouping)
  label: string // human-readable regulation name
  sections: string[] // distinct provisions in first-seen order (e.g. "Art. 13", "§ 25")
  units: number // raw evidence units in this family
  bindingness: Bindingness
}

export interface EvidenceSummaryModel {
  groups: FamilyGroup[]
  norms: FamilyGroup[] // bindingness === 'binding'
  guidance: FamilyGroup[] // bindingness === 'guidance'
  other: FamilyGroup[] // bindingness unknown
  hasBindingness: boolean // at least one unit carries the Legal-KG fact
  normProvisions: number // distinct binding provisions (Kernnormen)
  guidanceCount: number // distinct guidance documents (Leitlinien)
  unitCount: number // total evidence units
}

export function groupByFamily(evidence: EvidenceUnit[]): FamilyGroup[] {
  const byKey = new Map<string, FamilyGroup>()
  for (const e of evidence) {
    const { familyKey, familyLabel } = resolveRegulation({
      code: e.regulation_code || e.document,
      short: e.document,
    })
    let g = byKey.get(familyKey)
    if (!g) {
      g = { key: familyKey, label: familyLabel, sections: [], units: 0, bindingness: 'unknown' }
      byKey.set(familyKey, g)
    }
    g.units += 1
    if (e.section && !g.sections.includes(e.section)) g.sections.push(e.section)
    if (e.bindingness && g.bindingness === 'unknown') g.bindingness = e.bindingness
  }
  return [...byKey.values()]
}

/** distinct provisions for a family; falls back to raw unit count when no section is known. */
export function provisionCount(g: FamilyGroup): number {
  return g.sections.length || g.units
}

/** "5 Artikel" / "§ 25" / "3 Fundstellen" — the noun follows the family's own citation style. */
export function provisionSummary(g: FamilyGroup): string {
  const n = g.sections.length
  if (n === 0) return `${g.units} ${g.units === 1 ? 'Fundstelle' : 'Fundstellen'}`
  if (n === 1) return g.sections[0]
  if (g.sections.every((s) => /^\s*art/i.test(s))) return `${n} Artikel`
  if (g.sections.every((s) => s.trim().startsWith('§'))) return `${n} §§`
  return `${n} Fundstellen`
}

export function summarizeEvidence(evidence: EvidenceUnit[]): EvidenceSummaryModel {
  const groups = groupByFamily(evidence)
  const norms = groups.filter((g) => g.bindingness === 'binding')
  const guidance = groups.filter((g) => g.bindingness === 'guidance')
  const other = groups.filter((g) => g.bindingness === 'unknown')
  return {
    groups,
    norms,
    guidance,
    other,
    hasBindingness: norms.length > 0 || guidance.length > 0,
    normProvisions: norms.reduce((n, g) => n + provisionCount(g), 0),
    guidanceCount: guidance.length,
    unitCount: evidence.length,
  }
}