/**
 * cli:derive-change-impact — trace.ts
 *
 * The UPSTREAM TRACE of a data-model change: `/ba-create-data-model` refuses
 * an entity or an attribute nobody upstream names (« the set of entity
 * sources is CLOSED »: use-case.md + règles-métier.md of THIS module). The
 * same search, deterministic: every form of the term (PascalCase, the words
 * it splits into, kebab, snake), whole-word, accents folded — the DM-025
 * approach (audit-ba rules/dm.ts) — over the module's UC and rules docs.
 *
 * A miss BLOCKS the change with the route « write the UC / the rule first »;
 * the playbook says the honest limit: a synonym the search cannot see blocks
 * wrongly — the answer is then the missing UC/rule, which is the door
 * create-data-model wants anyway.
 */
import type { ScopeCorpus } from './corpus.js'
import type { TraceHit, TraceReport } from './types.js'

export function fold(s: string): string {
  return s
    .normalize('NFD')
    .replace(/[̀-ͯ]/g, '')
    .toLowerCase()
}

/** `DueDate` → [`duedate`, `due date`, `due-date`, `due_date`]; `Amount` → [`amount`]. */
export function termForms(term: string): string[] {
  const raw = term.trim()
  if (raw === '') return []
  const words = raw
    .replace(/([a-z0-9])([A-Z])/g, '$1 $2')
    .replace(/[_-]+/g, ' ')
    .split(/\s+/)
    .filter(Boolean)
    .map(fold)
  const forms = new Set<string>([fold(raw)])
  if (words.length > 1) {
    forms.add(words.join(' '))
    forms.add(words.join('-'))
    forms.add(words.join('_'))
    forms.add(words.join(''))
  }
  // A foreign key `ProspectId` IS the relation to « prospect » — the upstream
  // names the concept, never the column (DM-013 semantics). The stem's forms
  // count; `Id` alone never does.
  if (/Id$/.test(raw) && raw.length > 2) {
    for (const f of termForms(raw.slice(0, -2))) forms.add(f)
  }
  return [...forms].filter((f) => f.length >= 2 && f !== 'id')
}

const escapeRe = (s: string): string => s.replace(/[.*+?^${}()|[\]\\]/g, '\\$&')

/** Whole-word, accent-folded search of every form of `term` in the module's UC + rules docs. */
export function traceTerm(corpus: ScopeCorpus, term: string): TraceReport {
  const forms = termForms(term)
  const hits: TraceHit[] = []
  const docs = [...corpus.useCaseDocs, ...corpus.rulesDocs]
  if (forms.length === 0) return { searched: false, found: false, hits, docsScanned: docs.length }
  const res = forms.map((f) => new RegExp(`(^|[^a-z0-9_])${escapeRe(f)}([^a-z0-9_]|$)`))
  for (const d of docs) {
    const lines = d.text.split(/\r?\n/)
    for (let i = 0; i < lines.length; i++) {
      const folded = fold(lines[i]!)
      if (res.some((re) => re.test(folded))) {
        hits.push({ file: `${corpus.scope.app}/${corpus.scope.module}/${d.relPath}`, line: i + 1, excerpt: lines[i]!.trim().slice(0, 160) })
        if (hits.length >= 20) return { searched: true, found: true, hits, docsScanned: docs.length }
      }
    }
  }
  return { searched: true, found: hits.length > 0, hits, docsScanned: docs.length }
}