/**
 * Pure helpers for `scripts/worktree.mjs` — branch naming derived from the
 * claim-queue issue, shared with the unit tests. Naming: `<code>-<slug>`
 * where `code` is the frontmatter `id` (ex. `C15`) and `slug` is the pt-BR
 * title slugified with the repo's `src/lib/slug.ts` (accents stripped,
 * non-alphanumeric → `-`).
 */

import { slugify } from '../../src/lib/slug.ts'

/**
 * Prefix of every `/plan-issue` planning-worktree branch (`pnpm worktree
 * plan`). Lowercase-led `plans/…`, so it can never collide with a `next`
 * branch — `<Code>-<slug>` is always uppercase-led — neither in branch name
 * nor, structurally, in the port/slot space derived from the branch.
 */
export const PLAN_BRANCH_PREFIX = 'plans/plan-issue'

/** Total branch-name budget for plan branches — mirrors `branchNameForIssue`. */
const PLAN_BRANCH_MAX_LENGTH = 60

/** Strip the leading `<code> — ` (or any dash variant) off a title. */
const stripCodePrefix = (title, code) => {
  const escaped = code.replace(/[.*+?^${}()|[\]\\]/g, '\\$&')
  return title.replace(new RegExp(`^${escaped}\\s*[—–:-]?\\s*`), '')
}

/**
 * `code` = frontmatter `id` (falls back to the leading `ID — ` token of the
 * title); `subject` = the title with that prefix removed.
 */
export const issueCodeAndSubject = (issue) => {
  const title = issue.title ?? ''
  const code = typeof issue.meta?.id === 'string' && issue.meta.id.length > 0 ? issue.meta.id : null
  const subject = code
    ? stripCodePrefix(title, code)
    : title.replace(/^[A-Za-z0-9+]+\s*[—–:-]?\s*/, '')
  return { code, subject }
}

/**
 * `<code>-<slug>` truncated to `maxLength` total characters (always keeping
 * the code). Throws when the issue has no id — fail loudly, never invent.
 */
export const branchNameForIssue = (issue, maxLength = 60) => {
  const { code, subject } = issueCodeAndSubject(issue)
  if (!code) {
    throw new Error(`Issue sem frontmatter id: #${issue.number} ${issue.title}`)
  }
  const slug = slugify(subject) || 'issue'
  const full = `${code}-${slug}`
  if (full.length <= maxLength) return full
  const keep = Math.max(1, maxLength - code.length - 1)
  return `${code}-${slug.slice(0, keep)}`
}

/**
 * Branch for a `/plan-issue` planning worktree. Every invocation must land on
 * a DIFFERENT branch so parallel planning sessions coexist:
 *  - `bag` given → `plans/plan-issue-<bag-slug>`; if that name is already
 *    taken, `plans/plan-issue-<bag-slug>-2`, `-3`, …
 *  - no `bag` → the next free sequential `plans/plan-issue-1`, `-2`, `-3`, …
 * `taken` = branch short-names already alive (local refs + origin); when a
 * name is free it is reused only as a name-free slot — the branch is created
 * fresh from `origin/main` each time. The lowercase `plans/…` prefix cannot
 * collide with `next`'s uppercase-led `<Code>-<slug>` branches.
 */
export const planBranchName = ({ bag = '', taken = new Set() }) => {
  const hasBag = typeof bag === 'string' && bag.trim().length > 0

  if (!hasBag) {
    for (let n = 1; ; n += 1) {
      const candidate = `${PLAN_BRANCH_PREFIX}-${n}`
      if (!taken.has(candidate)) return candidate
    }
  }

  const slug = slugify(bag) || 'plano'
  const base = `${PLAN_BRANCH_PREFIX}-${slug.slice(
    0,
    PLAN_BRANCH_MAX_LENGTH - PLAN_BRANCH_PREFIX.length - 1,
  )}`
  if (!taken.has(base)) return base

  for (let n = 2; ; n += 1) {
    const suffix = `-${n}`
    const keep = Math.max(1, PLAN_BRANCH_MAX_LENGTH - PLAN_BRANCH_PREFIX.length - 1 - suffix.length)
    const candidate = `${PLAN_BRANCH_PREFIX}-${slug.slice(0, keep)}${suffix}`
    if (!taken.has(candidate)) return candidate
  }
}