/**
 * Pure helpers for the per-worktree environment provisioning in
 * `scripts/worktree.mjs` — deterministic port + database names derived from
 * the branch, so parallel agents (each in their own worktree) never fight
 * over port 3000, the shared `teqo_test` database, or a second Postgres
 * container on 5432.
 *
 * Contract: `slot` is the single collision domain. Port and BOTH database
 * names derive from the final slot, so a bumped slot frees all three at
 * once. Deterministic for a given (branch, code, live taken-slots set) —
 * the same "depends on live state" determinism the claim-queue branch picker
 * already has.
 */

/** Dev-server ports start here: slot 15 → http://localhost:3115. */
export const DEV_PORT_BASE = 3100

/** Marker line identifying a generated env file (never overwrite manual ones). */
export const GENERATED_ENV_MARKER = '# teqo worktree env (generated by pnpm worktree next)'

/** Slot cap — ports above 3100 + 999 would leave the usual ephemeral range. */
const MAX_SLOT = 999

/** First run of digits in the issue code (`C15` → 15, `B164` → 164); null when none. */
export const numericSlotOfCode = (code) => {
  const match = /([0-9]+)/.exec(code ?? '')
  return match ? Number(match[1]) : null
}

/** Stable 32-bit FNV-1a hash → slot in [0, MAX_SLOT] for codes without digits. */
export const hashSlotOf = (value) => {
  let hash = 0x811c9dc5
  for (const byte of Buffer.from(String(value), 'utf8')) {
    hash ^= byte
    hash = Math.imul(hash, 0x01000193) >>> 0
  }
  return hash % (MAX_SLOT + 1)
}

/** The slot a branch prefers before collision resolution. */
const preferredSlotForBranch = (branch, code) => {
  const numeric = numericSlotOfCode(code)
  return numeric !== null && numeric <= MAX_SLOT ? numeric : hashSlotOf(branch)
}

export const devPortForSlot = (slot) => DEV_PORT_BASE + slot
export const devDatabaseForSlot = (slot) => `teqo_wt${slot}`
export const testDatabaseForSlot = (slot) => `teqo_wt${slot}_test`

/** DB name charset guard — derived names are fed into `CREATE DATABASE` SQL. */
export const isGeneratedDatabaseName = (name) => /^teqo_wt[0-9]+(_test)?$/.test(name ?? '')

/**
 * Final environment for a branch. `takenSlots` = slots already claimed by
 * OTHER live worktrees; bumps +1 until free (bounded — live slot sets are
 * tiny). Every value a consumer needs derives from the one final slot.
 */
export const worktreeEnvironment = ({ branch, code, takenSlots = new Set() }) => {
  let slot = preferredSlotForBranch(branch, code)
  while (takenSlots.has(slot)) slot += 1
  return {
    slot,
    devPort: devPortForSlot(slot),
    devDatabase: devDatabaseForSlot(slot),
    testDatabase: testDatabaseForSlot(slot),
  }
}