/* eslint-disable no-bitwise -- FNV-style mixing requires bitwise ops */

const FNV32_OFFSET = 0x811c9dc5 >>> 0
const FNV32_PRIME = 0x01000193 >>> 0

export interface RetryPolicyInput {
  maxAttempts?: number
  initialBackoffMs?: number
}

export interface RetryPolicyNormalized {
  maxAttempts: number
  initialBackoffMs: number
}

export function cronToIntervalMs(expression: string): number {
  const trimmed = expression.trim()
  if (/^\*\/\d+ \* \* \* \*$/.test(trimmed)) {
    const value = Number(trimmed.slice(2, trimmed.indexOf(' ')))
    if (!Number.isNaN(value) && value > 0) {
      return value * 60_000
    }
  }
  throw new Error(
    `Unsupported cron expression "${expression}". V2 currently supports "*/N * * * *" minute expressions.`
  )
}

/**
 * Lightweight FNV‑1a 32‑bit bitmask for grouping tags inside JS until native policy routing lands.
 */
export function tagMaskFromStrings(tags: readonly string[]): number {
  let hash = FNV32_OFFSET
  const mix = () => {
    hash = Math.imul(hash, FNV32_PRIME)
    hash >>>= 0
  }
  for (const tag of tags) {
    const t = typeof tag === 'string' ? tag : String(tag)
    for (let i = 0; i < t.length; i += 1) {
      hash ^= t.charCodeAt(i)
      mix()
    }
    hash ^= 0xb3b3 >>> 0
    mix()
  }
  return hash >>> 0
}

export function normalizeRetryPolicy(
  input: RetryPolicyInput | undefined
): RetryPolicyNormalized {
  const maxAttemptsRaw = input?.maxAttempts ?? 0
  const initialBackoffRaw = input?.initialBackoffMs ?? 0
  const maxAttempts = Number.isFinite(maxAttemptsRaw)
    ? Math.max(0, Math.trunc(maxAttemptsRaw))
    : 0
  const initialBackoffMs = Number.isFinite(initialBackoffRaw)
    ? Math.max(0, Math.trunc(initialBackoffRaw))
    : 0
  return { maxAttempts, initialBackoffMs }
}

export function validatePersistWireSchema(wireJson: string): {
  valid: boolean
  reason?: string
} {
  try {
    const raw = JSON.parse(wireJson) as { version?: number; tasks?: unknown }
    if (raw.version !== 1) {
      return { valid: false, reason: 'unsupported_version' }
    }
    if (!Array.isArray(raw.tasks)) {
      return { valid: false, reason: 'tasks_not_array' }
    }
    return { valid: true }
  } catch {
    return { valid: false, reason: 'invalid_json' }
  }
}