/**
 * Token estimation utilities.
 * Uses ~4 chars per token heuristic (works well for English + code).
 */

export function estimateTokens(text: string): number {
  if (!text) return 0
  return Math.ceil(text.length / 4)
}

export function estimateMessagesTokens(
  messages: Array<{ role: string; content: unknown }>
): number {
  let total = 0
  for (const msg of messages) {
    const content =
      typeof msg.content === "string"
        ? msg.content
        : JSON.stringify(msg.content ?? "")
    total += estimateTokens(content)
    // Overhead per message (~4 tokens for role, separators)
    total += 4
  }
  return total
}

export function estimateToolSchemaTokens(schemas: Array<Record<string, unknown>>): number {
  let total = 0
  for (const schema of schemas) {
    total += estimateTokens(String(schema.description ?? ""))
    total += estimateTokens(String(schema.name ?? ""))
    total += estimateTokens(JSON.stringify(schema.input_schema ?? {}))
  }
  return total
}

export function formatTokenCount(tokens: number): string {
  if (tokens >= 1_000_000) return `${(tokens / 1_000_000).toFixed(1)}M`
  if (tokens >= 1_000) return `${(tokens / 1_000).toFixed(1)}K`
  return String(tokens)
}