/** The log of a server: events to stdout, warnings and errors in colour to stderr, and requests when they are on. */
export type Log = {
  event: (text: string) => void
  warn: (text: string) => void
  error: (text: string) => void
  request: (text: string) => void
}

/** A log that writes nothing, for tests. */
export const QUIET: Log = { event() {}, warn() {}, error() {}, request() {} }

/**
 * The log of a server. With timestamps each line starts with the local time with milliseconds; requests logs each
 * request to stderr, otherwise request writes nothing.
 */
export function createLog(options: { timestamps: boolean; requests: boolean }): Log {
  const line = (text: string) => {
    if (!options.timestamps) {
      return text
    }
    const now = new Date()
    const pad = (value: number, size = 2) => String(value).padStart(size, '0')
    return `${pad(now.getHours())}:${pad(now.getMinutes())}:${pad(now.getSeconds())}.${pad(now.getMilliseconds(), 3)} ${text}`
  }
  return {
    event: (text) => console.log(line(text)),
    warn: (text) => console.error(`\x1b[33m${line(`warning: ${text}`)}\x1b[0m`),
    error: (text) => console.error(`\x1b[31m${line(`error: ${text}`)}\x1b[0m`),
    request: options.requests ? (text) => console.error(line(text)) : () => {},
  }
}

/** Whether --timestamps auto|on|off asks for timestamps: auto only when stdout is a terminal. */
export function timestampsOn(choice: string) {
  return choice === 'on' || (choice === 'auto' && process.stdout.isTTY === true)
}

/** Prints the message in red to stderr as an error and ends the process with status 2. */
export function fail(message: string): never {
  console.error(`\x1b[31merror: ${message}\x1b[0m`)
  process.exit(2)
}