import * as fs from 'node:fs'
import * as os from 'node:os'
import * as crypto from 'node:crypto'

/** Based on https://github.com/actions/toolkit/blob/4e3b068ce116d28cb840033c02f912100b4592b0/packages/core/src/file-command.ts */
export function setOutput(key, value) {
  const filePath = process.env['GITHUB_OUTPUT'] || ''
  if (filePath) {
    return issueFileCommand('OUTPUT', prepareKeyValueMessage(key, value))
  }
  process.stdout.write(os.EOL)
}

function issueFileCommand(command, message) {
  const filePath = process.env[`GITHUB_${command}`]
  if (!filePath) {
    throw new Error(
      `Unable to find environment variable for file command ${command}`
    )
  }
  if (!fs.existsSync(filePath)) {
    throw new Error(`Missing file at path: ${filePath}`)
  }

  fs.appendFileSync(filePath, `${toCommandValue(message)}${os.EOL}`, {
    encoding: 'utf8'
  })
}

function prepareKeyValueMessage(key, value) {
  const delimiter = `gh-delimiter-${crypto.randomUUID()}`
  const convertedValue = toCommandValue(value)

  // These should realistically never happen, but just in case someone finds a
  // way to exploit uuid generation let's not allow keys or values that contain
  // the delimiter.
  if (key.includes(delimiter)) {
    throw new Error(
      `Unexpected input: name should not contain the delimiter "${delimiter}"`
    )
  }

  if (convertedValue.includes(delimiter)) {
    throw new Error(
      `Unexpected input: value should not contain the delimiter "${delimiter}"`
    )
  }

  return `${key}<<${delimiter}${os.EOL}${convertedValue}${os.EOL}${delimiter}`
}

function toCommandValue(input) {
  if (input === null || input === undefined) {
    return ''
  } else if (typeof input === 'string' || input instanceof String) {
    return input
  }
  return JSON.stringify(input)
}