import { Base64 } from 'js-base64'
import { diff } from 'jest-diff'

// Reference: https://jestjs.io/docs/expect#custom-matchers-api
const base64Matchers = (): jest.ExpectExtendMap => ({
  /**
   * Compares a Base64-encoded object to an expected JS value.
   * This approach of decoding first avoids false-negatives associated with different ordering of object keys.
   */
  base64ToEqual(actual: string, expected: unknown): jest.CustomMatcherResult {
    const options = {
      comment: 'Base64 parsed and equal',
      isNot: this.isNot,
      promise: this.promise,
    }

    let decoded
    try {
      decoded = Base64.decode(actual)
    } catch (err) {
      const errMessage =
        err && typeof err === 'object' && (err as Error).message
      return {
        pass: false,
        message: () => `Failed to decode Base64: ${errMessage}`,
      }
    }

    let parsed: unknown
    try {
      parsed = JSON.parse(decoded)
    } catch (err) {
      const errMessage =
        err && typeof err === 'object' && (err as Error).message
      return {
        pass: false,
        message: () => `Failed to parse as JSON: ${errMessage}`,
      }
    }

    const pass = this.equals(parsed, expected)

    let message: () => string
    if (pass) {
      message = () =>
        `${this.utils.matcherHint(
          'base64ToEqual',
          undefined,
          undefined,
          options
        )}\n\n` +
        `Expected: not ${this.utils.printExpected(expected)}\n` +
        `Received: ${this.utils.printReceived(parsed)}`
    } else {
      message = () => {
        const diffString = diff(expected, parsed, {
          expand: this.expand,
        })

        let result = `${this.utils.matcherHint(
          'base64ToEqual',
          undefined,
          undefined,
          options
        )}\n\n`

        if (diffString && diffString.includes('- Expect')) {
          result += `Difference:\n\n${diffString}`
        } else {
          result +=
            `Expected: ${this.utils.printExpected(expected)}\n` +
            `Received: ${this.utils.printReceived(parsed)}`
        }

        return result
      }
    }

    return {
      message,
      pass,
    }
  },
})

export default base64Matchers