import { afterEach, vi } from 'vitest'
import { _encodeUtf8Polyfill, decodeUtf8, encodeUtf8, fromCamelCase, splice, trimLeft, utf8ByteLength } from './string'

describe('lib0/string', () => {
  it('should trim left', () => {
    expect(trimLeft('   hello')).toBe('hello')
    expect(trimLeft('\thello')).toBe('hello')
    expect(trimLeft('hello')).toBe('hello')
  })

  it('should convert from camel case', () => {
    expect(fromCamelCase('fooBarBaz', '-')).toBe('foo-bar-baz')
    expect(fromCamelCase('FooBar', '_')).toBe('_foo_bar') // implementation adds leading underscore for initial uppercase
    expect(fromCamelCase('foo', '_')).toBe('foo')
  })

  it('should compute utf8 byte length', () => {
    expect(utf8ByteLength('hello')).toBe(5)
    expect(utf8ByteLength('✓')).toBe(3)
    expect(utf8ByteLength('')).toBe(0)
  })

  it('should encode and decode utf8', () => {
    const str = 'hello✓'
    const encoded = encodeUtf8(str)
    expect(Array.isArray(encoded) || encoded instanceof Uint8Array).toBe(true)
    expect(decodeUtf8(encoded)).toBe(str)
  })

  it('should splice strings', () => {
    expect(splice('abcdef', 2, 2, 'XY')).toBe('abXYef')
    expect(splice('abcdef', 0, 3, 'Z')).toBe('Zdef')
    expect(splice('abcdef', 3, 0, 'Q')).toBe('abcQdef')
  })

  it('should encode utf8 via polyfill', () => {
    const bytes = _encodeUtf8Polyfill('hi✓')
    expect(bytes).toBeInstanceOf(Uint8Array)
    expect(decodeUtf8(bytes)).toBe('hi✓')
  })

  describe('polyfill paths via module reset', () => {
    afterEach(() => {
      vi.unstubAllGlobals()
      vi.resetModules()
    })

    it('uses polyfill when TextEncoder/TextDecoder unavailable', async () => {
      vi.stubGlobal('TextEncoder', undefined)
      vi.stubGlobal('TextDecoder', undefined)
      vi.resetModules()
      const mod = await import('./string')
      const encoded = mod.encodeUtf8('hello✓')
      expect(encoded).toBeInstanceOf(Uint8Array)
      expect(mod.decodeUtf8(encoded)).toBe('hello✓')
      expect(mod.getUtf8TextEncoder()).toBeNull()
    })

    it('decodes via polyfill for a large buffer', async () => {
      vi.stubGlobal('TextDecoder', undefined)
      vi.resetModules()
      const mod = await import('./string')
      const big = 'a'.repeat(15000)
      const bytes = new TextEncoder().encode(big)
      expect(mod.decodeUtf8(bytes)).toBe(big)
    })

    it('disables broken TextDecoder (Safari BOM workaround)', async () => {
      class FakeDecoder {
        decode() { return 'x' }
      }
      vi.stubGlobal('TextDecoder', FakeDecoder as any)
      vi.resetModules()
      const mod = await import('./string')
      expect(mod.getUtf8TextDecoder()).toBeNull()
    })
  })
})