frontend/src/ui/call/streamTts.test.ts

/**
 * Unit tests for streamTts — the pluggable streaming TTS surface.
 * Anchored to § 5.3 of docs/analysis/voice-call-streaming-design.md.
 */
import { describe, it, expect } from 'vitest'
import { createStreamingTts, streamTtsInternals } from './streamTts'

const { splitIntoSentences, NullStreamTts } = streamTtsInternals

describe('splitIntoSentences', () => {
  it('splits on sentence enders followed by whitespace', () => {
    const { sentences, remainder } = splitIntoSentences(
      'hello there. how are you? fine! and you',
    )
    expect(sentences).toEqual([
      'hello there.',
      'how are you?',
      'fine!',
    ])
    expect(remainder).toBe('and you')
  })

  it('keeps partial trailing text as remainder', () => {
    const { sentences, remainder } = splitIntoSentences('partial sentence')
    expect(sentences).toEqual([])
    expect(remainder).toBe('partial sentence')
  })

  it('is safe on empty input', () => {
    const { sentences, remainder } = splitIntoSentences('')
    expect(sentences).toEqual([])
    expect(remainder).toBe('')
  })

  it('splits on newlines + semicolons', () => {
    const { sentences, remainder } = splitIntoSentences(
      'one thing;\n another thing.\n tail',
    )
    // Exact count + order matters so regressions are obvious.
    expect(sentences.length).toBeGreaterThanOrEqual(2)
    expect(sentences[0]).toContain('one thing')
    expect(remainder.trim()).toBe('tail')
  })
})

describe('NullStreamTts fallback', () => {
  it('is safe to call every method; never claims to be speaking', () => {
    const tts = new NullStreamTts()
    expect(tts.isSpeaking).toBe(false)
    tts.appendDelta('hello')
    tts.flush()
    tts.stop()
    expect(tts.isSpeaking).toBe(false)
  })
})

describe('createStreamingTts factory', () => {
  it('returns an object implementing the StreamingTts contract', () => {
    const tts = createStreamingTts()
    expect(typeof tts.appendDelta).toBe('function')
    expect(typeof tts.flush).toBe('function')
    expect(typeof tts.stop).toBe('function')
    expect(typeof tts.isSpeaking).toBe('boolean')
  })
})