import { describe, expect, it } from 'vitest'
import {
  AGENT_TUI_CLEAR_INPUT_FORWARD,
  AGENT_TUI_CLEAR_INPUT_LINE,
  AGENT_TUI_CLEAR_INPUT_MAX,
  AGENT_TUI_CLEAR_LINE_SLACK,
  AGENT_TUI_CLEAR_MAX_LINES,
  buildAgentTuiClearInput,
  buildAgentTuiClearInputForText,
  countAgentTuiInputLines
} from './agent-tui-input-clear'

const countCtrlU = (bytes: string): number =>
  bytes.split('').filter((char) => char === AGENT_TUI_CLEAR_INPUT_LINE).length
const countCtrlK = (bytes: string): number =>
  bytes.split('').filter((char) => char === AGENT_TUI_CLEAR_INPUT_FORWARD).length

describe('buildAgentTuiClearInput', () => {
  // The measured law: N kills + (N-1) joins. A constant here silently under-clears
  // (5 clears 3 lines but leaves residue at 4), which is what glues onto the next
  // message — so pin every small N, not just one.
  it.each([
    [1, 1],
    [2, 3],
    [3, 5],
    [4, 7],
    [10, 19]
  ])('clears %i logical lines with %i Ctrl+U', (lines, expected) => {
    const clearInput = buildAgentTuiClearInput(lines)
    expect(countCtrlU(clearInput)).toBe(expected)
    expect(countCtrlK(clearInput)).toBe(expected)
  })

  it('clears before the cursor before clearing the suffix after it', () => {
    expect(buildAgentTuiClearInput(4)).toBe(
      AGENT_TUI_CLEAR_INPUT_LINE.repeat(7) + AGENT_TUI_CLEAR_INPUT_FORWARD.repeat(7)
    )
  })

  it('still clears one line for a zero or negative count', () => {
    expect(countCtrlU(buildAgentTuiClearInput(0))).toBe(1)
    expect(countCtrlU(buildAgentTuiClearInput(-5))).toBe(1)
  })

  it('caps the burst so a pathological draft cannot emit an unbounded write', () => {
    expect(countCtrlU(buildAgentTuiClearInput(10_000))).toBe(2 * AGENT_TUI_CLEAR_MAX_LINES - 1)
    expect(AGENT_TUI_CLEAR_INPUT_MAX).toBe(buildAgentTuiClearInput(AGENT_TUI_CLEAR_MAX_LINES))
  })
})

describe('countAgentTuiInputLines', () => {
  it.each([
    ['one line', 1],
    ['a\nb', 2],
    ['a\r\nb\r\nc', 3],
    ['a\rb', 2],
    ['trailing\n', 2]
  ])('counts %j as %i logical lines', (text, expected) => {
    expect(countAgentTuiInputLines(text)).toBe(expected)
  })

  it('ignores visual wrapping — only logical newlines cost a Ctrl+U', () => {
    expect(countAgentTuiInputLines('x'.repeat(5_000))).toBe(1)
  })
})

describe('buildAgentTuiClearInputForText', () => {
  it('sizes the burst from the text plus slack for TUI-side edits', () => {
    // The injected text is a LOWER bound: the user can type into the TUI line too.
    expect(countCtrlU(buildAgentTuiClearInputForText('a\nb'))).toBe(
      2 * (2 + AGENT_TUI_CLEAR_LINE_SLACK) - 1
    )
  })

  it('clears strictly more than the draft needs, never less', () => {
    const draft = 'Linked Linear issue: ABC-123\nhttps://linear.app/x/issue/ABC-123\n'
    expect(countCtrlU(buildAgentTuiClearInputForText(draft))).toBeGreaterThan(
      2 * countAgentTuiInputLines(draft) - 1
    )
  })

  it('a long wrapped single line does not inflate the burst', () => {
    expect(buildAgentTuiClearInputForText('y'.repeat(5_000))).toBe(
      buildAgentTuiClearInputForText('y')
    )
  })
})