import { describe, expect, it } from 'bun:test'
import { diffHunks, diffLines } from './diff.ts'

const lines = (rows: ReturnType<typeof diffLines>) => rows.map((r) => `${r.kind}:${r.text}`)

describe('行级 diff', () => {
  it('相同的内容全是 same，折叠后没有片段', () => {
    const rows = diffLines('a\nb\nc', 'a\nb\nc')
    expect(rows.every((r) => r.kind === 'same')).toBe(true)
    expect(diffHunks(rows)).toEqual([])
  })

  it('中间插入一行', () => {
    expect(lines(diffLines('a\nc', 'a\nb\nc'))).toEqual(['same:a', 'add:b', 'same:c'])
  })

  it('中间删除一行', () => {
    expect(lines(diffLines('a\nb\nc', 'a\nc'))).toEqual(['same:a', 'del:b', 'same:c'])
  })

  it('改一行等于删旧行加新行', () => {
    expect(lines(diffLines('a\nx\nc', 'a\ny\nc'))).toEqual(['same:a', 'del:x', 'add:y', 'same:c'])
  })

  it('从空到有、从有到空', () => {
    expect(lines(diffLines('', 'a'))).toEqual(['del:', 'add:a'])
    expect(lines(diffLines('a\nb', ''))).toEqual(['del:a', 'del:b', 'add:'])
  })

  it('公共前后缀之外的多处改动都找得到', () => {
    const before = ['p1', 'p2', 'x', 'm', 'y', 's1'].join('\n')
    const after = ['p1', 'p2', 'x2', 'm', 'y2', 's1'].join('\n')
    expect(lines(diffLines(before, after))).toEqual([
      'same:p1',
      'same:p2',
      'del:x',
      'add:x2',
      'same:m',
      'del:y',
      'add:y2',
      'same:s1',
    ])
  })
})

describe('折叠成片段', () => {
  it('改动行带前后上下文，远处的未改动行不进片段', () => {
    const rows = diffLines(
      ['1', '2', '3', '4', '5', '6', '7', '8', '9'].join('\n'),
      ['1', '2', '3', 'x', '5', '6', '7', '8', '9'].join('\n'),
    )
    const hunks = diffHunks(rows, 1)
    expect(hunks).toHaveLength(1)
    expect(hunks[0]!.map((r) => r.text)).toEqual(['3', '4', 'x', '5'])
  })

  it('相距很远的两处改动分成两个片段，挨得近就合并成一个', () => {
    const before = ['a', '1', '2', '3', '4', '5', '6', '7', 'b'].join('\n')
    const afterFar = ['a2', '1', '2', '3', '4', '5', '6', '7', 'b2'].join('\n')
    expect(diffHunks(diffLines(before, afterFar), 1)).toHaveLength(2)
    const afterNear = ['a2', '1', '2', '3', '4', '5', '6', '7b', 'b'].join('\n')
    expect(diffHunks(diffLines(before, afterNear), 4)).toHaveLength(1)
  })
})