import { describe, expect, it } from 'vitest'
import { describeConflict, describeCounts, describeUndo, totalChanges, type ChangeSet } from './history'

function changeSet(over: Partial<ChangeSet> = {}): ChangeSet {
  return {
    id: 1,
    gardenId: 1,
    actorId: 1,
    actorName: 'Steve',
    source: 'ui',
    summary: 'Did a thing',
    counts: [],
    createdAt: '2026-07-21T00:00:00Z',
    ...over,
  }
}

describe('describeCounts', () => {
  it('pluralizes per entity and names the operation', () => {
    const cs = changeSet({
      counts: [
        { entityType: 'planting', op: 'create', n: 3 },
        { entityType: 'object', op: 'update', n: 1 },
      ],
    })
    expect(describeCounts(cs)).toBe('3 plantings added, 1 bed changed')
  })

  it('says nothing rather than "0 changes"', () => {
    expect(describeCounts(changeSet())).toBe('')
    expect(describeCounts(changeSet({ counts: [{ entityType: 'object', op: 'create', n: 0 }] }))).toBe('')
  })
})

describe('describeConflict', () => {
  it('names the entity when it has a name', () => {
    expect(describeConflict({ entityType: 'object', entityId: 4, reason: 'changed', name: 'North Bed' })).toBe(
      '“North Bed” was edited since, so it was left alone',
    )
  })

  it('falls back to the entity kind when it has no name', () => {
    expect(describeConflict({ entityType: 'planting', entityId: 9, reason: 'missing' })).toBe(
      'that planting no longer exists',
    )
  })
})

describe('describeUndo', () => {
  const target = changeSet({ counts: [{ entityType: 'object', op: 'update', n: 3 }] })

  it('is a plain success when nothing conflicted', () => {
    const out = describeUndo(target, {
      changeSet: changeSet({ id: 2, counts: [{ entityType: 'object', op: 'update', n: 3 }] }),
      conflicts: [],
    })
    expect(out).toEqual({ tone: 'ok', message: 'Undone.' })
  })

  // The server answers 200 with a null change set when every revision was
  // already a no-op — reachable by undoing a creation whose object is gone.
  // Claiming "Undone." there reports work that didn't happen.
  it("doesn't claim to have undone a no-op", () => {
    const out = describeUndo(target, { changeSet: null, conflicts: [] })
    expect(out.tone).toBe('ok')
    expect(out.message).toBe('Nothing left to undo — this was already reversed.')
  })

  // The case the issue was specific about: a partial revert really did change
  // things, so reporting a bare failure would be a lie about what applied.
  it('says how much applied and what was skipped', () => {
    const out = describeUndo(target, {
      changeSet: changeSet({ id: 2, counts: [{ entityType: 'object', op: 'update', n: 2 }] }),
      conflicts: [{ entityType: 'object', entityId: 7, reason: 'changed', name: 'North Bed' }],
    })
    expect(out.tone).toBe('partial')
    expect(out.message).toBe('2 of 3 changes undone — “North Bed” was edited since, so it was left alone.')
  })

  it('is an error when nothing applied at all', () => {
    const out = describeUndo(target, {
      changeSet: null,
      conflicts: [{ entityType: 'object', entityId: 7, reason: 'changed', name: 'North Bed' }],
    })
    expect(out.tone).toBe('error')
    expect(out.message).toBe('Nothing was undone — “North Bed” was edited since, so it was left alone.')
  })

  it('lists every conflict, not just the first', () => {
    const out = describeUndo(target, {
      changeSet: changeSet({ id: 2, counts: [{ entityType: 'object', op: 'update', n: 1 }] }),
      conflicts: [
        { entityType: 'object', entityId: 7, reason: 'changed', name: 'North Bed' },
        { entityType: 'planting', entityId: 8, reason: 'missing' },
      ],
    })
    expect(out.message).toContain('“North Bed”')
    expect(out.message).toContain('that planting no longer exists')
  })
})

describe('totalChanges', () => {
  it('sums every tally', () => {
    expect(
      totalChanges(
        changeSet({
          counts: [
            { entityType: 'planting', op: 'create', n: 12 },
            { entityType: 'object', op: 'update', n: 1 },
          ],
        }),
      ),
    ).toBe(13)
  })
})

describe('describeUndo with an unknown total', () => {
  // The chat panel offers Undo on a turn knowing only its change set id — the
  // agent's reply carries the id, not the tally. Inventing a denominator to
  // fill the sentence would be worse than not having one.
  it("doesn't invent a denominator it was never given", () => {
    const out = describeUndo(
      { id: 5 },
      {
        changeSet: changeSet({ id: 6, counts: [{ entityType: 'planting', op: 'delete', n: 2 }] }),
        conflicts: [{ entityType: 'object', entityId: 7, reason: 'changed', name: 'North Bed' }],
      },
    )
    expect(out.tone).toBe('partial')
    expect(out.message).toBe('Partly undone — “North Bed” was edited since, so it was left alone.')
    expect(out.message).not.toMatch(/\d+ of \d+/)
  })

  it('still reports a clean undo the same way', () => {
    const out = describeUndo(
      { id: 5 },
      { changeSet: changeSet({ id: 6, counts: [{ entityType: 'object', op: 'update', n: 1 }] }), conflicts: [] },
    )
    expect(out).toEqual({ tone: 'ok', message: 'Undone.' })
  })
})