import { describe, expect, it } from 'vitest'
import { B2B_THRESHOLD_MIN, findB2BLinks, findB2BSides } from '@/lib/timetable/b2b'
import type { Performance } from '@/types/timetable'

function p(overrides: Partial<Performance> = {}): Performance {
  return {
    id: 'p1',
    engagement_id: 'e1',
    event_id: 'ev1',
    stage_id: 's1',
    lane: 0,
    lane_resolved: 0,
    start_at: '2026-07-10T18:00:00.000Z',
    end_at: '2026-07-10T19:00:00.000Z',
    version: 0,
    notes: null,
    warnings: [],
    created_at: null,
    updated_at: null,
    deleted_at: null,
    ...overrides,
  }
}

describe('findB2BLinks', () => {
  it('returns empty when no consecutive pair exists', () => {
    expect(findB2BLinks([p({ id: 'a' })])).toEqual([])
  })

  it('marks 0-min gap as B2B', () => {
    const links = findB2BLinks([
      p({ id: 'a', start_at: '2026-07-10T18:00:00Z', end_at: '2026-07-10T19:00:00Z' }),
      p({ id: 'b', start_at: '2026-07-10T19:00:00Z', end_at: '2026-07-10T20:00:00Z' }),
    ])

    expect(links).toHaveLength(1)
    expect(links[0]).toEqual({ leftId: 'a', rightId: 'b', gapMin: 0 })
  })

  it('marks 2:59 gap as B2B (under 3-min threshold)', () => {
    const links = findB2BLinks([
      p({ id: 'a', start_at: '2026-07-10T18:00:00Z', end_at: '2026-07-10T19:00:00Z' }),
      p({ id: 'b', start_at: '2026-07-10T19:02:59Z', end_at: '2026-07-10T20:00:00Z' }),
    ])

    expect(links).toHaveLength(1)
  })

  it('does NOT mark 3:01 gap as B2B', () => {
    const links = findB2BLinks([
      p({ id: 'a', start_at: '2026-07-10T18:00:00Z', end_at: '2026-07-10T19:00:00Z' }),
      p({ id: 'b', start_at: '2026-07-10T19:03:01Z', end_at: '2026-07-10T20:00:00Z' }),
    ])

    expect(links).toHaveLength(0)
  })

  it('overlap (negative gap) is NOT a B2B link', () => {
    const links = findB2BLinks([
      p({ id: 'a', start_at: '2026-07-10T18:00:00Z', end_at: '2026-07-10T19:00:00Z' }),
      p({ id: 'b', start_at: '2026-07-10T18:30:00Z', end_at: '2026-07-10T19:30:00Z' }),
    ])

    expect(links).toHaveLength(0)
  })

  it('threshold constant is 3 minutes', () => {
    expect(B2B_THRESHOLD_MIN).toBe(3)
  })
})

describe('findB2BSides', () => {
  it('produces left+right sets reflecting neighbour position', () => {
    const { leftSet, rightSet } = findB2BSides([
      p({ id: 'a', start_at: '2026-07-10T18:00:00Z', end_at: '2026-07-10T19:00:00Z' }),
      p({ id: 'b', start_at: '2026-07-10T19:00:00Z', end_at: '2026-07-10T20:00:00Z' }),
    ])

    expect(rightSet.has('a')).toBe(true)
    expect(leftSet.has('b')).toBe(true)
    expect(leftSet.has('a')).toBe(false)
    expect(rightSet.has('b')).toBe(false)
  })
})