// import {collection} from '../core/db'
// const {collection} = require('../core/db')
import {createMap} from '../utils/common'
import {getCollective} from './collective'

import {scheduleDate, getPeriod as schedulePeriod, getPeriodString} from '../models/schedule'
import {getCourse} from '../models/course'

const last = require('../lib/array').last
const sortBy = require('../lib/sort').sortBy

const SCHEDULES = 'schedules'

export async function findSchedule(collection, period, semester) {
	const schedule = await collection(SCHEDULES).findOne({
		$or: [
			{period: period},
			{period: schedulePeriod(period)}
		],
		semester: semester
	})

	return schedule ? migrate(schedule) : null
}

async function findAllScheduleParams() {
	const schedules = await collection(SCHEDULES)
		.find({}, {
			period: 1,
			semester: 1,
			_id: 0,
		})
		.toArray()

	return schedules
		.map(i => ({
			...i,
			period: schedulePeriod(i.period),
		}))
		.sort(sortBy(
			i => scheduleDate(i).getTime(),
			true,
		))
}

async function findDefaultScheduleParams() {
	const schedules = await findAllScheduleParams()
	return last(schedules
		.map(i => ({
			...i,
			period: getPeriodString(i.period),
		}))
	)
}

function text({semester, period}) {
	const word = semester => [['spring', 'Весна'], ['autumn', 'Осень']]
		.find(i => i[0] === semester)
		[1]
	const periodIndex = semester === 'spring' ? 1 : 0
	const year = period[periodIndex]

	return `${word(semester)} ${year} года`
}

async function migrate(schedule) {
	const versions = {
		'1.0': migrate10to20,
		'2.0': migrate20to30,
	}

	const version = schedule.version
	const update = versions[version]
	return version in versions ? migrate(update(schedule)) : schedule
}

function migrate10to20(schedule) {
	const dayNames = ['mon', 'tue', 'wed', 'thu', 'fri', 'sat', 'sun']
	const time = time => time
		.map(i => i.split(' '))

	const week = days => days.reduce((week, lesson, index) => {
		if (lesson) {
			const day = dayNames[index]
			week[day] = [Object.assign(lesson, {
				time: time(lesson.time)
			})]
		}

		return week
	}, {})

	return Object.assign(schedule, {
		version: '2.0',
		period: schedulePeriod(schedule.period),
		groups: schedule.schedule
			.map(group => ({
				name: group.group,
				time: group.time,
				week: week(group.week)
			}))
	})
}

async function migrate20to30(schedule) {
	const days = ['mon', 'tue', 'wed', 'thu', 'fri', 'sat']//, 'sun']

	const persons = await getCollective()
	const person = createMap(i => i.id, persons)

	const week = week => days
		.map(day => week[day] || [])
		.map(lessons => lessons.map(lesson))

	const lesson = i => ({
		time: i.time,
		course: getCourse(i.lesson),
		teacher: person.has(i.teacher) ? teacher(i.teacher) : teacherDummy(i.teacher)
	})

	const teacher = id => ({
		id: id,
		url: `/teacher/${id}`,
		name: personName(id)
	})

	const teacherDummy = name => ({
		id: name,
		url: null,
		name: name
	})

	const personName = id => person.has(id) ? person.get(id).name : null

	return Object.assign(schedule, {
		version: '3.0',
		groups: schedule.groups
			.map(group => ({
				name: group.name,
				time: group.time,
				week: week(group.week)
			}))
	})
}

// exports.findSchedule = findSchedule
// exports.findAllScheduleParams = findAllScheduleParams
// exports.findDefaultScheduleParams = findDefaultScheduleParams
// exports.text = text