japanese-srs-trainer-wanikani/server/src/services/wanikaniService.ts

import { ApiKeyModel } from '../models/apikey.model.ts'
import { AssignmentModel } from '../models/assignments.model.ts'
import { ReviewItemModel } from '../models/reviewitem.model.ts'

import type { KanjiItem, VocabularyItem } from '../types/wanikani.ts'

const WANIKANI_API_BASE = 'https://api.wanikani.com/v2'

export interface WaniKaniSubject {
	id: number
	object: string
	data: {
		characters: string
		meanings: { meaning: string; primary: boolean; accepted_answers: boolean }[]
		readings: { type: string; primary: boolean; accepted_answer: boolean; reading: string }[]
		auxiliary_meanings: { meaning: string; type: string }[]
		pronunciation_audios?: {
			url: string
			content_type: string
			metadata: { gender: string; pronunciation: string }[]
		}[]
		level: number
		slug: string
		unlocked_at?: string
		subject_type: 'kanji' | 'vocabulary' | 'kana_vocabulary'
	}
}

const fetchAllPages = async (
	url: string,
	headers: Record<string, string>,
): Promise<WaniKaniSubject[]> => {
	let results: WaniKaniSubject[] = []
	let nextUrl: string | null = url

	while (nextUrl) {
		const res = await fetch(nextUrl, { headers })
		if (!res.ok) throw new Error(`Failed fetching ${url}: ${res.statusText}`)
		const json = (await res.json()) as { data: WaniKaniSubject[]; pages: { next_url: string | null } }
		results = results.concat(json.data)
		nextUrl = json.pages.next_url
	}

	return results
}

const fetchSubjects = async (
	ids: number[],
	headers: Record<string, string>,
): Promise<WaniKaniSubject[]> => {
	const chunkSize = 1000
	let results: WaniKaniSubject[] = []

	for (let i = 0; i < ids.length; i += chunkSize) {
		const chunk = ids.slice(i, i + chunkSize)
		const res = await fetch(`${WANIKANI_API_BASE}/subjects?ids=${chunk.join(',')}`, { headers })
		if (!res.ok) throw new Error(`Failed fetching subjects: ${res.statusText}`)
		const json = (await res.json()) as { data: WaniKaniSubject[] }
		results = results.concat(json.data)
	}

	return results
}

const mapToReviewItem = (item: WaniKaniSubject, userId: string) => {
	let type: 'kanji' | 'vocab'
	const subjectType = item.data.subject_type || item.object
	if (subjectType === 'kanji') type = 'kanji'
	else if (['vocabulary', 'kana_vocabulary'].includes(subjectType)) type = 'vocab'
	else throw new Error(`Unknown WaniKani subject type: ${subjectType}`)

	return {
		id: item.id,
		userId,
		type,
		characters: item.data.characters,
		meanings: item.data.meanings,
		readings: item.data.readings ?? [],
		auxiliary_meanings: item.data.auxiliary_meanings ?? [],
		pronunciation_audios: item.data.pronunciation_audios ?? [],
		level: item.data.level,
		slug: item.data.slug,
		srs: {
			jp_en_meaning: {
				streak: 0,
				ease_factor: 2.5,
				interval: 1,
				next_review: new Date(),
				last_review: null,
			},
			jp_en_reading: {
				streak: 0,
				ease_factor: 2.5,
				interval: 1,
				next_review: new Date(),
				last_review: null,
			},
			en_jp_writing: {
				streak: 0,
				ease_factor: 2.5,
				interval: 1,
				next_review: new Date(),
				last_review: null,
			},
			writing_practice: {
				streak: 0,
				ease_factor: 2.5,
				interval: 1,
				next_review: new Date(),
				last_review: null,
			},
		},
	}
}

export const syncWanikaniData = async (apiKey: string, userId: string): Promise<void> => {
	const headers = { Authorization: `Bearer ${apiKey}` }

	try {
		await ApiKeyModel.updateOne(
			{},
			{ $set: { userId: userId, apiKey: apiKey, lastUsed: new Date() } },
			{ upsert: true },
		)

		const assignments = await fetchAllPages(`${WANIKANI_API_BASE}/assignments`, headers)

		const unlockedKanjiIds: number[] = []
		const unlockedVocabIds: number[] = []

		for (const a of assignments) {
			const assignmentData = a.data as any
			if (!assignmentData.unlocked_at) continue

			if (assignmentData.subject_type === 'kanji') unlockedKanjiIds.push(assignmentData.subject_id)
			else if (['vocabulary', 'kana_vocabulary'].includes(assignmentData.subject_type)) unlockedVocabIds.push(assignmentData.subject_id)
		}

		await AssignmentModel.updateOne(
			{ userId, subject_type: 'kanji' },
			{ $set: { subject_ids: unlockedKanjiIds } },
			{ upsert: true },
		)

		await AssignmentModel.updateOne(
			{ userId, subject_type: 'vocab' },
			{ $set: { subject_ids: unlockedVocabIds } },
			{ upsert: true },
		)

		// Fetch and insert new review items
		const kanjiSubjects = await fetchSubjects(unlockedKanjiIds, headers)
		const vocabSubjects = await fetchSubjects(unlockedVocabIds, headers)

		const allSlugs = new Set((await ReviewItemModel.find({ userId }, { slug: 1 })).map(r => r.slug))

		const newItems = [...kanjiSubjects, ...vocabSubjects]
			.filter(s => !allSlugs.has(s.data.slug))
			.map(s => mapToReviewItem(s, userId))

		if (newItems.length > 0) await ReviewItemModel.insertMany(newItems)

		console.log('✅ WaniKani sync complete')
	} catch (err) {
		console.error('❌ Error syncing WaniKani data:', err)
		throw err
	}
}