// src/services/recommenderService.js
import { DECAY_RATE } from '../config/constants.js';
import { fetchAllArticles } from './fetchService.js'; // 新規記事取得
/**
* 指数関数的減衰（単位：日）
* - DECAY_RATE は「1日あたりの減衰率」を想定
*/
function decay(publishedAt) {
if (!publishedAt) return 0.5;
let publishedDate;
if (typeof publishedAt === 'string' && publishedAt.includes('年')) {
const normalized = publishedAt
.replace(/年/g, '-')
.replace(/月/g, '-')
.replace(/日/g, '');
publishedDate = new Date(normalized);
} else {
publishedDate = new Date(publishedAt);
}
if (isNaN(publishedDate.getTime())) {
console.warn('Invalid date format:', publishedAt);
return 0.5;
}
const ageDays =
(Date.now() - publishedDate.getTime()) / (1000 * 60 * 60 * 24);
return Math.exp(-DECAY_RATE * ageDays);
}
/**
* 読了×評価×タグ だけで重みマップを作成
*/
async function buildTagWeights(storage) {
const readArticles = await storage.listByStatus('読了', 100);
const weights = {};
for (const a of readArticles) {
// rating が 0 または undefined の場合はスキップ
if (!a.rating) continue;
for (const t of a.tags) {
weights[t] = (weights[t] || 0) + a.rating;
}
}
return weights;
}
/**
* 新規記事をタグ重み×減衰 または 新着度 でスコア化して推薦
* - 未読/ストック済記事は対象外
*/
export async function getRecommendations({ limit = 10 } = {}, { storage }) {
// ① 読了×評価×タグ で重みマップを構築
const tagWeights = await buildTagWeights(storage);
// ② 外部ソースから新規記事を取得
const allArticles = await fetchAllArticles();
const existsChecks = await Promise.all(
allArticles.map((art) =>
storage.findByUrlOrHash({ url: art.url, hash: art.hash })
)
);
const newArticles = allArticles.filter((_, i) => !existsChecks[i]);
// ③ 新規記事にスコアを付与
const scored = newArticles.map((a) => {
const tagScore = a.tags.reduce((sum, t) => sum + (tagWeights[t] || 0), 0);
const decayValue = decay(a.publishedAt);
// タグ適合度があればそれに減衰を掛け、なければ純粋な新着度をスコアに
const score = tagScore > 0 ? tagScore * decayValue : decayValue;
const reason =
tagScore > 0
? `タグ適合度 ${score.toFixed(1)}`
: `新着度 ${score.toFixed(2)}`;
return {
...a,
score: isNaN(score) ? 0 : score,
reason,
};
});
// ④ スコア順ソート＋上位 limit 件を返却
scored.sort((a, b) => b.score - a.score);
return scored.slice(0, limit);
}
