import { Not, In, IsNull } from "typeorm";
import { maximum } from "@/prelude/array.js";
import { Notes, Users } from "@/models/index.js";
import define from "../../define.js";
import { ApiError } from "../../error.js";
import { getUser } from "../../common/getters.js";

export const meta = {
	tags: ["users"],

	requireCredential: false,
	requireCredentialPrivateMode: true,

	description:
		"Get a list of other users that the specified user frequently replies to.",

	res: {
		type: "array",
		optional: false,
		nullable: false,
		items: {
			type: "object",
			optional: false,
			nullable: false,
			properties: {
				user: {
					type: "object",
					optional: false,
					nullable: false,
					ref: "UserDetailed",
				},
				weight: {
					type: "number",
					optional: false,
					nullable: false,
				},
			},
		},
	},

	errors: {
		noSuchUser: {
			message: "No such user.",
			code: "NO_SUCH_USER",
			id: "e6965129-7b2a-40a4-bae2-cd84cd434822",
		},
	},
} as const;

export const paramDef = {
	type: "object",
	properties: {
		userId: { type: "string", format: "misskey:id" },
		limit: { type: "integer", minimum: 1, maximum: 100, default: 10 },
	},
	required: ["userId"],
} as const;

export default define(meta, paramDef, async (ps, me) => {
	// Lookup user
	const user = await getUser(ps.userId).catch((e) => {
		if (e.id === "15348ddd-432d-49c2-8a5a-8069753becff")
			throw new ApiError(meta.errors.noSuchUser);
		throw e;
	});

	// Fetch recent notes
	const recentNotes = await Notes.find({
		where: {
			userId: user.id,
			replyId: Not(IsNull()),
		},
		order: {
			id: -1,
		},
		take: 1000,
		select: ["replyId"],
	});

	// 投稿が少なかったら中断
	if (recentNotes.length === 0) {
		return [];
	}

	// TODO ミュートを考慮
	const replyTargetNotes = await Notes.find({
		where: {
			id: In(recentNotes.map((p) => p.replyId)),
		},
		select: ["userId"],
	});

	const repliedUsers: any = {};

	// Extract replies from recent notes
	for (const userId of replyTargetNotes.map((x) => x.userId.toString())) {
		if (repliedUsers[userId]) {
			repliedUsers[userId]++;
		} else {
			repliedUsers[userId] = 1;
		}
	}

	// Calc peak
	const peak = maximum(Object.values(repliedUsers));

	// Sort replies by frequency
	const repliedUsersSorted = Object.keys(repliedUsers).sort(
		(a, b) => repliedUsers[b] - repliedUsers[a],
	);

	// Extract top replied users
	const topRepliedUsers = repliedUsersSorted.slice(0, ps.limit);

	// Make replies object (includes weights)
	const repliesObj = await Promise.all(
		topRepliedUsers.map(async (user) => ({
			user: await Users.pack(user, me, { detail: true }),
			weight: repliedUsers[user] / peak,
		})),
	);

	return repliesObj;
});
