import { sql } from "drizzle-orm";
import { messages } from "~~/drizzle/schema";
import { db } from "~~/server/lib/db";
import { topicEvents } from "~~/server/utils/events";

async function deeplyDeleteMessage(messageId: string, topicId: string, userId: string) {
    const children = await db.query.messages.findMany({
        where: {
            parentMessageId: messageId,
            userId,
        }
    } as any);

    for (const child of children) {
        await deeplyDeleteMessage(child.id, topicId, userId);
    }

    await db.delete(messages).where(sql`${messages.id} = ${messageId} AND ${messages.userId} = ${userId}`);

    topicEvents.emit(topicId, {
        type: 'MESSAGE_DELETED',
        payload: { id: messageId },
    });
}

export default defineEventHandler(async (event) => {
    await protectRoute(event);

    const userId = event.context.user!.id;
    const messageId = getRouterParam(event, 'messageId')!;

    const message = await db.query.messages.findFirst({
        where: {
            id: messageId,
            userId,
        }
    } as any);

    if (!message) {
        throw createError({
            statusCode: 400,
            statusMessage: 'Invalid message',
        });
    }

    const topicId = message.topicId;

    const allTopicMessages = await db.query.messages.findMany({
        where: {
            topicId,
            userId,
        },
        orderBy: {
            createdAt: 'asc',
        },
    });

    const messagesMap = new Map(allTopicMessages.map(m => [m.id, { ...m, children: [] as typeof m[] }]));

    for (const msg of messagesMap.values()) {
        if (msg.parentMessageId && messagesMap.has(msg.parentMessageId)) {
            messagesMap.get(msg.parentMessageId)!.children.push(msg);
        }
    }

    const targetMessage = messagesMap.get(messageId);
    if (!targetMessage) {
        throw createError({
            statusCode: 400,
            statusMessage: 'Invalid message',
        });
    }

    if (targetMessage.role === 'user') {
        await deeplyDeleteMessage(targetMessage.id, topicId, userId);
        return { ok: true };
    }

    if (targetMessage.parentMessageId && messagesMap.has(targetMessage.parentMessageId)) {
        const parent = messagesMap.get(targetMessage.parentMessageId)!;
        await deeplyDeleteMessage(targetMessage.id, topicId, userId);

        const remainingChildren = parent.children.filter((child) => {
            return child.id !== targetMessage.id;
        });

        if (parent.deleted === true && remainingChildren.length === 0) {
            await deeplyDeleteMessage(parent.id, topicId, userId);
        } else if (parent.activeChildId === targetMessage.id) {
            const nextActiveChildId = remainingChildren.length > 0
                ? (parent.deleted ? remainingChildren[0]!.id : remainingChildren[remainingChildren.length - 1]!.id)
                : null;
            await db.update(messages).set({ activeChildId: nextActiveChildId }).where(sql`${messages.id} = ${parent.id} AND ${messages.userId} = ${userId}`);
            topicEvents.emit(topicId, {
                type: 'MESSAGE_UPDATED',
                payload: { ...parent, activeChildId: nextActiveChildId },
            });
        }
        return { ok: true };
    }

    if (targetMessage.deleted === true) {
        const childMessage = targetMessage.activeChildId
            ? targetMessage.children.find((c) => { return c.id === targetMessage.activeChildId; })
            : targetMessage.children[0];

        if (childMessage) {
            await deeplyDeleteMessage(childMessage.id, topicId, userId);
            const remainingChildren = targetMessage.children.filter((child) => {
                return child.id !== childMessage.id;
            });
            if (remainingChildren.length === 0) {
                await deeplyDeleteMessage(targetMessage.id, topicId, userId);
            } else if (targetMessage.activeChildId === childMessage.id) {
                const nextActiveChildId = remainingChildren[0]!.id;
                await db.update(messages).set({ activeChildId: nextActiveChildId }).where(sql`${messages.id} = ${targetMessage.id} AND ${messages.userId} = ${userId}`);
                topicEvents.emit(topicId, {
                    type: 'MESSAGE_UPDATED',
                    payload: { ...targetMessage, activeChildId: nextActiveChildId },
                });
            }
        } else {
            await deeplyDeleteMessage(targetMessage.id, topicId, userId);
        }
        return { ok: true };
    }

    if (
        targetMessage.activeChildId
        && targetMessage.children.length > 0
    ) {
        const childMessage = targetMessage.children.find((c) => {
            return c.id === targetMessage.activeChildId;
        });
        if (childMessage) {
            await deeplyDeleteMessage(childMessage.id, topicId, userId);
            const remainingChildren = targetMessage.children.filter((child) => {
                return child.id !== childMessage.id;
            });
            const nextActiveChildId = remainingChildren.length > 0
                ? remainingChildren[remainingChildren.length - 1]!.id
                : null;
            await db.update(messages).set({ activeChildId: nextActiveChildId }).where(sql`${messages.id} = ${targetMessage.id} AND ${messages.userId} = ${userId}`);
            topicEvents.emit(topicId, {
                type: 'MESSAGE_UPDATED',
                payload: { ...targetMessage, activeChildId: nextActiveChildId },
            });
            return { ok: true };
        }
    }

    if (targetMessage.children.length === 0) {
        await deeplyDeleteMessage(targetMessage.id, topicId, userId);
        return { ok: true };
    }

    const nextActiveChildId = targetMessage.children[0]?.id ?? null;
    await db.update(messages).set({
        deleted: true,
        activeChildId: nextActiveChildId,
    }).where(sql`${messages.id} = ${targetMessage.id} AND ${messages.userId} = ${userId}`);

    topicEvents.emit(topicId, {
        type: 'MESSAGE_UPDATED',
        payload: { ...targetMessage, deleted: true, activeChildId: nextActiveChildId },
    });

    return { ok: true };
});