import { getUserIdFromSession } from '../../../utils/auth';
import { VILLAGE_GRID_SIZE, MOVE_COST, isCropGrown } from '../../../utils/village';

// --- Handler ---
export default defineEventHandler(async (event) => {
    const userId = await getUserIdFromSession(event);
    const objectId = parseInt(event.context.params?.id || '', 10);
    const { x, y } = await readBody(event);

    // 1. --- Validation ---
    if (isNaN(objectId)) {
        throw createError({ statusCode: 400, statusMessage: 'Invalid object ID.' });
    }
    if (typeof x !== 'number' || typeof y !== 'number') {
        throw createError({ statusCode: 400, statusMessage: 'Invalid request body. "x" and "y" are required.' });
    }
    if (x < 0 || x >= VILLAGE_GRID_SIZE.width || y < 0 || y >= VILLAGE_GRID_SIZE.height) {
        throw createError({ statusCode: 400, statusMessage: 'Cannot move object outside of village bounds.' });
    }

    // 2. --- Fetch state and enforce rules ---
    const village = await prisma.village.findUnique({
        where: { userId },
        include: { objects: true },
    });

    if (!village) {
        throw createError({ statusCode: 404, statusMessage: 'Village not found.' });
    }

    const objectToMove = village.objects.find(obj => obj.id === objectId);

    // Rule: Object must exist and belong to the user (implicit via village)
    if (!objectToMove) {
        throw createError({ statusCode: 404, statusMessage: 'Object not found.' });
    }

    // Rule: Cannot move obstacles
    if (objectToMove.type === 'OBSTACLE') {
        throw createError({ statusCode: 400, statusMessage: 'Cannot move obstacles. They must be cleared.' });
    }

    // Rule: Target cell must be empty (and not the same cell)
    if (village.objects.some(obj => obj.x === x && obj.y === y)) {
        throw createError({ statusCode: 409, statusMessage: 'Target cell is already occupied.' });
    }

    // 3. --- Perform atomic transaction ---
    try {
        const [, updatedObject] = await prisma.$transaction([
            prisma.user.update({
                where: { id: userId, coins: { gte: MOVE_COST } },
                data: { coins: { decrement: MOVE_COST } },
            }),
            prisma.villageObject.update({
                where: { id: objectId },
                data: { x, y },
            }),
        ]);

        return {
            id: updatedObject.id,
            type: updatedObject.type,
            x: updatedObject.x,
            y: updatedObject.y,
            cropType: updatedObject.cropType,
            isGrown: isCropGrown(updatedObject.plantedAt, updatedObject.cropType),
        };

    } catch (e) {
        throw createError({ statusCode: 402, statusMessage: 'Insufficient coins to move object.' });
    }
});