/**
 * These methods display fetching data from a MySQL database.
 * Single row from main table and multiple rows from secondary tables.
 * All results are coupled together into an object before sending the response.
 *
 * Example response: {
 *      success: true,
 *      data: {
 *          name: 'IngredientName',
 *          description: 'IngredientDescription',
 *          photo: 'IngredientPhoto',
 *          category: 'IngredientCategory',
 *          allowedUnits: [...],
 *          allergents: [...],
 *          nutrients: [...]
 *      }
 * }
 *
 * Note: This was taken out of context for demonstational purposes therefore
 * some imports might be missing.
 */

function getIngredient(id) {
    return Promise.all([
        databaseService.singleQuery(`
                SELECT
                    ingredients.id AS id,
                    ingredients.name AS name,
                    ingredients.description AS description,
                    ingredients.photo AS photo,
                    categories.name AS category
                FROM ingredients
                LEFT JOIN ingredientCategories ON ingredientCategories.ingredientId = ingredients.id
                LEFT JOIN categories ON categories.id = ingredientCategories.categoryId
                WHERE ingredients.id = ${id}
            `),
        databaseService.query(`
                SELECT
                    units.id AS id,
                    units.shortName AS shortName,
                    units.longName AS longName
                FROM ingredientAllowedUnits
                LEFT JOIN units ON units.id = ingredientAllowedUnits.unitId
                WHERE ingredientId = ${id}
            `),
        databaseService.query(`
                SELECT
                    allergents.id AS id,
                    allergents.name AS name
                FROM ingredientAllergents
                LEFT JOIN allergents ON allergents.id = ingredientAllergents.allergentId
                WHERE ingredientId = ${id}
            `),
        databaseService.query(`
                SELECT
                    nutrients.id AS id,
                    nutrients.name AS name,
                    ingredientNutrients.value AS value
                FROM ingredientNutrients
                LEFT JOIN nutrients ON nutrients.id = ingredientNutrients.nutrientId
                WHERE ingredientId = ${id}
            `)
    ]);
}

async function getIngredientHook(request, response) {

    // Authenticate user (returns user object or null)
    const user = await authenticationService.checkUserSession(request, response);

    if (user) {

        // Check if ingredient id was succesfully passed in the url
        if (!request.params || !request.params.id) {
            response.send(responseService.formatResponseError('Ingredient ID is required!'));
            return;
        }

        const ingredientId = request.params.id;

        try {
            const ingredientData = await ingredientsService.getIngredient(ingredientId);

            // ingredientData[0].success && ingredient[0].data checks if initial ingredient query was succesful and returned a non-null response
            if (ingredientData && ingredientData[0].success && ingredientData[0].data) {

                // Ingredient query response (first) (returns object - single row)
                let ingredient = ingredientData[0].success ? ingredientData[0].data : {};

                // Allowed units query response (second) (returns array of objects - multiple rows)
                const allowedUnits = ingredientData[1].success ? ingredientData[1].data : [];

                // Allergents query response (third) (returns array of objects - multiple rows)
                const allergents = ingredientData[2].success ? ingredientData[2].data : [];

                // Nutrients query response (fourth) (returns array of objects - multiple rows)
                const nutrients = ingredientData[3].success ? ingredientData[3].data : [];

                // Combine query responses into an object (nicely formatted)
                ingredient = Object.assign(ingredient, { allowedUnits, allergents, nutrients });

                response.send(responseService.formatResponseData(ingredient));

            // If ingredientData[0].data is null then no rows have been found with the supplied ID
            } else if (ingredientData && !ingredientData[0].data) {
                response.send(responseService.formatResponseError(`Ingredient with id ${ingredientId} not found.`));

            // Return error in other cases
            } else {
                logger.error(ingredientData);
                response.send(responseService.formatResponseError('Error fetching ingredient, contact system administrator!'));
            }
        } catch (e) {
            logger.error(e);
            response.send(responseService.formatResponseError('Error fetching ingredient, contact system administrator!'));
        }
    }
};