const ParameterizedSQL = require('loopback-connector').ParameterizedSQL;

module.exports = Self => {
    Self.remoteMethod('getLeaves', {
        description: 'Returns the first shipped and landed possible for params',
        accessType: '',
        accepts: [{
            arg: 'parentFk',
            type: 'Number',
            default: 1,
            required: false,
        },
        {
            arg: 'filter',
            type: 'Object',
            description: 'Filter defining where, order, offset, and limit - must be a JSON-encoded string',
            http: {source: 'query'}
        }],
        returns: {
            type: ['object'],
            root: true
        },
        http: {
            path: `/getLeaves`,
            verb: 'GET'
        }
    });

    Self.getLeaves = async(parentFk = 1, filter) => {
        let conn = Self.dataSource.connector;
        let stmt = new ParameterizedSQL(
            `SELECT 
                child.id,
                child.name,
                child.lft,
                child.rgt,
                child.depth,
                child.sons
            FROM department parent 
                JOIN department child ON child.lft > parent.lft 
                    AND child.rgt < parent.rgt
                    AND child.depth = parent.depth + 1
                WHERE parent.id = ?`, [parentFk]);

        // Get nodes from depth greather than Origin
        stmt.merge(conn.makeSuffix(filter));

        const nodes = await Self.rawStmt(stmt);

        if (nodes.length == 0)
            return nodes;

        // Get parent nodes
        const minorDepth = nodes.reduce((a, b) => {
            return b < a ? b : a;
        }).depth;

        const parentNodes = nodes.filter(element => {
            return element.depth === minorDepth;
        });
        const leaves = Object.assign([], parentNodes);

        nestLeaves(leaves);

        function nestLeaves(elements) {
            elements.forEach(element => {
                let childs = Object.assign([], getLeaves(element));
                if (childs.length > 0) {
                    element.childs = childs;
                    nestLeaves(element.childs);
                }
            });
        }

        function getLeaves(parent) {
            let elements = nodes.filter(element => {
                return element.lft > parent.lft && element.rgt < parent.rgt
                    && element.depth === parent.depth + 1;
            });

            return elements;
        }

        return leaves;
    };
};