const Matrices = {
    // A x A array of nulls; null-null relationships are omitted in chord diagram.
    createEmptyMatrix: (len) => {
        const empty = Array.apply(null, Array(len));
        return empty.map(() => empty.map(() => null));
    },

    // Identical structure of chord matrix but with { game, team }.
    buildMetaMatrix: (json, eventKey) => {
        const teams = json.tourneys[eventKey].teams;
        const matrix = Matrices.createEmptyMatrix(teams.length);

        json.tourneys[eventKey].games.forEach(g => {
            const i1 = teams.indexOf(g.t1);
            const i2 = teams.indexOf(g.t2);

            matrix[i1][i2] = { game: g, team: g.t1 };
            matrix[i2][i1] = { game: g, team: g.t2 };
        }, []);

        return matrix;
    },

    // Scalar data points (sum of goals scored).
    buildChordMatrix: (json, eventKey) => {
        const teams = json.tourneys[eventKey].teams;
        const matrix = Matrices.createEmptyMatrix(teams.length);

        json.tourneys[eventKey].games.forEach(g => {
            const i1 = teams.indexOf(g.t1);
            const i2 = teams.indexOf(g.t2);

            matrix[i1][i2] = g.s1 + g.se1 + g.sp1;
            matrix[i2][i1] = g.s2 + g.se2 + g.sp2;
        }, []);

        return matrix;
    },
};