thi-ng/umbrella

export const compress = (m: number, n: number, dense: ArrayLike<number>) => {
    const major: number[] = [0];
    const minor: number[] = [];
    const data: number[] = [];
    for (let i = 0, col = 0; col < n; col++) {
        let nnz = 0;
        for (let row = 0; row < m; i++, row++) {
            if (dense[i] !== 0) {
                data.push(dense[i]);
                minor.push(row);
                nnz++;
            }
        }
        major.push(major[major.length - 1] + nnz);
    }
    return [major, minor, data];
};

export const diag = (vals: number[]) => {
    const n = vals.length;
    const major: number[] = [];
    const minor: number[] = [];
    for (let i = 0; i < n; i++) {
        major.push(i);
        minor.push(i);
    }
    major.push(n);
    return [major, minor];
};

export const at = (
    id1: number,
    id2: number,
    major: number[],
    minor: number[],
    data: number[]
) => {
    const ii = major[id1 + 1];
    for (let i = major[id1]; i < ii; i++) {
        if (minor[i] === id2) {
            return data[i];
        }
    }
    return 0;
};

export const setAt = (
    id1: number,
    id2: number,
    id1max: number,
    val: number,
    major: number[],
    minor: number[],
    data: number[],
    compact = true
) => {
    const notZero = val !== 0;
    const ii = major[id1 + 1];
    for (let i = major[id1]; i < ii; i++) {
        const j = minor[i];
        if (j === id2) {
            if (notZero || !compact) {
                data[i] = val;
            } else {
                remove(id1, id1max, i, major, minor, data);
            }
            return [major, minor, data];
        } else if (j > id2 && notZero) {
            return insert(id1, id2, id1max, val, i, major, minor, data);
        }
    }
    if (notZero) {
        return insert(id1, id2, id1max, val, ii, major, minor, data);
    }
    return [major, minor, data];
};

export const insert = (
    id1: number,
    id2: number,
    id1max: number,
    x: number,
    idx: number,
    major: number[],
    minor: number[],
    data: number[]
) => {
    data = data.slice(0, idx).concat(x, data.slice(idx));
    minor = minor.slice(0, idx).concat(id2, minor.slice(idx));
    for (let i = id1 + 1; i <= id1max; i++) {
        major[i]++;
    }
    return [major, minor, data];
};

export const remove = (
    id1: number,
    id1max: number,
    idx: number,
    major: number[],
    minor: number[],
    data: number[]
) => {
    data.splice(idx, 1);
    minor.splice(idx, 1);
    for (let i = id1 + 1; i <= id1max; i++) {
        major[i]--;
    }
};