as-table/as-table.js

"use strict";

const O = Object
    , { first, strlen } = require ('printable-characters') // handles ANSI codes and invisible characters
    , limit = (s, n) => (first (s, n - 1) + '…')

const asColumns = (rows, cfg_) => {
    
    const

        zip = (arrs, f) => arrs.reduce ((a, b) => b.map ((b, i) => [...a[i] || [], b]), []).map (args => f (...args)),

    /*  Convert cell data to string (converting multiline text to singleline) */

        cells           = rows.map (r => r.map (c => c.replace (/\n/g, '\\n'))),

    /*  Compute column widths (per row) and max widths (per column)     */

        cellWidths      = cells.map (r => r.map (strlen)),
        maxWidths       = zip (cellWidths, Math.max),

    /*  Default config     */

        cfg             = O.assign ({
                            delimiter: '  ',
                            minColumnWidths: maxWidths.map (x => 0),
                            maxTotalWidth: 0 }, cfg_),

        delimiterLength = strlen (cfg.delimiter),

    /*  Project desired column widths, taking maxTotalWidth and minColumnWidths in account.     */

        totalWidth      = maxWidths.reduce ((a, b) => a + b, 0),
        relativeWidths  = maxWidths.map (w => w / totalWidth),
        maxTotalWidth   = cfg.maxTotalWidth - (delimiterLength * (maxWidths.length - 1)),
        excessWidth     = Math.max (0, totalWidth - maxTotalWidth),
        computedWidths  = zip ([cfg.minColumnWidths, maxWidths, relativeWidths],
                            (min, max, relative) => Math.max (min, Math.floor (max - excessWidth * relative))),

    /*  This is how many symbols we should pad or cut (per column).  */

        restCellWidths  = cellWidths.map (widths => zip ([computedWidths, widths], (a, b) => a - b))

    /*  Perform final composition.   */

        return zip ([cells, restCellWidths], (a, b) =>
                zip ([a, b], (str, w) => (w >= 0)
                                            ? (cfg.right ? (' '.repeat (w) + str) : (str + ' '.repeat (w)))
                                            : (limit (str, strlen (str) + w))).join (cfg.delimiter))
}

const asTable = cfg => O.assign (arr => {

/*  Print arrays  */

    if (arr[0] && Array.isArray (arr[0]))
        return asColumns (
            arr.map (
                r => r.map (
                    (c, i) => (c === undefined) ? '' : cfg.print(c, i)
                )
            ),
            cfg
        ).join ('\n')

/*  Print objects   */

    const colNames        = [...new Set ([].concat (...arr.map (O.keys)))],
          columns         = [
            colNames.map (cfg.title),
            ...arr.map (
                o => colNames.map (
                    key => (o[key] === undefined) ? '' : cfg.print(o[key], key)
                )
            )
          ],
          lines           = asColumns (columns, cfg)

    return [lines[0], cfg.dash.repeat (strlen (lines[0])), ...lines.slice (1)].join ('\n')

}, cfg, {

    configure: newConfig => asTable (O.assign ({}, cfg, newConfig)),
})

module.exports = asTable ({

    maxTotalWidth: Number.MAX_SAFE_INTEGER,
    print: String,
    title: String,
    dash: '-',
    right: false
})