thebespokepixel/truwrap

/* eslint unicorn/prefer-trim-start-end:0,unicorn/prefer-string-slice:0 */
/* ─────────────────────╮
 │ truwrap line fitting │
 ╰──────────────────────┴────────────────────────────────────────────────────── */

import ansiRegex from 'ansi-regex'

const newlineRegex = /^>\/\\\/\/__<$/
const tabRegex = /^>T\/\\B<$/

/**
 * Fit a line of text to settings
 * @private
 */
class LineFitter {
    /**
     * Create a LineFitter instance
     * @param  {number[]} options [margin, width, tab-width] as an array.
     */
    constructor(options) {
        [
            this.mode,
            this.margin,
            this.desiredWidth,
            this.tabWidth,
        ] = options

        this.lineTokens = [this.margin]
        this.cursor = 0
        this.lineBlock = false
    }

    /**
     * Add a [TAB] character token to the line.
     * @return {string} Tab -> n-spaces.
     */
    createTab() {
        const width = this.tabWidth - (this.cursor % this.tabWidth) || 4
        this.cursor += width
        return ' '.repeat(width)
    }

    /**
     * Add a token to the line.
     * @param {string} token The word token to add.
     * @returns {boolean} Causes newline.
     */
    add(token) {
        if (newlineRegex.test(token)) {
            return true
        }

        if (ansiRegex().test(token)) {
            this.lineTokens.push(token)
            return false
        }

        if (tabRegex.test(token)) {
            this.lineTokens.push(this.createTab())
            return false
        }

        const overlap = this.cursor + token.trimEnd().length - this.desiredWidth

        switch (this.mode) {
            case 'hard':
                if (overlap > 0) {
                    const head = token.trimEnd().substring(0, token.length - overlap)
                    const tail = token.substring(token.length - overlap)
                    this.lineTokens.push(head)
                    this.cursor += head.length
                    return tail === ' ' ? '' : tail
                }

                this.lineTokens.push(token)
                this.cursor += token.length
                return false

            case 'keep':
                this.lineTokens.push(token)
                this.cursor += token.length
                return false

            default:
                if (overlap > 0 && this.cursor > 0) {
                    return token
                }

                this.lineTokens.push(token)
                this.cursor += token.length
                return false
        }
    }

    /**
     * Return a string of the current line.
     * @return {string} The current line.
     */
    toString() {
        return this.lineTokens.join('')
    }
}

/**
 * Creates a line fitter - a new line of wrapped text..
 * @private
 * @param      {string}      mode      The wrapping mode
 * @param      {string}      margin    The left margin, made up of spaces
 * @param      {number}      width     The width the line can take up
 * @param      {number}      tabWidth  Desired TAB width
 * @return     {LineFitter}  The line fitter.
 */
export default function createLineFitter(mode, margin, width, tabWidth) {
    return new LineFitter([mode, margin, width, tabWidth])
}