lua-in-js/src/lib/string.ts

import { sprintf } from 'printj'
import { Table } from '../Table'
import { LuaError } from '../LuaError'
import {
    coerceArgToBoolean,
    coerceArgToNumber,
    coerceArgToString,
    hasOwnProperty,
    LuaType,
    posrelat,
    tostring
} from '../utils'

const ROSETTA_STONE: Record<string, string> = {
    '([^a-zA-Z0-9%(])-': '$1*?',
    '([^%])-([^a-zA-Z0-9?])': '$1*?$2',
    '([^%])\\.': '$1[\\s\\S]',
    '(.)-$': '$1*?',
    '%a': '[a-zA-Z]',
    '%A': '[^a-zA-Z]',
    '%c': '[\x00-\x1f]',
    '%C': '[^\x00-\x1f]',
    '%d': '\\d',
    '%D': '[^d]',
    '%l': '[a-z]',
    '%L': '[^a-z]',
    '%p': '[.,"\'?!;:#$%&()*+-/<>=@\\[\\]\\\\^_{}|~]',
    '%P': '[^.,"\'?!;:#$%&()*+-/<>=@\\[\\]\\\\^_{}|~]',
    '%s': '[ \\t\\n\\f\\v\\r]',
    '%S': '[^ \t\n\f\v\r]',
    '%u': '[A-Z]',
    '%U': '[^A-Z]',
    '%w': '[a-zA-Z0-9]',
    '%W': '[^a-zA-Z0-9]',
    '%x': '[a-fA-F0-9]',
    '%X': '[^a-fA-F0-9]',
    '%([^a-zA-Z])': '\\$1'
}

function translatePattern(pattern: string): string {
    // TODO Add support for balanced character matching (not sure this is easily achieveable).

    // Replace single backslash with double backslashes
    let tPattern = pattern.replace(/\\/g, '\\\\')

    for (const i in ROSETTA_STONE) {
        if (hasOwnProperty(ROSETTA_STONE, i)) {
            tPattern = tPattern.replace(new RegExp(i, 'g'), ROSETTA_STONE[i])
        }
    }

    let nestingLevel = 0

    for (let i = 0, l = tPattern.length; i < l; i++) {
        if (i && tPattern.substr(i - 1, 1) === '\\') {
            continue
        }

        // Remove nested square brackets caused by substitutions
        const character = tPattern.substr(i, 1)

        if (character === '[' || character === ']') {
            if (character === ']') {
                nestingLevel -= 1
            }

            if (nestingLevel > 0) {
                tPattern = tPattern.substr(0, i) + tPattern.substr(i + 1)
                i -= 1
                l -= 1
            }

            if (character === '[') {
                nestingLevel += 1
            }
        }
    }

    return tPattern
}

/**
 * Returns the internal numeric codes of the characters s[i], s[i+1], ..., s[j].
 * The default value for i is 1; the default value for j is i.
 * These indices are corrected following the same rules of function string.sub.
 *
 * Numeric codes are not necessarily portable across platforms.
 */
function byte(s: LuaType, i: LuaType, j: LuaType): number[] {
    const S = coerceArgToString(s, 'byte', 1)
    const I = i === undefined ? 1 : coerceArgToNumber(i, 'byte', 2)
    const J = j === undefined ? I : coerceArgToNumber(j, 'byte', 3)

    return S.substring(I - 1, J)
        .split('')
        .map(c => c.charCodeAt(0))
}

/**
 * Receives zero or more integers. Returns a string with length equal to the number of arguments,
 * in which each character has the internal numeric code equal to its corresponding argument.
 *
 * Numeric codes are not necessarily portable across platforms.
 */
function char(...bytes: LuaType[]): string {
    return bytes
        .map((b, i) => {
            const B = coerceArgToNumber(b, 'char', i)
            return String.fromCharCode(B)
        })
        .join('')
}

/**
 * Looks for the first match of pattern (see §6.4.1) in the string s. If it finds a match, then find returns
 * the indices of s where this occurrence starts and ends; otherwise, it returns nil.
 * A third, optional numeric argument init specifies where to start the search; its default value is 1 and can be negative.
 * A value of true as a fourth, optional argument plain turns off the pattern matching facilities,
 * so the function does a plain "find substring" operation, with no characters in pattern being considered magic.
 * Note that if plain is given, then init must be given as well.
 *
 * If the pattern has captures, then in a successful match the captured values are also returned, after the two indices.
 */
function find(s: LuaType, pattern: LuaType, init: LuaType, plain: LuaType): (number | string)[] {
    const S = coerceArgToString(s, 'find', 1)
    const P = coerceArgToString(pattern, 'find', 2)
    const INIT = init === undefined ? 1 : coerceArgToNumber(init, 'find', 3)
    const PLAIN = plain === undefined ? false : coerceArgToBoolean(plain, 'find', 4)

    // Regex
    if (!PLAIN) {
        const regex = new RegExp(translatePattern(P))
        const index = S.substr(INIT - 1).search(regex)

        if (index < 0) return

        const match = S.substr(INIT - 1).match(regex)
        const result = [index + INIT, index + INIT + match[0].length - 1]

        match.shift()
        return [...result, ...match]
    }

    // Plain
    const index = S.indexOf(P, INIT - 1)
    return index === -1 ? undefined : [index + 1, index + P.length]
}

function format(formatstring: string, ...args: LuaType[]): string {
    // Pattern with all constraints:
    // /%%|%([-+ #0]{0,5})?(\d{0,2})?(?:\.(\d{0,2}))?([AEGXacdefgioqsux])/g
    const PATTERN = /%%|%([-+ #0]*)?(\d*)?(?:\.(\d*))?(.)/g

    let i = -1
    return formatstring.replace(PATTERN, (format, flags, width, precision, modifier) => {
        if (format === '%%') return '%'
        if (!modifier.match(/[AEGXacdefgioqsux]/)) {
            throw new LuaError(`invalid option '%${format}' to 'format'`)
        }
        if (flags && flags.length > 5) {
            throw new LuaError(`invalid format (repeated flags)`)
        }
        if (width && width.length > 2) {
            throw new LuaError(`invalid format (width too long)`)
        }
        if (precision && precision.length > 2) {
            throw new LuaError(`invalid format (precision too long)`)
        }

        i += 1
        const arg = args[i]
        if (arg === undefined) {
            throw new LuaError(`bad argument #${i} to 'format' (no value)`)
        }
        if (/A|a|E|e|f|G|g/.test(modifier)) {
            return sprintf(format, coerceArgToNumber(arg, 'format', i))
        }
        if (/c|d|i|o|u|X|x/.test(modifier)) {
            return sprintf(format, coerceArgToNumber(arg, 'format', i))
        }

        if (modifier === 'q') {
            return `"${(arg as string).replace(/([\n"])/g, '\\$1')}"`
        }
        if (modifier === 's') {
            return sprintf(format, tostring(arg))
        }
        return sprintf(format, arg)
    })
}

/**
 * Returns an iterator function that, each time it is called, returns the next captures from pattern (see §6.4.1)
 * over the string s. If pattern specifies no captures, then the whole match is produced in each call.
 */
function gmatch(s: LuaType, pattern: LuaType): () => string[] {
    const S = coerceArgToString(s, 'gmatch', 1)
    const P = translatePattern(coerceArgToString(pattern, 'gmatch', 2))

    const reg = new RegExp(P, 'g')
    const matches = S.match(reg)

    return () => {
        const match = matches.shift()
        if (match === undefined) return []

        const groups = new RegExp(P).exec(match)
        groups.shift()
        return groups.length ? groups : [match]
    }
}

/**
 * Returns a copy of s in which all (or the first n, if given) occurrences of the pattern (see §6.4.1)
 * have been replaced by a replacement string specified by repl, which can be a string, a table, or a function.
 * gsub also returns, as its second value, the total number of matches that occurred.
 * The name gsub comes from Global SUBstitution.
 *
 * If repl is a string, then its value is used for replacement. The character % works as an escape character:
 * any sequence in repl of the form %d, with d between 1 and 9, stands for the value of the d-th captured substring.
 * The sequence %0 stands for the whole match. The sequence %% stands for a single %.
 *
 * If repl is a table, then the table is queried for every match, using the first capture as the key.
 *
 * If repl is a function, then this function is called every time a match occurs,
 * with all captured substrings passed as arguments, in order.
 *
 * In any case, if the pattern specifies no captures, then it behaves as if the whole pattern was inside a capture.
 *
 * If the value returned by the table query or by the function call is a string or a number,
 * then it is used as the replacement string; otherwise, if it is false or nil, then there is no replacement
 * (that is, the original match is kept in the string).
 */
function gsub(s: LuaType, pattern: LuaType, repl: LuaType, n?: LuaType): string {
    let S = coerceArgToString(s, 'gsub', 1)
    const N = n === undefined ? Infinity : coerceArgToNumber(n, 'gsub', 3)
    const P = translatePattern(coerceArgToString(pattern, 'gsub', 2))

    const REPL = ((): ((strs: string[]) => string) => {
        if (typeof repl === 'function')
            return strs => {
                const ret = repl(strs[0])[0]
                return ret === undefined ? strs[0] : ret
            }

        if (repl instanceof Table) return strs => repl.get(strs[0]).toString()

        return strs => `${repl}`.replace(/%([0-9])/g, (_, i) => strs[i])
    })()

    let result = ''
    let count = 0
    let match
    let lastMatch
    while (count < N && S && (match = S.match(P))) {
        const prefix =
            // eslint-disable-next-line no-nested-ternary
            match[0].length > 0 ? S.substr(0, match.index) : lastMatch === undefined ? '' : S.substr(0, 1)

        lastMatch = match[0]
        result += `${prefix}${REPL(match)}`
        S = S.substr(`${prefix}${lastMatch}`.length)

        count += 1
    }

    return `${result}${S}`
}

/**
 * Receives a string and returns its length. The empty string "" has length 0.
 * Embedded zeros are counted, so "a\000bc\000" has length 5.
 */
function len(s: LuaType): number {
    const str = coerceArgToString(s, 'len', 1)
    return str.length
}

/**
 * Receives a string and returns a copy of this string with all uppercase letters changed to lowercase.
 * All other characters are left unchanged.
 * The definition of what an uppercase letter is depends on the current locale.
 */
function lower(s: LuaType): string {
    const str = coerceArgToString(s, 'lower', 1)
    return str.toLowerCase()
}

/**
 * Looks for the first match of pattern (see §6.4.1) in the string s.
 * If it finds one, then match returns the captures from the pattern; otherwise it returns nil.
 * If pattern specifies no captures, then the whole match is returned.
 * A third, optional numeric argument init specifies where to start the search; its default value is 1 and can be negative.
 */
function match(s: LuaType, pattern: LuaType, init: LuaType = 0): string | RegExpMatchArray {
    let str = coerceArgToString(s, 'match', 1)
    const patt = coerceArgToString(pattern, 'match', 2)
    const ini = coerceArgToNumber(init, 'match', 3)

    str = str.substr(ini)
    const matches = str.match(new RegExp(translatePattern(patt)))

    if (!matches) {
        return
    } else if (!matches[1]) {
        return matches[0]
    }

    matches.shift()
    return matches
}

/**
 * Returns a string that is the concatenation of n copies of the string s separated by the string sep.
 * The default value for sep is the empty string (that is, no separator).
 * Returns the empty string if n is not positive.
 */
function rep(s: LuaType, n: LuaType, sep?: LuaType): string {
    const str = coerceArgToString(s, 'rep', 1)
    const num = coerceArgToNumber(n, 'rep', 2)
    const SEP = sep === undefined ? '' : coerceArgToString(sep, 'rep', 3)
    return Array(num)
        .fill(str)
        .join(SEP)
}

/** Returns a string that is the string s reversed. */
function reverse(s: LuaType): string {
    const str = coerceArgToString(s, 'reverse', 1)
    return str
        .split('')
        .reverse()
        .join('')
}

/**
 * Returns the substring of s that starts at i and continues until j; i and j can be negative.
 * If j is absent, then it is assumed to be equal to -1 (which is the same as the string length).
 * In particular, the call string.sub(s,1,j) returns a prefix of s with length j, and string.sub(s, -i)
 * (for a positive j) returns a suffix of s with length i.
 *
 * If, after the translation of negative indices, i is less than 1, it is corrected to 1. If j is greater than
 * the string length, it is corrected to that length. If, after these corrections, i is greater than j,
 * the function returns the empty string.
 */
function sub(s: LuaType, i: LuaType = 1, j: LuaType = -1): string {
    const S = coerceArgToString(s, 'sub', 1)
    let start = posrelat(coerceArgToNumber(i, 'sub', 2), S.length)
    let end = posrelat(coerceArgToNumber(j, 'sub', 3), S.length)

    if (start < 1) start = 1
    if (end > S.length) end = S.length

    if (start <= end) return S.substr(start - 1, end - start + 1)
    return ''
}

/**
 * Receives a string and returns a copy of this string with all lowercase letters changed to uppercase.
 * All other characters are left unchanged.
 * The definition of what a lowercase letter is depends on the current locale.
 */
function upper(s: LuaType): string {
    const S = coerceArgToString(s, 'upper', 1)
    return S.toUpperCase()
}

const libString = new Table({
    byte,
    char,
    find,
    format,
    gmatch,
    gsub,
    len,
    lower,
    match,
    rep,
    reverse,
    sub,
    upper
})

const metatable = new Table({ __index: libString })

export { libString, metatable }