lua-in-js/src/utils.ts

import { LuaError } from './LuaError'
import { Table } from './Table'

type LuaType = undefined | boolean | number | string | Function | Table // thread | userdata

interface Config {
    LUA_PATH?: string
    fileExists?: (path: string) => boolean
    loadFile?: (path: string) => string
    stdin?: string
    stdout?: (data: string) => void
    osExit?: (code: number) => void
}

/** Pattern to identify a float string value that can validly be converted to a number in Lua */
const FLOATING_POINT_PATTERN = /^[-+]?[0-9]*\.?([0-9]+([eE][-+]?[0-9]+)?)?$/

/** Pattern to identify a hex string value that can validly be converted to a number in Lua */
const HEXIDECIMAL_CONSTANT_PATTERN = /^(-)?0x([0-9a-fA-F]*)\.?([0-9a-fA-F]*)$/

function type(v: LuaType): 'string' | 'number' | 'boolean' | 'function' | 'nil' | 'table' {
    const t = typeof v

    switch (t) {
        case 'undefined':
            return 'nil'

        case 'number':
        case 'string':
        case 'boolean':
        case 'function':
            return t

        case 'object':
            if (v instanceof Table) return 'table'
            if (v instanceof Function) return 'function'
    }
}

/* translate a relative string position: negative means back from end */
function posrelat(pos: number, len: number): number {
    if (pos >= 0) return pos
    if (-pos > len) return 0
    return len + pos + 1
}

/**
 * Thows an error with the type of a variable included in the message
 * @param {Object} val The value whise type is to be inspected.
 * @param {String} errorMessage The error message to throw.
 * @throws {LuaError}
 */
function throwCoerceError(val: LuaType, errorMessage?: string): undefined {
    if (!errorMessage) return undefined
    throw new LuaError(`${errorMessage}`.replace(/%type/gi, type(val)))
}

/**
 * Coerces a value from its current type to a boolean in the same manner as Lua.
 * @param {Object} val The value to be converted.
 * @returns {Boolean} The converted value.
 */
function coerceToBoolean(val: LuaType): boolean {
    return !(val === false || val === undefined)
}

/**
 * Coerces a value from its current type to a number in the same manner as Lua.
 * @param {Object} val The value to be converted.
 * @param {String} [errorMessage] The error message to throw if the conversion fails.
 * @returns {Number} The converted value.
 */
function coerceToNumber(val: LuaType, errorMessage?: string): number {
    if (typeof val === 'number') return val

    switch (val) {
        case undefined:
            return undefined
        case 'inf':
            return Infinity
        case '-inf':
            return -Infinity
        case 'nan':
            return NaN
    }

    const V = `${val}`
    if (V.match(FLOATING_POINT_PATTERN)) {
        return parseFloat(V)
    }

    const match = V.match(HEXIDECIMAL_CONSTANT_PATTERN)
    if (match) {
        const [, sign, exponent, mantissa] = match
        let n = parseInt(exponent, 16) || 0
        if (mantissa) n += parseInt(mantissa, 16) / Math.pow(16, mantissa.length)
        if (sign) n *= -1
        return n
    }

    if (errorMessage === undefined) return undefined
    throwCoerceError(val, errorMessage)
}

/**
 * Coerces a value from its current type to a string in the same manner as Lua.
 * @param {Object} val The value to be converted.
 * @param {String} [errorMessage] The error message to throw if the conversion fails.
 * @returns {String} The converted value.
 */
function coerceToString(val: LuaType, errorMessage?: string): string {
    if (typeof val === 'string') return val

    switch (val) {
        case undefined:
        case null:
            return 'nil'
        case Infinity:
            return 'inf'
        case -Infinity:
            return '-inf'
    }

    if (typeof val === 'number') {
        return Number.isNaN(val) ? 'nan' : `${val}`
    }

    if (typeof val === 'boolean') {
        return `${val}`
    }

    if (errorMessage === undefined) return 'nil'
    throwCoerceError(val, errorMessage)
}

function coerceArg<T>(
    value: LuaType,
    coerceFunc: (val: LuaType, errorMessage?: string) => T,
    typ: 'number' | 'string',
    funcName: string,
    index: number
): T {
    return coerceFunc(value, `bad argument #${index} to '${funcName}' (${typ} expected, got %type)`)
}

function coerceArgToNumber(value: LuaType, funcName: string, index: number): number {
    return coerceArg<number>(value, coerceToNumber, 'number', funcName, index)
}

function coerceArgToString(value: LuaType, funcName: string, index: number): string {
    return coerceArg<string>(value, coerceToString, 'string', funcName, index)
}

function coerceArgToTable(value: LuaType, funcName: string, index: number): Table {
    if (value instanceof Table) {
        return value
    } else {
        const typ = type(value)
        throw new LuaError(`bad argument #${index} to '${funcName}' (table expected, got ${typ})`)
    }
}

function coerceArgToFunction(value: LuaType, funcName: string, index: number): Function {
    if (value instanceof Function) {
        return value
    } else {
        const typ = type(value)
        throw new LuaError(`bad argument #${index} to '${funcName}' (function expected, got ${typ})`)
    }
}

const ensureArray = <T>(value: T | T[]): T[] => (value instanceof Array ? value : [value])

const hasOwnProperty = (obj: Record<string, unknown> | unknown[], key: string | number): boolean =>
    Object.prototype.hasOwnProperty.call(obj, key)

export {
    LuaType,
    Config,
    type,
    posrelat,
    coerceToBoolean,
    coerceToNumber,
    coerceToString,
    coerceArgToNumber,
    coerceArgToString,
    coerceArgToTable,
    coerceArgToFunction,
    ensureArray,
    hasOwnProperty
}