prog8/compilerAst/src/prog8/ast/antlr/EscapeChars.kt

package prog8.ast.antlr

import prog8.ast.base.SyntaxError
import prog8.code.core.Position

fun escape(str: String): String {
    val es = str.map {
        when(it) {
            '\t' -> "\\t"
            '\n' -> "\\n"
            '\r' -> "\\r"
            '"' -> "\\\""
            in '\u8000'..'\u80ff' -> "\\x" + (it.code - 0x8000).toString(16).padStart(2, '0')
            in '\u0000'..'\u00ff' -> it.toString()
            else -> "\\u" + it.code.toString(16).padStart(4, '0')
        }
    }
    return es.joinToString("")
}

fun unescape(str: String, position: Position): String {
    val result = mutableListOf<Char>()
    val iter = str.iterator()
    while(iter.hasNext()) {
        val c = iter.nextChar()
        if(c=='\\') {
            val ec = iter.nextChar()
            result.add(when(ec) {
                '\\' -> '\\'
                'n' -> '\n'
                'r' -> '\r'
                '"' -> '"'
                '\'' -> '\''
                'u' -> {
                    try {
                        "${iter.nextChar()}${iter.nextChar()}${iter.nextChar()}${iter.nextChar()}".toInt(16).toChar()
                    } catch (sb: StringIndexOutOfBoundsException) {
                        throw SyntaxError("invalid \\u escape sequence", position)
                    } catch (nf: NumberFormatException) {
                        throw SyntaxError("invalid \\u escape sequence", position)
                    }
                }
                'x' -> {
                    // special hack 0x8000..0x80ff  will be outputted verbatim without encoding
                    try {
                        val hex = ("" + iter.nextChar() + iter.nextChar()).toInt(16)
                        (0x8000 + hex).toChar()
                    } catch (sb: StringIndexOutOfBoundsException) {
                        throw SyntaxError("invalid \\x escape sequence", position)
                    } catch (nf: NumberFormatException) {
                        throw SyntaxError("invalid \\x escape sequence", position)
                    }
                }
                else -> throw SyntaxError("invalid escape char in string: \\$ec", position)
            })
        } else {
            result.add(c)
        }
    }
    return result.joinToString("")
}