package main

import (
	"errors"
	"fmt"
	"strconv"
	"strings"
)

func phpUnquote(s string) (string, error) {
	if len(s) == 0 {
		return "", errors.New("expected quotes around string")
	}

	if s[0] == '"' {
		// Quote system is similar enough to Go's that strconv will probably just work

		// PROBLEM 1: PHP has some lax parsing for unknown escape sequences
		// e.g. regex("foo\.") will be silently parsed as regex("foo.")

		// PROBLEM 2: PHP supports multiline string literals, strconv.Unquote does not
		// Apply fixup
		s2 := strings.Replace(strings.Replace(s, "\r", `\r`, -1), "\n", `\n`, -1)

		ret, err := strconv.Unquote(s2)
		if err != nil {
			return "", fmt.Errorf("Parsing string literal `%s`: %v", s, err)
		}

		return ret, nil
	}

	if s[0] == '\'' {
		// Single-quotes escape fewer things
		unSQuo := strings.NewReplacer(`\'`, `'`, `\\`, `\`)
		return unSQuo.Replace(s[1 : len(s)-1]), nil
	}

	return "", errors.New("expected single/double quotes")
}