Convert Go http routes to express-js fashion

express_router_regex.go

package main
import "os"
import "text/tabwriter"
import "regexp"
import "fmt"

func main(){
  // silent the groups to eliminate redundant data in match
  var r = compileRegex("/:name/:service/:id(?:[0-9]{0,3})")
  var regex = r.FindStringSubmatch("/api/buy/123")
  var params = make(map[string]string)
  // to print beautifully 
  var writer = tabwriter.NewWriter(os.Stdout, 0, 0, 1, ' ', tabwriter.AlignRight|tabwriter.Debug)
  for i, name := range r.SubexpNames() {
    if i == 0 {
      // first value is matched string itself
      continue;
    }
    params[name] = regex[i]
    fmt.Fprintln(writer, "param: \t"+ string(name)+"\tvalue:\t" + string(regex[i]))
  }
  writer.Flush()
}
func compileRegex(url string) *regexp.Regexp {
  var i = 0
  var buffer = "/"
  var regexStr = "^"
  var endVariable = ">(?:[A-Za-z0-9\\-\\_\\$\\.\\+\\!\\*\\'\\(\\)\\,]+))"
  if url[0] == '/' {
    i++
  }
  for i < len(url) {
    if url[i] == '/' {
      // attach the last parsed part and then move ahead
      regexStr += buffer + "/"
      buffer = ""
      i++
    } else {
      if url[i] == ':' && ( (i-1 >=0 && url[i-1] == '/') || (i-1 == -1)) {
        // a variable found, lets read it
        var tempbuffer = "(?P<"
        var variableName = ""
        var variableNameDone = false
        var done = false
        var hasRegex = false
        var innerGroup = 0
        // lets branch in to look deeper
        i++
        for done != true && i < len(url) {
          if url[i] == '/' {
            // are we done yet? have the name?
            if variableName != "" {
              // are all brackets closed?
              if innerGroup == 0 {
                if hasRegex == false {
                  // attach the constant endVariable for URL param
                  tempbuffer += endVariable
                }
                done = true
                break
              }
            }
            // something went wrong in during parsing. panic.
            tempbuffer = ""
            break;
          } else if url[i] == '(' {
            // group begin, have we saved the variable name?
            if variableNameDone == false {
              variableNameDone = true
              tempbuffer += ">" // close variable name tag
              hasRegex = true // this group has regex
            }
            tempbuffer += string(url[i])
            if url[i - 1] != '\\' {
              innerGroup++
            }
          } else if url[i] == ')' {
            tempbuffer += string(url[i])
            if url[i - 1] != '\\' {
              innerGroup--
            }
          } else {
            if variableNameDone == false {
              variableName += string(url[i])
            }
            tempbuffer += string(url[i])
          }
          i++
        }
        if tempbuffer != "" {
          if hasRegex == false && done == false {
            tempbuffer += endVariable
          } else if hasRegex {
            tempbuffer += ")"
          }
          buffer += tempbuffer
        } else {
          panic("Invalid Route regex")
        }
      } else {
        buffer += string(url[i])
        i++
      }
    }
  }
  if buffer != "" {
    regexStr += buffer
  }
  return regexp.MustCompile(regexStr + "(?:[\\/]{0,1})$")
}