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package router
import scala.collection.mutable.ArrayBuffer
import scala.util.matching.Regex
class Router[T] {
val routes = new ArrayBuffer[Route[T]]()
def addRoute (
path: String,
target: T,
defaults: Map[String, String] = Map(),
validations: Map[String, Regex] = Map()
) {
routes += new Route(path, defaults, validations, target)
}
def insertRoute (
path: String,
target: T,
defaults: Map[String, String] = Map(),
validations: Map[String, Regex] = Map(),
at: Int = 0
) {
routes insert (
at min routes.length,
new Route(path, defaults, validations, target)
)
}
def route (path: String): Option[Match[T]] = {
def testRoutes (
components: Seq[String],
routes: List[Route[T]]
): Option[Match[T]] = routes match {
case r :: rs => r.route(components) match {
case Some(found) => Some(found)
case None => testRoutes(components, rs)
}
case _ => None
}
testRoutes(path.split("/"), routes.toList)
}
private class AmbiguousRouteMapping(
mapping: Map[String, String],
paths: Seq[String]
) extends RuntimeException {
override def getMessage (): String = {
"Ambiguous path descriptor (specified keys " +
mapping.keys.mkString(", ") +
"): could match paths " +
paths.mkString(", ")
}
}
def uriFor (mapping: Map[String, String]): Option[String] = {
// first remove all routes that can't possibly match
// - if the route requires a variable component that doesn't exist in the
// mapping, then it can't match
// - if the route contains a value for a variable component that doesn't
// pass the validation for that component, it can't match
// - if the route contains a default value, and that component also exists
// in the mapping, then the values must match
val possible = routes.flatMap(r => {
r.pathWithMapping(mapping) match {
case Some(path) => Some(r -> path)
case None => None
}
})
possible.toList match {
case Nil => None
case (r, path) :: Nil => Some(path)
case rs => {
// then try to disambiguate the remaining possibilities
// - we want the route with the fewest number of "extra" items in the
// mapping, after removing defaults and variable path components
val possibleByRemainder = possible.groupBy { case (r, path) => {
(mapping.keys.toSet -- r.defaults.keys.toSet -- r.variables).size
} }
val found = possibleByRemainder(possibleByRemainder.keys.min)
found.toList match {
case Nil => None
case (r, path) :: Nil => Some(path)
case rs =>
throw new AmbiguousRouteMapping(mapping, rs.map(_._1.path))
}
}
}
}
}
class Route[T] (
val path: String,
val defaults: Map[String, String],
val validations: Map[String, Regex],
val target: T
) {
import Route._
lazy val variables = components.flatMap(getVariableName)
def route(
parts: Seq[String],
components: Seq[String] = components,
mapping: Map[String, String] = defaults
): Option[Match[T]] = {
if (components.filter(!isOptional(_)).length == 0 && parts.length == 0) {
Some(new Match[T](path, mapping, target))
}
else if (components.length == 0 || parts.length == 0) {
None
}
else {
components.head match {
case Optional(name) => {
if (validate(name, parts.head)) {
route(parts.tail, components.tail, mapping + (name -> parts.head))
}
else {
route(parts, components.tail, mapping)
}
}
case Variable(name) => {
if (validate(name, parts.head)) {
route(parts.tail, components.tail, mapping + (name -> parts.head))
}
else {
None
}
}
case literal => parts.head match {
case `literal` => route(parts.tail, components.tail, mapping)
case _ => None
}
}
}
}
override def toString = path
def pathWithMapping (mapping: Map[String, String]): Option[String] = {
val requiredDefaults = defaults.keys.filter { k =>
mapping.isDefinedAt(k) && !variables.contains(k)
}
if (requiredDefaults.forall(k => defaults(k) == mapping(k)) &&
requiredVariables.forall(mapping.isDefinedAt)) {
val boundComponents = components.flatMap {
case Optional(v) => {
val component = (mapping get v).flatMap(validComponentValue(v, _))
defaults get v match {
case Some(default) => {
component.flatMap {
case `default` => None
case c => Some(c)
}
}
case None => component
}
}
case Variable(v) => validComponentValue(v, (mapping(v)))
case literal => Some(literal)
}
Some(boundComponents.mkString("/"))
}
else {
None
}
}
private lazy val components =
path.split("/").filter(_.length > 0)
private lazy val requiredVariables =
components.filter(!isOptional(_)).flatMap(getVariableName)
private lazy val hasVariable = variables.toSet
private def isOptional (component: String) =
Optional.findFirstIn(component).nonEmpty
private def isVariable (component: String) =
Variable.findFirstIn(component).nonEmpty
private def getVariableName (component: String) = component match {
case Variable(name) => Some(name)
case _ => None
}
private def validate (name: String, component: String) =
validations get name match {
case Some(rx) => rx.findFirstIn(component).nonEmpty
case None => true
}
private def validComponentValue (name: String, component: String) =
if (validate(name, component)) { Some(component) } else { None }
}
object Route {
private val Optional = """^\?:(.*)$""".r
private val Variable = """^\??:(.*)$""".r
}
class Match[T] (
val path: String,
val mapping: Map[String, String],
val target: T
)
|
