Depth: change internal representation and API, implement Comparable<Int>

wot-dijkstra/src/main/kotlin/org/pgpainless/wot/network/Depth.kt

@@ -7,16 +7,16 @@ package org.pgpainless.wot.network
 /**
  * Depth of a trust signature.
  */
-class Depth private constructor(val limit: Int?) : Comparable<Depth> {
+class Depth private constructor(private val limit: Int) : Comparable<Int> {
+
+    // Uses a byte for internal representation, like in the OpenPGP "Trust Signature" subpacket
 
     companion object {
         /**
          * The target is trusted to an unlimited degree.
          */
         @JvmStatic
-        fun unconstrained() : Depth {
-            return Depth(null)
-        }
+        fun unconstrained() = Depth(255)
 
         /**
          * The target is trusted to a limited degree.
@@ -34,32 +34,27 @@ class Depth private constructor(val limit: Int?) : Comparable<Depth> {
          */
         @JvmStatic
         fun auto(limit: Int): Depth {
-            return if (limit == 255) {
-                unconstrained()
-            } else {
-                limited(limit)
+            require(limit in 0..255) {
+                "Trust depth MUST be a value between 0 and 255."
             }
+            return Depth(limit)
         }
     }
 
     /**
      * Return true, if the [Depth] is unconstrained.
      */
-    fun isUnconstrained() : Boolean {
-        return limit == null
-    }
+    fun isUnconstrained() = limit == 255
 
     /**
      * The value of this Depth, as used in OpenPGP.
      *
      * Unlimited is 255.
      */
-    fun value(): Int {
-        return limit ?: 255
-    }
+    fun value() = limit
 
     /**
-     * Decrease the trust depth by one and return the result.
+     * Decrease the trust depth by `value` and return the result.
      * If the [Depth] is unconstrained, the result will still be unconstrained.
      * @throws IllegalArgumentException if the [Depth] cannot be decreased any further
      */
@@ -67,7 +62,7 @@ class Depth private constructor(val limit: Int?) : Comparable<Depth> {
         return if (isUnconstrained()) {
             unconstrained()
         } else {
-            if (limit!! >= value) {
+            if (limit >= value) {
                 limited(limit - value)
             } else {
                 throw IllegalArgumentException("Depth cannot be decreased.")
@@ -79,19 +74,19 @@ class Depth private constructor(val limit: Int?) : Comparable<Depth> {
      * Return the minimum [Depth] of this and the other [Depth].
      */
     fun min(other: Depth): Depth {
-        return if (compareTo(other) <= 0) {
-            this
-        } else {
+        return if (limit > other.limit) {
             other
+        } else {
+            this
         }
     }
 
-    override fun compareTo(other: Depth): Int {
-        return when (Pair(isUnconstrained(), other.isUnconstrained())) {
-            Pair(true, true) -> 0
-            Pair(true, false) -> 1
-            Pair(false, true) -> -1
-            else -> limit!!.compareTo(other.limit!!)
+    override fun compareTo(other: Int): Int {
+        return if (isUnconstrained()) {
+            // If this is unconstrained, it is bigger than `other`
+            1
+        } else {
+            limit.compareTo(other)
         }
     }
 
@@ -104,10 +99,12 @@ class Depth private constructor(val limit: Int?) : Comparable<Depth> {
     }
 
     override fun toString(): String {
-        return if (isUnconstrained()) { "unconstrained" } else { limit!!.toString() }
+        return if (isUnconstrained()) {
+            "unconstrained"
+        } else {
+            limit.toString()
+        }
     }
 
-    override fun hashCode(): Int {
-        return limit ?: 0 // TODO: 255?
-    }
+    override fun hashCode() = limit
 }

wot-dijkstra/src/main/kotlin/org/pgpainless/wot/network/EdgeComponent.kt

@@ -33,11 +33,11 @@ data class EdgeComponent(
 ) {
 
     override fun toString(): String {
-        return if (trustDepth.limit == 0)
-            "${issuer.fingerprint} certifies binding: $userId <-> ${target.fingerprint} [$trustAmount]"
-        else {
+        return if (trustDepth > 0) {
             val scope = if (regexes.regexStrings.isEmpty()) "" else ", scope: $regexes"
             "${issuer.fingerprint} delegates to ${target.fingerprint} [$trustAmount, depth $trustDepth$scope]"
+        } else {
+            "${issuer.fingerprint} certifies binding: $userId <-> ${target.fingerprint} [$trustAmount]"
         }
     }
 }

wot-dijkstra/src/main/kotlin/org/pgpainless/wot/query/Path.kt

@@ -97,7 +97,7 @@ class Path(
         require(target.fingerprint == nComponent.issuer.fingerprint) {
             "Cannot append edge to path: Path's tail is not issuer of the edge."
         }
-        require(residualDepth.isUnconstrained() || residualDepth.limit!! > 0) {
+        require(residualDepth > 0) {
             "Not enough depth."
         }
 

wot-dijkstra/src/test/kotlin/org/pgpainless/wot/network/DepthTest.kt

@@ -9,7 +9,10 @@ import org.junit.jupiter.api.assertThrows
 import org.pgpainless.wot.network.Depth.Companion.auto
 import org.pgpainless.wot.network.Depth.Companion.limited
 import org.pgpainless.wot.network.Depth.Companion.unconstrained
-import kotlin.test.*
+import kotlin.test.assertEquals
+import kotlin.test.assertFalse
+import kotlin.test.assertNotNull
+import kotlin.test.assertTrue
 
 class DepthTest {
 
@@ -22,14 +25,15 @@ class DepthTest {
     @Test
     fun `verify Depth#unconstrained() has null depth`() {
         val depth = unconstrained()
-        assertNull(depth.limit)
+        assert(depth.isUnconstrained())
+        assertEquals(depth.value(), 255)
     }
 
     @Test
     fun `verify Depth#limited(2) initializes properly`() {
         val limited = limited(2)
-        assertNotNull(limited.limit)
-        assertEquals(2, limited.limit)
+        assert(!limited.isUnconstrained())
+        assertEquals(2, limited.value())
     }
 
     @Test
@@ -50,7 +54,7 @@ class DepthTest {
         val limited = limited(3)
         val decreased = limited.decrease(2)
         assertFalse(decreased.isUnconstrained())
-        assertEquals(1, decreased.limit)
+        assertEquals(1, decreased.value())
     }
 
     @Test
@@ -63,17 +67,21 @@ class DepthTest {
     @Test
     fun `verify proper function of compareTo()`() {
         val unlimited = unconstrained()
-        val unlimited2 = unconstrained()
         val depth2 = limited(2)
-        val depth2_ = limited(2)
         val depth5 = limited(5)
-        assertEquals(0, unlimited.compareTo(unlimited2))
-        assertTrue(unlimited.compareTo(depth2) > 0)
-        assertTrue(unlimited.compareTo(depth5) > 0)
-        assertTrue(depth2.compareTo(unlimited) < 0)
-        assertTrue(depth2.compareTo(depth5) < 0)
-        assertTrue(depth5.compareTo(depth2) > 0)
-        assertEquals(0, depth2.compareTo(depth2_))
+        assertTrue(unlimited > 0)
+        assertTrue(unlimited > 255)
+        assertTrue(unlimited > 256)
+
+        assertTrue(depth2 > 0)
+        assertTrue(depth2 > 1)
+        assertFalse(depth2 > 2)
+        assertFalse(depth2 > 256)
+
+        assertTrue(depth5 > 1)
+        assertTrue(depth5 > 4)
+        assertFalse(depth5 > 5)
+        assertFalse(depth5 > 256)
     }
 
     @Test
@@ -108,7 +116,7 @@ class DepthTest {
     @Test
     fun `verify that Depth#auto(255) yields an unconstrained Depth`() {
         assertTrue { auto(255).isUnconstrained() }
-        assertNull(auto(255).limit)
+        assertEquals(auto(255).value(), 255)
     }
 
     @Test
@@ -117,7 +125,7 @@ class DepthTest {
         assertFalse { auto(120).isUnconstrained() }
         assertFalse { auto(254).isUnconstrained() }
 
-        assertNotNull(auto(42).limit)
+        assertNotNull(auto(42).value())
     }
 
     @Test