add model classes for engine,node and queue and implement the basic g…

…eneric algorithm using them

src/main/io/dkozak/search/engine/engine.kt

@@ -0,0 +1,27 @@
+package io.dkozak.search.engine
+
+import io.dkozak.search.model.EngineConfiguration
+import io.dkozak.search.model.Node
+
+
+fun search(engineConfiguration: EngineConfiguration, logger: (String) -> Unit = {}) = engineConfiguration.executeSearch(logger)
+
+private fun EngineConfiguration.executeSearch(logger: (String) -> Unit): Node? {
+    val queue = searchQueue
+    queue.addNode(initialState)
+    while (!queue.isEmpty()) {
+        val nextNode = queue.next()
+        logger("Exploring state $nextNode")
+        if (isFinalState(nextNode)) {
+            logger("$nextNode is a final state, returning")
+            return nextNode
+        }
+        val children = expandNode(nextNode)
+        logger("Expanded node and got these children $children")
+        val filtered = children.filter(nodeFilter)
+        logger("Children after filtering $filtered")
+        queue.addNodes(filtered)
+    }
+    logger("Whole state space explored and no final node found, returning null")
+    return null
+}

src/main/io/dkozak/search/model/EngineConfiguration.kt

@@ -0,0 +1,10 @@
+package io.dkozak.search.model
+
+class EngineConfiguration
+(
+        val initialState: Node,
+        val searchQueue: SearchQueue,
+        val expandNode: (Node) -> List<Node>,
+        val nodeFilter: (Node) -> Boolean,
+        val isFinalState: (Node) -> Boolean
+)

src/main/io/dkozak/search/model/Node.kt

@@ -0,0 +1,4 @@
+package io.dkozak.search.model
+
+interface Node {
+}

src/main/io/dkozak/search/model/SearchQueue.kt

@@ -0,0 +1,9 @@
+package io.dkozak.search.model
+
+interface SearchQueue {
+    fun next(): Node
+    fun addNodes(nodes: List<Node>)
+    fun isEmpty(): Boolean
+
+    fun addNode(node: Node) = addNodes(listOf(node))
+}