REPL checkpoint

src/Main.kt

@@ -1,9 +1,98 @@
-fun main() {
-    for (i in 1..10) {
-        println("Hello, Kotlin Command Line Utility!")
-    }
+import better_parser.PrologParser
+import better_parser.SimpleReplParser
+import interpreter.SourceFileReader
+import prolog.Answer
+import prolog.Program
+import prolog.ast.logic.Fact
+import prolog.ast.logic.Rule
+import prolog.ast.terms.Atom
+import prolog.ast.terms.CompoundTerm
+import prolog.ast.terms.Variable
+import prolog.builtins.Conjunction
+
+fun help(): String {
+    println("Unknown command. Type 'h' for help.")
+    println("Commands:")
+    println("  ;   - find next solution")
+    println("  a   - abort")
+    println("  .   - end query")
+    println("  h   - help")
+    println("  exit - exit Prolog REPL")
+    return ""
 }
 
-fun testMe(): String {
-    return "Hello, Kotlin Command Line Utility!"
+fun say(message: String) {
+    println(message)
+}
+
+fun prompt(message: String): String {
+    print("$message ")
+    var input: String = readlnOrNull() ?: help()
+    while (input.isBlank()) {
+        input = readlnOrNull() ?: help()
+    }
+    return input
+}
+
+fun prettyResult(result: Answer): String {
+    result.fold(
+        onSuccess = {
+            val subs = result.getOrNull()!!
+            if (subs.isEmpty()) {
+                return "true."
+            }
+            return subs.entries.joinToString(", ") { "${it.key} = ${it.value}" }
+        },
+        onFailure = {
+            return "Failure: ${result.exceptionOrNull()!!}"
+        }
+    )
+}
+
+val knownCommands = setOf(";", "a", ".")
+
+fun main() {
+    SourceFileReader().readFile("tests/better_parser/resources/parent.pl")
+
+    val parser = SimpleReplParser(debug = false)
+
+    say("Prolog REPL. Type 'exit' to quit.")
+
+    while (true) {
+        val queryString = prompt("?-")
+
+        try {
+            val query = parser.parse(queryString)
+            val answers = query.satisfy(emptyMap())
+
+            if (answers.none()) {
+                say("false.")
+            } else {
+                val iterator = answers.iterator()
+
+                var previous = iterator.next()
+
+                while (iterator.hasNext()) {
+                    var command = prompt(prettyResult(previous))
+
+                    while (command !in knownCommands) {
+                        say("Unknown action: $command (h for help)")
+                        command = prompt("Action?")
+                    }
+
+                    when (command) {
+                        ";" -> previous = iterator.next()
+                        "a" -> break
+                        "." -> break
+                    }
+                }
+
+                say(prettyResult(previous))
+            }
+
+        } catch (e: Exception) {
+            println("Error: ${e.message}")
+        }
+    }
+
 }