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 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}")
        }
    }

}