transcendental-lisp/src/test/kotlin/interpreter/LispInterpreterTest.kt

package interpreter

import environment.RuntimeEnvironment
import interpreter.InteractiveLispInterpreter.Companion.PROMPT
import org.assertj.core.api.Assertions.assertThat
import org.junit.jupiter.api.AfterEach
import org.junit.jupiter.api.BeforeEach
import org.junit.jupiter.api.Test
import testutil.TestUtilities.createInputStreamFromString
import java.io.ByteArrayOutputStream
import java.io.PrintStream

class LispInterpreterTest {

    companion object {
        private const val TERMINATED = "terminated"
        private val FILE = LispInterpreterTest::class.java.getResource("file.lisp").file
    }

    private val indicatorSet = mutableSetOf<String>()
    private val outputStream = ByteArrayOutputStream()
    private val errorOutputStream = ByteArrayOutputStream()

    private fun setCommonFeatures() {
        LispInterpreterBuilder.setOutput(PrintStream(outputStream))
        LispInterpreterBuilder.setErrorOutput(PrintStream(errorOutputStream))
        LispInterpreterBuilder.setTerminationFunction { }
        LispInterpreterBuilder.setErrorTerminationFunction { indicatorSet.add(TERMINATED) }
    }

    private fun assertTerminated() {
        assertThat(indicatorSet).contains(TERMINATED)
    }

    private fun assertErrorMessageWritten() {
        assertThat(errorOutputStream.toByteArray()).isNotEmpty()
    }

    @BeforeEach()
    fun setUp() {
        indicatorSet.clear()
        outputStream.reset()
        errorOutputStream.reset()
        RuntimeEnvironment.reset()
        LispInterpreterBuilder.reset()
    }

    @AfterEach()
    fun tearDown() {
        RuntimeEnvironment.reset()
        LispInterpreterBuilder.reset()
    }

    @Test
    fun `build an interactive interpreter`() {
        setCommonFeatures()
        LispInterpreterBuilder.setInput(System.`in`, "stdin")
        val interpreter = LispInterpreterBuilder.build()

        assertThat(interpreter is InteractiveLispInterpreter).isTrue()
    }

    @Test
    fun `build a non interactive interpreter`() {
        setCommonFeatures()
        LispInterpreterBuilder.setInput(System.`in`, "stdin")
        LispInterpreterBuilder.setNotInteractive()
        val interpreter = LispInterpreterBuilder.build()

        assertThat(interpreter is InteractiveLispInterpreter).isFalse()
        assertThat(interpreter is FileLispInterpreter).isFalse()
    }

    @Test
    fun `build a file based interpreter`() {
        setCommonFeatures()
        LispInterpreterBuilder.useFile(FILE)
        val interpreter = LispInterpreterBuilder.build()

        assertThat(interpreter is FileLispInterpreter).isTrue()
    }

    @Test
    fun `building an interpreter on a bad file terminates correctly`() {
        setCommonFeatures()
        LispInterpreterBuilder.useFile("does-not-exist.lisp")
        LispInterpreterBuilder.build()

        assertErrorMessageWritten()
        assertTerminated()
    }

    @Test
    fun `the decorators are initialized with the correct defaults`() {
        LispInterpreterBuilder.build()

        assertThat(RuntimeEnvironment.decoratePrompt("")).isEmpty()
        assertThat(RuntimeEnvironment.decorateValueOutput("")).isEmpty()
        assertThat(RuntimeEnvironment.decorateWarningOutput("")).isEmpty()
        assertThat(RuntimeEnvironment.decorateErrorOutput("")).isEmpty()
        assertThat(RuntimeEnvironment.decorateCriticalOutput("")).isEmpty()
    }

    @Test
    fun `the decorators are set correctly`() {
        LispInterpreterBuilder.setPromptDecorator { s -> "#$s#" }
        LispInterpreterBuilder.setValueOutputDecorator { s -> "@$s@" }
        LispInterpreterBuilder.setWarningOutputDecorator { s -> "%$s%" }
        LispInterpreterBuilder.setErrorOutputDecorator { s -> "*$s*" }
        LispInterpreterBuilder.setCriticalOutputDecorator { s -> "$$s$" }
        LispInterpreterBuilder.build()

        assertThat(RuntimeEnvironment.decoratePrompt("x")).isEqualTo("#x#")
        assertThat(RuntimeEnvironment.decorateValueOutput("x")).isEqualTo("@x@")
        assertThat(RuntimeEnvironment.decorateWarningOutput("x")).isEqualTo("%x%")
        assertThat(RuntimeEnvironment.decorateErrorOutput("x")).isEqualTo("*x*")
        assertThat(RuntimeEnvironment.decorateCriticalOutput("x")).isEqualTo("\$x$")
    }

    @Test
    fun `the file based interpreter works and prints the last value only`() {
        setCommonFeatures()
        LispInterpreterBuilder.useFile(FILE)
        LispInterpreterBuilder.build().interpret()

        assertThat(outputStream.toString()).isEqualTo("PICKLE\n\n")
        assertThat(errorOutputStream.toString()).isEmpty()
    }

    @Test
    fun `the interactive interpreter works`() {
        setCommonFeatures()
        LispInterpreterBuilder.setInput(createInputStreamFromString("'pickle"), "input")
        LispInterpreterBuilder.build().interpret()

        assertThat(outputStream.toString()).isEqualTo("$PROMPT\nPICKLE\n$PROMPT\n")
        assertThat(errorOutputStream.toString()).isEmpty()
    }

    @Test
    fun `the interpreter handles bad input`() {
        setCommonFeatures()
        LispInterpreterBuilder.setNotInteractive()
        LispInterpreterBuilder.setInput(createInputStreamFromString("['pickle"), "input")
        LispInterpreterBuilder.build().interpret()

        assertThat(outputStream.toString()).isEqualTo("PICKLE\n\n")
        assertThat(errorOutputStream.toString()).isEqualTo("[error] illegal character >>[<< - line 1, column 1\n")
    }

    @Test
    fun `the interpreter handles an evaluation error`() {
        setCommonFeatures()
        LispInterpreterBuilder.setNotInteractive()
        LispInterpreterBuilder.setInput(createInputStreamFromString("pickle"), "input")
        LispInterpreterBuilder.build().interpret()

        assertThat(outputStream.toString()).isEqualTo("\n")
        assertThat(errorOutputStream.toString()).isEqualTo("[error] symbol PICKLE has no value\n")
    }
}