package be.ugent.logprog.lexer

import lexer.Error
import lexer.Lexer
import lexer.TokenType
import org.junit.jupiter.api.Test
import org.junit.jupiter.api.assertThrows
import kotlin.test.assertEquals

class LexerScanTest {
    @Test
    fun scan_emptyString_returns_EOF() {
        val lexer = Lexer("")
        val tokens = lexer.scan()
        assertEquals(1, tokens.size, "Expected 1 token, got ${tokens.size}")
        assertEquals(TokenType.EOF, tokens[0].type, "Expected EOF token, got ${tokens[0].type}")
    }

    @Test
    fun scan_unknownSymbol_returns_Error() {
        val lexer = Lexer("€")
        assertThrows<Error>({
            val tokens = lexer.scan()
        })
    }

    @Test
    fun scan_dot_returns_Dot() {
        val lexer = Lexer(".")
        val tokens = lexer.scan()
        assertEquals(2, tokens.size)
        assertEquals(TokenType.DOT, tokens[0].type, "Expected DOT token, got ${tokens[0].type}")
        assertEquals(TokenType.EOF, tokens[1].type, "Expected EOF token, got ${tokens[1].type}")
    }

    @Test
    fun scan_two_dots_returns_two_dots() {
        val lexer = Lexer("..")
        val tokens = lexer.scan()
        assertEquals(3, tokens.size)
        assertEquals(TokenType.DOT, tokens[0].type, "Expected DOT token, got ${tokens[0].type}")
        assertEquals(TokenType.DOT, tokens[1].type, "Expected DOT token, got ${tokens[1].type}")
        assertEquals(TokenType.EOF, tokens[2].type, "Expected EOF token, got ${tokens[2].type}")
    }
    
    @Test
    fun scan_letter_returns_letter() {
        val lexer = Lexer("a")
        val tokens = lexer.scan()

        assertEquals(2, tokens.size)

        assertEquals(TokenType.ALPHANUMERIC, tokens[0].type, "Expected ALPHANUMERIC token, got ${tokens[0].type}")
        assertEquals(TokenType.EOF, tokens[1].type, "Expected EOF token, got ${tokens[1].type}")

        assertEquals(1, tokens[0].position.length, "Expected length 1, got ${tokens[0].position.length}")
    }

    @Test
    fun scan_word_returns_alphanumerics() {
        val lexer = Lexer("word")
        val tokens = lexer.scan()

        assertEquals(2, tokens.size)

        assertEquals(TokenType.ALPHANUMERIC, tokens[0].type, "Expected ALPHANUMERIC token, got ${tokens[0].type}")
        assertEquals(TokenType.EOF, tokens[1].type, "Expected EOF token, got ${tokens[1].type}")

        assertEquals(4, tokens[0].position.length, "Expected length 4, got ${tokens[0].position.length}")
    }
}