package com.example.aiapp

import kotlin.test.Test
import kotlin.test.assertEquals
import kotlin.test.assertTrue

/**
 * The line arithmetic behind the file viewer.
 *
 * Worth a test rather than an eye: a line number that is one out is invisible in a short file and
 * obvious in a long one, and a colour that stops at a line break is invisible until the file has a
 * block comment in it.
 */
class FileLinesTest {
    @Test
    fun `a file that ends with a newline has the number of lines its author would count`() {
        assertEquals(listOf("one", "two"), FileLines.of("one\ntwo\n", null).lines)
        assertEquals(listOf("one", "two"), FileLines.of("one\ntwo", null).lines)
        // Only one is dropped: a blank line at the end of a file is a line somebody typed.
        assertEquals(listOf("one", "two", ""), FileLines.of("one\ntwo\n\n", null).lines)
    }

    @Test
    fun `an empty file is one empty line`() {
        val lines = FileLines.of("", null)
        assertEquals(1, lines.size)
        assertEquals("", lines.line(0).text)
    }

    @Test
    fun `a comment that spans lines is coloured on every line it covers`() {
        val text = "fn a() {}\n/* still\n   a comment */\nfn b() {}\n"
        val lines = FileLines.of(text, Language.RUST)
        assertEquals(4, lines.size)
        val comment = catppuccinSyntax().of(Kind.COMMENT)
        // The whole of the middle line, and the part of the third up to the closer.
        assertTrue(lines.line(1).spanStyles.any { it.item.color == comment && it.start == 0 })
        val third = lines.line(2)
        assertTrue(third.spanStyles.any { it.item.color == comment && it.end == third.length })
        // And the code around it is not commented.
        assertTrue(lines.line(0).spanStyles.none { it.item.color == comment })
        assertTrue(lines.line(3).spanStyles.none { it.item.color == comment })
    }

    @Test
    fun `a span never runs past the line it was cut into`() {
        val lines = FileLines.of("val x = \"a\nb\"\nval y = 1\n", Language.KOTLIN)
        for (index in 0 until lines.size) {
            val line = lines.line(index)
            assertTrue(
                line.spanStyles.all { it.start >= 0 && it.end <= line.length },
                "line $index",
            )
        }
    }

    /**
     * The number every row in the viewer is sized to. It has to be the widest line, because rows of
     * their natural widths scroll sideways by different amounts -- see [FileViewer].
     */
    @Test
    fun `the column count is the widest line, counting a tab as eight`() {
        assertEquals(5, FileLines.of("one\nthree\nx\n", null).columns)
        // A tab counts up to eight, and upwards on purpose: over-estimating leaves empty space
        // past the longest line, under-estimating puts its end out of reach.
        assertEquals(9, FileLines.of("\tx\nshort\n", null).columns)
        // An empty file is one empty line, which is no columns at all rather than an error.
        assertEquals(0, FileLines.of("", null).columns)
    }

    @Test
    fun `a file with no language is plain`() {
        val lines = FileLines.of("fn main() {}\n", null)
        assertTrue(lines.line(0).spanStyles.isEmpty())
    }

    @Test
    fun `a language comes from the extension, and only from a real one`() {
        assertEquals(Language.KOTLIN, fileLanguage("Main.kt"))
        assertEquals(Language.KOTLIN, fileLanguage("build.gradle.kts"))
        assertEquals(Language.RUST, fileLanguage("files.rs"))
        assertEquals(Language.TOML, fileLanguage("Cargo.toml"))
        assertEquals(null, fileLanguage("Makefile"))
        assertEquals(null, fileLanguage(".bashrc"))
        assertEquals(null, fileLanguage("notes.txt"))
    }
}