ai-app/app/androidApp/src/test/kotlin/com/example/aiapp/TranscriptItemsTest.kt

package com.example.aiapp

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

/**
 * Where one turn ends and the next begins, which is the part of the fold that had no way of saying
 * anything was wrong: two replies run together read as one long answer, and the seam is somewhere
 * in the middle of a sentence.
 */
class TranscriptItemsTest {
    private var seq = 0L

    private fun fold(items: List<TranscriptItem>, event: SessionEvent) =
        foldEvent(items, SeqEvent(seq = ++seq, ts = 1.0, event = event))

    private fun fold(vararg events: SessionEvent) =
        events.fold(emptyList<TranscriptItem>()) { items, event -> fold(items, event) }

    private fun texts(items: List<TranscriptItem>) =
        items.filterIsInstance<TranscriptItem.AssistantMsg>().map { it.text }

    @Test
    fun an_authentication_failure_stays_visible_as_an_error_row() {
        val entry =
            SeqEvent(
                seq = 7,
                ts = 1.0,
                event = SessionEvent.AuthenticationRequired("sign in again"),
            )

        assertEquals(
            TranscriptItem.ErrorMsg(7, "sign in again"),
            foldEvent(emptyList(), entry).single(),
        )
    }

    @Test
    fun text_after_the_turn_ended_is_a_new_reply_rather_than_more_of_the_last_one() {
        val items =
            fold(
                SessionEvent.AssistantText("You'll get the one-line notice when it lands."),
                SessionEvent.Status("idle"),
                SessionEvent.AssistantText("Dev Updater fix is pushed."),
            )
        assertEquals(
            listOf("You'll get the one-line notice when it lands.", "Dev Updater fix is pushed."),
            texts(items),
        )
    }

    @Test
    fun deltas_of_one_reply_still_accumulate_into_it() {
        val items =
            fold(
                SessionEvent.AssistantText("Still "),
                SessionEvent.AssistantText("running "),
                SessionEvent.Status("running"),
                SessionEvent.AssistantText("its tests."),
            )
        assertEquals(listOf("Still running its tests."), texts(items))
    }

    @Test
    fun completed_text_replaces_provisional_deltas_live() {
        val items =
            fold(
                SessionEvent.AssistantText("I'll inspect the color-c concrete implementation"),
                SessionEvent.AssistantTextFinal(
                    "I’ll inspect the color-correction TODO and the relevant design."
                ),
            )
        assertEquals(
            listOf("I’ll inspect the color-correction TODO and the relevant design."),
            texts(items),
        )
    }

    @Test
    fun completed_text_discards_provisional_deltas_across_a_page_boundary() {
        val earlier = fold(SessionEvent.AssistantText("1. provisional section\n\n"))
        val later =
            fold(
                SessionEvent.AssistantTextFinal("1. final first section\n\n2. final second section")
            )

        assertEquals(
            listOf("1. final first section\n\n2. final second section"),
            texts(joinPages(earlier, later)),
        )
    }

    @Test
    fun a_final_value_after_a_settled_reply_is_a_new_message_across_a_page_boundary() {
        val earlier =
            fold(
                SessionEvent.AssistantText("Previous answer."),
                SessionEvent.Status("idle"),
            )
        val later = fold(SessionEvent.AssistantTextFinal("Next answer."))

        assertEquals(
            listOf("Previous answer.", "Next answer."),
            texts(joinPages(earlier, later)),
        )
    }

    /**
     * The rule that replaced the wall of reports. A turn that starts with nothing recorded in front
     * of it -- a subagent finishing, the CLI picking a conversation back up -- leaves two replies
     * abutting, and only the break says they are two.
     */
    @Test
    fun two_replies_that_meet_are_separated_by_a_rule_and_nothing_else() {
        val items =
            fold(
                SessionEvent.AssistantText("Launched it."),
                SessionEvent.Status("waiting"),
                SessionEvent.AssistantText("Noted."),
            )
        assertEquals(3, items.size, "$items")
        assertTrue(items[1] is TranscriptItem.TurnBreak, "$items")
        assertEquals(listOf("Launched it.", "Noted."), texts(items))
        // Distinct keys: the break shares the reply's seq, and two items with one key take the
        // app down.
        assertEquals(3, items.map { it.key }.toSet().size, "$items")
    }

    /**
     * A reply after anything that draws a row of its own needs no rule: that row is the boundary.
     */
    @Test
    fun a_reply_after_a_row_of_its_own_gets_no_rule() {
        val items =
            fold(
                SessionEvent.AssistantText("Launched it."),
                SessionEvent.Status("idle"),
                SessionEvent.UserMessage("carry on", null, emptyList()),
                SessionEvent.AssistantText("Noted."),
            )
        assertTrue(items.none { it is TranscriptItem.TurnBreak }, "$items")
    }

    @Test
    fun a_repeated_tool_start_is_still_one_row() {
        val start = SessionEvent.ToolStart("exec-1", "Bash", "{\"command\":\"cargo test\"}")
        val items =
            fold(
                start,
                SessionEvent.AssistantText("The test run is still going."),
                start,
                SessionEvent.ToolEnd("exec-1", "finished"),
            )

        val tools = items.filterIsInstance<TranscriptItem.ToolRun>()
        assertEquals(1, tools.size, "$items")
        assertEquals("finished", tools.single().output)
        assertTrue(tools.single().done)
    }

    /**
     * The page-join half of the same rule. A boundary that cuts one reply leaves an unfinished half
     * to be rejoined; a boundary that lands between two turns must not join anything, or paging
     * back puts the run-together paragraph straight back.
     */
    @Test
    fun paging_back_rejoins_a_cut_reply_and_leaves_two_finished_ones_apart() {
        val cut =
            joinPages(
                listOf(TranscriptItem.AssistantMsg(1, "half a ")),
                listOf(TranscriptItem.AssistantMsg(2, "sentence", settled = true)),
            )
        assertEquals(listOf("half a sentence"), texts(cut))

        val whole =
            joinPages(
                listOf(TranscriptItem.AssistantMsg(1, "One turn.", settled = true)),
                listOf(TranscriptItem.AssistantMsg(2, "The next.", settled = true)),
            )
        assertEquals(listOf("One turn.", "The next."), texts(whole))
        // And the rule between them, which the fold that would have made it never got to see.
        assertTrue(whole.any { it is TranscriptItem.TurnBreak }, "$whole")
    }
}