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

package com.example.aiapp

import java.time.ZoneId
import kotlin.test.Test
import kotlin.test.assertEquals
import kotlin.test.assertNull
import kotlin.test.assertTrue

/**
 * The model's working as its own row, and the line under a finished reply.
 *
 * Both have the same shape of hazard: a state nothing measured must not come out looking like one
 * that was. A block interrupted mid-thought has no duration, and a provider that reports no
 * generation speed has no figure -- neither may borrow one.
 */
class ThinkingTest {
    private val utc = ZoneId.of("UTC")
    private var seq = 0L

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

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

    private fun thinking(items: List<TranscriptItem>) =
        items.filterIsInstance<TranscriptItem.ThinkingRow>()

    @Test
    fun `deltas accumulate into one block that ends with its duration`() {
        val items =
            fold(
                SessionEvent.Thinking("the user "),
                SessionEvent.Thinking("wants a card"),
                SessionEvent.ThinkingDone(12_400),
                SessionEvent.AssistantText("Here it is."),
            )
        val block = thinking(items).single()
        assertEquals("the user wants a card", block.text)
        assertEquals(12_400, block.ms)
        assertEquals("Thought for 12.4s", thinkingHeadline(block))
        // Its own row, above the reply rather than inside it.
        assertEquals(1, items.filterIsInstance<TranscriptItem.AssistantMsg>().size)
    }

    @Test
    fun `a block the turn ended in the middle of stops without naming a span`() {
        val items = fold(SessionEvent.Thinking("half a thought"), SessionEvent.Status("idle"))
        val block = thinking(items).single()
        assertNull(block.ms)
        assertTrue(!block.open)
        assertEquals("Thought", thinkingHeadline(block))
    }

    @Test
    fun `a block still being thought says so`() {
        val block = thinking(fold(SessionEvent.Thinking("hmm"))).single()
        assertTrue(block.open)
        assertEquals("Thinking", thinkingHeadline(block))
    }

    @Test
    fun `thinking between two replies is two replies and two blocks`() {
        val items =
            fold(
                SessionEvent.Thinking("first"),
                SessionEvent.ThinkingDone(1_000),
                SessionEvent.AssistantText("One."),
                SessionEvent.Thinking("second"),
                SessionEvent.ThinkingDone(2_000),
                SessionEvent.AssistantText("Two."),
            )
        assertEquals(listOf("first", "second"), thinking(items).map { it.text })
        assertEquals(
            listOf("One.", "Two."),
            items.filterIsInstance<TranscriptItem.AssistantMsg>().map { it.text },
        )
    }

    @Test
    fun `a reply carries when it was sent and what it cost to produce`() {
        val items =
            fold(emptyList(), SessionEvent.AssistantText("Done."), ts = 1_788_609_600.0).let {
                fold(it, SessionEvent.UsageDelta(42, 100, 18.37, 9_489))
            }
        val reply = items.filterIsInstance<TranscriptItem.AssistantMsg>().single()
        assertEquals(1_788_609_600.0, reply.ts)
        assertEquals(18.37, reply.tokensPerSecond)
        assertEquals(9_489, reply.prefillMs)

        val footer = replyFooterText(reply.ts, reply.tokensPerSecond, reply.prefillMs, utc)
        // The clock reading rather than the whole string: the platform's own short-time format
        // differs by JDK and locale, which is the point of asking it for one.
        assertTrue(footer!!.startsWith("read 9.5s · 18.4 tok/s · "), footer)
        assertTrue(footer.contains("12:00"), footer)
    }

    @Test
    fun `the clock stays at the end however much the provider measured`() {
        // What a provider that measures nothing leaves: the time, and nothing in front of it.
        val bare = replyFooterText(1_788_609_600.0, null, null, utc)
        assertTrue(bare!!.contains("12:00"), bare)
        assertTrue(!bare.contains("tok/s") && !bare.contains("read"), bare)
        // Every shape ends with the same thing, which is the whole point of the order: the clock
        // does not move because the session is on a provider that measures more or less.
        val shapes =
            listOf(
                bare,
                replyFooterText(1_788_609_600.0, 18.37, null, utc)!!,
                replyFooterText(1_788_609_600.0, null, 9_489, utc)!!,
                replyFooterText(1_788_609_600.0, 18.37, 9_489, utc)!!,
            )
        assertEquals(1, shapes.map { it.substringAfterLast("· ") }.distinct().size, "$shapes")
        // A reply with nothing to say has no line at all rather than an empty one.
        assertNull(replyFooterText(0.0, null, null, utc))
    }

    @Test
    fun `a block cut by a page boundary is one block, and it is not still going`() {
        // Each page folded on its own, as the app does: the older one holds the fragments before
        // the cut and no ending, the newer one the rest and the ending.
        val older = fold(SessionEvent.Thinking("half a "))
        val newer = fold(SessionEvent.Thinking("thought"), SessionEvent.ThinkingDone(2_000))

        val joined = joinPages(older, newer)
        val block = thinking(joined).single()
        assertEquals("half a thought", block.text)
        assertEquals(2_000, block.ms)
        assertTrue(!block.open)
    }

    @Test
    fun `two blocks meeting at a page boundary stay two`() {
        val older = fold(SessionEvent.Thinking("first"), SessionEvent.ThinkingDone(1_000))
        val newer = fold(SessionEvent.Thinking("second"), SessionEvent.ThinkingDone(2_000))
        assertEquals(listOf("first", "second"), thinking(joinPages(older, newer)).map { it.text })
    }

    @Test
    fun `usage that lands after a tool call is not folded onto an older reply`() {
        val items =
            fold(
                SessionEvent.AssistantText("Reading it."),
                SessionEvent.ToolStart("t1", "Read", "{}"),
                SessionEvent.ToolEnd("t1", "done"),
                SessionEvent.UsageDelta(42, 100, 18.0, 500),
            )
        assertNull(items.filterIsInstance<TranscriptItem.AssistantMsg>().single().tokensPerSecond)
    }
}