package com.example.aiapp

import androidx.compose.foundation.BorderStroke
import androidx.compose.foundation.horizontalScroll
import androidx.compose.foundation.layout.Arrangement
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.FlowRow
import androidx.compose.foundation.layout.Row
import androidx.compose.foundation.layout.Spacer
import androidx.compose.foundation.layout.fillMaxWidth
import androidx.compose.foundation.layout.height
import androidx.compose.foundation.layout.padding
import androidx.compose.foundation.layout.width
import androidx.compose.foundation.rememberScrollState
import androidx.compose.material3.Button
import androidx.compose.material3.ButtonDefaults
import androidx.compose.material3.CardDefaults
import androidx.compose.material3.CircularProgressIndicator
import androidx.compose.material3.LocalContentColor
import androidx.compose.material3.MaterialTheme
import androidx.compose.material3.OutlinedButton
import androidx.compose.material3.OutlinedCard
import androidx.compose.material3.OutlinedTextField
import androidx.compose.material3.Surface
import androidx.compose.material3.Text
import androidx.compose.runtime.Composable
import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableIntStateOf
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.remember
import androidx.compose.runtime.setValue
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.text.font.FontFamily
import androidx.compose.ui.unit.dp

/** One question's answer on its way back, so a card can hand over several at once. */
data class QuestionAnswer(val questionId: String, val answers: List<String>)

/**
 * What the reader has settled on for one question, before any of it is sent.
 *
 * Held here rather than inferred from the transcript, which is what made picking an option feel
 * broken: the mark used to appear only when the answer had crossed the tunnel and come back as an
 * event, so the card sat unchanged for most of a second after a tap.
 *
 * Picked options and typed words are one field each because they are alternatives rather than
 * parts: typing puts the picks away and picking puts the words away, so there is never a draft that
 * means two things.
 */
data class Draft(val picked: Set<String> = emptySet(), val other: String = "") {
    val settled: Boolean
        get() = picked.isNotEmpty() || other.isNotBlank()

    /**
     * What goes back, in the order the options were offered rather than the order they were tapped:
     * the reader is answering a list, and it should read back as that list.
     */
    fun answers(options: List<QuestionOption>): List<String> =
        if (other.isNotBlank()) listOf(other.trim())
        else options.map { it.label }.filter { it in picked }
}

/**
 * Every question one tool call is waiting on, one at a time.
 *
 * All of it comes from the question events themselves. None of it is read out of the call's own
 * input, which is one provider's JSON: parsing that here would put that provider's schema in the
 * app, where no other provider can reach it and where it drifts the first time the schema moves.
 *
 * One question on screen with arrows to the others, rather than all of them stacked. A card asking
 * three questions with four options and a description each is several screens tall, so the reader
 * scrolls past the question they are answering to reach the button that sends it. Paged, each
 * question is a screen and the count says how many are left.
 *
 * Nothing is sent until Submit. Answering is one act even when it is several questions: the tool
 * asked them together, and sending each as it was tapped meant the reader could not change their
 * mind about the first after reading the third.
 */
@Composable
fun AskUserQuestionBody(
    asks: List<TranscriptItem.QuestionCard>,
    onAnswer: (List<QuestionAnswer>, onSettled: () -> Unit) -> Unit,
) {
    // Seeded from what was already answered, so a card the reader comes back to shows their answers
    // rather than an empty draft over them.
    var drafts by
        remember(asks.map { it.id }) {
            mutableStateOf(
                asks.associate { ask ->
                    ask.id to
                        Draft(
                            picked =
                                ask.answers
                                    .filter { a -> ask.options.any { it.label == a } }
                                    .toSet(),
                            other =
                                ask.answers
                                    .firstOrNull { a -> ask.options.none { it.label == a } }
                                    .orEmpty(),
                        )
                }
            )
        }
    var at by remember(asks.map { it.id }) { mutableIntStateOf(0) }
    var sending by remember(asks.map { it.id }) { mutableStateOf(false) }
    if (asks.isEmpty()) return
    val showing = asks[at.coerceIn(0, asks.size - 1)]
    val outstanding = asks.filter { it.answers.isEmpty() }

    Column(Modifier.fillMaxWidth()) {
        if (asks.size > 1) {
            Row(
                verticalAlignment = Alignment.CenterVertically,
                modifier = Modifier.fillMaxWidth(),
            ) {
                Text(
                    "Question ${at + 1} of ${asks.size}",
                    style = MaterialTheme.typography.labelSmall,
                    color = MaterialTheme.colorScheme.onSurfaceVariant,
                    modifier = Modifier.weight(1f),
                )
                // Disabled at the ends rather than absent, so the pair keeps its place and the
                // reader can see there is nothing further that way.
                MarkButton("Previous question", { at-- }, enabled = at > 0) {
                    Chevron(Pointing.Left, colour = LocalContentColor.current)
                }
                MarkButton("Next question", { at++ }, enabled = at < asks.size - 1) {
                    Chevron(Pointing.Right, colour = LocalContentColor.current)
                }
            }
        }
        Spacer(Modifier.height(4.dp))
        AskedQuestion(
            showing,
            draft = drafts[showing.id] ?: Draft(),
            onDraft = { drafts = drafts + (showing.id to it) },
        )
        if (outstanding.isNotEmpty()) {
            Spacer(Modifier.height(12.dp))
            // Greyed until every question has an answer, because the tool is waiting on all of
            // them: a submit that sent two of three would leave the third asked and the card
            // looking dealt with.
            val ready = outstanding.all { drafts[it.id]?.settled == true }
            Button(
                onClick = {
                    sending = true
                    onAnswer(
                        outstanding.map { ask ->
                            QuestionAnswer(ask.id, (drafts[ask.id] ?: Draft()).answers(ask.options))
                        }
                    ) {
                        // Back to a button whatever happened. A refusal is reported by the screen
                        // around this, and the draft is still here to send again -- a spinner that
                        // never stops would be the only sign of a failure this card cannot
                        // describe.
                        sending = false
                    }
                },
                enabled = ready && !sending,
                modifier = Modifier.fillMaxWidth(),
            ) {
                if (sending) {
                    // In the button rather than beside it, so the row does not change height at the
                    // moment it is pressed.
                    CircularProgressIndicator(
                        Modifier.height(18.dp).width(18.dp),
                        strokeWidth = 2.dp,
                        color = LocalContentColor.current,
                    )
                } else {
                    Text(
                        if (outstanding.size > 1) "Submit ${outstanding.size} answers" else "Submit"
                    )
                }
            }
        }
    }
}

/**
 * One question: what is being asked, what can be answered, and what was.
 *
 * The same body wherever a question appears -- on the call that asked it, or as a card of its own
 * when nothing did. Two renderings of it would be two places for an answer to go missing.
 *
 * [draft] is what the reader has picked so far and [onDraft] is how they change it; nothing here
 * sends anything. An answered question ignores both and draws what was answered.
 */
@Composable
fun AskedQuestion(
    ask: TranscriptItem.QuestionCard,
    draft: Draft,
    onDraft: (Draft) -> Unit,
) {
    Column(Modifier.fillMaxWidth()) {
        ask.header?.let { header ->
            // Its own line rather than beside the question, because it is a label *for* the
            // question and the question is the thing to read.
            Text(
                header.uppercase(),
                style = MaterialTheme.typography.labelSmall,
                color = MaterialTheme.colorScheme.onSurfaceVariant,
            )
        }
        Text(ask.prompt, style = MaterialTheme.typography.bodyLarge)
        Spacer(Modifier.height(8.dp))
        // An answered question keeps its options and marks the one that was taken, rather than
        // replacing them with a line repeating it. The options are what the question *was*, and
        // dropping them leaves an answer with nothing to have been an answer to -- "Sonnet" says
        // very little without the three it was chosen over. Marked in the same purple that says
        // "picked" while the question is open, so it is one appearance learned once.
        val answered = ask.answers.isNotEmpty()
        // What is marked: what was answered once there is an answer, and what the finger has chosen
        // until then.
        val marked = if (answered) ask.answers.toSet() else draft.picked
        // Null once the question is answered: the options stay and stop being pressable.
        val onPick: ((String) -> Unit)? =
            if (answered) null else { label -> onDraft(pick(draft, label, ask.multiSelect)) }
        if (ask.options.all { it.description == null && it.preview == null }) {
            // Nothing to read, so nothing to lay out: Allow and Deny are two words, and two words
            // do not need a card each.
            AnswerOptions(ask.options, marked.toList(), onPick)
        } else {
            ask.options.forEach { option ->
                OptionCard(option, selected = option.label in marked) {
                    onPick?.invoke(option.label)
                }
            }
        }
        // What was answered in the reader's own words, which no option can mark. Only ever the
        // answers that match nothing offered, so a question answered by picking says it by the
        // mark.
        val inWords = ask.answers.filterNot { answer -> ask.options.any { it.label == answer } }
        if (inWords.isNotEmpty()) {
            Text(
                "Answered: ${inWords.joinToString(", ")}",
                style = MaterialTheme.typography.labelLarge,
                color = MaterialTheme.colorScheme.primary,
                modifier = Modifier.padding(top = 8.dp),
            )
        }
        if (!answered) {
            OtherAnswer(draft.other) { onDraft(Draft(other = it)) }
        }
    }
}

/**
 * [label] added to, or taken out of, what [draft] has picked. A single-answer question replaces
 * rather than accumulates, and either way picking puts any typed words away -- see [Draft].
 */
private fun pick(draft: Draft, label: String, multiSelect: Boolean): Draft =
    when {
        !multiSelect -> Draft(picked = setOf(label))
        label in draft.picked -> Draft(picked = draft.picked - label)
        else -> Draft(picked = draft.picked + label)
    }

/**
 * One option: what it is called, what it means, and what it would produce.
 *
 * Outlined rather than tinted. Drawn first as a card one step up the surface ladder, it was
 * indistinguishable from the card behind it -- three paragraphs of text where three things to press
 * should have been. A border is one cue and it is unambiguous.
 */
@Composable
private fun OptionCard(option: QuestionOption, selected: Boolean, onPick: () -> Unit) {
    OutlinedCard(
        onClick = onPick,
        modifier = Modifier.fillMaxWidth().padding(top = 6.dp),
        colors =
            CardDefaults.outlinedCardColors(
                containerColor =
                    if (selected) MaterialTheme.colorScheme.primaryContainer
                    else MaterialTheme.colorScheme.surface
            ),
        // Picked shows in the border as well as the fill, because the fill alone is a colour
        // difference somebody has to have seen the unpicked version to notice.
        border =
            BorderStroke(
                if (selected) 2.dp else 1.dp,
                if (selected) MaterialTheme.colorScheme.primary
                else MaterialTheme.colorScheme.outlineVariant,
            ),
    ) {
        Column(Modifier.padding(12.dp)) {
            Text(option.label, style = MaterialTheme.typography.titleSmall)
            option.description?.let {
                Text(
                    it,
                    style = MaterialTheme.typography.bodySmall,
                    color = MaterialTheme.colorScheme.onSurfaceVariant,
                    modifier = Modifier.padding(top = 2.dp),
                )
            }
            option.preview?.let { Preview(it) }
        }
    }
}

/**
 * An option's worked example, shown as written.
 *
 * On its own surface, because it is a different kind of thing from the sentence above it: that
 * describes the option, this is a sample of what the option produces, and monospace alone reads as
 * a description that happens to be in code font.
 */
@Composable
private fun Preview(preview: String) {
    Surface(
        color = MaterialTheme.colorScheme.surfaceContainerLowest,
        modifier = Modifier.fillMaxWidth().padding(top = 8.dp),
    ) {
        Text(
            preview,
            style = MaterialTheme.typography.bodySmall,
            fontFamily = FontFamily.Monospace,
            // Not wrapped: these are mockups and diffs, where a wrapped line reads as two lines of
            // the thing being previewed.
            softWrap = false,
            modifier = Modifier.padding(8.dp).horizontalScroll(rememberScrollState()),
        )
    }
}

/**
 * The choice the asker always leaves open, and the app has to as well.
 *
 * Every AskUserQuestion carries an implicit "Other" -- the reader may answer in their own words
 * rather than pick. Leaving it out narrows a question that was never that narrow.
 */
@Composable
private fun OtherAnswer(text: String, onText: (String) -> Unit) {
    // No Send of its own: this is one more way to answer the question, and the card's Submit is
    // what sends it. A second send button beside the field made the shorter half of the card look
    // like the one that finishes it.
    OutlinedTextField(
        value = text,
        onValueChange = onText,
        label = { Text("Other") },
        singleLine = true,
        modifier = Modifier.fillMaxWidth().padding(top = 8.dp),
    )
}

/**
 * Bare options, wrapped rather than in a row.
 *
 * A Row hands out intrinsic widths in order and clips whatever runs past the edge, so a question
 * with four options showed the first one or two and dropped the rest off the side of the screen.
 * That reads as those having been the only choices.
 */
@Composable
fun AnswerOptions(
    options: List<QuestionOption>,
    /** What is chosen: the answer once there is one, and what the finger has marked until then. */
    answers: List<String> = emptyList(),
    /** Null once the question is answered -- the buttons stay, and stop being buttons. */
    onPick: ((String) -> Unit)?,
) {
    FlowRow(
        horizontalArrangement = Arrangement.spacedBy(8.dp),
        verticalArrangement = Arrangement.spacedBy(4.dp),
        modifier = Modifier.fillMaxWidth(),
    ) {
        options.forEach { option ->
            val taken = option.label in answers
            OutlinedButton(
                onClick = { onPick?.invoke(option.label) },
                // Disabled rather than removed, so an answered question still shows what it
                // offered. Material dims a disabled button's own border and label, which would take
                // the mark with it -- both are stated here instead.
                enabled = onPick != null,
                border =
                    BorderStroke(
                        if (taken) 2.dp else 1.dp,
                        if (taken) MaterialTheme.colorScheme.primary
                        else MaterialTheme.colorScheme.outlineVariant,
                    ),
                colors =
                    ButtonDefaults.outlinedButtonColors(
                        disabledContentColor =
                            if (taken) MaterialTheme.colorScheme.primary
                            else MaterialTheme.colorScheme.onSurfaceVariant
                    ),
            ) {
                Text(option.label)
            }
        }
    }
}