package soy.iko.opencode.ui.chat

import androidx.compose.foundation.clickable
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.Row
import androidx.compose.foundation.layout.fillMaxWidth
import androidx.compose.foundation.layout.heightIn
import androidx.compose.foundation.layout.padding
import androidx.compose.foundation.layout.size
import androidx.compose.foundation.lazy.LazyColumn
import androidx.compose.foundation.lazy.items
import androidx.compose.foundation.lazy.rememberLazyListState
import androidx.compose.foundation.text.KeyboardActions
import androidx.compose.foundation.text.KeyboardOptions
import androidx.compose.material.icons.Icons
import androidx.compose.material.icons.filled.Check
import androidx.compose.material.icons.filled.Close
import androidx.compose.material.icons.filled.Search
import androidx.compose.material3.CircularProgressIndicator
import androidx.compose.material3.ExperimentalMaterial3Api
import androidx.compose.material3.Icon
import androidx.compose.material3.IconButton
import androidx.compose.material3.MaterialTheme
import androidx.compose.material3.ModalBottomSheet
import androidx.compose.material3.OutlinedTextField
import androidx.compose.material3.Text
import androidx.compose.material3.TextButton
import androidx.compose.runtime.Composable
import androidx.compose.runtime.LaunchedEffect
import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.remember
import androidx.compose.runtime.saveable.rememberSaveable
import androidx.compose.runtime.setValue
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.focus.FocusRequester
import androidx.compose.ui.focus.focusRequester
import androidx.compose.ui.hapticfeedback.HapticFeedbackType
import androidx.compose.ui.platform.LocalHapticFeedback
import androidx.compose.ui.platform.LocalSoftwareKeyboardController
import androidx.compose.ui.res.stringResource
import androidx.compose.ui.semantics.Role
import androidx.compose.ui.semantics.contentDescription
import androidx.compose.ui.semantics.role
import androidx.compose.ui.semantics.selected
import androidx.compose.ui.semantics.semantics
import androidx.compose.ui.text.input.ImeAction
import androidx.compose.ui.unit.dp
import androidx.compose.foundation.layout.Box
import androidx.compose.foundation.layout.fillMaxHeight
import soy.iko.opencode.data.model.Agent
import soy.iko.opencode.data.network.NetworkConfig
import soy.iko.opencode.R

/**
 * Flat LazyColumn index of the selected agent, offset by the leading "Default" row when it's
 * shown. A null selection targets that Default row (index 0). -1 when the selection isn't in
 * the current list.
 */
/** Whether the synthetic "Default" agent row matches the current search query. */
private fun defaultAgentMatches(query: String, label: String, desc: String): Boolean =
    query.isEmpty() ||
        label.contains(query, ignoreCase = true) ||
        desc.contains(query, ignoreCase = true)

private fun selectedAgentIndex(
    distinctAgents: List<Agent>,
    selected: String?,
    defaultMatches: Boolean,
): Int {
    if (selected == null) return if (defaultMatches) 0 else -1
    val base = if (defaultMatches) 1 else 0
    val pos = distinctAgents.indexOfFirst { it.name == selected }
    return if (pos >= 0) base + pos else -1
}

/** Bottom sheet that lists every agent and lets the user pick one. */
@OptIn(ExperimentalMaterial3Api::class)
@Composable
fun AgentPickerSheet(
    agents: List<Agent>,
    selected: String?,
    loading: Boolean,
    error: Boolean,
    onSelect: (Agent?) -> Unit,
    onRetry: () -> Unit,
    onDismiss: () -> Unit,
) {
    ModalBottomSheet(onDismissRequest = onDismiss) {
        Text(
            stringResource(R.string.agent),
            style = MaterialTheme.typography.titleMedium,
            modifier = Modifier.padding(start = 24.dp, end = 24.dp, bottom = 8.dp),
        )
        if (loading) {
            val loadingLabel = stringResource(R.string.loading)
            Box(
                modifier = Modifier.fillMaxWidth().padding(vertical = 24.dp),
                contentAlignment = Alignment.Center,
            ) {
                CircularProgressIndicator(Modifier.semantics { contentDescription = loadingLabel })
            }
        } else if (error && agents.isEmpty()) {
            Column(
                modifier = Modifier.fillMaxWidth().padding(horizontal = 24.dp, vertical = 16.dp),
                horizontalAlignment = Alignment.CenterHorizontally,
            ) {
                Text(
                    stringResource(R.string.load_failed),
                    style = MaterialTheme.typography.bodyMedium,
                    color = MaterialTheme.colorScheme.error,
                )
                TextButton(onClick = onRetry) { Text(stringResource(R.string.retry)) }
            }
        } else if (agents.isEmpty()) {
            Text(
                stringResource(R.string.no_agents),
                style = MaterialTheme.typography.bodyMedium,
                color = MaterialTheme.colorScheme.onSurfaceVariant,
                modifier = Modifier.padding(horizontal = 24.dp, vertical = 16.dp),
            )
        } else {
            var query by rememberSaveable { mutableStateOf("") }
            val keyboardController = LocalSoftwareKeyboardController.current
            val haptics = LocalHapticFeedback.current
            // Auto-focus the search field (and raise the keyboard) when the sheet opens, but skip
            // it for a short catalog that's faster to scan by eye than to filter.
            val searchFocus = remember { FocusRequester() }
            LaunchedEffect(Unit) {
                if (agents.size > NetworkConfig.pickerSearchAutofocusThreshold) {
                    runCatching { searchFocus.requestFocus() }
                }
            }
            OutlinedTextField(
                value = query,
                onValueChange = { query = it },
                modifier = Modifier.fillMaxWidth().padding(horizontal = 24.dp, vertical = 8.dp).focusRequester(searchFocus),
                placeholder = { Text(stringResource(R.string.search_agents)) },
                leadingIcon = { Icon(Icons.Filled.Search, contentDescription = null) },
                trailingIcon = if (query.isNotEmpty()) {
                    {
                        IconButton(onClick = { query = "" }) {
                            Icon(Icons.Filled.Close, contentDescription = stringResource(R.string.clear_search))
                        }
                    }
                } else null,
                singleLine = true,
                keyboardOptions = KeyboardOptions(imeAction = ImeAction.Search),
                keyboardActions = KeyboardActions(onSearch = { keyboardController?.hide() }),
            )
            val filtered = remember(agents, query) {
                val q = query.trim()
                if (q.isEmpty()) agents
                else agents.filter {
                    it.name.contains(q, ignoreCase = true) ||
                        it.displayDescription.contains(q, ignoreCase = true)
                }
            }
            // The "Default" option participates in the search too: show it when the query is
            // empty or matches its label/description. Without this it either always showed
            // (ignoring the filter) or, when a query matched no named agent, disappeared with
            // the whole list — leaving the default unselectable.
            val defaultLabel = stringResource(R.string.default_agent)
            val defaultDesc = stringResource(R.string.default_agent_desc)
            val q = query.trim()
            val defaultMatches = defaultAgentMatches(q, defaultLabel, defaultDesc)
            if (filtered.isEmpty() && !defaultMatches) {
                Text(
                    stringResource(R.string.no_agents_match, query.trim()),
                    style = MaterialTheme.typography.bodyMedium,
                    color = MaterialTheme.colorScheme.onSurfaceVariant,
                    modifier = Modifier.padding(horizontal = 24.dp, vertical = 16.dp),
                )
            } else {
                val listState = rememberLazyListState()
                val distinctAgents = remember(filtered) { filtered.distinctBy { it.name } }
                // Flat index of the selected agent, offset by the leading "Default" row when
                // it's shown. selected == null targets that Default row (index 0). -1 when the
                // selection isn't in the current list.
                val selectedIndex = remember(distinctAgents, selected, defaultMatches) {
                    selectedAgentIndex(distinctAgents, selected, defaultMatches)
                }
                LaunchedEffect(Unit) {
                    if (selectedIndex >= 0) listState.scrollToItem(selectedIndex)
                }
                // Responsive height: half the viewport rather than a hardcoded 420dp cap, so
                // the sheet doesn't cramp in landscape or leave empty space on a tall phone.
                LazyColumn(state = listState, modifier = Modifier.fillMaxHeight(0.5f)) {
                if (defaultMatches) {
                item(key = "__default") {
                    Column(
                        modifier = Modifier
                            .fillMaxWidth()
                            .semantics(mergeDescendants = true) {
                                if (selected == null) this.selected = true
                            }
                            .clickable(role = Role.RadioButton) {
                                haptics.performHapticFeedback(HapticFeedbackType.TextHandleMove)
                                onSelect(null); onDismiss()
                            }
                            .padding(horizontal = 24.dp, vertical = 12.dp),
                    ) {
                        Row(verticalAlignment = Alignment.CenterVertically) {
                            Text(
                                stringResource(R.string.default_agent),
                                style = MaterialTheme.typography.bodyLarge,
                                color = if (selected == null) MaterialTheme.colorScheme.primary else MaterialTheme.colorScheme.onSurface,
                                modifier = Modifier.weight(1f),
                            )
                            if (selected == null) {
                                Icon(
                                    Icons.Filled.Check,
                                    contentDescription = null,
                                    tint = MaterialTheme.colorScheme.primary,
                                    modifier = Modifier.size(18.dp),
                                )
                            }
                        }
                        Text(
                            stringResource(R.string.default_agent_desc),
                            style = MaterialTheme.typography.bodySmall,
                            color = MaterialTheme.colorScheme.onSurfaceVariant,
                        )
                    }
                }
                }
                // distinctBy the name so a server that returns two agents with the same name
                // (e.g. a built-in colliding with a project-level one) can't crash the list
                // with LazyColumn's "Key was already used".
                // Namespace the agent keys so an agent literally named "__default" can't
                // collide with the sentinel key of the default item above (a duplicate key
                // crashes LazyColumn).
                items(distinctAgents, key = { "agent_" + it.name }) { agent ->
                    val isSelected = agent.name == selected
                    Column(
                        modifier = Modifier
                            .fillMaxWidth()
                            .semantics(mergeDescendants = true) {
                                if (isSelected) this.selected = true
                            }
                            .clickable(role = Role.RadioButton) {
                                haptics.performHapticFeedback(HapticFeedbackType.TextHandleMove)
                                onSelect(agent); onDismiss()
                            }
                            .padding(horizontal = 24.dp, vertical = 12.dp),
                    ) {
                        Row(verticalAlignment = Alignment.CenterVertically) {
                            Text(
                                agent.name,
                                style = MaterialTheme.typography.bodyLarge,
                                color = if (isSelected) MaterialTheme.colorScheme.primary else MaterialTheme.colorScheme.onSurface,
                                modifier = Modifier.weight(1f),
                            )
                            if (isSelected) {
                                Icon(
                                    Icons.Filled.Check,
                                    contentDescription = null,
                                    tint = MaterialTheme.colorScheme.primary,
                                    modifier = Modifier.size(18.dp),
                                )
                            }
                        }
                        Text(
                            agent.displayDescription,
                            style = MaterialTheme.typography.bodySmall,
                            color = MaterialTheme.colorScheme.onSurfaceVariant,
                        )
                    }
                }
            }
            }
        }
    }
}