package agzam.vyatsu.ui.picker

import agzam.vyatsu.domain.model.Group
import agzam.vyatsu.domain.model.Teacher
import androidx.compose.foundation.clickable
import androidx.compose.foundation.layout.Arrangement
import androidx.compose.foundation.layout.Box
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.Row
import androidx.compose.foundation.layout.Spacer
import androidx.compose.foundation.layout.WindowInsets
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.foundation.layout.fillMaxWidth
import androidx.compose.foundation.layout.height
import androidx.compose.foundation.layout.padding
import androidx.compose.foundation.layout.systemBars
import androidx.compose.foundation.layout.windowInsetsPadding
import androidx.compose.foundation.lazy.LazyColumn
import androidx.compose.foundation.lazy.items
import androidx.compose.material.icons.Icons
import androidx.compose.material.icons.filled.Clear
import androidx.compose.material.icons.filled.Refresh
import androidx.compose.material.icons.filled.Search
import androidx.compose.material3.CircularProgressIndicator
import androidx.compose.material3.ExperimentalMaterial3Api
import androidx.compose.material3.HorizontalDivider
import androidx.compose.material3.Icon
import androidx.compose.material3.IconButton
import androidx.compose.material3.LinearProgressIndicator
import androidx.compose.material3.MaterialTheme
import androidx.compose.material3.Scaffold
import androidx.compose.material3.SearchBar
import androidx.compose.material3.SearchBarDefaults
import androidx.compose.material3.SegmentedButton
import androidx.compose.material3.SegmentedButtonDefaults
import androidx.compose.material3.SingleChoiceSegmentedButtonRow
import androidx.compose.material3.Text
import androidx.compose.material3.TextButton
import androidx.compose.runtime.Composable
import androidx.compose.runtime.LaunchedEffect
import androidx.compose.runtime.collectAsState
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.unit.dp

@OptIn(ExperimentalMaterial3Api::class)
@Composable
fun PickerScreen(
    viewModel: PickerViewModel,
    onGroupPicked: (Group) -> Unit,
    onTeacherPicked: (Teacher) -> Unit
) {
    val state by viewModel.uiState.collectAsState()
    var segment by rememberSaveable { mutableStateOf(PickerSegment.GROUPS) }
    LaunchedEffect(segment) { viewModel.selectSegment(segment) }

    Scaffold { innerPadding ->
        Column(
            Modifier
                .fillMaxSize()
                .windowInsetsPadding(WindowInsets.systemBars)
                .padding(innerPadding)
                .padding(horizontal = 16.dp, vertical = 8.dp)
        ) {
            SingleChoiceSegmentedButtonRow(Modifier.fillMaxWidth()) {
                SegmentedButton(
                    selected = segment == PickerSegment.GROUPS,
                    onClick = { segment = PickerSegment.GROUPS },
                    shape = SegmentedButtonDefaults.itemShape(index = 0, count = 2)
                ) {
                    Text("Группы")
                }
                SegmentedButton(
                    selected = segment == PickerSegment.TEACHERS,
                    onClick = { segment = PickerSegment.TEACHERS },
                    shape = SegmentedButtonDefaults.itemShape(index = 1, count = 2)
                ) {
                    Text("Преподаватели")
                }
            }

            Spacer(Modifier.height(16.dp))

            when (segment) {
                PickerSegment.GROUPS -> GroupSection(
                    state = state,
                    onSearch = viewModel::searchGroup,
                    onRetry = viewModel::retryGroups,
                    onRefresh = viewModel::refreshGroups,
                    onGroupPicked = onGroupPicked
                )
                PickerSegment.TEACHERS -> TeacherSection(
                    state = state,
                    onSearch = viewModel::searchTeacher,
                    onRetry = viewModel::retryTeachers,
                    onTeacherPicked = onTeacherPicked
                )
            }
        }
    }
}

@OptIn(ExperimentalMaterial3Api::class)
@Composable
private fun GroupSection(
    state: PickerUiState,
    onSearch: (String) -> Unit,
    onRetry: () -> Unit,
    onRefresh: () -> Unit,
    onGroupPicked: (Group) -> Unit
) {
    var isSearchActive by remember { mutableStateOf(false) }

    if (!isSearchActive) {
        Row(
            Modifier
                .fillMaxWidth()
                .padding(bottom = 8.dp),
            verticalAlignment = Alignment.CenterVertically
        ) {
            Text(
                text = "Выберите группу",
                style = MaterialTheme.typography.headlineSmall,
                modifier = Modifier.weight(1f)
            )
            IconButton(onClick = onRefresh) {
                Icon(Icons.Default.Refresh, contentDescription = "Обновить")
            }
        }
    }

    if (state.groupsLoading && state.groups.isEmpty()) {
        Row(Modifier.fillMaxWidth(), horizontalArrangement = Arrangement.Center) {
            CircularProgressIndicator()
        }
        return
    }
    if (state.error != null && state.groups.isEmpty()) {
        Column(Modifier.fillMaxWidth()) {
            Text(
                state.error,
                style = MaterialTheme.typography.bodyMedium,
                color = MaterialTheme.colorScheme.error
            )
            TextButton(onClick = onRetry) { Text("Повторить") }
        }
        return
    }
    SearchBar(
        modifier = Modifier.fillMaxWidth(),
        expanded = isSearchActive,
        onExpandedChange = { isSearchActive = it },
        inputField = {
            SearchBarDefaults.InputField(
                query = state.groupQuery,
                onQueryChange = onSearch,
                onSearch = { isSearchActive = false },
                expanded = isSearchActive,
                onExpandedChange = { isSearchActive = it },
                placeholder = { Text("Поиск группы") },
                leadingIcon = { Icon(Icons.Default.Search, contentDescription = null) },
                trailingIcon = {
                    if (isSearchActive && state.groupQuery.isNotEmpty()) {
                        IconButton(onClick = { onSearch("") }) {
                            Icon(Icons.Default.Clear, contentDescription = "Очистить")
                        }
                    }
                }
            )
        }
    ) {
        GroupList(
            groups = state.filteredGroups,
            onPick = { group ->
                isSearchActive = false
                onGroupPicked(group)
            }
        )
    }

    if (!isSearchActive) {
        Spacer(modifier = Modifier.height(8.dp))
        GroupList(state.filteredGroups, onGroupPicked)
    }
}

@Composable
private fun GroupList(groups: List<Group>, onPick: (Group) -> Unit) {
    LazyColumn(modifier = Modifier.fillMaxSize()) {
        items(groups) { group ->
            Column(modifier = Modifier.fillMaxWidth().clickable { onPick(group) }) {
                Box(
                    modifier = Modifier
                        .fillMaxWidth()
                        .padding(horizontal = 16.dp, vertical = 8.dp),
                    contentAlignment = Alignment.CenterStart
                ) {
                    Text(group.name, style = MaterialTheme.typography.bodyMedium)
                }
            }
            HorizontalDivider(thickness = 1.dp, color = MaterialTheme.colorScheme.outlineVariant)
        }
    }
}

@OptIn(ExperimentalMaterial3Api::class)
@Composable
private fun TeacherSection(
    state: PickerUiState,
    onSearch: (String) -> Unit,
    onRetry: () -> Unit,
    onTeacherPicked: (Teacher) -> Unit
) {
    var isSearchActive by remember { mutableStateOf(false) }
    val progress = state.syncProgress
    val syncing = progress != null && progress.done < progress.total

    if (!isSearchActive) {
        Row(
            Modifier
                .fillMaxWidth()
                .padding(bottom = 8.dp),
            verticalAlignment = Alignment.CenterVertically
        ) {
            Text(
                text = "Выберите преподавателя",
                style = MaterialTheme.typography.headlineSmall,
                modifier = Modifier.weight(1f)
            )
            IconButton(onClick = onRetry) {
                Icon(Icons.Default.Refresh, contentDescription = "Обновить")
            }
        }
    }

    if (syncing) {
        Column(Modifier.fillMaxWidth().padding(vertical = 8.dp)) {
            LinearProgressIndicator(
                progress = { progress.done / progress.total.toFloat() },
                modifier = Modifier.fillMaxWidth()
            )
            Spacer(Modifier.height(4.dp))
            Text(
                text = "Кафедры: ${progress.done}/${progress.total}",
                style = MaterialTheme.typography.bodySmall,
                color = MaterialTheme.colorScheme.onSurfaceVariant
            )
        }
    }

    if (state.teachersLoading && state.teachers.isEmpty() && !syncing) {
        Row(Modifier.fillMaxWidth(), horizontalArrangement = Arrangement.Center) {
            CircularProgressIndicator()
        }
        return
    }
    if (state.error != null && state.teachers.isEmpty() && !syncing) {
        Column(Modifier.fillMaxWidth()) {
            Text(
                state.error,
                style = MaterialTheme.typography.bodyMedium,
                color = MaterialTheme.colorScheme.error
            )
            TextButton(onClick = onRetry) { Text("Повторить") }
        }
        return
    }
    SearchBar(
        modifier = Modifier.fillMaxWidth(),
        expanded = isSearchActive,
        onExpandedChange = { isSearchActive = it },
        inputField = {
            SearchBarDefaults.InputField(
                query = state.teacherQuery,
                onQueryChange = onSearch,
                onSearch = { isSearchActive = false },
                expanded = isSearchActive,
                onExpandedChange = { isSearchActive = it },
                placeholder = { Text("Поиск преподавателя") },
                leadingIcon = { Icon(Icons.Default.Search, contentDescription = null) },
                trailingIcon = {
                    if (isSearchActive && state.teacherQuery.isNotEmpty()) {
                        IconButton(onClick = { onSearch("") }) {
                            Icon(Icons.Default.Clear, contentDescription = "Очистить")
                        }
                    }
                }
            )
        }
    ) {
        TeacherList(
            teachers = state.filteredTeachers,
            onPick = { teacher ->
                isSearchActive = false
                onTeacherPicked(teacher)
            }
        )
    }

    if (!isSearchActive) {
        Spacer(modifier = Modifier.height(8.dp))
        when {
            state.teachers.isEmpty() -> Text(
                text = "Кафедры без расписания на эту неделю",
                style = MaterialTheme.typography.bodyMedium,
                color = MaterialTheme.colorScheme.onSurfaceVariant,
                modifier = Modifier.padding(horizontal = 16.dp, vertical = 8.dp)
            )
            else -> TeacherList(state.filteredTeachers, onTeacherPicked)
        }
    }
}

@Composable
private fun TeacherList(teachers: List<Teacher>, onPick: (Teacher) -> Unit) {
    LazyColumn(modifier = Modifier.fillMaxSize()) {
        items(teachers) { teacher ->
            Column(modifier = Modifier.fillMaxWidth().clickable { onPick(teacher) }) {
                Box(
                    modifier = Modifier
                        .fillMaxWidth()
                        .padding(horizontal = 16.dp, vertical = 8.dp),
                    contentAlignment = Alignment.CenterStart
                ) {
                    Text(teacher.name, style = MaterialTheme.typography.bodyMedium)
                }
            }
            HorizontalDivider(thickness = 1.dp, color = MaterialTheme.colorScheme.outlineVariant)
        }
    }
}