package com.example.aiapp

import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.Row
import androidx.compose.foundation.layout.Spacer
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.rememberScrollState
import androidx.compose.foundation.verticalScroll
import androidx.compose.material3.Card
import androidx.compose.material3.CircularProgressIndicator
import androidx.compose.material3.LinearProgressIndicator
import androidx.compose.material3.MaterialTheme
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.rememberCoroutineScope
import androidx.compose.runtime.setValue
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.unit.dp
import java.time.Duration
import java.time.OffsetDateTime
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.launch
import kotlinx.coroutines.withContext

private val WARN_COLOR = Color(0xFFB26A00)
private val OVER_COLOR = Color(0xFFB3261E)

/** Window bars for the account's rate limits, with reset times. */
@Composable
fun UsageScreen(settings: ServerSettings, onBack: () -> Unit) {
    val scope = rememberCoroutineScope()
    var state by remember { mutableStateOf<LoadState<List<UsageSnapshot>>>(LoadState.Loading) }

    fun refresh() {
        state = LoadState.Loading
        scope.launch {
            state =
                try {
                    withContext(Dispatchers.IO) { LoadState.Loaded(fetchUsage(settings)) }
                } catch (e: ApiException) {
                    LoadState.failed(e)
                }
        }
    }
    LaunchedEffect(Unit) { refresh() }

    Column(Modifier.fillMaxSize().verticalScroll(rememberScrollState()).padding(16.dp)) {
        Row(verticalAlignment = Alignment.CenterVertically, modifier = Modifier.fillMaxWidth()) {
            Text(
                "Usage",
                style = MaterialTheme.typography.headlineSmall,
                modifier = Modifier.weight(1f),
            )
            TextButton(onClick = onBack) { Text("Back") }
            TextButton(onClick = { refresh() }) { Text("Refresh") }
        }
        Spacer(Modifier.height(16.dp))

        when (val current = state) {
            is LoadState.Loading -> CircularProgressIndicator()
            is LoadState.Error -> Text(current.message, color = MaterialTheme.colorScheme.error)
            is LoadState.Loaded ->
                current.value.forEach { snapshot ->
                    Card(Modifier.fillMaxWidth()) {
                        Column(Modifier.padding(16.dp)) {
                            Text(snapshot.provider, style = MaterialTheme.typography.titleMedium)
                            Spacer(Modifier.height(8.dp))
                            if (!snapshot.available) {
                                Text(
                                    snapshot.error ?: "Unavailable",
                                    color = MaterialTheme.colorScheme.error,
                                    style = MaterialTheme.typography.bodyMedium,
                                )
                            }
                            snapshot.windows.forEach { window ->
                                WindowBar(window)
                                Spacer(Modifier.height(12.dp))
                            }
                        }
                    }
                    Spacer(Modifier.height(12.dp))
                }
        }
    }
}

@Composable
private fun WindowBar(window: UsageWindow) {
    val color =
        when {
            window.percent >= 95 -> OVER_COLOR
            window.percent >= 75 -> WARN_COLOR
            else -> MaterialTheme.colorScheme.primary
        }
    Column {
        Row(modifier = Modifier.fillMaxWidth()) {
            Text(
                window.label + if (window.active) " (active)" else "",
                style = MaterialTheme.typography.bodyMedium,
                modifier = Modifier.weight(1f),
            )
            Text("${window.percent.toInt()}%", style = MaterialTheme.typography.bodyMedium)
        }
        Spacer(Modifier.height(4.dp))
        LinearProgressIndicator(
            progress = { (window.percent / 100.0).toFloat().coerceIn(0f, 1f) },
            color = color,
            modifier = Modifier.fillMaxWidth(),
        )
        window.resetsAt?.let {
            Spacer(Modifier.height(2.dp))
            Text(
                "resets ${formatReset(it)}",
                style = MaterialTheme.typography.bodySmall,
                color = MaterialTheme.colorScheme.onSurfaceVariant,
            )
        }
    }
}

/** "in 3h 12m" -- close enough for deciding whether to start a big task. */
private fun formatReset(resetsAt: String): String =
    try {
        val until = Duration.between(OffsetDateTime.now(), OffsetDateTime.parse(resetsAt))
        when {
            until.isNegative -> "soon"
            until.toHours() >= 24 -> "in ${until.toDays()}d ${until.toHours() % 24}h"
            until.toHours() > 0 -> "in ${until.toHours()}h ${until.toMinutes() % 60}m"
            else -> "in ${until.toMinutes()}m"
        }
    } catch (_: Exception) {
        "at $resetsAt"
    }