package io.oxygenhub.android.ui.common

import android.text.format.DateUtils

import androidx.compose.foundation.layout.Arrangement

import androidx.compose.foundation.layout.Box

import androidx.compose.foundation.layout.Column

import androidx.compose.foundation.layout.Spacer

import androidx.compose.foundation.layout.fillMaxSize

import androidx.compose.foundation.layout.height

import androidx.compose.foundation.layout.padding

import androidx.compose.foundation.layout.size

import androidx.compose.material.icons.Icons

import androidx.compose.material.icons.outlined.CloudOff

import androidx.compose.material3.Button

import androidx.compose.material3.CircularProgressIndicator

import androidx.compose.material3.ExperimentalMaterial3Api

import androidx.compose.material3.Icon

import androidx.compose.material3.MaterialTheme

import androidx.compose.material3.Text

import androidx.compose.material3.pulltorefresh.PullToRefreshBox

import androidx.compose.runtime.Composable

import androidx.compose.ui.Alignment

import androidx.compose.ui.Modifier

import androidx.compose.ui.graphics.vector.ImageVector

import androidx.compose.ui.text.style.TextAlign

import androidx.compose.ui.unit.dp

import io.oxygenhub.android.ui.backdrop.Backdrop

import io.oxygenhub.android.ui.theme.Tones

import uniffi.rust_core.Backdrop as Scene

/** A spinner in the middle of the space. */

@Composable

fun LoadingState(modifier: Modifier = Modifier) {

    Box(modifier.fillMaxSize(), contentAlignment = Alignment.Center) {

        CircularProgressIndicator()

    }

}

/** Nothing to show, said plainly, with an icon. */

@Composable

fun EmptyState(

    icon: ImageVector,

    title: String,

    body: String,

    modifier: Modifier = Modifier,

    action: (@Composable () -> Unit)? = null,

) {

    Message(icon, title, body, modifier) {

        if (action != null) {

            Spacer(Modifier.height(8.dp))

            action()

        }

    }

}

/** What went wrong, and a way to try again. */

@Composable

fun ErrorState(message: String, onRetry: () -> Unit, modifier: Modifier = Modifier) {

    Message(Icons.Outlined.CloudOff, "Couldn't load this", message, modifier) {

        Spacer(Modifier.height(16.dp))

        Button(onClick = onRetry) { Text("Try again") }

    }

}

@Composable

private fun Message(

    icon: ImageVector,

    title: String,

    body: String,

    modifier: Modifier = Modifier,

    extra: @Composable () -> Unit = {},

) {

    // The quiet field behind it, as behind the hub's error pages (#23).

    Backdrop(key = Unit, make = { still -> Scene.adrift(still) }, modifier = modifier.fillMaxSize()) {

        Column(

            Modifier.fillMaxSize().padding(32.dp),

            horizontalAlignment = Alignment.CenterHorizontally,

            verticalArrangement = Arrangement.Center,

        ) {

            Icon(icon, contentDescription = null, modifier = Modifier.size(48.dp), tint = Tones.info.copy(alpha = 0.85f))

            Spacer(Modifier.height(16.dp))

            Text(title, style = MaterialTheme.typography.titleMedium, textAlign = TextAlign.Center)

            Spacer(Modifier.height(8.dp))

            Text(body, style = MaterialTheme.typography.bodyMedium, color = MaterialTheme.colorScheme.onSurfaceVariant, textAlign = TextAlign.Center)

            extra()

        }

    }

}

/**

 * The usual body of a screen over a [Load]: a spinner, the error with a

 * retry, or [content] in a pull-to-refresh box.

 */

@OptIn(ExperimentalMaterial3Api::class)

@Composable

fun <T> LoadContent(

    load: Load<T>,

    onRefresh: () -> Unit,

    modifier: Modifier = Modifier,

    content: @Composable (T) -> Unit,

) {

    when (load) {

        Load.Loading -> LoadingState(modifier)

        is Load.Failed -> ErrorState(load.message, onRefresh, modifier)

        is Load.Ready -> PullToRefreshBox(isRefreshing = load.refreshing, onRefresh = onRefresh, modifier = modifier.fillMaxSize()) {

            content(load.value)

        }

    }

}

/** "3 hours ago", from milliseconds since the epoch. */

fun relativeTime(ms: Long, now: Long = System.currentTimeMillis()): String =

    if (ms <= 0) "" else DateUtils.getRelativeTimeSpanString(ms, now, DateUtils.MINUTE_IN_MILLIS).toString()