package io.oxygenhub.android.ui.issues

import androidx.compose.foundation.background

import androidx.compose.foundation.clickable

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.fillMaxSize

import androidx.compose.foundation.layout.padding

import androidx.compose.foundation.lazy.LazyColumn

import androidx.compose.foundation.lazy.items

import androidx.compose.foundation.rememberScrollState

import androidx.compose.foundation.shape.RoundedCornerShape

import androidx.compose.material.icons.Icons

import androidx.compose.material.icons.outlined.CheckCircle

import androidx.compose.material.icons.outlined.ChatBubbleOutline

import androidx.compose.material.icons.outlined.PushPin

import androidx.compose.material.icons.outlined.RadioButtonUnchecked

import androidx.compose.material.icons.outlined.TaskAlt

import androidx.compose.material3.FilterChip

import androidx.compose.material3.HorizontalDivider

import androidx.compose.material3.Icon

import androidx.compose.material3.ListItem

import androidx.compose.material3.MaterialTheme

import androidx.compose.material3.Text

import androidx.compose.runtime.Composable

import androidx.compose.runtime.getValue

import androidx.compose.ui.Alignment

import androidx.compose.ui.Modifier

import androidx.compose.ui.draw.clip

import androidx.compose.ui.graphics.Color

import androidx.compose.ui.graphics.luminance

import androidx.compose.ui.platform.LocalUriHandler

import androidx.compose.ui.text.style.TextOverflow

import androidx.compose.ui.unit.dp

import androidx.compose.ui.unit.sp

import androidx.lifecycle.compose.collectAsStateWithLifecycle

import io.oxygenhub.android.api.Issue

import io.oxygenhub.android.api.IssueState

import io.oxygenhub.android.api.Label

import io.oxygenhub.android.ui.common.AppScreen

import io.oxygenhub.android.ui.common.EmptyState

import io.oxygenhub.android.ui.common.LoadContent

import io.oxygenhub.android.ui.common.relativeTime

import io.oxygenhub.android.ui.theme.LocalStatusColors

/**

 * A repository's issues. For now this is the repository's whole detail

 * pane; the repository overview (oxygenhub-android#3) will hold it as one

 * of its tabs. An issue opens on the hub's web page until #4 brings the

 * issue screen.

 */

@Composable

fun IssuesScreen(vm: IssuesViewModel, onBack: (() -> Unit)?) {

    val state by vm.state.collectAsStateWithLifecycle()

    val filter by vm.filter.collectAsStateWithLifecycle()

    val uri = LocalUriHandler.current

    AppScreen(title = "${vm.owner}/${vm.name}", subtitle = "Issues", onBack = onBack) {

        Column(Modifier.fillMaxSize()) {

            Row(

                Modifier.horizontalScroll(rememberScrollState()).padding(horizontal = 16.dp),

                horizontalArrangement = Arrangement.spacedBy(8.dp),

            ) {

                IssueState.entries.forEach { s ->

                    FilterChip(selected = filter == s, onClick = { vm.setFilter(s) }, label = { Text(s.name) })

                }

            }

            LoadContent(state, onRefresh = vm::refresh) { issues ->

                if (issues.isEmpty()) {

                    EmptyState(

                        Icons.Outlined.TaskAlt,

                        when (filter) {

                            IssueState.Open -> "No open issues"

                            IssueState.Closed -> "No closed issues"

                            IssueState.All -> "No issues yet"

                        },

                        "Issues for ${vm.owner}/${vm.name} show here.",

                    )

                } else {

                    LazyColumn(Modifier.fillMaxSize()) {

                        items(issues, key = { it.number }) { issue ->

                            IssueRow(issue, onClick = { if (issue.url.isNotBlank()) uri.openUri(issue.url) })

                            HorizontalDivider()

                        }

                    }

                }

            }

        }

    }

}

@Composable

fun IssueRow(issue: Issue, onClick: () -> Unit) {

    val status = LocalStatusColors.current

    ListItem(

        modifier = Modifier.clickable(onClick = onClick),

        leadingContent = {

            if (issue.isOpen) {

                Icon(Icons.Outlined.RadioButtonUnchecked, contentDescription = "Open", tint = status.ok)

            } else {

                Icon(Icons.Outlined.CheckCircle, contentDescription = "Closed", tint = status.warn)

            }

        },

        overlineContent = if (issue.pinned) {

            {

                Row(verticalAlignment = Alignment.CenterVertically) {

                    Icon(Icons.Outlined.PushPin, contentDescription = null, modifier = Modifier.padding(end = 4.dp))

                    Text("Pinned")

                }

            }

        } else {

            null

        },

        headlineContent = { Text(issue.title, maxLines = 2, overflow = TextOverflow.Ellipsis) },

        supportingContent = {

            Column {

                val verb = if (issue.isOpen) "opened" else "closed"

                val at = if (issue.isOpen) issue.createdMs else (issue.closedMs ?: issue.updatedMs)

                Text("#${issue.number} $verb ${relativeTime(at)} by ${issue.author}", maxLines = 1, overflow = TextOverflow.Ellipsis)

                if (issue.labels.isNotEmpty()) {

                    FlowRow(Modifier.padding(top = 4.dp), horizontalArrangement = Arrangement.spacedBy(4.dp), verticalArrangement = Arrangement.spacedBy(4.dp)) {

                        issue.labels.forEach { LabelChip(it) }

                    }

                }

            }

        },

        trailingContent = if (issue.comments > 0) {

            {

                Row(verticalAlignment = Alignment.CenterVertically) {

                    Icon(Icons.Outlined.ChatBubbleOutline, contentDescription = "Comments", modifier = Modifier.padding(end = 4.dp))

                    Text(issue.comments.toString())

                }

            }

        } else {

            null

        },

    )

}

@Composable

private fun LabelChip(label: Label) {

    val colour = parseColour(label.colour) ?: MaterialTheme.colorScheme.secondaryContainer

    val ink = if (colour.luminance() > 0.5f) Color.Black else Color.White

    Text(

        label.name,

        color = ink,

        fontSize = 12.sp,

        modifier = Modifier

            .clip(RoundedCornerShape(50))

            .background(colour)

            .padding(horizontal = 8.dp, vertical = 2.dp),

    )

}

/** `#rrggbb` (or `rrggbb`) to a colour; null for anything else. */

internal fun parseColour(s: String): Color? {

    val hex = s.trim().removePrefix("#")

    if (hex.length != 6) return null

    val v = hex.toLongOrNull(16) ?: return null

    return Color(0xFF000000 or v)

}