package io.oxygenhub.android.ui.code

import androidx.compose.foundation.clickable

import androidx.compose.foundation.horizontalScroll

import androidx.compose.foundation.isSystemInDarkTheme

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.fillMaxWidth

import androidx.compose.foundation.layout.padding

import androidx.compose.foundation.layout.width

import androidx.compose.foundation.lazy.LazyColumn

import androidx.compose.foundation.lazy.itemsIndexed

import androidx.compose.foundation.lazy.items

import androidx.compose.foundation.rememberScrollState

import androidx.compose.foundation.text.selection.SelectionContainer

import androidx.compose.material.icons.Icons

import androidx.compose.material.icons.outlined.History

import androidx.compose.material3.FilterChip

import androidx.compose.material3.HorizontalDivider

import androidx.compose.material3.Icon

import androidx.compose.material3.IconButton

import androidx.compose.material3.ListItem

import androidx.compose.material3.MaterialTheme

import androidx.compose.material3.Text

import androidx.compose.material3.TextButton

import androidx.compose.runtime.Composable

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.Modifier

import androidx.compose.ui.text.font.FontFamily

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

import androidx.compose.ui.unit.dp

import androidx.lifecycle.compose.collectAsStateWithLifecycle

import com.mikepenz.markdown.m3.Markdown

import io.oxygenhub.android.api.ChangeSummary

import io.oxygenhub.android.api.FileChange

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

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

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

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

/** A file at a reference: highlighted with line numbers, or rendered when it is Markdown. */

@Composable

fun FileScreen(vm: FileViewModel, onBack: () -> Unit, onOpenHistory: () -> Unit) {

    val state by vm.state.collectAsStateWithLifecycle()

    var rendered by rememberSaveable { mutableStateOf(vm.isMarkdown) }

    AppScreen(

        title = vm.path.substringAfterLast('/'),

        subtitle = "${vm.owner}/${vm.name} · ${vm.ref.take(24)} · ${vm.path}",

        onBack = onBack,

        actions = {

            IconButton(onClick = onOpenHistory) { Icon(Icons.Outlined.History, contentDescription = "This file's history") }

        },

    ) {

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

            Column {

                if (vm.isMarkdown) {

                    Row(Modifier.padding(horizontal = 12.dp), horizontalArrangement = Arrangement.spacedBy(8.dp)) {

                        FilterChip(selected = rendered, onClick = { rendered = true }, label = { Text("Rendered") })

                        FilterChip(selected = !rendered, onClick = { rendered = false }, label = { Text("Source") })

                    }

                }

                if (vm.isMarkdown && rendered) {

                    LazyColumn { item { Box(Modifier.padding(16.dp)) { Markdown(text) } } }

                } else {

                    CodeView(text, vm.path)

                }

            }

        }

    }

}

/** Lines with their numbers, highlighted, scrolling sideways together. */

@Composable

fun CodeView(text: String, path: String) {

    val dark = isSystemInDarkTheme()

    val lines = remember(text, path, dark) { highlightLines(text.trimEnd('\n'), path, dark) }

    val numbers = lines.size.toString().length

    val sideways = rememberScrollState()

    SelectionContainer {

        LazyColumn(Modifier.fillMaxWidth().horizontalScroll(sideways)) {

            itemsIndexed(lines) { i, line ->

                Row {

                    Text(

                        (i + 1).toString(),

                        modifier = Modifier.width((numbers * 9 + 16).dp).padding(end = 8.dp),

                        textAlign = TextAlign.End,

                        fontFamily = FontFamily.Monospace,

                        style = MaterialTheme.typography.bodySmall,

                        color = MaterialTheme.colorScheme.outline,

                    )

                    Text(line, fontFamily = FontFamily.Monospace, style = MaterialTheme.typography.bodySmall, softWrap = false)

                }

            }

        }

    }

}

/** A reference's history, or a file's, newest first. */

@Composable

fun HistoryScreen(vm: HistoryViewModel, onBack: () -> Unit, onOpenChange: (ChangeSummary) -> Unit) {

    val state by vm.state.collectAsStateWithLifecycle()

    AppScreen(title = "History", subtitle = listOfNotNull("${vm.owner}/${vm.name}", vm.ref.take(24), vm.path).joinToString(" · "), onBack = onBack) {

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

            LazyColumn {

                items(page.changes, key = { it.hash }) { c -> ChangeRow(c) { onOpenChange(c) } }

                if (page.hasMore) {

                    item {

                        TextButton(onClick = vm::more, enabled = !page.loadingMore, modifier = Modifier.fillMaxWidth()) {

                            Text(if (page.loadingMore) "Loading…" else page.moreFailed ?: "Older changes (${page.total - page.changes.size} more)")

                        }

                    }

                }

            }

        }

    }

}

@Composable

private fun ChangeRow(c: ChangeSummary, onClick: () -> Unit) {

    ListItem(

        modifier = Modifier.clickable(onClick = onClick),

        headlineContent = { Text(c.subject.ifEmpty { "(no message)" }, maxLines = 2) },

        supportingContent = { Text("${c.author.account ?: c.author.name} · ${relativeTime(c.whenMs)}") },

        trailingContent = { Text(c.short.take(8), fontFamily = FontFamily.Monospace, style = MaterialTheme.typography.labelSmall) },

    )

    HorizontalDivider()

}

/** One change: its message, where it is, and the files it touched, each opening at the change. */

@Composable

fun ChangeScreen(vm: ChangeViewModel, onBack: () -> Unit, onOpenFile: (path: String) -> Unit) {

    val state by vm.state.collectAsStateWithLifecycle()

    val status = LocalStatusColors.current

    AppScreen(title = vm.hash.take(12), subtitle = "${vm.owner}/${vm.name}", onBack = onBack) {

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

            LazyColumn {

                item {

                    Column(Modifier.padding(16.dp), verticalArrangement = Arrangement.spacedBy(6.dp)) {

                        Text(d.change.subject, style = MaterialTheme.typography.titleMedium)

                        Text(

                            "${d.change.author.account ?: d.change.author.name} · ${relativeTime(d.change.whenMs)}",

                            style = MaterialTheme.typography.bodySmall,

                            color = MaterialTheme.colorScheme.onSurfaceVariant,

                        )

                        val rest = d.change.message.lines().drop(1).joinToString("\n").trim()

                        if (rest.isNotEmpty()) Markdown(rest)

                        val where = d.inBookmarks.map { it } + d.inTags.map { "tag $it" }

                        if (where.isNotEmpty()) Text("In " + where.joinToString(", "), style = MaterialTheme.typography.bodySmall)

                    }

                    HorizontalDivider()

                }

                items(d.files, key = { it.path }) { f -> FileRow(f, status.ok, status.bad) { if (f.kind != "removed") onOpenFile(f.path) } }

            }

        }

    }

}

@Composable

private fun FileRow(f: FileChange, added: androidx.compose.ui.graphics.Color, removed: androidx.compose.ui.graphics.Color, onClick: () -> Unit) {

    ListItem(

        modifier = Modifier.clickable(onClick = onClick),

        headlineContent = { Text(f.path) },

        supportingContent = {

            Text(

                when (f.kind) {

                    "renamed" -> "renamed from ${f.from}"

                    else -> f.kind

                },

            )

        },

        trailingContent = {

            Row(horizontalArrangement = Arrangement.spacedBy(6.dp)) {

                Text("+${f.added}", color = added, style = MaterialTheme.typography.labelMedium)

                Text("−${f.removed}", color = removed, style = MaterialTheme.typography.labelMedium)

            }

        },

    )

}