package org.terst.feedreader.ui

import androidx.activity.compose.rememberLauncherForActivityResult
import androidx.activity.result.contract.ActivityResultContracts
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.Spacer
import androidx.compose.foundation.layout.fillMaxWidth
import androidx.compose.foundation.layout.height
import androidx.compose.foundation.layout.padding
import androidx.compose.foundation.lazy.LazyColumn
import androidx.compose.material.icons.Icons
import androidx.compose.material.icons.filled.ArrowBack
import androidx.compose.material3.Button
import androidx.compose.material3.ExperimentalMaterial3Api
import androidx.compose.material3.Icon
import androidx.compose.material3.IconButton
import androidx.compose.material3.OutlinedButton
import androidx.compose.material3.OutlinedTextField
import androidx.compose.material3.Scaffold
import androidx.compose.material3.Text
import androidx.compose.material3.TopAppBar
import androidx.compose.runtime.Composable
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.Modifier
import androidx.compose.ui.platform.LocalContext
import androidx.compose.ui.unit.dp
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.launch
import kotlinx.coroutines.withContext
import okhttp3.Request
import org.terst.feedreader.data.AppDatabase
import org.terst.feedreader.data.FeedEntity
import org.terst.feedreader.data.FeedParser
import org.terst.feedreader.data.Net
import org.terst.feedreader.opml.Opml
import org.terst.feedreader.work.FeedFetchWorker

@OptIn(ExperimentalMaterial3Api::class)
@Composable
fun AddFeedScreen(onDone: () -> Unit) {
    val context = LocalContext.current
    val db = remember { AppDatabase.get(context) }
    val scope = rememberCoroutineScope()

    var url by remember { mutableStateOf("") }
    var status by remember { mutableStateOf<String?>(null) }
    var isBusy by remember { mutableStateOf(false) }

    val importLauncher = rememberLauncherForActivityResult(ActivityResultContracts.GetContent()) { uri ->
        if (uri == null) return@rememberLauncherForActivityResult
        isBusy = true
        scope.launch {
            val imported = withContext(Dispatchers.IO) {
                context.contentResolver.openInputStream(uri)?.use { stream -> Opml.parse(stream) } ?: emptyList()
            }
            // A feed cross-listed under multiple OPML category folders (common when
            // exported from a reader with folders/labels) appears once per folder here --
            // dedupe by feed URL before reporting a count, or "108 feeds" would be reported
            // as some larger number even though upsert already collapses them to one row each.
            val uniqueFeeds = imported.distinctBy { it.xmlUrl }
            for (feed in uniqueFeeds) {
                // upsert() REPLACEs the whole row -- for a feed that's already subscribed,
                // building a bare FeedEntity here would silently wipe readerModeDisabled
                // (and etag/lastModified/lastError) back to defaults on every re-import.
                // Preserve the existing row's other fields; only title/siteUrl come from OPML.
                val existing = db.feedDao().getById(feed.xmlUrl)
                val entity = existing?.copy(title = feed.title, siteUrl = feed.htmlUrl ?: existing.siteUrl)
                    ?: FeedEntity(id = feed.xmlUrl, title = feed.title, siteUrl = feed.htmlUrl)
                db.feedDao().upsert(entity)
            }
            FeedFetchWorker.fetchNow(context)
            status = "Imported ${uniqueFeeds.size} feed(s)"
            isBusy = false
        }
    }

    val exportLauncher = rememberLauncherForActivityResult(ActivityResultContracts.CreateDocument("text/x-opml")) { uri ->
        if (uri == null) return@rememberLauncherForActivityResult
        scope.launch {
            withContext(Dispatchers.IO) {
                val feeds = db.feedDao().getAll()
                context.contentResolver.openOutputStream(uri)?.use { out -> Opml.write(feeds, out) }
            }
            status = "Exported subscriptions"
        }
    }

    Scaffold(
        topBar = {
            TopAppBar(
                title = { Text("Add Feed") },
                navigationIcon = {
                    IconButton(onClick = onDone) {
                        Icon(Icons.Default.ArrowBack, contentDescription = "Back")
                    }
                }
            )
        }
    ) { padding ->
        LazyColumn(modifier = Modifier.fillMaxWidth().padding(padding)) {
            item {
                Column(modifier = Modifier.padding(16.dp)) {
                    OutlinedTextField(
                        value = url,
                        onValueChange = { url = it },
                        label = { Text("Feed URL") },
                        modifier = Modifier.fillMaxWidth()
                    )
                    Spacer(modifier = Modifier.height(4.dp))
                    Button(
                        enabled = url.isNotBlank() && !isBusy,
                        onClick = {
                            isBusy = true
                            val feedUrl = url.trim()
                            scope.launch {
                                status = addFeedByUrl(context, db, feedUrl)
                                if (status?.startsWith("Added") == true) url = ""
                                isBusy = false
                            }
                        },
                        modifier = Modifier.fillMaxWidth()
                    ) { Text("Add") }

                    Spacer(modifier = Modifier.height(8.dp))
                    OutlinedButton(onClick = { importLauncher.launch("*/*") }, modifier = Modifier.fillMaxWidth()) {
                        Text("Import OPML")
                    }
                    Spacer(modifier = Modifier.height(4.dp))
                    OutlinedButton(onClick = { exportLauncher.launch("subscriptions.opml") }, modifier = Modifier.fillMaxWidth()) {
                        Text("Export OPML")
                    }

                    status?.let {
                        Spacer(modifier = Modifier.height(8.dp))
                        Text(it)
                    }
                }
            }
        }
    }
}

private suspend fun addFeedByUrl(context: android.content.Context, db: AppDatabase, feedUrl: String): String =
    withContext(Dispatchers.IO) {
        try {
            val response = Net.client.newCall(Request.Builder().url(feedUrl).build()).execute()
            response.use {
                if (!it.isSuccessful) return@withContext "Couldn't fetch feed: HTTP ${it.code}"
                val body = it.body ?: return@withContext "Empty response"
                val parsed = FeedParser.parse(body.byteStream())
                // Same REPLACE-wipes-other-fields concern as the OPML import path.
                val existing = db.feedDao().getById(feedUrl)
                val entity = existing?.copy(
                    title = parsed.title.ifBlank { feedUrl },
                    siteUrl = parsed.siteUrl ?: existing.siteUrl
                ) ?: FeedEntity(id = feedUrl, title = parsed.title.ifBlank { feedUrl }, siteUrl = parsed.siteUrl)
                db.feedDao().upsert(entity)
            }
            FeedFetchWorker.fetchNow(context)
            "Added"
        } catch (e: Exception) {
            "Couldn't add feed: ${e.message}"
        }
    }