package org.terst.feedreader.ui

import android.content.Intent
import android.net.Uri
import android.webkit.WebView
import androidx.compose.foundation.layout.Box
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.foundation.layout.padding
import androidx.compose.material.icons.Icons
import androidx.compose.material.icons.filled.ArrowBack
import androidx.compose.material.icons.filled.Bookmark
import androidx.compose.material.icons.filled.BookmarkBorder
import androidx.compose.material.icons.filled.OpenInBrowser
import androidx.compose.material3.CircularProgressIndicator
import androidx.compose.material3.ExperimentalMaterial3Api
import androidx.compose.material3.Icon
import androidx.compose.material3.IconButton
import androidx.compose.material3.Scaffold
import androidx.compose.material3.SnackbarHost
import androidx.compose.material3.SnackbarHostState
import androidx.compose.material3.Text
import androidx.compose.material3.TopAppBar
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.platform.LocalContext
import androidx.compose.ui.viewinterop.AndroidView
import kotlinx.coroutines.launch
import org.terst.feedreader.data.AppDatabase
import org.terst.feedreader.data.ArticleEntity
import org.terst.feedreader.data.Net
import org.terst.feedreader.data.Settings
import org.terst.feedreader.readability.ReaderExtractor
import org.terst.feedreader.stash.StashClient
import org.terst.feedreader.stash.StashSaveResult

// Below this length (of the plain feed-provided HTML), assume it's a teaser/summary,
// not the real article body, and fall back to on-device Readability extraction.
private const val THIN_CONTENT_THRESHOLD = 500

@OptIn(ExperimentalMaterial3Api::class)
@Composable
fun ReaderScreen(articleId: String, onBack: () -> Unit) {
    val context = LocalContext.current
    val db = remember { AppDatabase.get(context) }
    val scope = rememberCoroutineScope()
    val snackbarHostState = remember { SnackbarHostState() }

    var article by remember { mutableStateOf<ArticleEntity?>(null) }
    var displayContent by remember { mutableStateOf<String?>(null) }
    var isExtracting by remember { mutableStateOf(false) }
    var isSaving by remember { mutableStateOf(false) }

    LaunchedEffect(articleId) {
        val loaded = db.articleDao().getById(articleId) ?: return@LaunchedEffect
        article = loaded
        db.articleDao().setRead(articleId, true)

        val feedContent = loaded.feedContentHtml
        val plainLength = feedContent?.replace(Regex("<[^>]*>"), "")?.trim()?.length ?: 0

        displayContent = when {
            loaded.extractedContent != null -> loaded.extractedContent
            plainLength >= THIN_CONTENT_THRESHOLD -> feedContent
            else -> {
                isExtracting = true
                val extracted = ReaderExtractor.extract(context, loaded.link)
                isExtracting = false
                val content = extracted?.content
                if (content != null) {
                    db.articleDao().setExtractedContent(articleId, content)
                    content
                } else {
                    feedContent ?: "<p>Couldn't load article content. Try opening in browser.</p>"
                }
            }
        }
    }

    Scaffold(
        topBar = {
            TopAppBar(
                title = { Text(article?.title.orEmpty(), maxLines = 1) },
                navigationIcon = {
                    IconButton(onClick = onBack) {
                        Icon(Icons.Default.ArrowBack, contentDescription = "Back")
                    }
                },
                actions = {
                    val currentArticle = article
                    IconButton(onClick = {
                        val a = currentArticle ?: return@IconButton
                        val browserIntent = Intent(Intent.ACTION_VIEW, Uri.parse(a.link))
                        context.startActivity(browserIntent)
                    }) {
                        Icon(Icons.Default.OpenInBrowser, contentDescription = "Open in browser")
                    }
                    IconButton(
                        enabled = !isSaving,
                        onClick = {
                            val a = currentArticle ?: return@IconButton
                            isSaving = true
                            scope.launch {
                                val settings = Settings(context)
                                val client = StashClient(Net.client, settings.stashBaseUrlNow(), settings.stashApiKeyNow())
                                when (val result = client.saveArticle(a.link, a.title)) {
                                    is StashSaveResult.Saved -> {
                                        db.articleDao().setSaved(a.id, true)
                                        db.articleDao().setStashArtifactId(a.id, result.artifact.id)
                                        snackbarHostState.showSnackbar("Saved to Stash")
                                    }
                                    is StashSaveResult.AlreadySaved -> {
                                        db.articleDao().setSaved(a.id, true)
                                        db.articleDao().setStashArtifactId(a.id, result.existingId)
                                        snackbarHostState.showSnackbar("Already in Stash")
                                    }
                                    is StashSaveResult.Failed ->
                                        snackbarHostState.showSnackbar("Save failed: ${result.message}")
                                }
                                isSaving = false
                            }
                        }
                    ) {
                        Icon(
                            if (currentArticle?.isSaved == true) Icons.Default.Bookmark else Icons.Default.BookmarkBorder,
                            contentDescription = "Save to Stash"
                        )
                    }
                }
            )
        },
        snackbarHost = { SnackbarHost(snackbarHostState) }
    ) { padding ->
        Box(modifier = Modifier.fillMaxSize().padding(padding)) {
            val content = displayContent
            val baseUrl = article?.link
            if (content != null) {
                AndroidView(
                    modifier = Modifier.fillMaxSize(),
                    factory = { ctx ->
                        WebView(ctx).apply {
                            settings.javaScriptEnabled = false
                            loadDataWithBaseURL(baseUrl, wrapHtml(content), "text/html", "UTF-8", null)
                        }
                    },
                    update = { webView -> webView.loadDataWithBaseURL(baseUrl, wrapHtml(content), "text/html", "UTF-8", null) }
                )
            } else if (isExtracting) {
                CircularProgressIndicator(modifier = Modifier.align(Alignment.Center))
            }
        }
    }
}

private fun wrapHtml(bodyContent: String): String = """
    <html><head><meta name="viewport" content="width=device-width, initial-scale=1">
    <style>body { font-family: sans-serif; font-size: 18px; line-height: 1.5; padding: 16px; }
    img { max-width: 100%; height: auto; }</style></head>
    <body>$bodyContent</body></html>
""".trimIndent()