package org.terst.feedreader.ui

import android.os.Bundle
import android.webkit.CookieManager
import androidx.activity.ComponentActivity
import androidx.activity.compose.setContent
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.material3.MaterialTheme
import androidx.compose.material3.Surface
import androidx.compose.material3.darkColorScheme
import androidx.compose.runtime.Composable
import androidx.compose.ui.Modifier
import androidx.navigation.NavType
import androidx.navigation.compose.NavHost
import androidx.navigation.compose.composable
import androidx.navigation.compose.rememberNavController
import androidx.navigation.navArgument
import org.terst.feedreader.work.FeedFetchWorker
import java.net.URLDecoder
import java.net.URLEncoder

const val UNREAD_FEED_ID = "__unread__"
const val SAVED_FEED_ID = "__saved__"
const val OLDER_FEED_ID = "__older__"

// How far back the default Unread view reaches before an article falls into Older instead.
const val RECENT_WINDOW_MS = 72L * 60 * 60 * 1000

fun encodeNavArg(value: String): String = URLEncoder.encode(value, "UTF-8")
fun decodeNavArg(value: String): String = URLDecoder.decode(value, "UTF-8")

class MainActivity : ComponentActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        // The only implicit fetch trigger left: a fresh cold launch. No periodic
        // WorkManager job and no background alarm any more -- per user request, refreshing
        // only ever happens here or from an explicit tap on the refresh button.
        FeedFetchWorker.fetchNow(applicationContext)
        // Explicit, even though it defaults on -- BrowserScreen relies on cookies set
        // during a site login surviving into the reader's later extraction requests.
        CookieManager.getInstance().setAcceptCookie(true)

        setContent {
            // Dark by default -- per user request, not following system light/dark for now.
            MaterialTheme(colorScheme = darkColorScheme()) {
                Surface(modifier = Modifier.fillMaxSize()) {
                    FeedReaderApp()
                }
            }
        }
    }
}

@Composable
fun FeedReaderApp() {
    val navController = rememberNavController()
    // Unread is the landing screen (per user request) -- it has no "back" affordance of its
    // own since it's the root of the back stack; ArticleListScreen instead shows a way to
    // reach the feed list from there (a forward navigation, not a pop).
    NavHost(navController = navController, startDestination = "articles/${encodeNavArg(UNREAD_FEED_ID)}") {
        composable("feeds") {
            FeedListScreen(
                onOpenFeed = { feedId -> navController.navigate("articles/${encodeNavArg(feedId)}") },
                onOpenUnread = { navController.navigate("articles/${encodeNavArg(UNREAD_FEED_ID)}") },
                onOpenOlder = { navController.navigate("articles/${encodeNavArg(OLDER_FEED_ID)}") },
                onOpenSaved = { navController.navigate("articles/${encodeNavArg(SAVED_FEED_ID)}") },
                onAddFeed = { navController.navigate("addFeed") },
                onSettings = { navController.navigate("settings") }
            )
        }
        composable(
            "articles/{feedId}",
            arguments = listOf(navArgument("feedId") { type = NavType.StringType })
        ) { backStackEntry ->
            val feedId = decodeNavArg(backStackEntry.arguments?.getString("feedId") ?: UNREAD_FEED_ID)
            ArticleListScreen(
                feedId = feedId,
                onOpenArticle = { articleId ->
                    navController.navigate("reader/${encodeNavArg(feedId)}/${encodeNavArg(articleId)}")
                },
                onBack = { navController.popBackStack() },
                onOpenFeedList = { navController.navigate("feeds") }
            )
        }
        composable(
            "reader/{feedId}/{articleId}",
            arguments = listOf(
                navArgument("feedId") { type = NavType.StringType },
                navArgument("articleId") { type = NavType.StringType }
            )
        ) { backStackEntry ->
            val feedId = decodeNavArg(backStackEntry.arguments?.getString("feedId") ?: UNREAD_FEED_ID)
            val articleId = decodeNavArg(backStackEntry.arguments?.getString("articleId") ?: "")
            // feedId here is the list the article was opened from (Unread/Saved/a specific
            // feed) -- ReaderScreen uses it to look up the current article's neighbors.
            ReaderScreen(
                feedId = feedId,
                articleId = articleId,
                onBack = { navController.popBackStack() },
                onOpenLink = { url -> navController.navigate("linkReader/${encodeNavArg(url)}") },
                onOpenBrowser = { url -> navController.navigate("browser/${encodeNavArg(url)}") },
                // Replaces this screen's own back-stack entry rather than stacking a new
                // one per article (same popUpTo-replace pattern linkReader's own link-chain
                // navigation already uses below) -- so the stack is always exactly
                // [list, this one reader entry], and back always returns to the list in a
                // single press no matter how many articles were paged through via Next/Previous.
                onNavigateToArticle = { nextArticleId ->
                    navController.navigate("reader/${encodeNavArg(feedId)}/${encodeNavArg(nextArticleId)}") {
                        popUpTo("reader/{feedId}/{articleId}") { inclusive = true }
                    }
                }
            )
        }
        composable(
            "linkReader/{url}",
            arguments = listOf(navArgument("url") { type = NavType.StringType })
        ) { backStackEntry ->
            val url = decodeNavArg(backStackEntry.arguments?.getString("url") ?: "")
            // Recursive: a link tapped inside this screen pushes another linkReader route,
            // so following a chain of links stays inside the reader pipeline all the way down.
            LinkReaderScreen(
                url = url,
                onBack = { navController.popBackStack() },
                // Replaces the current linkReader entry rather than stacking another one on
                // top -- otherwise a chain of links-within-links (A -> link -> B -> link -> C)
                // made back step through the chain one hop at a time (C -> B -> A) instead of
                // returning straight to the source article A, which is what "back" actually
                // means here: leaving the link-reading detour, not undoing it one link at a time.
                onOpenLink = { nextUrl ->
                    navController.navigate("linkReader/${encodeNavArg(nextUrl)}") {
                        popUpTo("linkReader/{url}") { inclusive = true }
                    }
                },
                onOpenBrowser = { browserUrl -> navController.navigate("browser/${encodeNavArg(browserUrl)}") }
            )
        }
        composable(
            "browser/{url}",
            arguments = listOf(navArgument("url") { type = NavType.StringType })
        ) { backStackEntry ->
            val url = decodeNavArg(backStackEntry.arguments?.getString("url") ?: "")
            BrowserScreen(startUrl = url, onBack = { navController.popBackStack() })
        }
        composable("addFeed") {
            AddFeedScreen(onDone = { navController.popBackStack() })
        }
        composable("settings") {
            SettingsScreen(onBack = { navController.popBackStack() })
        }
    }
}