package org.terst.feedreader.ui

import android.app.AlarmManager
import android.content.Intent
import android.net.Uri
import android.os.Build
import android.os.Bundle
import android.provider.Settings
import android.util.Log
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 org.terst.feedreader.work.MorningFetchReceiver
import java.net.URLDecoder
import java.net.URLEncoder

private const val TAG = "MainActivity"
private const val KEY_REQUESTED_EXACT_ALARM = "requestedExactAlarmPermission"

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)
        requestedExactAlarmPermission = savedInstanceState?.getBoolean(KEY_REQUESTED_EXACT_ALARM) ?: false
        FeedFetchWorker.schedulePeriodic(applicationContext)
        maybeScheduleMorningFetch()
        // 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()
                }
            }
        }
    }

    // Re-checked on resume too, not just onCreate -- returning here from the "Alarms &
    // reminders" Settings screen (below) is an onResume, not a fresh onCreate, and the
    // alarm should get armed the moment permission is actually granted rather than
    // needing a full app relaunch.
    override fun onResume() {
        super.onResume()
        maybeScheduleMorningFetch()
    }

    // onCreate's own onStart/onResume fires once automatically as part of normal startup,
    // right after onCreate -- before the user has done anything -- so without this guard,
    // a not-yet-granted permission would launch the Settings screen twice back to back
    // (once from onCreate, immediately again from that auto-triggered onResume). Restored
    // from savedInstanceState in onCreate (see below), not left as a plain field that
    // silently resets to false on every config change -- a rotation while still ungranted
    // used to re-trigger the Settings screen every time the device rotated.
    private var requestedExactAlarmPermission = false

    override fun onSaveInstanceState(outState: Bundle) {
        super.onSaveInstanceState(outState)
        outState.putBoolean(KEY_REQUESTED_EXACT_ALARM, requestedExactAlarmPermission)
    }

    // Runs unconditionally on every onCreate/onResume -- must never let an exception
    // escape from here, or a device/OEM quirk around the exact-alarm APIs would crash
    // the app on every single launch. A wake-up alarm failing to schedule just isn't
    // worth that; worst case it's logged and tries again next launch.
    private fun maybeScheduleMorningFetch() {
        try {
            val alarmManager = getSystemService(AlarmManager::class.java) ?: return
            val canScheduleExact = Build.VERSION.SDK_INT < Build.VERSION_CODES.S || alarmManager.canScheduleExactAlarms()
            if (canScheduleExact) {
                MorningFetchReceiver.scheduleNext(applicationContext)
            } else if (!requestedExactAlarmPermission) {
                requestedExactAlarmPermission = true
                // Android 12+ only: exact alarms require a one-time user grant via Settings,
                // there's no in-app permission dialog for this one. Sends the user straight to
                // this app's page in the "Alarms & reminders" settings screen.
                startActivity(
                    Intent(Settings.ACTION_REQUEST_SCHEDULE_EXACT_ALARM, Uri.parse("package:$packageName"))
                )
            }
        } catch (e: Exception) {
            Log.e(TAG, "Failed to schedule or request permission for morning fetch", e)
        }
    }
}

@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() })
        }
    }
}