dev-updater/app/androidApp/src/main/kotlin/com/example/devupdater/InstalledBuilds.kt

package com.example.devupdater

import android.content.BroadcastReceiver
import android.content.Context
import android.content.Intent
import android.content.IntentFilter
import android.content.pm.PackageManager
import androidx.core.content.ContextCompat
import java.io.File

// These are ad hoc local rebuilds with no CI bumping a version code, so it
// can't tell "already have this build" apart from "update available" --
// during active development the version code routinely stays put across
// many rebuilds. PackageManager tracks something better for this purpose
// regardless: `lastUpdateTime`, the epoch millis of when the currently
// installed copy was actually installed, maintained by the OS itself on
// every install (including a plain `adb install -r`, unlike a
// download-tracked-in-SharedPreferences approach, which would only learn
// about installs that went through this app's own download button).
// Compared directly against `/manifest`'s build-mtime epoch (see
// UpdateManifest.kt) -- both are wall-clock timestamps, so as long as the
// device and dev machine roughly agree on the time (true for an emulator
// or a phone on the same LAN), "installed after the currently-served build
// was produced" is a reliable proxy for "already have that build."
//
// Querying another app's PackageInfo needs package visibility on API 30+,
// normally granted per-package via this app's own <queries> in
// AndroidManifest.xml -- but that would mean a manifest edit (and a
// rebuild) every time a new app is added to the server's /manifest. This
// app instead holds QUERY_ALL_PACKAGES, which lets it query any installed
// package by name with no such declaration. That permission is a Play
// Store *policy* restriction, not something the OS itself enforces, so
// it's free to use here since this app is never distributed through Play (F-Droid
// takes the same approach for the same reason -- see AndroidManifest.xml).
fun installedLastUpdateTimeMillis(context: Context, packageName: String): Long? =
    try {
        context.packageManager.getPackageInfo(packageName, 0).lastUpdateTime
    } catch (_: PackageManager.NameNotFoundException) {
        null
    }

// Whether this package is on this device at all -- same query, asked as
// the question the caller actually has.
fun isInstalled(context: Context, packageName: String): Boolean =
    installedLastUpdateTimeMillis(context, packageName) != null

// The installed APK's own file size, for showing "old size -> new size" next
// to an available update -- same package-visibility caveat as above.
fun installedApkSizeBytes(context: Context, packageName: String): Long? =
    try {
        val sourceDir =
            context.packageManager.getPackageInfo(packageName, 0).applicationInfo?.sourceDir
        sourceDir?.let { File(it).length() }
    } catch (_: PackageManager.NameNotFoundException) {
        null
    }

// PACKAGE_ADDED/PACKAGE_REPLACED are protected system broadcasts -- only
// the OS can send them -- fired the moment PackageManager finishes
// registering an install, which happens before the installer's own "App
// installed" confirmation screen appears. That makes this a strictly
// earlier and more precise signal than polling or waiting for this app's
// activity to next resume (the latter only happens once the user backs out
// of that confirmation screen). Context-registered rather than
// manifest-declared since this app only cares about it while some screen
// is actually observing install state, not for the whole time it's
// installed -- see the paired unregisterReceiver call at the caller's
// DisposableEffect.
//
// RECEIVER_NOT_EXPORTED is correct, not just required (API 33+ rejects a
// context-registered receiver with neither flag): nothing but the system
// can send this broadcast regardless, so there's no legitimate case for
// another app to inject it here.
fun registerPackageChangeReceiver(
    context: Context,
    onPackageChanged: (packageName: String) -> Unit,
): BroadcastReceiver {
    val receiver =
        object : BroadcastReceiver() {
            override fun onReceive(context: Context, intent: Intent) {
                val packageName = intent.data?.schemeSpecificPart ?: return
                // An install over an existing copy sends REMOVED and then
                // ADDED, with EXTRA_REPLACING marking the pair. Reporting
                // the first would put "this package is gone" on screen for
                // the moment between them, which is a state nothing here
                // is in.
                if (intent.getBooleanExtra(Intent.EXTRA_REPLACING, false)) return
                onPackageChanged(packageName)
            }
        }
    val filter =
        IntentFilter().apply {
            addAction(Intent.ACTION_PACKAGE_ADDED)
            addAction(Intent.ACTION_PACKAGE_REPLACED)
            // Removals as well as arrivals, because one of them is a step
            // in something this app started: an app signed with a
            // different key has to be removed before the download can go
            // on, and this is what says the way is clear.
            addAction(Intent.ACTION_PACKAGE_REMOVED)
            addDataScheme("package")
        }
    ContextCompat.registerReceiver(context, receiver, filter, ContextCompat.RECEIVER_NOT_EXPORTED)
    return receiver
}