/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

package mozilla.components.feature.downloads

import android.content.ActivityNotFoundException
import android.content.Context
import android.content.Intent
import android.content.pm.ActivityInfo
import android.content.pm.ResolveInfo
import android.widget.Toast
import androidx.annotation.ColorRes
import androidx.annotation.VisibleForTesting
import androidx.annotation.VisibleForTesting.PRIVATE
import androidx.core.net.toUri
import androidx.fragment.app.FragmentManager
import kotlinx.coroutines.CoroutineScope
import kotlinx.coroutines.cancel
import kotlinx.coroutines.flow.collect
import kotlinx.coroutines.flow.mapNotNull
import mozilla.components.browser.state.selector.findCustomTabOrSelectedTab
import mozilla.components.browser.state.selector.findTabOrCustomTabOrSelectedTab
import mozilla.components.browser.state.state.SessionState
import mozilla.components.browser.state.state.content.DownloadState
import mozilla.components.browser.state.store.BrowserStore
import mozilla.components.feature.downloads.DownloadDialogFragment.Companion.FRAGMENT_TAG
import mozilla.components.feature.downloads.manager.DownloadManager
import mozilla.components.feature.downloads.manager.noop
import mozilla.components.feature.downloads.manager.onDownloadStopped
import mozilla.components.feature.downloads.ui.DownloaderApp
import mozilla.components.feature.downloads.ui.DownloadAppChooserDialog
import mozilla.components.lib.state.ext.flowScoped
import mozilla.components.support.base.feature.LifecycleAwareFeature
import mozilla.components.support.base.feature.OnNeedToRequestPermissions
import mozilla.components.support.base.feature.PermissionsFeature
import mozilla.components.support.ktx.android.content.appName
import mozilla.components.support.ktx.android.content.isPermissionGranted
import mozilla.components.support.ktx.kotlin.isSameOriginAs
import mozilla.components.support.ktx.kotlinx.coroutines.flow.ifChanged
import mozilla.components.support.utils.Browsers

/**
 * Feature implementation to provide download functionality for the selected
 * session. The feature will subscribe to the selected session and listen
 * for downloads.
 *
 * @property applicationContext a reference to the application context.
 * @property onNeedToRequestPermissions a callback invoked when permissions
 * need to be requested before a download can be performed. Once the request
 * is completed, [onPermissionsResult] needs to be invoked.
 * @property onDownloadStopped a callback invoked when a download is paused or completed.
 * @property downloadManager a reference to the [DownloadManager] which is
 * responsible for performing the downloads.
 * @property store a reference to the application's [BrowserStore].
 * @property useCases [DownloadsUseCases] instance for consuming processed downloads.
 * @property fragmentManager a reference to a [FragmentManager]. If a fragment
 * manager is provided, a dialog will be shown before every download.
 * @property promptsStyling styling properties for the dialog.
 * @property shouldForwardToThirdParties Indicates if downloads should be forward to third party apps,
 * if there are multiple apps a chooser dialog will shown.
 */
@Suppress("TooManyFunctions", "LongParameterList", "LargeClass")
class DownloadsFeature(
    private val applicationContext: Context,
    private val store: BrowserStore,
    @VisibleForTesting(otherwise = PRIVATE)
    internal val useCases: DownloadsUseCases,
    override var onNeedToRequestPermissions: OnNeedToRequestPermissions = { },
    onDownloadStopped: onDownloadStopped = noop,
    private val downloadManager: DownloadManager,
    private val tabId: String? = null,
    private val fragmentManager: FragmentManager? = null,
    private val promptsStyling: PromptsStyling? = null,
    private val shouldForwardToThirdParties: () -> Boolean = { false }
) : LifecycleAwareFeature, PermissionsFeature {

    var onDownloadStopped: onDownloadStopped
        get() = downloadManager.onDownloadStopped
        set(value) { downloadManager.onDownloadStopped = value }

    init {
        this.onDownloadStopped = onDownloadStopped
    }

    private var scope: CoroutineScope? = null

    @VisibleForTesting
    internal var dismissPromptScope: CoroutineScope? = null
    @VisibleForTesting
    internal var previousTab: SessionState? = null

    /**
     * Starts observing downloads on the selected session and sends them to the [DownloadManager]
     * to be processed.
     */
    @Suppress("Deprecation")
    override fun start() {
        // Dismiss the previous prompts when the user navigates to another site.
        // This prevents prompts from the previous page from covering content.
        dismissPromptScope = store.flowScoped { flow ->
            flow.mapNotNull { state -> state.findTabOrCustomTabOrSelectedTab(tabId) }
                    .ifChanged { it.content.url }
                    .collect {
                        val currentHost = previousTab?.content?.url
                        val newHost = it.content.url

                        // The user is navigating to another site
                        if (currentHost?.isSameOriginAs(newHost) == false) {
                            previousTab?.let { tab ->
                                // We have an old download request.
                                tab.content.download?.let { download ->
                                    dismissAllDownloadDialogs()
                                    useCases.consumeDownload(tab.id, download.id)
                                    previousTab = null
                                }
                            }
                        }
                    }
        }

        scope = store.flowScoped { flow ->
            flow.mapNotNull { state -> state.findTabOrCustomTabOrSelectedTab(tabId) }
                .ifChanged { it.content.download }
                .collect { state ->
                    state.content.download?.let { downloadState ->
                        previousTab = state
                        processDownload(state, downloadState)
                    }
                }
        }
    }

    /**
     * Calls the tryAgain function of the corresponding [DownloadManager]
     */
    @Suppress("Unused")
    fun tryAgain(id: String) {
        downloadManager.tryAgain(id)
    }

    /**
     * Stops observing downloads on the selected session.
     */
    override fun stop() {
        scope?.cancel()
        dismissPromptScope?.cancel()
        downloadManager.unregisterListeners()
    }

    /**
     * Notifies the [DownloadManager] that a new download must be processed.
     */
    @VisibleForTesting
    internal fun processDownload(tab: SessionState, download: DownloadState): Boolean {
        return if (applicationContext.isPermissionGranted(downloadManager.permissions.asIterable())) {

            if (shouldForwardToThirdParties()) {
                val apps = getDownloaderApps(applicationContext, download)

                // We only show the dialog If we have multiple apps that can handle the download.
                if (apps.size > 1) {
                    showAppDownloaderDialog(tab, download, apps)
                    return false
                }
            }

            if (fragmentManager != null && !download.skipConfirmation) {
                showDownloadDialog(tab, download)
                false
            } else {
                useCases.consumeDownload(tab.id, download.id)
                startDownload(download)
            }
        } else {
            onNeedToRequestPermissions(downloadManager.permissions)
            false
        }
    }

    @VisibleForTesting
    internal fun startDownload(download: DownloadState): Boolean {
        val id = downloadManager.download(download)
        return if (id != null) {
            true
        } else {
            showDownloadNotSupportedError()
            false
        }
    }

    /**
     * Notifies the feature that the permissions request was completed. It will then
     * either trigger or clear the pending download.
     */
    override fun onPermissionsResult(permissions: Array<String>, grantResults: IntArray) {
        if (permissions.isEmpty()) {
            // If we are requesting permissions while a permission prompt is already being displayed
            // then Android seems to call `onPermissionsResult` immediately with an empty permissions
            // list. In this case just ignore it.
            return
        }

        withActiveDownload { (tab, download) ->
            if (applicationContext.isPermissionGranted(downloadManager.permissions.asIterable())) {
                processDownload(tab, download)
            } else {
                useCases.consumeDownload(tab.id, download.id)
            }
        }
    }

    @VisibleForTesting(otherwise = PRIVATE)
    internal fun showDownloadNotSupportedError() {
        Toast.makeText(
            applicationContext,
            applicationContext.getString(
                R.string.mozac_feature_downloads_file_not_supported2,
                applicationContext.appName),
            Toast.LENGTH_LONG
        ).show()
    }

    @VisibleForTesting(otherwise = PRIVATE)
    internal fun showDownloadDialog(
        tab: SessionState,
        download: DownloadState,
        dialog: DownloadDialogFragment = getDownloadDialog()
    ) {
        dialog.setDownload(download)

        dialog.onStartDownload = {
            startDownload(download)
            useCases.consumeDownload.invoke(tab.id, download.id)
        }

        dialog.onCancelDownload = {
            useCases.consumeDownload.invoke(tab.id, download.id)
        }

        if (!isAlreadyADownloadDialog() && fragmentManager != null && !fragmentManager.isDestroyed) {
            dialog.showNow(fragmentManager, FRAGMENT_TAG)
        }
    }

    private fun getDownloadDialog(): DownloadDialogFragment {
        return findPreviousDownloadDialogFragment() ?: SimpleDownloadDialogFragment.newInstance(
                promptsStyling = promptsStyling
        )
    }

    @VisibleForTesting
    internal fun showAppDownloaderDialog(
        tab: SessionState,
        download: DownloadState,
        apps: List<DownloaderApp>,
        appChooserDialog: DownloadAppChooserDialog = getAppDownloaderDialog()
    ) {
        appChooserDialog.setApps(apps)
        appChooserDialog.onAppSelected = { app ->
            if (app.packageName == applicationContext.packageName) {
                startDownload(download)
            } else {
                try {
                    applicationContext.startActivity(app.toIntent())
                } catch (error: ActivityNotFoundException) {
                    val errorMessage = applicationContext.getString(
                        R.string.mozac_feature_downloads_unable_to_open_third_party_app,
                        app.name
                    )
                    Toast.makeText(applicationContext, errorMessage, Toast.LENGTH_SHORT).show()
                }
            }
            useCases.consumeDownload(tab.id, download.id)
        }

        appChooserDialog.onDismiss = {
            useCases.consumeDownload.invoke(tab.id, download.id)
        }

        if (!isAlreadyAppDownloaderDialog() && fragmentManager != null && !fragmentManager.isDestroyed) {
            appChooserDialog.showNow(fragmentManager, DownloadAppChooserDialog.FRAGMENT_TAG)
        }
    }

    private fun getAppDownloaderDialog() = findPreviousAppDownloaderDialogFragment()
            ?: DownloadAppChooserDialog.newInstance(
                    promptsStyling?.gravity,
                    promptsStyling?.shouldWidthMatchParent
            )

    @VisibleForTesting
    internal fun isAlreadyAppDownloaderDialog(): Boolean {
        return findPreviousAppDownloaderDialogFragment() != null
    }

    private fun findPreviousAppDownloaderDialogFragment(): DownloadAppChooserDialog? {
        return fragmentManager?.findFragmentByTag(DownloadAppChooserDialog.FRAGMENT_TAG) as? DownloadAppChooserDialog
    }

    @VisibleForTesting(otherwise = PRIVATE)
    internal fun isAlreadyADownloadDialog(): Boolean {
        return findPreviousDownloadDialogFragment() != null
    }

    private fun findPreviousDownloadDialogFragment(): DownloadDialogFragment? {
        return fragmentManager?.findFragmentByTag(FRAGMENT_TAG) as? DownloadDialogFragment
    }

    private fun withActiveDownload(block: (Pair<SessionState, DownloadState>) -> Unit) {
        val state = store.state.findCustomTabOrSelectedTab(tabId) ?: return
        val download = state.content.download ?: return
        block(Pair(state, download))
    }

    /**
     * Find all apps that can perform a download, including this app.
     */
    @VisibleForTesting
    internal fun getDownloaderApps(context: Context, download: DownloadState): List<DownloaderApp> {
        val packageManager = context.packageManager

        val browsers = Browsers.findResolvers(context, packageManager, includeThisApp = true)
                .associateBy { it.activityInfo.identifier }

        val thisApp = browsers.values
                .firstOrNull { it.activityInfo.packageName == context.packageName }
                ?.toDownloaderApp(context, download)

        val apps = Browsers.findResolvers(
                context,
                packageManager,
                includeThisApp = false,
                url = download.url,
                contentType = download.contentType
        )
        // Remove browsers and returns only the apps that can perform a download plus this app.
        return apps.filter { !browsers.contains(it.activityInfo.identifier) }
                .map { it.toDownloaderApp(context, download) } + listOfNotNull(thisApp)
    }

    @VisibleForTesting
    internal fun dismissAllDownloadDialogs() {
        findPreviousDownloadDialogFragment()?.dismiss()
        findPreviousAppDownloaderDialogFragment()?.dismiss()
    }

    private val ActivityInfo.identifier: String get() = packageName + name

    private fun DownloaderApp.toIntent(): Intent {
        return Intent(Intent.ACTION_VIEW).apply {
            setDataAndTypeAndNormalize(url.toUri(), contentType)
            flags = Intent.FLAG_ACTIVITY_NEW_TASK
            setClassName(packageName, activityName)
            addCategory(Intent.CATEGORY_BROWSABLE)
        }
    }

    /**
     * Styling for the download dialog prompt
     */
    data class PromptsStyling(
        val gravity: Int,
        val shouldWidthMatchParent: Boolean = false,
        @ColorRes
        val positiveButtonBackgroundColor: Int? = null,
        @ColorRes
        val positiveButtonTextColor: Int? = null,
        val positiveButtonRadius: Float? = null
    )
}

@VisibleForTesting
internal fun ResolveInfo.toDownloaderApp(context: Context, download: DownloadState): DownloaderApp {
    return DownloaderApp(
        loadLabel(context.packageManager).toString(),
        this,
        activityInfo.packageName,
        activityInfo.name,
        download.url,
        download.contentType
    )
}
