/* 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.containers

import android.content.Context
import kotlinx.coroutines.CoroutineScope
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.flow.Flow
import kotlinx.coroutines.flow.collect
import kotlinx.coroutines.launch
import mozilla.components.browser.state.action.BrowserAction
import mozilla.components.browser.state.action.ContainerAction
import mozilla.components.browser.state.state.BrowserState
import mozilla.components.browser.state.state.Container
import mozilla.components.browser.state.state.ContainerState
import mozilla.components.lib.state.Middleware
import mozilla.components.lib.state.MiddlewareContext
import mozilla.components.lib.state.Store
import java.util.UUID
import kotlin.coroutines.CoroutineContext

/**
 * [Middleware] implementation for handling [ContainerAction] and syncing the containers in
 * [BrowserState.containers] with the [ContainerStorage].
 */
class ContainerMiddleware(
    applicationContext: Context,
    coroutineContext: CoroutineContext = Dispatchers.IO,
    private val containerStorage: Storage = ContainerStorage(applicationContext)
) : Middleware<BrowserState, BrowserAction> {

    private var scope = CoroutineScope(coroutineContext)

    override fun invoke(
        context: MiddlewareContext<BrowserState, BrowserAction>,
        next: (BrowserAction) -> Unit,
        action: BrowserAction
    ) {
        when (action) {
            is ContainerAction.InitializeContainerState -> initializeContainers(context.store)
            is ContainerAction.AddContainerAction -> addContainer(action)
            is ContainerAction.RemoveContainerAction -> removeContainer(context.store, action)
        }

        next(action)
    }

    private fun initializeContainers(
        store: Store<BrowserState, BrowserAction>
    ) = scope.launch {
        containerStorage.getContainers().collect { containers ->
            store.dispatch(ContainerAction.AddContainersAction(containers))
        }
    }

    private fun addContainer(
        action: ContainerAction.AddContainerAction
    ) = scope.launch {
        containerStorage.addContainer(
            contextId = action.container.contextId,
            name = action.container.name,
            color = action.container.color,
            icon = action.container.icon
        )
    }

    private fun removeContainer(
        store: Store<BrowserState, BrowserAction>,
        action: ContainerAction.RemoveContainerAction
    ) = scope.launch {
        store.state.containers[action.contextId]?.let {
            containerStorage.removeContainer(it)
        }
    }

    /**
     * Interface for a storage to be passed to the middleware.
     */
    interface Storage {
        /**
         * Returns a [Flow] list of all the [Container] instances.
         */
        fun getContainers(): Flow<List<Container>>

        /**
         * Adds a new [Container].
         */
        suspend fun addContainer(
            contextId: String = UUID.randomUUID().toString(),
            name: String,
            color: ContainerState.Color,
            icon: ContainerState.Icon
        )

        /**
         * Removes the given [Container].
         */
        suspend fun removeContainer(container: Container)
    }
}
