package com.aiosman.riderpro.data

import androidx.paging.PagingSource
import androidx.paging.PagingState
import com.aiosman.riderpro.R
import com.aiosman.riderpro.model.MomentItem
import com.aiosman.riderpro.test.TestDatabase
import java.io.IOException
import kotlin.math.min

interface MomentService {
    suspend fun getMomentById(id: Int): MomentItem
    suspend fun likeMoment(id: Int)
    suspend fun dislikeMoment(id: Int)
    suspend fun getMoments(
        pageNumber: Int,
        author: Int? = null,
        timelineId: Int? = null
    ): ListContainer<MomentItem>

    suspend fun createMoment(
        content: String,
        authorId: Int,
        imageUriList: List<String>
    ): MomentItem
}


class MomentPagingSource(
    private val remoteDataSource: MomentRemoteDataSource,
    private val author: Int? = null,
    private val timelineId: Int? = null
) : PagingSource<Int, MomentItem>() {
    override suspend fun load(params: LoadParams<Int>): LoadResult<Int, MomentItem> {
        return try {
            val currentPage = params.key ?: 1
            val moments = remoteDataSource.getMoments(
                pageNumber = currentPage,
                author = author,
                timelineId = timelineId
            )

            LoadResult.Page(
                data = moments.list,
                prevKey = if (currentPage == 1) null else currentPage - 1,
                nextKey = if (moments.list.isEmpty()) null else moments.page + 1
            )
        } catch (exception: IOException) {
            return LoadResult.Error(exception)
        }
    }

    override fun getRefreshKey(state: PagingState<Int, MomentItem>): Int? {
        return state.anchorPosition
    }

}

class MomentRemoteDataSource(
    private val momentService: MomentService,
) {
    suspend fun getMoments(
        pageNumber: Int,
        author: Int?,
        timelineId: Int?
    ): ListContainer<MomentItem> {
        return momentService.getMoments(pageNumber, author, timelineId)
    }
}


class TestMomentServiceImpl() : MomentService {
    val testMomentBackend = TestMomentBackend()

    override suspend fun getMoments(
        pageNumber: Int,
        author: Int?,
        timelineId: Int?
    ): ListContainer<MomentItem> {
        return testMomentBackend.fetchMomentItems(pageNumber, author, timelineId)
    }

    override suspend fun getMomentById(id: Int): MomentItem {
        return testMomentBackend.getMomentById(id)
    }


    override suspend fun likeMoment(id: Int) {
        testMomentBackend.likeMoment(id)
    }

    override suspend fun dislikeMoment(id: Int) {
        testMomentBackend.dislikeMoment(id)
    }

    override suspend fun createMoment(
        content: String,
        authorId: Int,
        imageUriList: List<String>
    ): MomentItem {
        return testMomentBackend.createMoment(content, authorId, imageUriList)
    }

}

class TestMomentBackend(
    private val loadDelay: Long = 500,
) {
    val DataBatchSize = 5
    suspend fun fetchMomentItems(
        pageNumber: Int,
        author: Int? = null,
        timelineId: Int?
    ): ListContainer<MomentItem> {
        var rawList = TestDatabase.momentData
        rawList = rawList.sortedBy { it.id }.reversed()
        if (author != null) {
            rawList = rawList.filter { it.authorId == author }
        }
        if (timelineId != null) {
            val followIdList = TestDatabase.followList.filter {
                it.first == timelineId
            }.map { it.second }
            rawList = rawList.filter { it.authorId in followIdList || it.authorId == 1 }
        }
        val from = (pageNumber - 1) * DataBatchSize
        val to = (pageNumber) * DataBatchSize
        if (from >= rawList.size) {
            return ListContainer(
                total = rawList.size,
                page = pageNumber,
                pageSize = DataBatchSize,
                list = emptyList()
            )
        }
        val currentSublist = rawList.subList(from, min(to, rawList.size))
        currentSublist.forEach {
            val myLikeIdList =
                TestDatabase.likeMomentList.filter { it.second == 1 }.map { it.first }
            if (myLikeIdList.contains(it.id)) {
                it.liked = true
            }
        }

        // delay
        kotlinx.coroutines.delay(loadDelay)
        return ListContainer(
            total = rawList.size,
            page = pageNumber,
            pageSize = DataBatchSize,
            list = currentSublist
        )
    }

    suspend fun getMomentById(id: Int): MomentItem {
        var moment = TestDatabase.momentData.first {
            it.id == id
        }
        val isLike = TestDatabase.likeMomentList.any {
            it.first == id && it.second == 1
        }
        moment = moment.copy(liked = isLike)
        return moment
    }

    suspend fun likeMoment(id: Int) {
        val oldMoment = TestDatabase.momentData.first {
            it.id == id
        }
        val newMoment = oldMoment.copy(likeCount = oldMoment.likeCount + 1)
        TestDatabase.updateMomentById(id, newMoment)
        TestDatabase.likeMomentList += Pair(id, 1)
    }

    suspend fun dislikeMoment(id: Int) {
        val oldMoment = TestDatabase.momentData.first {
            it.id == id
        }
        val newMoment = oldMoment.copy(likeCount = oldMoment.likeCount - 1)
        TestDatabase.updateMomentById(id, newMoment)
        TestDatabase.likeMomentList = TestDatabase.likeMomentList.filter {
            it.first != id
        }
    }

    suspend fun createMoment(
        content: String,
        authorId: Int,
        imageUriList: List<String>
    ): MomentItem {
        TestDatabase.momentIdCounter += 1
        val person = TestDatabase.accountData.first {
            it.id == authorId
        }
        val newMoment = MomentItem(
            id = TestDatabase.momentIdCounter,
            avatar = person.avatar,
            nickname = person.nickName,
            location = person.country,
            time = "2023.02.02 11:23",
            followStatus = false,
            momentTextContent = content,
            momentPicture = R.drawable.default_moment_img,
            likeCount = 0,
            commentCount = 0,
            shareCount = 0,
            favoriteCount = 0,
            images = imageUriList,
            authorId = person.id
        )
        TestDatabase.momentData += newMoment
        return newMoment
    }

}