package io.oxygenhub.android.ui.dashboard

import androidx.lifecycle.ViewModel

import io.oxygenhub.android.api.Avatar

import io.oxygenhub.android.api.HubApi

import io.oxygenhub.android.api.Repository

import io.oxygenhub.android.api.User

import io.oxygenhub.android.api.UserProposals

import io.oxygenhub.android.auth.Session

import io.oxygenhub.android.ui.common.Avatars

import io.oxygenhub.android.ui.common.Load

import io.oxygenhub.android.ui.common.load

import kotlinx.coroutines.CancellationException

import kotlinx.coroutines.Job

import kotlinx.coroutines.async

import kotlinx.coroutines.coroutineScope

import kotlinx.coroutines.flow.MutableStateFlow

import kotlinx.coroutines.flow.StateFlow

import kotlinx.coroutines.flow.asStateFlow

import java.util.Calendar

data class Dashboard(

    val greeting: String,

    /** The account, or null when the token may not read it (no `user:read`). */

    val user: User?,

    /** The account's avatar (#13), or null while the hub has none this app can draw. */

    val avatar: Avatar? = null,

    /** Whose avatar: the signed-in account's name. */

    val username: String = "",

    /** Proposals to review and the account's own (#18); null when the hub cannot say. */

    val proposals: UserProposals? = null,

    /** The newest-updated repositories: the user's own, or everyone's when they own none. */

    val recent: List<Repository>,

    val recentAreYours: Boolean,

    val repositoryCount: Int,

)

class DashboardViewModel(

    private val api: HubApi,

    private val session: Session,

    private val hourOfDay: () -> Int = { Calendar.getInstance().get(Calendar.HOUR_OF_DAY) },

) : ViewModel() {

    private val _state = MutableStateFlow<Load<Dashboard>>(Load.Loading)

    val state: StateFlow<Load<Dashboard>> = _state.asStateFlow()

    private var job: Job? = null

    init {

        refresh()

    }

    fun refresh() {

        job = load(_state, job) { fetch() }

    }

    private suspend fun fetch(): Dashboard = coroutineScope {

        // The account is a nicety (a display name); the repositories are the page.

        val user = async {

            try {

                api.user()

            } catch (e: CancellationException) {

                throw e

            } catch (_: Exception) {

                null

            }

        }

        // As are the proposals: a hub without the call shows none.

        val proposals = async {

            try {

                api.userProposals()

            } catch (e: CancellationException) {

                throw e

            } catch (_: Exception) {

                null

            }

        }

        // As is the avatar: its failure leaves the last one, or the initial.

        val avatar = async { Avatars.load(api, session.username) }

        val repos = api.repositories()

        val me = user.await()

        val username = me?.username ?: session.username

        val mine = repos.filter { it.owner == username }

        val pool = mine.ifEmpty { repos }

        Dashboard(

            greeting = greeting(hourOfDay(), me?.shownName ?: session.username),

            user = me,

            avatar = avatar.await(),

            username = username,

            proposals = proposals.await(),

            recent = pool.sortedByDescending { it.updatedMs }.take(RECENT),

            recentAreYours = mine.isNotEmpty(),

            repositoryCount = mine.size,

        )

    }

    companion object {

        const val RECENT = 5

        fun greeting(hour: Int, name: String): String {

            val part = when (hour) {

                in 5..11 -> "Good morning"

                in 12..17 -> "Good afternoon"

                else -> "Good evening"

            }

            return "$part, $name"

        }

    }

}