package io.oxygenhub.android.ui.proposals

import androidx.compose.foundation.lazy.LazyColumn

import androidx.compose.material.icons.Icons

import androidx.compose.material.icons.outlined.Description

import androidx.compose.runtime.Composable

import androidx.compose.runtime.getValue

import androidx.compose.runtime.mutableStateOf

import androidx.compose.runtime.saveable.rememberSaveable

import androidx.compose.runtime.setValue

import androidx.lifecycle.ViewModel

import androidx.lifecycle.compose.collectAsStateWithLifecycle

import io.oxygenhub.android.api.FileChange

import io.oxygenhub.android.api.HubApi

import io.oxygenhub.android.ui.code.fileDiffs

import io.oxygenhub.android.ui.code.openByDefault

import io.oxygenhub.android.ui.common.AppScreen

import io.oxygenhub.android.ui.common.EmptyState

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

import io.oxygenhub.android.ui.common.LoadContent

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

import io.oxygenhub.android.ui.theme.LocalStatusColors

import kotlinx.coroutines.Job

import kotlinx.coroutines.flow.MutableStateFlow

import kotlinx.coroutines.flow.StateFlow

import kotlinx.coroutines.flow.asStateFlow

/** The files a proposal changes, each with its diff (#4). */

class ProposalFilesViewModel(private val api: HubApi, val owner: String, val name: String, val number: Long) : ViewModel() {

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

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

    private var job: Job? = null

    init {

        refresh()

    }

    fun refresh() {

        job = load(_state, job) { api.proposalDiff(owner, name, number) }

    }

}

/** A proposal's files, as its page on the hub shows them: each folds open to its diff. */

@Composable

fun ProposalFilesScreen(vm: ProposalFilesViewModel, onBack: () -> Unit) {

    val state by vm.state.collectAsStateWithLifecycle()

    val status = LocalStatusColors.current

    AppScreen(title = "Files · #${vm.number}", subtitle = "${vm.owner}/${vm.name}", onBack = onBack) {

        LoadContent(state, onRefresh = vm::refresh) { files ->

            if (files.isEmpty()) {

                EmptyState(Icons.Outlined.Description, "No files changed", "This proposal's changes are already on its target, or change nothing.")

                return@LoadContent

            }

            var open by rememberSaveable(vm.number) { mutableStateOf(openByDefault(files).toList()) }

            LazyColumn {

                fileDiffs(

                    files,

                    open,

                    status.ok,

                    status.bad,

                    onToggle = { path -> open = if (path in open) open - path else open + path },

                    onOpen = { null },

                )

            }

        }

    }

}