@page "/"
@using Butter.Dtos.Asset
@using Butter.Types
@using Microsoft.Extensions.Options
@using Microsoft.JSInterop
@using MilkStream.Client.Components.Layout
@using MilkStream.Client.Services
@implements IAsyncDisposable

@inject AssetService            assetService
@inject LoginService            loginService
@inject IJSRuntime              jsRuntime
@inject IOptions<ServiceOptions> serviceOptions

<PageTitle>Home</PageTitle>

@if (isLoading) {
    <LoadSpinner/>
} else if (flatList.Count == 0) {
    <div class="border-warning border-5 border-opacity-100 rounded-3 p-3 m-5 bg-warning-subtle text-center">
        <h2 class="text-warning">No media available</h2>
        @if (loginService.IsLoggedIn) {
            <p class="text-warning-emphasis">You are logged in, but there is no media available at the moment.</p>
        } else {
            <p class="text-warning-emphasis">Please <a href="/login" class="link-warning">log-in</a> to be able to browse any media.</p>
        }
    </div>
} else {
    <div class="masonry-grid">
        @{ var idx = 0; }
        @foreach (var page in allAssetPages) {
            @foreach (var asset in page) {
                var i = idx++;
                <div class="masonry-tile" @key="asset.Id"
                     style="aspect-ratio:@GetAspectRatio(asset)"
                     @onclick="() => OpenPreview(asset, i)">
                    @if (asset.HasThumbnail) {
                        <img src="@ThumbUrl(asset.Id)"
                             loading="lazy" alt=""
                             onerror="this.style.display='none';this.nextElementSibling.style.display='flex'" />
                        <div class="tile-fallback" style="display:none">
                            <i class="bi bi-image"></i>
                        </div>
                    } else {
                        <div class="tile-fallback">
                            <i class="bi bi-image"></i>
                        </div>
                    }
                </div>
            }
        }
    </div>

    @if (isLoadingMore) {
        <LoadSpinner/>
    }

    <div @ref="sentinelRef" class="masonry-sentinel"></div>
}

@if (selectedAsset != null) {
    <div class="preview-overlay" @onkeydown="OnPreviewKeyDown" tabindex="0" @onclick="ClosePreview">
        <div class="preview-content" @onclick:stopPropagation="true">
            <button class="preview-close" @onclick="ClosePreview">&times;</button>

            @if (selectedIndex > 0) {
                <button class="preview-nav preview-prev" @onclick="() => NavigatePreview(-1)" @onclick:stopPropagation="true">&#8249;</button>
            }
            @if (selectedIndex < flatList.Count - 1) {
                <button class="preview-nav preview-next" @onclick="() => NavigatePreview(1)" @onclick:stopPropagation="true">&#8250;</button>
            }

            @if (selectedAsset.HasPreview) {
                <img class="preview-img" src="@PreviewUrl(selectedAsset.Id)" alt=""
                     onerror="this.onerror=null;this.src='@ThumbUrl(selectedAsset.Id)'" />
            } else {
                <img class="preview-img" src="@ThumbUrl(selectedAsset.Id)" alt="" />
            }
        </div>
    </div>
}

@code {
    List<List<AssetPreviewDto>> allAssetPages = [];
    List<AssetPreviewDto> flatList = [];
    int currentPage = 1;
    bool hasMore = true;
    bool isLoading = true;
    bool isLoadingMore;
    AssetPreviewDto? selectedAsset;
    int selectedIndex = -1;
    ElementReference sentinelRef;
    DotNetObjectReference<Home>? dotNetRef;
    string token = string.Empty;
    string apiBase => serviceOptions.Value.BaseUrl.TrimEnd('/');

    string TokenParam => string.IsNullOrEmpty(token) ? "" : $"?token={token}";

    protected override async Task OnInitializedAsync() {
        loginService.LoggedUserChanged += (_, _) => StateHasChanged();
        loginService.AuthInfoChanged += (_, info) => {
            token = info?.Token ?? string.Empty;
            StateHasChanged();
        };
        token = loginService.AuthInfo?.Token ?? string.Empty;
        await LoadFirstPage();
    }

    protected override async Task OnAfterRenderAsync(bool firstRender) {
        if (flatList.Count > 0 && hasMore && dotNetRef == null) {
            dotNetRef = DotNetObjectReference.Create(this);
            await jsRuntime.InvokeVoidAsync(
                "masonryObserver.observe", sentinelRef, dotNetRef
            );
        }

        if (selectedAsset != null)
            await jsRuntime.InvokeVoidAsync("masonryObserver.lockBodyScroll");
        else
            await jsRuntime.InvokeVoidAsync("masonryObserver.unlockBodyScroll");
    }

    async Task LoadFirstPage() {
        isLoading = true;
        var items = await assetService.GetAssetsAsync(EAssetType.Image, true, 1, 30);
        if (items?.Count > 0) {
            allAssetPages.Add(items);
            RebuildFlatList();
            currentPage = 2;
        }
        hasMore = items?.Count == 30;
        isLoading = false;
    }

    [JSInvokable]
    public async Task LoadNextPage() {
        if (isLoadingMore || !hasMore) return;
        isLoadingMore = true;
        StateHasChanged();

        var items = await assetService.GetAssetsAsync(EAssetType.Image, true, currentPage, 30);
        if (items?.Count > 0) {
            allAssetPages.Add(items);
            RebuildFlatList();
            currentPage++;

            if (allAssetPages.Count > 10)
                allAssetPages.RemoveAt(0);
        }
        hasMore = items?.Count == 30;
        isLoadingMore = false;
        StateHasChanged();
    }

    void RebuildFlatList() => flatList = allAssetPages.SelectMany(p => p).ToList();

    void OpenPreview(AssetPreviewDto asset, int index) {
        selectedAsset = asset;
        selectedIndex = index;
    }

    void ClosePreview() {
        selectedAsset = null;
        selectedIndex = -1;
    }

    void NavigatePreview(int direction) {
        var newIndex = selectedIndex + direction;
        if (newIndex < 0 || newIndex >= flatList.Count) return;
        selectedAsset = flatList[newIndex];
        selectedIndex = newIndex;
    }

    void OnPreviewKeyDown(KeyboardEventArgs e) {
        switch (e.Key) {
            case "Escape":
                ClosePreview();
                break;
            case "ArrowLeft":
                NavigatePreview(-1);
                break;
            case "ArrowRight":
                NavigatePreview(1);
                break;
        }
    }

    static string GetAspectRatio(AssetPreviewDto asset) {
        if (asset.ResolutionWidth > 0 && asset.ResolutionHeight > 0)
            return $"{asset.ResolutionWidth} / {asset.ResolutionHeight}";
        return "4 / 3";
    }

    string ThumbUrl(Guid id) => $"{apiBase}/api/media/thumb/{id}{TokenParam}";
    string PreviewUrl(Guid id) => $"{apiBase}/api/media/preview/{id}{TokenParam}";

    public async ValueTask DisposeAsync() {
        if (dotNetRef != null) {
            await jsRuntime.InvokeVoidAsync("masonryObserver.dispose");
            dotNetRef.Dispose();
        }
    }
}