@page "/reports"
@attribute [Authorize]
@inject TransactionService TransactionService
@inject AccountService AccountService
@inject CategoryService CategoryService
@inject SalaryService SalaryService
@inject AuthenticationStateProvider AuthStateProvider
@inject IJSRuntime JS
@implements IAsyncDisposable
@rendermode InteractiveServer

<PageTitle>Reports</PageTitle>

<h3 class="mb-2">Reports</h3>
<p class="text-muted mb-4">Visual breakdown of your spending and income by category for a specified time period.</p>

@if (loading)
{
    <p><em>Loading...</em></p>
}
else if (accounts.Count == 0)
{
    <div class="alert alert-info">
        <h5>No data yet</h5>
        <p>Add some <a href="/accounts">accounts</a> and <a href="/transactions">transactions</a> to see your spending reports.</p>
    </div>
}
else
{
    @* ── Date Range & Account Filters ── *@
    <div class="card mb-4">
        <div class="card-header d-flex flex-wrap align-items-center justify-content-between gap-2">
            <h5 class="mb-0">Filters</h5>
            <div class="d-flex flex-wrap align-items-center gap-2">
                <div class="btn-group btn-group-sm">
                    <button class="btn @(preset == "7d" ? "btn-primary" : "btn-outline-secondary")" @onclick="() => SetPreset(7)">7d</button>
                    <button class="btn @(preset == "30d" ? "btn-primary" : "btn-outline-secondary")" @onclick="() => SetPreset(30)">30d</button>
                    <button class="btn @(preset == "90d" ? "btn-primary" : "btn-outline-secondary")" @onclick="() => SetPreset(90)">90d</button>
                    <button class="btn @(preset == "1y" ? "btn-primary" : "btn-outline-secondary")" @onclick="() => SetPreset(365)">1y</button>
                </div>
                <input type="date" class="form-control form-control-sm" style="width:auto;"
                       title="Start date" @bind="dateFrom" @bind:after="OnDateChanged" />
                <span class="text-muted">to</span>
                <input type="date" class="form-control form-control-sm" style="width:auto;"
                       title="End date" @bind="dateTo" @bind:after="OnDateChanged" />
            </div>
        </div>
        <div class="card-body">
            <div class="d-flex flex-wrap gap-2">
                @foreach (var account in accounts)
                {
                    <button class="btn btn-sm @(selectedAccountIds.Contains(account.Id) ? "btn-primary" : "btn-outline-secondary")"
                            title="Toggle @account.Name" @onclick="() => ToggleAccount(account.Id)">
                        <span class="d-inline-block rounded-circle me-1" style="width:10px;height:10px;background-color:@account.Color;"></span>
                        @account.Name
                    </button>
                }
            </div>
        </div>
    </div>

    @* ── Expense by Category (Doughnut) ── *@
    <div class="row mb-4">
        <div class="col-lg-6 mb-4 mb-lg-0">
            <div class="card h-100">
                <div class="card-header"><h5 class="mb-0">Expenses by Category</h5></div>
                <div class="card-body">
                    @if (categoryBreakdown.Count == 0)
                    {
                        <p class="text-muted">No expenses in this period.</p>
                    }
                    else
                    {
                        <div style="position:relative;height:clamp(250px,35vw,400px);">
                            <canvas id="expensePieChart"></canvas>
                        </div>
                    }
                </div>
            </div>
        </div>

        @* ── Income by Category (Doughnut) ── *@
        <div class="col-lg-6">
            <div class="card h-100">
                <div class="card-header"><h5 class="mb-0">Income by Category</h5></div>
                <div class="card-body">
                    @if (incomeBreakdown.Count == 0)
                    {
                        <p class="text-muted">No income in this period.</p>
                    }
                    else
                    {
                        <div style="position:relative;height:clamp(250px,35vw,400px);">
                            <canvas id="incomePieChart"></canvas>
                        </div>
                    }
                </div>
            </div>
        </div>
    </div>

    @* ── Monthly Income vs Expenses (Bar) ── *@
    <div class="card mb-4">
        <div class="card-header"><h5 class="mb-0">Monthly Income vs Expenses</h5></div>
        <div class="card-body">
            @if (monthlyLabels.Count == 0)
            {
                <p class="text-muted">No transactions in this period.</p>
            }
            else
            {
                <div style="position:relative;height:clamp(250px,30vw,350px);">
                    <canvas id="monthlyBarChart"></canvas>
                </div>
            }
        </div>
    </div>

    @* ── Category Breakdown Table ── *@
    <div class="card mb-4">
        <div class="card-header"><h5 class="mb-0">Category Summary</h5></div>
        <div class="card-body">
            @if (categoryBreakdown.Count == 0 && incomeBreakdown.Count == 0)
            {
                <p class="text-muted">No transactions in this period.</p>
            }
            else
            {
                <div class="table-responsive">
                    <table class="table table-hover mb-0">
                        <thead>
                            <tr>
                                <th>Category</th>
                                <th class="text-end">Income</th>
                                <th class="text-end">Expenses</th>
                                <th class="text-end">Net</th>
                            </tr>
                        </thead>
                        <tbody>
                            @foreach (var row in categorySummary)
                            {
                                <tr>
                                    <td>@row.Icon @row.Name</td>
                                    <td class="text-end text-success">@currencySymbol@row.Income.ToString("N2")</td>
                                    <td class="text-end text-danger">@currencySymbol@row.Expense.ToString("N2")</td>
                                    <td class="text-end @(row.Net >= 0 ? "text-success" : "text-danger")">
                                        @currencySymbol@row.Net.ToString("N2")
                                    </td>
                                </tr>
                            }
                        </tbody>
                        <tfoot>
                            <tr class="fw-bold">
                                <td>Total</td>
                                <td class="text-end text-success">@currencySymbol@categorySummary.Sum(r => r.Income).ToString("N2")</td>
                                <td class="text-end text-danger">@currencySymbol@categorySummary.Sum(r => r.Expense).ToString("N2")</td>
                                @{ var totalNet = categorySummary.Sum(r => r.Net); }
                                <td class="text-end @(totalNet >= 0 ? "text-success" : "text-danger")">
                                    @currencySymbol@totalNet.ToString("N2")
                                </td>
                            </tr>
                        </tfoot>
                    </table>
                </div>
            }
        </div>
    </div>
}

@code {
    private bool loading = true;
    private string? userId;

    private DateTime dateFrom = DateTime.Today;
    private DateTime dateTo = DateTime.Today.AddDays(30);
    private string? preset = "30d";

    private List<Account> accounts = [];
    private HashSet<int> selectedAccountIds = [];
    private List<Category> categories = [];
    private string currencySymbol = "£";

    private List<CategoryAmount> categoryBreakdown = [];
    private List<CategoryAmount> incomeBreakdown = [];
    private List<CategorySummaryRow> categorySummary = [];

    private List<string> monthlyLabels = [];
    private List<decimal> monthlyIncome = [];
    private List<decimal> monthlyExpenses = [];

    private static readonly string[] chartColors =
    [
        "#4dc9f6", "#f67019", "#f53794", "#537bc4", "#acc236",
        "#166a8f", "#00a950", "#58595b", "#8549ba", "#e6194b",
        "#3cb44b", "#ffe119", "#4363d8", "#f58231", "#911eb4",
        "#42d4f4", "#f032e6", "#bfef45", "#fabed4", "#469990"
    ];

    protected override async Task OnInitializedAsync()
    {
        var authState = await AuthStateProvider.GetAuthenticationStateAsync();
        userId = authState.User.FindFirst(System.Security.Claims.ClaimTypes.NameIdentifier)?.Value;
        if (userId is null) return;

        accounts = await AccountService.GetAccountsAsync(userId);
        categories = await CategoryService.GetCategoriesAsync(userId);
        selectedAccountIds = accounts.Select(a => a.Id).ToHashSet();
        currencySymbol = accounts.FirstOrDefault()?.GetSymbol() ?? "£";

        await LoadReport();
        loading = false;
    }

    protected override async Task OnAfterRenderAsync(bool firstRender)
    {
        if (!firstRender || loading) return;
        await RenderCharts();
    }

    private async Task LoadReport()
    {
        if (userId is null) return;

        await SalaryService.MaterializeSalaryTransactionsAsync(userId, dateTo);
        var transactions = await TransactionService.GetTransactionsInRangeAsync(userId, dateFrom, dateTo);

        var filtered = transactions
            .Where(t => selectedAccountIds.Contains(t.AccountId))
            .ToList();

        categoryBreakdown = filtered
            .Where(t => t.Type == TransactionType.Expense)
            .GroupBy(t => t.CategoryId)
            .Select(g =>
            {
                var cat = categories.FirstOrDefault(c => c.Id == g.Key);
                return new CategoryAmount
                {
                    Name = cat?.Name ?? "Uncategorised",
                    Icon = cat?.Icon ?? "",
                    Total = g.Sum(t => t.Amount)
                };
            })
            .OrderByDescending(c => c.Total)
            .ToList();

        incomeBreakdown = filtered
            .Where(t => t.Type == TransactionType.Income)
            .GroupBy(t => t.CategoryId)
            .Select(g =>
            {
                var cat = categories.FirstOrDefault(c => c.Id == g.Key);
                return new CategoryAmount
                {
                    Name = cat?.Name ?? "Uncategorised",
                    Icon = cat?.Icon ?? "",
                    Total = g.Sum(t => t.Amount)
                };
            })
            .OrderByDescending(c => c.Total)
            .ToList();

        var allCategoryKeys = filtered
            .Select(t => t.CategoryId)
            .Distinct()
            .ToList();

        categorySummary = allCategoryKeys.Select(key =>
        {
            var cat = categories.FirstOrDefault(c => c.Id == key);
            var income = filtered.Where(t => t.CategoryId == key && t.Type == TransactionType.Income).Sum(t => t.Amount);
            var expense = filtered.Where(t => t.CategoryId == key && t.Type == TransactionType.Expense).Sum(t => t.Amount);
            return new CategorySummaryRow
            {
                Name = cat?.Name ?? "Uncategorised",
                Icon = cat?.Icon ?? "",
                Income = income,
                Expense = expense
            };
        })
        .OrderByDescending(r => r.Expense)
        .ToList();

        // Monthly data
        var monthly = filtered
            .GroupBy(t => new { t.Date.Year, t.Date.Month })
            .OrderBy(g => g.Key.Year).ThenBy(g => g.Key.Month)
            .ToList();

        monthlyLabels = monthly.Select(g => $"{g.Key.Year}-{g.Key.Month:D2}").ToList();
        monthlyIncome = monthly.Select(g => g.Where(t => t.Type == TransactionType.Income).Sum(t => t.Amount)).ToList();
        monthlyExpenses = monthly.Select(g => g.Where(t => t.Type == TransactionType.Expense).Sum(t => t.Amount)).ToList();
    }

    private async Task RenderCharts()
    {
        if (categoryBreakdown.Count > 0)
        {
            var labels = categoryBreakdown.Select(c => $"{c.Icon} {c.Name}".Trim()).ToArray();
            var data = categoryBreakdown.Select(c => c.Total).ToArray();
            var colors = Enumerable.Range(0, categoryBreakdown.Count).Select(i => chartColors[i % chartColors.Length]).ToArray();
            await JS.InvokeVoidAsync("chartInterop.createOrUpdatePieChart", "expensePieChart", labels, data, colors, currencySymbol, "doughnut");
        }

        if (incomeBreakdown.Count > 0)
        {
            var labels = incomeBreakdown.Select(c => $"{c.Icon} {c.Name}".Trim()).ToArray();
            var data = incomeBreakdown.Select(c => c.Total).ToArray();
            var colors = Enumerable.Range(0, incomeBreakdown.Count).Select(i => chartColors[i % chartColors.Length]).ToArray();
            await JS.InvokeVoidAsync("chartInterop.createOrUpdatePieChart", "incomePieChart", labels, data, colors, currencySymbol, "doughnut");
        }

        if (monthlyLabels.Count > 0)
        {
            await JS.InvokeVoidAsync("chartInterop.createOrUpdateBarChart", "monthlyBarChart", monthlyLabels.ToArray(), monthlyIncome.ToArray(), monthlyExpenses.ToArray(), currencySymbol);
        }
    }

    private async Task SetPreset(int days)
    {
        preset = days switch { 7 => "7d", 30 => "30d", 90 => "90d", 365 => "1y", _ => null };
        dateFrom = DateTime.Today;
        dateTo = DateTime.Today.AddDays(days);
        await Refresh();
    }

    private async Task OnDateChanged()
    {
        preset = null;
        await Refresh();
    }

    private async Task ToggleAccount(int accountId)
    {
        if (!selectedAccountIds.Remove(accountId))
            selectedAccountIds.Add(accountId);
        await Refresh();
    }

    private async Task Refresh()
    {
        await LoadReport();
        StateHasChanged();
        await Task.Yield();
        await RenderCharts();
    }

    public async ValueTask DisposeAsync()
    {
        try
        {
            await JS.InvokeVoidAsync("chartInterop.destroyChart", "expensePieChart");
            await JS.InvokeVoidAsync("chartInterop.destroyChart", "incomePieChart");
            await JS.InvokeVoidAsync("chartInterop.destroyChart", "monthlyBarChart");
        }
        catch (JSDisconnectedException) { }
    }

    private sealed class CategoryAmount
    {
        public string Name { get; set; } = string.Empty;
        public string Icon { get; set; } = string.Empty;
        public decimal Total { get; set; }
    }

    private sealed class CategorySummaryRow
    {
        public string Name { get; set; } = string.Empty;
        public string Icon { get; set; } = string.Empty;
        public decimal Income { get; set; }
        public decimal Expense { get; set; }
        public decimal Net => Income - Expense;
    }
}