namespace MeterVault.Infrastructure.Dashboard;

/// <summary>KPI card figures for a period plus the delta versus the previous comparable period.</summary>
public sealed record CostKpi(double Current, double Previous)
{
    public double Delta => Current - Previous;

    public double DeltaPercent => Previous == 0 ? 0 : (Current - Previous) / Math.Abs(Previous) * 100.0;

    /// <summary>+1 up, -1 down, 0 flat.</summary>
    public int Direction => Math.Sign(Math.Round(Delta, 2));
}

/// <summary>The overview KPIs: month and year cost, each with its previous-period comparison.</summary>
public sealed record DashboardSummary(DateOnly AsOf, CostKpi Month, CostKpi Year, double LatestMonthCost);

/// <summary>One slice of the cost breakdown / "what costs most" view.</summary>
public sealed record CategorySlice(string Name, string? ColorHex, double Cost);

/// <summary>The first thing missing before the dashboard can show a cost, in the order they are set up.</summary>
public enum CostSetupGap
{
    None,
    NoMeters,
    NoCategories,
    NoMembers,
    NoTariffs,
}

/// <summary>
/// What exists of the chain a cost figure needs: a meter, a category that counts it, and a price.
/// </summary>
/// <remarks>
/// Manual costs stand in for the meter side only on an instance without meters. Once there are meters,
/// their chain is diagnosed on its own: the diagnosis only runs when this year shows no cost, so any
/// manual cost there is from another year and explains nothing about the meters.
/// </remarks>
public sealed record CostSetup(bool HasMeters, bool HasCategories, bool HasMembers, bool HasTariffs, bool HasManualCosts)
{
    public CostSetupGap FirstGap =>
        !HasMeters && !HasManualCosts ? CostSetupGap.NoMeters
        : !HasCategories ? CostSetupGap.NoCategories
        : !HasMeters ? CostSetupGap.None
        : !HasMembers ? CostSetupGap.NoMembers
        : !HasTariffs ? CostSetupGap.NoTariffs
        : CostSetupGap.None;
}

/// <summary>A point on a monthly cost/consumption trend.</summary>
public sealed record TrendPoint(DateOnly Period, double Cost);

/// <summary>A row of the "what cost more / less" difference view.</summary>
public sealed record DifferenceRow(string Name, double Current, double Previous)
{
    public double Delta => Current - Previous;

    public double DeltaPercent => Previous == 0 ? 0 : (Current - Previous) / Math.Abs(Previous) * 100.0;
}