namespace Server.Engines.Pathing.Cache;

/// <summary>
/// Per-cell, per-direction walkability baked by <see cref="StepProbe"/> and stored by
/// <see cref="StepCache"/>. Two rule sets travel together: WalkMask + WalkZ_* for a default
/// walker (cantWalk=false, canSwim=false), WetMask + SwimZ_* for a swim-only mob
/// (cantWalk=true, canSwim=true). Callers overlay whichever applies to the mobile.
/// </summary>
public readonly struct StepMask(
    byte walkMask,
    byte wetMask,
    sbyte walkZN,
    sbyte walkZNE,
    sbyte walkZE,
    sbyte walkZSE,
    sbyte walkZS,
    sbyte walkZSW,
    sbyte walkZW,
    sbyte walkZNW,
    sbyte swimZN,
    sbyte swimZNE,
    sbyte swimZE,
    sbyte swimZSE,
    sbyte swimZS,
    sbyte swimZSW,
    sbyte swimZW,
    sbyte swimZNW,
    CacheHitKind hitKind = CacheHitKind.Hit
)
{
    public readonly byte WalkMask = walkMask;
    public readonly byte WetMask = wetMask;
    public readonly sbyte WalkZ_N = walkZN;
    public readonly sbyte WalkZ_NE = walkZNE;
    public readonly sbyte WalkZ_E = walkZE;
    public readonly sbyte WalkZ_SE = walkZSE;
    public readonly sbyte WalkZ_S = walkZS;
    public readonly sbyte WalkZ_SW = walkZSW;
    public readonly sbyte WalkZ_W = walkZW;
    public readonly sbyte WalkZ_NW = walkZNW;
    public readonly sbyte SwimZ_N = swimZN;
    public readonly sbyte SwimZ_NE = swimZNE;
    public readonly sbyte SwimZ_E = swimZE;
    public readonly sbyte SwimZ_SE = swimZSE;
    public readonly sbyte SwimZ_S = swimZS;
    public readonly sbyte SwimZ_SW = swimZSW;
    public readonly sbyte SwimZ_W = swimZW;
    public readonly sbyte SwimZ_NW = swimZNW;
    public readonly CacheHitKind HitKind = hitKind;

    /// <summary>
    /// True when the cache produced a usable answer. False on any Fallthrough_*, where the
    /// payload is all zeroes and the caller must resolve this cell via the slow path.
    /// </summary>
    public bool IsHit => HitKind <= CacheHitKind.Miss_DirtyRebuild;

    public bool IsWalkable(Direction d) => (WalkMask & (1 << (int)d)) != 0;
    public bool IsSwimmable(Direction d) => (WetMask & (1 << (int)d)) != 0;

    public sbyte GetWalkZ(Direction d) => d switch
    {
        Direction.North => WalkZ_N,
        Direction.Right => WalkZ_NE,
        Direction.East  => WalkZ_E,
        Direction.Down  => WalkZ_SE,
        Direction.South => WalkZ_S,
        Direction.Left  => WalkZ_SW,
        Direction.West  => WalkZ_W,
        Direction.Up    => WalkZ_NW,
        _ => 0
    };

    public sbyte GetSwimZ(Direction d) => d switch
    {
        Direction.North => SwimZ_N,
        Direction.Right => SwimZ_NE,
        Direction.East  => SwimZ_E,
        Direction.Down  => SwimZ_SE,
        Direction.South => SwimZ_S,
        Direction.Left  => SwimZ_SW,
        Direction.West  => SwimZ_W,
        Direction.Up    => SwimZ_NW,
        _ => 0
    };
}