namespace IslaApocalypse.Tools
{
	/// <summary>
	/// Everything pass 1 produces. → <see cref="Topography"/>.
	///
	/// ⭐ THREE OF THESE FIELDS ARE THE PHASE-2 SEAM. The reference computed them in pass 1 and
	/// consumed them in pass 2; exposing them now is what keeps the deferred ports clean, and it
	/// costs nothing to carry.
	/// </summary>
	public sealed class Pass1Result
	{
		/// <summary>Map side in columns.</summary>
		public readonly int MapSize;

		/// <summary>The resolved seed this was generated with. Always positive, always recorded.</summary>
		public readonly int Seed;

		/// <summary>
		/// The raw pass-1 height field, <c>[x, y]</c>. Pre-curve, pre-erosion, pre-crater.
		/// The reference's <c>finalH</c> (~:619) written to <c>_heightMap</c> (~:666).
		/// </summary>
		public readonly float[,] Height;

		/// <summary>
		/// ⭐ PHASE-2 SEAM — the falloff value captured BEFORE the <c>Pow(·, 2.5f)</c> and BEFORE the
		/// Trench wall (reference ~:591, <c>preTrenchFalloff</c>).
		///
		/// It is the "how far past the island body are we" number, uncontaminated by the power's
		/// curvature and by the Trench's additive ramp. The DEFERRED offshore-islet layer reads it
		/// as its distance mask (<c>OffshoreZoneWeight</c>), which is the only reason it is captured
		/// mid-computation rather than recomputed.
		///
		/// ⚠ A port that "tidies" the falloff chain into one expression destroys this capture point,
		/// and the loss would not show up until Phase 2's offshore mask moved. It is exposed here so
		/// that cannot happen quietly.
		/// </summary>
		public readonly float[,] PreTrenchFalloff;

		/// <summary>
		/// ⭐ PHASE-2 SEAM — the wobbled latitude scalar, <c>[x, y]</c>.
		///
		/// ⚠ THIS IS NOT A CLIMATE TEMPERATURE MAP. See <see cref="Topography"/> for the full note.
		/// It is a stage-1-local latitude field that terrain GEOMETRY reads. Phase 2 needs it if the
		/// latitude sea-level model is ever switched on (<c>SeaLevelModel = "field"</c>); under the
		/// shipped flat model it has no consumer beyond the spine.
		/// </summary>
		public readonly float[,] LatitudeField;

		/// <summary>
		/// ⭐ PHASE-2 SEAM — the maximum height over the whole map (reference <c>_hMaxSeed</c>, ~:665).
		///
		/// The reference's v2+ redistribution curve is SEED-DEPENDENT: its spike maps
		/// <c>[t4, hMaxSeed]</c> onto the peak band, so pass 2 cannot start until pass 1 has scanned
		/// every pixel. That is precisely why the pass-1/pass-2 boundary is a hard one and not an
		/// interleave. Carried here so Phase 2 inherits it rather than rediscovering the dependency.
		/// </summary>
		public readonly float HMaxSeed;

		/// <summary>The minimum height. Not a reference field — carried for the renderer's ramp and the report.</summary>
		public readonly float HMinSeed;

		/// <summary>Wall-clock milliseconds the pass took.</summary>
		public readonly ulong ElapsedMs;

		public Pass1Result(int mapSize, int seed, float[,] height, float[,] preTrenchFalloff,
			float[,] latitudeField, float hMaxSeed, float hMinSeed, ulong elapsedMs)
		{
			MapSize = mapSize;
			Seed = seed;
			Height = height;
			PreTrenchFalloff = preTrenchFalloff;
			LatitudeField = latitudeField;
			HMaxSeed = hMaxSeed;
			HMinSeed = hMinSeed;
			ElapsedMs = elapsedMs;
		}

		/// <summary>Fraction of the map at or above the sea threshold. A cheap shape sanity number.</summary>
		public float LandFraction(float seaLevel)
		{
			long land = 0;
			for (int x = 0; x < MapSize; x++)
				for (int y = 0; y < MapSize; y++)
					if (Height[x, y] >= seaLevel) land++;
			return land / (float)((long)MapSize * MapSize);
		}
	}
}