// Copyright 2016 Google Inc. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package s2

import (
	"math"
	"testing"

	"github.com/golang/geo/r1"
	"github.com/golang/geo/r2"
)

func TestPaddedCellMethods(t *testing.T) {
	// Test the PaddedCell methods that have approximate Cell equivalents.
	for i := 0; i < 1000; i++ {
		cid := randomCellID()
		padding := math.Pow(1e-15, randomFloat64())
		cell := CellFromCellID(cid)
		pCell := PaddedCellFromCellID(cid, padding)

		if cell.id != pCell.id {
			t.Errorf("%v.id = %v, want %v", pCell, pCell.id, cell.id)
		}
		if cell.id.Level() != pCell.Level() {
			t.Errorf("%v.Level() = %v, want %v", pCell, pCell.Level(), cell.id.Level())
		}

		if padding != pCell.Padding() {
			t.Errorf("%v.Padding() = %v, want %v", pCell, pCell.Padding(), padding)
		}

		if got, want := pCell.Bound(), cell.BoundUV().ExpandedByMargin(padding); got != want {
			t.Errorf("%v.BoundUV() = %v, want %v", pCell, got, want)
		}

		r := r2.RectFromPoints(cell.id.centerUV()).ExpandedByMargin(padding)
		if r != pCell.Middle() {
			t.Errorf("%v.Middle() = %v, want %v", pCell, pCell.Middle(), r)
		}

		if cell.id.Point() != pCell.Center() {
			t.Errorf("%v.Center() = %v, want %v", pCell, pCell.Center(), cell.id.Point())
		}
		if cid.IsLeaf() {
			continue
		}

		children, ok := cell.Children()
		if !ok {
			t.Errorf("%v.Children() failed but should not have", cell)
			continue
		}
		for pos := 0; pos < 4; pos++ {
			i, j := pCell.ChildIJ(pos)

			cellChild := children[pos]
			pCellChild := PaddedCellFromParentIJ(pCell, i, j)
			if cellChild.id != pCellChild.id {
				t.Errorf("%v.id = %v, want %v", pCellChild, pCellChild.id, cellChild.id)
			}
			if cellChild.id.Level() != pCellChild.Level() {
				t.Errorf("%v.Level() = %v, want %v", pCellChild, pCellChild.Level(), cellChild.id.Level())
			}

			if padding != pCellChild.Padding() {
				t.Errorf("%v.Padding() = %v, want %v", pCellChild, pCellChild.Padding(), padding)
			}

			if got, want := pCellChild.Bound(), cellChild.BoundUV().ExpandedByMargin(padding); got != want {
				t.Errorf("%v.BoundUV() = %v, want %v", pCellChild, got, want)
			}

			r := r2.RectFromPoints(cellChild.id.centerUV()).ExpandedByMargin(padding)
			if got := pCellChild.Middle(); !r.ApproxEqual(got) {
				t.Errorf("%v.Middle() = %v, want %v", pCellChild, got, r)
			}

			if cellChild.id.Point() != pCellChild.Center() {
				t.Errorf("%v.Center() = %v, want %v", pCellChild, pCellChild.Center(), cellChild.id.Point())
			}

		}
	}
}

func TestPaddedCellEntryExitVertices(t *testing.T) {
	for i := 0; i < 1000; i++ {
		id := randomCellID()
		unpadded := PaddedCellFromCellID(id, 0)
		padded := PaddedCellFromCellID(id, 0.5)

		// Check that entry/exit vertices do not depend on padding.
		if unpadded.EntryVertex() != padded.EntryVertex() {
			t.Errorf("entry vertex should not depend on padding; %v != %v", unpadded.EntryVertex(), padded.EntryVertex())
		}

		if unpadded.ExitVertex() != padded.ExitVertex() {
			t.Errorf("exit vertex should not depend on padding; %v != %v", unpadded.ExitVertex(), padded.ExitVertex())
		}

		// Check that the exit vertex of one cell is the same as the entry vertex
		// of the immediately following cell. This also tests wrapping from the
		// end to the start of the CellID curve with high probability.
		if got := PaddedCellFromCellID(id.NextWrap(), 0).EntryVertex(); unpadded.ExitVertex() != got {
			t.Errorf("PaddedCellFromCellID(%v.NextWrap(), 0).EntryVertex() = %v, want %v", id, got, unpadded.ExitVertex())
		}

		// Check that the entry vertex of a cell is the same as the entry vertex
		// of its first child, and similarly for the exit vertex.
		if id.IsLeaf() {
			continue
		}
		if got := PaddedCellFromCellID(id.Children()[0], 0).EntryVertex(); unpadded.EntryVertex() != got {
			t.Errorf("PaddedCellFromCellID(%v.Children()[0], 0).EntryVertex() = %v, want %v", id, got, unpadded.EntryVertex())
		}
		if got := PaddedCellFromCellID(id.Children()[3], 0).ExitVertex(); unpadded.ExitVertex() != got {
			t.Errorf("PaddedCellFromCellID(%v.Children()[3], 0).ExitVertex() = %v, want %v", id, got, unpadded.ExitVertex())
		}
	}
}

func TestPaddedCellShrinkToFit(t *testing.T) {
	for iter := 0; iter < 1000; iter++ {
		// Start with the desired result and work backwards.
		result := randomCellID()
		resultUV := result.boundUV()
		sizeUV := resultUV.Size()

		// Find the biggest rectangle that fits in "result" after padding.
		// (These calculations ignore numerical errors.)
		maxPadding := 0.5 * math.Min(sizeUV.X, sizeUV.Y)
		padding := maxPadding * randomFloat64()
		maxRect := resultUV.ExpandedByMargin(-padding)

		// Start with a random subset of the maximum rectangle.
		a := r2.Point{
			randomUniformFloat64(maxRect.X.Lo, maxRect.X.Hi),
			randomUniformFloat64(maxRect.Y.Lo, maxRect.Y.Hi),
		}
		b := r2.Point{
			randomUniformFloat64(maxRect.X.Lo, maxRect.X.Hi),
			randomUniformFloat64(maxRect.Y.Lo, maxRect.Y.Hi),
		}

		if !result.IsLeaf() {
			// If the result is not a leaf cell, we must ensure that no child of
			// result also satisfies the conditions of ShrinkToFit().  We do this
			// by ensuring that rect intersects at least two children of result
			// (after padding).
			useY := oneIn(2)
			center := result.centerUV().X
			if useY {
				center = result.centerUV().Y
			}

			// Find the range of coordinates that are shared between child cells
			// along that axis.
			shared := r1.Interval{center - padding, center + padding}
			if useY {
				shared = shared.Intersection(maxRect.Y)
			} else {
				shared = shared.Intersection(maxRect.X)
			}
			mid := randomUniformFloat64(shared.Lo, shared.Hi)

			if useY {
				a.Y = randomUniformFloat64(maxRect.Y.Lo, mid)
				b.Y = randomUniformFloat64(mid, maxRect.Y.Hi)
			} else {
				a.X = randomUniformFloat64(maxRect.X.Lo, mid)
				b.X = randomUniformFloat64(mid, maxRect.X.Hi)
			}
		}
		rect := r2.RectFromPoints(a, b)

		// Choose an arbitrary ancestor as the PaddedCell.
		initialID := result.Parent(randomUniformInt(result.Level() + 1))
		pCell := PaddedCellFromCellID(initialID, padding)
		if got := pCell.ShrinkToFit(rect); got != result {
			t.Errorf("%v.ShrinkToFit(%v) = %v, want %v", pCell, rect, got, result)
		}
	}
}
