// Copyright ©2016 The Gonum Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package testlapack

import (
	"fmt"
	"math/rand/v2"
	"testing"

	"gonum.org/v1/gonum/blas"
	"gonum.org/v1/gonum/blas/blas64"
	"gonum.org/v1/gonum/lapack"
)

type Dlaqr5er interface {
	Dlaqr5(wantt, wantz bool, kacc22 int, n, ktop, kbot, nshfts int, sr, si []float64, h []float64, ldh int, iloz, ihiz int, z []float64, ldz int, v []float64, ldv int, u []float64, ldu int, nh int, wh []float64, ldwh int, nv int, wv []float64, ldwv int)
}

func Dlaqr5Test(t *testing.T, impl Dlaqr5er) {
	rnd := rand.New(rand.NewPCG(1, 1))
	for _, n := range []int{1, 2, 3, 4, 5, 6, 10, 30} {
		for _, extra := range []int{0, 1, 20} {
			for _, kacc22 := range []int{0, 1, 2} {
				for cas := 0; cas < 100; cas++ {
					testDlaqr5(t, impl, n, extra, kacc22, rnd)
				}
			}
		}
	}
}

func testDlaqr5(t *testing.T, impl Dlaqr5er, n, extra, kacc22 int, rnd *rand.Rand) {
	const tol = 1e-14

	wantt := true
	wantz := true
	nshfts := 2 * n
	sr := make([]float64, nshfts)
	si := make([]float64, nshfts)
	for i := 0; i < nshfts; {
		if i == nshfts-1 || rnd.Float64() < 0.5 {
			re := rnd.NormFloat64()
			sr[i], si[i] = re, 0
			i++
			continue
		}
		re := rnd.NormFloat64()
		im := rnd.NormFloat64()
		sr[i], sr[i+1] = re, re
		si[i], si[i+1] = im, -im
		i += 2
	}
	ktop := rnd.IntN(n)
	kbot := rnd.IntN(n)
	if kbot < ktop {
		ktop, kbot = kbot, ktop
	}

	v := randomGeneral(nshfts/2, 3, 3+extra, rnd)
	u := randomGeneral(2*nshfts, 2*nshfts, 2*nshfts+extra, rnd)
	nh := n
	wh := randomGeneral(2*nshfts, n, n+extra, rnd)
	nv := n
	wv := randomGeneral(n, 2*nshfts, 2*nshfts+extra, rnd)

	h := randomHessenberg(n, n+extra, rnd)
	if ktop > 0 {
		h.Data[ktop*h.Stride+ktop-1] = 0
	}
	if kbot < n-1 {
		h.Data[(kbot+1)*h.Stride+kbot] = 0
	}
	hCopy := h
	hCopy.Data = make([]float64, len(h.Data))
	copy(hCopy.Data, h.Data)

	z := eye(n, n+extra)

	impl.Dlaqr5(wantt, wantz, kacc22,
		n, ktop, kbot,
		nshfts, sr, si,
		h.Data, h.Stride,
		0, n-1, z.Data, z.Stride,
		v.Data, v.Stride,
		u.Data, u.Stride,
		nv, wv.Data, wv.Stride,
		nh, wh.Data, wh.Stride)

	prefix := fmt.Sprintf("Case n=%v, extra=%v, kacc22=%v", n, extra, kacc22)

	if !generalOutsideAllNaN(h) {
		t.Errorf("%v: out-of-range write to H\n%v", prefix, h.Data)
	}
	if !generalOutsideAllNaN(z) {
		t.Errorf("%v: out-of-range write to Z\n%v", prefix, z.Data)
	}
	if !generalOutsideAllNaN(u) {
		t.Errorf("%v: out-of-range write to U\n%v", prefix, u.Data)
	}
	if !generalOutsideAllNaN(v) {
		t.Errorf("%v: out-of-range write to V\n%v", prefix, v.Data)
	}
	if !generalOutsideAllNaN(wh) {
		t.Errorf("%v: out-of-range write to WH\n%v", prefix, wh.Data)
	}
	if !generalOutsideAllNaN(wv) {
		t.Errorf("%v: out-of-range write to WV\n%v", prefix, wv.Data)
	}

	for i := 0; i < n; i++ {
		for j := 0; j < i-1; j++ {
			if h.Data[i*h.Stride+j] != 0 {
				t.Errorf("%v: H is not Hessenberg, H[%v,%v]!=0", prefix, i, j)
			}
		}
	}
	// Check that Z is orthogonal.
	if resid := residualOrthogonal(z, false); resid > tol*float64(n) {
		t.Errorf("Case %v: Z is not orthogonal; resid=%v, want<=%v", prefix, resid, tol*float64(n))
	}
	// Check that |Zᵀ*HOrig*Z - H| is small where H is the result from Dlaqr5.
	hz := zeros(n, n, n)
	blas64.Gemm(blas.NoTrans, blas.NoTrans, 1, hCopy, z, 0, hz)
	zhz := cloneGeneral(h)
	blas64.Gemm(blas.Trans, blas.NoTrans, 1, z, hz, -1, zhz)
	resid := dlange(lapack.MaxColumnSum, n, n, zhz.Data, zhz.Stride)
	if resid > tol*float64(n) {
		t.Errorf("%v: |Zᵀ*HOrig*Z - H|=%v, want<=%v", prefix, resid, tol*float64(n))
	}
}