// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
// SPDX-License-Identifier: BSD-3-Clause

package verify

import (
	"bytes"
	"os"
	"testing"

	"sourcedock.dev/petrbalvin/gasm-devkit/asm"
	"sourcedock.dev/petrbalvin/gasm-devkit/parser"
)

func mustRead(t *testing.T, path string) string {
	t.Helper()
	b, err := os.ReadFile(path)
	if err != nil {
		t.Fatalf("read: %v", err)
	}
	return string(b)
}

func TestGroundTruthBasic(t *testing.T) {
	// Use the simple test kernel; it assembles with go tool asm.
	gt, err := GroundTruth("../testdata/verify/basic_amd64.s")
	if err != nil {
		t.Fatalf("GroundTruth: %v", err)
	}
	if len(gt) == 0 {
		t.Fatal("no functions extracted from ground truth")
	}
	// The "add" function should be present and non-empty.
	code, ok := gt["add"]
	if !ok {
		t.Fatalf("function 'add' not found in ground truth; got: %v", keys(gt))
	}
	if len(code) == 0 {
		t.Fatal("add: zero-length code")
	}
	t.Logf("ground truth functions: %v", keys(gt))
}

func TestGroundTruthComparison(t *testing.T) {
	// Assemble with gasm and compare against go tool asm.
	k, err := Load("../testdata/verify/basic_amd64.s")
	if err != nil {
		t.Fatalf("Load: %v", err)
	}
	defer k.Close()

	gt, err := GroundTruth("../testdata/verify/basic_amd64.s")
	if err != nil {
		t.Fatalf("GroundTruth: %v", err)
	}

	for _, name := range k.FuncNames() {
		fl, _ := k.Func(name)
		gasmCode := k.Image().Code[fl.Offset : fl.Offset+fl.Size]
		goCode, ok := gt[name]
		if !ok {
			t.Errorf("%s: not in ground truth", name)
			continue
		}
		if len(gasmCode) != len(goCode) {
			t.Errorf("%s: size mismatch: gasm=%d go=%d", name, len(gasmCode), len(goCode))
			continue
		}
		for i := range gasmCode {
			if gasmCode[i] != goCode[i] {
				t.Errorf("%s: byte %d differs: gasm=%02x go=%02x", name, i, gasmCode[i], goCode[i])
				break
			}
		}
	}
}

func TestGroundTruthBadFile(t *testing.T) {
	_, err := GroundTruth("/nonexistent/file_amd64.s")
	if err == nil {
		t.Fatal("expected error for nonexistent file")
	}
}

// TestGroundTruthCrossEnvGOARCH checks that a GOARCH exported in the
// ambient environment does not override cross-assembly: the child
// assembler must honour the requested GOARCH even when the environment
// already carries a GOARCH entry (os.Getenv reads the first entry, so a
// duplicate would win).
func TestGroundTruthCrossEnvGOARCH(t *testing.T) {
	t.Setenv("GOARCH", "amd64")
	gt, err := GroundTruthARM64("../testdata/verify/basic_arm64.s")
	if err != nil {
		t.Fatalf("GroundTruthARM64 with ambient GOARCH=amd64: %v", err)
	}
	if len(gt) == 0 {
		t.Fatal("no functions extracted from ground truth")
	}
}

func keys(m map[string][]byte) []string {
	out := make([]string, 0, len(m))
	for k := range m {
		out = append(out, k)
	}
	return out
}

// TestGroundTruthAMD64 runs the amd64 kernels through the same live
// comparison the other arches use: gasm output versus go tool asm output,
// with relocation fields masked on both sides.
func TestGroundTruthAMD64(t *testing.T) {
	for _, path := range []string{
		"../testdata/verify/basic_amd64.s",
		"../testdata/verify/bigframe_amd64.s",
		"../testdata/verify/guard_amd64.s",
		"../testdata/verify/indirect_amd64.s",
		"../testdata/verify/widen_amd64.s",
		"../testdata/verify/scalar_amd64.s",
		"../testdata/verify/atomics_amd64.s",
		"../testdata/verify/system_amd64.s",
		"../testdata/verify/crypto_amd64.s",
		"../testdata/verify/sse_amd64.s",
		"../testdata/verify/avx_amd64.s",
		"../testdata/verify/pfx_amd64.s",
		"../testdata/verify/vsib_amd64.s",
		"../testdata/verify/floatimm_amd64.s",
		"../testdata/verify/bookkeep_amd64.s",
		"../testdata/verify/quadreg_amd64.s",
		"../testdata/verify/rawdata_amd64.s",
		"../testdata/verify/avx512_amd64.s",
		"../testdata/verify/pfx_amd64.s",
		"../testdata/verify/vsib_amd64.s",
		"../testdata/verify/floatimm_amd64.s",
		"../testdata/verify/bookkeep_amd64.s",
		"../testdata/verify/quadreg_amd64.s",
		"../testdata/verify/rawdata_amd64.s",
		"../testdata/verify/avx512_amd64.s",
		"../testdata/verify/doubleshift_amd64.s",
		"../testdata/verify/ssestatic_amd64.s",
	} {
		t.Run(path, func(t *testing.T) {
			f, errs := parser.Parse(path, mustRead(t, path))
			if len(errs) > 0 {
				t.Fatalf("parse: %v", errs)
			}
			img, err := asm.AssembleFile(f)
			if err != nil {
				t.Fatalf("AssembleFile: %v", err)
			}
			gt, err := GroundTruth(path)
			if err != nil {
				t.Fatalf("GroundTruth: %v", err)
			}
			matched := 0
			for _, fn := range img.Funcs {
				gasmCode := maskRelocs(append([]byte(nil), img.Code[fn.Offset:fn.Offset+fn.Size]...), fn.Relocs)
				goCode, ok := gt[fn.Name]
				if !ok {
					t.Errorf("%s: not in ground truth (%d functions)", fn.Name, len(gt))
					continue
				}
				goCode = maskRelocs(goCode, fn.Relocs)
				if !bytes.Equal(gasmCode, goCode) {
					t.Errorf("%s: MISMATCH gasm=%d go=%d bytes\n%s", fn.Name, len(gasmCode), len(goCode), diffHex(gasmCode, goCode))
					continue
				}
				matched++
			}
			if matched == 0 {
				t.Fatal("no functions matched")
			}
		})
	}
}