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

package verify

import (
	"os"
	"strings"
	"testing"
)

func TestExtractSignatures(t *testing.T) {
	src := `// func add(a int64, b int64) int64
TEXT ·add(SB), NOSPLIT, $0-24
	RET

// func wideCopy(dst []byte, src []byte)
TEXT ·wideCopy(SB), NOSPLIT, $0-48
	RET
`
	sigs := ExtractSignatures(src)
	if len(sigs) != 2 {
		t.Fatalf("expected 2 signatures, got %d: %v", len(sigs), sigs)
	}
	add, ok := sigs["add"]
	if !ok {
		t.Fatal("add not found")
	}
	if len(add.params) != 2 {
		t.Errorf("add params: got %d, want 2", len(add.params))
	}
	wc, ok := sigs["wideCopy"]
	if !ok {
		t.Fatal("wideCopy not found")
	}
	if len(wc.params) != 2 {
		t.Errorf("wideCopy params: got %d, want 2", len(wc.params))
	}
	if wc.params[0].typ != "[]byte" {
		t.Errorf("wideCopy param[0].typ = %q, want []byte", wc.params[0].typ)
	}
}

func TestFuzzWideCopy(t *testing.T) {
	k := loadBasic(t)

	gt, err := GroundTruth("../testdata/verify/basic_amd64.s")
	if err != nil {
		t.Fatalf("GroundTruth: %v", err)
	}
	goCode, ok := gt["wideCopy"]
	if !ok {
		t.Skip("wideCopy not in ground truth")
	}

	sig := funcSig{
		name: "wideCopy",
		params: []param{
			{name: "dst", typ: "[]byte"},
			{name: "src", typ: "[]byte"},
		},
	}

	res := k.FuzzFunc("wideCopy", sig, goCode, 200, 42)
	if !res.OK() {
		t.Errorf("wideCopy fuzz: %s", res)
	}
}

// TestFuzzFuncSigWiderThanFrame pins the guard against a // func comment
// that declares more parameter bytes than the TEXT frame carries: before
// the guard, slicing the result area at paramsSize(sig) past the end of
// the argument block panicked the whole test binary.
func TestFuzzFuncSigWiderThanFrame(t *testing.T) {
	k := loadBasic(t)

	gt, err := GroundTruth("../testdata/verify/basic_amd64.s")
	if err != nil {
		t.Skipf("go tool asm unavailable: %v", err)
	}
	goCode, ok := gt["add"]
	if !ok {
		t.Skip("add not in ground truth")
	}

	// add carries $0-24; four int parameters declare 32 bytes.
	sig := funcSig{
		name: "add",
		params: []param{
			{name: "a", typ: "int"},
			{name: "b", typ: "int"},
			{name: "c", typ: "int"},
			{name: "d", typ: "int"},
		},
	}

	res := k.FuzzFunc("add", sig, goCode, 3, 42)
	if res.OK() {
		t.Fatal("expected the over-wide signature to fail the campaign")
	}
	if !strings.Contains(res.FirstFail, "parameter bytes") || !strings.Contains(res.FirstFail, "argument bytes") {
		t.Errorf("FirstFail = %q, want a clear signature-versus-frame message", res.FirstFail)
	}
}

// TestFuzzStringParam runs the differential fuzzer over a kernel whose
// only parameter is a string: the marshaller lays out a real two-word
// header (data pointer + length) and the comparison slices at
// paramsSize(sig) = 16, so the length word is input, not result.
func TestFuzzStringParam(t *testing.T) {
	k := loadStrProbeKernel(t)

	file := t.TempDir() + "/strprobe_amd64.s"
	if err := os.WriteFile(file, []byte(strProbeSrc), 0o644); err != nil {
		t.Fatalf("write kernel: %v", err)
	}
	gt, err := GroundTruth(file)
	if err != nil {
		t.Skipf("go tool asm unavailable: %v", err)
	}
	goCode, ok := gt["strProbe"]
	if !ok {
		t.Skip("strProbe not in ground truth")
	}

	sig, ok := parseFuncSig("// func strProbe(s string) int64")
	if !ok {
		t.Fatal("parseFuncSig failed")
	}
	res := k.FuzzFunc("strProbe", sig, goCode, 100, 42)
	if !res.OK() {
		t.Errorf("strProbe fuzz: %s", res)
	}
}

func TestParseFuncSig(t *testing.T) {
	tests := []struct {
		comment string
		name    string
		nParams int
	}{
		{"// func add(a int64, b int64) int64", "add", 2},
		{"// func wideCopy(dst []byte, src []byte)", "wideCopy", 2},
		{"// func analyzeO1RangeAVX2(swin []int32, dstP []uint32, hist *[32]uint16) (partSum uint64, overflow bool)", "analyzeO1RangeAVX2", 3},
		{"// not a func", "", 0},
	}
	for _, tt := range tests {
		sig, ok := parseFuncSig(tt.comment)
		if tt.name == "" {
			if ok {
				t.Errorf("parseFuncSig(%q): expected not ok", tt.comment)
			}
			continue
		}
		if !ok {
			t.Errorf("parseFuncSig(%q): expected ok", tt.comment)
			continue
		}
		if sig.name != tt.name {
			t.Errorf("parseFuncSig(%q).name = %q, want %q", tt.comment, sig.name, tt.name)
		}
		if len(sig.params) != tt.nParams {
			t.Errorf("parseFuncSig(%q): %d params, want %d", tt.comment, len(sig.params), tt.nParams)
		}
	}
}