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

package lint

import "testing"

// TestRegisterClobber detects writes to callee-saved registers that are not
// saved and restored.
func TestRegisterClobber(t *testing.T) {
	// BX (callee-saved on amd64) is written but never saved → clobbered.
	clob := lintSrc(t, "#include \"textflag.h\"\n"+
		"TEXT ·f(SB), NOSPLIT, $0\n"+
		"\tMOVQ CX, BX\n"+
		"\tRET\n")
	if codes(clob)[CodeRegisterClobber] != 1 {
		t.Fatalf("unsaved callee-saved write should be flagged: %+v", clob)
	}

	// Saved and restored → preserved.
	saved := lintSrc(t, "#include \"textflag.h\"\n"+
		"TEXT ·f(SB), NOSPLIT, $8\n"+
		"\tPUSHQ BX\n"+
		"\tMOVQ CX, BX\n"+
		"\tPOPQ BX\n"+
		"\tRET\n")
	if codes(saved)[CodeRegisterClobber] != 0 {
		t.Fatalf("saved/restored register must not be flagged: %+v", saved)
	}

	// A caller-saved register (CX) is fine to write.
	caller := lintSrc(t, "#include \"textflag.h\"\n"+
		"TEXT ·f(SB), NOSPLIT, $0\n"+
		"\tMOVQ $1, CX\n"+
		"\tRET\n")
	if codes(caller)[CodeRegisterClobber] != 0 {
		t.Fatalf("caller-saved register must not be flagged: %+v", caller)
	}
}

// TestFuncdata validates the FUNCDATA/PCDATA structural checks.
func TestFuncdata(t *testing.T) {
	// Well formed: no findings.
	good := lintSrc(t, "#include \"textflag.h\"\n"+
		"TEXT ·f(SB), NOSPLIT, $0\n"+
		"\tFUNCDATA $0, gclocals·abc(SB)\n"+
		"\tPCDATA $1, $0\n"+
		"\tRET\n")
	if codes(good)[CodeFuncdata] != 0 {
		t.Fatalf("well-formed FUNCDATA/PCDATA must not be flagged: %+v", good)
	}

	// FUNCDATA with one operand.
	bad1 := lintSrc(t, "#include \"textflag.h\"\n"+
		"TEXT ·f(SB), NOSPLIT, $0\n"+
		"\tFUNCDATA $0\n"+
		"\tRET\n")
	if codes(bad1)[CodeFuncdata] == 0 {
		t.Fatal("FUNCDATA with one operand should be flagged")
	}

	// PCDATA with a non-immediate value.
	bad2 := lintSrc(t, "#include \"textflag.h\"\n"+
		"TEXT ·f(SB), NOSPLIT, $0\n"+
		"\tPCDATA $0, AX\n"+
		"\tRET\n")
	if codes(bad2)[CodeFuncdata] == 0 {
		t.Fatal("PCDATA with a register value should be flagged")
	}

	// FUNCDATA index out of range.
	bad3 := lintSrc(t, "#include \"textflag.h\"\n"+
		"TEXT ·f(SB), NOSPLIT, $0\n"+
		"\tFUNCDATA $99, gclocals·abc(SB)\n"+
		"\tRET\n")
	if codes(bad3)[CodeFuncdata] == 0 {
		t.Fatal("out-of-range FUNCDATA index should be flagged")
	}
}