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

//go:build linux || (freebsd && (amd64 || arm64 || riscv64))

package debug

import (
	"os"
	"path/filepath"
)

// markDead records the target's failure reason in the handshake directory,
// the death notice the debugger's readiness poll reads.  The poll must not
// wait on the child while it polls: a wait there could consume the SIGSTOP
// park the debugger's own waitStopped must receive, hanging the launch, so
// the file is the only fast death notice that is safe to read.  A debuggee
// killed without a notice (a crash, SIGKILL) surfaces through the ordinary
// wait after the poll instead.
func markDead(tmpDir, reason string) {
	os.WriteFile(filepath.Join(tmpDir, "dead"), []byte(reason), 0o644)
}

// tracer abstracts the minimal ptrace operations needed by the breakpoint
// manager and the stop-information helpers.  The live implementation is
// *Session (ptrace_linux_amd64.go); tests supply a mock.
type tracer interface {
	Peek(addr uint64) (uint64, error)
	Poke(addr uint64, val uint64) error
	SetRegs(regs *Regs) error
	Step() error
	Pid() int
}

// mockTracer records Peek/Poke/Step calls and provides fake register state.
type mockTracer struct {
	mem   map[uint64]byte
	peeks []uint64
	pokes []struct {
		addr uint64
		val  uint64
	}
	steps int
	regs  *Regs
}

func newMockTracer() *mockTracer {
	return &mockTracer{
		mem:  make(map[uint64]byte),
		regs: &Regs{},
	}
}

func (m *mockTracer) Peek(addr uint64) (uint64, error) {
	m.peeks = append(m.peeks, addr)
	var val uint64
	for i := range uint64(8) {
		val |= uint64(m.mem[addr+i]) << (i * 8)
	}
	return val, nil
}

func (m *mockTracer) Poke(addr uint64, val uint64) error {
	m.pokes = append(m.pokes, struct {
		addr uint64
		val  uint64
	}{addr, val})
	for i := range uint64(8) {
		m.mem[addr+i] = byte(val >> (i * 8))
	}
	return nil
}

func (m *mockTracer) SetRegs(regs *Regs) error {
	m.regs = regs
	return nil
}
func (m *mockTracer) Step() error {
	m.steps++
	return nil
}
func (m *mockTracer) Pid() int { return 42 }