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

package debug

// Regs holds the full general-purpose register set of a traced process
// (the Linux amd64 user_regs_struct layout).
type Regs struct {
	R15     uint64
	R14     uint64
	R13     uint64
	R12     uint64
	RBP     uint64
	RBX     uint64
	R11     uint64
	R10     uint64
	R9      uint64
	R8      uint64
	RAX     uint64
	RCX     uint64
	RDX     uint64
	RSI     uint64
	RDI     uint64
	OrigRAX uint64
	RIP     uint64
	CS      uint64
	RFLAGS  uint64
	RSP     uint64
	SS      uint64
	FSBase  uint64
	GSBase  uint64
	DS      uint64
	ES      uint64
	FS      uint64
	GS      uint64
}

// 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
	Pid() int
}

// mockTracer records Peek/Poke calls and provides fake register state.
type mockTracer struct {
	mem   map[uint64]byte
	peeks []uint64
	pokes []struct {
		addr uint64
		val  uint64
	}
	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 := uint64(0); i < 8; i++ {
		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 := uint64(0); i < 8; i++ {
		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) Pid() int { return 42 }