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

//go:build linux && amd64

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
}

// GetPC returns the program counter.
func (r *Regs) GetPC() uint64 { return r.RIP }

// SetPC sets the program counter.
func (r *Regs) SetPC(pc uint64) { r.RIP = pc }

// GetSP returns the stack pointer.
func (r *Regs) GetSP() uint64 { return r.RSP }

// RegValue returns the value of the named register, or false if unknown.
func (r *Regs) RegValue(name string) (uint64, bool) {
	switch name {
	case "rax", "eax", "ax", "al":
		return r.RAX, true
	case "rbx", "ebx", "bx", "bl":
		return r.RBX, true
	case "rcx", "ecx", "cx", "cl":
		return r.RCX, true
	case "rdx", "edx", "dx", "dl":
		return r.RDX, true
	case "rsi", "esi", "si":
		return r.RSI, true
	case "rdi", "edi", "di":
		return r.RDI, true
	case "rbp", "ebp", "bp":
		return r.RBP, true
	case "rsp", "esp", "sp":
		return r.RSP, true
	case "r8":
		return r.R8, true
	case "r9":
		return r.R9, true
	case "r10":
		return r.R10, true
	case "r11":
		return r.R11, true
	case "r12":
		return r.R12, true
	case "r13":
		return r.R13, true
	case "r14":
		return r.R14, true
	case "r15":
		return r.R15, true
	case "rip", "eip":
		return r.RIP, true
	default:
		return 0, false
	}
}

// breakpointInsn is the software breakpoint instruction.
var breakpointInsn = []byte{0xCC} // INT3

// breakpointPCAdjust is how far PC is past the breakpoint instruction after a trap.
const breakpointPCAdjust = 1