// Copyright 2025 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package windows

import (
	"internal/goarch"
	"unsafe"
)

// NOTE(rsc): CONTEXT_CONTROL is actually 0x400001 and should include PC, SP, and LR.
// However, empirically, LR doesn't come along on Windows 10
// unless you also set CONTEXT_INTEGER (0x400002).
// Without LR, we skip over the next-to-bottom function in profiles
// when the bottom function is frameless.
// So we set both here, to make a working CONTEXT_CONTROL.
const CONTEXT_CONTROL = 0x400003

type Neon128 struct {
	Low  uint64
	High int64
}

// See https://docs.microsoft.com/en-us/windows/win32/api/winnt/ns-winnt-arm64_nt_context
type Context struct {
	ContextFlags uint32
	Cpsr         uint32
	X            [31]uint64 // fp is x[29], lr is x[30]
	XSp          uint64
	Pc           uint64
	V            [32]Neon128
	Fpcr         uint32
	Fpsr         uint32
	Bcr          [8]uint32
	Bvr          [8]uint64
	Wcr          [2]uint32
	Wvr          [2]uint64
}

func (c *Context) PC() uintptr { return uintptr(c.Pc) }
func (c *Context) SP() uintptr { return uintptr(c.XSp) }
func (c *Context) LR() uintptr { return uintptr(c.X[30]) }

func (c *Context) SetPC(x uintptr) { c.Pc = uint64(x) }
func (c *Context) SetSP(x uintptr) { c.XSp = uint64(x) }
func (c *Context) SetLR(x uintptr) { c.X[30] = uint64(x) }
func (c *Context) SetFP(x uintptr) { c.X[29] = uint64(x) }

func (c *Context) PushCall(targetPC, resumePC uintptr) {
	// Push LR. The injected call is responsible
	// for restoring LR. gentraceback is aware of
	// this extra slot. See sigctxt.pushCall in
	// signal_arm64.go.
	sp := c.SP() - goarch.StackAlign
	c.SetSP(sp)
	*(*uint64)(unsafe.Pointer(sp)) = uint64(c.LR())
	c.SetLR(resumePC)
	c.SetPC(targetPC)
}

type DISPATCHER_CONTEXT struct {
	ControlPc        uint64
	ImageBase        uint64
	FunctionEntry    uintptr
	EstablisherFrame uint64
	TargetIp         uint64
	Context          *Context
	LanguageHandler  uintptr
	HandlerData      uintptr
}

func (c *DISPATCHER_CONTEXT) Ctx() *Context {
	return c.Context
}