// Copyright 2016 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 runtime

import (
	"runtime/internal/atomic"
	"syscall/zx"
	"unsafe"
)

//go:nosplit
func cputicks() int64 {
	return int64(zx.Sys_ticks_get())
}

type mOS struct{}

type sigset struct{}

//go:nosplit
func getRandomData(r []byte) {
	zx.RandRead(r)
}

//go:nosplit
func futexsleep(addr *uint32, val uint32, ns int64) {
	deadline := zx.Sys_deadline_after(zx.Duration(ns))
	if ns < 0 {
		deadline = zx.Time(zx.TimensecInfinite)
	}
	zx.Sys_futex_wait((*int32)(unsafe.Pointer(addr)), int32(val), zx.HandleInvalid, deadline)
}

//go:nosplit
func futexwakeup(addr *uint32, cnt uint32) {
	zx.Sys_futex_wake((*int32)(unsafe.Pointer(addr)), cnt)
}

//go:nosplit
func osyield() {
	zx.Sys_nanosleep(0)
}

// cgocallm0 calls a C function on the current stack.
//
// It is intended for use inside functions like osinit that run
// before mstart directly on an OS thread stack.
//
// If in doubt, do not use.
func cgocallm0(fn, arg unsafe.Pointer)

func osinit() {
	if _cgo_get_initial_handles != nil {
		cgocallm0(_cgo_get_initial_handles, unsafe.Pointer(&fdioHandles))
		for i := 0; i < 3; i = i + 1 {
			zx.StdioHandles[i] = fdioHandles.stdioClones[i]
			zx.StdioHandleTypes[i] = int(fdioHandles.stdioCloneTypes[i])
		}
		zx.ProcHandle = zx.Handle(fdioHandles.processSelf)
		zx.VMARRoot = zx.VMAR(fdioHandles.vmarRootSelf)
	} else {
		// TODO: implement cgo-less init
		println("runtime: no fuchsia process handle without cgo yet")
		exit(2)
	}

	ncpu = int32(zx.Sys_system_get_num_cpus())
	physPageSize = 4096
}

func parseRootNS() {
	if fdioHandles.rootNSNumHandles > 0 {
		const maxHandleCount = 1 << 20 // arbitrary
		paths := (*(*[maxHandleCount]*byte)(unsafe.Pointer(fdioHandles.rootNSPaths)))[:fdioHandles.rootNSNumHandles]
		handles := (*(*[maxHandleCount]zx.Handle)(unsafe.Pointer(fdioHandles.rootNSHandles)))[:fdioHandles.rootNSNumHandles]
		zx.RootNSMap = make(map[string]zx.Handle)
		for i, p := range paths {
			zx.RootNSMap[gostring(p)] = handles[i]
		}
	}
}

// Filled in by runtime/cgo when linked into binary.

var (
	_cgo_get_initial_handles    unsafe.Pointer
	_cgo_get_thread_self_handle unsafe.Pointer
)

//go:nosplit
func minit() {
	var h zx.Handle
	asmcgocall(_cgo_get_thread_self_handle, unsafe.Pointer(&h))
	atomic.Storeuintptr(&getg().m.thread, uintptr(h))
}

//go:nosplit
func unminit() {
	// TODO
}

func sigpanic() {
	// TODO
}

func mpreinit(mp *m) {
	// TODO
}

//go:nosplit
func msigsave(mp *m) {
	// TODO
}

//go:nosplit
func msigrestore(sigmask sigset) {
	// TODO
}

func initsig(preinit bool) {
	// TODO
}

//go:nosplit
func sigblock() {
	// TODO
}

func sigenable(sig uint32) {
	// TODO
}

func sigdisable(sig uint32) {
	// TODO
}

func sigignore(sig uint32) {
	// TODO
}

func crash() {
	*(*int32)(nil) = 0
}

func threadinit(mp *m)

var gothreadname = []byte("gothread")

//go:nowritebarrier
func newosproc(mp *m) {
	stk := unsafe.Pointer(mp.g0.stack.hi)
	p := zx.Handle(0) // TODO: only works due to temporary hack in zircon
	var h zx.Handle
	status := zx.Sys_thread_create(p, &gothreadname[0], uint(len(gothreadname)), 0, &h)
	if status < 0 {
		println("runtime: newosproc zx.Sys_thread_create failed:", h)
		exit(2)
	}

	mp.thread = uintptr(h)

	status = zx.Sys_thread_start(h, zx.Vaddr(funcPC(threadinit)), zx.Vaddr(stk), uintptr(unsafe.Pointer(mp)), 0)
	if status < 0 {
		println("runtime: newosproc zx.Sys_thread_start failed:", h)
		exit(2)
	}
}

type zx_proc_args struct {
	protocol        uint32
	version         uint32
	handle_info_off uint32
	args_off        uint32
	args_num        uint32
}

type zx_proc_info struct {
	magic         uint32
	version       uint32
	next_tls_slot uint32
	proc_args     *zx_proc_args
	handle        *zx.Handle
	handle_info   *uint32
	handle_count  int32
	argv          **byte
	argc          int32
}

type zx_tls_root struct {
	self     *zx_tls_root
	proc     *zx_proc_info
	magic    uint32
	flags    uint16
	maxslots uint16
	slots    [8]uintptr // has length maxslots
}

func resetcpuprofiler(hz int32) {
	// TODO
}

// fdio_init matches a Go struct of the same name in gcc_fdio.c.
type fdio_init struct {
	stdioClones          [3]zx.Handle
	stdioCloneNumHandles [3]uint32
	stdioCloneTypes      [3]uint32
	processSelf          zx.Handle
	vmarRootSelf         zx.Handle
	envlen               int32
	environ              **byte
	_                    [4]byte
	rootNSNumHandles     int32
	rootNSHandles        *zx.Handle
	rootNSPaths          **byte
}

var fdioHandles fdio_init

func goenvs() {
	if _cgo_get_initial_handles != nil {
		const maxEnvSize = 1 << 20 // arbitrary
		envp := (*(*[maxEnvSize]*byte)(unsafe.Pointer(fdioHandles.environ)))[:fdioHandles.envlen]
		envs = make([]string, len(envp))
		for i, e := range envp {
			envs[i] = gostring(e)
		}
		// TODO: find a better place to call this
		parseRootNS()
	} else {
		// TODO: implement cgo-less init
		println("runtime: no fuchsia process handle without cgo yet")
		exit(2)
	}
}

const _NSIG = 65 // TODO

const (
	ZX_CLOCK_MONOTONIC           = 0
	ZX_HANDLE_INVALID            = 0
	ZX_INFO_THREAD               = uint32(10)
	ZX_OK                        = int32(0)
	ZX_THREAD_STATE_GENERAL_REGS = uint32(0)
	ZX_THREAD_STATE_NEW          = uint32(0)
	ZX_THREAD_SUSPENDED          = uint32(1 << 5)
	ZX_THREAD_TERMINATED         = uint32(1 << 3)
	ZX_TIME_INFINITE             = int64(^uint64(1 << 63))
	ZX_TIMER_SIGNALED            = uint32(1 << 3)
	ZX_TIMER_SLACK_EARLY         = 1
)

//go:nosplit
func nanotime() int64 {
	return int64(zx.Sys_clock_get_monotonic())
}

//go:linkname time_now time.now
//go:nosplit
func time_now() (sec int64, nsec int32, mono int64) {
	const ZX_CLOCK_UTC = 1
	var x zx.Time
	zx.Sys_clock_get(ZX_CLOCK_UTC, &x)
	return int64(x / 1e9), int32(x % 1e9), nanotime()
}

func unixnanotime() int64 {
	return nanotime()
}

// #define LOGBUF_MAX (ZX_LOG_RECORD_MAX - sizeof(zx_log_record_t))
const logBufMax = 224

var logger zx.Handle
var logBufferArray [logBufMax]byte
var logBufferN int

//go:nosplit
func write(fd uintptr, buf unsafe.Pointer, n int32) int32 {
	if fd != 1 && fd != 2 {
		panic("runtime.write(): can not write to non-log fd")
	}

	// This initialization mechanism is not thread-safe, but if the only calls to 'write' with
	// these file descriptors come from print, they will already be serialized by a lock in
	// print's implementation.
	if logger <= 0 {
		zx.Sys_debuglog_create(0, 0, &logger)
		logBufferN = 0
	}
	// Ideally this should panic, but that would go down "blind", which is arguably worse.
	if logger <= 0 {
		return -1
	}

	for i := int32(0); i < n; i++ {
		c := *(*byte)(unsafe.Pointer(uintptr(buf) + uintptr(i)))

		if c == '\n' {
			zx.Sys_debuglog_write(logger, 0, unsafe.Pointer(&logBufferArray[0]), uint(logBufferN))
			logBufferN = 0
			continue
		}

		if c < ' ' {
			continue
		}

		logBufferArray[logBufferN] = c
		logBufferN++

		if logBufferN == len(logBufferArray) {
			zx.Sys_debuglog_write(logger, 0, unsafe.Pointer(&logBufferArray[0]), uint(logBufferN))
			logBufferN = 0
		}
	}

	return n
}

//go:nosplit
func exit(code int32) {
	zx.Sys_process_exit(int64(code))
}

//go:nosplit
func usleep(usec uint32) {
	zx.Sys_nanosleep(zx.Sys_deadline_after(zx.Duration(usec * 1000)))
}

func signame(sig uint32) string {
	return "unknown_sig" // TODO
}

// zircon_mktls
//go:nosplit
func zircon_mktls() {
	// TODO
}

//go:nosplit
func zircon_settls(val uintptr) {
	// TODO: should call zx_set_object_property with property ZX_PROP_REGISTER_FS in amd64 or
	// ZX_PROP_REGISTER_CP15 on arm.
}

//go:linkname os_sigpipe os.sigpipe
func os_sigpipe() {
	// TODO
}

// gsignalStack is unused on fuchsia
type gsignalStack struct{}

const (
	profStkSize = uintptr(1 << 16)
)

var (
	profTimer   uint32 // timer handle
	profThread  uint32 // thread handle
	profHz      = ZX_TIME_INFINITE
	profName    = []byte("profiler")
	profStk     unsafe.Pointer
	profStkFail = []byte("runtime: failed to allocate stack for the new OS thread\n")
)

type zxCpuSet struct {
	mask [16]uint32
}

type zxInfoThread struct {
	state                 uint32
	waitExceptionPortType uint32
	affinityMask          zxCpuSet
}

//go:noescape
//go:nosplit
func profiler_object_wait_one(handle uint32, signals uint32, deadline int64, observed *uint32) int32

func profilem(mp *m, thread uint32) {
	// Ignore nascent threads.
	var observed uint32
	var info zxInfoThread
	var actualSize uint64
	var availSize uint64
	if status := vdsoCall_zx_object_get_info(thread, ZX_INFO_THREAD, unsafe.Pointer(&info), uint(unsafe.Sizeof(info)), unsafe.Pointer(&actualSize), unsafe.Pointer(&availSize)); status != ZX_OK {
		return
	}
	if info.state == ZX_THREAD_STATE_NEW {
		return
	}

	// Wait for the thread to be suspended.
	if status := profiler_object_wait_one(thread, ZX_THREAD_SUSPENDED|ZX_THREAD_TERMINATED, ZX_TIME_INFINITE, &observed); status != ZX_OK {
		return
	}

	// Ignore threads that were terminated as a result of suspension.
	if observed&ZX_THREAD_TERMINATED == ZX_THREAD_TERMINATED {
		return
	}

	var r generalRegs
	if status := vdsoCall_zx_thread_read_state(thread, ZX_THREAD_STATE_GENERAL_REGS, unsafe.Pointer(&r), uint(unsafe.Sizeof(r))); status != ZX_OK {
		return
	}

	if mp.curg != nil {
		sigprof(r.rPC(), r.rSP(), r.rLR(), mp.curg, mp)
	} else {
		sigprofNonGoPC(r.rPC())
	}
}

// profileLoop is called when pprof CPU tracing is enabled. It runs without a p, hence nowritebarrierrec.
//
//go:nosplit
//go:nowritebarrierrec
func profileLoop() {
	me := getg().m
	for {
		var observed uint32
		if status := profiler_object_wait_one(profTimer, ZX_TIMER_SIGNALED, ZX_TIME_INFINITE, &observed); status != ZX_OK {
			continue
		}

		// Scan over all threads and suspend them, then trace. Ideally, we'd scan over
		// all of them and give them a chance to suspend before this, but I don't want
		// to deal with allocation here.
		first := (*m)(atomic.Loadp(unsafe.Pointer(&allm)))
		for mp := first; mp != nil; mp = mp.alllink {
			thread := uint32(atomic.Loaduintptr(&mp.thread))
			// Do not profile threads blocked on Notes (this includes idle worker threads, idle timer thread,
			// idle heap scavenger, etc.). Do not profile this thread.
			if thread == ZX_HANDLE_INVALID || mp.profilehz == 0 || mp.blocked || mp == me {
				continue
			}

			var token uint32
			if status := vdsoCall_zx_task_suspend_token(thread, unsafe.Pointer(&token)); status == ZX_OK {
				profilem(mp, thread)
			}
			vdsoCall_zx_handle_close(token)

		}

		due := vdsoCall_zx_deadline_after(profHz)
		if status := vdsoCall_zx_timer_set(profTimer, due, ZX_TIMER_SLACK_EARLY); status != ZX_OK {
			// TODO: what do?
			return
		}
	}
}

// profileloop is defined in sys_fuchsia_{amd,arm}64.s
func profileloop()

func setProcessCPUProfiler(hz int32) {
	// This function is entered in the critical section guarded by
	// prof.signalLock in proc.go and is thus safe to assume the profiler's
	// timer is created atomically.
	if profTimer == ZX_HANDLE_INVALID {
		if status := vdsoCall_zx_timer_create(ZX_TIMER_SLACK_EARLY, ZX_CLOCK_MONOTONIC, unsafe.Pointer(&profTimer)); status != ZX_OK {
			// TODO: what do?
			return
		}

		newm(profileLoop, nil)
	}
}

func setThreadCPUProfiler(hz int32) {
	// Don't do anything if we don't have a timer yet.
	if profTimer == ZX_HANDLE_INVALID {
		return
	}

	atomic.Store((*uint32)(unsafe.Pointer(&getg().m.profilehz)), uint32(hz))

	if hz > 0 {
		ns := int64(int64(1000000000) / int64(hz))
		// Bound tracing frequency to microseconds. This is likely
		// already well above the granularity traces can actually
		// provide.
		if ns < 1000 {
			ns = 1000
		}

		profHz = ns
		due := vdsoCall_zx_deadline_after(ns)
		if status := vdsoCall_zx_timer_set(profTimer, due, ZX_TIMER_SLACK_EARLY); status != ZX_OK {
			// TODO: what do?
			return
		}
	} else {
		if status := vdsoCall_zx_timer_cancel(profTimer); status != ZX_OK {
			return
		}
	}
}

func exitThread(wait *uint32) {}

//go:nosplit
//go:nowritebarrierrec
func clearSignalHandlers() {}