//go:build linux

package agent

// probe_linux.go is the Linux sampler for the probe collector: host
// Facts and per-heartbeat Metrics read directly from /proc and /sys
// with the standard library only. The accounting discipline (see
// probe.go) is the source's:
//   - memory "used" is free(1)'s column: MemTotal - MemAvailable;
//   - disk "used" is df(1)'s: sum over real mounts of (f_blocks-f_bfree);
//   - network totals sum only "counted" interfaces, selected by the
//     three-layer filter below so no byte is counted twice;
//   - boot epoch = kernel boot_id + fingerprint of the counted set.

import (
	"net"
	"os"
	"path/filepath"
	"runtime"
	"strconv"
	"strings"
	"syscall"
	"time"

	"github.com/mhsanaei/3x-ui/v3/internal/config"
)

func sampleFacts() *ProbeFacts {
	mem := parseMeminfo(readProcFile("meminfo"))
	diskTotal, _ := diskUsage(realMountPoints(readProcFile("self/mounts")))
	cpuName, cpuCores := cpuInfo(readProcFile("cpuinfo"))
	v4, v6 := probeAddresses()
	return &ProbeFacts{
		Hostname:     readTrimFile("/proc/sys/kernel/hostname", "unknown"),
		OS:           osPrettyName(),
		Kernel:       readTrimFile("/proc/sys/kernel/osrelease", "unknown"),
		Arch:         runtime.GOARCH,
		Virt:         detectVirt(readProcFile("self/mounts"), readProcFile("cpuinfo")),
		CPUName:      cpuName,
		CPUCores:     cpuCores,
		MemTotal:     mem["MemTotal"],
		SwapTotal:    mem["SwapTotal"],
		DiskTotal:    diskTotal,
		AgentVersion: config.GetAgentDisplayVersion(),
		IPv4:         v4,
		IPv6:         v6,
	}
}

// collectMetrics takes one full sample. Individual sources fail soft.
func collectMetrics() *ProbeMetrics {
	probeColl.mu.Lock()
	defer probeColl.mu.Unlock()
	mem := parseMeminfo(readProcFile("meminfo"))
	memTotal, memUsed := memUsedFree(mem)
	swapTotal, swapUsed := swapUsedFree(mem)
	diskTotal, diskUsed := diskUsage(realMountPoints(readProcFile("self/mounts")))
	allIfaces := parseNetDev(readProcFile("net/dev"))
	counted := countedInterfaces(allIfaces, sysNetRoot)
	if pin := statIfacePinValue(); pin != "" {
		counted = pinnedInterfaces(allIfaces, pin)
	}
	var rxTotal, txTotal uint64
	names := make([]string, 0, len(counted))
	for _, c := range counted {
		rxTotal += c.rx
		txTotal += c.tx
		names = append(names, c.name)
	}
	bootID := bootEpoch(readTrimFile("/proc/sys/kernel/random/boot_id", ""), names)
	rxRate, txRate := probeColl.netRate(counted, time.Now())
	tcp, udp := connCounts(readProcFile("net/sockstat"), readProcFile("net/sockstat6"))
	return &ProbeMetrics{
		BootID:     bootID,
		Uptime:     parseUptime(readProcFile("uptime")),
		CPU:        probeColl.cpuPercent(parseCPUJiffies(readProcFile("stat"))),
		Load:       parseLoadavg(readProcFile("loadavg")),
		MemTotal:   memTotal,
		MemUsed:    memUsed,
		SwapTotal:  swapTotal,
		SwapUsed:   swapUsed,
		DiskTotal:  diskTotal,
		DiskUsed:   diskUsed,
		NetRxTotal: rxTotal,
		NetTxTotal: txTotal,
		NetRx:      rxRate,
		NetTx:      txRate,
		TCP:        tcp,
		UDP:        udp,
		Procs:      procCount(),
	}
}

// --- file helpers -----------------------------------------------------------

const sysNetRoot = "/sys/class/net"

func readProcFile(name string) string {
	b, err := os.ReadFile(filepath.Join("/proc", name))
	if err != nil {
		return ""
	}
	return string(b)
}

func readTrimFile(path, fallback string) string {
	b, err := os.ReadFile(path)
	if err != nil {
		return fallback
	}
	if s := strings.TrimSpace(string(b)); s != "" {
		return s
	}
	return fallback
}

// --- memory (free口径) -------------------------------------------------------

func parseMeminfo(text string) map[string]uint64 {
	out := make(map[string]uint64)
	for _, line := range strings.Split(text, "\n") {
		key, rest, ok := strings.Cut(line, ":")
		if !ok {
			continue
		}
		f := strings.Fields(rest)
		if len(f) == 0 {
			continue
		}
		kb, err := strconv.ParseUint(f[0], 10, 64)
		if err != nil {
			continue
		}
		out[key] = kb * 1024
	}
	return out
}

// memUsedFree is free(1)'s used column: total - MemAvailable, with the
// source's two fallbacks (no MemAvailable -> Free+Buffers+Cached; an
// available above the total, as LXCFS can report, -> total - MemFree).
func memUsedFree(m map[string]uint64) (total, used uint64) {
	total = m["MemTotal"]
	if total == 0 {
		return 0, 0
	}
	avail, ok := m["MemAvailable"]
	if !ok {
		avail = m["MemFree"] + m["Buffers"] + m["Cached"]
	}
	if avail > total {
		avail = m["MemFree"]
	}
	if avail > total {
		avail = total
	}
	return total, total - avail
}

func swapUsedFree(m map[string]uint64) (total, used uint64) {
	total = m["SwapTotal"]
	free := m["SwapFree"]
	if free > total {
		free = total
	}
	return total, total - free
}

// --- cpu --------------------------------------------------------------------

func parseCPUJiffies(stat string) *cpuSample {
	for _, line := range strings.Split(stat, "\n") {
		if !strings.HasPrefix(line, "cpu ") {
			continue
		}
		f := strings.Fields(line[4:])
		if len(f) < 5 {
			return nil
		}
		var v [8]uint64
		var total uint64
		for i := 0; i < len(f) && i < 8; i++ {
			n, err := strconv.ParseUint(f[i], 10, 64)
			if err != nil {
				return nil
			}
			v[i] = n
			total += n
		}
		return &cpuSample{total: total, idle: v[3] + v[4]}
	}
	return nil
}

func parseLoadavg(text string) [3]float32 {
	var out [3]float32
	f := strings.Fields(text)
	for i := 0; i < 3 && i < len(f); i++ {
		if v, err := strconv.ParseFloat(f[i], 32); err == nil {
			out[i] = float32(v)
		}
	}
	return out
}

func parseUptime(text string) uint64 {
	f := strings.Fields(text)
	if len(f) == 0 {
		return 0
	}
	v, err := strconv.ParseFloat(f[0], 64)
	if err != nil || v < 0 {
		return 0
	}
	return uint64(v)
}

// cpuInfo returns the display name and logical core count from /proc/cpuinfo.
func cpuInfo(text string) (string, uint32) {
	name := ""
	cores := uint32(0)
	for _, line := range strings.Split(text, "\n") {
		key, val, ok := strings.Cut(line, ":")
		if !ok {
			continue
		}
		switch strings.TrimSpace(key) {
		case "processor":
			cores++
		case "model name", "Model", "cpu model":
			if name == "" {
				name = strings.TrimSpace(val)
			}
		}
	}
	if cores == 0 {
		cores = uint32(runtime.NumCPU())
		if cores == 0 {
			cores = 1
		}
	}
	if name == "" {
		name = armCPUName(text)
	}
	if name == "" {
		name = "unknown"
	}
	return name, cores
}

// armCPUName decodes AArch64 MIDR implementer/part pairs the way lscpu does,
// joining distinct core types with "/" (e.g. Cortex-A55/Cortex-A76).
func armCPUName(text string) string {
	var vendor *armVendor
	var names []string
	seen := map[string]bool{}
	for _, line := range strings.Split(text, "\n") {
		key, val, ok := strings.Cut(line, ":")
		if !ok {
			continue
		}
		switch strings.TrimSpace(key) {
		case "CPU implementer":
			vendor = nil
			if id, ok := parseHexID(val); ok {
				for i := range armVendors {
					if armVendors[i].id == id {
						vendor = &armVendors[i]
					}
				}
			}
		case "CPU part":
			if vendor == nil {
				continue
			}
			name := vendor.name
			if id, ok := parseHexID(val); ok {
				for _, p := range vendor.parts {
					if p.id == id {
						name = p.name
					}
				}
			}
			if !seen[name] {
				seen[name] = true
				names = append(names, name)
			}
		}
	}
	return strings.Join(names, "/")
}

func parseHexID(s string) (uint32, bool) {
	s = strings.TrimSpace(strings.TrimPrefix(strings.TrimSpace(s), "0x"))
	v, err := strconv.ParseUint(s, 16, 32)
	if err != nil {
		return 0, false
	}
	return uint32(v), true
}

type armPart struct {
	id   uint32
	name string
}
type armVendor struct {
	id    uint32
	name  string
	parts []armPart
}

// Subset of the source's MIDR table (util-linux lscpu-arm names): the parts
// plausibly met on VPS hardware. An unlisted part falls back to the vendor.
var armVendors = []armVendor{
	{0x41, "ARM", []armPart{
		{0xd03, "Cortex-A53"}, {0xd04, "Cortex-A35"}, {0xd05, "Cortex-A55"},
		{0xd07, "Cortex-A57"}, {0xd08, "Cortex-A72"}, {0xd09, "Cortex-A73"},
		{0xd0a, "Cortex-A75"}, {0xd0b, "Cortex-A76"}, {0xd0c, "Neoverse-N1"},
		{0xd0d, "Cortex-A77"}, {0xd40, "Neoverse-V1"}, {0xd41, "Cortex-A78"},
		{0xd44, "Cortex-X1"}, {0xd46, "Cortex-A510"}, {0xd47, "Cortex-A710"},
		{0xd48, "Cortex-X2"}, {0xd49, "Neoverse-N2"}, {0xd4d, "Cortex-A715"},
		{0xd4e, "Cortex-X3"}, {0xd4f, "Neoverse-V2"}, {0xd80, "Cortex-A520"},
		{0xd81, "Cortex-A720"}, {0xd82, "Cortex-X4"}, {0xd84, "Neoverse-V3"},
		{0xd85, "Cortex-X925"}, {0xd87, "Cortex-A725"}, {0xd8e, "Neoverse-N3"},
	}},
	{0x48, "HiSilicon", []armPart{
		{0xd01, "Kunpeng-920"}, {0xd02, "Kunpeng-920"}, {0xd03, "Kunpeng-920"},
		{0xd06, "Kunpeng-950"}, {0xd22, "Kunpeng-920"},
	}},
	{0x51, "Qualcomm", []armPart{{0x001, "Oryon"}, {0x002, "Oryon-2"}}},
	{0x50, "APM", []armPart{{0x000, "X-Gene"}}},
	{0xc0, "Ampere", []armPart{{0xac3, "Ampere-1"}, {0xac4, "Ampere-1a"}}},
	{0x6d, "Microsoft", []armPart{{0xd49, "Azure-Cobalt-100"}}},
}

// --- os / virt ---------------------------------------------------------------

func osPrettyName() string {
	for _, path := range []string{"/etc/os-release", "/usr/lib/os-release"} {
		b, err := os.ReadFile(path)
		if err != nil {
			continue
		}
		for _, line := range strings.Split(string(b), "\n") {
			if v, ok := strings.CutPrefix(line, "PRETTY_NAME="); ok {
				return strings.Trim(v, "\"'")
			}
		}
	}
	return "Linux"
}

// detectVirt ports the source's chain: containers first, then hypervisor.
// CPUID is unreachable from Go's stdlib, so the x86 signature check is
// replaced by the DMI strings (the source's own non-x86 fallback) plus the
// /proc/cpuinfo hypervisor flag — a guest of a hypervisor that hides both
// reads as "none", same caveat the source documents for cleared CPUID bits.
func detectVirt(mounts, cpuinfo string) string {
	if _, err := os.Stat("/proc/vz"); err == nil {
		if _, err := os.Stat("/proc/bc"); err != nil {
			return "openvz"
		}
	}
	if s := readTrimFile("/run/systemd/container", ""); s != "" {
		return s
	}
	if _, err := os.Stat("/.dockerenv"); err == nil {
		return "docker"
	}
	if _, err := os.Stat("/run/.containerenv"); err == nil {
		return "podman"
	}
	for _, line := range strings.Split(mounts, "\n") {
		f := strings.Fields(line)
		if len(f) >= 3 && f[2] == "fuse.lxcfs" && strings.HasPrefix(f[1], "/proc/") {
			return "lxc"
		}
	}
	if _, err := os.Stat("/proc/xen"); err == nil {
		return "xen"
	}
	if _, err := os.Stat("/sys/hypervisor/type"); err == nil {
		return "xen"
	}
	dmi := strings.ToLower(readTrimFile("/sys/class/dmi/id/product_name", "") + " " +
		readTrimFile("/sys/class/dmi/id/sys_vendor", ""))
	for _, m := range []struct{ word, name string }{
		{"kvm", "kvm"}, {"qemu", "kvm"}, {"amazon ec2", "kvm"}, {"google", "kvm"},
		{"microsoft", "hyper-v"}, {"vmware", "vmware"}, {"virtualbox", "virtualbox"},
		{"bhyve", "bhyve"}, {"xen", "xen"},
	} {
		if strings.Contains(dmi, m.word) {
			return m.name
		}
	}
	if _, err := os.Stat("/sys/bus/acpi/devices/QEMU0002:00"); err == nil {
		return "kvm"
	}
	if strings.Contains(cpuinfo, "hypervisor") {
		return "vm"
	}
	return "none"
}

// --- network: counted set, epoch, rates -------------------------------------

func parseNetDev(text string) []netCounters {
	var out []netCounters
	lines := strings.Split(text, "\n")
	for _, line := range lines {
		name, rest, ok := strings.Cut(line, ":")
		if !ok {
			continue
		}
		f := strings.Fields(rest)
		if len(f) < 16 {
			continue
		}
		rx, err1 := strconv.ParseUint(f[0], 10, 64)
		tx, err2 := strconv.ParseUint(f[8], 10, 64)
		if err1 != nil || err2 != nil {
			continue
		}
		out = append(out, netCounters{name: strings.TrimSpace(name), rx: rx, tx: tx})
	}
	return out
}

// skipIfacePrefixes is layer 1 of the filter (source SKIP_IFACES).
var skipIfacePrefixes = []string{
	"lo", "docker", "veth", "br-", "virbr", "tap", "tun", "wg", "tailscale",
	"cni", "flannel", "podman", "fwbr", "fwpr", "fwln", "ifb", "gretap",
	"erspan", "kube", "cali", "nerdctl", "lxc", "cilium", "zt",
}

func skipIfaceName(name string) bool {
	for _, p := range skipIfacePrefixes {
		if strings.HasPrefix(name, p) {
			return true
		}
	}
	return false
}

// isStackedName is layer 2: bonds, bridges, VLAN children, PPPoE overlays —
// the kernel books their bytes again on the device beneath.
func isStackedName(name string) bool {
	if strings.Contains(name, ".") {
		return true
	}
	for _, p := range []string{"bond", "br", "vlan", "vmbr", "pppoe-"} {
		if strings.HasPrefix(name, p) {
			return true
		}
	}
	return false
}

var tunnelLinkTypes = map[string]bool{
	"65534": true, "768": true, "769": true, "776": true, "778": true, "823": true,
}

// countedElsewhere is layer 3 (sysfs): the kernel shows this device's bytes
// are already counted on another device. Hardware (a `device` link) exempts
// a device from the tunnel/port rules — a raw-IP LTE modem shares its link
// type with WireGuard but carries real traffic.
func countedElsewhere(sysRoot, name string) bool {
	dev := filepath.Join(sysRoot, name)
	uevent := readTrimFile(filepath.Join(dev, "uevent"), "")
	devtypeIs := func(set ...string) bool {
		for _, line := range strings.Split(uevent, "\n") {
			for _, want := range set {
				if line == want {
					return true
				}
			}
		}
		return false
	}
	if devtypeIs("DEVTYPE=bridge", "DEVTYPE=bond") {
		return true
	}
	if entries, err := os.ReadDir(dev); err == nil {
		for _, e := range entries {
			if strings.HasPrefix(e.Name(), "lower_") {
				return true
			}
		}
	}
	if _, err := os.Stat(filepath.Join(dev, "device")); err == nil {
		return false
	}
	if _, err := os.Stat(filepath.Join(dev, "brport")); err == nil {
		return true
	}
	if tunnelLinkTypes[readTrimFile(filepath.Join(dev, "type"), "")] {
		return true
	}
	return devtypeIs("DEVTYPE=vxlan", "DEVTYPE=geneve")
}

// ifaceCounts applies the three layers. Exposed for tests with a fake sysfs.
func ifaceCounts(sysRoot, name string) bool {
	if skipIfaceName(name) || isStackedName(name) {
		return false
	}
	return !countedElsewhere(sysRoot, name)
}

func countedInterfaces(all []netCounters, sysRoot string) []netCounters {
	out := make([]netCounters, 0, len(all))
	for _, c := range all {
		if ifaceCounts(sysRoot, c.name) {
			out = append(out, c)
		}
	}
	return out
}

// --- addresses (scope §1.5) ---------------------------------------------------

// probeAddresses picks one address per family: candidates come from
// non-skip interfaces that are up, are not link-local, prefer public over
// private, and for v6 avoid temporary/deprecated/tentative addresses.
func probeAddresses() (string, string) {
	transient := transientV6(readProcFile("net/if_inet6"))
	ifaces, err := net.Interfaces()
	if err != nil {
		return "", ""
	}
	type cand struct {
		ip        net.IP
		transient bool
	}
	var held []cand
	for _, ifc := range ifaces {
		if ifc.Flags&net.FlagUp == 0 {
			continue
		}
		if readTrimFile(filepath.Join(sysNetRoot, ifc.Name, "operstate"), "up") != "up" {
			continue
		}
		addrs, err := ifc.Addrs()
		if err != nil {
			continue
		}
		for _, addr := range addrs {
			var ip net.IP
			switch v := addr.(type) {
			case *net.IPNet:
				ip = v.IP
			case *net.IPAddr:
				ip = v.IP
			}
			if ip == nil || ip.IsLinkLocalUnicast() || ip.IsLinkLocalMulticast() {
				continue
			}
			if !lendsAddress(ifc.Name, ip) {
				continue
			}
			c := cand{ip: ip}
			if ip6 := ip.To16(); ip.To4() == nil && ip6 != nil {
				for _, t := range transient {
					if t.Equal(ip6) {
						c.transient = true
					}
				}
			}
			held = append(held, c)
		}
	}
	pick := func(v6 bool) string {
		var best *cand
		for i := range held {
			c := &held[i]
			if (c.ip.To4() == nil) != v6 {
				continue
			}
			if best == nil {
				best = c
				continue
			}
			bp, cp := isPublicIP(best.ip), isPublicIP(c.ip)
			if cp != bp {
				if cp {
					best = c
				}
				continue
			}
			if v6 && best.transient && !c.transient {
				best = c
			}
		}
		if best == nil {
			return ""
		}
		return best.ip.String()
	}
	return pick(false), pick(true)
}

// lendsAddress mirrors the source: a skipped interface lends no address,
// except a WireGuard interface lending a public v6 that is not in
// Cloudflare WARP's shared 2606:4700::/32.
func lendsAddress(name string, ip net.IP) bool {
	if !skipIfaceName(name) {
		return true
	}
	if strings.HasPrefix(name, "wg") && ip.To4() == nil && isPublicIP(ip) {
		ip16 := ip.To16()
		return !(ip16[0] == 0x26 && ip16[1] == 0x06 && ip16[2] == 0x47 && ip16[3] == 0x00)
	}
	return false
}

// transientV6 parses /proc/net/if_inet6 for addresses carrying
// TEMPORARY|DADFAILED|DEPRECATED|TENTATIVE flags.
func transientV6(text string) []net.IP {
	const transientFlags = 0x01 | 0x08 | 0x20 | 0x40
	var out []net.IP
	for _, line := range strings.Split(text, "\n") {
		f := strings.Fields(line)
		if len(f) < 6 {
			continue
		}
		flags, err := strconv.ParseUint(f[4], 16, 32)
		if err != nil || flags&transientFlags == 0 {
			continue
		}
		if len(f[0]) != 32 {
			continue
		}
		ip := make(net.IP, 16)
		ok := true
		for i := 0; i < 16; i++ {
			b, err := strconv.ParseUint(f[0][i*2:i*2+2], 16, 8)
			if err != nil {
				ok = false
				break
			}
			ip[i] = byte(b)
		}
		if ok {
			out = append(out, ip)
		}
	}
	return out
}

// --- sockets / processes ------------------------------------------------------

func connCounts(v4, v6 string) (tcp, udp uint32) {
	stat := func(text, prefix, key string) uint32 {
		for _, line := range strings.Split(text, "\n") {
			if !strings.HasPrefix(line, prefix) {
				continue
			}
			f := strings.Fields(line[len(prefix):])
			for i := 0; i+1 < len(f); i++ {
				if f[i] == key {
					if n, err := strconv.ParseUint(f[i+1], 10, 32); err == nil {
						return uint32(n)
					}
					return 0
				}
			}
		}
		return 0
	}
	tcp = stat(v4, "TCP:", "inuse") + stat(v4, "TCP:", "tw") + stat(v6, "TCP6:", "inuse")
	udp = stat(v4, "UDP:", "inuse") + stat(v6, "UDP6:", "inuse")
	return tcp, udp
}

func procCount() uint32 {
	entries, err := os.ReadDir("/proc")
	if err != nil {
		return 0
	}
	var n uint32
	for _, e := range entries {
		name := e.Name()
		digits := name != ""
		for i := 0; i < len(name); i++ {
			if name[i] < '0' || name[i] > '9' {
				digits = false
				break
			}
		}
		if digits {
			n++
		}
	}
	return n
}

// --- disk (df口径) ---------------------------------------------------------------

var skipFSTypes = map[string]bool{
	"tmpfs": true, "devtmpfs": true, "proc": true, "sysfs": true,
	"cgroup": true, "cgroup2": true, "devpts": true, "mqueue": true,
	"hugetlbfs": true, "debugfs": true, "tracefs": true, "securityfs": true,
	"pstore": true, "bpf": true, "configfs": true, "fusectl": true,
	"binfmt_misc": true, "autofs": true, "squashfs": true, "ramfs": true,
	"efivarfs": true, "nsfs": true, "overlay": true, "ecryptfs": true,
	"fuse": true, "rpc_pipefs": true,
	"nfs": true, "nfs4": true, "cifs": true, "smb3": true, "ceph": true,
	"glusterfs": true, "9p": true,
}

func skipFSType(fstype string) bool {
	if skipFSTypes[fstype] {
		return true
	}
	// Flavours: "fuse.lxcfs" is skipped by its "fuse." prefix, like the source.
	if i := strings.IndexByte(fstype, '.'); i > 0 && skipFSTypes[fstype[:i]] {
		return true
	}
	return false
}

// realMountPoints ports parse_mounts: only the topmost mount per path,
// deduped by source device (zfs by pool), real storage only.
func realMountPoints(text string) []string {
	type row struct{ dev, mount, fstype string }
	var rows []row
	top := map[string]int{}
	for _, line := range strings.Split(text, "\n") {
		f := strings.Fields(line)
		if len(f) < 3 {
			continue
		}
		rows = append(rows, row{f[0], f[1], f[2]})
		top[f[1]] = len(rows) - 1
	}
	seen := map[string]bool{}
	var out []string
	for i, r := range rows {
		if top[r.mount] != i || skipFSType(r.fstype) {
			continue
		}
		if !strings.HasPrefix(r.dev, "/") && r.fstype != "zfs" && r.fstype != "btrfs" {
			continue
		}
		key := r.dev
		if r.fstype == "zfs" {
			if j := strings.IndexByte(key, '/'); j >= 0 {
				key = key[:j]
			}
		}
		if seen[key] {
			continue
		}
		seen[key] = true
		out = append(out, strings.ReplaceAll(r.mount, `\040`, " "))
	}
	return out
}

// diskUsage sums statfs over the mounts: total = f_blocks, used =
// f_blocks - f_bfree (NOT f_bavail — df does not charge the ext reserve).
func diskUsage(mounts []string) (total, used uint64) {
	for _, m := range mounts {
		var st syscall.Statfs_t
		if err := syscall.Statfs(m, &st); err != nil {
			continue
		}
		bs := uint64(st.Frsize)
		if bs == 0 {
			bs = uint64(st.Bsize)
		}
		total += st.Blocks * bs
		if st.Blocks > st.Bfree {
			used += (st.Blocks - st.Bfree) * bs
		}
	}
	return total, used
}