package agent

import (
	"context"
	"math"
	"net"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"time"

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

	"github.com/shirou/gopsutil/v4/cpu"
	"github.com/shirou/gopsutil/v4/host"
	"github.com/shirou/gopsutil/v4/mem"
)

// telemetryPayload is the best-effort host/runtime snapshot piggybacked on
// every heartbeat (P13). Pointer fields are omitted when their collector
// failed, so the master keeps the last stored value instead of a zero.
type telemetryPayload struct {
	AgentVersion  string   `json:"agentVersion"`
	XrayVersion   string   `json:"xrayVersion,omitempty"`
	UptimeSeconds *uint64  `json:"uptimeSeconds,omitempty"`
	LatencyMs     *int64   `json:"latencyMs,omitempty"`
	CpuPercent    *float64 `json:"cpuPercent,omitempty"`
	MemPercent    *float64 `json:"memPercent,omitempty"`
	IPv4          string   `json:"ipv4,omitempty"`
	IPv6          string   `json:"ipv6,omitempty"`
}

// collectTelemetry samples every source independently; a failing source
// only blanks its own field, never the whole report.
func (a *Agent) collectTelemetry() *telemetryPayload {
	t := &telemetryPayload{AgentVersion: config.GetBaseVersion()}
	if v, ok := a.cachedXrayVersion(); ok {
		t.XrayVersion = v
	}
	if up, err := host.Uptime(); err == nil {
		t.UptimeSeconds = &up
	}
	if pcts, err := cpu.Percent(0, false); err == nil && len(pcts) > 0 {
		v := math.Round(pcts[0]*10) / 10
		t.CpuPercent = &v
	}
	if vm, err := mem.VirtualMemory(); err == nil {
		v := math.Round(vm.UsedPercent*10) / 10
		t.MemPercent = &v
	}
	if a.hasRTT.Load() {
		v := a.lastRTTms.Load()
		t.LatencyMs = &v
	}
	t.IPv4, t.IPv6 = hostPublicIPs()
	return t
}

// cachedXrayVersion returns the managed xray binary's version, re-reading
// it only when the binary file changed (path or mtime) since the last read,
// so a swapped xray is picked up without restarting the agent.
func (a *Agent) cachedXrayVersion() (string, bool) {
	path := xrayBinaryPath()
	if path == "" {
		return "", false
	}
	fi, err := os.Stat(path)
	if err != nil {
		return "", false
	}
	a.xrayVerMu.Lock()
	defer a.xrayVerMu.Unlock()
	if a.xrayVer != "" && a.xrayVerFor == path && fi.ModTime().Equal(a.xrayVerMod) {
		return a.xrayVer, true
	}
	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
	defer cancel()
	out, err := exec.CommandContext(ctx, path, "version").Output()
	if err != nil {
		return "", false
	}
	v, ok := parseXrayVersion(string(out))
	if !ok {
		return "", false
	}
	a.xrayVer, a.xrayVerFor, a.xrayVerMod = v, path, fi.ModTime()
	return v, true
}

// xrayBinaryPath resolves the managed xray binary: the arch-specific name
// the process manager uses, falling back to a plain "xray" in the same bin
// folder (mirrors ensureXrayBinary).
func xrayBinaryPath() string {
	if p := xray.GetBinaryPath(); fileExists(p) {
		return p
	}
	if p := filepath.Join(config.GetBinFolderPath(), "xray"); fileExists(p) {
		return p
	}
	return ""
}

func fileExists(p string) bool {
	fi, err := os.Stat(p)
	return err == nil && !fi.IsDir()
}

// parseXrayVersion extracts the version from the first line of
// `xray version` output, e.g. "Xray 26.6.27 (Xray, Penetrates Everything.)".
func parseXrayVersion(out string) (string, bool) {
	line := out
	if i := strings.IndexByte(line, '\n'); i >= 0 {
		line = line[:i]
	}
	fields := strings.Fields(line)
	if len(fields) < 2 || !strings.EqualFold(fields[0], "xray") {
		return "", false
	}
	v := fields[1]
	if v == "" || v[0] < '0' || v[0] > '9' {
		return "", false
	}
	return v, true
}

// hostPublicIPs picks one IPv4 and one IPv6 address from the host's active
// interfaces. Loopback, link-local, multicast and down interfaces are
// excluded; globally routable addresses win over private/ULA ones, which
// are only used when no public address exists.
func hostPublicIPs() (string, string) {
	ifaces, err := net.Interfaces()
	if err != nil {
		return "", ""
	}
	var ips []net.IP
	for _, ifc := range ifaces {
		if ifc.Flags&net.FlagUp == 0 || ifc.Flags&net.FlagLoopback != 0 {
			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 {
				ips = append(ips, ip)
			}
		}
	}
	return chooseHostIPs(ips)
}

// chooseHostIPs applies the public-over-private preference to a candidate
// address list. Kept pure for testing.
func chooseHostIPs(ips []net.IP) (string, string) {
	var v4Pub, v4Priv, v6Pub, v6Priv net.IP
	for _, ip := range ips {
		if ip == nil || ip.IsLoopback() || ip.IsUnspecified() ||
			ip.IsLinkLocalUnicast() || ip.IsLinkLocalMulticast() || ip.IsMulticast() {
			continue
		}
		if ip4 := ip.To4(); ip4 != nil {
			if ip4.IsPrivate() {
				if v4Priv == nil {
					v4Priv = ip4
				}
			} else if v4Pub == nil {
				v4Pub = ip4
			}
			continue
		}
		ip6 := ip.To16()
		if ip6 == nil {
			continue
		}
		if ip6.IsPrivate() { // unique-local fc00::/7
			if v6Priv == nil {
				v6Priv = ip6
			}
		} else if v6Pub == nil {
			v6Pub = ip6
		}
	}
	pick := func(pub, priv net.IP) string {
		if pub != nil {
			return pub.String()
		}
		if priv != nil {
			return priv.String()
		}
		return ""
	}
	return pick(v4Pub, v4Priv), pick(v6Pub, v6Priv)
}