package originclient

import (
	"net"
	"os"
	"strings"
)

// Hostname returns the OS hostname, or "" if it cannot be determined.
func Hostname() string {
	h, err := os.Hostname()
	if err != nil {
		return ""
	}
	return h
}

// OutboundIP returns the first non-loopback IPv4 address bound to this
// host. It is a LAN-facing address, not the host's public internet
// address, and is not part of Origin's wire contract — it exists so
// callers can populate BaseURL/InternalURL/Description themselves.
func OutboundIP() string {
	addrs, err := net.InterfaceAddrs()
	if err != nil {
		return ""
	}
	for _, addr := range addrs {
		ipNet, ok := addr.(*net.IPNet)
		if !ok || ipNet.IP.IsLoopback() {
			continue
		}
		if ip4 := ipNet.IP.To4(); ip4 != nil {
			return ip4.String()
		}
	}
	return ""
}

// ContainerID best-effort detects the Docker/Kubernetes container ID this
// process runs in. It returns "" outside a container or when detection
// fails; an empty container ID is treated as "not containerized" rather
// than an error.
func ContainerID() string {
	if data, err := os.ReadFile("/proc/self/cgroup"); err == nil {
		if id := parseCgroupContainerID(data); id != "" {
			return id
		}
	}
	if _, err := os.Stat("/.dockerenv"); err == nil {
		if h := Hostname(); isContainerIDLike(h) {
			return h
		}
	}
	return ""
}

// Orchestrator best-effort detects the orchestration environment:
// "kubernetes" under Kubernetes, "docker" in a plain Docker container, ""
// otherwise.
func Orchestrator() string {
	if os.Getenv("KUBERNETES_SERVICE_HOST") != "" {
		return "kubernetes"
	}
	if _, err := os.Stat("/.dockerenv"); err == nil {
		return "docker"
	}
	return ""
}

// parseCgroupContainerID extracts a container ID from /proc/self/cgroup
// content, handling both cgroup v1 (".../docker/<id>") and cgroup v2
// systemd-scope (".../docker-<id>.scope") layouts.
func parseCgroupContainerID(data []byte) string {
	for _, line := range strings.Split(string(data), "\n") {
		line = strings.TrimSpace(line)
		idx := strings.LastIndex(line, "/")
		if idx == -1 {
			continue
		}
		segment := line[idx+1:]
		segment = strings.TrimSuffix(segment, ".scope")
		segment = strings.TrimPrefix(segment, "docker-")
		if isContainerIDLike(segment) {
			return segment
		}
	}
	return ""
}

func isContainerIDLike(s string) bool {
	if len(s) < 12 || len(s) > 64 {
		return false
	}
	for _, r := range s {
		if (r < '0' || r > '9') && (r < 'a' || r > 'f') {
			return false
		}
	}
	return true
}