// Package platform centralizes OS detection, path resolution, signal handling,
// and runtime system information. Other packages must never call syscall or
// hard-code OS paths; they resolve everything through this package.
package platform

import (
	"os"
	"runtime"
	"strconv"
)

// Info describes the host platform.
type Info struct {
	Name    string // human-readable platform name
	GOOS    string
	GOARCH  string
	Kind    string // platform family: desktop / server / mobile / unknown
	CPUs    int
	Host    string
	GoVer   string
}

// Detect returns runtime-derived platform information.
func Detect() Info {
	return Info{
		Name:   platformName(runtime.GOOS),
		GOOS:   runtime.GOOS,
		GOARCH: runtime.GOARCH,
		Kind:   platformKind(runtime.GOOS),
		CPUs:   runtime.NumCPU(),
		Host:   hostname(),
		GoVer:  runtime.Version(),
	}
}

// GOOS returns the operating system name (runtime.GOOS).
func GOOS() string { return runtime.GOOS }

// GOARCH returns the CPU architecture name (runtime.GOARCH).
func GOARCH() string { return runtime.GOARCH }

// CPUs returns the number of logical CPUs visible to the runtime.
func CPUs() int { return runtime.NumCPU() }

// IsWindows reports whether the host is Windows.
func IsWindows() bool { return runtime.GOOS == "windows" }

// IsDarwin reports whether the host is macOS.
func IsDarwin() bool { return runtime.GOOS == "darwin" }

// IsLinux reports whether the host is Linux.
func IsLinux() bool { return runtime.GOOS == "linux" }

// IsUnix reports whether the host is a Unix-like OS (linux, darwin, etc.).
func IsUnix() bool { return runtime.GOOS != "windows" }

// CPUArch converts runtime.GOARCH to a compact architecture label.
func CPUArch() string { return archLabel(runtime.GOARCH) }

// archLabel maps a GOARCH value to a compact human-readable label. Unknown
// values pass through unchanged.
func archLabel(goarch string) string {
	switch goarch {
	case "amd64":
		return "x86_64"
	case "386":
		return "x86"
	default:
		return goarch
	}
}

// Describe renders a short log-ready summary of the runtime.
func (i Info) Describe() string {
	return i.Name + "/" + i.GOOS + "/" + i.GOARCH + " cpu=" + strconv.Itoa(i.CPUs) + " go=" + i.GoVer
}

func platformName(goos string) string {
	switch goos {
	case "windows":
		return "Windows"
	case "darwin":
		return "macOS"
	case "linux":
		return "Linux"
	default:
		return goos
	}
}

func platformKind(goos string) string {
	switch goos {
	case "windows", "darwin":
		return "desktop"
	case "linux":
		return "server"
	default:
		return "unknown"
	}
}

func hostname() string {
	h, err := os.Hostname()
	if err != nil {
		return "unknown"
	}
	return h
}