package tools

import (
	"bufio"
	"context"
	"encoding/json"
	"fmt"
	"net"
	"os"
	"os/exec"
	"runtime"
	"strings"
)

// systemInfoTool reúne datos básicos del sistema (§46, §49, §50, §51) leyendo
// directamente /proc, /etc/os-release y el PATH: no ejecuta comandos, así
// que es seguro en cualquier modo de ejecución.
type systemInfoTool struct{}

func (systemInfoTool) Name() string { return "system_info" }
func (systemInfoTool) Description() string {
	return "Report OS, kernel, architecture, hostname, CPU, memory, uptime, privileges (uid/euid, sudo/doas), init system, package managers, mounted filesystems and network interfaces. Read-only."
}
func (systemInfoTool) Schema() map[string]any { return obj(nil, map[string]any{}) }

func (systemInfoTool) Run(_ context.Context, _ *Env, raw json.RawMessage) Result {
	var none struct{}
	if err := decode(raw, &none); err != nil {
		return fail("system_info", err)
	}
	return Result{OK: true, ExitCode: 0, Summary: "system_info", Output: CollectSystemInfo()}
}

// CollectSystemInfo produce un informe textual. Los datos que no se pueden
// leer aparecen como UNKNOWN en lugar de suponerse.
func CollectSystemInfo() string {
	var b strings.Builder
	kv := func(k, v string) {
		if v == "" {
			v = "UNKNOWN"
		}
		fmt.Fprintf(&b, "%s: %s\n", k, v)
	}

	osr := readKeyValues("/etc/os-release")
	kv("os", osr["PRETTY_NAME"])
	kv("os_id", strings.TrimSpace(osr["ID"]+" "+osr["ID_LIKE"]))
	kv("os_version", osr["VERSION_ID"])
	kv("kernel", readTrim("/proc/sys/kernel/osrelease"))
	kv("architecture", runtime.GOARCH)
	h, _ := os.Hostname()
	kv("hostname", h)

	cpuModel, cpus := "", 0
	if f, err := os.Open("/proc/cpuinfo"); err == nil {
		sc := bufio.NewScanner(f)
		for sc.Scan() {
			line := sc.Text()
			if strings.HasPrefix(line, "processor") {
				cpus++
			}
			if cpuModel == "" && (strings.HasPrefix(line, "model name") || strings.HasPrefix(line, "Model")) {
				if _, v, ok := strings.Cut(line, ":"); ok {
					cpuModel = strings.TrimSpace(v)
				}
			}
		}
		f.Close()
	}
	kv("cpu_model", cpuModel)
	kv("cpu_count", fmt.Sprint(max(cpus, runtime.NumCPU())))

	mem := readKeyValuesSep("/proc/meminfo", ":")
	kv("mem_total", mem["MemTotal"])
	kv("mem_available", mem["MemAvailable"])
	kv("swap_total", mem["SwapTotal"])
	if up := strings.Fields(readTrim("/proc/uptime")); len(up) > 0 {
		kv("uptime_seconds", up[0])
	}

	kv("uid", fmt.Sprint(os.Getuid()))
	kv("euid", fmt.Sprint(os.Geteuid()))
	kv("running_as_root", fmt.Sprint(os.Geteuid() == 0))
	kv("escalation_tools", strings.Join(available("sudo", "doas", "su"), " "))

	initSys := "UNKNOWN"
	if st, err := os.Stat("/run/systemd/system"); err == nil && st.IsDir() {
		initSys = "systemd"
	} else if comm := readTrim("/proc/1/comm"); comm != "" {
		initSys = comm
	}
	kv("init_system", initSys)
	kv("package_managers", strings.Join(available("apt", "apt-get", "dpkg", "dnf", "yum", "rpm", "pacman", "zypper", "apk", "snap", "flatpak"), " "))

	b.WriteString("filesystems:\n")
	if f, err := os.Open("/proc/mounts"); err == nil {
		sc := bufio.NewScanner(f)
		for sc.Scan() {
			p := strings.Fields(sc.Text())
			if len(p) < 3 || isPseudoFS(p[2]) {
				continue
			}
			fmt.Fprintf(&b, "  %s on %s type %s\n", p[0], p[1], p[2])
		}
		f.Close()
	}

	b.WriteString("network_interfaces:\n")
	if ifs, err := net.Interfaces(); err == nil {
		for _, it := range ifs {
			addrs, _ := it.Addrs()
			var as []string
			for _, a := range addrs {
				as = append(as, a.String())
			}
			fmt.Fprintf(&b, "  %s flags=%s mac=%s addrs=%s\n", it.Name, it.Flags, it.HardwareAddr, strings.Join(as, ","))
		}
	}
	return b.String()
}

// execLookPath existe para que find_program y available compartan criterio.
func execLookPath(name string) (string, error) { return exec.LookPath(name) }

func available(names ...string) []string {
	var out []string
	for _, n := range names {
		if _, err := exec.LookPath(n); err == nil {
			out = append(out, n)
		}
	}
	return out
}

func isPseudoFS(t string) bool {
	switch t {
	case "proc", "sysfs", "devtmpfs", "devpts", "tmpfs", "cgroup", "cgroup2", "securityfs", "pstore", "bpf",
		"debugfs", "tracefs", "mqueue", "hugetlbfs", "configfs", "fusectl", "autofs", "binfmt_misc", "efivarfs",
		"rpc_pipefs", "nsfs", "ramfs", "selinuxfs":
		return true
	}
	return false
}

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

func readKeyValues(path string) map[string]string {
	m := map[string]string{}
	f, err := os.Open(path)
	if err != nil {
		return m
	}
	defer f.Close()
	sc := bufio.NewScanner(f)
	for sc.Scan() {
		if k, v, ok := strings.Cut(sc.Text(), "="); ok {
			m[k] = strings.Trim(v, `"`)
		}
	}
	return m
}

func readKeyValuesSep(path, sep string) map[string]string {
	m := map[string]string{}
	f, err := os.Open(path)
	if err != nil {
		return m
	}
	defer f.Close()
	sc := bufio.NewScanner(f)
	for sc.Scan() {
		if k, v, ok := strings.Cut(sc.Text(), sep); ok {
			m[strings.TrimSpace(k)] = strings.TrimSpace(v)
		}
	}
	return m
}