package main

import (
	"context"
	"encoding/json"
	"strings"
	"time"
)

// CountConnections reads the bus driver's Debug.Stats answer (`busctl call … GetStats --json=short`):
// dbus-broker lists one accounting entry per peer, the reference daemon says ActiveConnections.
func CountConnections(out string) (int, bool) {
	var reply struct {
		Data []map[string]struct {
			Data json.RawMessage `json:"data"`
		} `json:"data"`
	}
	if json.Unmarshal([]byte(strings.TrimSpace(out)), &reply) != nil || len(reply.Data) != 1 {
		return 0, false
	}
	if v, ok := reply.Data[0]["org.bus1.DBus.Debug.Stats.PeerAccounting"]; ok {
		var peers []json.RawMessage
		if json.Unmarshal(v.Data, &peers) == nil {
			return len(peers), true
		}
	}
	if v, ok := reply.Data[0]["ActiveConnections"]; ok {
		var n int
		if json.Unmarshal(v.Data, &n) == nil {
			return n, true
		}
	}
	return 0, false
}

// CountUniqueNames counts the connections among ListNames' answer (`busctl call … ListNames`).
func CountUniqueNames(out string) (int, bool) {
	var reply struct {
		Data [][]string `json:"data"`
	}
	if json.Unmarshal([]byte(strings.TrimSpace(out)), &reply) != nil || len(reply.Data) != 1 {
		return 0, false
	}
	n := 0
	for _, name := range reply.Data[0] {
		if strings.HasPrefix(name, ":") {
			n++
		}
	}
	return n, true
}

// Health is the system bus's health now: a ping through the watcher's connection, how many
// connections the bus has, and how long it has run.
func (m *Machine) Health(ctx context.Context, w *Watcher) map[string]any {
	h := map[string]any{"bus": "system"}
	if w != nil {
		took, err := w.PingNow()
		if err != nil {
			h["ping"] = "no answer: " + err.Error()
		} else {
			h["ping_ms"] = float64(took.Microseconds()) / 1000
		}
		h["watcher"] = w.Snapshot()
	}
	// Debug.Stats is root's on the system bus; asked as the account it is refused and logged as a
	// denial, which the watcher would then publish. So it is asked through sudo -n or not at all.
	call := []string{"busctl", "--system", "--json=short", "--no-pager", "call", busName, busPath}
	if out, err := m.privileged(ctx, call[0], append(call[1:], busName+".Debug.Stats", "GetStats")...); err == nil {
		if n, ok := CountConnections(out); ok {
			h["connections"], h["connections_from"] = n, "the bus's Debug.Stats"
		}
	}
	if _, ok := h["connections"]; !ok {
		if out, err := m.Run(ctx, call[0], append(call[1:], busName, "ListNames")...); err == nil {
			if n, ok := CountUniqueNames(out); ok {
				h["connections"], h["connections_from"] = n, "the unique names on the bus (Debug.Stats needs sudo -n)"
			}
		}
	}
	if u, err := m.SystemBusUnit(ctx); err != nil {
		h["unit"] = err.Error()
	} else {
		h["unit"], h["active"], h["pid"] = u.Unit, u.Active, u.PID
		if !u.Since.IsZero() {
			h["started"] = u.Started
			h["uptime"] = m.Now().Sub(u.Since).Round(time.Second).String()
		}
	}
	return h
}