// Package sysfacts reads the agent's `system` stanza (agent v0.142.0, R-852, `09` decision 89): the box's Proxmox,
// kernel, Debian and Docker versions and its crash guard. One parser for the System page, the Hosts page and the
// crash events. A value the box could not read stays "unknown" — never empty, never guessed. Pinned by sysfacts_test.go.
package sysfacts

import (
	"encoding/json"
	"strings"
)

// Unknown is what a field reads when nobody could read it.
const Unknown = "unknown"

// CrashGuard is the box's felhom-crash-guard state (`11` §5.9).
type CrashGuard struct {
	Armed           bool     `json:"armed"`
	Tripped         bool     `json:"tripped"`
	TrippedAt       string   `json:"tripped_at"`
	TrippedReason   string   `json:"tripped_reason"`
	UncleanBoots    []string `json:"unclean_boots"`
	InWindow        int      `json:"unclean_boots_in_window"`
	In24h           int      `json:"unclean_boots_24h"`
	LastBootAt      string   `json:"last_boot_at"`
	LastBootUnclean bool     `json:"last_boot_unclean"`
	KernelPanic     *int     `json:"kernel_panic"`
	BootID          string   `json:"boot_id"`
	RearmedAt       string   `json:"rearmed_at"`
	RearmedBy       string   `json:"rearmed_by"`
}

// Host is the Proxmox host's half.
type Host struct {
	Debian               string      `json:"debian"`
	KernelRunning        string      `json:"kernel_running"`
	KernelNextBoot       string      `json:"kernel_next_boot"`
	KernelNextBootSource string      `json:"kernel_next_boot_source"`
	Held                 []string    `json:"held"` // nil = unknown
	Tainted              *int        `json:"tainted"`
	OopsThisBoot         *bool       `json:"oops_this_boot"`
	KernelPanic          *int        `json:"kernel_panic"`
	CrashGuard           *CrashGuard `json:"crash_guard"`
}

// Guest is the customer guest's half.
type Guest struct {
	Debian        string `json:"debian"`
	DockerEngine  string `json:"docker_engine"`
	Containerd    string `json:"containerd"`
	LiveRestore   string `json:"live_restore"` // on | off | unknown
	UnknownReason string `json:"unknown_reason"`
}

// ConfigBundle is the box's root-owned config bundle (R-840, agent v0.143.0): the agent's own read of the record
// (version "none" = no bundle ever reached the box), with the drift the wrapper's facts add (files changed by hand).
type ConfigBundle struct {
	Version      string   `json:"version"` // agent version of the bundle | none | unknown
	BundleSHA256 string   `json:"bundle_sha256"`
	InstalledAt  string   `json:"installed_at"`
	Drift        []string `json:"drift"`
}

// System is the whole stanza. Present is false for a report from an agent older than v0.142.0.
type System struct {
	Present       bool
	PVEVersion    string
	KernelVersion string
	VMID          int
	FactsError    string
	ReadAt        string
	Host          Host
	Guest         Guest
	Bundle        ConfigBundle
}

type wire struct {
	System *struct {
		PVEVersion    string          `json:"pve_version"`
		KernelVersion string          `json:"kernel_version"`
		VMID          int             `json:"vmid"`
		Facts         json.RawMessage `json:"facts"`
		FactsError    string          `json:"facts_error"`
		ReadAt        string          `json:"read_at"`
		ConfigBundle  *ConfigBundle   `json:"config_bundle"`
	} `json:"system"`
}

func orUnknown(s string) string {
	if strings.TrimSpace(s) == "" {
		return Unknown
	}
	return s
}

// Parse reads the stanza from a host-report body. Never fails: an absent or broken stanza is Present=false or unknowns.
func Parse(reportJSON string) System {
	out := System{PVEVersion: Unknown, KernelVersion: Unknown,
		Host:  Host{Debian: Unknown, KernelRunning: Unknown, KernelNextBoot: Unknown},
		Guest: Guest{Debian: Unknown, DockerEngine: Unknown, Containerd: Unknown, LiveRestore: Unknown}}
	var w wire
	if json.Unmarshal([]byte(reportJSON), &w) != nil || w.System == nil {
		return out
	}
	out.Present = true
	out.PVEVersion, out.KernelVersion = orUnknown(w.System.PVEVersion), orUnknown(w.System.KernelVersion)
	out.VMID, out.FactsError, out.ReadAt = w.System.VMID, w.System.FactsError, w.System.ReadAt
	var f struct {
		Host struct {
			Host
			ConfigBundle *ConfigBundle `json:"config_bundle"`
		} `json:"host"`
		Guest Guest `json:"guest"`
	}
	out.Bundle = ConfigBundle{Version: Unknown}
	if w.System.ConfigBundle != nil && w.System.ConfigBundle.Version != "" {
		out.Bundle = *w.System.ConfigBundle
	}
	if len(w.System.Facts) > 0 && json.Unmarshal(w.System.Facts, &f) == nil {
		out.Host, out.Guest = f.Host.Host, f.Guest
		// The wrapper's view adds the drift; its record is the same file the agent read.
		if fb := f.Host.ConfigBundle; fb != nil && fb.Version != "" && fb.Version != Unknown {
			if out.Bundle.Version == Unknown {
				out.Bundle = *fb
			}
			out.Bundle.Drift = fb.Drift
		}
	}
	out.Host.Debian, out.Host.KernelRunning = orUnknown(out.Host.Debian), orUnknown(out.Host.KernelRunning)
	out.Host.KernelNextBoot = orUnknown(out.Host.KernelNextBoot)
	out.Guest.Debian, out.Guest.DockerEngine = orUnknown(out.Guest.Debian), orUnknown(out.Guest.DockerEngine)
	out.Guest.Containerd, out.Guest.LiveRestore = orUnknown(out.Guest.Containerd), orUnknown(out.Guest.LiveRestore)
	return out
}

// ShortPVE turns "pve-manager/9.0.11/abc123" into "9.0.11".
func ShortPVE(s string) string {
	if p := strings.Split(s, "/"); len(p) >= 2 && p[0] == "pve-manager" {
		return p[1]
	}
	return s
}

// ShortKernel turns "Linux 7.0.14-20-pve #1 SMP …" into "7.0.14-20-pve".
func ShortKernel(s string) string {
	if f := strings.Fields(s); len(f) >= 2 && f[0] == "Linux" {
		return f[1]
	}
	return s
}

// NextBootDiffers is true when the box will boot a kernel other than the one it runs (both known).
func (s System) NextBootDiffers() bool {
	return s.Host.KernelRunning != Unknown && s.Host.KernelNextBoot != Unknown && s.Host.KernelRunning != s.Host.KernelNextBoot
}