// Pusher periodically uploads system telemetry to the HarborForge
// backend's /monitor/server/heartbeat endpoint. Replaces the standalone
// `harborforge-monitor` daemon — the plugin's lifecycle (host gateway
// start/stop) bounds the heartbeat loop, so no separate process need
// supervise it.
//
// Wire shape mirrors HarborForge.Monitor's `telemetry.Payload`
// (flat `cpu_pct/mem_pct/...` fields + `X-API-Key` header). The
// translation from internal `telemetry.Snapshot` to that shape lives
// in buildPayload; HF backend stays unchanged.

package monitor

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"strings"
	"sync"
	"time"

	"git.hangman-lab.top/zhi/HarborForge.PlexumPlugin/internal/telemetry"
)

// PushPayload is the wire shape POSTed to /monitor/server/heartbeat —
// 1:1 with HarborForge.Monitor's `telemetry.Payload`.
type PushPayload struct {
	Identifier     string    `json:"identifier"`
	PluginVersion  string    `json:"plugin_version,omitempty"`
	Agents         []any     `json:"agents"`
	NginxInstalled bool      `json:"nginx_installed"`
	NginxSites     []string  `json:"nginx_sites"`
	CPUPct         float64   `json:"cpu_pct,omitempty"`
	MemPct         float64   `json:"mem_pct,omitempty"`
	DiskPct        float64   `json:"disk_pct,omitempty"`
	SwapPct        float64   `json:"swap_pct,omitempty"`
	LoadAvg        []float64 `json:"load_avg,omitempty"`
	UptimeSeconds  uint64    `json:"uptime_seconds,omitempty"`
}

// PusherConfig is the operator-supplied tuning.
type PusherConfig struct {
	BackendURL string        // e.g. https://hf-api.hangman-lab.top
	APIKey     string        // sent as X-API-Key
	Interval   time.Duration // default 30s when <=0
}

// Pusher runs the periodic POST loop. One per plugin process.
type Pusher struct {
	cfg     PusherConfig
	collect func() telemetry.Snapshot
	log     LogFunc
	http    *http.Client

	// stats — for the monitor_telemetry tool / status surfacing.
	mu          sync.RWMutex
	lastSentAt  time.Time
	lastStatus  int
	lastErr     string
	successHits uint64
	errHits     uint64
}

// NewPusher constructs the loop runner. collect must be a snapshot
// producer (caller usually wires it to telemetry.Collect with
// SampleCPU=true).
func NewPusher(cfg PusherConfig, collect func() telemetry.Snapshot, log LogFunc) *Pusher {
	if cfg.Interval <= 0 {
		cfg.Interval = 30 * time.Second
	}
	if log == nil {
		log = func(string, string, map[string]any) {}
	}
	return &Pusher{
		cfg:     cfg,
		collect: collect,
		log:     log,
		http:    &http.Client{Timeout: 15 * time.Second},
	}
}

// Run drives the push loop until ctx is cancelled. Returns ctx.Err().
// First push happens immediately so the backend sees this claw alive
// without waiting an interval.
func (p *Pusher) Run(ctx context.Context) error {
	if p.cfg.BackendURL == "" {
		p.log("warn", "monitor push disabled (empty backendURL)", nil)
		return nil
	}
	if p.cfg.APIKey == "" {
		p.log("warn", "monitor push disabled (empty apiKey)", nil)
		return nil
	}
	url := strings.TrimRight(p.cfg.BackendURL, "/") + "/monitor/server/heartbeat"

	tick := time.NewTicker(p.cfg.Interval)
	defer tick.Stop()

	p.pushOnce(ctx, url)
	for {
		select {
		case <-ctx.Done():
			return ctx.Err()
		case <-tick.C:
			p.pushOnce(ctx, url)
		}
	}
}

func (p *Pusher) pushOnce(ctx context.Context, url string) {
	snap := p.collect()
	body, err := json.Marshal(buildPayload(snap))
	if err != nil {
		p.recordErr("marshal: " + err.Error())
		return
	}
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, url, bytes.NewReader(body))
	if err != nil {
		p.recordErr("build req: " + err.Error())
		return
	}
	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("X-API-Key", p.cfg.APIKey)
	res, err := p.http.Do(req)
	if err != nil {
		p.recordErr("send: " + err.Error())
		p.log("warn", "monitor push failed", map[string]any{"err": err.Error()})
		return
	}
	defer res.Body.Close()
	raw, _ := io.ReadAll(res.Body)
	if res.StatusCode < 200 || res.StatusCode >= 300 {
		p.recordErr(fmt.Sprintf("%d: %s", res.StatusCode, truncate(raw, 200)))
		p.log("warn", "monitor push non-2xx", map[string]any{
			"status": res.StatusCode, "body": truncate(raw, 200),
		})
		return
	}
	p.recordOK(res.StatusCode)
}

// Stats exposes a copy of the latest push state for diagnostics
// (harborforge_monitor_telemetry tool surfaces this).
type PushStats struct {
	LastSentAt   time.Time
	LastStatus   int
	LastErr      string
	SuccessCount uint64
	ErrorCount   uint64
}

func (p *Pusher) Stats() PushStats {
	p.mu.RLock()
	defer p.mu.RUnlock()
	return PushStats{
		LastSentAt:   p.lastSentAt,
		LastStatus:   p.lastStatus,
		LastErr:      p.lastErr,
		SuccessCount: p.successHits,
		ErrorCount:   p.errHits,
	}
}

func (p *Pusher) recordOK(status int) {
	p.mu.Lock()
	defer p.mu.Unlock()
	p.lastSentAt = time.Now().UTC()
	p.lastStatus = status
	p.lastErr = ""
	p.successHits++
}

func (p *Pusher) recordErr(msg string) {
	p.mu.Lock()
	defer p.mu.Unlock()
	p.lastSentAt = time.Now().UTC()
	p.lastErr = msg
	p.errHits++
}

// buildPayload translates the internal Snapshot into the flat
// PushPayload shape the backend expects. agents is passed through as
// []any (one entry per agent — id/model/state preserved).
func buildPayload(snap telemetry.Snapshot) PushPayload {
	agents := make([]any, 0, len(snap.Agents))
	for _, a := range snap.Agents {
		agents = append(agents, map[string]any{
			"id":    a.ID,
			"model": a.Model,
			"state": a.State,
		})
	}
	return PushPayload{
		Identifier:    snap.Identifier,
		PluginVersion: snap.PluginInfo.Version,
		Agents:        agents,
		// nginx detection is independent monitor's responsibility today;
		// HF plugin leaves it blank rather than rediscovering nginx
		// state. Operators that need it can keep the standalone monitor
		// alongside or wait for a follow-up commit.
		NginxInstalled: false,
		NginxSites:     []string{},
		CPUPct:         round1(snap.CPU.UsedPercent),
		MemPct:         round1(snap.Memory.UsedPercent),
		DiskPct:        round1(snap.Disk.UsedPercent),
		SwapPct:        round1(snap.Swap.UsedPercent),
		LoadAvg:        []float64{round2(snap.Load.One), round2(snap.Load.Five), round2(snap.Load.Fifteen)},
		UptimeSeconds:  snap.UptimeSecs,
	}
}

func round1(v float64) float64 { return float64(int64(v*10+0.5)) / 10 }
func round2(v float64) float64 { return float64(int64(v*100+0.5)) / 100 }

func truncate(b []byte, n int) string {
	if len(b) <= n {
		return string(b)
	}
	return string(b[:n]) + "…"
}