package monitor

import (
	"context"
	"encoding/json"
	"fmt"
	"log"
	"sync"
	"time"

	"gitea.dooplex.hu/admin/felhom-hub/internal/hetznerapi"
	"gitea.dooplex.hu/admin/felhom-hub/internal/offsite"
	"gitea.dooplex.hu/admin/felhom-hub/internal/store"
)

// OffsiteBoxChecker (v0.64.0, R-5) watches the SHARED POOL BOX as a whole — the aggregate the
// per-customer OffsiteChecker cannot see. Two independent box-level signals, one checker, mirroring the
// OffsiteChecker/StorageFillChecker shape (escalation-only emit, recovery re-arms silently, born/persistent
// via an unseeded band). It is DELIBERATELY separate from OffsiteChecker — a different data source (the
// Hetzner unified API, not the controller report) and a customer-less scope.
//
//   - FILL: box used vs box capacity (from the box TYPE's size, never stats.size) at warn 80% / crit 90%.
//   - OVERSUBSCRIPTION: Σ(shared+enabled customers' soft quotas) vs capacity, at a warn ratio (2.0×). The
//     number that says how far the sold promises exceed the disk. Independent of fill (both can fire).
//
// Fetch is throttled (boxFetchInterval); between refreshes Check() serves the cached snapshot. A failed
// fetch keeps the last snapshot (marked Degraded) and never drives a band transition — absence of data is
// NEVER treated as 0%. Events carry the customer-less scope "pool-box": the dispatcher uses it as a
// cooldown key + display string only, and processCustomer no-ops on it (no prefs → no customer email;
// verified against dispatcher.go), so a box event reaches ONLY the operator channel. NO SaveEvent — the
// scope has no customer row to key it to.
type OffsiteBoxChecker struct {
	api         hetznerapi.CloudAPI
	boxID       int64
	store       *store.Store
	fillWarn    float64
	fillCrit    float64
	oversubWarn float64
	onEvent     EventNotifyFunc
	logger      *log.Logger
	now         func() time.Time // injectable clock (tests)

	mu          sync.Mutex
	snap        BoxSnapshot
	haveSnap    bool
	lastFetch   time.Time
	fillBand    string // "" until first eval → born/persistent (a born-breach emits on the first sweep)
	oversubBand string
}

// offsiteBoxScope is the customer-less cooldown/display key for pool-box events.
const offsiteBoxScope = "pool-box"

const (
	defaultOffsiteBoxFillWarnPercent = 80.0
	defaultOffsiteBoxFillCritPercent = 90.0
	defaultOffsiteOversubWarnRatio   = 2.0
	// boxFetchInterval throttles the Hetzner read: Check() runs on the 60 s sweep but fetches at most
	// once per this window (≈4 API reads/hour, not ≈60). A manual page load never forces a fetch.
	boxFetchInterval = 15 * time.Minute
)

// BoxSnapshot is the cached pool-box aggregate the web layer renders. All sizes are BYTES. FillBand /
// OversubBand carry the checker's own band verdict so the UI colors bars EXACTLY as the alerts fire (no
// threshold re-derivation in the web layer).
type BoxSnapshot struct {
	CapacityBytes int64
	UsedBytes     int64
	DataBytes     int64
	SnapshotBytes int64
	FillPercent   float64
	SumQuotaGB    int64
	Ratio         float64 // Σ(shared quota bytes) / capacity
	FillBand      string  // "" | ok | warning | critical
	OversubBand   string  // "" | ok | warning
	FetchedAt     time.Time
	BoxType       string
	Degraded      bool // last fetch failed OR capacity==0 → render stale; no alert transitions
}

// NewOffsiteBoxChecker builds the checker. Invalid thresholds fall back to the documented defaults
// (warn 80% / crit 90% / oversub 2.0×). Nothing is seeded → the first Check that finds a breach emits
// (born/persistent; the dispatcher's 1 h cooldown dedups a hub restart).
func NewOffsiteBoxChecker(api hetznerapi.CloudAPI, boxID int64, s *store.Store, fillWarn, fillCrit, oversubWarn float64, onEvent EventNotifyFunc, logger *log.Logger) *OffsiteBoxChecker {
	if fillWarn <= 0 || fillWarn >= 100 {
		fillWarn = defaultOffsiteBoxFillWarnPercent
	}
	if fillCrit <= 0 || fillCrit > 100 || fillCrit <= fillWarn {
		fillCrit = defaultOffsiteBoxFillCritPercent
	}
	if fillCrit <= fillWarn {
		fillWarn, fillCrit = defaultOffsiteBoxFillWarnPercent, defaultOffsiteBoxFillCritPercent
	}
	if oversubWarn <= 0 {
		oversubWarn = defaultOffsiteOversubWarnRatio
	}
	c := &OffsiteBoxChecker{
		api: api, boxID: boxID, store: s,
		fillWarn: fillWarn, fillCrit: fillCrit, oversubWarn: oversubWarn,
		onEvent: onEvent, logger: logger, now: time.Now,
	}
	logger.Printf("[INFO] Offsite pool-box checker initialized: box=%d fill warn=%.0f%% crit=%.0f%%, oversub warn=%.2fx, refresh %s",
		boxID, fillWarn, fillCrit, oversubWarn, boxFetchInterval)
	return c
}

// Check runs on the 60 s sweep. It fetches (throttled), recomputes the snapshot, and emits on each
// band escalation. Recovery de-escalation re-arms silently. Degraded data drives no transition.
func (c *OffsiteBoxChecker) Check() {
	c.mu.Lock()
	defer c.mu.Unlock()

	// Fetch throttle: between refreshes serve the cache — bands only move on a fresh fetch.
	if c.haveSnap && c.now().Sub(c.lastFetch) < boxFetchInterval {
		return
	}
	c.lastFetch = c.now() // updated even on failure → a failing API is retried once per window, not per sweep

	box, err := c.api.GetStorageBox(context.Background(), c.boxID)
	if err != nil {
		c.logger.Printf("[WARN] Offsite pool-box: refresh failed (keeping last snapshot): %v", err)
		if c.haveSnap {
			c.snap.Degraded = true // serve the last-known, visibly stale; NO band transition (D)
		}
		return
	}

	sumQuotaGB, qerr := c.sumSharedQuotaGB()
	if qerr != nil {
		c.logger.Printf("[WARN] Offsite pool-box: quota sum failed (ratio omitted this cycle): %v", qerr)
		sumQuotaGB = 0 // a wrong sum is worse than a nominal 0.00× — never emit oversub off bad data
	}

	capacity := box.StorageBoxType.Size
	used := box.Stats.Size
	snap := BoxSnapshot{
		CapacityBytes: capacity, UsedBytes: used,
		DataBytes: box.Stats.SizeData, SnapshotBytes: box.Stats.SizeSnapshots,
		SumQuotaGB: sumQuotaGB, FetchedAt: c.now(), BoxType: box.StorageBoxType.Name,
	}
	if capacity > 0 {
		snap.FillPercent = float64(used) * 100 / float64(capacity)
		snap.Ratio = float64(sumQuotaGB<<30) / float64(capacity)
		snap.FillBand = bandForPercent(snap.FillPercent, c.fillWarn, c.fillCrit)
		snap.OversubBand = bandOK
		if snap.Ratio >= c.oversubWarn {
			snap.OversubBand = bandWarning // ratio is single-threshold — no "critical"
		}
	} else {
		snap.Degraded = true // zero capacity (initializing box / probe surprise) — guard the division
	}
	c.snap = snap
	c.haveSnap = true

	if snap.Degraded {
		c.logger.Printf("[INFO] Offsite pool-box refreshed: DEGRADED (capacity unavailable) — box %d", c.boxID)
		return // no band transitions on degraded data
	}
	// Periodic operator visibility of the pool trend (one line per 15-min refresh; keys, no secrets).
	c.logger.Printf("[INFO] Offsite pool-box refreshed: %.1f%% full (%s of %s), Σ shared quota %d GB, oversub %.2fx",
		snap.FillPercent, fmtSize(snap.UsedBytes), fmtSize(snap.CapacityBytes), snap.SumQuotaGB, snap.Ratio)

	// FILL band (escalation-only; recovery re-arms because bandOK has rank 0).
	if bandRank(snap.FillBand) > bandRank(c.fillBand) {
		c.emitFill(snap, snap.FillBand)
	}
	c.fillBand = snap.FillBand

	// OVERSUBSCRIPTION band — independent signal (both can fire in one sweep; neither masks the other).
	if bandRank(snap.OversubBand) > bandRank(c.oversubBand) {
		c.emitOversub(snap)
	}
	c.oversubBand = snap.OversubBand
}

// Snapshot returns the current cached aggregate + whether one exists (mutex copy-out). The web layer's
// only source — it NEVER fetches from Hetzner in the request path.
func (c *OffsiteBoxChecker) Snapshot() (BoxSnapshot, bool) {
	c.mu.Lock()
	defer c.mu.Unlock()
	return c.snap, c.haveSnap
}

// FillState / OversubState expose the current bands (tests).
func (c *OffsiteBoxChecker) FillState() string    { c.mu.Lock(); defer c.mu.Unlock(); return orUnknown(c.fillBand) }
func (c *OffsiteBoxChecker) OversubState() string  { c.mu.Lock(); defer c.mu.Unlock(); return orUnknown(c.oversubBand) }

func orUnknown(b string) string {
	if b == "" {
		return "unknown"
	}
	return b
}

// sumSharedQuotaGB sums the soft quotas of every ENABLED, SHARED customer from the authoritative
// ConfigJSON descriptor (never the report echo). Dedicated + disabled customers are excluded.
func (c *OffsiteBoxChecker) sumSharedQuotaGB() (int64, error) {
	cfgs, err := c.store.ListCustomerConfigs()
	if err != nil {
		return 0, err
	}
	var sum int64
	for _, cfg := range cfgs {
		d, derr := offsite.ReadDescriptor(cfg.ConfigJSON)
		if derr != nil || d == nil {
			continue
		}
		if d.Enabled && d.Type == "shared" && d.QuotaGB > 0 {
			sum += int64(d.QuotaGB)
		}
	}
	return sum, nil
}

func (c *OffsiteBoxChecker) emitFill(snap BoxSnapshot, band string) {
	var severity, message string
	switch band {
	case bandCritical:
		severity = "critical"
		message = fmt.Sprintf("Offsite pool box %.0f%% full (%s of %s) — approaching capacity; add capacity or reduce retention before customer offsite runs start failing",
			snap.FillPercent, fmtSize(snap.UsedBytes), fmtSize(snap.CapacityBytes))
	case bandWarning:
		severity = "warning"
		message = fmt.Sprintf("Offsite pool box %.0f%% full (%s of %s) — the shared pool is filling",
			snap.FillPercent, fmtSize(snap.UsedBytes), fmtSize(snap.CapacityBytes))
	default:
		return
	}
	details, _ := json.Marshal(map[string]any{
		"scope": offsiteBoxScope, "capacity_bytes": snap.CapacityBytes, "used_bytes": snap.UsedBytes,
		"fill_percent": snap.FillPercent, "warn_percent": c.fillWarn, "crit_percent": c.fillCrit,
	})
	c.logger.Printf("[INFO] Offsite pool-box fill: %.0f%% (%s)", snap.FillPercent, band)
	// NO SaveEvent — the scope is customer-less; emit straight to the operator dispatcher.
	if c.onEvent != nil {
		c.onEvent(offsiteBoxScope, "offsite_box_fill", severity, message, string(details), "hub")
	}
}

func (c *OffsiteBoxChecker) emitOversub(snap BoxSnapshot) {
	message := fmt.Sprintf("Offsite pool oversubscription %.2fx — Σ(shared soft quotas) %d GB against %s capacity exceeds the %.2fx threshold; a full-usage scenario would overrun the pool",
		snap.Ratio, snap.SumQuotaGB, fmtSize(snap.CapacityBytes), c.oversubWarn)
	details, _ := json.Marshal(map[string]any{
		"scope": offsiteBoxScope, "sum_quota_gb": snap.SumQuotaGB, "capacity_bytes": snap.CapacityBytes,
		"ratio": snap.Ratio, "oversub_warn_ratio": c.oversubWarn,
	})
	c.logger.Printf("[INFO] Offsite pool-box oversub: %.2fx (Σquota %d GB)", snap.Ratio, snap.SumQuotaGB)
	if c.onEvent != nil {
		c.onEvent(offsiteBoxScope, "offsite_box_oversub", "warning", message, string(details), "hub")
	}
}

// fmtSize renders bytes as GB (one decimal) below 1 TB, TB above — for the operator email/log only.
func fmtSize(b int64) string {
	const gb = 1 << 30
	if b >= 1<<40 {
		return fmt.Sprintf("%.2f TB", float64(b)/float64(int64(1)<<40))
	}
	return fmt.Sprintf("%.1f GB", float64(b)/float64(gb))
}