package backup

import (
	"bytes"
	"context"
	"fmt"
	"log"
	"strings"
	"sync"
	"sync/atomic"
	"testing"
	"time"

	"gitea.dooplex.hu/admin/felhom-controller/internal/settings"
)

// inventoryFixture wires a Manager whose repository answers a fixed snapshot list, and whose per-app
// `stats` calls are observable: how many ran at once, how many in total, and which ones fail.
//
// The delay is what makes the concurrency assertion meaningful — with instant calls a sequential
// implementation could pass a peak-of-1 check by finishing before the next one starts.
func inventoryFixture(t *testing.T, tags []string, statDelay time.Duration, failFor map[string]bool) (*Manager, *int32, *int32, *bytes.Buffer) {
	t.Helper()
	m, sett := newOffboxManager(t)
	if err := sett.SetOffboxTarget(&settings.OffboxTarget{
		Enabled: true, Host: "nas.local", Port: 22, User: "felhom", RepoPath: "/srv/repo",
		Schedule: "daily", EscrowState: "escrowed",
	}); err != nil {
		t.Fatal(err)
	}
	if err := m.WriteOffboxSecrets("KEYMATERIAL", "nas.local ssh-ed25519 HOSTKEY"); err != nil {
		t.Fatal(err)
	}
	if !m.OffboxConfigured() {
		t.Fatal("fixture: the target must be configured or the listing exits early")
	}
	var logbuf bytes.Buffer
	m.logger = log.New(&logbuf, "", 0)

	var snaps []string
	for i, tag := range tags {
		snaps = append(snaps, fmt.Sprintf(`{"short_id":"snap%d","time":"2026-08-0%dT06:00:00Z","tags":["%s"]}`, i, i+1, tag))
	}
	snapshotsJSON := "[" + strings.Join(snaps, ",") + "]"

	var inFlight, peak, total int32
	var mu sync.Mutex
	m.SetOffboxRunner(func(_ context.Context, _ []string, args ...string) ([]byte, error) {
		if contains(args, "snapshots") {
			return []byte(snapshotsJSON), nil
		}
		if !contains(args, "stats") {
			return nil, nil
		}
		atomic.AddInt32(&total, 1)
		cur := atomic.AddInt32(&inFlight, 1)
		mu.Lock()
		if cur > peak {
			peak = cur
		}
		mu.Unlock()
		time.Sleep(statDelay)
		atomic.AddInt32(&inFlight, -1)
		// args carries the snapshot id; map it back to its tag position.
		for i, tag := range tags {
			if contains(args, fmt.Sprintf("snap%d", i)) {
				if failFor[tag] {
					return nil, fmt.Errorf("injected failure for %s", tag)
				}
				return []byte(`{"total_size":1048576}`), nil
			}
		}
		return []byte(`{"total_size":0}`), nil
	})
	return m, &peak, &total, &logbuf
}

// R-351 PART 4 — the per-app size calls run AT ONCE, and never more than the bound at once.
//
// MEASURED on demo-hp against the live off-site target before any change (2026-08-21):
// snapshots --json 2605 ms once, then stats --mode restore-size 2697 ms PER APP, sequential, over
// 5 app tags — 2605 + 5*2697 = ~16.1 s, which is the reported ten-to-fifteen seconds.
//
// THE BOUND IS THE SAFETY PROPERTY, not the speed one. The repository is a Hetzner Storage Box with
// a concurrent-SSH-session cap; a size call that is refused returns SizeBytes 0, which is a SILENT
// UNDER-REPORT of the customer's own data rather than a visible failure. So the peak is asserted,
// not just the total.
func TestOffsiteInventoryList_SizeCallsAreConcurrentButBounded(t *testing.T) {
	tags := []string{"immich", "nextcloud", "opengist", "paperless-ngx", "privatebin", "calibre-web", "vaultwarden"}
	m, peak, total, _ := inventoryFixture(t, tags, 40*time.Millisecond, nil)

	start := time.Now()
	_, err := m.OffsiteInventoryList(context.Background())
	elapsed := time.Since(start)
	if err != nil {
		t.Fatalf("inventory: %v", err)
	}

	if int(*total) != len(tags) {
		t.Errorf("every app needs its own size call: got %d, want %d", *total, len(tags))
	}
	if *peak < 2 {
		t.Errorf("the size calls must run concurrently; peak in flight was %d — that is the sequential shape that cost 16s", *peak)
	}
	if *peak > 4 {
		t.Errorf("peak in flight was %d, above the bound of 4 — an unbounded fan-out risks refused connections, "+
			"and a refused size call silently under-reports the customer's data", *peak)
	}
	// 7 apps at 40ms: sequential would be >=280ms, four-at-a-time is two waves (~80ms).
	if elapsed >= time.Duration(len(tags))*40*time.Millisecond {
		t.Errorf("elapsed %v is the sequential cost — the fan-out is not taking effect", elapsed)
	}
}

// Nothing may be LOST or REORDERED by the fan-out. A missing app reads as "you have no backup of
// this", which is the worst possible thing for this page to say by accident.
func TestOffsiteInventoryList_FanOutLosesNothingAndStaysSorted(t *testing.T) {
	tags := []string{"vaultwarden", "immich", "calibre-web", "opengist", "nextcloud"}
	m, _, _, _ := inventoryFixture(t, tags, time.Millisecond, nil)

	inv, err := m.OffsiteInventoryList(context.Background())
	if err != nil {
		t.Fatalf("inventory: %v", err)
	}
	if len(inv.Apps) != len(tags) {
		t.Fatalf("apps listed = %d, want %d — the fan-out dropped one, which reads as a missing backup", len(inv.Apps), len(tags))
	}
	seen := map[string]bool{}
	for _, a := range inv.Apps {
		seen[a.App] = true
		if a.SizeBytes != 1048576 {
			t.Errorf("%s: size = %d, want the injected value", a.App, a.SizeBytes)
		}
	}
	for _, tag := range tags {
		if !seen[tag] {
			t.Errorf("%s is missing from the listing", tag)
		}
	}
	for i := 1; i < len(inv.Apps); i++ {
		if inv.Apps[i-1].App > inv.Apps[i].App {
			t.Fatalf("the listing must stay sorted; %q came before %q", inv.Apps[i-1].App, inv.Apps[i].App)
		}
	}
	if inv.Empty {
		t.Error("a repository with snapshots is not Empty")
	}
}

// A FAILED size call must still list the app, with size 0, AND still log the WARN. The warning is
// the only thing that distinguishes "0 bytes" from "we could not tell" — and under a fan-out it is
// the easiest thing to lose, because the logging moved off the goroutine that produced the error.
func TestOffsiteInventoryList_FailedSizeStillListsAndStillWarns(t *testing.T) {
	tags := []string{"immich", "opengist"}
	m, _, _, logbuf := inventoryFixture(t, tags, time.Millisecond, map[string]bool{"opengist": true})

	inv, err := m.OffsiteInventoryList(context.Background())
	if err != nil {
		t.Fatalf("a per-app size failure must not fail the whole listing: %v", err)
	}
	if len(inv.Apps) != 2 {
		t.Fatalf("both apps must be listed; got %d", len(inv.Apps))
	}
	for _, a := range inv.Apps {
		if a.App == "opengist" && a.SizeBytes != 0 {
			t.Errorf("an unknown size must be 0, got %d", a.SizeBytes)
		}
		if a.App == "immich" && a.SizeBytes == 0 {
			t.Error("the healthy app's size must survive its neighbour's failure")
		}
	}
	if !strings.Contains(logbuf.String(), "size of opengist's newest snapshot unknown") {
		t.Errorf("the WARN is what separates \"0 bytes\" from \"could not tell\"; log was: %s", logbuf.String())
	}
	if strings.Contains(logbuf.String(), "size of immich's newest snapshot unknown") {
		t.Error("a healthy app must not be warned about")
	}
}