package localapi

import (
	"context"
	"encoding/json"
	"io"
	"log/slog"
	"testing"

	"gitea.dooplex.hu/admin/felhom-agent/internal/hub"
	"gitea.dooplex.hu/admin/felhom-agent/internal/storage"
)

// R-116 — the backup-target flag must be reachable from the row the CONTROLLER keys on.
//
// THE DEFECT. The controller resolves the drive-absent alarm by the registered StoragePath, which for
// an external drive is the GUEST path. When the device vanishes, Observe's exactMountDevice fails, so
// BackingDevice becomes "" and RoleForStorage returns RoleSystem (role.go:180-181) — the guest-path
// block is skipped and the flag-bearing row loses its guest path. It keeps its MountPath, so the union
// loop DEDUPES the registry row away, and /disks carries NO row with that guest path at all.
// driveTargetByPath then has no entry, isTarget[guestPath] is a MISSING KEY, and the specific
// backup_target_absent alarm cannot fire — the generic storage_disconnected goes out instead, while
// the RETURN (rows rejoined) fires the specific recovery. An operator gets a pair they cannot match.
// Measured live: felhom.eu audits/SESSION-C-2026-07-29.md §5.
//
// These tests exercise the REAL GET /disks response and assert the emitted JSON, because the failure
// class is "the value is on the wrong row" — a test that hand-builds rows proves nothing about which
// row the handler actually emits.

// targetRowServer builds a /disks server whose primary backup tier is `primaryTarget`, over the given
// Observe targets. boundCheck/deviceCheck are pinned so the R-113 conjunction is not the variable
// under test here.
func targetRowServer(t *testing.T, primaryTarget string, targets []hub.StorageTarget) *Server {
	t.Helper()
	return targetRowServerWithDrives(t, primaryTarget, targets, nil)
}

// targetRowServerWithDrives additionally wires the REGISTRY union source. v0.115.0's tests left
// DriveTargets nil, so the union loop never ran and the two-row absent shape — the actual defect — was
// invisible to the whole suite. Any test about which row carries what MUST populate this.
func targetRowServerWithDrives(t *testing.T, primaryTarget string, targets []hub.StorageTarget,
	drives []storage.KnownTarget) *Server {
	t.Helper()
	var known storage.KnownTargets
	if drives != nil {
		known = fakeKnownTargets{drives: drives}
	}
	srv, err := NewServer(Options{
		DriveTargets: known,
		ListenAddr:   "127.0.0.1:0",
		Guests:       &fakeGuestsCfg{}, Backups: &fakeBackups{}, Store: &fakeStore{},
		Storage: fakeStorage{targets: targets},
		// Service is REQUIRED: normalizeBackupTiers (backup_tiers.go:21-22) drops any tier with a nil
		// Service, and the legacy fallback then yields TargetID "" — which silently makes every
		// BackupTarget false and would make these tests pass for the wrong reason.
		BackupTiers: []BackupTier{{TargetID: primaryTarget, Primary: true, Service: &fakeBackups{}}},
		Tokens:      staticTokens{"A": 8200},
		Disks:       &fakeDiskOps{probe: storage.DeviceProbe{Probed: true, HasFilesystem: true, FSType: "ext4"}},
		DiskGate:    &fakeGate{}, HostReader: sysOnSDA(),
		Logger: slog.New(slog.NewTextHandler(io.Discard, nil)),
	})
	if err != nil {
		t.Fatal(err)
	}
	srv.baseCtx = context.Background()
	srv.boundCheck = func(string) bool { return true }
	srv.deviceCheck = func(string) bool { return true }
	return srv
}

// wireDisks returns the decoded /disks rows exactly as the controller receives them.
func wireDisks(t *testing.T, srv *Server) []map[string]any {
	t.Helper()
	body := do(t, srv.Handler(), "GET", "/disks", "A", "").Body.Bytes()
	var w struct {
		Data struct {
			Disks []map[string]any `json:"disks"`
		} `json:"data"`
	}
	if err := json.Unmarshal(body, &w); err != nil {
		t.Fatalf("decode /disks: %v (%s)", err, body)
	}
	return w.Data.Disks
}

// isTargetByPath reproduces the controller's driveTargetByPath EXACTLY (intermediary.go:602-616):
// both keyings, value = backup_target. This is the map whose missing key is the whole defect, so the
// assertion is made against a faithful copy of it rather than against a field in isolation.
func isTargetByPath(disks []map[string]any) map[string]bool {
	out := map[string]bool{}
	for _, d := range disks {
		bt, _ := d["backup_target"].(bool)
		if gp, ok := d["guest_path"].(string); ok && gp != "" {
			out[gp] = bt
		}
		if mp, ok := d["mount_path"].(string); ok && mp != "" {
			out[mp] = bt
		}
	}
	return out
}

// theAbsentTarget is the absent-target Observe row, CORRECTED in v0.116.0 to the shape the live box
// actually produces.
//
// THIS FIXTURE IS WHY AN INERT FIX SHIPPED GREEN. As written for v0.115.0 it supplied
// `MountPath: "/mnt/mentes"` — a field the real absent state does NOT have. The same exactMount failure
// that empties BackingDevice empties MountPath (observe.go:184-190), so on the live box this row carries
// `mount_path: ""`, and v0.115.0's `StablePathForRaw(t.MountPath)` was therefore
// `StablePathForRaw("")` == "". The fixture handed the code a value production never supplies, the test
// went green, and the fix was inert on real hardware — twice.
//
// Captured payload this now mirrors, field for field:
// felhom.eu audits/DIAG-r116-disks-payload-2026-07-30.md §6.2.
var theAbsentTarget = hub.StorageTarget{
	Name: "felhom-backup", Type: hub.StorageTypeLocalDir,
	MountPath: "", BackingDevice: "", ConfigPath: "/mnt/mentes",
	State: hub.StorageStateDisconnected,
	// DurableID degrades off the fs-UUID exactly as the live payload showed (`path:/mnt/cel` there).
	DurableID: "path:/mnt/mentes",
}

// theAbsentRegistryRow is the OTHER half of the live absent payload — the registry/union row. Its
// MountPath comes from the systemd .mount unit FILE (registry_known.go:40-75), which never consults the
// mount table, so it survives the device intact. Its presence is what made /disks carry the drive TWICE.
var theAbsentRegistryRow = []storage.KnownTarget{
	{Name: "9303-uuid", Type: hub.StorageTypeUSB, MountPath: "/mnt/mentes",
		DurableID: "uuid:9303", UUID: "9303"},
}

// ── the observable that must move ───────────────────────────────────────────────────────────────

// RED-PROOF: delete the `di.GuestPath == "" && di.BackupTarget && t.BackingDevice == ""` block and
// this fails with "the guest path the controller keys on is MISSING from /disks entirely".
func TestAbsentBackupTargetIsResolvableByGuestPath(t *testing.T) {
	disks := wireDisks(t, targetRowServerWithDrives(t, "felhom-backup",
		[]hub.StorageTarget{theAbsentTarget}, theAbsentRegistryRow))
	isTarget := isTargetByPath(disks)

	const guestPath = "/mnt/felhom-drives/mentes"
	got, present := isTarget[guestPath]
	if !present {
		t.Fatalf("isTarget[%q] is a MISSING KEY — the guest path the controller keys on is missing from "+
			"/disks entirely, so notifyDriveAbsent takes the generic branch and backup_target_absent "+
			"can never fire (R-116)", guestPath)
	}
	if !got {
		t.Fatalf("isTarget[%q] = FALSE. Both rows for this drive reached the wire and the registry row — "+
			"appended last, BackupTarget defaulted false — overwrote the flag-bearing row's true. This is "+
			"the measured live defect, not a hypothetical: rows=%d", guestPath, len(disks))
	}
}

// ── V2: the new guest path must NOT make the gate read the drive as PRESENT ─────────────────────

// This is the over-correction guard, in the exact component under test. planDriveGates computes
// present[gp] = present[gp] || d.BoundUnderParent. If the row we now emit carried a true
// BoundUnderParent, this fix would SILENCE the alarm it exists to raise.
func TestAbsentTargetRowDoesNotRegisterPresence(t *testing.T) {
	srv := targetRowServer(t, "felhom-backup", []hub.StorageTarget{theAbsentTarget})
	// deviceCheck/boundCheck are pinned TRUE — the strongest possible case for a false positive.
	// The row must still report bound_under_parent=false, because that field is only ever assigned
	// inside the guest-path blocks a system-role row does not enter.
	for _, d := range wireDisks(t, srv) {
		if d["guest_path"] != "/mnt/felhom-drives/mentes" {
			continue
		}
		if bup, _ := d["bound_under_parent"].(bool); bup {
			t.Fatal("the absent backup-target row reports bound_under_parent=true — planDriveGates " +
				"would compute present=true, the Stop branch would never run, and this fix would " +
				"SUPPRESS the very alarm it exists to raise")
		}
		return
	}
	t.Fatal("the absent target row never reached the wire")
}

// ── V1: the gates, each on its own ──────────────────────────────────────────────────────────────

// Case B is the COMMON fresh-box shape, not an edge: the tier target is the builtin `local` on the
// root fs. It must never acquire a guest path.
func TestCaseBLocalTargetGetsNoGuestPath(t *testing.T) {
	disks := wireDisks(t, targetRowServer(t, "local", []hub.StorageTarget{
		{Name: "local", Type: "local", MountPath: "/var/lib/vz", BackingDevice: "", State: hub.StorageStateAttached},
	}))
	for _, d := range disks {
		if gp, _ := d["guest_path"].(string); gp != "" {
			t.Errorf("the Case B target on %v acquired guest path %q — a system-drive backup target "+
				"must not cross into the guest", d["mount_path"], gp)
		}
	}
}

// A storage that is RoleSystem because it is genuinely system-BACKED (non-empty BackingDevice on the
// system disk) must be excluded — this is the case StablePathForRaw would NOT have filtered, since
// /mnt/<name> maps to a real stable path. The BackingDevice gate is what stops it.
func TestSystemBackedTargetUnderMntGetsNoGuestPath(t *testing.T) {
	disks := wireDisks(t, targetRowServer(t, "sysbackup", []hub.StorageTarget{
		// sysOnSDA() makes /dev/sda the system disk, so this classifies RoleSystem with a REAL device.
		{Name: "sysbackup", Type: hub.StorageTypeLocalDir, MountPath: "/mnt/sysbackup",
			BackingDevice: "/dev/sda1", State: hub.StorageStateAttached},
	}))
	for _, d := range disks {
		if gp, _ := d["guest_path"].(string); gp != "" {
			t.Errorf("a system-BACKED backup target acquired guest path %q — the BackingDevice gate "+
				"failed and the :213-214 boundary was widened", gp)
		}
	}
}

// ── the negative ────────────────────────────────────────────────────────────────────────────────

// A drive that is NOT the target must not acquire the flag on any row, present or absent.
func TestNonTargetDriveNeverCarriesTheFlag(t *testing.T) {
	disks := wireDisks(t, targetRowServer(t, "felhom-backup", []hub.StorageTarget{
		{Name: "adat", Type: hub.StorageTypeLocalDir, MountPath: "/mnt/adat",
			BackingDevice: "", State: hub.StorageStateDisconnected},
	}))
	for _, d := range disks {
		if bt, _ := d["backup_target"].(bool); bt {
			t.Errorf("non-target drive %v reports backup_target=true", d["name"])
		}
		if gp, _ := d["guest_path"].(string); gp != "" {
			t.Errorf("an absent NON-target drive acquired guest path %q via the R-116 fallback — the "+
				"BackupTarget gate failed", gp)
		}
	}
}

// ── v0.116.0 — the join, and the regression it must not cause ───────────────────────────────────

// THE JOIN. With the device gone the two records of one drive share no runtime field, so the dedup has
// to key on the one thing both can still derive: the CONFIGURED path (storage.cfg's `path` on the
// Observe side, the .mount unit's `Where` on the registry side), expressed as the stable guest path.
// This pins that exactly one row survives — because driveTargetByPath ASSIGNS rather than ORs, so two
// rows disagreeing on the flag is decided by append order, which is not a contract anyone should rely on.
//
// RED-PROOF: delete the `seenGuest[gp]` skip in the union loop and this fails with rows=2.
func TestAbsentTargetAppearsExactlyOnce(t *testing.T) {
	disks := wireDisks(t, targetRowServerWithDrives(t, "felhom-backup",
		[]hub.StorageTarget{theAbsentTarget}, theAbsentRegistryRow))

	const guestPath = "/mnt/felhom-drives/mentes"
	var rows []map[string]any
	for _, d := range disks {
		if gp, _ := d["guest_path"].(string); gp == guestPath {
			rows = append(rows, d)
		}
	}
	if len(rows) != 1 {
		t.Fatalf("the absent drive is carried by %d rows, want exactly 1 — with two rows the flag the "+
			"controller reads is decided by append order, not by the fix. rows=%v", len(rows), rows)
	}
	if bt, _ := rows[0]["backup_target"].(bool); !bt {
		t.Error("the surviving row does not carry backup_target=true")
	}
}

// THE REGRESSION THIS FIX MUST NOT CAUSE, and the reason neither obvious option was taken.
//
// The controller reads `d.BackupTarget && d.MountPath != ""` as "a real drive with its own mountpoint —
// HEALTHY" and returns immediately (backup_target_offer.go:79). So the two candidate fixes that look
// smallest — back-filling MountPath onto the Observe row, or teaching the registry row the flag (its
// MountPath is non-empty, read from the stale unit file) — BOTH produce a row satisfying that predicate
// while the drive is missing. Either would have silently regressed R-114, which shipped 2026-07-29 and
// tells the customer „A rendszermentés meghajtója nem érhető el" in exactly this state, flipping it back
// to a false healthy.
//
// R-114's correctness currently rests on the absent-state rows NOT combining the flag with a mount path.
// That coupling was invisible until the payload was captured, and it is what this test pins.
//
// RED-PROOF: set `MountPath: "/mnt/mentes"` on theAbsentTarget (v0.115.0's fixture value) and this fails.
func TestAbsentTargetKeepsR114DegradedSignal(t *testing.T) {
	disks := wireDisks(t, targetRowServerWithDrives(t, "felhom-backup",
		[]hub.StorageTarget{theAbsentTarget}, theAbsentRegistryRow))

	for _, d := range disks {
		bt, _ := d["backup_target"].(bool)
		mp, _ := d["mount_path"].(string)
		if bt && mp != "" {
			t.Fatalf("row %v carries backup_target=true AND mount_path=%q while the drive is ABSENT. "+
				"resolveBackupTargetState (backup_target_offer.go:79) reads that as \"a real drive with "+
				"its own mountpoint — healthy\" and returns before its TargetAbsent branch, so the "+
				"customer is told the backup target is fine while its drive is gone. That is R-114, "+
				"regressed.", d["name"], mp)
		}
	}
}

// PRESENT-STATE PARITY. The fix must change nothing when the drive is there. Present state is the
// state every healthy box is in, so a change here reaches the whole fleet; absent state reaches only a
// box with a problem. Both rows are supplied, exactly as on a live present box, and the pre-existing
// MountPath dedup must still collapse them to one COMPLETE row.
func TestPresentTargetPayloadUnchanged(t *testing.T) {
	present := hub.StorageTarget{
		Name: "felhom-backup", Type: hub.StorageTypeLocalDir,
		MountPath: "/mnt/mentes", BackingDevice: "/dev/sdb", ConfigPath: "/mnt/mentes",
		State: hub.StorageStateAttached, DurableID: "uuid:9303",
	}
	disks := wireDisks(t, targetRowServerWithDrives(t, "felhom-backup",
		[]hub.StorageTarget{present}, theAbsentRegistryRow))

	var rows []map[string]any
	for _, d := range disks {
		if d["name"] == "felhom-backup" || d["mount_path"] == "/mnt/mentes" {
			rows = append(rows, d)
		}
	}
	if len(rows) != 1 {
		t.Fatalf("present state carries the drive on %d rows, want 1 (the MountPath dedup): %v", len(rows), rows)
	}
	r := rows[0]
	for field, want := range map[string]any{
		"mount_path": "/mnt/mentes", "guest_path": "/mnt/felhom-drives/mentes",
		"backing_device": "/dev/sdb", "role": "user-data", "state": "attached",
		"backup_target": true, "bound_under_parent": true, "durable_id": "uuid:9303",
	} {
		if got := r[field]; got != want {
			t.Errorf("present-state %s = %v, want %v — the fix altered the healthy payload", field, got, want)
		}
	}
}

// The negative, with the union loop actually running: a non-target absent drive gains the flag on no row
// and keeps its own registry row (nothing to dedup against, since no Observe row claims its guest path).
func TestAbsentNonTargetKeepsItsRegistryRowAndNoFlag(t *testing.T) {
	disks := wireDisks(t, targetRowServerWithDrives(t, "felhom-backup",
		[]hub.StorageTarget{{Name: "adat", Type: hub.StorageTypeLocalDir, MountPath: "",
			BackingDevice: "", ConfigPath: "/mnt/adat", State: hub.StorageStateDisconnected}},
		[]storage.KnownTarget{{Name: "adat-uuid", Type: hub.StorageTypeUSB,
			MountPath: "/mnt/adat", DurableID: "uuid:1111", UUID: "1111"}}))

	isTarget := isTargetByPath(disks)
	for k, v := range isTarget {
		if v {
			t.Errorf("isTarget[%q] = true for a NON-target drive — the BackupTarget gate failed", k)
		}
	}
	if _, ok := isTarget["/mnt/felhom-drives/adat"]; !ok {
		t.Error("the non-target drive lost its guest-path key entirely — the union row was over-suppressed")
	}
}