package storage

import "testing"

// v0.87.0 — SystemDisks device-mapper/md walk (IA finding 2, operator ruling 2026-07-13).
// The direction that must be IMPOSSIBLE is a root-backing disk classified as a candidate;
// the direction being fixed is the legacy-boot all-system over-protection (dead wizard).
//
// Fixtures mirror the §3 live transcripts: on the drill host / → /dev/mapper/pve-root →
// dm-1 → slaves sda3 → parent sda; physical disks carry an EMPTY slaves dir (hasDir=true).
// COMPANION red-proofs (run → fail → revert, recorded in REPORT):
//   B: walk returns only the dm node (pre-fix shape) → TestSystemDisks_WalkTopologies legacy
//      fixture fails its system-set assertion.
//   A: pre-fix resolver (no walk) → TestSystemDisks_LegacyBoot_WizardLives fails
//      (reproduces the dead-wizard live shape).
//   D: per-branch conservatism removed (skip unresolvable slaves) → the dangling fixture
//      fails on "scratch classified candidate while walk incomplete".

// walkTopology is one fixture: the host's mounts + sysfs slaves tree, with the disks that
// MUST be system and a scratch disk that must stay outside the set.
type walkTopology struct {
	name       string
	mounts     []Mount
	slaves     map[string][]string
	wantSystem []string // every entry MUST be in the resolved set (signature assertion B)
	scratch    string   // must NOT be in the set (wizard-eligible)
}

func walkTopologies() []walkTopology {
	return []walkTopology{
		{
			// The drill host's exact shape (§3 transcript): legacy boot, LVM root, no ESP mount.
			name:   "legacy LVM root (dm -> partition -> disk)",
			mounts: []Mount{{Device: "/dev/mapper/pve-root", MountPoint: "/", FSType: "ext4"}},
			slaves: map[string][]string{
				"pve-root": {"sda3"},
				"sda":      {}, // physical disk: slaves dir exists, empty (live-probed)
			},
			wantSystem: []string{"/dev/sda"},
			scratch:    "/dev/sdd",
		},
		{
			// md-raid root: BOTH member disks are system.
			name:   "md-raid root (md -> 2 disks)",
			mounts: []Mount{{Device: "/dev/md0", MountPoint: "/", FSType: "ext4"}},
			slaves: map[string][]string{
				"md0": {"sda1", "sdb1"},
			},
			wantSystem: []string{"/dev/sda", "/dev/sdb"},
			scratch:    "/dev/sdd",
		},
		{
			// Plain EFI + raw partitions (the pre-walk demo shape) — no virtual layer at all.
			name: "EFI + raw partitions",
			mounts: []Mount{
				{Device: "/dev/sda2", MountPoint: "/", FSType: "ext4"},
				{Device: "/dev/sda1", MountPoint: "/boot/efi", FSType: "vfat"},
			},
			slaves:     map[string][]string{},
			wantSystem: []string{"/dev/sda"},
			scratch:    "/dev/sdd",
		},
		{
			// felhom-pve's exact shape (§3 baseline): EFI mount AND LVM root — the walk and the
			// ESP must agree on the same disk (scenario C: output identical pre/post).
			name: "EFI + LVM root (felhom-pve)",
			mounts: []Mount{
				{Device: "/dev/mapper/pve-root", MountPoint: "/", FSType: "ext4"},
				{Device: "/dev/sda2", MountPoint: "/boot/efi", FSType: "vfat"},
			},
			slaves: map[string][]string{
				"pve-root": {"sda3"},
			},
			wantSystem: []string{"/dev/sda"},
			scratch:    "/dev/sdd",
		},
		{
			// Nested virtual layers: dm on md on partitions of two disks.
			name:   "nested dm-on-md",
			mounts: []Mount{{Device: "/dev/mapper/pve-root", MountPoint: "/", FSType: "ext4"}},
			slaves: map[string][]string{
				"pve-root": {"md0"},
				"md0":      {"sda2", "sdb2"},
			},
			wantSystem: []string{"/dev/sda", "/dev/sdb"},
			scratch:    "/dev/sdd",
		},
	}
}

// TestSystemDisks_WalkTopologies is the SIGNATURE test (scenario B): in every topology the
// walk resolves, the root-backing physical disk(s) are ALWAYS in the system set. This
// assertion may never be weakened.
func TestSystemDisks_WalkTopologies(t *testing.T) {
	for _, tc := range walkTopologies() {
		t.Run(tc.name, func(t *testing.T) {
			host := &fakeHostReader{mounts: tc.mounts, slaves: tc.slaves}
			set, ok := SystemDisks(host)
			if !ok {
				t.Fatalf("SystemDisks must resolve this topology, got ok=false (set=%v)", set)
			}
			for _, d := range tc.wantSystem {
				if !set[d] {
					t.Errorf("SIGNATURE VIOLATION: root-backing disk %s missing from system set %v", d, set)
				}
			}
			if set[tc.scratch] {
				t.Errorf("scratch disk %s wrongly in the system set %v", tc.scratch, set)
			}
			// And the classification consequences: the system disk is never user-data, the
			// scratch disk is never system.
			if RoleForRawDevice(tc.wantSystem[0], set, ok) != RoleSystem {
				t.Errorf("root-backing disk %s must classify system", tc.wantSystem[0])
			}
			if RoleForRawDevice(tc.scratch, set, ok) != RoleUserData {
				t.Errorf("scratch disk %s must classify user-data (wizard-eligible)", tc.scratch)
			}
		})
	}
}

// TestSystemDisks_LegacyBoot_WizardLives (scenario A): the drill-box shape resolves — the
// scratch disk is wizard-eligible instead of the pre-fix all-system dead end.
// RED-PROOF companion: with the pre-fix resolver (wholeDiskOf only, no walk) this fails on
// ok=false — the exact dead-wizard live shape from the IA report.
func TestSystemDisks_LegacyBoot_WizardLives(t *testing.T) {
	host := &fakeHostReader{
		mounts: []Mount{{Device: "/dev/mapper/pve-root", MountPoint: "/", FSType: "ext4"}},
		slaves: map[string][]string{"pve-root": {"sda3"}},
	}
	set, ok := SystemDisks(host)
	if !ok {
		t.Fatal("legacy-boot topology must resolve (the all-system fail-safe is the ERROR case, not the legacy-boot case)")
	}
	if !set["/dev/sda"] {
		t.Fatalf("root parent disk missing: %v", set)
	}
	if isSystemBacked("/dev/sdd", set, ok) {
		t.Fatal("hot-added scratch disk still classified system — the wizard stays dead")
	}
}

// TestSystemDisks_DanglingSlave_FailSafe (scenario D): an unresolvable slave fails the WHOLE
// walk and callers see the all-system behavior through the SAME code path as today
// (sysKnown=false → isSystemBacked true for everything).
// RED-PROOF companion: treating an unresolved slave as skippable makes ok=true here → the
// scratch disk classifies candidate while the walk is incomplete → this test fails.
func TestSystemDisks_DanglingSlave_FailSafe(t *testing.T) {
	host := &fakeHostReader{
		mounts: []Mount{{Device: "/dev/mapper/pve-root", MountPoint: "/", FSType: "ext4"}},
		slaves: map[string][]string{
			// One branch resolves (sda3 → sda), one is DANGLING (dm-9 has no /sys/block entry).
			// The resolvable branch is load-bearing for the red-proof: a "skip the unresolved
			// slave" mutation would yield a plausible non-empty set — exactly the partial
			// topology the conservatism rule forbids.
			"pve-root": {"sda3", "dm-9"},
		},
	}
	set, ok := SystemDisks(host)
	if ok {
		t.Fatalf("a dangling slave must fail the whole walk, got ok=true set=%v", set)
	}
	// The fail-safe path itself (not a lookalike): sysKnown=false forces system for EVERY
	// device, exactly as the pre-walk legacy behavior did.
	if !isSystemBacked("/dev/sdd", set, ok) {
		t.Fatal("fail-safe violated: scratch disk classified candidate while the walk is incomplete")
	}
	if RoleForRawDevice("/dev/sdd", set, ok) != RoleSystem {
		t.Fatal("fail-safe violated at role level")
	}
}

// TestSystemDisks_CycleGuard: a slaves cycle (corrupt sysfs / hostile fixture) terminates and
// fails safe instead of recursing forever.
func TestSystemDisks_CycleGuard(t *testing.T) {
	host := &fakeHostReader{
		mounts: []Mount{{Device: "/dev/mapper/pve-root", MountPoint: "/", FSType: "ext4"}},
		slaves: map[string][]string{
			"pve-root": {"dm-1"},
			"dm-1":     {"pve-root"},
		},
	}
	if _, ok := SystemDisks(host); ok {
		t.Fatal("a slaves cycle must fail safe (ok=false)")
	}
}

// TestSystemDisks_VirtualWithEmptySlaves: a virtual root whose slaves dir is EMPTY (nothing to
// ground on) fails safe — hasDir alone is not resolution.
func TestSystemDisks_VirtualWithEmptySlaves(t *testing.T) {
	host := &fakeHostReader{
		mounts: []Mount{{Device: "/dev/mapper/pve-root", MountPoint: "/", FSType: "ext4"}},
		slaves: map[string][]string{"pve-root": {}},
	}
	if _, ok := SystemDisks(host); ok {
		t.Fatal("virtual device with no slaves must fail safe")
	}
}