package monitoring

import (
	"context"
	"fmt"
	"sync/atomic"
	"testing"
	"time"

	"github.com/rcourtman/pulse-go-rewrite/internal/models"
	"github.com/rcourtman/pulse-go-rewrite/pkg/proxmox"
)

type mockPVEClientSnapshots struct {
	mockPVEClientExtra
	snapshots    []proxmox.Snapshot
	vmSnapshots  map[int][]proxmox.Snapshot
	snapshotGate <-chan struct{}
	inflight     int64
	maxInflight  int64
}

func (m *mockPVEClientSnapshots) GetVMSnapshots(ctx context.Context, node string, vmid int) ([]proxmox.Snapshot, error) {
	if vmid == 999 {
		// simulate timeout/error
		return nil, fmt.Errorf("timeout")
	}
	m.trackSnapshotConcurrency(ctx)
	if m.vmSnapshots != nil {
		return m.vmSnapshots[vmid], nil
	}
	return m.snapshots, nil
}

func (m *mockPVEClientSnapshots) GetContainerSnapshots(ctx context.Context, node string, vmid int) ([]proxmox.Snapshot, error) {
	return m.snapshots, nil
}

func (m *mockPVEClientSnapshots) trackSnapshotConcurrency(ctx context.Context) {
	if m.snapshotGate == nil {
		return
	}
	current := atomic.AddInt64(&m.inflight, 1)
	for {
		max := atomic.LoadInt64(&m.maxInflight)
		if current <= max || atomic.CompareAndSwapInt64(&m.maxInflight, max, current) {
			break
		}
	}
	defer atomic.AddInt64(&m.inflight, -1)

	select {
	case <-m.snapshotGate:
	case <-ctx.Done():
	}
}

func TestMonitor_PollGuestSnapshots_Coverage(t *testing.T) {
	m := &Monitor{
		state: models.NewState(),
	}

	// 1. Setup State directly
	vms := []models.VM{
		{ID: "qemu/100", VMID: 100, Node: "node1", Instance: "pve1", Name: "vm100", Template: false},
		{ID: "qemu/101", VMID: 101, Node: "node1", Instance: "pve1", Name: "vm101-tmpl", Template: true}, // Should start skip
		{ID: "qemu/999", VMID: 999, Node: "node1", Instance: "pve1", Name: "vm999-fail", Template: false},
	}
	ct := []models.Container{
		{ID: "lxc/200", VMID: 200, Node: "node1", Instance: "pve1", Name: "ct200", Template: false},
	}
	m.state.UpdateVMsForInstance("pve1", vms)
	m.state.UpdateContainersForInstance("pve1", ct)

	// 2. Setup Client
	snaps := []proxmox.Snapshot{
		{Name: "snap1", SnapTime: 1234567890, Description: "test snap"},
	}
	client := &mockPVEClientSnapshots{
		snapshots: snaps,
	}

	// 3. Run
	ctx := context.Background()
	m.pollGuestSnapshots(ctx, "pve1", client)

	// 4. Verify
	// Check if snapshots are stored in State
	snapshot := m.state.GetSnapshot()
	found := false
	t.Logf("Found %d guest snapshots in state", len(snapshot.PVEBackups.GuestSnapshots))
	for _, gst := range snapshot.PVEBackups.GuestSnapshots {
		t.Logf("Snapshot: VMID=%d, Name=%s", gst.VMID, gst.Name)
		if gst.VMID == 100 && gst.Name == "snap1" {
			found = true
			if gst.Description != "test snap" {
				t.Errorf("Expected description 'test snap', got %s", gst.Description)
			}
		}
		if gst.VMID == 101 {
			t.Error("Should not have snapshots for template VM 101")
		}
	}
	if !found {
		t.Error("Expected snapshot 'snap1' for VM 100")
	}

	// 5. Test Context Deadline Exceeded Early Return
	shortCtx, cancel := context.WithTimeout(context.Background(), 1*time.Nanosecond)
	defer cancel()
	time.Sleep(1 * time.Millisecond) // Ensure it expired
	m.pollGuestSnapshots(shortCtx, "pve1", client)

	// Should log warn and return (no change to state, but coverage of check)
}

// TestMonitor_PollGuestSnapshots_PreservesPreviousOnPerVMError guards against
// #1437: when a per-VM snapshot fetch fails, the previously-known snapshots
// for that VM must be carried forward so they do not silently disappear.
// Successfully-polled VMs in the same cycle still get their fresh snapshots.
func TestMonitor_PollGuestSnapshots_PreservesPreviousOnPerVMError(t *testing.T) {
	m := &Monitor{state: models.NewState()}

	vms := []models.VM{
		{ID: "qemu/100", VMID: 100, Node: "node1", Instance: "pve1", Name: "vm100", Template: false},
		{ID: "qemu/999", VMID: 999, Node: "node1", Instance: "pve1", Name: "vm999-fail", Template: false},
	}
	m.state.UpdateVMsForInstance("pve1", vms)

	previous := []models.GuestSnapshot{
		{ID: "pve1-node1-100-snap_old", Name: "snap_old", Node: "node1", Instance: "pve1", Type: "qemu", VMID: 100, Time: time.Unix(1000, 0)},
		{ID: "pve1-node1-999-snap_persisted", Name: "snap_persisted", Node: "node1", Instance: "pve1", Type: "qemu", VMID: 999, Time: time.Unix(2000, 0)},
	}
	m.state.UpdateGuestSnapshotsForInstance("pve1", previous)

	client := &mockPVEClientSnapshots{
		snapshots: []proxmox.Snapshot{
			{Name: "snap_new", SnapTime: 3000, Description: "fresh"},
		},
	}

	m.pollGuestSnapshots(context.Background(), "pve1", client)

	got := m.state.GetSnapshot().PVEBackups.GuestSnapshots
	byName := make(map[string]models.GuestSnapshot, len(got))
	for _, snap := range got {
		byName[snap.Name] = snap
	}

	if _, oldStillThere := byName["snap_old"]; oldStillThere {
		t.Errorf("expected snap_old to be replaced by fresh poll, but it persisted")
	}
	if _, freshHere := byName["snap_new"]; !freshHere {
		t.Errorf("expected snap_new from fresh poll, got names=%v", keys(byName))
	}
	if _, persisted := byName["snap_persisted"]; !persisted {
		t.Errorf("expected snap_persisted to be carried forward after fetch failure, got names=%v", keys(byName))
	}
}

func TestMonitor_PollGuestSnapshots_PollsGuestsConcurrently(t *testing.T) {
	m := &Monitor{state: models.NewState()}

	const guestCount = 12
	vms := make([]models.VM, 0, guestCount)
	snapshotsByVMID := make(map[int][]proxmox.Snapshot, guestCount)
	for i := 0; i < guestCount; i++ {
		vmid := 100 + i
		vms = append(vms, models.VM{
			ID:       fmt.Sprintf("qemu/%d", vmid),
			VMID:     vmid,
			Node:     "node1",
			Instance: "pve1",
			Name:     fmt.Sprintf("vm%d", vmid),
		})
		snapshotsByVMID[vmid] = []proxmox.Snapshot{{
			Name:        fmt.Sprintf("snap-%d", vmid),
			SnapTime:    int64(3000 + i),
			Description: "fresh",
		}}
	}
	m.state.UpdateVMsForInstance("pve1", vms)

	gate := make(chan struct{})
	client := &mockPVEClientSnapshots{
		vmSnapshots:  snapshotsByVMID,
		snapshotGate: gate,
	}

	done := make(chan struct{})
	go func() {
		m.pollGuestSnapshots(context.Background(), "pve1", client)
		close(done)
	}()

	deadline := time.After(2 * time.Second)
	for atomic.LoadInt64(&client.maxInflight) < 2 {
		select {
		case <-deadline:
			close(gate)
			<-done
			t.Fatalf("guest snapshot polling did not start concurrent guest fetches; max inflight=%d", atomic.LoadInt64(&client.maxInflight))
		case <-done:
			t.Fatalf("guest snapshot polling completed before the gated snapshot fetches were released")
		default:
			time.Sleep(10 * time.Millisecond)
		}
	}

	close(gate)
	select {
	case <-done:
	case <-time.After(2 * time.Second):
		t.Fatal("guest snapshot polling did not finish after releasing concurrent fetches")
	}

	got := m.state.GetSnapshot().PVEBackups.GuestSnapshots
	if len(got) != guestCount {
		t.Fatalf("guest snapshots = %d, want %d: %+v", len(got), guestCount, got)
	}
}

func keys[K comparable, V any](m map[K]V) []K {
	out := make([]K, 0, len(m))
	for k := range m {
		out = append(out, k)
	}
	return out
}