package kvm2

import (
	"context"
	"errors"
	"fmt"
	"os"
	"path/filepath"
	"slices"
	"strings"
	"sync/atomic"
	"testing"
	"time"

	"github.com/digitalocean/go-libvirt"
	"github.com/go-logr/logr/funcr"
	"golang.org/x/crypto/ssh/knownhosts"
	logf "sigs.k8s.io/controller-runtime/pkg/log"

	"gitea.home.hrajfrisbee.cz/kacerr/egress-proxies-operator/internal/provider"
)

// checkContext is captureContext with a sink that tolerates the concurrent
// per-host log lines of Check.
func checkContext() (context.Context, *logCapture) {
	logs := &logCapture{}
	log := funcr.New(func(prefix, args string) {
		logs.mu.Lock()
		defer logs.mu.Unlock()
		logs.lines = append(logs.lines, prefix+" "+args)
	}, funcr.Options{Verbosity: 2})
	return logf.IntoContext(context.Background(), log), logs
}

// checkDialer hands out a distinct fake per host name, fails the hosts in
// errs, counts every dial, and, with block set, waits for ctx to end.
type checkDialer struct {
	backends map[string]*fakeBackend
	errs     map[string]error
	block    bool

	dials atomic.Int32
}

func (d *checkDialer) dial(ctx context.Context, host provider.KVMHost) (backend, error) {
	d.dials.Add(1)
	if d.block {
		<-ctx.Done()
		return nil, fmt.Errorf("%w: dialing %s: %w", provider.ErrTransient, host.Name, ctx.Err())
	}
	if err := d.errs[host.Name]; err != nil {
		return nil, err
	}
	b, ok := d.backends[host.Name]
	if !ok {
		return nil, fmt.Errorf("checkDialer: no backend for %s", host.Name)
	}
	return b, nil
}

func threeHosts() provider.KVMConfig {
	cfg := twoHosts()
	cfg.Hosts = append(cfg.Hosts, provider.KVMHost{Name: "lab3", Address: "lab3:22", User: "ops", Bridge: "br0", Pool: "ssd"})
	return cfg
}

func fakesFor(cfg provider.KVMConfig) map[string]*fakeBackend {
	out := make(map[string]*fakeBackend, len(cfg.Hosts))
	for _, h := range cfg.Hosts {
		f := newFakeBackend()
		f.hostname = h.Name + ".home.lan"
		if h.Pool != "" {
			f.pools[h.Pool] = newFakePool()
		}
		out[h.Name] = f
	}
	return out
}

func detailKeys(d map[string]string) []string {
	keys := make([]string, 0, len(d))
	for k := range d {
		keys = append(keys, k)
	}
	slices.Sort(keys)
	return keys
}

func TestCheck_oneEntryPerHostInConfigOrder(t *testing.T) {
	t.Parallel()
	cfg := threeHosts()
	d := &checkDialer{backends: fakesFor(cfg), errs: map[string]error{"lab2": errors.New("dial tcp 192.0.2.2:22: connect: no route to host")}}
	p := newProvider(testProvider, cfg, d)
	ctx, _ := checkContext()
	got := p.Check(ctx)
	if len(got) != len(cfg.Hosts) {
		t.Fatalf("Check() returned %d targets, want %d", len(got), len(cfg.Hosts))
	}
	for i, h := range cfg.Hosts {
		ts := got[i]
		if ts.Name != h.Name || ts.Address != h.Address {
			t.Errorf("target %d = %s (%s), want %s (%s)", i, ts.Name, ts.Address, h.Name, h.Address)
		}
		if ts.Name == "" || ts.Address == "" {
			t.Errorf("target %d has an empty name or address: %+v", i, ts)
		}
		wantReady := h.Name != "lab2"
		if ts.Ready != wantReady {
			t.Errorf("target %s ready = %v, want %v (%s: %s)", ts.Name, ts.Ready, wantReady, ts.Reason, ts.Message)
		}
	}
	if got[1].Reason != provider.ReasonUnreachable || got[0].Reason != provider.ReasonReachable {
		t.Errorf("reasons = %s, %s, %s", got[0].Reason, got[1].Reason, got[2].Reason)
	}
}

func TestCheck_hostsCheckedConcurrently(t *testing.T) {
	t.Parallel()
	cfg := twoHosts()
	fakes := fakesFor(cfg)
	for _, f := range fakes {
		release := f.blockOn("ConnectGetLibVersion")
		time.AfterFunc(200*time.Millisecond, func() { close(release) })
	}
	p := newProvider(testProvider, cfg, &checkDialer{backends: fakes})
	ctx, _ := checkContext()
	start := time.Now()
	got := p.Check(ctx)
	elapsed := time.Since(start)
	if elapsed > 350*time.Millisecond {
		t.Errorf("Check() took %v, want under 350ms for two 200ms hosts", elapsed)
	}
	for _, ts := range got {
		if !ts.Ready {
			t.Errorf("target %s not ready: %s: %s", ts.Name, ts.Reason, ts.Message)
		}
		if ts.Latency < 200*time.Millisecond {
			t.Errorf("target %s latency = %v, want at least the 200ms block", ts.Name, ts.Latency)
		}
	}
}

func TestCheck_expiredContextReturnsPromptly(t *testing.T) {
	t.Parallel()
	cfg := twoHosts()
	p := newProvider(testProvider, cfg, &checkDialer{block: true})
	ctx, _ := checkContext()
	ctx, cancel := context.WithCancel(ctx)
	cancel()
	start := time.Now()
	got := p.Check(ctx)
	if elapsed := time.Since(start); elapsed > time.Second {
		t.Errorf("Check() took %v with an expired ctx, want under 1s", elapsed)
	}
	if len(got) != len(cfg.Hosts) {
		t.Fatalf("Check() returned %d targets, want %d", len(got), len(cfg.Hosts))
	}
	for _, ts := range got {
		if ts.Ready || ts.Reason != provider.ReasonTimeout {
			t.Errorf("target %s = ready %v reason %s, want not ready, Timeout", ts.Name, ts.Ready, ts.Reason)
		}
		if ts.Message == "" {
			t.Errorf("target %s has no message", ts.Name)
		}
	}
}

// keyMaterial is the sentinel in the unusable key file of the credentials
// row; it must never reach a message.
const keyMaterial = "SENTINEL-PRIVATE-KEY-BYTES-9f3a"

func TestCheck_reasonsTable(t *testing.T) {
	t.Parallel()
	sshHandshake := func(cause error) error {
		return &dialError{stage: stageSSH, host: testHost, err: fmt.Errorf("ssh: handshake failed: %w", cause)}
	}
	tests := []struct {
		name string
		// dialErr builds the dial failure; nil means the dial succeeds.
		dialErr func(t *testing.T) error
		prep    func(f *fakeBackend)
		timeout time.Duration
		cancel  bool

		wantReady   bool
		wantReason  string
		wantMessage string
	}{
		{
			name: "credentials unusable",
			dialErr: func(t *testing.T) error {
				path := filepath.Join(t.TempDir(), "id_ed25519")
				if err := os.WriteFile(path, []byte(keyMaterial), 0o600); err != nil {
					t.Fatal(err)
				}
				_, err := loadCredentials(provider.KVMConfig{SSHKeyFile: path, KnownHostsFile: "/nonexistent/known_hosts"})
				if err == nil {
					t.Fatal("loadCredentials accepted the sentinel file")
				}
				return &dialError{stage: stageCredentials, host: testHost, err: err}
			},
			wantReason: reasonCredentialsUnavailable,
		},
		{
			name: "credentials missing",
			dialErr: func(*testing.T) error {
				_, err := loadCredentials(provider.KVMConfig{SSHKeyFile: "/nonexistent/kvm2/id_ed25519"})
				return &dialError{stage: stageCredentials, host: testHost, err: err}
			},
			wantReason: reasonCredentialsUnavailable,
		},
		{
			name: "tcp refused",
			dialErr: func(*testing.T) error {
				return &dialError{stage: stageTCP, host: testHost, err: errors.New("dial tcp 192.0.2.1:22: connect: connection refused")}
			},
			wantReason: provider.ReasonUnreachable,
		},
		{
			name: "tcp timed out",
			dialErr: func(*testing.T) error {
				return &dialError{stage: stageTCP, host: testHost, err: fmt.Errorf("dial tcp 192.0.2.1:22: %w", context.DeadlineExceeded)}
			},
			wantReason: provider.ReasonUnreachable,
		},
		{
			name:       "ssh host key unknown",
			dialErr:    func(*testing.T) error { return sshHandshake(&knownhosts.KeyError{}) },
			wantReason: provider.ReasonUnauthorized,
		},
		{
			name: "ssh host key mismatch",
			dialErr: func(*testing.T) error {
				return sshHandshake(&knownhosts.KeyError{Want: []knownhosts.KnownKey{{Filename: "known_hosts", Line: 3}}})
			},
			wantReason: provider.ReasonUnauthorized,
		},
		{
			name: "ssh authentication refused",
			dialErr: func(*testing.T) error {
				return sshHandshake(errors.New("ssh: unable to authenticate, attempted methods [none publickey], no supported methods remain"))
			},
			wantReason: provider.ReasonUnauthorized,
		},
		{
			name:       "ssh handshake reset",
			dialErr:    func(*testing.T) error { return sshHandshake(errors.New("read tcp: connection reset by peer")) },
			wantReason: provider.ReasonUnreachable,
		},
		{
			name:       "ssh handshake timed out",
			dialErr:    func(*testing.T) error { return sshHandshake(context.DeadlineExceeded) },
			wantReason: provider.ReasonUnreachable,
		},
		{
			name: "socket refused",
			dialErr: func(*testing.T) error {
				return &dialError{stage: stageSocket, host: testHost, err: errors.New("opening /var/run/libvirt/libvirt-sock: ssh: rejected: connect failed (No such file or directory)")}
			},
			wantReason:  provider.ReasonUnreachable,
			wantMessage: "/var/run/libvirt/libvirt-sock",
		},
		{
			name: "libvirt access denied",
			prep: func(f *fakeBackend) {
				f.failWith("ConnectGetLibVersion", fakeErr(libvirt.ErrAccessDenied, "access denied"))
			},
			wantReason: provider.ReasonForbidden,
		},
		{
			name: "libvirt auth failed",
			prep: func(f *fakeBackend) {
				f.failWith("ConnectGetHostname", fakeErr(libvirt.ErrAuthFailed, "authentication failed"))
			},
			wantReason: provider.ReasonForbidden,
		},
		{
			name: "pool not found",
			prep: func(f *fakeBackend) {
				f.mu.Lock()
				delete(f.pools, fakePoolName)
				f.mu.Unlock()
			},
			wantReason:  reasonPoolNotFound,
			wantMessage: fakePoolName,
		},
		{
			name: "other libvirt error",
			prep: func(f *fakeBackend) {
				f.failWith("StoragePoolGetInfo", fakeErr(libvirt.ErrInternalError, "internal error: pool info"))
			},
			wantReason: provider.ReasonAPIError,
		},
		{
			name:       "rpc outlives the deadline",
			prep:       func(f *fakeBackend) { f.blockOn("ConnectGetLibVersion") },
			timeout:    50 * time.Millisecond,
			wantReason: provider.ReasonTimeout,
		},
		{
			name:       "ctx cancelled mid check",
			prep:       func(f *fakeBackend) { f.blockOn("StoragePoolLookupByName") },
			cancel:     true,
			wantReason: provider.ReasonTimeout,
		},
		{
			name: "link killed mid check",
			prep: func(f *fakeBackend) {
				f.failWith("StoragePoolLookupByName", transientf("libvirt call StoragePoolLookupByName on beelink: connection closed while waiting: keepalive: EOF"))
			},
			wantReason: provider.ReasonUnreachable,
		},
		{
			name:        "pool inactive",
			prep:        func(f *fakeBackend) { f.pools[fakePoolName].state = libvirt.StoragePoolInactive },
			wantReason:  reasonPoolNotActive,
			wantMessage: `storage pool "default" is inactive`,
		},
		{
			name:       "ok",
			wantReady:  true,
			wantReason: provider.ReasonReachable,
		},
	}
	for _, tc := range tests {
		t.Run(tc.name, func(t *testing.T) {
			t.Parallel()
			cfg := twoHosts()
			cfg.Hosts = cfg.Hosts[:1]
			f := newFakeBackend()
			d := &checkDialer{backends: map[string]*fakeBackend{testHost: f}}
			if tc.dialErr != nil {
				d.errs = map[string]error{testHost: tc.dialErr(t)}
			}
			if tc.prep != nil {
				tc.prep(f)
			}
			p := newProvider(testProvider, cfg, d)
			ctx, _ := checkContext()
			switch {
			case tc.timeout > 0:
				var cancel context.CancelFunc
				ctx, cancel = context.WithTimeout(ctx, tc.timeout)
				defer cancel()
			case tc.cancel:
				var cancel context.CancelFunc
				ctx, cancel = context.WithCancel(ctx)
				time.AfterFunc(50*time.Millisecond, cancel)
			}
			got := p.Check(ctx)
			if len(got) != 1 {
				t.Fatalf("Check() returned %d targets, want 1", len(got))
			}
			ts := got[0]
			if ts.Ready != tc.wantReady || ts.Reason != tc.wantReason {
				t.Errorf("verdict = ready %v reason %s (%s), want ready %v reason %s", ts.Ready, ts.Reason, ts.Message, tc.wantReady, tc.wantReason)
			}
			if !tc.wantReady && ts.Message == "" {
				t.Error("failed check has no message")
			}
			if tc.wantReady && ts.Message != "" {
				t.Errorf("successful check has a message: %q", ts.Message)
			}
			if strings.Contains(ts.Message, keyMaterial) {
				t.Errorf("message leaks the key file content: %q", ts.Message)
			}
			if tc.wantMessage != "" && !strings.Contains(ts.Message, tc.wantMessage) {
				t.Errorf("message = %q, want it to contain %q", ts.Message, tc.wantMessage)
			}
			if ts.Details["user"] != "virt" || ts.Details["pool"] != "default" {
				t.Errorf("details = %v, want user and pool", ts.Details)
			}
			if tc.wantReady {
				want := map[string]string{
					"user": "virt", "pool": "default", "hostname": "fake-host", "libvirtVersion": "11.6.0",
					"poolState": "running", "poolCapacityGiB": "100.0", "poolAvailableGiB": "50.0",
				}
				for k, v := range want {
					if ts.Details[k] != v {
						t.Errorf("details[%s] = %q, want %q", k, ts.Details[k], v)
					}
				}
			}
		})
	}
}

func TestCheck_neverUsesPooledConnection(t *testing.T) {
	t.Parallel()
	cfg := threeHosts()
	fakes := fakesFor(cfg)
	d := &checkDialer{backends: fakes}
	p := newProvider(testProvider, cfg, d)
	ctx, _ := checkContext()
	got := p.Check(ctx)
	for _, ts := range got {
		if !ts.Ready {
			t.Errorf("target %s not ready: %s: %s", ts.Name, ts.Reason, ts.Message)
		}
	}
	if n := d.dials.Load(); int(n) != len(cfg.Hosts) {
		t.Errorf("dials = %d, want one fresh dial per host (%d)", n, len(cfg.Hosts))
	}
	p.hosts.mu.Lock()
	pooled := len(p.hosts.hosts)
	p.hosts.mu.Unlock()
	if pooled != 0 {
		t.Errorf("pooled table has %d entries after Check, want none", pooled)
	}
	for name, f := range fakes {
		if f.closeCount() != 1 {
			t.Errorf("fresh backend for %s closed %d times, want 1", name, f.closeCount())
		}
	}
}

func TestCheck_detailsKeys(t *testing.T) {
	t.Parallel()
	full := []string{"hostname", "libvirtVersion", "pool", "poolAvailableGiB", "poolCapacityGiB", "poolState", "user"}
	tests := []struct {
		name    string
		dialErr error
		prep    func(f *fakeBackend)
		want    []string
	}{
		{name: "success", want: full},
		{name: "pool not active", prep: func(f *fakeBackend) { f.pools[fakePoolName].state = libvirt.StoragePoolDegraded }, want: full},
		{
			name:    "dial failure",
			dialErr: &dialError{stage: stageTCP, host: testHost, err: errors.New("dial tcp: connection refused")},
			want:    []string{"pool", "user"},
		},
	}
	for _, tc := range tests {
		t.Run(tc.name, func(t *testing.T) {
			t.Parallel()
			cfg := twoHosts()
			cfg.Hosts = cfg.Hosts[:1]
			f := newFakeBackend()
			if tc.prep != nil {
				tc.prep(f)
			}
			d := &checkDialer{backends: map[string]*fakeBackend{testHost: f}}
			if tc.dialErr != nil {
				d.errs = map[string]error{testHost: tc.dialErr}
			}
			p := newProvider(testProvider, cfg, d)
			ctx, _ := checkContext()
			got := p.Check(ctx)[0]
			if keys := detailKeys(got.Details); !slices.Equal(keys, tc.want) {
				t.Errorf("details keys = %v, want %v", keys, tc.want)
			}
			for k, v := range got.Details {
				if v == "" {
					t.Errorf("details[%s] is empty", k)
				}
			}
		})
	}
}

func TestCheck_logsVerdictPerHost(t *testing.T) {
	t.Parallel()
	cfg := twoHosts()
	d := &checkDialer{backends: fakesFor(cfg), errs: map[string]error{"lab2": &dialError{stage: stageTCP, host: "lab2", err: errors.New("dial tcp: i/o timeout")}}}
	p := newProvider(testProvider, cfg, d)
	ctx, logs := checkContext()
	p.Check(ctx)
	checked := logs.matching("kvm2 host checked")
	if len(checked) != 2 {
		t.Fatalf("got %d verdict lines, want 2: %v", len(checked), checked)
	}
	for _, l := range checked {
		switch {
		case strings.Contains(l, `"host"="beelink"`):
			if !strings.Contains(l, `"ready"=true`) || !strings.Contains(l, `"reason"="Reachable"`) || !strings.Contains(l, `"latency"=`) {
				t.Errorf("beelink verdict line = %s", l)
			}
		case strings.Contains(l, `"host"="lab2"`):
			if !strings.Contains(l, `"ready"=false`) || !strings.Contains(l, `"reason"="Unreachable"`) {
				t.Errorf("lab2 verdict line = %s", l)
			}
		default:
			t.Errorf("verdict line without a host: %s", l)
		}
	}
}

func TestCheckReason_table(t *testing.T) {
	t.Parallel()
	dial := func(stage dialStage, cause error) error {
		return fmt.Errorf("wrapped: %w", &dialError{stage: stage, host: testHost, err: cause})
	}
	tests := []struct {
		name string
		err  error
		want string
	}{
		{name: "credentials stage", err: dial(stageCredentials, errors.New("reading ssh key file /k: no such file")), want: reasonCredentialsUnavailable},
		{name: "credentials stage even when permanent", err: dial(stageCredentials, permanentf("parsing ssh key file /k: ssh: no key found")), want: reasonCredentialsUnavailable},
		{name: "tcp stage", err: dial(stageTCP, errors.New("connect: connection refused")), want: provider.ReasonUnreachable},
		{name: "tcp stage with a deadline", err: dial(stageTCP, context.DeadlineExceeded), want: provider.ReasonUnreachable},
		{name: "ssh stage unknown host key", err: dial(stageSSH, &knownhosts.KeyError{}), want: provider.ReasonUnauthorized},
		{name: "ssh stage wrapped key error", err: dial(stageSSH, fmt.Errorf("ssh: handshake failed: %w", &knownhosts.KeyError{Want: []knownhosts.KnownKey{{}}})), want: provider.ReasonUnauthorized},
		{name: "ssh stage unable to authenticate", err: dial(stageSSH, errors.New("ssh: handshake failed: ssh: unable to authenticate, attempted methods [none publickey], no supported methods remain")), want: provider.ReasonUnauthorized},
		{name: "ssh stage reset", err: dial(stageSSH, errors.New("read tcp: connection reset by peer")), want: provider.ReasonUnreachable},
		{name: "ssh stage cancelled", err: dial(stageSSH, context.Canceled), want: provider.ReasonUnreachable},
		{name: "socket stage", err: dial(stageSocket, errors.New("opening /run/libvirt/libvirt-sock: ssh: rejected")), want: provider.ReasonUnreachable},
		{name: "deadline exceeded", err: fmt.Errorf("%w: libvirt call ConnectGetHostname on beelink exceeded its 30s budget: %w", provider.ErrTransient, context.DeadlineExceeded), want: provider.ReasonTimeout},
		{name: "cancelled", err: fmt.Errorf("%w: libvirt call ConnectGetHostname on beelink abandoned: %w", provider.ErrTransient, context.Canceled), want: provider.ReasonTimeout},
		{name: "access denied", err: fakeErr(libvirt.ErrAccessDenied, "access denied"), want: provider.ReasonForbidden},
		{name: "auth failed wrapped", err: fmt.Errorf("connecting to libvirt on host beelink: %w", fakeErr(libvirt.ErrAuthFailed, "authentication failed")), want: provider.ReasonForbidden},
		{name: "no storage pool", err: fakeErr(libvirt.ErrNoStoragePool, "Storage pool not found"), want: reasonPoolNotFound},
		{name: "other libvirt error", err: fakeErr(libvirt.ErrInternalError, "internal error"), want: provider.ReasonAPIError},
		{name: "link killed", err: transientf("libvirt call X on beelink: connection closed while waiting: keepalive: EOF"), want: provider.ReasonUnreachable},
		{name: "plain error", err: errors.New("unexpected EOF"), want: provider.ReasonUnreachable},
		{name: "nil", err: nil, want: provider.ReasonUnreachable},
	}
	for _, tc := range tests {
		t.Run(tc.name, func(t *testing.T) {
			t.Parallel()
			if got := checkReason(tc.err); got != tc.want {
				t.Errorf("checkReason(%v) = %s, want %s", tc.err, got, tc.want)
			}
		})
	}
}

func TestFormatLibVersion(t *testing.T) {
	t.Parallel()
	tests := []struct {
		in   uint64
		want string
	}{
		{0, "0.0.0"},
		{11006000, "11.6.0"},
		{10000003, "10.0.3"},
		{9010012, "9.10.12"},
		{100999999, "100.999.999"},
	}
	for _, tc := range tests {
		t.Run(tc.want, func(t *testing.T) {
			t.Parallel()
			if got := formatLibVersion(tc.in); got != tc.want {
				t.Errorf("formatLibVersion(%d) = %s, want %s", tc.in, got, tc.want)
			}
		})
	}
}

func TestPoolStateName(t *testing.T) {
	t.Parallel()
	tests := []struct {
		in   uint8
		want string
	}{
		{uint8(libvirt.StoragePoolInactive), "inactive"},
		{uint8(libvirt.StoragePoolBuilding), "building"},
		{uint8(libvirt.StoragePoolRunning), "running"},
		{uint8(libvirt.StoragePoolDegraded), "degraded"},
		{uint8(libvirt.StoragePoolInaccessible), "inaccessible"},
		{42, "state 42"},
	}
	for _, tc := range tests {
		t.Run(tc.want, func(t *testing.T) {
			t.Parallel()
			if got := poolStateName(tc.in); got != tc.want {
				t.Errorf("poolStateName(%d) = %s, want %s", tc.in, got, tc.want)
			}
		})
	}
}