package vmware

import (
	"bytes"
	"context"
	"crypto/tls"
	"crypto/x509"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"net"
	"net/http"
	"net/http/cookiejar"
	"net/url"
	"os"
	"strconv"
	"strings"
	"sync/atomic"
	"time"
)

const (
	// FeatureVMware allows explicit opt-out of the default-on VMware vCenter
	// platform integration.
	FeatureVMware              = "PULSE_ENABLE_VMWARE"
	defaultTimeout             = 10 * time.Second
	inventoryResponseLimitByte = 8 << 20
)

var supportedVIJSONReleases = []string{"9.0.0.0", "8.0.3", "8.0.2.0", "8.0.1.0"}

var featureVMwareEnabled atomic.Bool

func init() {
	featureVMwareEnabled.Store(parseFeatureEnabled(os.Getenv(FeatureVMware)))
}

// IsFeatureEnabled returns whether the VMware vCenter integration is enabled.
func IsFeatureEnabled() bool {
	return featureVMwareEnabled.Load()
}

// SetFeatureEnabled allows tests to control the feature flag.
func SetFeatureEnabled(enabled bool) {
	featureVMwareEnabled.Store(enabled)
}

// ResetFeatureEnabledFromEnv restores the feature flag from the current
// environment configuration.
func ResetFeatureEnabledFromEnv() {
	featureVMwareEnabled.Store(parseFeatureEnabled(os.Getenv(FeatureVMware)))
}

func parseFeatureEnabled(raw string) bool {
	switch strings.TrimSpace(strings.ToLower(raw)) {
	case "", "1", "true", "yes", "on":
		return true
	case "0", "false", "no", "off":
		return false
	default:
		return true
	}
}

// ConnectionError classifies VMware connection failures for API consumers.
type ConnectionError struct {
	Category string
	Message  string
}

func (e *ConnectionError) Error() string {
	if e == nil {
		return ""
	}
	return e.Message
}

// InventorySummary captures the minimum read-side floor proven by a successful
// VMware connection test.
type InventorySummary struct {
	Hosts      int
	VMs        int
	Datastores int
	Networks   int
	VIRelease  string
	Degraded   bool
	Issues     []InventoryEnrichmentIssue
}

// ClientConfig configures a VMware vCenter client.
type ClientConfig struct {
	Host               string
	Port               int
	Username           string
	Password           string
	InsecureSkipVerify bool
	Timeout            time.Duration
}

// Client executes phase-1 VMware connection validation.
type Client struct {
	baseURL    *url.URL
	httpClient *http.Client
	username   string
	password   string
	// tagCatalog memoizes CIS tag and category names across refreshes. The
	// poller keeps one client per vCenter connection, so the cache spans the
	// whole poll loop rather than one collection.
	tagCatalog vmwareTagCatalog
}

type viJSONServiceContentRefs struct {
	SessionManagerMoID string
	PerfManagerMoID    string
	EventManagerMoID   string
}

// NewClient constructs a VMware client from saved connection input.
func NewClient(cfg ClientConfig) (*Client, error) {
	baseURL, err := normalizeBaseURL(cfg.Host, cfg.Port)
	if err != nil {
		return nil, &ConnectionError{Category: "invalid_config", Message: err.Error()}
	}
	jar, err := cookiejar.New(nil)
	if err != nil {
		return nil, fmt.Errorf("create cookie jar: %w", err)
	}
	timeout := cfg.Timeout
	if timeout <= 0 {
		timeout = defaultTimeout
	}
	transport := &http.Transport{
		TLSClientConfig: &tls.Config{
			InsecureSkipVerify: cfg.InsecureSkipVerify, // operator-controlled onboarding setting
		},
	}
	return &Client{
		baseURL: baseURL,
		httpClient: &http.Client{
			Timeout:   timeout,
			Transport: transport,
			Jar:       jar,
		},
		username: strings.TrimSpace(cfg.Username),
		password: strings.TrimSpace(cfg.Password),
	}, nil
}

// Close releases idle resources held by the underlying HTTP client.
func (c *Client) Close() {
	if c == nil || c.httpClient == nil {
		return
	}
	if transport, ok := c.httpClient.Transport.(*http.Transport); ok {
		transport.CloseIdleConnections()
	}
}

// TestConnection validates both the Automation API and VI JSON API families and
// returns a minimal inventory summary on success.
func (c *Client) TestConnection(ctx context.Context) (*InventorySummary, error) {
	inventory, _, err := c.collectInventoryBaseWithSession(ctx)
	if err != nil {
		return nil, err
	}
	release, refs, err := c.resolveVIJSONRelease(ctx)
	if err != nil {
		return nil, err
	}
	sessionID, err := c.loginVIJSON(ctx, release, refs.SessionManagerMoID)
	if err != nil {
		return nil, err
	}
	perfCounters, err := c.loadPerfCounterCatalog(ctx, release, sessionID, refs.PerfManagerMoID)
	if err != nil {
		return nil, err
	}
	issues, err := c.validateSignalFloor(ctx, release, sessionID, refs.PerfManagerMoID, refs.EventManagerMoID, inventory, perfCounters)
	if err != nil {
		return nil, err
	}
	return &InventorySummary{
		Hosts:      len(inventory.Hosts),
		VMs:        len(inventory.VMs),
		Datastores: len(inventory.Datastores),
		Networks:   len(inventory.Networks),
		VIRelease:  release,
		Degraded:   len(issues) > 0,
		Issues:     issues,
	}, nil
}

// CollectInventory fetches the phase-1 VMware inventory floor used by the
// supplemental-ingest provider.
func (c *Client) CollectInventory(ctx context.Context) (*InventorySnapshot, error) {
	inventory, automationSessionID, err := c.collectInventoryBaseWithSession(ctx)
	if err != nil {
		return nil, err
	}
	release, refs, err := c.resolveVIJSONRelease(ctx)
	if err != nil {
		return nil, err
	}
	sessionID, err := c.loginVIJSON(ctx, release, refs.SessionManagerMoID)
	if err != nil {
		return nil, err
	}
	perfCounters, err := c.loadPerfCounterCatalog(ctx, release, sessionID, refs.PerfManagerMoID)
	if err != nil {
		return nil, err
	}
	signalIssues, err := c.enrichInventorySnapshot(ctx, automationSessionID, release, sessionID, refs.PerfManagerMoID, refs.EventManagerMoID, perfCounters, inventory)
	if err != nil {
		return nil, err
	}
	topologyIssues, err := c.enrichInventoryTopology(ctx, automationSessionID, release, sessionID, inventory)
	if err != nil {
		return nil, err
	}
	tagIssues, err := c.enrichInventoryTags(ctx, automationSessionID, inventory)
	if err != nil {
		return nil, err
	}
	inventory.VIRelease = strings.TrimSpace(release)
	inventory.CollectedAt = time.Now().UTC()
	inventory.EnrichmentIssues = append(inventory.EnrichmentIssues, signalIssues...)
	inventory.EnrichmentIssues = append(inventory.EnrichmentIssues, topologyIssues...)
	inventory.EnrichmentIssues = append(inventory.EnrichmentIssues, tagIssues...)
	return inventory, nil
}

func (c *Client) collectInventoryBaseWithSession(ctx context.Context) (*InventorySnapshot, string, error) {
	automationSessionID, err := c.createAutomationSession(ctx)
	if err != nil {
		return nil, "", err
	}

	var hosts []InventoryHost
	if err := c.listAutomationResources(ctx, automationSessionID, "/api/vcenter/host", "host inventory", &hosts); err != nil {
		return nil, "", err
	}

	var vms []InventoryVM
	if err := c.listAutomationResources(ctx, automationSessionID, "/api/vcenter/vm", "vm inventory", &vms); err != nil {
		return nil, "", err
	}

	var datastores []InventoryDatastore
	if err := c.listAutomationResources(ctx, automationSessionID, "/api/vcenter/datastore", "datastore inventory", &datastores); err != nil {
		return nil, "", err
	}

	var networks []InventoryNetwork
	if err := c.listAutomationResources(ctx, automationSessionID, "/api/vcenter/network", "network inventory", &networks); err != nil {
		return nil, "", err
	}

	return &InventorySnapshot{
		Hosts:      hosts,
		VMs:        vms,
		Datastores: datastores,
		Networks:   networks,
	}, automationSessionID, nil
}

func normalizeBaseURL(rawHost string, port int) (*url.URL, error) {
	host := strings.TrimSpace(rawHost)
	if host == "" {
		return nil, fmt.Errorf("vmware vcenter host is required")
	}
	if !strings.Contains(host, "://") {
		host = "https://" + host
	}
	parsed, err := url.Parse(host)
	if err != nil {
		return nil, fmt.Errorf("invalid vmware vcenter host: %w", err)
	}
	if parsed.Scheme != "https" {
		return nil, fmt.Errorf("vmware vcenter connections must use https")
	}
	if parsed.Host == "" {
		return nil, fmt.Errorf("vmware vcenter host is required")
	}
	if parsed.Path != "" && parsed.Path != "/" {
		return nil, fmt.Errorf("vmware vcenter host must not include a path")
	}
	if parsed.RawQuery != "" || parsed.Fragment != "" {
		return nil, fmt.Errorf("vmware vcenter host must not include query or fragment data")
	}
	if parsed.Port() == "" {
		if port <= 0 {
			port = 443
		}
		parsed.Host = net.JoinHostPort(parsed.Hostname(), strconv.Itoa(port))
	}
	parsed.Path = ""
	return parsed, nil
}

func (c *Client) createAutomationSession(ctx context.Context) (string, error) {
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, c.baseURL.String()+"/api/session", nil)
	if err != nil {
		return "", fmt.Errorf("build automation session request: %w", err)
	}
	req.SetBasicAuth(c.username, c.password)
	req.Header.Set("Accept", "application/json")
	resp, err := c.httpClient.Do(req)
	if err != nil {
		return "", classifyTransportError("automation session", err)
	}
	defer resp.Body.Close()
	body, readErr := io.ReadAll(io.LimitReader(resp.Body, 1<<20))
	if readErr != nil {
		return "", fmt.Errorf("read automation session response: %w", readErr)
	}
	switch resp.StatusCode {
	case http.StatusOK, http.StatusCreated:
	default:
		if resp.StatusCode == http.StatusUnauthorized || resp.StatusCode == http.StatusForbidden {
			return "", &ConnectionError{Category: "auth", Message: "VMware authentication failed while creating the Automation API session"}
		}
		if c.legacyCISSessionWorks(ctx) {
			return "", &ConnectionError{
				Category: "unsupported_version",
				Message:  "This vCenter only answers the legacy /rest CIS API, which predates the JSON APIs Pulse uses. Pulse supports vCenter 8.0U1 and newer.",
			}
		}
		return "", &ConnectionError{
			Category: "endpoint",
			Message:  fmt.Sprintf("VMware Automation API session request failed with HTTP %d", resp.StatusCode),
		}
	}
	var sessionID string
	if err := json.Unmarshal(body, &sessionID); err != nil || strings.TrimSpace(sessionID) == "" {
		return "", &ConnectionError{Category: "endpoint", Message: "VMware Automation API returned an invalid session payload"}
	}
	return strings.TrimSpace(sessionID), nil
}

func (c *Client) listAutomationResources(
	ctx context.Context,
	sessionID string,
	path string,
	label string,
	target any,
) error {
	return c.getAutomationJSON(ctx, sessionID, path, label, target)
}

// legacyCISSessionWorks probes the pre-7.0 CIS REST session endpoint after an
// /api/session failure. vSphere 6.x releases (EOL) only expose the legacy
// /rest API, so a successful legacy login with the same credentials means the
// target is an old release rather than a broken endpoint. The probe session is
// deleted best-effort so it does not count against vCenter session limits.
func (c *Client) legacyCISSessionWorks(ctx context.Context) bool {
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, c.baseURL.String()+"/rest/com/vmware/cis/session", nil)
	if err != nil {
		return false
	}
	req.SetBasicAuth(c.username, c.password)
	req.Header.Set("Accept", "application/json")
	resp, err := c.httpClient.Do(req)
	if err != nil {
		return false
	}
	body, _ := io.ReadAll(io.LimitReader(resp.Body, 1<<20))
	resp.Body.Close()
	if resp.StatusCode != http.StatusOK && resp.StatusCode != http.StatusCreated {
		return false
	}
	var payload struct {
		Value string `json:"value"`
	}
	if err := json.Unmarshal(body, &payload); err == nil && strings.TrimSpace(payload.Value) != "" {
		if delReq, delErr := http.NewRequestWithContext(ctx, http.MethodDelete, c.baseURL.String()+"/rest/com/vmware/cis/session", nil); delErr == nil {
			delReq.Header.Set("vmware-api-session-id", strings.TrimSpace(payload.Value))
			if delResp, doErr := c.httpClient.Do(delReq); doErr == nil {
				delResp.Body.Close()
			}
		}
	}
	return true
}

// getSessionScopedJSON fetches a session-authenticated vCenter JSON endpoint
// (shared by the Automation API and VI/JSON API paths) into target with the
// inventory response size cap and shared error classification.
func (c *Client) getSessionScopedJSON(
	ctx context.Context,
	sessionID string,
	path string,
	label string,
	target any,
) error {
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, c.baseURL.String()+path, nil)
	if err != nil {
		return fmt.Errorf("build %s request: %w", label, err)
	}
	req.Header.Set("Accept", "application/json")
	req.Header.Set("vmware-api-session-id", sessionID)
	resp, err := c.httpClient.Do(req)
	if err != nil {
		return classifyTransportError(label, err)
	}
	defer resp.Body.Close()
	body, readErr := io.ReadAll(io.LimitReader(resp.Body, inventoryResponseLimitByte))
	if readErr != nil {
		return fmt.Errorf("read %s response: %w", label, readErr)
	}
	switch resp.StatusCode {
	case http.StatusOK:
	default:
		return classifyReadStatusCode(label, resp.StatusCode)
	}
	if err := json.Unmarshal(body, target); err != nil {
		return &ConnectionError{Category: "endpoint", Message: fmt.Sprintf("VMware %s response was not valid JSON", label)}
	}
	return nil
}

// postSessionScopedJSON posts a JSON body to a session-authenticated vCenter
// endpoint and decodes the response into target. The vSphere Automation API
// models several reads as POST actions — CIS tag association lookups are the
// current case — so they cannot go through getSessionScopedJSON.
func (c *Client) postSessionScopedJSON(
	ctx context.Context,
	sessionID string,
	path string,
	label string,
	payload any,
	target any,
) error {
	body, err := json.Marshal(payload)
	if err != nil {
		return fmt.Errorf("marshal %s request: %w", label, err)
	}
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, c.baseURL.String()+path, bytes.NewReader(body))
	if err != nil {
		return fmt.Errorf("build %s request: %w", label, err)
	}
	req.Header.Set("Accept", "application/json")
	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("vmware-api-session-id", sessionID)
	resp, err := c.httpClient.Do(req)
	if err != nil {
		return classifyTransportError(label, err)
	}
	defer resp.Body.Close()
	responseBody, readErr := io.ReadAll(io.LimitReader(resp.Body, inventoryResponseLimitByte))
	if readErr != nil {
		return fmt.Errorf("read %s response: %w", label, readErr)
	}
	if resp.StatusCode != http.StatusOK {
		return classifyReadStatusCode(label, resp.StatusCode)
	}
	if err := json.Unmarshal(responseBody, target); err != nil {
		return &ConnectionError{Category: "endpoint", Message: fmt.Sprintf("VMware %s response was not valid JSON", label)}
	}
	return nil
}

func (c *Client) getAutomationJSON(
	ctx context.Context,
	sessionID string,
	path string,
	label string,
	target any,
) error {
	return c.getSessionScopedJSON(ctx, sessionID, path, label, target)
}

func (c *Client) resolveVIJSONRelease(ctx context.Context) (string, viJSONServiceContentRefs, error) {
	var lastErr error
	for _, release := range supportedVIJSONReleases {
		refs, err := c.fetchVIJSONServiceContentRefs(ctx, release)
		if err == nil {
			return release, refs, nil
		}
		lastErr = err
		if !isVIJSONReleaseProbeRetryable(err) {
			return "", viJSONServiceContentRefs{}, err
		}
	}
	if lastErr != nil && isVIJSONNotFound(lastErr) {
		return "", viJSONServiceContentRefs{}, &ConnectionError{
			Category: "unsupported_version",
			Message: fmt.Sprintf(
				"VMware vCenter version is outside the implemented VI JSON probe floor; Pulse currently probes %s",
				strings.Join(supportedVIJSONReleases, ", "),
			),
		}
	}
	if lastErr != nil {
		return "", viJSONServiceContentRefs{}, lastErr
	}
	return "", viJSONServiceContentRefs{}, &ConnectionError{
		Category: "unsupported_version",
		Message: fmt.Sprintf(
			"VMware vCenter version is outside the implemented VI JSON probe floor; Pulse currently probes %s",
			strings.Join(supportedVIJSONReleases, ", "),
		),
	}
}

// isVIJSONReleaseProbeRetryable reports whether a failed service-content probe
// for one vim25 release string should fall through to the next release in the
// list. vCenter answers a newer-than-supported release path with 404 on some
// builds and HTTP 500 on others (8.0.x returns 500 for the 9.0.0.0 path), so
// both "not_found" and generic endpoint failures continue the negotiation.
// Auth, permission, TLS, and network errors abort: they will not change with a
// different release string.
func isVIJSONReleaseProbeRetryable(err error) bool {
	connectionErr, ok := err.(*ConnectionError)
	if !ok {
		return false
	}
	switch connectionErr.Category {
	case "not_found", "endpoint":
		return true
	default:
		return false
	}
}

func (c *Client) fetchVIJSONServiceContentRefs(ctx context.Context, release string) (viJSONServiceContentRefs, error) {
	endpoint := fmt.Sprintf("%s/sdk/vim25/%s/ServiceInstance/ServiceInstance/content", c.baseURL.String(), release)
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, endpoint, nil)
	if err != nil {
		return viJSONServiceContentRefs{}, fmt.Errorf("build vi-json service instance request: %w", err)
	}
	req.Header.Set("Accept", "application/json")
	resp, err := c.httpClient.Do(req)
	if err != nil {
		return viJSONServiceContentRefs{}, classifyTransportError("vi-json service content", err)
	}
	defer resp.Body.Close()
	body, readErr := io.ReadAll(io.LimitReader(resp.Body, 1<<20))
	if readErr != nil {
		return viJSONServiceContentRefs{}, fmt.Errorf("read vi-json service content response: %w", readErr)
	}
	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
		return viJSONServiceContentRefs{}, classifyReadStatusCode("vi-json service content", resp.StatusCode)
	}
	var payload struct {
		SessionManager viJSONReference `json:"sessionManager"`
		PerfManager    viJSONReference `json:"perfManager"`
		EventManager   viJSONReference `json:"eventManager"`
	}
	if err := json.Unmarshal(body, &payload); err != nil {
		return viJSONServiceContentRefs{}, &ConnectionError{Category: "endpoint", Message: "VMware VI JSON API service-instance response was not valid JSON"}
	}
	refs := viJSONServiceContentRefs{
		SessionManagerMoID: strings.TrimSpace(payload.SessionManager.Value),
		PerfManagerMoID:    strings.TrimSpace(payload.PerfManager.Value),
		EventManagerMoID:   strings.TrimSpace(payload.EventManager.Value),
	}
	if refs.SessionManagerMoID == "" {
		return viJSONServiceContentRefs{}, &ConnectionError{Category: "endpoint", Message: "VMware VI JSON API service-instance response did not include a session manager reference"}
	}
	if refs.PerfManagerMoID == "" {
		return viJSONServiceContentRefs{}, &ConnectionError{Category: "endpoint", Message: "VMware VI JSON API service-instance response did not include a performance manager reference"}
	}
	if refs.EventManagerMoID == "" {
		return viJSONServiceContentRefs{}, &ConnectionError{Category: "endpoint", Message: "VMware VI JSON API service-instance response did not include an event manager reference"}
	}
	return refs, nil
}

func (c *Client) loginVIJSON(ctx context.Context, release string, sessionManagerMoID string) (string, error) {
	body, err := json.Marshal(map[string]string{
		"userName": c.username,
		"password": c.password,
	})
	if err != nil {
		return "", fmt.Errorf("marshal vi-json login request: %w", err)
	}
	endpoint := fmt.Sprintf("%s/sdk/vim25/%s/SessionManager/%s/Login", c.baseURL.String(), release, sessionManagerMoID)
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, endpoint, strings.NewReader(string(body)))
	if err != nil {
		return "", fmt.Errorf("build vi-json login request: %w", err)
	}
	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("Accept", "application/json")
	resp, err := c.httpClient.Do(req)
	if err != nil {
		return "", classifyTransportError("vi-json login", err)
	}
	defer resp.Body.Close()
	_, _ = io.Copy(io.Discard, io.LimitReader(resp.Body, 1<<20))
	switch resp.StatusCode {
	case http.StatusOK:
		sessionID := strings.TrimSpace(resp.Header.Get("vmware-api-session-id"))
		if sessionID == "" {
			return "", &ConnectionError{Category: "endpoint", Message: "VMware VI JSON API login succeeded without returning a session id"}
		}
		return sessionID, nil
	case http.StatusUnauthorized, http.StatusForbidden:
		return "", &ConnectionError{Category: "auth", Message: "VMware authentication failed while creating the VI JSON API session"}
	case http.StatusServiceUnavailable:
		return "", &ConnectionError{Category: "unavailable", Message: "VMware VI JSON API login is temporarily unavailable"}
	default:
		return "", &ConnectionError{Category: "endpoint", Message: fmt.Sprintf("VMware VI JSON API login failed with HTTP %d", resp.StatusCode)}
	}
}

func classifyReadStatusCode(label string, statusCode int) error {
	switch statusCode {
	case http.StatusUnauthorized:
		return &ConnectionError{Category: "auth", Message: fmt.Sprintf("VMware authentication failed while reading %s", label)}
	case http.StatusForbidden:
		return &ConnectionError{Category: "permission", Message: fmt.Sprintf("VMware permissions are insufficient for %s", label)}
	case http.StatusNotFound:
		return &ConnectionError{Category: "not_found", Message: fmt.Sprintf("VMware %s endpoint is unavailable", label)}
	case http.StatusServiceUnavailable:
		return &ConnectionError{Category: "unavailable", Message: fmt.Sprintf("VMware %s is temporarily unavailable", label)}
	default:
		return &ConnectionError{Category: "endpoint", Message: fmt.Sprintf("VMware %s request failed with HTTP %d", label, statusCode)}
	}
}

func classifyTransportError(stage string, err error) error {
	if err == nil {
		return nil
	}
	lower := strings.ToLower(err.Error())
	if strings.Contains(lower, "x509") || strings.Contains(lower, "certificate") || strings.Contains(lower, "tls") {
		return &ConnectionError{Category: "tls", Message: fmt.Sprintf("VMware TLS validation failed during %s", stage)}
	}
	var unknownAuthority *x509.UnknownAuthorityError
	if errors.As(err, &unknownAuthority) {
		return &ConnectionError{Category: "tls", Message: fmt.Sprintf("VMware TLS validation failed during %s", stage)}
	}
	var netErr net.Error
	if errors.As(err, &netErr) {
		return &ConnectionError{Category: "network", Message: fmt.Sprintf("VMware network error during %s", stage)}
	}
	return &ConnectionError{Category: "network", Message: fmt.Sprintf("VMware connection failed during %s", stage)}
}