/*
 * SPDX-FileCopyrightText: Copyright (c) 2025-2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
 * SPDX-License-Identifier: Apache-2.0
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package validation

import (
	"context"
	"errors"
	"fmt"
	"strconv"
	"strings"

	nvidiacomv1alpha1 "github.com/ai-dynamo/dynamo/deploy/operator/api/v1alpha1"
	"github.com/ai-dynamo/dynamo/deploy/operator/internal/consts"
	controllercommon "github.com/ai-dynamo/dynamo/deploy/operator/internal/controller_common"
	"github.com/ai-dynamo/dynamo/deploy/operator/internal/dynamo/epp"
	ctrl "sigs.k8s.io/controller-runtime"
	"sigs.k8s.io/controller-runtime/pkg/webhook/admission"
)

// SharedSpecValidator validates DynamoComponentDeploymentSharedSpec fields.
// This validator is used by both DynamoComponentDeploymentValidator and DynamoGraphDeploymentValidator
// to provide consistent validation logic for shared spec fields.
type SharedSpecValidator struct {
	spec                *nvidiacomv1alpha1.DynamoComponentDeploymentSharedSpec
	fieldPath           string       // e.g., "spec" for DCD, "spec.services[foo]" for DGD
	calculatedNamespace string       // The namespace that will be used: {k8s_namespace}-{dgd_name}
	mgr                 ctrl.Manager // Optional: for API group detection via discovery client
}

// NewSharedSpecValidator creates a new validator for DynamoComponentDeploymentSharedSpec.
// fieldPath is used to provide context in error messages (e.g., "spec" or "spec.services[main]").
// calculatedNamespace is the namespace the operator will use:
//   - If GlobalDynamoNamespace is true: "dynamo" (global constant)
//   - Otherwise: {k8s_namespace}-{dgd_name}
func NewSharedSpecValidator(spec *nvidiacomv1alpha1.DynamoComponentDeploymentSharedSpec, fieldPath string, calculatedNamespace string) *SharedSpecValidator {
	return &SharedSpecValidator{
		spec:                spec,
		fieldPath:           fieldPath,
		calculatedNamespace: calculatedNamespace,
		mgr:                 nil,
	}
}

// NewSharedSpecValidatorWithManager creates a validator with a manager for API group detection.
// This allows the validator to check for API group availability (e.g., inference.networking.k8s.io) when validating EPP components.
func NewSharedSpecValidatorWithManager(spec *nvidiacomv1alpha1.DynamoComponentDeploymentSharedSpec, fieldPath string, calculatedNamespace string, mgr ctrl.Manager) *SharedSpecValidator {
	return &SharedSpecValidator{
		spec:                spec,
		fieldPath:           fieldPath,
		calculatedNamespace: calculatedNamespace,
		mgr:                 mgr,
	}
}

// Validate performs validation on the shared spec fields.
// Context is required for any operations that may need to query the cluster (e.g., CRD checks).
// Returns warnings (e.g., deprecation notices) and error if validation fails.
func (v *SharedSpecValidator) Validate(ctx context.Context) (admission.Warnings, error) {
	// Collect warnings (e.g., deprecation notices)
	var warnings admission.Warnings

	// Warn about deprecated dynamoNamespace field
	if v.spec.DynamoNamespace != nil && *v.spec.DynamoNamespace != "" {
		warnings = append(warnings, fmt.Sprintf(
			"%s.dynamoNamespace is deprecated and ignored. Value '%s' will be replaced with '%s'. "+
				"Remove this field from your configuration",
			v.fieldPath, *v.spec.DynamoNamespace, v.calculatedNamespace))
	}

	// Validate replicas if specified
	if v.spec.Replicas != nil && *v.spec.Replicas < 0 {
		return nil, fmt.Errorf("%s.replicas must be non-negative", v.fieldPath)
	}

	// Validate ingress configuration if enabled
	if v.spec.Ingress != nil && v.spec.Ingress.Enabled {
		if err := v.validateIngress(); err != nil {
			return nil, err
		}
	}

	// Validate volume mounts
	if err := v.validateVolumeMounts(); err != nil {
		return nil, err
	}

	// Validate shared memory
	if v.spec.SharedMemory != nil {
		if err := v.validateSharedMemory(); err != nil {
			return nil, err
		}
	}

	// Check for deprecated autoscaling field
	//nolint:staticcheck // SA1019: Intentionally checking deprecated field to warn users
	if v.spec.Autoscaling != nil {
		warnings = append(warnings, fmt.Sprintf(
			"%s.autoscaling is deprecated and ignored. Use DynamoGraphDeploymentScalingAdapter "+
				"with HPA, KEDA, or Planner for autoscaling instead. See docs/kubernetes/autoscaling.md",
			v.fieldPath))
	}

	// Validate frontend sidecar container name conflicts
	if err := v.validateFrontendSidecar(); err != nil {
		return nil, err
	}

	// Validate service-level annotations
	if err := v.validateServiceAnnotations(); err != nil {
		return nil, err
	}

	// Validate EPP-specific constraints
	if err := v.validateEPPConfig(ctx); err != nil {
		return nil, err
	}

	// Validate GPU memory service configuration (intra-pod GMS)
	if err := v.validateGPUMemoryService(); err != nil {
		return nil, err
	}

	// Validate GMS failover constraints
	if err := v.validateFailover(); err != nil {
		return nil, err
	}

	return warnings, nil
}

// validateIngress validates the ingress configuration.
func (v *SharedSpecValidator) validateIngress() error {
	if v.spec.Ingress.Host == "" {
		return fmt.Errorf("%s.ingress.host is required when ingress is enabled", v.fieldPath)
	}
	return nil
}

// validateVolumeMounts validates the volume mount configurations.
func (v *SharedSpecValidator) validateVolumeMounts() error {
	for i, volumeMount := range v.spec.VolumeMounts {
		if err := v.validateVolumeMount(i, &volumeMount); err != nil {
			return err
		}
	}
	return nil
}

// validateVolumeMount validates a single volume mount configuration.
func (v *SharedSpecValidator) validateVolumeMount(index int, volumeMount *nvidiacomv1alpha1.VolumeMount) error {
	// If useAsCompilationCache is false, mountPoint is required
	if !volumeMount.UseAsCompilationCache && volumeMount.MountPoint == "" {
		return fmt.Errorf("%s.volumeMounts[%d].mountPoint is required when useAsCompilationCache is false", v.fieldPath, index)
	}
	return nil
}

// validateSharedMemory validates the shared memory configuration.
func (v *SharedSpecValidator) validateSharedMemory() error {
	// If disabled is false (i.e., shared memory is enabled), size is required
	if !v.spec.SharedMemory.Disabled && v.spec.SharedMemory.Size.IsZero() {
		return fmt.Errorf("%s.sharedMemory.size is required when disabled is false", v.fieldPath)
	}
	return nil
}

// validateEPPConfig validates EPP-specific configuration constraints.
func (v *SharedSpecValidator) validateEPPConfig(ctx context.Context) error {
	// Only validate if this is an EPP component
	if v.spec.ComponentType != consts.ComponentTypeEPP {
		return nil
	}

	// Check if InferencePool API group is available in the cluster (if manager is provided)
	if v.mgr != nil {
		if err := v.checkInferencePoolAPIAvailability(ctx); err != nil {
			return fmt.Errorf("%s: cannot deploy EPP component: %w", v.fieldPath, err)
		}
	}

	// EPP must be single-node (cannot be multinode)
	if v.spec.IsMultinode() {
		return fmt.Errorf("%s: EPP component cannot be multinode (multinode field must be nil or nodeCount must be 1)", v.fieldPath)
	}

	// EPP should have exactly 1 replica (optional constraint - can be relaxed if needed)
	if v.spec.Replicas != nil && *v.spec.Replicas != 1 {
		return fmt.Errorf("%s: EPP component must have exactly 1 replica (found %d replicas)", v.fieldPath, *v.spec.Replicas)
	}

	// EPP components MUST have EPPConfig
	if v.spec.EPPConfig == nil {
		return fmt.Errorf("%s.eppConfig is required for EPP components", v.fieldPath)
	}

	// Either ConfigMapRef or Config must be specified (no default)
	if v.spec.EPPConfig.ConfigMapRef == nil && v.spec.EPPConfig.Config == nil {
		return fmt.Errorf("%s.eppConfig: either configMapRef or config must be specified (no default configuration provided)", v.fieldPath)
	}

	// ConfigMapRef and Config are mutually exclusive
	if v.spec.EPPConfig.ConfigMapRef != nil && v.spec.EPPConfig.Config != nil {
		return fmt.Errorf("%s.eppConfig: configMapRef and config are mutually exclusive, only one can be specified", v.fieldPath)
	}

	// If ConfigMapRef is provided, validate it
	if v.spec.EPPConfig.ConfigMapRef != nil {
		if v.spec.EPPConfig.ConfigMapRef.Name == "" {
			return fmt.Errorf("%s.eppConfig.configMapRef.name is required", v.fieldPath)
		}
	}

	return nil
}

// checkInferencePoolAPIAvailability checks if the inference.networking.k8s.io API group is available in the cluster.
// Returns an error if the API group is not available, which prevents EPP deployment.
// This reuses the controller_common.DetectInferencePoolAvailability function.
func (v *SharedSpecValidator) checkInferencePoolAPIAvailability(ctx context.Context) error {
	if v.mgr == nil {
		// No manager provided, skip the check (e.g., in controller without webhooks)
		return nil
	}

	if !controllercommon.DetectInferencePoolAvailability(ctx, v.mgr) {
		return fmt.Errorf(
			"InferencePool API group (%s) is not available in the cluster. "+
				"EPP requires the Gateway API Inference Extension to be installed. "+
				"Please install the Gateway API Inference Extension before deploying EPP components",
			epp.InferencePoolGroup)
	}

	return nil
}

// validateFrontendSidecar checks that extraPodSpec.containers does not already
// contain a container whose name collides with the auto-generated frontend sidecar.
func (v *SharedSpecValidator) validateFrontendSidecar() error {
	if v.spec.FrontendSidecar == nil {
		return nil
	}
	if v.spec.ExtraPodSpec == nil || v.spec.ExtraPodSpec.PodSpec == nil {
		return nil
	}
	for _, c := range v.spec.ExtraPodSpec.PodSpec.Containers {
		if c.Name == consts.FrontendSidecarContainerName {
			return fmt.Errorf(
				"%s: cannot inject frontend sidecar: a container named %q already exists in extraPodSpec.containers",
				v.fieldPath, consts.FrontendSidecarContainerName)
		}
	}
	return nil
}

// parseGPUCount extracts the GPU count from a Resources block, preferring
// Limits then Requests. Returns (0, nil) when no GPU is requested, or an
// error if the value is non-numeric.
func parseGPUCount(r *nvidiacomv1alpha1.Resources) (int, error) {
	gpuStr := ""
	switch {
	case r != nil && r.Limits != nil && r.Limits.GPU != "":
		gpuStr = r.Limits.GPU
	case r != nil && r.Requests != nil && r.Requests.GPU != "":
		gpuStr = r.Requests.GPU
	}
	if gpuStr == "" {
		return 0, nil
	}
	n, err := strconv.Atoi(gpuStr)
	if err != nil {
		return 0, fmt.Errorf("invalid value %q: %w", gpuStr, err)
	}
	return n, nil
}

// validateFailover validates GMS failover configuration constraints.
//
// The layout (intra-pod sidecar vs. inter-pod weight-server pod) is declared
// by gpuMemoryService.mode. failover is an independent toggle: when enabled,
// failover.mode MUST match gpuMemoryService.mode so the two knobs describe a
// consistent topology. It is also valid to configure gpuMemoryService without
// failover (no shadows; a single engine + GMS server pair) — see
// validateGPUMemoryService below.
func (v *SharedSpecValidator) validateFailover() error {
	if v.spec.Failover == nil || !v.spec.Failover.Enabled {
		// When failover.enabled is false the sub-fields (mode, numShadows)
		// are dormant configuration and the render path ignores them
		// (GetNumShadows returns 0). We deliberately do not validate them
		// here so users can stage a failover config before flipping
		// enabled=true — matching the K8s convention that fields on a
		// disabled feature are not constrained.
		return nil
	}

	var errs []error

	// For intra-pod mode: require gpuMemoryService.enabled and validate mode matching.
	if v.spec.Failover.Mode == nvidiacomv1alpha1.GMSModeIntraPod {
		if v.spec.GPUMemoryService == nil || !v.spec.GPUMemoryService.Enabled {
			errs = append(errs, fmt.Errorf(
				"%s.failover: intraPod failover requires gpuMemoryService.enabled to be true",
				v.fieldPath))
		} else if v.spec.GPUMemoryService.Mode != "" &&
			v.spec.GPUMemoryService.Mode != nvidiacomv1alpha1.GMSModeIntraPod {
			errs = append(errs, fmt.Errorf(
				"%s.failover: failover.mode %q must match gpuMemoryService.mode %q",
				v.fieldPath, v.spec.Failover.Mode, v.spec.GPUMemoryService.Mode))
		}

		// intraPod is a fixed 1 primary + 1 shadow sidecar layout; numShadows
		// is meaningless here and any value other than the implicit 1 is
		// almost certainly a configuration error (user probably wanted
		// mode=interPod).
		if v.spec.Failover.NumShadows != 0 && v.spec.Failover.NumShadows != 1 {
			errs = append(errs, fmt.Errorf(
				"%s.failover.numShadows=%d is invalid for mode=%q: intraPod uses a fixed 1 primary + 1 shadow sidecar; "+
					"use failover.mode=%q to configure numShadows",
				v.fieldPath, v.spec.Failover.NumShadows, nvidiacomv1alpha1.GMSModeIntraPod, nvidiacomv1alpha1.GMSModeInterPod))
		}
	}

	// For inter-pod mode: require the inter-pod GMS layout (gpuMemoryService
	// with mode=interPod) so failover hot-spares are added on top of an
	// already-declared weight-server pod layout.
	if v.spec.Failover.Mode == nvidiacomv1alpha1.GMSModeInterPod {
		if v.spec.GPUMemoryService == nil || !v.spec.GPUMemoryService.Enabled {
			errs = append(errs, fmt.Errorf(
				"%s.failover: interPod failover requires gpuMemoryService.enabled=true and gpuMemoryService.mode=%q",
				v.fieldPath, nvidiacomv1alpha1.GMSModeInterPod))
		} else if v.spec.GPUMemoryService.Mode != nvidiacomv1alpha1.GMSModeInterPod {
			// An unset gpuMemoryService.mode defaults to the intra-pod sidecar
			// layout, which is incompatible with inter-pod failover; the user
			// must set gpuMemoryService.mode=interPod explicitly.
			detected := string(v.spec.GPUMemoryService.Mode)
			if detected == "" {
				detected = "<unset>"
			}
			errs = append(errs, fmt.Errorf(
				"%s.failover: interPod failover requires gpuMemoryService.mode=%q (got %q)",
				v.fieldPath, nvidiacomv1alpha1.GMSModeInterPod, detected))
		}

		if v.spec.Failover.NumShadows < 1 {
			errs = append(errs, fmt.Errorf("%s.failover.numShadows must be >= 1", v.fieldPath))
		}

		gpuCount, err := parseGPUCount(v.spec.Resources)
		if err != nil {
			errs = append(errs, fmt.Errorf("%s.resources.limits.gpu: %w", v.fieldPath, err))
		} else if gpuCount < 1 {
			errs = append(errs, fmt.Errorf("%s: GMS failover requires at least 1 GPU in resources.limits.gpu", v.fieldPath))
		}

		switch v.spec.ComponentType {
		case consts.ComponentTypeEPP, consts.ComponentTypeFrontend, consts.ComponentTypePlanner:
			errs = append(errs, fmt.Errorf("%s: GMS failover is not supported for componentType %q", v.fieldPath, v.spec.ComponentType))
		}
	}

	return errors.Join(errs...)
}

// validateGPUMemoryService validates gpuMemoryService constraints.
//
// gpuMemoryService declares the GMS layout (intra-pod sidecar vs. inter-pod
// dedicated weight-server pod) and may be enabled independently of failover:
// the intra-pod layout gives the engine a GMS sidecar in the same pod, and
// the inter-pod layout gives it a dedicated weight-server pod paired with one
// engine pod. Failover adds shadow engine pods on top of the declared layout
// (see validateFailover); it is not the sole way to request the inter-pod
// layout.
func (v *SharedSpecValidator) validateGPUMemoryService() error {
	if v.spec.GPUMemoryService == nil || !v.spec.GPUMemoryService.Enabled {
		return nil
	}

	isWorker := v.spec.ComponentType == consts.ComponentTypeWorker ||
		v.spec.ComponentType == consts.ComponentTypePrefill ||
		v.spec.ComponentType == consts.ComponentTypeDecode
	if !isWorker {
		return fmt.Errorf(
			"%s.gpuMemoryService: GPU memory service is only supported for worker components (componentType must be worker, prefill, or decode)",
			v.fieldPath)
	}

	gpuCount, err := parseGPUCount(v.spec.Resources)
	if err != nil || gpuCount < 1 {
		return fmt.Errorf(
			"%s.gpuMemoryService: GPU memory service requires resources.limits.gpu >= 1",
			v.fieldPath)
	}

	return nil
}

// validateServiceAnnotations validates known annotations on the service-level spec.
func (v *SharedSpecValidator) validateServiceAnnotations() error {
	if v.spec.Annotations == nil {
		return nil
	}
	if value, exists := v.spec.Annotations[consts.KubeAnnotationVLLMDistributedExecutorBackend]; exists {
		switch strings.ToLower(value) {
		case "mp", "ray":
			// valid
		default:
			return fmt.Errorf("%s.annotations[%s] has invalid value %q: must be \"mp\" or \"ray\"",
				v.fieldPath, consts.KubeAnnotationVLLMDistributedExecutorBackend, value)
		}
	}
	return nil
}