/**
# Copyright (c) 2022, NVIDIA CORPORATION.  All rights reserved.
#
# 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 modifier

import (
	"fmt"
	"path/filepath"

	"github.com/NVIDIA/nvidia-container-toolkit/internal/config"
	"github.com/NVIDIA/nvidia-container-toolkit/internal/discover"
	"github.com/NVIDIA/nvidia-container-toolkit/internal/edits"
	"github.com/NVIDIA/nvidia-container-toolkit/internal/oci"
	"github.com/opencontainers/runtime-spec/specs-go"
	"github.com/sirupsen/logrus"
)

// experiemental represents the modifications required by the experimental runtime
type experimental struct {
	logger     *logrus.Logger
	discoverer discover.Discover
}

// NewExperimentalModifier creates a modifier that applied the experimental
// modications to an OCI spec if required by the runtime wrapper.
func NewExperimentalModifier(logger *logrus.Logger, cfg *config.RuntimeConfig) (oci.SpecModifier, error) {
	logger.Infof("Constructing modifier from config: %+v", cfg)

	// TODO: We need to specify the root
	root := ""

	var d discover.Discover
	switch cfg.DiscoverMode {
	case "legacy":
		legacyDiscoverer, err := discover.NewLegacyDiscoverer(logger, root)
		if err != nil {
			return nil, fmt.Errorf("failed to create legacy discoverer: %v", err)
		}
		d = legacyDiscoverer
	default:
		return nil, fmt.Errorf("invalid discover mode: %v", cfg.DiscoverMode)
	}

	return newExperimentalModifierFromDiscoverer(logger, d)
}

// newExperimentalModifierFromDiscoverer created a modifier that aplies the discovered
// modifications to an OCI spec if require by the runtime wrapper.
func newExperimentalModifierFromDiscoverer(logger *logrus.Logger, d discover.Discover) (oci.SpecModifier, error) {
	m := experimental{
		logger:     logger,
		discoverer: d,
	}
	return &m, nil
}

// Modify applies the required modifications to the incomming OCI spec. These modifications
// are applied in-place.
func (m experimental) Modify(spec *specs.Spec) error {
	err := m.assertSpecIsCompatible(spec)
	if err != nil {
		return fmt.Errorf("OCI specification cannot be modified: %v", err)
	}

	specEdits, err := edits.NewSpecEdits(m.logger, m.discoverer)
	if err != nil {
		return fmt.Errorf("failed to get required container edits: %v", err)
	}

	return specEdits.Modify(spec)
}

func (m experimental) assertSpecIsCompatible(spec *specs.Spec) error {
	if spec == nil {
		return nil
	}

	if spec.Hooks == nil {
		return nil
	}

	if hookPath := findStableHook(spec.Hooks.Prestart); hookPath != "" {
		return fmt.Errorf("spec already contains required 'prestart' hook: %v", hookPath)
	}

	return nil
}

// findStableHook checks the list of OCI hooks for the nvidia-container-runtime-hook
// or nvidia-container-toolkit hook. These are included, for example, by the non-experimental
// nvidia-container-runtime or docker when specifying the --gpus flag.
func findStableHook(hooks []specs.Hook) string {
	lookFor := map[string]bool{
		nvidiaContainerRuntimeHookExecuable: true,
		nvidiaContainerToolkitExecutable:    true,
	}

	for _, h := range hooks {
		base := filepath.Base(h.Path)
		if lookFor[base] {
			return h.Path
		}
	}

	return ""
}