/**
# 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"

	"tags.cncf.io/container-device-interface/pkg/parser"

	"github.com/NVIDIA/nvidia-container-toolkit/internal/config"
	"github.com/NVIDIA/nvidia-container-toolkit/internal/config/image"
	"github.com/NVIDIA/nvidia-container-toolkit/internal/logger"
	"github.com/NVIDIA/nvidia-container-toolkit/internal/modifier/cdi"
	"github.com/NVIDIA/nvidia-container-toolkit/internal/oci"
	"github.com/NVIDIA/nvidia-container-toolkit/pkg/nvcdi"
	"github.com/NVIDIA/nvidia-container-toolkit/pkg/nvcdi/spec"
)

// NewCDIModifier creates an OCI spec modifier that determines the modifications to make based on the
// CDI specifications available on the system. The NVIDIA_VISIBLE_DEVICES environment variable is
// used to select the devices to include.
func NewCDIModifier(logger logger.Interface, cfg *config.Config, image image.CUDA) (oci.SpecModifier, error) {
	deviceRequestor := newCDIDeviceRequestor(
		logger,
		image,
		cfg.NVIDIAContainerRuntimeConfig.Modes.CDI.DefaultKind,
	)
	devices := deviceRequestor.DeviceRequests()
	if len(devices) == 0 {
		logger.Debugf("No devices requested; no modification required.")
		return nil, nil
	}
	logger.Debugf("Creating CDI modifier for devices: %v", devices)

	automaticDevices := filterAutomaticDevices(devices)
	if len(automaticDevices) != len(devices) && len(automaticDevices) > 0 {
		return nil, fmt.Errorf("requesting a CDI device with vendor 'runtime.nvidia.com' is not supported when requesting other CDI devices")
	}
	if len(automaticDevices) > 0 {
		automaticModifier, err := newAutomaticCDISpecModifier(logger, cfg, automaticDevices)
		if err == nil {
			return automaticModifier, nil
		}
		logger.Warningf("Failed to create the automatic CDI modifier: %w", err)
		logger.Debugf("Falling back to the standard CDI modifier")
	}

	return cdi.New(
		cdi.WithLogger(logger),
		cdi.WithDevices(devices...),
		cdi.WithSpecDirs(cfg.NVIDIAContainerRuntimeConfig.Modes.CDI.SpecDirs...),
	)
}

type deviceRequestor interface {
	DeviceRequests() []string
}

type cdiDeviceRequestor struct {
	image       image.CUDA
	logger      logger.Interface
	defaultKind string
}

func newCDIDeviceRequestor(logger logger.Interface, image image.CUDA, defaultKind string) deviceRequestor {
	c := &cdiDeviceRequestor{
		logger:      logger,
		image:       image,
		defaultKind: defaultKind,
	}
	return withUniqueDevices(c)
}

func (c *cdiDeviceRequestor) DeviceRequests() []string {
	if c == nil {
		return nil
	}
	var devices []string
	for _, name := range c.image.VisibleDevices() {
		if !parser.IsQualifiedName(name) {
			name = fmt.Sprintf("%s=%s", c.defaultKind, name)
		}
		devices = append(devices, name)
	}

	return devices
}

// filterAutomaticDevices searches for "automatic" device names in the input slice.
// "Automatic" devices are a well-defined list of CDI device names which, when requested,
// trigger the generation of a CDI spec at runtime. This removes the need to generate a
// CDI spec on the system a-priori as well as keep it up-to-date.
func filterAutomaticDevices(devices []string) []string {
	var automatic []string
	for _, device := range devices {
		vendor, class, _ := parser.ParseDevice(device)
		if vendor == "runtime.nvidia.com" && class == "gpu" {
			automatic = append(automatic, device)
		}
	}
	return automatic
}

func newAutomaticCDISpecModifier(logger logger.Interface, cfg *config.Config, devices []string) (oci.SpecModifier, error) {
	logger.Debugf("Generating in-memory CDI specs for devices %v", devices)
	spec, err := generateAutomaticCDISpec(logger, cfg, devices)
	if err != nil {
		return nil, fmt.Errorf("failed to generate CDI spec: %w", err)
	}
	cdiDeviceRequestor, err := cdi.New(
		cdi.WithLogger(logger),
		cdi.WithSpec(spec.Raw()),
	)
	if err != nil {
		return nil, fmt.Errorf("failed to construct CDI modifier: %w", err)
	}

	return cdiDeviceRequestor, nil
}

func generateAutomaticCDISpec(logger logger.Interface, cfg *config.Config, devices []string) (spec.Interface, error) {
	cdilib, err := nvcdi.New(
		nvcdi.WithLogger(logger),
		nvcdi.WithNVIDIACDIHookPath(cfg.NVIDIACTKConfig.Path),
		nvcdi.WithDriverRoot(cfg.NVIDIAContainerCLIConfig.Root),
		nvcdi.WithVendor("runtime.nvidia.com"),
		nvcdi.WithClass("gpu"),
	)
	if err != nil {
		return nil, fmt.Errorf("failed to construct CDI library: %w", err)
	}

	identifiers := []string{}
	for _, device := range devices {
		_, _, id := parser.ParseDevice(device)
		identifiers = append(identifiers, id)
	}

	deviceSpecs, err := cdilib.GetDeviceSpecsByID(identifiers...)
	if err != nil {
		return nil, fmt.Errorf("failed to get CDI device specs: %w", err)
	}

	commonEdits, err := cdilib.GetCommonEdits()
	if err != nil {
		return nil, fmt.Errorf("failed to get common CDI spec edits: %w", err)
	}

	return spec.New(
		spec.WithDeviceSpecs(deviceSpecs),
		spec.WithEdits(*commonEdits.ContainerEdits),
		spec.WithVendor("runtime.nvidia.com"),
		spec.WithClass("gpu"),
	)
}

type deduplicatedDeviceRequestor struct {
	deviceRequestor
}

func withUniqueDevices(deviceRequestor deviceRequestor) deviceRequestor {
	return &deduplicatedDeviceRequestor{deviceRequestor: deviceRequestor}
}

func (d *deduplicatedDeviceRequestor) DeviceRequests() []string {
	if d == nil {
		return nil
	}
	seen := make(map[string]bool)
	var devices []string
	for _, device := range d.deviceRequestor.DeviceRequests() {
		if seen[device] {
			continue
		}
		seen[device] = true
		devices = append(devices, device)
	}
	return devices
}