// Copyright 2015 clair authors
//
// 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 worker implements the logic to extract useful informations from a
// container layer and store it in the database.
package worker

import (
	"errors"
	"strings"

	"github.com/coreos/clair/database"
	"github.com/coreos/clair/utils"
	cerrors "github.com/coreos/clair/utils/errors"
	"github.com/coreos/clair/worker/detectors"
	"github.com/coreos/pkg/capnslog"
)

const (
	// Version (integer) represents the worker version.
	// Increased each time the engine changes.
	Version = 1

	// maxFileSize is the maximum size of a single file we should extract.
	maxFileSize = 200 * 1024 * 1024 // 200 MiB
)

var (
	log = capnslog.NewPackageLogger("github.com/coreos/clair", "worker")

	// ErrUnsupported is the error that should be raised when an OS or package
	// manager is not supported.
	ErrUnsupported = errors.New("worker: OS and/or package manager are not supported")

	// ErrParentUnknown is the error that should be raised when a parent layer
	// has yet to be processed for the current layer.
	ErrParentUnknown = errors.New("worker: parent layer is unknown, it must be processed first")

	// SupportedNamespacePrefixes is the list of namespace prefixes that the worker supports.
	SupportedNamespacePrefixes = []string{"debian:", "ubuntu:", "centos:"}

	// SupportedImageFormat is the list of image formats that the worker supports.
	SupportedImageFormat = []string{"Docker", "ACI"}
)

// Process detects the Namespace of a layer, the features it adds/removes, and
// then stores everything in the database.
// TODO(Quentin-M): We could have a goroutine that looks for layers that have been analyzed with an
// older engine version and that processes them.
func Process(datastore database.Datastore, name, parentName, path, imageFormat string) error {
	// Verify parameters.
	if name == "" {
		return cerrors.NewBadRequestError("could not process a layer which does not have a name")
	}

	if path == "" {
		return cerrors.NewBadRequestError("could not process a layer which does not have a path")
	}

	if imageFormat == "" {
		return cerrors.NewBadRequestError("could not process a layer which does not have a format")
	}

	isSupported := false
	for _, format := range SupportedImageFormat {
		if strings.EqualFold(imageFormat, format) {
			isSupported = true
			break
		}
	}
	if !isSupported {
		return cerrors.NewBadRequestError("could not process a layer which does not have a supported format")
	}

	log.Debugf("layer %s: processing (Location: %s, Engine version: %d, Parent: %s, Format: %s)",
		name, utils.CleanURL(path), Version, parentName, imageFormat)

	// Check to see if the layer is already in the database.
	layer, err := datastore.FindLayer(name, false, false)
	if err != nil && err != cerrors.ErrNotFound {
		return err
	}

	if err == cerrors.ErrNotFound {
		// New layer case.
		layer = database.Layer{Name: name, EngineVersion: Version}

		// Retrieve the parent if it has one.
		// We need to get it with its Features in order to diff them.
		if parentName != "" {
			parent, err := datastore.FindLayer(parentName, true, false)
			if err != nil && err != cerrors.ErrNotFound {
				return err
			}
			if err == cerrors.ErrNotFound {
				log.Warningf("layer %s: the parent layer (%s) is unknown. it must be processed first", name,
					parentName)
				return ErrParentUnknown
			}
			layer.Parent = &parent
		}
	} else {
		// The layer is already in the database, check if we need to update it.
		if layer.EngineVersion >= Version {
			log.Debugf(`layer %s: layer content has already been processed in the past with engine %d.
        Current engine is %d. skipping analysis`, name, layer.EngineVersion, Version)
			return nil
		}

		log.Debugf(`layer %s: layer content has been analyzed in the past with engine %d. Current
      engine is %d. analyzing again`, name, layer.EngineVersion, Version)
	}

	// Analyze the content.
	layer.Namespace, layer.Features, err = detectContent(name, path, imageFormat, layer.Parent)
	if err != nil {
		return err
	}

	return datastore.InsertLayer(layer)
}

// detectContent downloads a layer's archive and extracts its Namespace and Features.
func detectContent(name, path, imageFormat string, parent *database.Layer) (namespace *database.Namespace, features []database.FeatureVersion, err error) {
	data, err := detectors.DetectData(path, imageFormat, append(detectors.GetRequiredFilesFeatures(),
		detectors.GetRequiredFilesNamespace()...), maxFileSize)
	if err != nil {
		log.Errorf("layer %s: failed to extract data from %s: %s", name, utils.CleanURL(path), err)
		return
	}

	// Detect namespace.
	namespace, err = detectNamespace(data, parent)
	if err != nil {
		return
	}
	if namespace != nil {
		log.Debugf("layer %s: Namespace is %s.", name, namespace.Name)
	} else {
		log.Debugf("layer %s: OS is unknown.", name)
	}

	// Detect features.
	features, err = detectFeatures(name, data, namespace)
	if err != nil {
		log.Errorf("layer %s: package list could not be determined: %s", name, err)
		return
	}

	// If there are no feature detected, use parent's features if possible.
	// TODO(Quentin-M): We eventually want to give the choice to each detectors to use none/some
	// parent's Features. It would be useful for dectectors that can't find their entire result using
	// one Layer.
	if len(features) == 0 && parent != nil {
		features = parent.Features
	}

	log.Debugf("layer %s: detected %d features", name, len(features))
	return
}

func detectNamespace(data map[string][]byte, parent *database.Layer) (namespace *database.Namespace, err error) {
	namespace = detectors.DetectNamespace(data)

	// Attempt to detect the OS from the parent layer.
	if namespace == nil && parent != nil {
		namespace = parent.Namespace
		if err != nil {
			return
		}
	}

	// Ensure that the detected namespace's prefix is supported.
	if namespace != nil {
		isSupported := false
		for _, namespacePrefix := range SupportedNamespacePrefixes {
			if strings.HasPrefix(namespace.Name, namespacePrefix) {
				isSupported = true
				break
			}
		}
		if !isSupported {
			return namespace, ErrUnsupported
		}
	}

	return
}

func detectFeatures(name string, data map[string][]byte, namespace *database.Namespace) (features []database.FeatureVersion, err error) {
	// TODO(Quentin-M): We need to pass the parent image DetectFeatures because it's possible that
	// some detectors would need it in order to produce the entire feature list (if they can only
	// detect a diff). Also, we should probably pass the detected namespace so detectors could
	// make their own decision.
	features, err = detectors.DetectFeatures(data)
	if err != nil {
		return
	}

	// Ensure that every feature has a Namespace associated, otherwise associate the detected
	// namespace. If there is no detected namespace, we'll throw an error.
	for i := 0; i < len(features); i++ {
		if features[i].Feature.Namespace.Name == "" {
			if namespace != nil {
				features[i].Feature.Namespace = *namespace
			} else {
				log.Errorf("layer %s: Layer's namespace is unknown but non-namespaced features have been detected", name)
				err = ErrUnsupported
				return
			}
		}
	}

	return
}