// Copyright 2017 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 (
	"github.com/coreos/pkg/capnslog"

	"github.com/coreos/clair/database"
	"github.com/coreos/clair/ext/featurefmt"
	"github.com/coreos/clair/ext/featurens"
	"github.com/coreos/clair/ext/imagefmt"
	"github.com/coreos/clair/pkg/commonerr"
	"github.com/coreos/clair/pkg/tarutil"
	"github.com/coreos/clair/utils"
)

const (
	// Version (integer) represents the worker version.
	// Increased each time the engine changes.
	Version = 3
)

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 = commonerr.NewBadRequestError("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 = commonerr.NewBadRequestError("worker: parent layer is unknown, it must be processed first")
)

// 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, imageFormat, name, parentName, path string, headers map[string]string) error {
	// Verify parameters.
	if name == "" {
		return commonerr.NewBadRequestError("could not process a layer which does not have a name")
	}

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

	if imageFormat == "" {
		return commonerr.NewBadRequestError("could not process a layer which does not have a 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 != commonerr.ErrNotFound {
		return err
	}

	if err == commonerr.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 != commonerr.ErrNotFound {
				return err
			}
			if err == commonerr.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(imageFormat, name, path, headers, 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(imageFormat, name, path string, headers map[string]string, parent *database.Layer) (namespace *database.Namespace, featureVersions []database.FeatureVersion, err error) {
	totalRequiredFiles := append(featurefmt.RequiredFilenames(), featurens.RequiredFilenames()...)
	files, err := imagefmt.Extract(imageFormat, path, headers, totalRequiredFiles)
	if err != nil {
		log.Errorf("layer %s: failed to extract data from %s: %s", name, utils.CleanURL(path), err)
		return
	}

	namespace, err = detectNamespace(name, files, parent)
	if err != nil {
		return
	}

	// Detect features.
	featureVersions, err = detectFeatureVersions(name, files, namespace, parent)
	if err != nil {
		return
	}
	if len(featureVersions) > 0 {
		log.Debugf("layer %s: detected %d features", name, len(featureVersions))
	}

	return
}

func detectNamespace(name string, files tarutil.FilesMap, parent *database.Layer) (namespace *database.Namespace, err error) {
	namespace, err = featurens.Detect(files)
	if err != nil {
		return
	}
	if namespace != nil {
		log.Debugf("layer %s: detected namespace %q", name, namespace.Name)
		return
	}

	// Fallback to the parent's namespace.
	if parent != nil {
		namespace = parent.Namespace
		if namespace != nil {
			log.Debugf("layer %s: detected namespace %q (from parent)", name, namespace.Name)
			return
		}
	}

	return
}

func detectFeatureVersions(name string, files tarutil.FilesMap, namespace *database.Namespace, parent *database.Layer) (features []database.FeatureVersion, err error) {
	// TODO(Quentin-M): We need to pass the parent image to 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 = featurefmt.ListFeatures(files)
	if err != nil {
		return
	}

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

	// Build a map of the namespaces for each FeatureVersion in our parent layer.
	parentFeatureNamespaces := make(map[string]database.Namespace)
	if parent != nil {
		for _, parentFeature := range parent.Features {
			parentFeatureNamespaces[parentFeature.Feature.Name+":"+parentFeature.Version] = parentFeature.Feature.Namespace
		}
	}

	// Ensure that each FeatureVersion has an associated Namespace.
	for i, feature := range features {
		if feature.Feature.Namespace.Name != "" {
			// There is a Namespace associated.
			continue
		}

		if parentFeatureNamespace, ok := parentFeatureNamespaces[feature.Feature.Name+":"+feature.Version]; ok {
			// The FeatureVersion is present in the parent layer; associate with their Namespace.
			features[i].Feature.Namespace = parentFeatureNamespace
			continue
		}

		if namespace != nil {
			// The Namespace has been detected in this layer; associate it.
			features[i].Feature.Namespace = *namespace
			continue
		}

		log.Warningf("layer %s: Layer's namespace is unknown but non-namespaced features have been detected", name)
		err = ErrUnsupported
		return
	}

	return
}
