/*
	Copyright (c) 2020 Docker Inc.

	Permission is hereby granted, free of charge, to any person
	obtaining a copy of this software and associated documentation
	files (the "Software"), to deal in the Software without
	restriction, including without limitation the rights to use, copy,
	modify, merge, publish, distribute, sublicense, and/or sell copies
	of the Software, and to permit persons to whom the Software is
	furnished to do so, subject to the following conditions:

	The above copyright notice and this permission notice shall be
	included in all copies or substantial portions of the Software.

	THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
	EXPRESS OR IMPLIED,
	INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
	FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
	IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
	HOLDERS BE LIABLE FOR ANY CLAIM,
	DAMAGES OR OTHER LIABILITY,
	WHETHER IN AN ACTION OF CONTRACT,
	TORT OR OTHERWISE,
	ARISING FROM, OUT OF OR IN CONNECTION WITH
	THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/

package store

import (
	"context"
	"encoding/json"
	"fmt"
	"io/ioutil"
	"os"
	"path/filepath"
	"reflect"

	"github.com/opencontainers/go-digest"
	"github.com/pkg/errors"

	"github.com/docker/api/errdefs"
)

const (
	// DefaultContextName is an automatically generated local context
	DefaultContextName = "default"
)

const (
	dockerEndpointKey = "docker"
	configDir         = ".docker"
	contextsDir       = "contexts"
	metadataDir       = "meta"
	metaFile          = "meta.json"
)

type contextStoreKey struct{}

// WithContextStore adds the store to the context
func WithContextStore(ctx context.Context, store Store) context.Context {
	return context.WithValue(ctx, contextStoreKey{}, store)
}

// ContextStore returns the store from the context
func ContextStore(ctx context.Context) Store {
	s, _ := ctx.Value(contextStoreKey{}).(Store)
	return s
}

// Store is the context store
type Store interface {
	// Get returns the context with name, it returns an error if the  context
	// doesn't exist
	Get(name string) (*Metadata, error)
	// GetEndpoint sets the `v` parameter to the value of the endpoint for a
	// particular context type
	GetEndpoint(name string, v interface{}) error
	// Create creates a new context, it returns an error if a context with the
	// same name exists already.
	Create(name string, contextType string, description string, data interface{}) error
	// List returns the list of created contexts
	List() ([]*Metadata, error)
	// Remove removes a context by name from the context store
	Remove(name string) error
}

// Endpoint holds the Docker or the Kubernetes endpoint, they both have the
// `Host` property, only kubernetes will have the `DefaultNamespace`
type Endpoint struct {
	Host             string `json:",omitempty"`
	DefaultNamespace string `json:",omitempty"`
}

const (
	// AciContextType is the endpoint key in the context endpoints for an ACI
	// backend
	AciContextType = "aci"
	// MobyContextType is the endpoint key in the context endpoints for a moby
	// backend
	MobyContextType = "moby"
	// ExampleContextType is the endpoint key in the context endpoints for an
	// example backend
	ExampleContextType = "example"
)

// Metadata represents the docker context metadata
type Metadata struct {
	Name      string                 `json:",omitempty"`
	Type      string                 `json:",omitempty"`
	Metadata  ContextMetadata        `json:",omitempty"`
	Endpoints map[string]interface{} `json:",omitempty"`
}

// ContextMetadata is represtentation of the data we put in a context
// metadata
type ContextMetadata struct {
	Description       string `json:",omitempty"`
	StackOrchestrator string `json:",omitempty"`
}

// AciContext is the context for the ACI backend
type AciContext struct {
	SubscriptionID string `json:",omitempty"`
	Location       string `json:",omitempty"`
	ResourceGroup  string `json:",omitempty"`
}

// MobyContext is the context for the moby backend
type MobyContext struct{}

// ExampleContext is the context for the example backend
type ExampleContext struct{}

type store struct {
	root string
}

// Opt is a functional option for the store
type Opt func(*store)

// WithRoot sets a new root to the store
func WithRoot(root string) Opt {
	return func(s *store) {
		s.root = root
	}
}

// New returns a configured context store with $HOME/.docker as root
func New(opts ...Opt) (Store, error) {
	home, err := os.UserHomeDir()
	if err != nil {
		return nil, err
	}

	root := filepath.Join(home, configDir)
	if err := createDirIfNotExist(root); err != nil {
		return nil, err
	}

	s := &store{
		root: root,
	}

	for _, opt := range opts {
		opt(s)
	}

	m := filepath.Join(s.root, contextsDir, metadataDir)
	if err := createDirIfNotExist(m); err != nil {
		return nil, err
	}

	return s, nil
}

// Get returns the context with the given name
func (s *store) Get(name string) (*Metadata, error) {
	meta := filepath.Join(s.root, contextsDir, metadataDir, contextDirOf(name), metaFile)
	m, err := read(meta)
	if os.IsNotExist(err) {
		return nil, errors.Wrap(errdefs.ErrNotFound, objectName(name))
	} else if err != nil {
		return nil, err
	}

	return m, nil
}

func (s *store) GetEndpoint(name string, data interface{}) error {
	meta, err := s.Get(name)
	if err != nil {
		return err
	}
	if _, ok := meta.Endpoints[meta.Type]; !ok {
		return errors.Wrapf(errdefs.ErrNotFound, "endpoint of type %q", meta.Type)
	}

	dstPtrValue := reflect.ValueOf(data)
	dstValue := reflect.Indirect(dstPtrValue)

	val := reflect.ValueOf(meta.Endpoints[meta.Type])
	valIndirect := reflect.Indirect(val)

	if dstValue.Type() != valIndirect.Type() {
		return errdefs.ErrWrongContextType
	}

	dstValue.Set(valIndirect)

	return nil
}

func read(meta string) (*Metadata, error) {
	bytes, err := ioutil.ReadFile(meta)
	if err != nil {
		return nil, err
	}

	var metadata Metadata
	if err := json.Unmarshal(bytes, &metadata); err != nil {
		return nil, err
	}

	metadata.Endpoints, err = toTypedEndpoints(metadata.Endpoints)
	if err != nil {
		return nil, err
	}

	return &metadata, nil
}

func toTypedEndpoints(endpoints map[string]interface{}) (map[string]interface{}, error) {
	result := map[string]interface{}{}
	for k, v := range endpoints {
		bytes, err := json.Marshal(v)
		if err != nil {
			return nil, err
		}
		typeGetters := getters()
		if _, ok := typeGetters[k]; !ok {
			result[k] = v
			continue
		}

		val := typeGetters[k]()
		err = json.Unmarshal(bytes, &val)
		if err != nil {
			return nil, err
		}

		result[k] = val
	}

	return result, nil
}

func (s *store) Create(name string, contextType string, description string, data interface{}) error {
	if name == DefaultContextName {
		return errors.Wrap(errdefs.ErrAlreadyExists, objectName(name))
	}
	dir := contextDirOf(name)
	metaDir := filepath.Join(s.root, contextsDir, metadataDir, dir)
	if _, err := os.Stat(metaDir); !os.IsNotExist(err) {
		return errors.Wrap(errdefs.ErrAlreadyExists, objectName(name))
	}

	err := os.Mkdir(metaDir, 0755)
	if err != nil {
		return err
	}

	meta := Metadata{
		Name: name,
		Type: contextType,
		Metadata: ContextMetadata{
			Description: description,
		},
		Endpoints: map[string]interface{}{
			(dockerEndpointKey): data,
			(contextType):       data,
		},
	}

	bytes, err := json.Marshal(&meta)
	if err != nil {
		return err
	}

	return ioutil.WriteFile(filepath.Join(metaDir, metaFile), bytes, 0644)
}

func (s *store) List() ([]*Metadata, error) {
	root := filepath.Join(s.root, contextsDir, metadataDir)
	c, err := ioutil.ReadDir(root)
	if err != nil {
		return nil, err
	}

	var result []*Metadata
	for _, fi := range c {
		if fi.IsDir() {
			meta := filepath.Join(root, fi.Name(), metaFile)
			r, err := read(meta)
			if err != nil {
				return nil, err
			}
			result = append(result, r)
		}
	}

	// The default context is not stored in the store, it is in-memory only
	// so we need a special case for it.
	dockerDefault, err := dockerDefaultContext()
	if err != nil {
		return nil, err
	}

	result = append(result, dockerDefault)
	return result, nil
}

func (s *store) Remove(name string) error {
	if name == DefaultContextName {
		return errors.Wrap(errdefs.ErrForbidden, objectName(name))
	}
	dir := filepath.Join(s.root, contextsDir, metadataDir, contextDirOf(name))
	// Check if directory exists because os.RemoveAll returns nil if it doesn't
	if _, err := os.Stat(dir); os.IsNotExist(err) {
		return errors.Wrap(errdefs.ErrNotFound, objectName(name))
	}
	if err := os.RemoveAll(dir); err != nil {
		return errors.Wrapf(errdefs.ErrUnknown, "unable to remove %s: %s", objectName(name), err)
	}
	return nil
}

func contextDirOf(name string) string {
	return digest.FromString(name).Encoded()
}

func objectName(name string) string {
	return fmt.Sprintf("context %q", name)
}

func createDirIfNotExist(dir string) error {
	if _, err := os.Stat(dir); os.IsNotExist(err) {
		if err = os.MkdirAll(dir, 0755); err != nil {
			return err
		}
	}
	return nil
}

// Different context types managed by the store.
// TODO(rumpl): we should make this extensible in the future if we want to
// be able to manage other contexts.
func getters() map[string]func() interface{} {
	return map[string]func() interface{}{
		"aci": func() interface{} {
			return &AciContext{}
		},
		"moby": func() interface{} {
			return &MobyContext{}
		},
		"example": func() interface{} {
			return &ExampleContext{}
		},
	}
}