// ExtractToken returns the just-created Token from a CreateResult.
func (result CreateResult) ExtractToken() (*Token, error) {
	if result.Err != nil {
		return nil, result.Err
	}

	var response struct {
		Access struct {
			Token struct {
				Expires string         `mapstructure:"expires"`
				ID      string         `mapstructure:"id"`
				Tenant  tenants.Tenant `mapstructure:"tenant"`
			} `mapstructure:"token"`
		} `mapstructure:"access"`
	}

	err := mapstructure.Decode(result.Body, &response)
	if err != nil {
		return nil, err
	}

	expiresTs, err := time.Parse(gophercloud.RFC3339Milli, response.Access.Token.Expires)
	if err != nil {
		return nil, err
	}

	return &Token{
		ID:        response.Access.Token.ID,
		ExpiresAt: expiresTs,
		Tenant:    response.Access.Token.Tenant,
	}, nil
}

// ExtractToken interprets a commonResult as a Token.
func (r commonResult) ExtractToken() (*Token, error) {
	if r.Err != nil {
		return nil, r.Err
	}

	var response struct {
		Token struct {
			ExpiresAt string `mapstructure:"expires_at"`
		} `mapstructure:"token"`
	}

	var token Token

	// Parse the token itself from the stored headers.
	token.ID = r.Header.Get("X-Subject-Token")

	err := mapstructure.Decode(r.Body, &response)
	if err != nil {
		return nil, err
	}

	// Attempt to parse the timestamp.
	token.ExpiresAt, err = time.Parse(gophercloud.RFC3339Milli, response.Token.ExpiresAt)

	return &token, err
}

// ExtractVolumes extracts and returns Volumes. It is used while iterating over a volumes.List call.
func ExtractVolumes(page pagination.Page) ([]Volume, error) {
	var response struct {
		Volumes []Volume `json:"volumes"`
	}

	err := mapstructure.Decode(page.(ListResult).Body, &response)
	return response.Volumes, err
}

// ExtractSnapshots extracts and returns Snapshots. It is used while iterating over a snapshots.List call.
func ExtractSnapshots(page pagination.Page) ([]Snapshot, error) {
	var response struct {
		Snapshots []Snapshot `json:"snapshots"`
	}

	err := mapstructure.Decode(page.(ListResult).Body, &response)
	return response.Snapshots, err
}

// ExtractSubnets accepts a Page struct, specifically a SubnetPage struct,
// and extracts the elements into a slice of Subnet structs. In other words,
// a generic collection is mapped into a relevant slice.
func ExtractSubnets(page pagination.Page) ([]Subnet, error) {
	var resp struct {
		Subnets []Subnet `mapstructure:"subnets" json:"subnets"`
	}

	err := mapstructure.Decode(page.(SubnetPage).Body, &resp)

	return resp.Subnets, err
}

// ExtractImages converts a page of List results into a slice of usable Image structs.
func ExtractImages(page pagination.Page) ([]Image, error) {
	casted := page.(ImagePage).Body
	var results struct {
		Images []Image `mapstructure:"images"`
	}

	err := mapstructure.Decode(casted, &results)
	return results.Images, err
}

// ExtractPorts accepts a Page struct, specifically a PortPage struct,
// and extracts the elements into a slice of Port structs. In other words,
// a generic collection is mapped into a relevant slice.
func ExtractPorts(page pagination.Page) ([]Port, error) {
	var resp struct {
		Ports []Port `mapstructure:"ports" json:"ports"`
	}

	err := mapstructure.Decode(page.(PortPage).Body, &resp)

	return resp.Ports, err
}

// ExtractTenants returns a slice of Tenants contained in a single page of results.
func ExtractTenants(page pagination.Page) ([]Tenant, error) {
	casted := page.(TenantPage).Body
	var response struct {
		Tenants []Tenant `mapstructure:"tenants"`
	}

	err := mapstructure.Decode(casted, &response)
	return response.Tenants, err
}

// ExtractGroups accepts a Page struct, specifically a SecGroupPage struct,
// and extracts the elements into a slice of SecGroup structs. In other words,
// a generic collection is mapped into a relevant slice.
func ExtractGroups(page pagination.Page) ([]SecGroup, error) {
	var resp struct {
		SecGroups []SecGroup `mapstructure:"security_groups" json:"security_groups"`
	}

	err := mapstructure.Decode(page.(SecGroupPage).Body, &resp)

	return resp.SecGroups, err
}

// ExtractNetworks accepts a Page struct, specifically a NetworkPage struct,
// and extracts the elements into a slice of Network structs. In other words,
// a generic collection is mapped into a relevant slice.
func ExtractNetworks(page pagination.Page) ([]Network, error) {
	var resp struct {
		Networks []Network `mapstructure:"networks" json:"networks"`
	}

	err := mapstructure.Decode(page.(NetworkPage).Body, &resp)

	return resp.Networks, err
}

// ExtractInfo is a function that takes a page of objects and returns their full information.
func ExtractInfo(page pagination.Page) ([]Object, error) {
	untyped := page.(ObjectPage).Body.([]interface{})
	results := make([]Object, len(untyped))
	for index, each := range untyped {
		object := each.(map[string]interface{})
		err := mapstructure.Decode(object, &results[index])
		if err != nil {
			return results, err
		}
	}
	return results, nil
}

// Extract interprets any MetadatumResult as a Metadatum, if possible.
func (r MetadatumResult) Extract() (map[string]string, error) {
	if r.Err != nil {
		return nil, r.Err
	}

	var response struct {
		Metadatum map[string]string `mapstructure:"meta"`
	}

	err := mapstructure.Decode(r.Body, &response)
	return response.Metadatum, err
}

// Extract is a method that attempts to interpret any VolumeAttachment resource
// response as a VolumeAttachment struct.
func (r VolumeAttachmentResult) Extract() (*VolumeAttachment, error) {
	if r.Err != nil {
		return nil, r.Err
	}

	var res struct {
		VolumeAttachment *VolumeAttachment `json:"volumeAttachment" mapstructure:"volumeAttachment"`
	}

	err := mapstructure.Decode(r.Body, &res)
	return res.VolumeAttachment, err
}

// Extract is a method that attempts to interpret any KeyPair resource response as a KeyPair struct.
func (r keyPairResult) Extract() (*KeyPair, error) {
	if r.Err != nil {
		return nil, r.Err
	}

	var res struct {
		KeyPair *KeyPair `json:"keypair" mapstructure:"keypair"`
	}

	err := mapstructure.Decode(r.Body, &res)
	return res.KeyPair, err
}

func ExtractLinkedInts(page Page) ([]int, error) {
	var response struct {
		Ints []int `mapstructure:"ints"`
	}

	err := mapstructure.Decode(page.(LinkedPageResult).Body, &response)
	if err != nil {
		return nil, err
	}

	return response.Ints, nil
}

// NextPageURL is invoked when a paginated collection of networks has reached
// the end of a page and the pager seeks to traverse over a new one. In order
// to do this, it needs to construct the next page's URL.
func (p NetworkPage) NextPageURL() (string, error) {
	type resp struct {
		Links []gophercloud.Link `mapstructure:"networks_links"`
	}

	var r resp
	err := mapstructure.Decode(p.Body, &r)
	if err != nil {
		return "", err
	}

	return gophercloud.ExtractNextURL(r.Links)
}

// Extract will get the Snapshot object out of the commonResult object.
func (r commonResult) Extract() (*Snapshot, error) {
	if r.Err != nil {
		return nil, r.Err
	}

	var res struct {
		Snapshot *Snapshot `json:"snapshot"`
	}

	err := mapstructure.Decode(r.Body, &res)

	return res.Snapshot, err
}

// Extract is a function that accepts a result and extracts a network resource.
func (r commonResult) Extract() (*Network, error) {
	if r.Err != nil {
		return nil, r.Err
	}

	var res struct {
		Network *Network `json:"network"`
	}

	err := mapstructure.Decode(r.Body, &res)

	return res.Network, err
}

// Extract is a function that accepts a result and extracts a security group.
func (r commonResult) Extract() (*SecGroup, error) {
	if r.Err != nil {
		return nil, r.Err
	}

	var res struct {
		SecGroup *SecGroup `mapstructure:"security_group" json:"security_group"`
	}

	err := mapstructure.Decode(r.Body, &res)

	return res.SecGroup, err
}

// ExtractAddresses interprets the results of a single page from a ListAddresses() call,
// producing a map of addresses.
func ExtractAddresses(page pagination.Page) (map[string][]Address, error) {
	casted := page.(AddressPage).Body

	var response struct {
		Addresses map[string][]Address `mapstructure:"addresses"`
	}

	err := mapstructure.Decode(casted, &response)
	if err != nil {
		return nil, err
	}

	return response.Addresses, err
}