prologic-saltyim/lookup.go

package saltyim

import (
	"crypto/sha256"
	"encoding/json"
	"fmt"
	"io/ioutil"
	"net"
	"net/http"
	"net/url"
	"strings"

	sync "github.com/sasha-s/go-deadlock"
)

// Addr represents a Salty IM User's Address
type Addr struct {
	mu sync.RWMutex

	User   string
	Domain string

	endpoint         *url.URL
	discoveredDomain string
}

// IsZero returns true if the address is empty
func (a *Addr) IsZero() bool {
	a.mu.RLock()
	defer a.mu.RUnlock()

	return a.User == "" && a.Domain == ""
}

func (a *Addr) String() string {
	return fmt.Sprintf("%s@%s", a.User, a.Domain)
}

// Hash returns the Hex(SHA256Sum()) of the Address
func (a *Addr) Hash() string {
	return fmt.Sprintf("%x", sha256.Sum256([]byte(a.String())))
}

// Formatted returns a formatted user used in the Salty Message Format
// <timestamp\t(<user>) <message>\n
func (a *Addr) Formatted() string {
	return fmt.Sprintf("(%s)", a)
}

// Endpoint returns the discovered Endpoint
func (a *Addr) Endpoint() *url.URL {
	a.mu.RLock()
	defer a.mu.RUnlock()

	return a.endpoint

}

// DiscoveredDomain returns the discovered domain (if any) of fallbacks to the Domain
func (a *Addr) DiscoveredDomain() string {
	a.mu.RLock()
	defer a.mu.RUnlock()

	if a.discoveredDomain != "" {
		return a.discoveredDomain
	}
	return a.Domain
}

// URI returns the Well-Known URI for this Addr
func (a *Addr) URI() string {
	return fmt.Sprintf("https://%s/.well-known/salty/%s.json", a.DiscoveredDomain(), a.User)
}

// HashURI returns the Well-Known HashURI for this Addr
func (a *Addr) HashURI() string {
	return fmt.Sprintf("https://%s/.well-known/salty/%s.json", a.DiscoveredDomain(), a.Hash())
}

func (a *Addr) Refresh() error {
	a.mu.Lock()
	defer a.mu.Unlock()

	_, records, err := net.LookupSRV("salty", "tcp", a.Domain)
	if err == nil && len(records) > 0 {
		a.discoveredDomain = records[0].Target
	}

	config, err := Lookup(a.String())
	if err != nil {
		return fmt.Errorf("error looking up endpoint for %s: %w", a, err)
	}

	u, err := url.Parse(config.Endpoint)
	if err != nil {
		return fmt.Errorf("error parsing endpoint %s: %w", config.Endpoint, err)
	}
	a.endpoint = u

	return nil
}

// ParseAddr parsers a Salty Address for a user into it's user and domain
// parts and returns an Addr object with the User and Domain and a method
// for returning the expected User's Well-Known URI
func ParseAddr(addr string) (*Addr, error) {
	parts := strings.Split(addr, "@")
	if len(parts) != 2 {
		return nil, fmt.Errorf("expected nick@domain found %q", addr)
	}

	return &Addr{User: parts[0], Domain: parts[1]}, nil
}

// Lookup looks up a Salty Address for a User by parsing the user's domain and
// making a request to the user's Well-Known URI expected to be located at
// https://domain/.well-known/salty/<user>.json
func Lookup(addr string) (Config, error) {
	a, err := ParseAddr(addr)
	if err != nil {
		return Config{}, err
	}
	config, err := fetchConfig(a.HashURI())
	if err != nil {
		// Fallback to plain user nick
		config, err = fetchConfig(a.URI())
	}
	return config, err
}

func fetchConfig(addr string) (Config, error) {
	// Attempt using hash
	res, err := Request(http.MethodGet, addr, nil, nil)
	if err != nil {
		return Config{}, err
	}

	data, err := ioutil.ReadAll(res.Body)
	if err != nil {
		return Config{}, err
	}

	var config Config
	if err := json.Unmarshal(data, &config); err != nil {
		return Config{}, err
	}

	return config, err
}