Support private channels

This patch adds support to private channels. Previously, private
channels were read-only, while now it's bidirectional like public
channels and IMs.

This required a refactoring of the channels API, and a few bug fixes.
Now anything channel-related goes through the Channel and Channels
structures, and should not use the Slack conversations API directly
anymore.

Signed-off-by: Andrea Barberio <insomniac@slackware.it>

pkg/ircslack/channel.go

@@ -0,0 +1,140 @@
+package ircslack
+
+import (
+	"fmt"
+	"strings"
+	"time"
+
+	"github.com/slack-go/slack"
+)
+
+// Constants for public, private, and multi-party conversation prefixes.
+// Channel threads are prefixed with "+" but they are not conversation types
+// so they do not belong here. A thread is just a message whose destination
+// is within another message in a public, private, or multi-party conversation.
+const (
+	ChannelPrefixPublicChannel  = "#"
+	ChannelPrefixPrivateChannel = "@"
+	ChannelPrefixMpIM           = "&"
+	// NOTE: a thread is not a channel type
+	ChannelPrefixThread = "+"
+)
+
+// HasChannelPrefix returns true if the channel name starts with one of the
+// supproted channel prefixes.
+func HasChannelPrefix(name string) bool {
+	if len(name) == 0 {
+		return false
+	}
+	switch string(name[0]) {
+	case ChannelPrefixPublicChannel, ChannelPrefixPrivateChannel, ChannelPrefixMpIM, ChannelPrefixThread:
+		return true
+	default:
+		return false
+	}
+}
+
+// StripChannelPrefix returns a channel name without its channel prefix. If no
+// channel prefix is present, the string is returned unchanged.
+func StripChannelPrefix(name string) string {
+	if HasChannelPrefix(name) {
+		return name[1:]
+	}
+	return name
+}
+
+// ChannelMembers returns a list of users in the given conversation.
+func ChannelMembers(ctx *IrcContext, channelID string) ([]slack.User, error) {
+	var (
+		members, m []string
+		nextCursor string
+		err        error
+		page       int
+	)
+	for {
+		attempt := 0
+		for {
+			// retry if rate-limited, no more than MaxSlackAPIAttempts times
+			if attempt >= MaxSlackAPIAttempts {
+				return nil, fmt.Errorf("ChannelMembers: exceeded the maximum number of attempts (%d) with the Slack API", MaxSlackAPIAttempts)
+			}
+			log.Debugf("ChannelMembers: page %d attempt #%d nextCursor=%s", page, attempt, nextCursor)
+			m, nextCursor, err = ctx.SlackClient.GetUsersInConversation(&slack.GetUsersInConversationParameters{ChannelID: channelID, Cursor: nextCursor, Limit: 1000})
+			if err != nil {
+				log.Errorf("Failed to get users in conversation '%s': %v", channelID, err)
+				if rlErr, ok := err.(*slack.RateLimitedError); ok {
+					// we were rate-limited. Let's wait as much as Slack
+					// instructs us to do
+					log.Warningf("Hit Slack API rate limiter. Waiting %v", rlErr.RetryAfter)
+					time.Sleep(rlErr.RetryAfter)
+					attempt++
+					continue
+				}
+				return nil, fmt.Errorf("Cannot get member list for conversation %s: %v", channelID, err)
+			}
+			break
+		}
+		members = append(members, m...)
+		log.Debugf("Fetched %d user IDs for channel %s (fetched so far: %d)", len(m), channelID, len(members))
+		// TODO call ctx.Users.FetchByID here in a goroutine to see if this
+		// speeds up
+		if nextCursor == "" {
+			break
+		}
+		page++
+	}
+	log.Debugf("Retrieving user information for %d users", len(members))
+	users, err := ctx.Users.FetchByIDs(ctx.SlackClient, false, members...)
+	if err != nil {
+		return nil, fmt.Errorf("Failed to fetch users by their IDs: %v", err)
+	}
+	return users, nil
+}
+
+// Channel wraps a Slack conversation with a few utility functions.
+type Channel slack.Channel
+
+// IsPublicChannel returns true if the channel is public.
+func (c *Channel) IsPublicChannel() bool {
+	return c.IsChannel && !c.IsPrivate
+}
+
+// IsPrivateChannel returns true if the channel is private.
+func (c *Channel) IsPrivateChannel() bool {
+	return c.IsGroup && c.IsPrivate
+}
+
+// IsMP returns true if it is a multi-party conversation.
+func (c *Channel) IsMP() bool {
+	return c.IsMpIM
+}
+
+// IRCName returns the channel name as it would appear on IRC.
+// Examples:
+// * #channel for public groups
+// * @channel for private groups
+// * &Gxxxx|nick1-nick2-nick3 for multi-party IMs
+func (c *Channel) IRCName() string {
+	switch {
+	case c.IsPublicChannel():
+		return ChannelPrefixPublicChannel + c.Name
+	case c.IsPrivateChannel():
+		return ChannelPrefixPrivateChannel + c.Name
+	case c.IsMP():
+		name := ChannelPrefixMpIM + c.ID + "|" + c.Name
+		name = strings.Replace(name, "mpdm-", "", -1)
+		name = strings.Replace(name, "--", "-", -1)
+		if len(name) >= 30 {
+			return name[:29] + "…"
+		}
+		return name
+	default:
+		log.Warningf("Unknown channel type for channel %+v", c)
+		return "<unknow-channel-type>"
+	}
+}
+
+// SlackName returns the slack.Channel.Name field.
+func (c *Channel) SlackName() string {
+	return c.Name
+}

pkg/ircslack/channels.go

@@ -2,7 +2,6 @@ package ircslack
 
 import (
 	"context"
-	"strings"
 	"sync"
 	"time"
 
@@ -11,23 +10,36 @@ import (
 
 // Channels wraps the channel list with convenient operations and cache.
 type Channels struct {
-	channels   map[string]slack.Channel
+	channels   map[string]Channel
 	Pagination int
 	mu         sync.Mutex
 }
 
 // NewChannels creates a new Channels object.
 func NewChannels(pagination int) *Channels {
 	return &Channels{
-		channels:   make(map[string]slack.Channel),
+		channels:   make(map[string]Channel),
 		Pagination: pagination,
 	}
 }
 
+// SupportedChannelPrefixes returns a list of supported channel prefixes.
+func SupportedChannelPrefixes() []string {
+	return []string{
+		ChannelPrefixPublicChannel,
+		ChannelPrefixPrivateChannel,
+		ChannelPrefixMpIM,
+		ChannelPrefixThread,
+	}
+
+}
+
 // AsMap returns the channels as a map of name -> channel. The map is copied to
 // avoid data races
-func (c *Channels) AsMap() map[string]slack.Channel {
-	var ret map[string]slack.Channel
+func (c *Channels) AsMap() map[string]Channel {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	ret := make(map[string]Channel, len(c.channels))
 	for k, v := range c.channels {
 		ret[k] = v
 	}
@@ -43,20 +55,22 @@ func (c *Channels) Fetch(client *slack.Client) error {
 	var (
 		err      error
 		ctx      = context.Background()
-		channels = make(map[string]slack.Channel)
+		channels = make(map[string]Channel)
 	)
 	start := time.Now()
 	params := slack.GetConversationsParameters{
+		Types: []string{"public_channel", "private_channel"},
 		Limit: c.Pagination,
 	}
 	for err == nil {
 		chans, nextCursor, err := client.GetConversationsContext(ctx, &params)
 		if err == nil {
 			log.Debugf("Retrieved %d channels (current total is %d)", len(chans), len(channels))
-			for _, c := range chans {
+			for _, sch := range chans {
 				// WARNING WARNING WARNING: channels are internally mapped by
-				// name, while users are mapped by ID.
-				channels[c.Name] = c
+				// the Slack name, while users are mapped by Slack ID.
+				ch := Channel(sch)
+				channels[ch.SlackName()] = ch
 			}
 		} else if rateLimitedError, ok := err.(*slack.RateLimitedError); ok {
 			select {
@@ -88,7 +102,7 @@ func (c *Channels) Count() int {
 }
 
 // ByID retrieves a channel by its Slack ID.
-func (c *Channels) ByID(id string) *slack.Channel {
+func (c *Channels) ByID(id string) *Channel {
 	c.mu.Lock()
 	defer c.mu.Unlock()
 	for _, c := range c.channels {
@@ -99,17 +113,16 @@ func (c *Channels) ByID(id string) *slack.Channel {
 	return nil
 }
 
-// ByName retrieves a channel by its Slack name.
-func (c *Channels) ByName(name string) *slack.Channel {
-	if strings.HasPrefix(name, "#") {
+// ByName retrieves a channel by its Slack or IRC name.
+func (c *Channels) ByName(name string) *Channel {
+	if HasChannelPrefix(name) {
+		// without prefix, the channel now has the form of a Slack name
 		name = name[1:]
 	}
 	c.mu.Lock()
 	defer c.mu.Unlock()
-	for _, c := range c.channels {
-		if c.Name == name {
-			return &c
-		}
+	if ch, ok := c.channels[name]; ok {
+		return &ch
 	}
 	return nil
 }