Implement GET channels endpoints for APIv4 (#5363)

* implement get channels endpoints and updated drivers and unittests

* removed channel deletion on tear down, removed manage permission on get channels endpoints, and updated utils to add constant channel length

* added constants for user, team and channel length, updated context to use the model functions

* make sure team name length should be less than the minimum length and revert underscore to team name validity

* changed post test condition from notfound to unauthorized

5 files changed, 49 insertions, 7 deletions

diff --git a/model/channel.go b/model/channel.go
index 2ad257ccc..3ad7da1fa 100644
--- a/model/channel.go
+++ b/model/channel.go
@@ -15,6 +15,7 @@ const (
 	CHANNEL_DIRECT                 = "D"
 	DEFAULT_CHANNEL                = "town-square"
 	CHANNEL_DISPLAY_NAME_MAX_RUNES = 64
+	CHANNEL_NAME_MIN_LENGTH        = 3
 	CHANNEL_NAME_MAX_LENGTH        = 64
 	CHANNEL_HEADER_MAX_RUNES       = 1024
 	CHANNEL_PURPOSE_MAX_RUNES      = 250
@@ -83,10 +84,6 @@ func (o *Channel) IsValid() *AppError {
 		return NewLocAppError("Channel.IsValid", "model.channel.is_valid.display_name.app_error", nil, "id="+o.Id)
 	}
 
-	if len(o.Name) > CHANNEL_NAME_MAX_LENGTH {
-		return NewLocAppError("Channel.IsValid", "model.channel.is_valid.name.app_error", nil, "id="+o.Id)
-	}
-
 	if !IsValidChannelIdentifier(o.Name) {
 		return NewLocAppError("Channel.IsValid", "model.channel.is_valid.2_or_more.app_error", nil, "id="+o.Id)
 	}
diff --git a/model/client4.go b/model/client4.go
index 7afc63359..5c51026a9 100644
--- a/model/client4.go
+++ b/model/client4.go
@@ -72,6 +72,10 @@ func (c *Client4) GetTeamRoute(teamId string) string {
 	return fmt.Sprintf(c.GetTeamsRoute()+"/%v", teamId)
 }
 
+func (c *Client4) GetTeamByNameRoute(teamName string) string {
+	return fmt.Sprintf(c.GetTeamsRoute()+"/name/%v", teamName)
+}
+
 func (c *Client4) GetTeamMemberRoute(teamId, userId string) string {
 	return fmt.Sprintf(c.GetTeamRoute(teamId)+"/members/%v", userId)
 }
@@ -84,6 +88,14 @@ func (c *Client4) GetChannelRoute(channelId string) string {
 	return fmt.Sprintf(c.GetChannelsRoute()+"/%v", channelId)
 }
 
+func (c *Client4) GetChannelByNameRoute(channelName, teamId string) string {
+	return fmt.Sprintf(c.GetTeamRoute(teamId)+"/channels/name/%v", channelName)
+}
+
+func (c *Client4) GetChannelByNameForTeamNameRoute(channelName, teamName string) string {
+	return fmt.Sprintf(c.GetTeamByNameRoute(teamName)+"/channels/name/%v", channelName)
+}
+
 func (c *Client4) GetChannelMembersRoute(channelId string) string {
 	return fmt.Sprintf(c.GetChannelRoute(channelId) + "/members")
 }
@@ -444,6 +456,36 @@ func (c *Client4) CreateDirectChannel(userId1, userId2 string) (*Channel, *Respo
 	}
 }
 
+// GetChannel returns a channel based on the provided channel id string.
+func (c *Client4) GetChannel(channelId, etag string) (*User, *Response) {
+	if r, err := c.DoApiGet(c.GetChannelRoute(channelId), etag); err != nil {
+		return nil, &Response{StatusCode: r.StatusCode, Error: err}
+	} else {
+		defer closeBody(r)
+		return UserFromJson(r.Body), BuildResponse(r)
+	}
+}
+
+// GetChannelByName returns a channel based on the provided channel name and team id strings.
+func (c *Client4) GetChannelByName(channelName, teamId string, etag string) (*User, *Response) {
+	if r, err := c.DoApiGet(c.GetChannelByNameRoute(channelName, teamId), etag); err != nil {
+		return nil, &Response{StatusCode: r.StatusCode, Error: err}
+	} else {
+		defer closeBody(r)
+		return UserFromJson(r.Body), BuildResponse(r)
+	}
+}
+
+// GetChannelByNameForTeamName returns a channel based on the provided channel name and team name strings.
+func (c *Client4) GetChannelByNameForTeamName(channelName, teamName string, etag string) (*User, *Response) {
+	if r, err := c.DoApiGet(c.GetChannelByNameForTeamNameRoute(channelName, teamName), etag); err != nil {
+		return nil, &Response{StatusCode: r.StatusCode, Error: err}
+	} else {
+		defer closeBody(r)
+		return UserFromJson(r.Body), BuildResponse(r)
+	}
+}
+
 // GetChannelMembers gets a page of channel members.
 func (c *Client4) GetChannelMembers(channelId string, page, perPage int, etag string) (*ChannelMembers, *Response) {
 	query := fmt.Sprintf("?page=%v&per_page=%v", page, perPage)
diff --git a/model/team.go b/model/team.go
index 310ad2d91..99444bc5e 100644
--- a/model/team.go
+++ b/model/team.go
@@ -22,6 +22,7 @@ const (
 	TEAM_DISPLAY_NAME_MAX_RUNES     = 64
 	TEAM_EMAIL_MAX_LENGTH           = 128
 	TEAM_NAME_MAX_LENGTH            = 64
+	TEAM_NAME_MIN_LENGTH            = 2
 )
 
 type Team struct {
@@ -228,7 +229,7 @@ func IsValidTeamName(s string) bool {
 		return false
 	}
 
-	if len(s) <= 1 {
+	if len(s) < TEAM_NAME_MIN_LENGTH {
 		return false
 	}
 
diff --git a/model/user.go b/model/user.go
index b2b077e5f..8e02fe1ab 100644
--- a/model/user.go
+++ b/model/user.go
@@ -29,6 +29,8 @@ const (
 	USER_FIRST_NAME_MAX_RUNES = 64
 	USER_LAST_NAME_MAX_RUNES  = 64
 	USER_AUTH_DATA_MAX_LENGTH = 128
+	USER_NAME_MAX_LENGTH      = 64
+	USER_NAME_MIN_LENGTH      = 3
 )
 
 type User struct {
@@ -487,7 +489,7 @@ var restrictedUsernames = []string{
 }
 
 func IsValidUsername(s string) bool {
-	if len(s) == 0 || len(s) > 64 {
+	if len(s) < USER_NAME_MIN_LENGTH || len(s) > USER_NAME_MAX_LENGTH {
 		return false
 	}
 
diff --git a/model/utils.go b/model/utils.go
index 9ecc19595..fcdf5b5cd 100644
--- a/model/utils.go
+++ b/model/utils.go
@@ -280,7 +280,7 @@ func IsValidChannelIdentifier(s string) bool {
 		return false
 	}
 
-	if len(s) < 2 {
+	if len(s) < CHANNEL_NAME_MIN_LENGTH {
 		return false
 	}