From ee63c0a9efdeb2c0c6dedd5cf55e3f020a96ef99 Mon Sep 17 00:00:00 2001
From: ChronosX88 <chronosx88@gmail.com>
Date: Tue, 25 Jan 2022 19:27:58 +0300
Subject: [PATCH] Implement GROUP command

---
 README.md                           |  2 +-
 internal/backend/sqlite/sqlite.go   |  5 +++++
 internal/backend/storage_backend.go |  1 +
 internal/protocol/constants.go      |  2 ++
 internal/server/handler.go          | 35 +++++++++++++++++++++++++++++
 internal/server/session.go          |  3 +++
 6 files changed, 47 insertions(+), 1 deletion(-)

diff --git a/README.md b/README.md
index c96181f..0567513 100644
--- a/README.md
+++ b/README.md
@@ -21,7 +21,7 @@
 - :heavy_check_mark: `QUIT`
 - :x: `ARTICLE`
 - :x: `BODY`
-- :x: `GROUP`
+- :heavy_check_mark: `GROUP`
 - :x: `HDR`
 - :x: `HEAD`
 - :x: `HELP`
diff --git a/internal/backend/sqlite/sqlite.go b/internal/backend/sqlite/sqlite.go
index e4eb9c0..cdfb3e5 100644
--- a/internal/backend/sqlite/sqlite.go
+++ b/internal/backend/sqlite/sqlite.go
@@ -83,3 +83,8 @@ func (sb *SQLiteBackend) GetGroupLowWaterMark(g models.Group) (int, error) {
 	var waterMark int
 	return waterMark, sb.db.Get(&waterMark, "SELECT article_id FROM articles_to_groups WHERE group_id = ? ORDER BY article_id LIMIT 1", g.ID)
 }
+
+func (sb *SQLiteBackend) GetGroup(groupName string) (models.Group, error) {
+	var group models.Group
+	return group, sb.db.Get(&group, "SELECT * FROM groups WHERE group_name = ?", groupName)
+}
diff --git a/internal/backend/storage_backend.go b/internal/backend/storage_backend.go
index 6fe0a4a..3a01bac 100644
--- a/internal/backend/storage_backend.go
+++ b/internal/backend/storage_backend.go
@@ -9,6 +9,7 @@ const (
 type StorageBackend interface {
 	ListGroups() ([]models.Group, error)
 	ListGroupsByPattern(pattern string) ([]models.Group, error)
+	GetGroup(groupName string) (models.Group, error)
 	GetArticlesCount(g models.Group) (int, error)
 	GetGroupLowWaterMark(g models.Group) (int, error)
 	GetGroupHighWaterMark(g models.Group) (int, error)
diff --git a/internal/protocol/constants.go b/internal/protocol/constants.go
index d5b4414..49a7f52 100644
--- a/internal/protocol/constants.go
+++ b/internal/protocol/constants.go
@@ -11,6 +11,7 @@ const (
 	CommandDate         = "DATE"
 	CommandMode         = "MODE"
 	CommandList         = "LIST"
+	CommandGroup        = "GROUP"
 )
 
 const (
@@ -34,4 +35,5 @@ const (
 	MessageErrorHappened                     = "403 Failed to process command:"
 	MessageListOfNewsgroupsFollows           = "215 list of newsgroups follows"
 	MessageSyntaxError                       = "501 Syntax Error"
+	MessageNoSuchGroup                       = "411 No such newsgroup"
 )
diff --git a/internal/server/handler.go b/internal/server/handler.go
index 30c340f..7fb3260 100644
--- a/internal/server/handler.go
+++ b/internal/server/handler.go
@@ -1,6 +1,7 @@
 package server
 
 import (
+	"database/sql"
 	"fmt"
 	"github.com/ChronosX88/yans/internal/backend"
 	"github.com/ChronosX88/yans/internal/models"
@@ -23,6 +24,7 @@ func NewHandler(b backend.StorageBackend) *Handler {
 		protocol.CommandQuit:         h.handleQuit,
 		protocol.CommandList:         h.handleList,
 		protocol.CommandMode:         h.handleModeReader,
+		protocol.CommandGroup:        h.handleGroup,
 	}
 	return h
 }
@@ -143,6 +145,39 @@ func (h *Handler) handleModeReader(s *Session, arguments []string, id uint) erro
 	return s.tconn.PrintfLine(protocol.MessageReaderModePostingProhibited) // TODO vary on auth status
 }
 
+func (h *Handler) handleGroup(s *Session, arguments []string, id uint) error {
+	s.tconn.StartResponse(id)
+	defer s.tconn.EndResponse(id)
+
+	if len(arguments) == 0 || len(arguments) > 1 {
+		return s.tconn.PrintfLine(protocol.MessageSyntaxError)
+	}
+
+	g, err := h.backend.GetGroup(arguments[0])
+	if err != nil {
+		if err == sql.ErrNoRows {
+			return s.tconn.PrintfLine(protocol.MessageNoSuchGroup)
+		}
+		return err
+	}
+	highWaterMark, err := h.backend.GetGroupHighWaterMark(g)
+	if err != nil {
+		return err
+	}
+	lowWaterMark, err := h.backend.GetGroupLowWaterMark(g)
+	if err != nil {
+		return err
+	}
+	articlesCount, err := h.backend.GetArticlesCount(g)
+	if err != nil {
+		return err
+	}
+
+	s.currentGroup = &g
+
+	return s.tconn.PrintfLine("211 %d %d %d %s", articlesCount, lowWaterMark, highWaterMark, g.GroupName)
+}
+
 func (h *Handler) Handle(s *Session, message string, id uint) error {
 	splittedMessage := strings.Split(message, " ")
 	for i, v := range splittedMessage {
diff --git a/internal/server/session.go b/internal/server/session.go
index 533609e..8a2dcb5 100644
--- a/internal/server/session.go
+++ b/internal/server/session.go
@@ -2,6 +2,7 @@ package server
 
 import (
 	"context"
+	"github.com/ChronosX88/yans/internal/models"
 	"github.com/ChronosX88/yans/internal/protocol"
 	"io"
 	"log"
@@ -24,6 +25,8 @@ type Session struct {
 	id           string
 	closed       chan<- bool
 	h            *Handler
+
+	currentGroup *models.Group
 	mode         SessionMode
 }