feat: initial release with 48 Mattermost MCP tools

- 27 base tools: channels, messaging, users, reactions, files, DMs
- Team management: invite/remove users, get stats, list members
- Slash commands: execute /remind, /poll, etc.
- Webhook management: incoming and outgoing webhooks
- System tools: server config, logs, bulk status updates
- Channel admin: create, invite, leave, delete channels
- Read-only mode for safe exploration
- Dual token support (bot + PAT) for enhanced security
- Apache 2.0 licensed

operation/messaging/messages.go

@@ -0,0 +1,85 @@
+package messaging
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/karti-ai/mattermost-mcp-server/pkg/log"
+	"github.com/karti-ai/mattermost-mcp-server/pkg/mattermost"
+	"github.com/karti-ai/mattermost-mcp-server/pkg/params"
+	"github.com/karti-ai/mattermost-mcp-server/pkg/to"
+	"github.com/mark3labs/mcp-go/mcp"
+	"github.com/mark3labs/mcp-go/server"
+)
+
+const (
+	GetChannelMessagesToolName = "mattermost_get_channel_messages"
+)
+
+var (
+	GetChannelMessagesTool = mcp.NewTool(
+		GetChannelMessagesToolName,
+		mcp.WithDescription("Read message history from a channel"),
+		mcp.WithString("channel_id", mcp.Required(), mcp.Description("Channel ID to read from")),
+		mcp.WithNumber("limit", mcp.Description("Number of messages to return (default 60, max 200)")),
+		mcp.WithString("before", mcp.Description("Get messages before this post ID (for pagination)")),
+		mcp.WithString("after", mcp.Description("Get messages after this post ID (for pagination)")),
+	)
+)
+
+func init() {
+	registerGetChannelMessagesTool()
+}
+
+func registerGetChannelMessagesTool() {
+	tools := []server.ServerTool{
+		{Tool: GetChannelMessagesTool, Handler: GetChannelMessagesFn},
+	}
+	for _, t := range tools {
+		Tool.RegisterRead(t)
+	}
+}
+
+func GetChannelMessagesFn(ctx context.Context, req mcp.CallToolRequest) (*mcp.CallToolResult, error) {
+	log.Debugf("[Messaging] Called GetChannelMessagesFn")
+
+	args := req.GetArguments()
+
+	channelID, err := params.GetString(args, "channel_id")
+	if err != nil {
+		return to.Error(fmt.Errorf("[channel_id] %v", err)), nil
+	}
+
+	limit := params.GetOptionalInt(args, "limit", 60)
+	if limit > 200 {
+		limit = 200
+	}
+	if limit < 1 {
+		limit = 60
+	}
+
+	before := params.GetOptionalString(args, "before", "")
+	after := params.GetOptionalString(args, "after", "")
+
+	client := mattermost.GetGlobalClient()
+	if client == nil {
+		return to.Error(fmt.Errorf("[internal] client not initialized")), nil
+	}
+
+	posts, err := client.GetChannelPosts(ctx, channelID, int(limit), before, after)
+	if err != nil {
+		return to.Error(fmt.Errorf("[posts] failed to get channel messages: %v", err)), nil
+	}
+
+	results := make([]map[string]interface{}, 0, len(posts.Posts))
+	for _, post := range posts.Posts {
+		results = append(results, SlimPost(post))
+	}
+
+	return to.Result(map[string]interface{}{
+		"posts":      results,
+		"count":      len(results),
+		"channel_id": channelID,
+		"has_more":   len(results) == int(limit),
+	}), nil
+}