gem "axn-mcp"

class GreetUser < Axn::MCP::Tool
  description "Greet a user by name"

  expects :name, type: String, description: "The user's name"
  exposes :greeting, type: String, description: "The greeting message"

  def call
    expose greeting: "Hello, #{name}!"
  end
end

class CreateNote < Axn::MCP::Tool
  description "Create a new note"

  expects :title, type: String, description: "Note title"
  expects :content, type: String, description: "Note body"
  expects :tags, type: Array, optional: true, description: "Optional tags"

  exposes :note_id, type: Integer, description: "ID of the created note"

  def call
    note = Note.create!(title:, content:, tags: tags || [])
    expose note_id: note.id
  end
end

expects :start_date, type: Date, optional: true, description: "Inclusive lower bound (YYYY-MM-DD)"
exposes :results,    type: Array,                description: "Matching records"

exposes :config, type: Hash do
  field :region,  type: String
  field :timeout, type: Integer, optional: true
end

IntegrationRecord = Data.define(:source, :provider_name, :active, :status)

exposes :integration, type: IntegrationRecord do
  field :status, type: String, inclusion: { in: %w[connected error needs_reconnect] }
  field :active, type: :boolean, optional: true
end

exposes :config, type: Hash do
  field :region,    type: String
  field :retention, type: Hash do
    field :days, type: Integer
  end
end

exposes :tags, type: Array, of: String

exposes :values, type: Array, of: [String, Numeric]

exposes :integrations, type: Array, of: IntegrationRecord

exposes :integrations, type: Array, of: IntegrationRecord do
  field :status, type: String, inclusion: { in: %w[connected error needs_reconnect] }
  field :active, type: :boolean, optional: true
end

class UpdateUser < Axn::MCP::Tool
  description "Update a user's profile"

  expects :user, model: true
  expects :name, type: String, optional: true

  def call
    user.update!(name:) if name
  end
end

expects :status, inclusion: { in: %w[active inactive pending] }

class ReadOnlyTool < Axn::MCP::Tool
  description "Fetch data without side effects"
  read_only!

  # ...
end

class DangerousTool < Axn::MCP::Tool
  description "Delete all the things"
  destructive!
  idempotent!

  # ...
end

class CustomAnnotations < Axn::MCP::Tool
  annotations(
    read_only_hint: true,
    idempotent_hint: true,
    title: "My Custom Tool",
  )

  # ...
end

SearchTool = Axn::MCP::Tool.define(
  description: "Search for items",
  expects: { query: { type: String, description: "Search query" } },
  exposes: { results: { type: Array } },
  annotations: { read_only_hint: true },
) do
  expose results: Item.search(query)
end

class AuthenticatedTool < Axn::MCP::Tool
  description "Do something with the current user"

  def call
    current_user = server_context&.dig(:user)
    # ...
  end
end

# Called FROM MCP server (server_context injected) → returns MCP::Tool::Response
# This happens automatically when registered with MCP::Server

# Called DIRECTLY without server_context → returns Axn::Result
result = MyTool.call(name: "Alice")
if result.ok?
  puts result.greeting
else
  puts "Error: #{result.message}"
end

# Or use call! to raise on failure
result = MyTool.call!(name: "Bob")
puts result.greeting

def call
  fail! "User not found" unless user
  fail! "Unauthorized" unless authorized?

  # success path...
end

require "mcp"
require "axn-mcp"

server = MCP::Server.new(
  name: "my-server",
  version: "1.0.0",
  tools: [GreetUser, CreateNote, SearchTool],
)

# Use with stdio transport
transport = MCP::Server::Transports::StdioTransport.new(server)
transport.open