Query Execution

# Main parsing interface
def GraphQL.parse(graphql_string, trace: GraphQL::Tracing::NullTrace, filename: nil, max_tokens: nil)
def GraphQL.parse_file(filename)
def GraphQL.scan(graphql_string)

# Language parsing classes
class GraphQL::Language::Parser
  def self.parse(string, filename: nil, trace: GraphQL::Tracing::NullTrace)
end

class GraphQL::Language::Lexer  
  def self.tokenize(graphql_string)
end

# Parse result
class GraphQL::Language::Nodes::Document
  def definitions
  def to_query_string
end

# Parse a query string
query_string = '
  query GetUser($id: ID!) {
    user(id: $id) {
      id
      name
      email
    }
  }
'

document = GraphQL.parse(query_string)
puts document.definitions.first.name  # "GetUser"

# Parse from file
document = GraphQL.parse_file("queries/get_user.graphql")

# Tokenize for analysis
tokens = GraphQL.scan(query_string)
tokens.each { |token| puts "#{token[0]}: #{token[1]}" }

class GraphQL::Query
  def initialize(schema, query_string = nil, document: nil, variables: {}, context: {}, operation_name: nil, root_value: nil, max_depth: nil, max_complexity: nil)
  
  # Execution
  def result
  def result_name
  
  # Validation and analysis
  def valid?
  def static_errors
  def analyzers
  
  # Query introspection
  def operation_name
  def selected_operation
  def variables
  def context
  def root_value
  def schema
  def document
  def query_string
  
  # Utilities
  def fingerprint
  def sanitized_query_string(inline_variables: false)
end

# Create and execute a query
schema = MySchema
query_string = 'query { users { id name } }'

query = GraphQL::Query.new(
  schema,
  query_string,
  variables: {},
  context: { current_user: current_user },
  operation_name: nil
)

# Check if query is valid
unless query.valid?
  puts "Query errors:"
  query.static_errors.each { |error| puts error.message }
end

# Execute the query
result = query.result
puts result.to_json

# Query introspection
puts "Operation: #{query.operation_name}"
puts "Variables: #{query.variables}"
puts "Fingerprint: #{query.fingerprint}"

class GraphQL::Query::Result
  # Data access
  def [] (key)
  def dig(*keys)
  def to_h
  def to_json(**options)
  
  # Error handling
  def context_errors
  def execution_errors
  
  # Metadata
  def query
  def extensions
end

result = MySchema.execute('query { user(id: "1") { name email } }')

# Access data
user_data = result["data"]["user"]
user_name = result.dig("data", "user", "name")

# Check for errors
if result["errors"]&.any?
  puts "GraphQL errors:"
  result["errors"].each { |error| puts error["message"] }
end

# Convert to JSON for API response
json_response = result.to_json

# Access extensions (custom metadata)
if result["extensions"]
  puts "Query complexity: #{result['extensions']['complexity']}"
end

class GraphQL::Query::Context
  def initialize(query:, schema:, values: {})
  
  # Data access
  def [] (key)
  def []= (key, value)
  def key?(key)
  def fetch(key, default = nil)
  def delete(key)
  def merge(new_values)
  def merge!(new_values)
  
  # Namespace support
  def namespace(ns_name)
  
  # Query access
  def query
  def schema
  def warden
  def interpreter?
  
  # Execution state
  def errors
  def add_error(error)
  def invalid_null?
  def skip
  def ast_node
  def irep_node
  def path
end

# Setting up context in schema execution
result = MySchema.execute(
  query_string,
  context: {
    current_user: current_user,
    request: request,
    abilities: current_user.abilities,
    dataloader: MyDataLoader.new
  }
)

# Accessing context in resolvers
class UserType < GraphQL::Schema::Object
  field :posts, [PostType], null: true
  
  def posts
    current_user = context[:current_user]
    abilities = context[:abilities]
    
    # Filter posts based on user permissions
    object.posts.accessible_by(abilities)
  end
end

# Adding errors to context
def secure_field
  unless context[:current_user]&.admin?
    context.add_error(GraphQL::ExecutionError.new(
      "Access denied",
      path: context.path,
      extensions: { code: "UNAUTHORIZED" }
    ))
    return nil
  end
  
  # Return authorized data
  object.secure_data
end

# Using namespaced context
def expensive_computation
  cache = context.namespace(:cache)
  cache[:computation_result] ||= perform_expensive_operation
end

class GraphQL::Schema
  # Single query execution
  def self.execute(query_string, variables: {}, context: {}, operation_name: nil, root_value: nil, only: nil, except: nil, validate: true)
  
  # Multiple query execution (multiplexing)
  def self.multiplex(queries, context: {}, max_complexity: nil, validate: true)
  
  # Analysis configuration
  def self.query_analyzer(analyzer_class)
  def self.analysis_engine(engine = nil)
  
  # Execution hooks
  def self.lazy_resolve(lazy_class, method_name)
  def self.after_lazy(value, &block)
end

# Multiplex execution
class GraphQL::Execution::Multiplex
  def initialize(schema:, queries:, context: {})
  def self.run_all(schema, query_options, **kwargs)
end

# Single query with options
result = MySchema.execute(
  query_string,
  variables: { id: "123" },
  context: { current_user: user },
  operation_name: "GetUser",
  only: [:query],  # Only allow queries, not mutations
  validate: true   # Validate before execution
)

# Multiplex execution (multiple queries in one request)
queries = [
  {
    query: "query GetUser($id: ID!) { user(id: $id) { name } }",
    variables: { id: "1" },
    operation_name: "GetUser"
  },
  {
    query: "query GetPosts { posts(limit: 5) { title } }",
    operation_name: "GetPosts"
  }
]

results = MySchema.multiplex(queries, context: { current_user: user })
results.each_with_index do |result, index|
  puts "Query #{index + 1}: #{result.to_json}"
end

# Custom lazy resolution
class MySchema < GraphQL::Schema
  # Define how to resolve lazy values
  lazy_resolve(Promise, :sync)
  lazy_resolve(Concurrent::Future, :value!)
end

def lazy_field
  # Return a lazy value that will be resolved later
  Promise.new { expensive_database_call }
end

class GraphQL::ExecutionError < GraphQL::Error
  def initialize(message, ast_node: nil, options: {})
  
  # Error information
  def message
  def path
  def locations
  def ast_node
  def extensions
  
  # Extensions for additional error data
  def extensions=(new_extensions)
end

# Schema error handling hooks
class GraphQL::Schema
  def self.type_error(err, context)
  def self.rescue_from(error_class, &block)
  def self.unauthorized_object(error)
  def self.unauthorized_field(error)
end

# Raising execution errors in resolvers
def user
  user = User.find_by(id: args[:id])
  
  unless user
    raise GraphQL::ExecutionError.new(
      "User not found",
      extensions: { 
        code: "NOT_FOUND",
        timestamp: Time.current.iso8601
      }
    )
  end
  
  user
end

# Schema-level error handling
class MySchema < GraphQL::Schema
  # Handle type resolution errors
  def self.type_error(err, context)
    GraphQL::ExecutionError.new(
      "Failed to resolve type: #{err.message}",
      extensions: { code: "TYPE_ERROR" }
    )
  end
  
  # Handle specific exception types
  rescue_from(ActiveRecord::RecordNotFound) do |err, obj, args, ctx, field|
    GraphQL::ExecutionError.new(
      "#{field.owner.name} not found",
      extensions: { code: "NOT_FOUND" }
    )
  end
  
  rescue_from(ActiveRecord::RecordInvalid) do |err, obj, args, ctx, field|
    GraphQL::ExecutionError.new(
      "Validation failed: #{err.record.errors.full_messages.join(', ')}",
      extensions: { 
        code: "VALIDATION_ERROR",
        details: err.record.errors.messages
      }
    )
  end
  
  # Handle authorization errors
  def self.unauthorized_object(err)
    GraphQL::ExecutionError.new(
      "Access denied",
      extensions: { code: "UNAUTHORIZED" }
    )
  end
end

# Collecting multiple errors
def resolve_with_multiple_errors
  errors = []
  results = []
  
  args[:ids].each do |id|
    begin
      results << fetch_item(id)
    rescue StandardError => e
      errors << GraphQL::ExecutionError.new(
        e.message,
        path: context.path + [results.length],
        extensions: { code: "FETCH_ERROR" }
      )
      results << nil
    end
  end
  
  errors.each { |error| context.add_error(error) }
  results
end