ni_nitdoc: simplified github option

[nit.git] / src / debugger.nit

# This file is part of NIT ( http://www.nitlanguage.org ).
#
# Copyright 2013 Lucas Bajolet <lucas.bajolet@gmail.com>
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

# Debugging of a nit program using the NaiveInterpreter
module debugger

import breakpoint
intrude import naive_interpreter

redef class ToolContext
        # -d
        var opt_debugger_mode: OptionBool = new OptionBool("Launches the target program with the debugger attached to it", "-d")
        # -c
        var opt_debugger_autorun: OptionBool = new OptionBool("Launches the target program with the interpreter, such as when the program fails, the debugging prompt is summoned", "-c")

        redef init
        do
                super
                self.option_context.add_option(self.opt_debugger_mode)
                self.option_context.add_option(self.opt_debugger_autorun)
        end
end

redef class ModelBuilder
        # Execute the program from the entry point (Sys::main) of the `mainmodule`
        # `arguments` are the command-line arguments in order
        # REQUIRE that:
        #   1. the AST is fully loaded.
        #   2. the model is fully built.
        #   3. the instructions are fully analysed.
        fun run_debugger(mainmodule: MModule, arguments: Array[String])
        do
                var time0 = get_time
                self.toolcontext.info("*** START INTERPRETING ***", 1)

                var interpreter = new Debugger(self, mainmodule, arguments)

                init_naive_interpreter(interpreter, mainmodule)

                var time1 = get_time
                self.toolcontext.info("*** END INTERPRETING: {time1-time0} ***", 2)
        end

        fun run_debugger_autorun(mainmodule: MModule, arguments: Array[String])
        do
                var time0 = get_time
                self.toolcontext.info("*** START INTERPRETING ***", 1)

                var interpreter = new Debugger(self, mainmodule, arguments)
                interpreter.autocontinue = true

                init_naive_interpreter(interpreter, mainmodule)

                var time1 = get_time
                self.toolcontext.info("*** END INTERPRETING: {time1-time0} ***", 2)
        end
end

# The class extending `NaiveInterpreter` by adding debugging methods
class Debugger
        super NaiveInterpreter

        # Keeps the frame count in memory to find when to stop
        # and launch the command prompt after a step out call
        var step_stack_count = 1

        # Triggers a step over an instruction in a nit program
        var stop_after_step_over_trigger = true

        # Triggers a step out of an instruction
        var stop_after_step_out_trigger= false

        # Triggers a step in a instruction (enters a function
        # if the instruction is a function call)
        var step_in_trigger = false

        # HashMap containing the breakpoints bound to a file
        var breakpoints = new HashMap[String, HashSet[Breakpoint]]

        # Contains the current file
        var curr_file = ""

        # Aliases hashmap (maps an alias to a variable name)
        var aliases = new HashMap[String, String]

        # Set containing all the traced variables and their related frame
        private var traces = new HashSet[TraceObject]

        # Map containing all the positions for the positions of the arguments traced
        # In a function call
        private var fun_call_arguments_positions = new HashMap[Int, TraceObject]

        # Triggers the remapping of a trace object in the local context after a function call
        var aftermath = false

        # Used to prevent the case when the body of the function called is empty
        # If it is not, then, the remapping won't be happening
        var frame_count_aftermath = 1

        # Auto continues the execution until the end or until an error is encountered
        var autocontinue = false

        #######################################################################
        ##                  Execution of statement function                  ##
        #######################################################################

        # Main loop, every call to a debug command is done here
        redef fun stmt(n: nullable AExpr)
        do
                if n == null then return

                var frame = self.frame
                var old = frame.current_node
                frame.current_node = n

                if not self.autocontinue then
                        if not n isa ABlockExpr then
                                steps_fun_call(n)

                                breakpoint_check(n)

                                check_funcall_and_traced_args(n)

                                remap(n)

                                check_if_vars_are_traced(n)
                        end
                end

                n.stmt(self)
                frame.current_node = old
        end

        # Encpasulates the behaviour for step over/out
        private fun steps_fun_call(n: AExpr)
        do
                if self.stop_after_step_over_trigger then
                        if self.frames.length <= self.step_stack_count then
                                n.debug("Execute stmt {n.to_s}")
                                while process_debug_command(gets) do end
                        end
                else if self.stop_after_step_out_trigger then
                        if frames.length < self.step_stack_count then
                                n.debug("Execute stmt {n.to_s}")
                                while process_debug_command(gets) do end
                        end
                else if step_in_trigger then
                        n.debug("Execute stmt {n.to_s}")
                        while process_debug_command(gets) do end
                end
        end

        # Checks if a breakpoint is encountered, and launches the debugging prompt if true
        private fun breakpoint_check(n: AExpr)
        do
                var currFileNameSplit = self.frame.current_node.location.file.filename.to_s.split_with("/")

                self.curr_file = currFileNameSplit[currFileNameSplit.length-1]

                var breakpoint = find_breakpoint(curr_file, n.location.line_start)

                if breakpoints.keys.has(curr_file) and breakpoint != null then

                        breakpoint.check_in

                        if not breakpoint.is_valid
                        then
                                remove_breakpoint(curr_file, n.location.line_start)
                        end

                        n.debug("Execute stmt {n.to_s}")
                        while process_debug_command(gets) do end
                end
        end

        # Check if a variable of current expression is traced
        # Then prints and/or breaks for command prompt
        private fun check_if_vars_are_traced(n: AExpr)
        do
                var identifiers_in_instruction = get_identifiers_in_current_instruction(n.location.text)

                for i in identifiers_in_instruction do
                        var variable = seek_variable(i, frame)
                        for j in self.traces do
                                if j.is_variable_traced_in_frame(i, frame) then
                                        n.debug("Traced variable {i} used")
                                        if j.break_on_encounter then while process_debug_command(gets) do end
                                        break
                                end
                        end
                end
        end

        # Function remapping all the traced objects to match their name in the local context
        private fun remap(n: AExpr)
        do
                if self.aftermath then

                        # Trace every argument variable pre-specified
                        if self.frame_count_aftermath < frames.length and fun_call_arguments_positions.length > 0 then

                                var ids_in_fun_def = get_identifiers_in_current_instruction(get_function_arguments(frame.mpropdef.location.text))

                                for i in fun_call_arguments_positions.keys do
                                        self.fun_call_arguments_positions[i].add_frame_variable(frame, ids_in_fun_def[i])
                                end
                        end

                        self.aftermath = false
                end
        end

        # If the current instruction is a function call
        # We analyse its signature and the position of traced arguments if the call
        # For future remapping when inside the function
        private fun check_funcall_and_traced_args(n: AExpr) do
                # If we have a function call, we need to see if any of the arguments is traced (including the caller)
                # if it is, next time we face an instruction, we'll trace the local version on the traced variable in the next frame
                if n isa ACallExpr then
                        self.aftermath = true
                        self.frame_count_aftermath = frames.length
                        fun_call_arguments_positions.clear
                        var fun_arguments = get_identifiers_in_current_instruction(get_function_arguments(n.location.text))

                        for i in self.traces do
                                for j in [0 .. fun_arguments.length - 1] do
                                        if i.is_variable_traced_in_frame(fun_arguments[j],frame) then
                                                fun_call_arguments_positions[j] = i
                                        end
                                end
                        end
                end
        end

        #######################################################################
        ##                   Processing commands functions                   ##
        #######################################################################

        # Takes a user command as a parameter
        #
        # Returns a boolean value, representing whether or not to
        # continue reading commands from the console input
        fun process_debug_command(command:String): Bool
        do
                # For lisibility
                print "\n"

                # Kills the current program
                if command == "kill" then
                        abort
                # Step-out command
                else if command == "finish"
                then
                        return step_out
                # Step-in command
                else if command == "s"
                then
                        return step_in
                # Step-over command
                else if command == "n" then
                        return step_over
                # Continues execution until the end
                else if command == "c" then
                        return continue_exec
                else
                        var parts_of_command = command.split_with(' ')
                        # Shows the value of a variable in the current frame
                        if parts_of_command[0] == "p" or parts_of_command[0] == "print" then
                                print_command(parts_of_command)
                        # Places a breakpoint on line x of file y
                        else if parts_of_command[0] == "break" or parts_of_command[0] == "b"
                        then
                                process_place_break_fun(parts_of_command)
                        # Places a temporary breakpoint on line x of file y
                        else if parts_of_command[0] == "tbreak" and (parts_of_command.length == 2 or parts_of_command.length == 3)
                        then
                                process_place_tbreak_fun(parts_of_command)
                        # Removes a breakpoint on line x of file y
                        else if parts_of_command[0] == "d" or parts_of_command[0] == "delete" then
                                process_remove_break_fun(parts_of_command)
                        # Sets an alias for a variable
                        else if parts_of_command.length == 3 and parts_of_command[1] == "as"
                        then
                                add_alias(parts_of_command[0], parts_of_command[2])
                        # Modifies the value of a variable in the current frame
                        else if parts_of_command.length >= 3 and parts_of_command[1] == "=" then
                                process_mod_function(parts_of_command)
                        # Traces the modifications on a variable
                        else if parts_of_command.length >= 2 and parts_of_command[0] == "trace" then
                                process_trace_command(parts_of_command)
                        # Untraces the modifications on a variable
                        else if parts_of_command.length == 2 and parts_of_command[0] == "untrace" then
                                process_untrace_command(parts_of_command)
                        # Lists all the commands available
                        else
                                list_commands
                        end
                end
                return true
        end

        #######################################################################
        ##               Processing specific command functions               ##
        #######################################################################

        # Sets the flags to step-over an instruction in the current file
        fun step_over: Bool
        do
                self.step_stack_count = frames.length
                self.stop_after_step_over_trigger = true
                self.stop_after_step_out_trigger = false
                self.step_in_trigger = false
                return false
        end

        #Sets the flags to step-out of a function
        fun step_out: Bool
        do
                self.stop_after_step_over_trigger = false
                self.stop_after_step_out_trigger = true
                self.step_in_trigger = false
                self.step_stack_count = frames.length
                return false
        end

        # Sets the flags to step-in an instruction
        fun step_in: Bool
        do
                self.step_in_trigger = true
                self.stop_after_step_over_trigger = false
                self.stop_after_step_out_trigger = false
                return false
        end

        # Sets the flags to continue execution
        fun continue_exec: Bool
        do
                self.stop_after_step_over_trigger = false
                self.stop_after_step_out_trigger = false
                self.step_in_trigger = false
                return false
        end

        # Prints the demanded variable in the command
        #
        # The name of the variable in in position 1 of the array 'parts_of_command'
        fun print_command(parts_of_command: Array[String])
        do
                if parts_of_command[1] == "*" then
                        var map_of_instances = frame.map

                        var keys = map_of_instances.iterator

                        print "Variables collection : \n"

                        for instance in map_of_instances.keys do
                                print "Variable {instance.to_s}, Instance {map_of_instances[instance].to_s}"
                        end

                        print "\nEnd of current instruction \n"
                else if parts_of_command[1] == "stack" then
                        print self.stack_trace
                else if parts_of_command[1].has('[') and parts_of_command[1].has(']') then
                        process_array_command(parts_of_command)
                else
                        var instance = seek_variable(get_real_variable_name(parts_of_command[1]), frame)

                        if instance != null
                        then
                                print_instance(instance)
                        else
                                print "Cannot find variable {parts_of_command[1]}"
                        end
                end
        end

        # Processes the input string to know where to put a breakpoint
        fun process_place_break_fun(parts_of_command: Array[String])
        do
                var bp = get_breakpoint_from_command(parts_of_command)
                if bp != null then
                        place_breakpoint(bp)
                else
                        list_commands
                end
        end

        # Returns a breakpoint containing the informations stored in the command
        fun get_breakpoint_from_command(parts_of_command: Array[String]): nullable Breakpoint
        do
                if parts_of_command[1].is_numeric then
                        return new Breakpoint(parts_of_command[1].to_i, curr_file)
                else if parts_of_command.length >= 3 and parts_of_command[2].is_numeric then
                        return new Breakpoint(parts_of_command[2].to_i, parts_of_command[1])
                else
                        return null
                end
        end

        # Processes the command of removing a breakpoint on specified line and file
        fun process_remove_break_fun(parts_of_command: Array[String])
        do
                if parts_of_command[1].is_numeric then
                        remove_breakpoint(self.curr_file, parts_of_command[1].to_i)
                else if parts_of_command.length >= 3 and parts_of_command[2].is_numeric then
                        remove_breakpoint(parts_of_command[1], parts_of_command[2].to_i)
                else
                        list_commands
                end
        end

        # Processes an array print command
        fun process_array_command(parts_of_command: Array[String])
        do
                var index_of_first_brace = parts_of_command[1].index_of('[')
                var variable_name = get_real_variable_name(parts_of_command[1].substring(0,index_of_first_brace))
                var braces = parts_of_command[1].substring_from(index_of_first_brace)

                var indexes = remove_braces(braces)

                var index_array = new Array[Array[Int]]

                if indexes != null then
                        for index in indexes do
                                var temp_indexes_array = process_index(index)
                                if temp_indexes_array != null then
                                        index_array.push(temp_indexes_array)
                                        #print index_array.last
                                end
                        end
                end

                var instance = seek_variable(variable_name, frame)

                if instance != null then
                        print_nested_collection(instance, index_array, 0, variable_name, "")
                else
                        print "Cannot find variable {variable_name}"
                end
        end

        # Processes the modification function to modify a variable dynamically
        #
        # Command of type variable = value
        fun process_mod_function(parts_of_command: Array[String])
        do
                parts_of_command[0] = get_real_variable_name(parts_of_command[0])
                var parts_of_variable = parts_of_command[0].split_with(".")

                if parts_of_variable.length > 1 then
                        var last_part = parts_of_variable.pop
                        var first_part = parts_of_command[0].substring(0,parts_of_command[0].length - last_part.length - 1)
                        var papa = seek_variable(first_part, frame)

                        if papa != null and papa isa MutableInstance then
                                var attribute = get_attribute_in_mutable_instance(papa, last_part)

                                if attribute != null then
                                        modify_argument_of_complex_type(papa, attribute, parts_of_command[2])
                                end
                        end
                else
                        var target = seek_variable(parts_of_variable[0], frame)
                        if target != null then
                                modify_in_frame(target, parts_of_command[2])
                        end
                end
        end

        # Processes the untrace variable command
        #
        # Command pattern : "untrace variable"
        fun process_untrace_command(parts_of_command: Array[String])
        do
                var variable_name = get_real_variable_name(parts_of_command[1])
                if untrace_variable(variable_name) then
                        print "Untraced variable {parts_of_command[1]}"
                else
                        print "{parts_of_command[1]} is not traced"
                end
        end

        # Processes the trace variable command
        #
        # Command pattern : "trace variable [break/print]"
        fun process_trace_command(parts_of_command: Array[String])
        do
                var variable_name = get_real_variable_name(parts_of_command[1])
                var breaker:Bool

                if seek_variable(variable_name, frame) == null then
                        print "Cannot find a variable called {parts_of_command[1]}"
                        return
                end

                if parts_of_command.length == 3 then
                        if parts_of_command[2] == "break" then
                                breaker = true
                        else
                                breaker = false
                        end
                else
                        breaker = false
                end

                trace_variable(variable_name, breaker)

                print "Successfully tracing {parts_of_command[1]}"
        end

        #######################################################################
        ##                    Trace Management functions                     ##
        #######################################################################

        # Effectively untraces the variable called *variable_name*
        #
        # Returns true if the variable exists, false otherwise
        private fun untrace_variable(variable_name: String): Bool
        do
                var to_remove: nullable TraceObject = null
                for i in self.traces do
                        if i.is_variable_traced_in_frame(variable_name, frame) then
                                to_remove = i
                        end
                end

                if to_remove != null then
                        self.traces.remove(to_remove)
                        return true
                else
                        return false
                end
        end

        # Effectively traces the variable *variable_name* either in print or break mode depending on the value of breaker (break if true, print if false)
        #
        private fun trace_variable(variable_name: String, breaker: Bool)
        do
                for i in self.traces do
                        if i.is_variable_traced_in_frame(variable_name, frame) then
                                print "This variable is already traced"
                                return
                        end
                end

                var trace_object: TraceObject

                if breaker then
                        trace_object = new TraceObject(true)
                else
                        trace_object = new TraceObject(false)
                end

                # We trace the current variable found for the current frame
                trace_object.add_frame_variable(self.frame, variable_name)

                var position_of_variable_in_arguments = get_position_of_variable_in_arguments(frame, variable_name)

                # Start parsing the frames starting with the parent of the current one, until the highest
                # When the variable traced is declared locally, the loop stops
                for i in [1 .. frames.length-1] do

                        # If the variable was reported to be an argument of the previous frame
                        if position_of_variable_in_arguments != -1 then

                                var local_name = get_identifiers_in_current_instruction(get_function_arguments(frames[i].current_node.location.text))[position_of_variable_in_arguments]

                                position_of_variable_in_arguments = get_position_of_variable_in_arguments(frames[i], local_name)

                                trace_object.add_frame_variable(frames[i], local_name)
                        else
                                break
                        end
                end

                self.traces.add(trace_object)
        end

        # If the variable *variable_name* is an argument of the function being executed in the frame *frame*
        # The function returns its position in the arguments
        # Else, it returns -1
        private fun get_position_of_variable_in_arguments(frame: Frame, variable_name: String): Int
        do
                var identifiers = get_identifiers_in_current_instruction(get_function_arguments(frame.mpropdef.location.text))
                for i in [0 .. identifiers.length-1] do
                        # If the current traced variable is an argument of the current function, we trace its parent (at least)
                        if identifiers[i] == variable_name then return i
                end
                return -1
        end

        # Gets all the identifiers of an instruction (uses the rules of Nit as of Mar 05 2013)
        #
        fun get_identifiers_in_current_instruction(instruction: AbstractString): Array[String]
        do
                var result_array = new Array[String]
                var instruction_buffer = new Buffer

                var trigger_char_escape = false
                var trigger_string_escape = false
                var trigger_concat_in_string = false

                for i in instruction do
                        if trigger_char_escape then
                                if i == '\'' then trigger_char_escape = false
                        else if trigger_string_escape then
                                if i == '{' then
                                        trigger_concat_in_string = true
                                        trigger_string_escape = false
                                else if i == '\"' then trigger_string_escape = false
                        else
                                if i.is_alphanumeric or i == '_' then
                                        instruction_buffer.add(i)
                                else if i == '.' then
                                        if instruction_buffer.is_numeric or (instruction_buffer[0] >= 'A' and instruction_buffer[0] <= 'Z') then
                                                instruction_buffer.clear
                                        else
                                                result_array.push(instruction_buffer.to_s)
                                                instruction_buffer.add(i)
                                        end
                                else if i == '\'' then
                                        trigger_char_escape = true
                                else if i == '\"' then
                                        trigger_string_escape = true
                                else if i == '}' then
                                        trigger_concat_in_string = false
                                        trigger_string_escape = true
                                else
                                        if instruction_buffer.length > 0 and not instruction_buffer.is_numeric and not (instruction_buffer[0] >= 'A' and instruction_buffer[0] <= 'Z') then result_array.push(instruction_buffer.to_s)
                                        instruction_buffer.clear
                                end
                        end
                end

                if instruction_buffer.length > 0 and not instruction_buffer.is_numeric and not (instruction_buffer[0] >= 'A' and instruction_buffer[0] <= 'Z') then result_array.push(instruction_buffer.to_s)

                return result_array
        end

        # Takes a function call or declaration and strips all but the arguments
        #
        fun get_function_arguments(function: AbstractString): String
        do
                var buf = new Buffer
                var trigger_copy = false

                for i in function do
                        if i == ')' then break
                        if trigger_copy then buf.add(i)
                        if i == '(' then trigger_copy = true
                end

                return buf.to_s
        end

        #######################################################################
        ##                    Alias management functions                     ##
        #######################################################################

        # Adds a new alias to the tables
        fun add_alias(var_represented: String, alias: String)
        do
                self.aliases[alias] = var_represented
        end

        # Gets the real name of a variable hidden by an alias
        fun get_variable_name_by_alias(alias: String): nullable String
        do
                if self.aliases.keys.has(alias) then
                        return self.aliases[alias]
                end

                return null
        end

        # Gets the variable named by name, whether it is an alias or not
        fun get_real_variable_name(name: String): String
        do
                var explode_string = name.split_with(".")
                var final_string = new Buffer
                for i in explode_string do
                        var alias_resolved = get_variable_name_by_alias(i)
                        if alias_resolved != null then
                                final_string.append(get_real_variable_name(alias_resolved))
                        else
                                final_string.append(i)
                        end
                        final_string.append(".")
                end

                return final_string.substring(0,final_string.length-1).to_s
        end

        #######################################################################
        ##                         Print functions                           ##
        #######################################################################

        # Prints an object instance and its attributes if it has some
        #
        # If it is a primitive type, its value is directly printed
        fun print_instance(instance: Instance)
        do
                print "Printing innards of a variable"

                if instance isa MutableInstance then
                        var attributes = instance.attributes
                        print "Object : {instance}"

                        for current_attribute in attributes.keys do
                                print "Attribute : {current_attribute.to_s} \nValeur : {attributes[current_attribute].to_s}"
                        end
                else
                        print "Found variable {instance}"
                end

                print "Stopping printing innards of a variable"
        end

        # Prints the attributes demanded in a SequenceRead
        # Used recursively to print nested collections
        fun print_nested_collection(instance: Instance, indexes: Array[Array[Int]], depth: Int, variable_name: String, depth_string: String)
        do
                var collection: nullable SequenceRead[Object] = null
                var real_collection_length: nullable Int = null

                if instance isa MutableInstance then
                        real_collection_length = get_collection_instance_real_length(instance)
                        collection = get_primary_collection(instance)
                end

                if collection != null and real_collection_length != null then
                        for i in indexes[depth] do
                                if i >= 0 and i < real_collection_length then
                                        if depth == indexes.length-1 then
                                                print "{variable_name}{depth_string}[{i}] = {collection[i]}"
                                        else
                                                var item_i = collection[i]

                                                if item_i isa MutableInstance then
                                                        print_nested_collection(item_i, indexes, depth+1, variable_name, depth_string+"[{i}]")
                                                else
                                                        print "The item at {variable_name}{depth_string}[{i}] is not a collection"
                                                        print item_i
                                                end
                                        end
                                else
                                        print "Out of bounds exception : i = {i} and collection_length = {real_collection_length.to_s}"

                                        if i < 0 then
                                                continue
                                        else if i >= real_collection_length then
                                                break
                                        end
                                end
                        end
                else
                        if collection == null then
                                print "Cannot find {variable_name}{depth_string}"
                        else if real_collection_length != null then
                                print "Cannot find attribute length in {instance}"
                        else
                                print "Unknown error."
                                abort
                        end
                end
        end

        #######################################################################
        ##                  Variable Exploration functions                   ##
        #######################################################################

        # Seeks a variable from the current frame called 'variable_path', can introspect complex objects using function get_variable_in_mutable_instance
        private fun seek_variable(variable_path: String, frame: Frame): nullable Instance
        do
                var full_variable = variable_path.split_with(".")

                var full_variable_iterator = full_variable.iterator

                var first_instance = get_variable_in_frame(full_variable_iterator.item, frame)

                if first_instance == null then  return null

                if full_variable.length <= 1 then return first_instance

                full_variable_iterator.next

                if not (first_instance isa MutableInstance and full_variable_iterator.is_ok) then return null

                return get_variable_in_mutable_instance(first_instance, full_variable_iterator)
        end

        # Gets a variable 'variable_name' contained in the frame 'frame'
        private fun get_variable_in_frame(variable_name: String, frame: Frame): nullable Instance
        do
                if variable_name == "self" then
                        if frame.arguments.length >= 1 then return frame.arguments.first
                end

                var map_of_instances = frame.map

                for key in map_of_instances.keys do
                        if key.to_s == variable_name then
                                return map_of_instances[key]
                        end
                end

                return null
        end

        # Gets an attribute 'attribute_name' contained in variable 'variable'
        fun get_attribute_in_mutable_instance(variable: MutableInstance, attribute_name: String): nullable MAttribute
        do
                var map_of_attributes = variable.attributes

                for key in map_of_attributes.keys do
                        if key.to_s.substring_from(1) == attribute_name then
                                return key
                        end
                end

                return null
        end

        # Recursive function, returns the variable described by 'total_chain'
        fun get_variable_in_mutable_instance(variable: MutableInstance, iterator: Iterator[String]): nullable Instance
        do
                var attribute = get_attribute_in_mutable_instance(variable, iterator.item)

                if attribute == null then return null

                iterator.next

                if iterator.is_ok then
                        var new_variable = variable.attributes[attribute]
                        if new_variable isa MutableInstance then
                                return get_variable_in_mutable_instance(new_variable, iterator)
                        else
                                return null
                        end
                else
                        return variable.attributes[attribute]
                end
        end

        #######################################################################
        ##                     Array exploring functions                     ##
        #######################################################################

        # Gets the length of a collection
        # Used by the debugger, else if we call Collection.length, it returns the capacity instead
        fun get_collection_instance_real_length(collection: MutableInstance): nullable Int
        do
                var collection_length_attribute = get_attribute_in_mutable_instance(collection, "length")

                var real_collection_length: nullable Int = null

                if collection_length_attribute != null then
                        var primitive_length_instance = collection.attributes[collection_length_attribute]
                        if primitive_length_instance isa PrimitiveInstance[Int] then
                                return primitive_length_instance.val
                        end
                end

                return null
        end

        # Processes the indexes of a print array call
        # Returns an array containing all the indexes demanded
        fun process_index(index_string: String): nullable Array[Int]
        do
                var from_end_index = index_string.index_of('.')
                var to_start_index = index_string.last_index_of('.')

                if from_end_index != -1 and to_start_index != -1 then
                        var index_from_string = index_string.substring(0,from_end_index)
                        var index_to_string = index_string.substring_from(to_start_index+1)

                        if index_from_string.is_numeric and index_to_string.is_numeric then
                                var result_array = new Array[Int]

                                var index_from = index_from_string.to_i
                                var index_to = index_to_string.to_i

                                for i in [index_from..index_to] do
                                        result_array.push(i)
                                end

                                return result_array
                        end
                else
                        if index_string.is_numeric
                        then
                                var result_array = new Array[Int]

                                result_array.push(index_string.to_i)

                                return result_array
                        else
                                return null
                        end
                end

                return null
        end

        # Gets a collection in a MutableInstance
        fun get_primary_collection(container: MutableInstance): nullable SequenceRead[Object]
        do
                var items_of_array = get_attribute_in_mutable_instance(container, "items")
                if items_of_array != null then
                        var array = container.attributes[items_of_array]

                        if array isa PrimitiveInstance[Object] then
                                var sequenceRead_final = array.val
                                if sequenceRead_final isa SequenceRead[Object] then
                                        return sequenceRead_final
                                end
                        end
                end

                return null
        end

        # Removes the braces '[' ']' in a print array command
        # Returns an array containing their content
        fun remove_braces(braces: String): nullable Array[String]
        do
                var buffer = new Buffer

                var result_array = new Array[String]

                var number_of_opening_brackets = 0
                var number_of_closing_brackets = 0

                var last_was_opening_bracket = false

                for i in braces do
                        if i == '[' then
                                if last_was_opening_bracket then
                                        return null
                                end

                                number_of_opening_brackets += 1
                                last_was_opening_bracket = true
                        else if i == ']' then
                                if not last_was_opening_bracket then
                                        return null
                                end

                                result_array.push(buffer.to_s)
                                buffer.clear
                                number_of_closing_brackets += 1
                                last_was_opening_bracket = false
                        else if i.is_numeric or i == '.' then
                                buffer.append(i.to_s)
                        else if not i == ' ' then
                                return null
                        end
                end

                if number_of_opening_brackets != number_of_closing_brackets then
                        return null
                end

                return result_array
        end

        #######################################################################
        ##                   Breakpoint placing functions                    ##
        #######################################################################

        # Places a breakpoint on line 'line_to_break' for file 'file_to_break'
        fun place_breakpoint(breakpoint: Breakpoint)
        do
                if not self.breakpoints.keys.has(breakpoint.file) then
                        self.breakpoints[breakpoint.file] = new HashSet[Breakpoint]
                end
                if find_breakpoint(breakpoint.file, breakpoint.line) == null then
                        self.breakpoints[breakpoint.file].add(breakpoint)
                        print "Breakpoint added on line {breakpoint.line} for file {breakpoint.file}"
                else
                        print "Breakpoint already present on line {breakpoint.line} for file {breakpoint.file}"
                end
        end

        #Places a breakpoint that will trigger once and be destroyed afterwards
        fun process_place_tbreak_fun(parts_of_command: Array[String])
        do
                var bp = get_breakpoint_from_command(parts_of_command)
                if bp != null
                then
                        bp.set_max_breaks(1)
                        place_breakpoint(bp)
                else
                        list_commands
                end
        end

        #######################################################################
        ##                  Breakpoint removing functions                    ##
        #######################################################################

        # Removes a breakpoint on line 'line_to_break' for file 'file_to_break'
        fun remove_breakpoint(file_to_break: String, line_to_break: Int)
        do
                if self.breakpoints.keys.has(file_to_break) then
                        var bp = find_breakpoint(file_to_break, line_to_break)

                        if bp != null then
                                self.breakpoints[file_to_break].remove(bp)
                                print "Breakpoint removed on line {line_to_break} for file {file_to_break}"
                                return
                        end
                end

                print "No breakpoint existing on line {line_to_break} for file {file_to_break}"
        end

        #######################################################################
        ##                  Breakpoint searching functions                   ##
        #######################################################################

        # Finds a breakpoint for 'file' and 'line' in the class HashMap
        fun find_breakpoint(file: String, line: Int): nullable Breakpoint
        do
                if self.breakpoints.keys.has(file)
                then
                        for i in self.breakpoints[file]
                        do
                                if i.line == line
                                then
                                        return i
                                end
                        end
                end

                return null
        end

        #######################################################################
        ##                  Runtime modification functions                   ##
        #######################################################################

        # Modifies the value of a variable contained in a frame
        fun modify_in_frame(variable: Instance, value: String)
        do
                var new_variable = get_variable_of_type_with_value(variable.mtype.to_s, value)
                if new_variable != null
                then
                        var keys = frame.map.keys
                        for key in keys
                        do
                                if frame.map[key] == variable
                                then
                                        frame.map[key] = new_variable
                                end
                        end
                end
        end

        # Modifies the value of a variable contained in a MutableInstance
        fun modify_argument_of_complex_type(papa: MutableInstance, attribute: MAttribute, value: String)
        do
                var final_variable = papa.attributes[attribute]
                var type_of_variable = final_variable.mtype.to_s
                var new_variable = get_variable_of_type_with_value(type_of_variable, value)
                if new_variable != null
                then
                        papa.attributes[attribute] = new_variable
                end
        end

        #######################################################################
        ##                   Variable generator functions                    ##
        #######################################################################

        # Returns a new variable of the type 'type_of_variable' with a value of 'value'
        fun get_variable_of_type_with_value(type_of_variable: String, value: String): nullable Instance
        do
                if type_of_variable == "Int" then
                        return get_int(value)
                else if type_of_variable == "Float" then
                        return get_float(value)
                else if type_of_variable == "Bool" then
                        return get_bool(value)
                else if type_of_variable == "Char" then
                        return get_char(value)
                end

                return null
        end

        # Returns a new int instance with value 'value'
        fun get_int(value: String): nullable Instance
        do
                if value.is_numeric then
                        return int_instance(value.to_i)
                else
                        return null
                end
        end

        # Returns a new float instance with value 'value'
        fun get_float(value:String): nullable Instance
        do
                if value.is_numeric then
                        return float_instance(value.to_f)
                else
                        return null
                end
        end

        # Returns a new char instance with value 'value'
        fun get_char(value: String): nullable Instance
        do
                if value.length >= 1 then
                        return char_instance(value[0])
                else
                        return null
                end
        end

        # Returns a new bool instance with value 'value'
        fun get_bool(value: String): nullable Instance
        do
                if value.to_lower == "true" then
                        return self.true_instance
                else if value.to_lower == "false" then
                        return self.false_instance
                else
                        print "Invalid value, a boolean must be set at \"true\" or \"false\""
                        return null
                end
        end

        #######################################################################
        ##                     Command listing function                      ##
        #######################################################################

        # Lists the commands available when using the debugger
        fun list_commands
        do
                print "\nCommand not recognized\n"
                print "Commands accepted : \n"
                print "[break/b] line : Adds a breakpoint on line *line_nb* of the current file\n"
                print "[break/b] file_name line_nb : Adds a breakpoint on line *line_nb* of file *file_name* \n"
                print "[p/print] variable : [p/print] * shows the status of all the variables\n"
                print "[p/print] variable[i] : Prints the value of the variable contained at position *i* in SequenceRead collection *variable*\n"
                print "[p/print] variable[i..j]: Prints the value of all the variables contained between positions *i* and *j* in SequenceRead collection *variable*\n"
                print "[p/print] stack: Prints a stack trace at current instruction\n"
                print "Note : The arrays can be multi-dimensional (Ex : variable[i..j][k] will print all the values at position *k* of all the SequenceRead collections contained between positions *i* and *j* in SequenceRead collection *variable*)\n"
                print "s : steps in on the current function\n"
                print "n : steps-over the current instruction\n"
                print "finish : steps out of the current function\n"
                print "variable as alias : Adds an alias called *alias* for the variable *variable*"
                print "An alias can reference another alias\n"
                print "variable = value : Sets the value of *variable* to *value*\n"
                print "[d/delete] line_nb : Removes a breakpoint on line *line_nb* of the current file \n"
                print "[d/delete] file_name line_nb : Removes a breakpoint on line *line_nb* of file *file_name* \n"
                print "trace variable_name [break/print] : Traces the uses of the variable you chose to trace by printing the statement it appears in or by breaking on each use."
                print "untrace variable_name : Removes the trace on the variable you chose to trace earlier in the program"
                print "kill : kills the current program (Exits with an error and stack trace)\n"
        end

end

# Traces the modifications of an object linked to a certain frame
private class TraceObject

        # Map of the local names bound to a frame
        var trace_map: HashMap[Frame, String]
        # Decides if breaking or printing statement when the variable is encountered
        var break_on_encounter: Bool

        init(break_on_encounter: Bool)
        do
                trace_map = new HashMap[Frame, String]
                self.break_on_encounter = break_on_encounter
        end

        # Adds the local alias for a variable and the frame bound to it
        fun add_frame_variable(frame: Frame, variable_name: String)
        do
                self.trace_map[frame] = variable_name
        end

        # Checks if the prompted variable is traced in the specified frame
        fun is_variable_traced_in_frame(variable_name: String, frame: Frame): Bool
        do
                if self.trace_map.has_key(frame) then
                        if self.trace_map[frame] == variable_name then
                                return true
                        end
                end

                return false
        end

end

redef class ANode

        # Breaks automatically when encountering an error
        # Permits the injunction of commands before crashing
        redef private fun fatal(v: NaiveInterpreter, message: String)
        do
                if v isa Debugger then
                        print "An error was encountered, the program will stop now."
                        self.debug(message)
                        while v.process_debug_command(gets) do end
                end

                super
        end
end