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# The **Scope** class regulates lexical scoping within CoffeeScript. As you
# generate code, you create a tree of scopes in the same shape as the nested
# function bodies. Each scope knows about the variables declared within it,
# and has a reference to its parent enclosing scope. In this way, we know which
# variables are new and need to be declared with `var`, and which are shared
# with the outside.
# Import the helpers we plan to use.
{extend, last} = require './helpers'
exports.Scope = class Scope
# The top-level **Scope** object.
@root: null
# Initialize a scope with its parent, for lookups up the chain,
# as well as a reference to the **Block** node it belongs to, which is
# where it should declare its variables, and a reference to the function that
# it wraps.
constructor: (@parent, @expressions, @method) ->
@variables = [{name: 'arguments', type: 'arguments'}]
@positions = {}
Scope.root = this unless @parent
# Adds a new variable or overrides an existing one.
add: (name, type, immediate) ->
return @parent.add name, type, immediate if @shared and not immediate
if @positions, name
@variables[@positions[name]].type = type
@positions[name] = @variables.push({name, type}) - 1
# Look up a variable name in lexical scope, and declare it if it does not
# already exist.
find: (name, options) ->
return yes if @check name, options
@add name, 'var'
# Reserve a variable name as originating from a function parameter for this
# scope. No `var` required for internal references.
parameter: (name) ->
return if @shared and @parent.check name, yes
@add name, 'param'
# Just check to see if a variable has already been declared, without reserving,
# walks up to the root scope.
check: (name, immediate) ->
found = !!@type(name)
return found if found or immediate
!!@parent?.check name
# Generate a temporary variable name at the given index.
temporary: (name, index) ->
if name.length > 1
'_' + name + if index > 1 then index else ''
'_' + (index + parseInt name, 36).toString(36).replace /\d/g, 'a'
# Gets the type of a variable.
type: (name) ->
return v.type for v in @variables when is name
# If we need to store an intermediate result, find an available name for a
# compiler-generated variable. `_var`, `_var2`, and so on...
freeVariable: (name, reserve=true) ->
index = 0
index++ while @check((temp = @temporary name, index))
@add temp, 'var', yes if reserve
# Ensure that an assignment is made at the top of this scope
# (or at the top-level scope, if requested).
assign: (name, value) ->
@add name, {value, assigned: yes}, yes
@hasAssignments = yes
# Does this scope have any declared variables?
hasDeclarations: ->
# Return the list of variables first declared in this scope.
declaredVariables: ->
realVars = []
tempVars = []
for v in @variables when v.type is 'var'
(if is '_' then tempVars else realVars).push
realVars.sort().concat tempVars.sort()
# Return the list of assignments that are supposed to be made at the top
# of this scope.
assignedVariables: ->
"#{} = #{v.type.value}" for v in @variables when v.type.assigned
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