ioquatix/build-environment

# Copyright, 2012, by Samuel G. D. Williams. <http://www.codeotaku.com>
# 
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
# 
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
# 
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.

module Build
    # This is the basic environment data structure which is essentially a linked list of hashes. It is primarily used for organising build configurations across a wide range of different sub-systems, e.g. platform configuration, target configuration, local project configuration, etc.
    class Environment
        def initialize(parent = nil, values = nil, name: nil, &block)
            @parent = parent
            @values = (values || {}).to_h
            @update = block
            
            @name = name
        end
        
        def == other
            self.equal?(other) or
                self.class == other.class and
                @parent == other.parent and
                @values == other.values and
                @update == other.update and
                @name == other.name
        end
        
        def eql?(other)
            self == other
        end
        
        def hash
            @parent.hash ^ @values.hash ^ @update.hash ^ @name.hash
        end
        
        attr :parent
        attr :values
        attr :update
        attr :name
        
        def dup(parent: @parent, values: @values, update: @update, name: @name)
            self.class.new(parent, values.dup, name: name, &update)
        end
        
        def freeze
            return self if frozen?
            
            @parent.freeze
            @values.freeze
            @update.freeze
            
            super
        end
        
        def lookup(name)
            if @values.include? name
                self
            elsif @parent
                @parent.lookup(name)
            end
        end
        
        def include?(key)
            if @values.include?(key)
                true
            elsif @parent
                @parent.include?(key)
            end
        end
        
        def size
            @values.size + (@parent ? @parent.size : 0)
        end
        
        def fetch(key, *default, &block)
            if environment = lookup(key)
                return environment.values[key]
            elsif block_given?
                yield(key, *default)
            elsif !default.empty?
                return default.first
            else
                raise KeyError.new("Environment missing #{key}")
            end
        end
        
        def [](key)
            environment = lookup(key)
            
            environment ? environment.values[key] : nil
        end
        
        def []=(key, value)
            @values[key] = value
        end
        
        def to_s
            buffer = String.new("\#<#{self.class} ")
            
            if @name
                buffer << @name.inspect << ' '
            end
            
            if @update
                buffer << @update.source_location.join(':') << ' '
            end
            
            buffer << @values.to_s << '>'
            
            return buffer
        end
    end
end