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.

require 'digest/md5'

module Build
    class Environment
        def to_h
            hash = {}
            
            # Flatten this chain of environments:
            flatten_to_hash(hash)
            
            # Evaluate all items to their respective object value:
            evaluator = Evaluator.new(hash)
            
            # Evaluate all the individual environment values so that they are flat:
            Hash[hash.map{|key, value| [key, evaluator.object_value(value)]}]
        end
        
        def evaluator
            Evaluator.new(self)
        end
        
        def evaluate(**options)
            self.class.new(nil, self.to_h, **options)
        end
        
        def flatten(**options)
            hash = {}
            
            flatten_to_hash(hash)
            
            options[:name] ||= self.name
            
            return self.class.new(nil, hash, **options)
        end
        
        def defined
            @values.select{|name,value| Define === value}
        end
        
        def checksum(digester: Digest::SHA1.new)
            checksum_recursively(digester)
            
            return digester.hexdigest
        end
        
        protected
        
        def sorted_keys
            @values.keys.sort_by(&:to_s)
        end
        
        def checksum_recursively(digester)
            sorted_keys.each do |key|
                digester.update(key.to_s)
                
                case value = @values[key]
                when Proc
                    digester.update(value.source_location.join)
                else
                    digester.update(value.to_s)
                end
            end
            
            @parent.checksum_recursively(digester) if @parent
        end
        
        def update_hash(hash)
            @values.each do |key, value|
                previous = hash[key]
                
                if Replace === value
                    # Replace the parent value
                    hash[key] = value
                elsif Default === value
                    # Update the parent value if not defined.
                    hash[key] = previous || value
                elsif Array === previous
                    # Merge with the parent value
                    hash[key] = previous + Array(value)
                elsif OpenStruct === value
                    hash[key] = value.to_h
                else
                    hash[key] = value
                end
            end
            
            return self
        end
        
        # Apply the update function to this environment.
        def update!
            construct!(self, &@update)
            @update = nil
            
            return self
        end
        
        # We fold in the ancestors one at a time from oldest to youngest.
        def flatten_to_hash(hash)
            if parent = @parent
                parent = parent.flatten_to_hash(hash)
            end
            
            if @update
                self.dup(parent: parent).update!.update_hash(hash)
            else
                self.update_hash(hash)
            end
        end
    end
end