module Cancando

# File lib/cancando.rb, line 14
def abilities
  @abilities ||= Hash.new { |hash, k| hash[k] = [] }
end

# File lib/cancando.rb, line 22
def apply
  merge_and_grant(abilities, 'can') if abilities
  merge_and_grant(restrictions, 'cannot') if restrictions
end

# File lib/cancando.rb, line 6
def can_do(actions, resource, conditions = {})
  add(abilities, actions, resource, conditions)
end

# File lib/cancando.rb, line 10
def cannot_do(actions, resource, conditions = {})
  add(restrictions, actions, resource, conditions)
end

# File lib/cancando.rb, line 18
def restrictions
  @restrictions ||= Hash.new { |hash, k| hash[k] = [] }
end

# File lib/cancando.rb, line 29
def add(target, actions, resource, conditions)
  Array(actions).each do |action|
    target[resource] << {action: action, conditions: conditions}
  end
end

# File lib/cancando.rb, line 82
def equal_conditions?(conditions1, conditions2)
  conditions1.sort == conditions2.sort
end

# File lib/cancando.rb, line 100
def grant_abilities(abilities, resource, method)
  abilities.each do |ability|
    send(method, ability[:action], resource, ability[:conditions])
  end
end

# File lib/cancando.rb, line 45
def merge_abilities(abilities, ability_to_merge)
  if abilities.empty?
    abilities << ability_to_merge
    return
  end

  merged = false
  abilities.each do |ability|
    if same_actions?(ability[:action], ability_to_merge[:action]) &&
        same_single_condition_attr?(ability_to_merge[:conditions], ability[:conditions])

      merge_conditions(ability, ability_to_merge)
      merge_actions(ability, ability_to_merge)
      merged = true
      break
    elsif equal_conditions?(ability_to_merge[:conditions], ability[:conditions])
      merge_actions(ability, ability_to_merge)
      merged = true
      break
    end
  end

  abilities << ability_to_merge unless merged
end

# File lib/cancando.rb, line 95
def merge_actions(ability1, ability2)
  ability1[:action] = (Array(ability1[:action]) + Array(ability2[:action])).uniq
end

# File lib/cancando.rb, line 35
def merge_and_grant(abilities_to_merge, method)
  abilities_to_merge.each do |resource, abilities|
    merged_abilities = []
    abilities.each do |ability|
      merge_abilities(merged_abilities, ability)
    end
    grant_abilities(merged_abilities, resource, method)
  end
end

# File lib/cancando.rb, line 86
def merge_conditions(ability1, ability2)
  attr_value1 = ability1[:conditions].first[1]
  attr_value2 = ability2[:conditions].first[1]
  attr_name = ability2[:conditions].first[0]
  merged_value = (Array(attr_value1) + Array(attr_value2)).uniq

  ability1[:conditions][attr_name] = merged_value.length == 1 ? merged_value[0] : merged_value
end

# File lib/cancando.rb, line 70
def same_actions?(actions1, actions2)
  if actions1.is_a? Array
    actions1.include? actions2
  else
    actions1 == actions2
  end
end

# File lib/cancando.rb, line 78
def same_single_condition_attr?(conditions1, conditions2)
  conditions1.length == 1 && conditions1.keys == conditions2.keys
end