module Ancestry
  module InstanceMethods
    # Validate that the ancestors don't include itself
    def ancestry_exclude_self
      add_error_to_base "#{self.class.name.humanize} cannot be a descendant of itself." if ancestor_ids.include? self.id
    end

    # Update descendants with new ancestry
    def update_descendants_with_new_ancestry
      # Skip this if callbacks are disabled
      unless ancestry_callbacks_disabled?
        # If node is valid, not a new record and ancestry was updated ...
        if changed.include?(self.base_class.ancestry_column.to_s) && !new_record? && valid?
          # ... for each descendant ...
          descendants.each do |descendant|
            # ... replace old ancestry with new ancestry
            descendant.without_ancestry_callbacks do
              descendant.update_attribute(
                self.base_class.ancestry_column,
                descendant.read_attribute(descendant.class.ancestry_column).gsub(
                  /^#{self.child_ancestry}/,
                  if read_attribute(self.class.ancestry_column).blank? then id.to_s else "#{read_attribute self.class.ancestry_column }/#{id}" end
                )
              )
            end
          end
        end
      end
    end

    # Apply orphan strategy
    def apply_orphan_strategy
      # Skip this if callbacks are disabled
      unless ancestry_callbacks_disabled?
        # If this isn't a new record ...
        unless new_record?
          # ... make al children root if orphan strategy is rootify
          if self.base_class.orphan_strategy == :rootify
            descendants.each do |descendant|
              descendant.without_ancestry_callbacks do
                descendant.update_attribute descendant.class.ancestry_column, (if descendant.ancestry == child_ancestry then nil else descendant.ancestry.gsub(/^#{child_ancestry}\//, '') end)
              end
            end
          # ... destroy all descendants if orphan strategy is destroy
          elsif self.base_class.orphan_strategy == :destroy
            descendants.all.each do |descendant|
              descendant.without_ancestry_callbacks do
                descendant.destroy
              end
            end
          # ... throw an exception if it has children and orphan strategy is restrict
          elsif self.base_class.orphan_strategy == :restrict
            raise Ancestry::AncestryException.new('Cannot delete record because it has descendants.') unless is_childless?
          end
        end
      end
    end

    # The ancestry value for this record's children
    def child_ancestry
      # New records cannot have children
      raise Ancestry::AncestryException.new('No child ancestry for new record. Save record before performing tree operations.') if new_record?

      if self.send("#{self.base_class.ancestry_column}_was").blank? then id.to_s else "#{self.send "#{self.base_class.ancestry_column}_was"}/#{id}" end
    end

    # Ancestors
    def ancestor_ids
      read_attribute(self.base_class.ancestry_column).to_s.split('/').map { |id| cast_primary_key(id) }
    end

    def ancestor_conditions
      {self.base_class.primary_key => ancestor_ids}
    end

    def ancestors depth_options = {}
      self.base_class.scope_depth(depth_options, depth).ordered_by_ancestry.scoped :conditions => ancestor_conditions
    end

    def path_ids
      ancestor_ids + [id]
    end

    def path_conditions
      {self.base_class.primary_key => path_ids}
    end

    def path depth_options = {}
      self.base_class.scope_depth(depth_options, depth).ordered_by_ancestry.scoped :conditions => path_conditions
    end

    def depth
      ancestor_ids.size
    end

    def cache_depth
      write_attribute self.base_class.depth_cache_column, depth
    end

    # Parent
    def parent= parent
      write_attribute(self.base_class.ancestry_column, if parent.blank? then nil else parent.child_ancestry end)
    end

    def parent_id= parent_id
      self.parent = if parent_id.blank? then nil else self.base_class.find(parent_id) end
    end

    def parent_id
      if ancestor_ids.empty? then nil else ancestor_ids.last end
    end

    def parent
      if parent_id.blank? then nil else self.base_class.find(parent_id) end
    end

    # Root
    def root_id
      if ancestor_ids.empty? then id else ancestor_ids.first end
    end

    def root
      if root_id == id then self else self.base_class.find(root_id) end
    end

    def is_root?
      read_attribute(self.base_class.ancestry_column).blank?
    end

    # Children
    def child_conditions
      {self.base_class.ancestry_column => child_ancestry}
    end

    def children
      self.base_class.scoped :conditions => child_conditions
    end

    def child_ids
      children.all(:select => self.base_class.primary_key).map(&self.base_class.primary_key.to_sym)
    end

    def has_children?
      self.children.exists?({})
    end

    def is_childless?
      !has_children?
    end

    # Siblings
    def sibling_conditions
      {self.base_class.ancestry_column => read_attribute(self.base_class.ancestry_column)}
    end

    def siblings
      self.base_class.scoped :conditions => sibling_conditions
    end

    def sibling_ids
       siblings.all(:select => self.base_class.primary_key).collect(&self.base_class.primary_key.to_sym)
    end

    def has_siblings?
      self.siblings.count > 1
    end

    def is_only_child?
      !has_siblings?
    end

    # Descendants
    def descendant_conditions
      ["#{self.base_class.table_name}.#{self.base_class.ancestry_column} like ? or #{self.base_class.table_name}.#{self.base_class.ancestry_column} = ?", "#{child_ancestry}/%", child_ancestry]
    end

    def descendants depth_options = {}
      self.base_class.ordered_by_ancestry.scope_depth(depth_options, depth).scoped :conditions => descendant_conditions
    end

    def descendant_ids depth_options = {}
      descendants(depth_options).all(:select => self.base_class.primary_key).collect(&self.base_class.primary_key.to_sym)
    end

    # Subtree
    def subtree_conditions
      ["#{self.base_class.table_name}.#{self.base_class.primary_key} = ? or #{self.base_class.table_name}.#{self.base_class.ancestry_column} like ? or #{self.base_class.table_name}.#{self.base_class.ancestry_column} = ?", self.id, "#{child_ancestry}/%", child_ancestry]
    end

    def subtree depth_options = {}
      self.base_class.ordered_by_ancestry.scope_depth(depth_options, depth).scoped :conditions => subtree_conditions
    end

    def subtree_ids depth_options = {}
      subtree(depth_options).all(:select => self.base_class.primary_key).collect(&self.base_class.primary_key.to_sym)
    end

    # Callback disabling
    def without_ancestry_callbacks
      @disable_ancestry_callbacks = true
      yield
      @disable_ancestry_callbacks = false
    end

    def ancestry_callbacks_disabled?
      !!@disable_ancestry_callbacks
    end

  private

    # Workaround to support Rails 2
    def add_error_to_base error
      if rails_3
        errors[:base] << error
      else
        errors.add_to_base error
      end
    end

    def cast_primary_key(key)
      if primary_key_type == :string
        key
      else
        key.to_i
      end
    end

    def primary_key_type
      @primary_key_type ||= column_for_attribute(self.class.primary_key).type
    end
  end
end