# encoding: UTF-8
# frozen_string_literal: true

# Requirements
# =======================================================================

# Stdlib
# -----------------------------------------------------------------------
require 'pathname'

# Deps
# -----------------------------------------------------------------------
require 'nrser'
require 'nrser/core_ext/object'


# Project / Package
# -----------------------------------------------------------------------


# Refinements
# =======================================================================

require 'nrser/refinements/types'
using NRSER::Types


# Definitions
# =======================================================================

# @todo document Locd::Config class.
class Locd::Config
  
  # Constants
  # ===================================================================
  
  # Absolute path to the default config file (`//config/default.yml`).
  # 
  # Has to be defined as a constant because no other config is loaded
  # before it and it contains the ENV var prefix.
  # 
  # @return [Pathname]
  # 
  DEFAULT_CONFIG_PATH = Locd::ROOT / 'config' / 'default.yml'
  
  
  # Absolute path to the dev override config, which will be loaded
  # last if it exists.
  # 
  # @return [Pathname]
  # 
  DEV_CONFIG_PATH = Locd::ROOT / 'dev' / 'config.yml'
  
  
  # What to split string keys into key path segments on.
  # 
  # @return [String]
  # 
  KEY_SEPARATOR = '.'
  
  
  # Attributes
  # ============================================================================
  
  # Absolute path to the built-in default configuration file in use.
  # 
  # @return [Pathname]
  #     
  attr_reader :default_config_path
  
  
  # Constructor
  # ===================================================================
  
  # Instantiate a new `Locd::Config`.
  def initialize  default_config_path: DEFAULT_CONFIG_PATH,
                  dev_config_path: DEV_CONFIG_PATH
    @default_config_path = default_config_path.to_pn
    @dev_config_path = dev_config_path.to_pn
    
    @from_files = {}
    
    load_file default_config_path
    
    if user_config_path.exist?
      load_file user_config_path
    end
    
    if dev_config_path && dev_config_path.exist?
      load_file dev_config_path
    end
  end # #initialize
  
  
  # Instance Methods
  # ===================================================================
  
  protected
  # ========================================================================
    
    
    # @todo Document load_file method.
    # 
    # @param [type] arg_name
    #   @todo Add name param description.
    # 
    # @return [return_type]
    #   @todo Document return value.
    # 
    def load_file path
      bnd = binding
      
      path.
        to_pn.
        read.
        thru { |contents|
            YAML.load contents
        }.
        map_leaves { |path, leaf|
          case leaf
          when String
            bnd.erb leaf
          else
            leaf
          end
        }.
        thru { |tree|
          @from_files.deep_merge! tree
        }
      
      nil
    end # #load_file
    
  public # end protected ***************************************************
  
  
  def key_path_for *key
    key.flat_map { |k| k.to_s.split KEY_SEPARATOR }
  end
  
  
  def from_files *key, type: nil
    key_path = key_path_for *key
    value = @from_files.dig Locd::GEM_NAME, *key_path
    
    if value.nil?
      nil
    else
      parse_and_check value, type: type
    end
  end
  
  
  def env_key_for *key
    [
      from_files( :namespace, :env, type: t.non_empty_str ),
      *key_path_for( *key )
    ].join( '_' ).upcase
  end
  
  
  def parse_and_check value, type: nil
    return value if type.nil?
    
    if value.is_a?( String ) && type.has_from_s?
      type.from_s value
    else
      type.check value
    end
  end
  
  
  def from_env *key, type: nil
    env_key = env_key_for *key
    
    value = ENV[env_key]
    
    case value
    when nil, ''
      nil
    else
      parse_and_check value, type: type
    end
  end
  
  
  def get *key, type: nil, default: nil
    env_value = from_env *key, type: type
    return env_value unless env_value.nil?
    
    files_value = from_files *key, type: type
    return files_value unless files_value.nil?
    
    parse_and_check default, type: type
  end
  
  alias_method :[], :get
  
  
  def to_h
    @from_files.merge \
      "locd" => @from_files["locd"].map_leaves { |key_path, value|
        env_value = from_env *key_path
        
        if env_value.nil?
          value
        else
          env_value
        end
      }
  end
  
  
  # @return [Pathname]
  #   Absolute path to Loc'd home directory (it's workspace).
  #   Directory may not exist, or may be something else like a file.
  #   
  def home_dir
    self[:home, type: t.abs_path].to_pn
  end
  
  
  def log_dir
    self[
      :log_dir,
      type: t.abs_path,
      default: (home_dir / 'log')
    ]
  end
  
  
  # @return [Pathname]
  #   Absolute path to the user config file, which may not exist, but
  #   will be loaded if it does.
  # 
  def user_config_path
    home_dir / 'config.yml'
  end
  
end # class Locd::Config