require 'set'

module CocoaPodsKeys
  class KeyMaster

    attr_accessor :name, :interface, :implementation

    def initialize(keyring)
      @keys = Hash[keyring.keychain_data.map { |(key, value)| [key[0].downcase + key[1..-1], value] }]
      @name = keyring.code_name + 'Keys'
      @used_indexes = Set.new
      @indexed_keys = {}
      @data = generate_data
      @interface = generate_interface
      @implementation = generate_implementation
    end

    def generate_data

      # Generate a base64 hash string that is ~25 times the length of all keys

      @data_length = @keys.values.map(&:length).reduce(:+) * (20 + rand(10))
      data = `head -c #{@data_length} /dev/random | base64 | head -c #{@data_length}`
      length = data.length

      # Swap the characters within the hashed string with the characters from
      # the keyring values. Then store that index in a index-ed copy of the values.

      @keys.each do |key, value|
        @indexed_keys[key] = []

        value.chars.each_with_index do |char, char_index|
          loop do

            index = rand data.length
            unless @used_indexes.include?(index)
              data[index] = char

              @used_indexes << index
              @indexed_keys[key][char_index] = index
              break
            end

          end
        end
      end

      data
    end

    def generate_interface
      erb = <<-SOURCE
//
// Generated by CocoaPods-Keys
// on #{Time.now.strftime("%d/%m/%Y")}
// For more information see https://github.com/cocoapods/cocoapods-keys
//

#import <Foundation/NSString.h>

@interface <%= @name %> : NSObject
<% @keys.each do |key, value| %>
- (NSString *)<%= key %>;<% end %>

@end
SOURCE

      render_erb(erb)
    end

    def generate_implementation
      require 'digest'

      erb = <<-SOURCE
//
// Generated by CocoaPods-Keys
// on #{Time.now.strftime("%d/%m/%Y")}
// For more information see https://github.com/cocoapods/cocoapods-keys
//

#import <objc/runtime.h>
#import "<%= @name %>.h"

#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wincomplete-implementation"

@implementation <%= @name %>

#pragma clang diagnostic pop

+ (BOOL)resolveInstanceMethod:(SEL)name
{
  NSString *key = NSStringFromSelector(name);
  NSString * (*implementation)(<%= name %> *, SEL) = NULL;
<% @keys.each do |key, value| %>
  if ([key isEqualToString:@"<%= key %>"]) {
    implementation = _podKeys<%= Digest::MD5.hexdigest(key) %>;
  }
<% end %>
  if (!implementation) {
    return [super resolveInstanceMethod:name];
  }

  return class_addMethod([self class], name, (IMP)implementation, "@@:");
}
<% @keys.each do |key, value| %>
static NSString *_podKeys<%= Digest::MD5.hexdigest(key) %>(<%= name %> *self, SEL _cmd)
{
  <% if @indexed_keys.length > 0 %>
    <% if @indexed_keys[key].length > 0 %>
      char cString[<%= @indexed_keys[key].length + 1 %>] = { <%= key_data_arrays[key] %>, '\\0' };
    <% else %>
      char cString[1] = { '\\0' };
    <% end %>
    return [NSString stringWithCString:cString encoding:NSUTF8StringEncoding];
  <% else %>
    return @"";
  <% end %>
}
<% end %>

static char <%= name %>Data[<%= @data_length %>] = "<%= @data %>";

@end
SOURCE

      render_erb(erb)
    end

    :private

    def render_erb(erb)
      require 'erb'
      ERB.new(erb).result(binding)
    end

    def key_data_arrays
      Hash[@indexed_keys.map {|key, value| [key, value.map { |i| name + "Data[#{i}]" }.join(', ')]}]
    end

  end
end