class ActiveRecord::ConnectionAdapters::SQLite3Adapter

def self.database_exists?(config)
  config = config.symbolize_keys
  if config[:database] == ":memory:"
    true
  else
    database_file = defined?(Rails.root) ? File.expand_path(config[:database], Rails.root) : config[:database]
    File.exist?(database_file)
  end
end

def active?
  !@connection.closed?
end

def add_column(table_name, column_name, type, **options) # :nodoc:
  if invalid_alter_table_type?(type, options)
    alter_table(table_name) do |definition|
      definition.column(column_name, type, **options)
    end
  else
    super
  end
end

def add_reference(table_name, ref_name, **options) # :nodoc:
  super(table_name, ref_name, type: :integer, **options)
end

def all_foreign_keys_valid? # :nodoc:
  execute("PRAGMA foreign_key_check").blank?
end

def alter_table(
  table_name,
  foreign_keys = foreign_keys(table_name),
  check_constraints = check_constraints(table_name),
  **options
)
  altered_table_name = "a#{table_name}"
  caller = lambda do |definition|
    rename = options[:rename] || {}
    foreign_keys.each do |fk|
      if column = rename[fk.options[:column]]
        fk.options[:column] = column
      end
      to_table = strip_table_name_prefix_and_suffix(fk.to_table)
      definition.foreign_key(to_table, **fk.options)
    end
    check_constraints.each do |chk|
      definition.check_constraint(chk.expression, **chk.options)
    end
    yield definition if block_given?
  end
  transaction do
    disable_referential_integrity do
      move_table(table_name, altered_table_name, options.merge(temporary: true))
      move_table(altered_table_name, table_name, &caller)
    end
  end
end

def arel_visitor
  Arel::Visitors::SQLite.new(self)
end

def bind_params_length
  999
end

def build_insert_sql(insert) # :nodoc:
  sql = +"INSERT #{insert.into} #{insert.values_list}"
  if insert.skip_duplicates?
    sql << " ON CONFLICT #{insert.conflict_target} DO NOTHING"
  elsif insert.update_duplicates?
    sql << " ON CONFLICT #{insert.conflict_target} DO UPDATE SET "
    if insert.raw_update_sql?
      sql << insert.raw_update_sql
    else
      sql << insert.touch_model_timestamps_unless { |column| "#{column} IS excluded.#{column}" }
      sql << insert.updatable_columns.map { |column| "#{column}=excluded.#{column}" }.join(",")
    end
  end
  sql
end

def build_statement_pool
  StatementPool.new(self.class.type_cast_config_to_integer(@config[:statement_limit]))
end

def change_column(table_name, column_name, type, **options) # :nodoc:
  alter_table(table_name) do |definition|
    definition[column_name].instance_eval do
      self.type = aliased_types(type.to_s, type)
      self.options.merge!(options)
    end
  end
end

def change_column_default(table_name, column_name, default_or_changes) # :nodoc:
  default = extract_new_default_value(default_or_changes)
  alter_table(table_name) do |definition|
    definition[column_name].default = default
  end
end

def change_column_null(table_name, column_name, null, default = nil) # :nodoc:
  unless null || default.nil?
    exec_query("UPDATE #{quote_table_name(table_name)} SET #{quote_column_name(column_name)}=#{quote(default)} WHERE #{quote_column_name(column_name)} IS NULL")
  end
  alter_table(table_name) do |definition|
    definition[column_name].null = null
  end
end

def check_version # :nodoc:
  if database_version < "3.8.0"
    raise "Your version of SQLite (#{database_version}) is too old. Active Record supports SQLite >= 3.8."
  end
end

def configure_connection
  @connection.busy_timeout(self.class.type_cast_config_to_integer(@config[:timeout])) if @config[:timeout]
  execute("PRAGMA foreign_keys = ON", "SCHEMA")
end

def connect
  @connection = ::SQLite3::Database.new(
    @config[:database].to_s,
    @config.merge(results_as_hash: true)
  )
  configure_connection
end

def copy_table(from, to, options = {})
  from_primary_key = primary_key(from)
  options[:id] = false
  create_table(to, **options) do |definition|
    @definition = definition
    if from_primary_key.is_a?(Array)
      @definition.primary_keys from_primary_key
    end
    columns(from).each do |column|
      column_name = options[:rename] ?
        (options[:rename][column.name] ||
         options[:rename][column.name.to_sym] ||
         column.name) : column.name
      if column.has_default?
        type = lookup_cast_type_from_column(column)
        default = type.deserialize(column.default)
      end
      @definition.column(column_name, column.type,
        limit: column.limit, default: default,
        precision: column.precision, scale: column.scale,
        null: column.null, collation: column.collation,
        primary_key: column_name == from_primary_key
      )
    end
    yield @definition if block_given?
  end
  copy_table_indexes(from, to, options[:rename] || {})
  copy_table_contents(from, to,
    @definition.columns.map(&:name),
    options[:rename] || {})
end

def copy_table_contents(from, to, columns, rename = {})
  column_mappings = Hash[columns.map { |name| [name, name] }]
  rename.each { |a| column_mappings[a.last] = a.first }
  from_columns = columns(from).collect(&:name)
  columns = columns.find_all { |col| from_columns.include?(column_mappings[col]) }
  from_columns_to_copy = columns.map { |col| column_mappings[col] }
  quoted_columns = columns.map { |col| quote_column_name(col) } * ","
  quoted_from_columns = from_columns_to_copy.map { |col| quote_column_name(col) } * ","
  exec_query("INSERT INTO #{quote_table_name(to)} (#{quoted_columns})
             SELECT #{quoted_from_columns} FROM #{quote_table_name(from)}")
end

def copy_table_indexes(from, to, rename = {})
  indexes(from).each do |index|
    name = index.name
    if to == "a#{from}"
      name = "t#{name}"
    elsif from == "a#{to}"
      name = name[1..-1]
    end
    columns = index.columns
    if columns.is_a?(Array)
      to_column_names = columns(to).map(&:name)
      columns = columns.map { |c| rename[c] || c }.select do |column|
        to_column_names.include?(column)
      end
    end
    unless columns.empty?
      # index name can't be the same
      options = { name: name.gsub(/(^|_)(#{from})_/, "\\1#{to}_"), internal: true }
      options[:unique] = true if index.unique
      options[:where] = index.where if index.where
      options[:order] = index.orders if index.orders
      add_index(to, columns, **options)
    end
  end
end

def disable_referential_integrity # :nodoc:
  old_foreign_keys = query_value("PRAGMA foreign_keys")
  old_defer_foreign_keys = query_value("PRAGMA defer_foreign_keys")
  begin
    execute("PRAGMA defer_foreign_keys = ON")
    execute("PRAGMA foreign_keys = OFF")
    yield
  ensure
    execute("PRAGMA defer_foreign_keys = #{old_defer_foreign_keys}")
    execute("PRAGMA foreign_keys = #{old_foreign_keys}")
  end
end

def disconnect!
  super
  @connection.close rescue nil
end

def encoding
  @connection.encoding.to_s
end

def extract_default_function(default_value, default)
  default if has_default_function?(default_value, default)
end

def extract_value_from_default(default)
  case default
  when /^null$/i
    nil
  # Quoted types
  when /^'(.*)'$/m
    $1.gsub("''", "'")
  # Quoted types
  when /^"(.*)"$/m
    $1.gsub('""', '"')
  # Numeric types
  when /\A-?\d+(\.\d*)?\z/
    $&
  else
    # Anything else is blank or some function
    # and we can't know the value of that, so return nil.
    nil
  end
end

def foreign_keys(table_name)
  fk_info = exec_query("PRAGMA foreign_key_list(#{quote(table_name)})", "SCHEMA")
  fk_info.map do |row|
    options = {
      column: row["from"],
      primary_key: row["to"],
      on_delete: extract_foreign_key_action(row["on_delete"]),
      on_update: extract_foreign_key_action(row["on_update"])
    }
    ForeignKeyDefinition.new(table_name, row["table"], options)
  end
end

def get_database_version # :nodoc:
  SQLite3Adapter::Version.new(query_value("SELECT sqlite_version(*)", "SCHEMA"))
end

def has_default_function?(default_value, default)
  !default_value && %r{\w+\(.*\)|CURRENT_TIME|CURRENT_DATE|CURRENT_TIMESTAMP}.match?(default)
end

def initialize(connection, logger, connection_options, config)
  @memory_database = config[:database] == ":memory:"
  super(connection, logger, config)
  configure_connection
end

def initialize_type_map(m)
  super
  register_class_with_limit m, %r(int)i, SQLite3Integer
end

def invalid_alter_table_type?(type, options)
  type.to_sym == :primary_key || options[:primary_key] ||
    options[:null] == false && options[:default].nil?
end

def move_table(from, to, options = {}, &block)
  copy_table(from, to, options, &block)
  drop_table(from)
end

def native_database_types # :nodoc:
  NATIVE_DATABASE_TYPES
end

def primary_keys(table_name) # :nodoc:
  pks = table_structure(table_name).select { |f| f["pk"] > 0 }
  pks.sort_by { |f| f["pk"] }.map { |f| f["name"] }
end

def reconnect!
  super
  connect if @connection.closed?
end

def remove_column(table_name, column_name, type = nil, **options) # :nodoc:
  alter_table(table_name) do |definition|
    definition.remove_column column_name
    definition.foreign_keys.delete_if { |fk| fk.column == column_name.to_s }
  end
end

def remove_columns(table_name, *column_names, type: nil, **options) # :nodoc:
  alter_table(table_name) do |definition|
    column_names.each do |column_name|
      definition.remove_column column_name
    end
    column_names = column_names.map(&:to_s)
    definition.foreign_keys.delete_if { |fk| column_names.include?(fk.column) }
  end
end

def remove_index(table_name, column_name = nil, **options) # :nodoc:
  return if options[:if_exists] && !index_exists?(table_name, column_name, **options)
  index_name = index_name_for_remove(table_name, column_name, options)
  exec_query "DROP INDEX #{quote_column_name(index_name)}"
end

def rename_column(table_name, column_name, new_column_name) # :nodoc:
  column = column_for(table_name, column_name)
  alter_table(table_name, rename: { column.name => new_column_name.to_s })
  rename_column_indexes(table_name, column.name, new_column_name)
end

def rename_table(table_name, new_name)
  schema_cache.clear_data_source_cache!(table_name.to_s)
  schema_cache.clear_data_source_cache!(new_name.to_s)
  exec_query "ALTER TABLE #{quote_table_name(table_name)} RENAME TO #{quote_table_name(new_name)}"
  rename_table_indexes(table_name, new_name)
end

def requires_reloading?
  true
end

def shared_cache? # :nodoc:
  @config.fetch(:flags, 0).anybits?(::SQLite3::Constants::Open::SHAREDCACHE)
end

def supports_check_constraints?
  true
end

def supports_common_table_expressions?
  database_version >= "3.8.3"
end

def supports_concurrent_connections?
  !@memory_database
end

def supports_datetime_with_precision?
  true
end

def supports_ddl_transactions?
  true
end

def supports_explain?
  true
end

def supports_expression_index?
  database_version >= "3.9.0"
end

def supports_foreign_keys?
  true
end

def supports_index_sort_order?
  true
end

def supports_insert_on_conflict?
  database_version >= "3.24.0"
end

def supports_json?
  true
end

def supports_lazy_transactions?
  true
end

def supports_partial_index?
  true
end

def supports_savepoints?
  true
end

def supports_transaction_isolation?
  true
end

def supports_views?
  true
end

def table_structure(table_name)
  structure = exec_query("PRAGMA table_info(#{quote_table_name(table_name)})", "SCHEMA")
  raise(ActiveRecord::StatementInvalid, "Could not find table '#{table_name}'") if structure.empty?
  table_structure_with_collation(table_name, structure)
end

def table_structure_with_collation(table_name, basic_structure)
  collation_hash = {}
  sql = <<~SQL
    SELECT sql FROM
      (SELECT * FROM sqlite_master UNION ALL
       SELECT * FROM sqlite_temp_master)
    WHERE type = 'table' AND name = #{quote(table_name)}
  SQL
  # Result will have following sample string
  # CREATE TABLE "users" ("id" INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL,
  #                       "password_digest" varchar COLLATE "NOCASE");
  result = query_value(sql, "SCHEMA")
  if result
    # Splitting with left parentheses and discarding the first part will return all
    # columns separated with comma(,).
    columns_string = result.split("(", 2).last
    columns_string.split(",").each do |column_string|
      # This regex will match the column name and collation type and will save
      # the value in $1 and $2 respectively.
      collation_hash[$1] = $2 if COLLATE_REGEX =~ column_string
    end
    basic_structure.map do |column|
      column_name = column["name"]
      if collation_hash.has_key? column_name
        column["collation"] = collation_hash[column_name]
      end
      column
    end
  else
    basic_structure.to_a
  end
end

def translate_exception(exception, message:, sql:, binds:)
  # SQLite 3.8.2 returns a newly formatted error message:
  #   UNIQUE constraint failed: *table_name*.*column_name*
  # Older versions of SQLite return:
  #   column *column_name* is not unique
  if exception.message.match?(/(column(s)? .* (is|are) not unique|UNIQUE constraint failed: .*)/i)
    RecordNotUnique.new(message, sql: sql, binds: binds)
  elsif exception.message.match?(/(.* may not be NULL|NOT NULL constraint failed: .*)/i)
    NotNullViolation.new(message, sql: sql, binds: binds)
  elsif exception.message.match?(/FOREIGN KEY constraint failed/i)
    InvalidForeignKey.new(message, sql: sql, binds: binds)
  elsif exception.message.match?(/called on a closed database/i)
    ConnectionNotEstablished.new(exception)
  else
    super
  end
end

def type_map
  TYPE_MAP
end