require "uri"

# The DB module is a unified interface to database access.
# Database dialects is supported by custom database driver shards.
# Check [manastech/crystal-sqlite3](https://github.com/manastech/crystal-sqlite3) for example.
#
# Drivers implementors check `Driver` class.
#
# Currently a *single connection* to the database is stablished.
# In the future a connection pool and transaction support will be available.
#
# ### Usage
#
# Assuming `crystal-sqlite3` is included a sqlite3 database can be opened with `#open`.
#
# ```
# db = DB.open "sqlite3:./path/to/db/file.db"
# db.close
# ```
#
# If a block is given to `#open` the database is closed automatically
#
# ```
# DB.open "sqlite3:./file.db" do |db|
#   # work with db
# end # db is closed
# ```
#
# In the code above `db` is a `Database`. Methods available for querying it are described in `QueryMethods`.
#
# Three kind of statements can be performed:
# 1. `Database#exec` waits no response from the database.
# 2. `Database#scalar` reads a single value of the response.
# 3. `Database#query` returns a ResultSet that allows iteration over the rows in the response and column information.
#
# All of the above methods allows parametrised query. Either positional or named arguments.
#
# Check a full working version:
#
# ```
# require "db"
# require "sqlite3"
#
# DB.open "sqlite3:./file.db" do |db|
#   db.exec "create table contacts (name string, age integer)"
#   db.exec "insert into contacts values (?, ?)", "John Doe", 30
#
#   args = [] of DB::Any
#   args << "Sarah"
#   args << 33
#   db.exec "insert into contacts values (?, ?)", args
#
#   puts "max age:"
#   puts db.scalar "select max(age) from contacts" # => 33
#
#   puts "contacts:"
#   db.query "select name, age from contacts order by age desc" do |rs|
#     puts "#{rs.column_name(0)} (#{rs.column_name(1)})"
#     # => name (age)
#     rs.each do
#       puts "#{rs.read(String)} (#{rs.read(Int32)})"
#       # => Sarah (33)
#       # => John Doe (30)
#     end
#   end
# end
# ```
#
module DB
  # Types supported to interface with database driver.
  # These can be used in any `ResultSet#read` or any `Database#query` related
  # method to be used as query parameters
  TYPES = [Nil, String, Int32, Int64, Float32, Float64, Bytes]

  # See `DB::TYPES` in `DB`. `Any` is a union of all types in `DB::TYPES`
  {% begin %}
    alias Any = Union({{*TYPES}})
  {% end %}

  # Result of a `#exec` statement.
  record ExecResult, rows_affected : Int64, last_insert_id : Int64

  # :nodoc:
  def self.driver_class(driver_name) : Driver.class
    @@drivers.not_nil![driver_name]
  end

  # Registers a driver class for a given *driver_name*.
  # Should be called by drivers implementors only.
  def self.register_driver(driver_name, driver_class : Driver.class)
    @@drivers ||= {} of String => Driver.class
    @@drivers.not_nil![driver_name] = driver_class
  end

  # Opens a database using the specified *uri*.
  # The scheme of the *uri* determines the driver to use.
  # Returned database must be closed by `Database#close`.
  # If a block is used the database is yielded and closed automatically.
  def self.open(uri : URI | String)
    build_database(uri)
  end

  # Same as `#open` but the database is yielded and closed automatically.
  def self.open(uri : URI | String, &block)
    db = build_database(uri)
    begin
      yield db
    ensure
      db.close
    end
  end

  private def self.build_database(connection_string : String)
    build_database(URI.parse(connection_string))
  end

  private def self.build_database(uri : URI)
    Database.new(driver_class(uri.scheme).new, uri)
  end
end

require "./db/query_methods"
require "./db/disposable"
require "./db/database"
require "./db/driver"
require "./db/connection"
require "./db/statement"
require "./db/result_set"
require "./db/error"
require "./db/mapping"