# SQLite3 wrapper
# Copyright (C) 2023  Nguyễn Gia Phong
#
# This file if part of hybring.
#
# Hybring is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# Hybring is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU Affero General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with hybring.  If not, see <https://www.gnu.org/licenses/>.

@[Link("sqlite3")]
lib SQLite
  OK = 0
  ROW = 100
  DONE = 101

  type Database = Void*
  type Statement = Void*

  fun errstr = sqlite3_errstr(rc : LibC::Int) : LibC::Char*
  fun open = sqlite3_open(filename : LibC::Char*, db : Database*) : LibC::Int
  fun prepare = sqlite3_prepare(db : Database, query : LibC::Char*,
                                length : LibC::Int, stmt : Statement*,
                                query_tail : LibC::Char**) : LibC::Int
  fun step = sqlite3_step(stmt : Statement) : Int32
  fun column_text = sqlite3_column_text(stmt : Statement,
                                        col : LibC::Int) : LibC::Char*
  fun column_int = sqlite3_column_int(stmt : Statement,
                                      col : LibC::Int) : LibC::Int
  fun finalize = sqlite3_finalize(stmt : Statement) : LibC::Int
  fun close = sqlite3_close(db : Database) : LibC::Int
end

class Database
  MIGRATIONS = [""] # migration #0 is reserved for schema initialization
  SCHEMA = "CREATE TABLE member (
    id INTEGER PRIMARY KEY,
    nick TEXT NOT NULL UNIQUE,
    opennic TEXT NOT NULL UNIQUE,
    icann TEXT NOT NULL UNIQUE)";

  class Statement
    def initialize(db, query)
      bytes = query.to_slice
      Database.check SQLite.prepare db.ref, bytes, bytes.size,
                                    out @ref, out @tail
    end

    def ref
      @ref
    end

    def step : LibC::Int
      SQLite.step @ref
    end

    def finalize
      Database.check SQLite.finalize @ref
    end
  end

  class Column
    def initialize(stmt : SQLite::Statement, i : LibC::Int)
      @stmt = stmt
      @i = i
    end

    def int
      SQLite.column_int @stmt, @i
    end

    def text
      String.new SQLite.column_text @stmt, @i
    end
  end

  class Row
    def initialize(stmt : SQLite::Statement)
      @stmt = stmt
    end

    def [](i : LibC::Int)
      Column.new @stmt, i
    end
  end

  def initialize(path : String)
    Database.check SQLite.open path, out @ref
    self.exec "PRAGMA user_version" do |row|
      version = row[0].int
      raise "negative schema version" if version < 0
      raise "schema version newer than supported" if version > MIGRATIONS.size
      if version == 0
        self.exec SCHEMA do end
        self.exec "PRAGMA user_version = #{MIGRATIONS.size}" do end
      end
    end
  end

  def ref
    @ref
  end

  def exec(query : String)
    stmt = Statement.new self, query
    loop do
      rc = stmt.step
      case rc
      when SQLite::ROW
        yield Row.new stmt.ref
      when SQLite::DONE
        break
      else
        Database.check rc
      end
    end
  end

  def finalize
    Database.check SQLite.close @ref
  end
end

def Database.check(rc : LibC::Int)
  raise String.new SQLite.errstr rc if rc != SQLite::OK
end