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Pure functional JDBC layer for Scala.

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package doobie.syntax

import doobie.util.param.Param
import doobie.util.pos.Pos
import doobie.util.fragment.Fragment
import shapeless.ProductArgs

/** Module defining the `sql` string interpolator. */
object string {

  /**
   * String interpolator for SQL literals. An expression of the form `sql".. $a ... $b ..."` with
   * interpolated values of type `A` and `B` (which must have `[[Param]]` instances, derived
   * automatically from `Meta` via `Atom`) yields a value of type `[[Fragment]]`.
   */
  implicit class SqlInterpolator(private val sc: StringContext)(implicit pos: Pos) {

    private def mkFragment[A](a: A, token: Boolean)(implicit ev: Param[A]): Fragment = {
      val sql = sc.parts.mkString("", "?", if (token) " " else "")
      Fragment(sql, a, Some(pos))(ev.composite)
    }

    /**
     * Interpolator for a statement fragment that can contain interpolated values. When inserted
     * into the final SQL statement this fragment will be followed by a space. This is normally
     * what you want, and it makes it easier to concatenate fragments because you don't need to
     * think about intervening whitespace. If you do not want this behavior, use `fr0`.
     */
    object fr extends ProductArgs {
      def applyProduct[A: Param](a: A): Fragment = mkFragment(a, true)
    }

    /** Alternative name for the `fr0` interpolator. */
    final val sql: fr0.type = fr0

    /**
     * Interpolator for a statement fragment that can contain interpolated values. Unlike `fr` no
     * attempt is made to be helpful with respect to whitespace.
     */
    object fr0 extends ProductArgs {
      def applyProduct[A: Param](a: A): Fragment = mkFragment(a, false)
    }

  }

}