export interface withDecodingDefault<S extends Constraint, R = never> extends decodeTo<S, optional<toEncoded<S>>, R> {
  readonly "Rebuild": withDecodingDefault<S, R>
}

/**
 * Wraps the `Encoded` side with `optional` (key absent **or** `undefined`)
 * and provides a default `Encoded` value when the field is missing or
 * `undefined` during decoding.
 *
 * **When to use**
 *
 * Use when the default is expressed in the encoded representation, before the
 * field's decoding transformation runs.
 *
 * **Details**
 *
 * The default value is specified in terms of the `Encoded` type (before any
 * decoding transformations).
 *
 * Options:
 *
 * - `encodingStrategy`:
 *   - `"passthrough"` (default): include the value in the encoded output.
 *   - `"omit"`: omit the key from the encoded output.
 *
 * **Example** (Providing a default for an optional field value)
 *
 * ```ts
 * import { Effect, Schema } from "effect"
 *
 * const MySchema = Schema.Struct({
 *   name: Schema.String.pipe(Schema.optional, Schema.withDecodingDefault(Effect.succeed("anonymous")))
 * })
 *
 * const result = Schema.decodeUnknownSync(MySchema)({ name: undefined })
 * // result: { name: "anonymous" }
 * ```
 *
 * @see {@link withDecodingDefaultKey} for the key-level variant (key absent only, not `undefined`)
 * @see {@link withDecodingDefaultType} for the variant where the default is a `Type` value
 * @category decoding
 * @since 3.10.0
 */
export function withDecodingDefault<S extends Constraint, R = never>(
  defaultValue: Effect.Effect<S["Encoded"], SchemaError, R>,
  options?: DecodingDefaultOptions
) {
  const encode = options?.encodingStrategy === "omit" ? SchemaGetter.omit() : SchemaGetter.passthrough()
  return (self: S): withDecodingDefault<S, R> => {
    return optional(toEncoded(self)).pipe(decodeTo(self, {
      decode: SchemaGetter.withDefault(toIssueEffect(defaultValue)),
      encode
    }))
  }
}