import * as Array from "effect/Array";
import * as Effect from "effect/Effect";
import * as QueryStreamKey from "./QueryStreamKey";
import * as SchemaIssue from "effect/SchemaIssue";
import * as Match from "effect/Match";
import * as Schema from "effect/Schema";
import * as SchemaGetter from "effect/SchemaGetter";
import * as QueryStreamKeyLayout from "./QueryStreamKeyLayout";
import * as QueryStreamKeyValues from "./QueryStreamKeyValues";

// Serialized labels are a cursor boundary representation. They include every
// runtime position but do not preserve implicitness.
const RuntimeLabels = Schema.Array(Schema.String);
const RuntimeLabelsEquivalence = Schema.toEquivalence(RuntimeLabels);
const positionRuntimeLabel = Match.type<QueryStreamKeyLayout.Position>().pipe(
  Match.tagsExhaustive({
    Visible: ({ label }) => label,
    ImplicitId: () => "_id",
  }),
);

/**
 * @experimental
 */
export const QueryStreamCursor = Schema.Struct({
  runtimeLabels: RuntimeLabels,
  keyValues: QueryStreamKeyValues.QueryStreamKeyValues,
}).check(
  Schema.makeFilter(
    (cursor) => cursor.keyValues.length === cursor.runtimeLabels.length,
    { message: "key values and runtime labels must have the same length" },
  ),
);

/**
 * @experimental
 */
export interface QueryStreamCursor extends Schema.Schema.Type<
  typeof QueryStreamCursor
> {}

/**
 * @experimental
 */
export const END_CURSOR = "[]";

/**
 * Bind cursor string encoding and decoding to a layout.
 *
 * @experimental
 */
export const fromKeyLayout = (
  keyLayout: QueryStreamKeyLayout.QueryStreamKeyLayout,
) => {
  const runtimeLabels = Array.map(
    QueryStreamKeyLayout.positions(keyLayout),
    positionRuntimeLabel,
  );
  return Schema.fromJsonString(QueryStreamCursor)
    .check(
      Schema.makeFilter(
        (cursor) =>
          RuntimeLabelsEquivalence(cursor.runtimeLabels, runtimeLabels),
        { message: "Cursor runtime labels do not match the stream" },
      ),
    )
    .pipe(
      Schema.decodeTo(
        Schema.declare(QueryStreamKey.isComplete).check(
          Schema.makeFilter(
            (key) => QueryStreamKeyLayout.Equivalence(key.layout, keyLayout),
            { message: "Cursor key does not belong to the stream layout" },
          ),
        ),
        {
          decode: SchemaGetter.transformEffect((cursor, options) =>
            Effect.fromResult(
              QueryStreamKey.complete(keyLayout, cursor.keyValues),
            ).pipe(
              Effect.mapError(
                (error) =>
                  new SchemaIssue.InvalidValue(
                    { message: error.message },
                    cursor.keyValues,
                    options,
                  ),
              ),
            ),
          ),
          encode: SchemaGetter.transformEffect((key) =>
            QueryStreamCursor.makeEffect({
              runtimeLabels,
              keyValues: key.values,
            }),
          ),
        },
      ),
    );
};