import * as qbusiness from "@distilled.cloud/aws/qbusiness";
import * as Data from "effect/Data";
import * as Effect from "effect/Effect";
import * as Schedule from "effect/Schedule";
import * as EffectStream from "effect/Stream";
import { Unowned } from "../../AdoptPolicy.ts";
import { isResolved } from "../../Diff.ts";
import { createPhysicalName } from "../../PhysicalName.ts";
import * as Provider from "../../Provider.ts";
import { Resource } from "../../Resource.ts";
import {
  createInternalTags,
  diffTags,
  hasAlchemyTags,
  type Tags,
} from "../../Tags.ts";
import type { Providers } from "../Providers.ts";

export type IndexStatus = qbusiness.IndexStatus;
export type IndexType = qbusiness.IndexType;

export interface IndexProps {
  /**
   * The identifier of the Amazon Q Business application the index attaches
   * to. Changing it replaces the index.
   */
  applicationId: string;
  /**
   * Display name of the index.
   * @default ${app}-${stage}-${id}
   */
  displayName?: string;
  /**
   * A description of the index.
   */
  description?: string;
  /**
   * The index tier — `STARTER` (single AZ) or `ENTERPRISE` (multi AZ).
   * Changing it replaces the index.
   * @default "STARTER"
   */
  type?: IndexType;
  /**
   * Provisioned storage capacity units. Each unit stores 20,000 documents.
   * @default 1 unit
   */
  capacityConfiguration?: qbusiness.IndexCapacityConfiguration;
  /**
   * Configuration for document metadata attributes (search/display
   * behavior).
   */
  documentAttributeConfigurations?: qbusiness.DocumentAttributeConfiguration[];
  /**
   * Tags to associate with the index.
   */
  tags?: Record<string, string>;
}

export interface Index extends Resource<
  "AWS.QBusiness.Index",
  IndexProps,
  {
    /**
     * Service-assigned unique identifier of the index (unique within its
     * application).
     */
    indexId: string;
    /**
     * The identifier of the application the index belongs to.
     */
    applicationId: string;
    /**
     * ARN of the index.
     */
    indexArn: string;
    /**
     * The index's display name.
     */
    displayName: string;
    /**
     * The provisioned index tier.
     */
    type: IndexType | undefined;
    /**
     * Current lifecycle status of the index.
     */
    status: IndexStatus | undefined;
    /**
     * Current tags reported for the index.
     */
    tags: Record<string, string>;
  },
  never,
  Providers
> {}

/**
 * An Amazon Q Business index — the document store that data sources sync
 * content into and retrievers query.
 *
 * :::caution
 * An index bills hourly per provisioned capacity unit from the moment it
 * becomes `ACTIVE`. Destroy test indexes promptly.
 * :::
 * ### Creating Indexes
 * **Example:** Starter Index
 * ```typescript
 * import * as AWS from "alchemy/AWS";
 *
 * const index = yield* AWS.QBusiness.Index("Docs", {
 *   applicationId: app.applicationId,
 * });
 * ```
 *
 * **Example:** Enterprise Index with Extra Capacity
 * ```typescript
 * const index = yield* AWS.QBusiness.Index("Docs", {
 *   applicationId: app.applicationId,
 *   type: "ENTERPRISE",
 *   capacityConfiguration: { units: 2 },
 * });
 * ```
 *
 * @resource
 */
export const Index = Resource<Index>("AWS.QBusiness.Index");

const createDisplayName = (
  id: string,
  props: { displayName?: string | undefined },
) =>
  props.displayName
    ? Effect.succeed(props.displayName)
    : createPhysicalName({ id, maxLength: 100 });

const fetchTags = Effect.fn(function* (arn: string) {
  const response = yield* qbusiness
    .listTagsForResource({ resourceARN: arn })
    .pipe(
      Effect.catchTag("ResourceNotFoundException", () =>
        Effect.succeed(undefined),
      ),
    );
  return Object.fromEntries(
    (response?.tags ?? []).map((tag) => [tag.key, tag.value]),
  );
});

interface IndexState {
  attrs: Index["Attributes"];
  described: qbusiness.GetIndexResponse;
}

const readIndexById = Effect.fn(function* (
  applicationId: string,
  indexId: string,
) {
  const described = yield* qbusiness
    .getIndex({ applicationId, indexId })
    .pipe(
      Effect.catchTag("ResourceNotFoundException", () =>
        Effect.succeed(undefined),
      ),
    );
  if (!described || described.status === "DELETING") return undefined;
  const arn = described.indexArn;
  if (arn === undefined) return undefined;
  const state: IndexState = {
    described,
    attrs: {
      indexId: described.indexId ?? indexId,
      applicationId: described.applicationId ?? applicationId,
      indexArn: arn,
      displayName: described.displayName ?? "",
      type: described.type,
      status: described.status,
      tags: yield* fetchTags(arn),
    },
  };
  return state;
});

const findIndexByName = Effect.fn(function* (
  applicationId: string,
  displayName: string,
) {
  const summaries = yield* qbusiness.listIndices.pages({ applicationId }).pipe(
    EffectStream.runCollect,
    Effect.map((chunk) =>
      Array.from(chunk).flatMap((page) => page.indices ?? []),
    ),
    // The parent application may itself be gone.
    Effect.catchTag("ResourceNotFoundException", () =>
      Effect.succeed([] as qbusiness.Index[]),
    ),
  );
  const match = summaries.find(
    (summary) =>
      summary.displayName === displayName && summary.status !== "DELETING",
  );
  if (!match?.indexId) return undefined;
  return yield* readIndexById(applicationId, match.indexId);
});

/**
 * An index still transitioning toward the awaited status — retried by
 * {@link waitForIndexStatus}'s bounded schedule.
 */
class IndexNotReady extends Data.TaggedError("QBusinessIndexNotReady")<{
  readonly indexId: string;
  readonly status: string | undefined;
}> {}

/**
 * An index whose asynchronous provisioning converged to the terminal
 * `FAILED` status.
 */
export class IndexProvisioningFailed extends Data.TaggedError(
  "QBusinessIndexProvisioningFailed",
)<{
  readonly indexId: string;
  readonly message: string | undefined;
}> {}

// Explicitly-typed retry wrapper — an inline `Effect.retry` in provider
// lifecycle code leaks `Retry.Return`'s conditional type into declaration
// emit and widens the provider layer to `unknown` for every consumer of
// `AWS.providers()`.
const retryWhileNotReady = <A, E extends { readonly _tag: string }, R>(
  self: Effect.Effect<A, E, R>,
): Effect.Effect<A, E, R> =>
  Effect.retry(self, {
    while: (e) => e._tag === "QBusinessIndexNotReady",
    // Index provisioning takes several minutes; poll every 15s up to ~30 min.
    schedule: Schedule.max([
      Schedule.spaced("15 seconds"),
      Schedule.recurs(120),
    ]),
  });

const waitForIndexStatus = (
  applicationId: string,
  indexId: string,
  target: "ACTIVE" | "DELETED",
) =>
  retryWhileNotReady(
    Effect.gen(function* () {
      const described = yield* qbusiness
        .getIndex({ applicationId, indexId })
        .pipe(
          Effect.catchTag("ResourceNotFoundException", () =>
            Effect.succeed(undefined),
          ),
        );
      if (target === "DELETED") {
        if (described === undefined) return;
        return yield* Effect.fail(
          new IndexNotReady({ indexId, status: described.status }),
        );
      }
      if (described?.status === "ACTIVE") return;
      if (described?.status === "FAILED") {
        return yield* Effect.fail(
          new IndexProvisioningFailed({
            indexId,
            message: described.error?.errorMessage,
          }),
        );
      }
      return yield* Effect.fail(
        new IndexNotReady({ indexId, status: described?.status }),
      );
    }),
  );

export const IndexProvider = () =>
  Provider.effect(
    Index,
    Effect.gen(function* () {
      return {
        stables: ["indexId", "applicationId", "indexArn"],
        // Keyed by a parent application; cannot be enumerated account-wide
        // without iterating every application — treated as a sub-resource per
        // the factory list() convention.
        list: () => Effect.succeed([]),
        read: Effect.fn(function* ({ id, olds, output }) {
          const applicationId = output?.applicationId ?? olds?.applicationId;
          if (applicationId === undefined) return undefined;
          const state = output?.indexId
            ? yield* readIndexById(applicationId, output.indexId)
            : yield* findIndexByName(
                applicationId,
                yield* createDisplayName(id, olds ?? {}),
              );
          if (!state) return undefined;
          return (yield* hasAlchemyTags(id, state.attrs.tags as Tags))
            ? state.attrs
            : Unowned(state.attrs);
        }),
        diff: Effect.fn(function* ({ news, olds }) {
          if (!isResolved(news)) return;
          if (olds === undefined) return;
          // The parent application and index tier are fixed at creation.
          if (
            olds.applicationId !== news.applicationId ||
            (olds.type ?? "STARTER") !== (news.type ?? "STARTER")
          ) {
            return { action: "replace" } as const;
          }
        }),
        reconcile: Effect.fn(function* ({ id, news, output, session }) {
          if (!news) {
            return yield* Effect.fail(
              new Error("QBusiness Index requires props"),
            );
          }
          const applicationId = news.applicationId;
          const displayName = yield* createDisplayName(id, news);
          const internalTags = yield* createInternalTags(id);
          const desiredTags = { ...internalTags, ...news.tags };

          // Observe — prefer the cached id; fall back to a name lookup so a
          // create whose state failed to persist is adopted, not duplicated.
          let state = output?.indexId
            ? yield* readIndexById(applicationId, output.indexId)
            : yield* findIndexByName(applicationId, displayName);

          // Ensure — create if missing, then wait for ACTIVE.
          if (state === undefined) {
            const created = yield* qbusiness.createIndex({
              applicationId,
              displayName,
              description: news.description,
              type: news.type,
              capacityConfiguration: news.capacityConfiguration,
              tags: Object.entries(desiredTags).map(([key, value]) => ({
                key,
                value,
              })),
            });
            if (!created.indexId) {
              return yield* Effect.fail(
                new Error(
                  `CreateIndex for '${displayName}' returned no indexId`,
                ),
              );
            }
            yield* session.note(
              `Creating index ${displayName} (${created.indexId})...`,
            );
            yield* waitForIndexStatus(applicationId, created.indexId, "ACTIVE");
            state = yield* readIndexById(applicationId, created.indexId);
            if (state === undefined) {
              return yield* Effect.fail(
                new Error(`failed to read created index ${displayName}`),
              );
            }
          }

          // Sync mutable settings via UpdateIndex — only when drifted.
          const described = state.described;
          const desiredUnits = news.capacityConfiguration?.units;
          const needsUpdate =
            displayName !== described.displayName ||
            (news.description ?? "") !== (described.description ?? "") ||
            (desiredUnits !== undefined &&
              desiredUnits !== described.capacityConfiguration?.units) ||
            news.documentAttributeConfigurations !== undefined;
          if (needsUpdate) {
            yield* qbusiness.updateIndex({
              applicationId,
              indexId: state.attrs.indexId,
              displayName,
              description: news.description,
              capacityConfiguration: news.capacityConfiguration,
              documentAttributeConfigurations:
                news.documentAttributeConfigurations,
            });
            yield* waitForIndexStatus(
              applicationId,
              state.attrs.indexId,
              "ACTIVE",
            );
            yield* session.note(`Updated index ${displayName}`);
          }

          // Sync tags — diff against observed cloud tags.
          const { removed, upsert } = diffTags(state.attrs.tags, desiredTags);
          if (removed.length > 0) {
            yield* qbusiness.untagResource({
              resourceARN: state.attrs.indexArn,
              tagKeys: removed,
            });
          }
          if (upsert.length > 0) {
            yield* qbusiness.tagResource({
              resourceARN: state.attrs.indexArn,
              tags: upsert.map(({ Key, Value }) => ({
                key: Key,
                value: Value,
              })),
            });
          }

          yield* session.note(state.attrs.indexArn);

          const final = yield* readIndexById(
            applicationId,
            state.attrs.indexId,
          );
          if (!final) {
            return yield* Effect.fail(
              new Error(`failed to read reconciled index ${displayName}`),
            );
          }
          return final.attrs;
        }),
        delete: Effect.fn(function* ({ output }) {
          yield* qbusiness
            .deleteIndex({
              applicationId: output.applicationId,
              indexId: output.indexId,
            })
            .pipe(
              Effect.catchTag("ResourceNotFoundException", () => Effect.void),
            );
          yield* waitForIndexStatus(
            output.applicationId,
            output.indexId,
            "DELETED",
          );
        }),
      };
    }),
  );