import { davConditionalFailure } from "@/worker/dav/conditional";
import type { ParsedIfHeader } from "@/worker/dav/if-header";
import { parseCollectionObjectPath } from "@/worker/dav/paths";

export interface CollectionConditionalInput {
  subjectId: string;
  nowMs: number;
  ifMatch: string | null;
  ifNoneMatch: string | null;
  ifHeader: ParsedIfHeader;
}

export interface CollectionPreconditionSpec<TDb, TCollection extends { id: string }, TError> {
  basePath: string;
  collectionHref: (collectionName: string) => string;
  ensureCollection: (db: TDb, subjectId: string, nowMs: number, collectionName: string) => TCollection | null;
  objectEtag: (db: TDb, collectionId: string, objectName: string) => string | null;
  latestChangeSeq: (db: TDb) => number;
  syncToken: (seq: number) => string;
  preconditionFailed: (message: string) => TError;
}

export function collectionWritePrecondition<TDb, TCollection extends { id: string }, TError>(
  db: TDb,
  input: CollectionConditionalInput,
  targetHref: string,
  targetEtag: string | null,
  spec: CollectionPreconditionSpec<TDb, TCollection, TError>,
): TError | null {
  const stateHref = collectionStateHrefForTarget(targetHref, spec.basePath, spec.collectionHref);
  const failure = davConditionalFailure({
    ifMatch: input.ifMatch,
    ifNoneMatch: input.ifNoneMatch,
    ifHeader: input.ifHeader,
    targetHref,
    targetEtag,
    getEtag: (href) => collectionEtagForHref(db, input, href, spec),
    getStateToken: (href) => (href === stateHref ? collectionStateTokenForHref(db, input, href, spec) : null),
  });
  return failure ? spec.preconditionFailed(failure) : null;
}

function collectionStateHrefForTarget(
  targetHref: string,
  basePath: string,
  collectionHref: (collectionName: string) => string,
): string | null {
  const path = parseCollectionObjectPath(targetHref, basePath);
  if (!path || path.kind === "home") return null;
  return collectionHref(path.collectionName);
}

function collectionEtagForHref<TDb, TCollection extends { id: string }, TError>(
  db: TDb,
  input: CollectionConditionalInput,
  href: string,
  spec: CollectionPreconditionSpec<TDb, TCollection, TError>,
): string | null {
  const path = parseCollectionObjectPath(href, spec.basePath);
  if (!path || path.kind !== "object") return null;
  const collection = spec.ensureCollection(db, input.subjectId, input.nowMs, path.collectionName);
  if (!collection) return null;
  return spec.objectEtag(db, collection.id, path.objectName);
}

function collectionStateTokenForHref<TDb, TCollection extends { id: string }, TError>(
  db: TDb,
  input: CollectionConditionalInput,
  href: string,
  spec: CollectionPreconditionSpec<TDb, TCollection, TError>,
): string | null {
  const path = parseCollectionObjectPath(href, spec.basePath);
  if (!path || path.kind !== "collection") return null;
  const collection = spec.ensureCollection(db, input.subjectId, input.nowMs, path.collectionName);
  return collection ? spec.syncToken(spec.latestChangeSeq(db)) : null;
}