import {
  Fetcher,
  fillLeafs,
  formatError,
  formatResult,
  GetDefaultFieldNamesFn,
  isAsyncIterable,
  isObservable,
  Unsubscribable,
} from '@graphiql/toolkit';
import { ExecutionResult, GraphQLError, print } from 'graphql';
import { getFragmentDependenciesForAST } from 'graphql-language-service';
import setValue from 'set-value';
import getValue from 'get-value';

import type { StateCreator } from 'zustand';
import { tryParseJSONC, Range } from '../utility';
import type { SlicesWithActions, MonacoEditor } from '../types';

export interface ExecutionSlice {
  /**
   * If there is currently a GraphQL request in-flight. For multipart
   * requests like subscriptions, this will be `true` while fetching the
   * first partial response and `false` while fetching subsequent batches.
   * @default false
   */
  isFetching: boolean;

  /**
   * Represents an active GraphQL subscription.
   *
   * For multipart operations such as subscriptions, this
   * will hold an `Unsubscribable` object while the request is in-flight. It
   * remains non-null until the operation completes or is manually unsubscribed.
   *
   * @remarks Use `subscription?.unsubscribe()` to cancel the request.
   * @default null
   */
  subscription: Unsubscribable | null;

  /**
   * The operation name that will be sent with all GraphQL requests.
   * @default null
   */
  overrideOperationName: string | null;

  /**
   * A function to determine which field leafs are automatically added when
   * trying to execute a query with missing selection sets. It will be called
   * with the `GraphQLType` for which fields need to be added.
   */
  getDefaultFieldNames?: GetDefaultFieldNamesFn;

  /**
   * @default 0
   */
  queryId: number;

  /**
   * A function which accepts GraphQL HTTP parameters and returns a `Promise`,
   * `Observable` or `AsyncIterable` that returns the GraphQL response in
   * parsed JSON format.
   *
   * We suggest using the `createGraphiQLFetcher` utility from `@graphiql/toolkit`
   * to create these fetcher functions.
   *
   * @see {@link https://graphiql-test.netlify.app/typedoc/modules/graphiql_toolkit.html#creategraphiqlfetcher-2|`createGraphiQLFetcher`}
   */
  fetcher: Fetcher;
}

export interface ExecutionActions {
  /**
   * Start a GraphQL request based on the current editor contents.
   */
  run(): void;

  /**
   * Stop the GraphQL request that is currently in-flight.
   */
  stop(): void;
}

export interface ExecutionProps extends Pick<
  ExecutionSlice,
  'getDefaultFieldNames' | 'fetcher'
> {
  /**
   * This prop sets the operation name that is passed with a GraphQL request.
   */
  operationName?: string;
}

type CreateExecutionSlice = (
  initial: Pick<
    ExecutionSlice,
    'overrideOperationName' | 'getDefaultFieldNames' | 'fetcher'
  >,
) => StateCreator<
  SlicesWithActions,
  [],
  [],
  ExecutionSlice & {
    actions: ExecutionActions;
  }
>;

export const createExecutionSlice: CreateExecutionSlice =
  initial => (set, get) => {
    function getAutoCompleteLeafs() {
      const { queryEditor, schema, getDefaultFieldNames } = get();
      if (!queryEditor) {
        return;
      }
      const query = queryEditor.getValue();
      const { insertions, result = '' } = fillLeafs(
        schema,
        query,
        getDefaultFieldNames,
      );
      if (!insertions.length) {
        return result;
      }
      const model = queryEditor.getModel()!;

      // Save the current cursor position as an offset
      const selection = queryEditor.getSelection()!;
      const cursorIndex = model.getOffsetAt(selection.getPosition());

      // Replace entire content
      model.setValue(result);

      let added = 0;
      const decorations = insertions.map(({ index, string }) => {
        const start = model.getPositionAt(index + added);
        const end = model.getPositionAt(index + (added += string.length));
        return {
          range: new Range(
            start.lineNumber,
            start.column,
            end.lineNumber,
            end.column,
          ),
          options: {
            className: 'auto-inserted-leaf',
            hoverMessage: { value: 'Automatically added leaf fields' },
            isWholeLine: false,
          },
        };
      });

      // Create a decoration collection (initially empty)
      const decorationCollection = queryEditor.createDecorationsCollection([]);

      // Apply decorations
      decorationCollection.set(decorations);

      // Clear decorations after 7 seconds
      setTimeout(() => {
        decorationCollection.clear();
      }, 7000);

      // Adjust the cursor position based on insertions
      let newCursorIndex = cursorIndex;
      for (const { index, string } of insertions) {
        if (index < cursorIndex) {
          newCursorIndex += string.length;
        }
      }

      const newCursorPosition = model.getPositionAt(newCursorIndex);
      queryEditor.setPosition(newCursorPosition);

      return result;
    }

    return {
      ...initial,
      isFetching: false,
      subscription: null,
      queryId: 0,
      actions: {
        stop() {
          set(({ subscription }) => {
            subscription?.unsubscribe();
            return { isFetching: false, subscription: null };
          });
        },
        async run() {
          const {
            externalFragments,
            headerEditor,
            queryEditor,
            responseEditor,
            variableEditor,
            actions,
            operationName,
            documentAST,
            subscription,
            overrideOperationName,
            queryId,
            fetcher,
          } = get();
          if (!queryEditor || !responseEditor) {
            return;
          }
          // If there's an active subscription, unsubscribe it and return
          if (subscription) {
            actions.stop();
            return;
          }

          function setResponse(value: string): void {
            responseEditor?.setValue(value);
            actions.updateActiveTabValues({ response: value });
          }

          function setError(error: Error, editor?: MonacoEditor): void {
            if (!editor) {
              return;
            }
            const name =
              editor === variableEditor ? 'Variables' : 'Request headers';
            // Need to format since the response editor uses `json` language
            setResponse(formatError({ message: `${name} ${error.message}` }));
          }

          const newQueryId = queryId + 1;
          set({ queryId: newQueryId });

          // Use the edited query after autoCompleteLeafs() runs or,
          // in case autoCompletion fails (the function returns undefined),
          // the current query from the editor.
          let query = getAutoCompleteLeafs() || queryEditor.getValue();

          let variables: Record<string, unknown> | undefined;
          try {
            variables = tryParseJSONC(variableEditor?.getValue());
          } catch (error) {
            setError(error as Error, variableEditor);
            return;
          }
          let headers: Record<string, unknown> | undefined;
          try {
            headers = tryParseJSONC(headerEditor?.getValue());
          } catch (error) {
            setError(error as Error, headerEditor);
            return;
          }
          const fragmentDependencies = documentAST
            ? getFragmentDependenciesForAST(documentAST, externalFragments)
            : [];
          if (fragmentDependencies.length) {
            query +=
              '\n' + fragmentDependencies.map(node => print(node)).join('\n');
          }

          setResponse('');
          set({ isFetching: true });
          try {
            const fullResponse: ExecutionResult = {};
            const handleResponse = (result: ExecutionResult) => {
              // A different query was dispatched in the meantime, so don't
              // show the results of this one.
              if (newQueryId !== get().queryId) {
                return;
              }

              let maybeMultipart = Array.isArray(result) ? result : false;
              if (
                !maybeMultipart &&
                typeof result === 'object' &&
                'hasNext' in result
              ) {
                maybeMultipart = [result];
              }

              if (maybeMultipart) {
                for (const part of maybeMultipart) {
                  mergeIncrementalResult(fullResponse, part);
                }

                set({ isFetching: false });
                setResponse(formatResult(fullResponse));
              } else {
                set({ isFetching: false });
                setResponse(formatResult(result));
              }
            };
            const opName = overrideOperationName ?? operationName;
            const fetch = fetcher(
              { query, variables, operationName: opName },
              { headers, documentAST },
            );

            const value = await fetch;
            if (isObservable(value)) {
              // If the fetcher returned an Observable, then subscribe to it, calling
              // the callback on each next value and handling both errors and the
              // completion of the Observable.
              const newSubscription = value.subscribe({
                next(result) {
                  handleResponse(result);
                },
                error(error: Error) {
                  set({ isFetching: false });
                  setResponse(formatError(error));
                  set({ subscription: null });
                },
                complete() {
                  set({ isFetching: false, subscription: null });
                },
              });
              set({ subscription: newSubscription });
            } else if (isAsyncIterable(value)) {
              const newSubscription = {
                unsubscribe: () => value[Symbol.asyncIterator]().return?.(),
              };
              set({ subscription: newSubscription });
              for await (const result of value) {
                handleResponse(result);
              }
              set({ isFetching: false, subscription: null });
            } else {
              handleResponse(value);
            }
          } catch (error) {
            set({ isFetching: false });
            setResponse(formatError(error));
            set({ subscription: null });
          }
        },
      },
    };
  };

interface IncrementalResult {
  data?: Record<string, unknown> | null;
  errors?: ReadonlyArray<GraphQLError>;
  extensions?: Record<string, unknown>;
  hasNext?: boolean;
  path?: ReadonlyArray<string | number>;
  incremental?: ReadonlyArray<IncrementalResult>;
  label?: string;
  items?: ReadonlyArray<Record<string, unknown>> | null;
  pending?: ReadonlyArray<{ id: string; path: ReadonlyArray<string | number> }>;
  completed?: ReadonlyArray<{
    id: string;
    errors?: ReadonlyArray<GraphQLError>;
  }>;
  id?: string;
  subPath?: ReadonlyArray<string | number>;
}

const pathsMap = new WeakMap<
  ExecutionResult,
  Map<string, ReadonlyArray<string | number>>
>();

/**
 * @param executionResult - The complete execution result object which will be
 * mutated by merging the contents of the incremental result.
 * @param incrementalResult - The incremental result that will be merged into the
 * complete execution result.
 */
function mergeIncrementalResult(
  executionResult: IncrementalResult,
  incrementalResult: IncrementalResult,
): void {
  let path: ReadonlyArray<string | number> | undefined = [
    'data',
    ...(incrementalResult.path ?? []),
  ];

  for (const result of [executionResult, incrementalResult]) {
    if (result.pending) {
      let paths = pathsMap.get(executionResult);
      if (paths === undefined) {
        paths = new Map();
        pathsMap.set(executionResult, paths);
      }

      for (const { id, path: pendingPath } of result.pending) {
        paths.set(id, ['data', ...pendingPath]);
      }
    }
  }

  const { items, data, id } = incrementalResult;
  if (items) {
    if (id) {
      path = pathsMap.get(executionResult)?.get(id);
      if (path === undefined) {
        throw new Error('Invalid incremental delivery format.');
      }

      const list = getValue(executionResult, path.join('.'));
      list.push(...items);
    } else {
      path = ['data', ...(incrementalResult.path ?? [])];
      for (const item of items) {
        setValue(executionResult, path.join('.'), item);
        // Increment the last path segment (the array index) to merge the next item at the next index
        // @ts-expect-error -- (path[path.length - 1] as number)++ breaks react compiler
        path[path.length - 1]++;
      }
    }
  }
  if (data) {
    if (id) {
      path = pathsMap.get(executionResult)?.get(id);
      if (path === undefined) {
        throw new Error('Invalid incremental delivery format.');
      }
      const { subPath } = incrementalResult;
      if (subPath !== undefined) {
        path = [...path, ...subPath];
      }
    }
    setValue(executionResult, path.join('.'), data, {
      merge: true,
    });
  }

  if (incrementalResult.errors) {
    executionResult.errors ||= [];
    (executionResult.errors as GraphQLError[]).push(
      ...incrementalResult.errors,
    );
  }

  if (incrementalResult.extensions) {
    setValue(executionResult, 'extensions', incrementalResult.extensions, {
      merge: true,
    });
  }

  if (incrementalResult.incremental) {
    for (const incrementalSubResult of incrementalResult.incremental) {
      mergeIncrementalResult(executionResult, incrementalSubResult);
    }
  }

  if (incrementalResult.completed) {
    // Remove tracking and add additional errors
    for (const { id: completedId, errors } of incrementalResult.completed) {
      pathsMap.get(executionResult)?.delete(completedId);
      if (errors) {
        executionResult.errors ||= [];
        (executionResult.errors as GraphQLError[]).push(...errors);
      }
    }
  }
}