import { ASTNode } from 'graphql/language/ast';
import { visit } from 'graphql/language/visitor';
import { prettify } from './helpers/prettify';

/**
 * Converts an AST into a string, using one set of reasonable
 * formatting rules.
 */

export type PrintOptions = {
  clientVarName?: string;
  transformVariableName?: (x: string) => string;
  thenCode?: string;
};

export function print(ast: ASTNode, options: PrintOptions = {}) {
  return visit(ast, {
    leave: (node) => {
      const fn = printDocASTReducer(options);
      const visitor = fn[node.kind];
      if (visitor) {
        return visitor(node);
      }
      return null;
    },
  });
}

function printDocASTReducer({ clientVarName = 'client', transformVariableName = (x) => x, thenCode }: PrintOptions) {
  return {
    Name: (node) => node.value,
    Variable: (node) => transformVariableName(node.name),
    NamedType: ({ name }) => name,
    ListType: ({ type }) => '[' + type + ']',
    NonNullType: ({ type }) => type,
    Directive: ({ name, arguments: args }) => '',

    IntValue: ({ value }) => value,
    FloatValue: ({ value }) => value,
    StringValue: ({ value, block: isBlockString }, key) => JSON.stringify(value),
    BooleanValue: ({ value }) => (value ? 'true' : 'false'),
    NullValue: () => 'null',
    EnumValue: ({ value }) => `'${value}'`,
    ListValue: ({ values }) => '[' + join(values, ', ') + ']',
    ObjectValue: ({ fields }) => '{' + join(fields, ', ') + '}',
    ObjectField: ({ name, value }) => name + ': ' + value,

    // Document

    Document: (node) => join(node.definitions, '\n\n') + '\n',

    OperationDefinition(node) {
      const selectionSet = node.selectionSet;
      // Anonymous queries with no directives or variable definitions can use
      // the query short form.
      let code = join(node.variableDefinitions, '\n');
      if (node.variableDefinitions.length) {
        code = '// variables\n' + code;
        code += '\n\n';
      }
      code += `${clientVarName}.${node.operation}(` + selectionSet + ')';
      if (thenCode) {
        code += `.then(${thenCode})`;
      }
      return prettify(code, 'typescript');
    },

    VariableDefinition: ({ variable, type, defaultValue, directives }) => {
      return 'var ' + variable.replace('$', '');
    },
    SelectionSet: ({ selections }) => block(selections),

    Field: ({ alias, name, arguments: args, directives, selectionSet }) => {
      if (args.length == 0 && !join([selectionSet])) {
        return name + ': true';
      }
      if (args.length == 0) {
        return name + ': ' + join([selectionSet]);
      }
      const argsAndFields = join([block(args), ',', selectionSet]);
      return name + ': ' + wrap('[', argsAndFields, ']');
    },
    // join(directives, ' '),

    Argument: ({ name, value = '' }) => {
      if (typeof value === 'string') {
        return name + ': ' + transformVariableName(value.replace('$', ''));
      }
      console.error(`unhandled type, received ${JSON.stringify(value)} as Argument`);
      return '';
    },
    // Fragments

    FragmentSpread: ({ name, directives }) => {
      // TODO FragmentSpread
      return '...' + name + ',';
    },

    InlineFragment: ({ typeCondition, directives, selectionSet }) => {
      // console.log({ selectionSet, directives, typeCondition });
      return join(['', wrap('on_', typeCondition), ':', selectionSet], ' ');
    },

    FragmentDefinition: ({ name, typeCondition, variableDefinitions, directives, selectionSet }) => {
      // TODO FragmentDefinition
      // Note: fragment variable definitions are experimental and may be changed
      // or removed in the future.
      return `const ${name} = ` + selectionSet;
    },
    // Directive
  };
}

/**
 * Given maybeArray, print an empty string if it is null or empty, otherwise
 * print all items together separated by separator if provided
 */
function join(maybeArray: Array<string>, separator = '') {
  return maybeArray?.filter((x) => x).join(separator) ?? '';
}

/**
 * Given array, print each item on its own line, wrapped in an
 * indented "{ }" block.
 */
function block(array) {
  return array && array.length !== 0 ? '{\n' + indent(join(array, ',\n')) + '\n}' : '';
}

/**
 * If maybeString is not null or empty, then wrap with start and end, otherwise
 * print an empty string.
 */
function wrap(start, maybeString, end = '') {
  return maybeString ? start + maybeString + end : '';
}

function indent(maybeString) {
  return maybeString && '  ' + maybeString.replace(/\n/g, '\n  ');
}

function isMultiline(string) {
  return string.indexOf('\n') !== -1;
}

function hasMultilineItems(maybeArray) {
  return maybeArray && maybeArray.some(isMultiline);
}