// @flow strict

import find from '../polyfills/find';

import { Kind } from '../language/kinds';
import { type ASTNode, type FieldNode } from '../language/ast';

import { type GraphQLSchema } from '../type/schema';
import { type GraphQLDirective } from '../type/directives';
import {
  type GraphQLType,
  type GraphQLInputType,
  type GraphQLOutputType,
  type GraphQLCompositeType,
  type GraphQLField,
  type GraphQLArgument,
  type GraphQLInputField,
  type GraphQLEnumValue,
  isObjectType,
  isInterfaceType,
  isEnumType,
  isInputObjectType,
  isListType,
  isCompositeType,
  isInputType,
  isOutputType,
  getNullableType,
  getNamedType,
} from '../type/definition';
import {
  SchemaMetaFieldDef,
  TypeMetaFieldDef,
  TypeNameMetaFieldDef,
} from '../type/introspection';

import { typeFromAST } from './typeFromAST';

/**
 * TypeInfo is a utility class which, given a GraphQL schema, can keep track
 * of the current field and type definitions at any point in a GraphQL document
 * AST during a recursive descent by calling `enter(node)` and `leave(node)`.
 */
export class TypeInfo {
  _schema: GraphQLSchema;
  _typeStack: Array<?GraphQLOutputType>;
  _parentTypeStack: Array<?GraphQLCompositeType>;
  _inputTypeStack: Array<?GraphQLInputType>;
  _fieldDefStack: Array<?GraphQLField<mixed, mixed>>;
  _defaultValueStack: Array<?mixed>;
  _directive: ?GraphQLDirective;
  _argument: ?GraphQLArgument;
  _enumValue: ?GraphQLEnumValue;
  _getFieldDef: typeof getFieldDef;

  constructor(
    schema: GraphQLSchema,
    // NOTE: this experimental optional second parameter is only needed in order
    // to support non-spec-compliant codebases. You should never need to use it.
    // It may disappear in the future.
    getFieldDefFn?: typeof getFieldDef,
    // Initial type may be provided in rare cases to facilitate traversals
    // beginning somewhere other than documents.
    initialType?: GraphQLType,
  ): void {
    this._schema = schema;
    this._typeStack = [];
    this._parentTypeStack = [];
    this._inputTypeStack = [];
    this._fieldDefStack = [];
    this._defaultValueStack = [];
    this._directive = null;
    this._argument = null;
    this._enumValue = null;
    this._getFieldDef = getFieldDefFn || getFieldDef;
    if (initialType) {
      if (isInputType(initialType)) {
        this._inputTypeStack.push(initialType);
      }
      if (isCompositeType(initialType)) {
        this._parentTypeStack.push(initialType);
      }
      if (isOutputType(initialType)) {
        this._typeStack.push(initialType);
      }
    }
  }

  getType(): ?GraphQLOutputType {
    if (this._typeStack.length > 0) {
      return this._typeStack[this._typeStack.length - 1];
    }
  }

  getParentType(): ?GraphQLCompositeType {
    if (this._parentTypeStack.length > 0) {
      return this._parentTypeStack[this._parentTypeStack.length - 1];
    }
  }

  getInputType(): ?GraphQLInputType {
    if (this._inputTypeStack.length > 0) {
      return this._inputTypeStack[this._inputTypeStack.length - 1];
    }
  }

  getParentInputType(): ?GraphQLInputType {
    if (this._inputTypeStack.length > 1) {
      return this._inputTypeStack[this._inputTypeStack.length - 2];
    }
  }

  getFieldDef(): ?GraphQLField<mixed, mixed> {
    if (this._fieldDefStack.length > 0) {
      return this._fieldDefStack[this._fieldDefStack.length - 1];
    }
  }

  getDefaultValue(): ?mixed {
    if (this._defaultValueStack.length > 0) {
      return this._defaultValueStack[this._defaultValueStack.length - 1];
    }
  }

  getDirective(): ?GraphQLDirective {
    return this._directive;
  }

  getArgument(): ?GraphQLArgument {
    return this._argument;
  }

  getEnumValue(): ?GraphQLEnumValue {
    return this._enumValue;
  }

  enter(node: ASTNode) {
    const schema = this._schema;
    // Note: many of the types below are explicitly typed as "mixed" to drop
    // any assumptions of a valid schema to ensure runtime types are properly
    // checked before continuing since TypeInfo is used as part of validation
    // which occurs before guarantees of schema and document validity.
    switch (node.kind) {
      case Kind.SELECTION_SET: {
        const namedType: mixed = getNamedType(this.getType());
        this._parentTypeStack.push(
          isCompositeType(namedType) ? namedType : undefined,
        );
        break;
      }
      case Kind.FIELD: {
        const parentType = this.getParentType();
        let fieldDef;
        let fieldType: mixed;
        if (parentType) {
          fieldDef = this._getFieldDef(schema, parentType, node);
          if (fieldDef) {
            fieldType = fieldDef.type;
          }
        }
        this._fieldDefStack.push(fieldDef);
        this._typeStack.push(isOutputType(fieldType) ? fieldType : undefined);
        break;
      }
      case Kind.DIRECTIVE:
        this._directive = schema.getDirective(node.name.value);
        break;
      case Kind.OPERATION_DEFINITION: {
        let type: mixed;
        if (node.operation === 'query') {
          type = schema.getQueryType();
        } else if (node.operation === 'mutation') {
          type = schema.getMutationType();
        } else if (node.operation === 'subscription') {
          type = schema.getSubscriptionType();
        }
        this._typeStack.push(isObjectType(type) ? type : undefined);
        break;
      }
      case Kind.INLINE_FRAGMENT:
      case Kind.FRAGMENT_DEFINITION: {
        const typeConditionAST = node.typeCondition;
        const outputType: mixed = typeConditionAST
          ? typeFromAST(schema, typeConditionAST)
          : getNamedType(this.getType());
        this._typeStack.push(isOutputType(outputType) ? outputType : undefined);
        break;
      }
      case Kind.VARIABLE_DEFINITION: {
        const inputType: mixed = typeFromAST(schema, node.type);
        this._inputTypeStack.push(
          isInputType(inputType) ? inputType : undefined,
        );
        break;
      }
      case Kind.ARGUMENT: {
        let argDef;
        let argType: mixed;
        const fieldOrDirective = this.getDirective() || this.getFieldDef();
        if (fieldOrDirective) {
          argDef = find(
            fieldOrDirective.args,
            arg => arg.name === node.name.value,
          );
          if (argDef) {
            argType = argDef.type;
          }
        }
        this._argument = argDef;
        this._defaultValueStack.push(argDef ? argDef.defaultValue : undefined);
        this._inputTypeStack.push(isInputType(argType) ? argType : undefined);
        break;
      }
      case Kind.LIST: {
        const listType: mixed = getNullableType(this.getInputType());
        const itemType: mixed = isListType(listType)
          ? listType.ofType
          : listType;
        // List positions never have a default value.
        this._defaultValueStack.push(undefined);
        this._inputTypeStack.push(isInputType(itemType) ? itemType : undefined);
        break;
      }
      case Kind.OBJECT_FIELD: {
        const objectType: mixed = getNamedType(this.getInputType());
        let inputFieldType: GraphQLInputType | void;
        let inputField: GraphQLInputField | void;
        if (isInputObjectType(objectType)) {
          inputField = objectType.getFields()[node.name.value];
          if (inputField) {
            inputFieldType = inputField.type;
          }
        }
        this._defaultValueStack.push(
          inputField ? inputField.defaultValue : undefined,
        );
        this._inputTypeStack.push(
          isInputType(inputFieldType) ? inputFieldType : undefined,
        );
        break;
      }
      case Kind.ENUM: {
        const enumType: mixed = getNamedType(this.getInputType());
        let enumValue;
        if (isEnumType(enumType)) {
          enumValue = enumType.getValue(node.value);
        }
        this._enumValue = enumValue;
        break;
      }
    }
  }

  leave(node: ASTNode) {
    switch (node.kind) {
      case Kind.SELECTION_SET:
        this._parentTypeStack.pop();
        break;
      case Kind.FIELD:
        this._fieldDefStack.pop();
        this._typeStack.pop();
        break;
      case Kind.DIRECTIVE:
        this._directive = null;
        break;
      case Kind.OPERATION_DEFINITION:
      case Kind.INLINE_FRAGMENT:
      case Kind.FRAGMENT_DEFINITION:
        this._typeStack.pop();
        break;
      case Kind.VARIABLE_DEFINITION:
        this._inputTypeStack.pop();
        break;
      case Kind.ARGUMENT:
        this._argument = null;
        this._defaultValueStack.pop();
        this._inputTypeStack.pop();
        break;
      case Kind.LIST:
      case Kind.OBJECT_FIELD:
        this._defaultValueStack.pop();
        this._inputTypeStack.pop();
        break;
      case Kind.ENUM:
        this._enumValue = null;
        break;
    }
  }
}

/**
 * Not exactly the same as the executor's definition of getFieldDef, in this
 * statically evaluated environment we do not always have an Object type,
 * and need to handle Interface and Union types.
 */
function getFieldDef(
  schema: GraphQLSchema,
  parentType: GraphQLType,
  fieldNode: FieldNode,
): ?GraphQLField<mixed, mixed> {
  const name = fieldNode.name.value;
  if (
    name === SchemaMetaFieldDef.name &&
    schema.getQueryType() === parentType
  ) {
    return SchemaMetaFieldDef;
  }
  if (name === TypeMetaFieldDef.name && schema.getQueryType() === parentType) {
    return TypeMetaFieldDef;
  }
  if (name === TypeNameMetaFieldDef.name && isCompositeType(parentType)) {
    return TypeNameMetaFieldDef;
  }
  if (isObjectType(parentType) || isInterfaceType(parentType)) {
    return parentType.getFields()[name];
  }
}