/* eslint-disable no-continue */
import type { OpenAPIV3_1 } from 'openapi-types';

import mergeJSONSchemaAllOf from 'json-schema-merge-allof';
import jsonpointer from 'jsonpointer';

import * as RMOAS from '../rmoas.types';

/**
 * This list has been pulled from `openapi-schema-to-json-schema` but been slightly modified to fit
 * within the constraints in which ReadMe uses the output from this library in schema form
 * rendering as while properties like `readOnly` aren't represented within JSON Schema, we support
 * it within that library's handling of OpenAPI-friendly JSON Schema.
 *
 * @see {@link https://github.com/openapi-contrib/openapi-schema-to-json-schema/blob/master/index.js#L23-L27}
 */
const UNSUPPORTED_SCHEMA_PROPS: ('nullable' | 'xml' | 'externalDocs' | 'example')[] = [
  'nullable',
  // 'discriminator',
  // 'readOnly',
  // 'writeOnly',
  'xml',
  'externalDocs',
  'example', // OpenAPI supports `example`, but we're mapping it to `examples` below.
  // 'deprecated',
];

type PrevSchemasType = RMOAS.SchemaObject[];

export interface toJSONSchemaOptions {
  /**
   * Whether or not to extend descriptions with a list of any present enums.
   */
  addEnumsToDescriptions?: boolean;

  /**
   * Current location within the schema -- this is a JSON pointer.
   */
  currentLocation?: string;

  /**
   * Object containing a global set of defaults that we should apply to schemas that match it.
   */
  globalDefaults?: Record<string, unknown>;

  /**
   * Is this schema the child of a polymorphic `allOf` schema?
   */
  isPolymorphicAllOfChild?: boolean;

  /**
   * Array of parent schemas to utilize when attempting to path together examples.
   */
  prevSchemas?: PrevSchemasType;

  /**
   * A function that's called anytime a (circular) `$ref` is found.
   */
  refLogger?: (ref: string, type: 'ref' | 'discriminator') => void;

  /**
   * A function that's called to potentially transform any discovered schema.
   */
  transformer?: (schema: RMOAS.SchemaObject) => RMOAS.SchemaObject;
}

/**
 * List partially sourced from `openapi-schema-to-json-schema`.
 *
 * @see {@link https://github.com/openapi-contrib/openapi-schema-to-json-schema/blob/master/lib/converters/schema.js#L140-L154}
 */
const FORMAT_OPTIONS: {
  [key: `${string}_MAX`]: number;
  [key: `${string}_MIN`]: number;
} = {
  INT8_MIN: 0 - 2 ** 7, // -128
  INT8_MAX: 2 ** 7 - 1, // 127
  INT16_MIN: 0 - 2 ** 15, // -32768
  INT16_MAX: 2 ** 15 - 1, // 32767
  INT32_MIN: 0 - 2 ** 31, // -2147483648
  INT32_MAX: 2 ** 31 - 1, // 2147483647
  INT64_MIN: 0 - 2 ** 63, // -9223372036854775808
  INT64_MAX: 2 ** 63 - 1, // 9223372036854775807

  UINT8_MIN: 0,
  UINT8_MAX: 2 ** 8 - 1, // 255
  UINT16_MIN: 0,
  UINT16_MAX: 2 ** 16 - 1, // 65535
  UINT32_MIN: 0,
  UINT32_MAX: 2 ** 32 - 1, // 4294967295
  UINT64_MIN: 0,
  UINT64_MAX: 2 ** 64 - 1, // 18446744073709551615

  FLOAT_MIN: 0 - 2 ** 128, // -3.402823669209385e+38
  FLOAT_MAX: 2 ** 128 - 1, // 3.402823669209385e+38

  DOUBLE_MIN: 0 - Number.MAX_VALUE,
  DOUBLE_MAX: Number.MAX_VALUE,
};

/**
 * Encode a string to be used as a JSON pointer.
 *
 * @see {@link https://tools.ietf.org/html/rfc6901}
 * @param str String to encode into string that can be used as a JSON pointer.
 */
function encodePointer(str: string) {
  return str.replace('~', '~0').replace('/', '~1');
}

export function getSchemaVersionString(schema: RMOAS.SchemaObject, api: RMOAS.OASDocument): string {
  // If we're not on version 3.1.0, we always fall back to the default schema version for pre-3.1.0.
  if (!RMOAS.isOAS31(api)) {
    // This should remain as an HTTP url, not HTTPS.
    return 'http://json-schema.org/draft-04/schema#';
  }

  /**
   * If the schema indicates the version, prefer that.
   *
   * We use `as` here because the schema *should* be an OAS 3.1 schema due to the `isOAS31` check
   * above.
   */
  if ((schema as OpenAPIV3_1.SchemaObject).$schema) {
    return (schema as OpenAPIV3_1.SchemaObject).$schema;
  }

  // If the user defined a global schema version on their OAS document, prefer that.
  if (api.jsonSchemaDialect) {
    return api.jsonSchemaDialect;
  }

  return 'https://json-schema.org/draft/2020-12/schema#';
}

export function isPrimitive(val: unknown): boolean {
  return typeof val === 'string' || typeof val === 'number' || typeof val === 'boolean';
}

function isPolymorphicSchema(schema: RMOAS.SchemaObject): boolean {
  return 'allOf' in schema || 'anyOf' in schema || 'oneOf' in schema;
}

function isRequestBodySchema(schema: unknown): schema is RMOAS.RequestBodyObject {
  return 'content' in (schema as RMOAS.RequestBodyObject);
}

/**
 * Given a JSON pointer and an array of examples do a reverse search through them until we find the
 * JSON pointer, or part of it, within the array.
 *
 * This function will allow you to take a pointer like `/tags/name` and return back `buster` from
 * the following array:
 *
 * ```
 *  [
 *    {
 *      example: {id: 20}
 *    },
 *    {
 *      examples: {
 *        distinctName: {
 *          tags: {name: 'buster'}
 *        }
 *      }
 *    }
 *  ]
 * ```
 *
 * As with most things however, this is not without its quirks! If a deeply nested property shares
 * the same name as an example that's further up the stack (like `tags.id` and an example for `id`),
 * there's a chance that it'll be misidentified as having an example and receive the wrong value.
 *
 * That said, any example is usually better than no example though, so while it's quirky behavior
 * it shouldn't raise immediate cause for alarm.
 *
 * @see {@link https://tools.ietf.org/html/rfc6901}
 * @param pointer JSON pointer to search for an example for.
 * @param examples Array of previous schemas we've found relating to this pointer.
 */
function searchForExampleByPointer(pointer: string, examples: PrevSchemasType = []) {
  if (!examples.length || !pointer.length) {
    return undefined;
  }

  const locSplit = pointer.split('/').filter(Boolean).reverse();
  const pointers = [];

  let point = '';
  for (let i = 0; i < locSplit.length; i += 1) {
    point = `/${locSplit[i]}${point}`;
    pointers.push(point);
  }

  let example;
  const rev = [...examples].reverse();

  for (let i = 0; i < pointers.length; i += 1) {
    for (let ii = 0; ii < rev.length; ii += 1) {
      let schema = rev[ii];
      if ('example' in schema) {
        schema = schema.example;
      } else {
        if (!Array.isArray(schema.examples) || !schema.examples.length) {
          continue;
        }

        // Prevent us from crashing if `examples` is a completely empty object.
        schema = schema.examples.shift();
      }

      try {
        example = jsonpointer.get(schema, pointers[i]);
      } catch (err) {
        // If the schema we're looking at is `{obj: null}` and our pointer if `/obj/propertyName`
        // jsonpointer will throw an error. If that happens, we should silently catch and toss it
        // and return no example.
      }

      if (example !== undefined) {
        break;
      }
    }

    if (example !== undefined) {
      break;
    }
  }

  return example;
}

/**
 * Given an OpenAPI-flavored JSON Schema, make an effort to modify it so it's shaped more towards
 * stock JSON Schema.
 *
 * Why do this?
 *
 *  1. OpenAPI 3.0.x supports its own flavor of JSON Schema that isn't fully compatible with most
 *    JSON Schema tooling (like `@readme/oas-form` or `@rjsf/core`).
 *  2. While validating an OpenAPI definition will prevent corrupted or improper schemas from
 *    occuring, we have a lot of legacy schemas in ReadMe that were ingested before we had proper
 *    validation in place, and as a result have some API definitions that will not pass validation
 *    right now. In addition to reshaping OAS-JSON Schema into JSON Schema this library will also
 *    fix these improper schemas: things like `type: object` having `items` instead of `properties`,
 *    or `type: array` missing `items`.
 *  3. To ease the burden of polymorphic handling on our form rendering engine we make an attempt
 *    to merge `allOf` schemas here.
 *  4. Additionally due to OpenAPI 3.0.x not supporting JSON Schema, in order to support the
 *    `example` keyword that OAS supports, we need to do some work in here to remap it into
 *    `examples`. However, since all we care about in respect to examples for usage within
 *    `@readme/oas-form`, we're only retaining primitives. This *slightly* deviates from JSON
 *    Schema in that JSON Schema allows for any schema to be an example, but since
 *    `@readme/oas-form` can only actually **render** primitives, that's what we're retaining.
 *  5. Though OpenAPI 3.1 does support full JSON Schema, this library should be able to handle it
 *    without any problems.
 *
 * And why use this over `@openapi-contrib/openapi-schema-to-json-schema`? Fortunately and
 * unfortunately we've got a lot of API definitions in our database that aren't currently valid so
 * we need to have a lot of bespoke handling for odd quirks, typos, and missing declarations that
 * might be present.
 *
 * @todo add support for `schema: false` and `not` cases.
 * @see {@link https://json-schema.org/draft/2019-09/json-schema-validation.html}
 * @see {@link https://github.com/OAI/OpenAPI-Specification/blob/main/versions/3.0.3.md#schemaObject}
 * @see {@link https://github.com/OAI/OpenAPI-Specification/blob/main/versions/3.1.0.md#schemaObject}
 * @param data OpenAPI Schema Object to convert to pure JSON Schema.
 */
export default function toJSONSchema(
  data: RMOAS.SchemaObject | boolean,
  opts: toJSONSchemaOptions = {}
): RMOAS.SchemaObject {
  let schema = data === true ? {} : { ...data };
  const schemaAdditionalProperties = RMOAS.isSchema(schema) ? schema.additionalProperties : null;

  const {
    addEnumsToDescriptions,
    currentLocation,
    globalDefaults,
    isPolymorphicAllOfChild,
    prevSchemas,
    refLogger,
    transformer,
  } = {
    addEnumsToDescriptions: false,
    currentLocation: '',
    globalDefaults: {},
    isPolymorphicAllOfChild: false,
    prevSchemas: [] as PrevSchemasType,
    refLogger: () => true,
    transformer: (s: RMOAS.SchemaObject) => s,
    ...opts,
  };

  // If this schema contains a `$ref`, it's circular and we shouldn't try to resolve it. Just
  // return and move along.
  if (RMOAS.isRef(schema)) {
    refLogger(schema.$ref, 'ref');

    return transformer({
      $ref: schema.$ref,
    });
  }

  // If we don't have a set type, but are dealing with an `anyOf`, `oneOf`, or `allOf`
  // representation let's run through them and make sure they're good.
  if (RMOAS.isSchema(schema, isPolymorphicAllOfChild)) {
    // If this is an `allOf` schema we should make an attempt to merge so as to ease the burden on
    // the tooling that ingests these schemas.
    if ('allOf' in schema && Array.isArray(schema.allOf)) {
      try {
        schema = mergeJSONSchemaAllOf(schema as RMOAS.JSONSchema, {
          ignoreAdditionalProperties: true,
          resolvers: {
            // JSON Schema ony supports examples with the `examples` property, since we're
            // ingesting OpenAPI definitions we need to add a custom resolver for its `example`
            // property.
            example: (obj: unknown[]) => obj[0],

            // JSON Schema has no support for `format` on anything other than `string`, but since
            // OpenAPI has it on `integer` and `number` we need to add a custom resolver here so we
            // can still merge schemas that may have those.
            format: (obj: string[]) => obj[0],

            // Since JSON Schema obviously doesn't know about our vendor extension we need to tell
            // the library to essentially ignore and pass it along.
            'x-readme-ref-name': (obj: string[]) => obj[0],
          } as unknown,
        }) as RMOAS.SchemaObject;
      } catch (e) {
        // If we can't merge the `allOf` for whatever reason (like if one item is a `string` and
        // the other is a `object`) then we should completely remove it from the schema and continue
        // with whatever we've got. Why? If we don't, any tooling that's ingesting this will need
        // to account for the incompatible `allOf` and it may be subject to more breakages than
        // just not having it present would be.
        const { ...schemaWithoutAllOf } = schema;
        schema = schemaWithoutAllOf as RMOAS.SchemaObject;
        delete schema.allOf;
      }
    }

    ['anyOf', 'oneOf'].forEach((polyType: 'anyOf' | 'oneOf') => {
      if (polyType in schema && Array.isArray(schema[polyType])) {
        schema[polyType].forEach((item, idx) => {
          const polyOptions: toJSONSchemaOptions = {
            addEnumsToDescriptions,
            currentLocation: `${currentLocation}/${idx}`,
            globalDefaults,
            isPolymorphicAllOfChild: false,
            prevSchemas,
            refLogger,
            transformer,
          };

          // When `properties` or `items` are present alongside a polymorphic schema instead of
          // letting whatever JSON Schema interpreter is handling these constructed schemas we can
          // guide its hand a bit by manually transforming it into an inferred `allOf` of the
          // `properties` + the polymorph schema.
          //
          // This `allOf` schema will be merged together when fed through `toJSONSchema`.
          if ('properties' in schema) {
            schema[polyType][idx] = toJSONSchema(
              { allOf: [item, { properties: schema.properties }] } as RMOAS.SchemaObject,
              polyOptions
            );
          } else if ('items' in schema) {
            schema[polyType][idx] = toJSONSchema(
              { allOf: [item, { items: schema.items }] } as RMOAS.SchemaObject,
              polyOptions
            );
          } else {
            schema[polyType][idx] = toJSONSchema(item as RMOAS.SchemaObject, polyOptions);
          }
        });
      }
    });

    if ('discriminator' in schema) {
      if ('mapping' in schema.discriminator && typeof schema.discriminator.mapping === 'object') {
        // Discriminator mappings aren't written as traditional `$ref` pointers so in order to log
        // them to the supplied `refLogger`.
        const mapping = schema.discriminator.mapping;
        Object.keys(mapping).forEach(k => {
          refLogger(mapping[k], 'discriminator');
        });
      }
    }
  }

  // If this schema is malformed for some reason, let's do our best to repair it.
  if (!('type' in schema) && !isPolymorphicSchema(schema) && !isRequestBodySchema(schema)) {
    if ('properties' in schema) {
      schema.type = 'object';
    } else if ('items' in schema) {
      schema.type = 'array';
    } else {
      // If there's still no `type` on the schema we should leave it alone because we don't have a
      // great way to know if it's part of a nested schema that should, and couldn't be merged,
      // into another, or it's just purely malformed.
      //
      // Whatever tooling that ingests the generated schema should handle it however it needs to.
    }
  }

  if (RMOAS.isSchema(schema, isPolymorphicAllOfChild)) {
    // JSON Schema doesn't support OpenAPI-style examples so we need to reshape them a bit.
    if ('example' in schema) {
      // Only bother adding primitive examples.
      if (isPrimitive(schema.example)) {
        schema.examples = [schema.example];
      } else if (Array.isArray(schema.example)) {
        schema.examples = schema.example.filter(example => isPrimitive(example));
        if (!schema.examples.length) {
          delete schema.examples;
        }
      } else {
        prevSchemas.push({ example: schema.example });
      }

      delete schema.example;
    } else if ('examples' in schema) {
      let reshapedExamples = false;
      if (typeof schema.examples === 'object' && !Array.isArray(schema.examples)) {
        const examples: unknown[] = [];
        Object.keys(schema.examples).forEach(name => {
          const example = schema.examples[name as unknown as number];
          if ('$ref' in example) {
            // no-op because any `$ref` example here after dereferencing is circular so we should
            // ignore it
            refLogger(example.$ref, 'ref');
          } else if ('value' in example) {
            if (isPrimitive(example.value)) {
              examples.push(example.value);
              reshapedExamples = true;
            } else if (Array.isArray(example.value) && isPrimitive(example.value[0])) {
              examples.push(example.value[0]);
              reshapedExamples = true;
            } else {
              // If this example is neither a primitive or an array we should dump it into the
              // `prevSchemas` array because we might be able to extract an example from it further
              // downstream.
              prevSchemas.push({
                example: example.value,
              });
            }
          }
        });

        if (examples.length) {
          reshapedExamples = true;
          schema.examples = examples;
        }
      } else if (Array.isArray(schema.examples) && isPrimitive(schema.examples[0])) {
        // We haven't reshaped `examples` here, but since it's in a state that's preferrable to us
        // let's keep it around.
        reshapedExamples = true;
      }

      if (!reshapedExamples) {
        delete schema.examples;
      }
    }

    // If we didn't have any immediately defined examples, let's search backwards and see if we can
    // find one. But as we're only looking for primitive example, only try to search for one if
    // we're dealing with a primitive schema.
    if (schema.type !== 'array' && schema.type !== 'object' && !schema.examples) {
      const foundExample = searchForExampleByPointer(currentLocation, prevSchemas);
      if (foundExample) {
        // We can only really deal with primitives, so only promote those as the found example if
        // it is.
        if (isPrimitive(foundExample) || (Array.isArray(foundExample) && isPrimitive(foundExample[0]))) {
          schema.examples = [foundExample];
        }
      }
    }

    if (schema.type === 'array') {
      if ('items' in schema) {
        if (!Array.isArray(schema.items) && Object.keys(schema.items).length === 1 && RMOAS.isRef(schema.items)) {
          // `items` contains a `$ref`, so since it's circular we should do a no-op here and log
          // and ignore it.
          refLogger(schema.items.$ref, 'ref');
        } else if (schema.items !== true) {
          // Run through the arrays contents and clean them up.
          schema.items = toJSONSchema(schema.items as RMOAS.SchemaObject, {
            addEnumsToDescriptions,
            currentLocation: `${currentLocation}/0`,
            globalDefaults,
            prevSchemas,
            refLogger,
            transformer,
          });
        }
      } else if ('properties' in schema || 'additionalProperties' in schema) {
        // This is a fix to handle cases where someone may have typod `items` as `properties` on an
        // array. Since throwing a complete failure isn't ideal, we can see that they meant for the
        // type to be `object`, so we can do our best to shape the data into what they were
        // intending it to be.
        // README-6R
        schema.type = 'object';
      } else {
        // This is a fix to handle cases where we have a malformed array with no `items` property
        // present.
        // README-8E
        schema.items = {};
      }
    } else if (schema.type === 'object') {
      if ('properties' in schema) {
        Object.keys(schema.properties).forEach(prop => {
          if (
            Array.isArray(schema.properties[prop]) ||
            (typeof schema.properties[prop] === 'object' && schema.properties[prop] !== null)
          ) {
            schema.properties[prop] = toJSONSchema(schema.properties[prop] as RMOAS.SchemaObject, {
              addEnumsToDescriptions,
              currentLocation: `${currentLocation}/${encodePointer(prop)}`,
              globalDefaults,
              prevSchemas,
              refLogger,
              transformer,
            });
          }
        });
      }

      if (typeof schemaAdditionalProperties === 'object' && schemaAdditionalProperties !== null) {
        // If this `additionalProperties` is completely empty and devoid of any sort of schema,
        // treat it as such. Otherwise let's recurse into it and see if we can sort it out.
        if (
          !('type' in schemaAdditionalProperties) &&
          !('$ref' in schemaAdditionalProperties) &&
          // We know it will be a schema object because it's dereferenced
          !isPolymorphicSchema(schemaAdditionalProperties as RMOAS.SchemaObject)
        ) {
          schema.additionalProperties = true;
        } else {
          // We know it will be a schema object because it's dereferenced
          schema.additionalProperties = toJSONSchema(schemaAdditionalProperties as RMOAS.SchemaObject, {
            addEnumsToDescriptions,
            currentLocation,
            globalDefaults,
            prevSchemas,
            refLogger,
            transformer,
          });
        }
      }

      // Since neither `properties` and `additionalProperties` are actually required to be present
      // on an object, since we construct this schema work to build up a form we still need
      // *something* for the user to enter in for this object so we'll add back in
      // `additionalProperties` for that.
      if (!isPolymorphicSchema(schema) && !('properties' in schema) && !('additionalProperties' in schema)) {
        schema.additionalProperties = true;
      }
    }
  }

  // Ensure that number schemas formats have properly constrained min/max attributes according to
  // whatever type of `format` and `type` they adhere to.
  if ('format' in schema) {
    const formatUpper = schema.format.toUpperCase();

    if (`${formatUpper}_MIN` in FORMAT_OPTIONS) {
      if ((!schema.minimum && schema.minimum !== 0) || schema.minimum < FORMAT_OPTIONS[`${formatUpper}_MIN`]) {
        schema.minimum = FORMAT_OPTIONS[`${formatUpper}_MIN`];
      }
    }

    if (`${formatUpper}_MAX` in FORMAT_OPTIONS) {
      if ((!schema.maximum && schema.maximum !== 0) || schema.maximum > FORMAT_OPTIONS[`${formatUpper}_MAX`]) {
        schema.maximum = FORMAT_OPTIONS[`${formatUpper}_MAX`];
      }
    }
  }

  /**
   * Users can pass in parameter defaults via JWT User Data. We're checking to see if the defaults
   * being passed in exist on endpoints via jsonpointer
   *
   * @see {@link https://docs.readme.com/docs/passing-data-to-jwt}
   */
  if (
    RMOAS.isSchema(schema, isPolymorphicAllOfChild) &&
    globalDefaults &&
    Object.keys(globalDefaults).length > 0 &&
    currentLocation
  ) {
    try {
      const userJwtDefault = jsonpointer.get(globalDefaults, currentLocation);
      if (userJwtDefault) {
        schema.default = userJwtDefault;
      }
    } catch (err) {
      // If jsonpointer returns an error, we won't show any defaults for that path.
    }
  }

  // Only add a default value if we actually have one.
  if ('default' in schema && typeof schema.default !== 'undefined') {
    if (('allowEmptyValue' in schema && schema.allowEmptyValue && schema.default === '') || schema.default !== '') {
      // If we have `allowEmptyValue` present, and the default is actually an empty string, let it
      // through as it's allowed.
    } else {
      // If the default is empty and we don't want to allowEmptyValue, we need to remove the
      // default.
      delete schema.default;
    }
  }

  if (RMOAS.isSchema(schema, isPolymorphicAllOfChild) && 'enum' in schema && Array.isArray(schema.enum)) {
    // Enums should not have duplicated items as those will break AJV validation.
    // If we ever target ES6 for typescript we can drop this array.from.
    // https://stackoverflow.com/questions/33464504/using-spread-syntax-and-new-set-with-typescript/56870548
    schema.enum = Array.from(new Set(schema.enum));

    // If we want to add enums to descriptions (like in the case of response JSON Schema)
    // generation we need to convert them into a list of Markdown tilda'd strings. We're also
    // filtering away empty and falsy strings here because adding empty `` blocks to the description
    // will serve nobody any good.
    if (addEnumsToDescriptions) {
      const enums = schema.enum
        .filter(Boolean)
        .map(str => `\`${str}\``)
        .join(' ');

      if (enums.length) {
        if ('description' in schema) {
          schema.description += `\n\n${enums}`;
        } else {
          schema.description = enums;
        }
      }
    }
  }

  // Clean up any remaining `items` or `properties` schema fragments lying around if there's also
  // polymorphism present.
  if ('anyOf' in schema || 'oneOf' in schema) {
    if ('properties' in schema) {
      delete schema.properties;
    }

    if ('items' in schema) {
      delete schema.items;
    }
  }

  // Remove unsupported JSON Schema props.
  for (let i = 0; i < UNSUPPORTED_SCHEMA_PROPS.length; i += 1) {
    // Using the as here because the purpose is to delete keys we don't expect, so of course the
    // typing won't work
    delete (schema as Record<string, unknown>)[UNSUPPORTED_SCHEMA_PROPS[i]];
  }

  return transformer(schema);
}