import type { OpenAPIV3 } from '@gitbook/openapi-parser';
import { checkIsReference } from './utils';

type JSONValue = string | number | boolean | null | JSONValue[] | { [key: string]: JSONValue };

type ScalarGetExampleFromSchemaOptions = NonNullable<Parameters<typeof getExampleFromSchema>[1]>;
type GenerateSchemaExampleOptions = Pick<
    ScalarGetExampleFromSchemaOptions,
    'xml' | 'omitEmptyAndOptionalProperties' | 'mode'
>;

/**
 * Generate a JSON example from a schema
 */
export function generateSchemaExample(
    schema: OpenAPIV3.SchemaObject,
    options?: GenerateSchemaExampleOptions
): JSONValue | undefined {
    return getExampleFromSchema(
        schema,
        {
            emptyString: 'text',
            ...options,
        },
        3 // Max depth for circular references
    );
}

/**
 * Generate an example for a media type.
 */
export function generateMediaTypeExamples(
    mediaType: OpenAPIV3.MediaTypeObject,
    options?: GenerateSchemaExampleOptions
): OpenAPIV3.ExampleObject[] {
    if (mediaType.example) {
        return [{ summary: 'default', value: mediaType.example }];
    }

    if (mediaType.examples) {
        const { examples } = mediaType;
        const keys = Object.keys(examples);
        if (keys.length > 0) {
            return keys.reduce<OpenAPIV3.ExampleObject[]>((result, key) => {
                const example = examples[key];
                if (!example || checkIsReference(example)) {
                    return result;
                }
                result.push({
                    summary: example.summary || key,
                    value: example.value,
                    description: example.description,
                    externalValue: example.externalValue,
                });
                return result;
            }, []);
        }
    }

    if (mediaType.schema) {
        return [{ summary: 'default', value: generateSchemaExample(mediaType.schema, options) }];
    }

    return [];
}

/** Hard limit for rendering circular references */
const MAX_LEVELS_DEEP = 5;

const genericExampleValues: Record<string, string> = {
    'date-time': new Date().toISOString(),
    date: new Date().toISOString().split('T')[0] ?? '1970-01-01',
    email: 'name@gmail.com',
    hostname: 'example.com',
    ipv4: '0.0.0.0',
    ipv6: '2001:0db8:85a3:0000:0000:8a2e:0370:7334',
    uri: 'https://example.com',
    uuid: '123e4567-e89b-12d3-a456-426614174000',
    binary: 'binary',
    byte: 'Ynl0ZXM=',
    password: 'password',
    'idn-email': 'jane.doe@example.com',
    'idn-hostname': 'example.com',
    'iri-reference': '/entitiy/1',
    // https://tools.ietf.org/html/rfc3987
    iri: 'https://example.com/entity/123',
    'json-pointer': '/nested/objects',
    regex: '/[a-z]/',
    // https://tools.ietf.org/html/draft-handrews-relative-json-pointer-01
    'relative-json-pointer': '1/nested/objects',
    // full-time in https://tools.ietf.org/html/rfc3339#section-5.6
    time: new Date().toISOString().split('T')[1]?.split('.')[0] ?? '00:00:00Z',
    // either a URI or relative-reference https://tools.ietf.org/html/rfc3986#section-4.1
    'uri-reference': '../folder',
    'uri-template': 'https://example.com/{id}',
    'object-id': '6592008029c8c3e4dc76256c',
};

/**
 * We can use the `format` to generate some random values.
 */
function guessFromFormat(schema: Record<string, any>, fallback = '') {
    return genericExampleValues[schema.format] ?? fallback;
}

/** Map of all the results */
const resultCache = new WeakMap<Record<string, any>, any>();

/** Store result in the cache, and return the result */
function cache(schema: Record<string, any>, result: unknown) {
    // Avoid unnecessary WeakMap operations for primitive values
    if (typeof result !== 'object' || result === null) {
        return result;
    }

    resultCache.set(schema, result);

    return result;
}

/**
 * This function takes an OpenAPI schema and generates an example from it
 * Forked from : https://github.com/scalar/scalar/blob/main/packages/oas-utils/src/spec-getters/getExampleFromSchema.ts
 */
const getExampleFromSchema = (
    schema: Record<string, any>,
    options?: {
        /**
         * The fallback string for empty string values.
         * @default ''
         */
        emptyString?: string;
        /**
         * Whether to use the XML tag names as keys
         * @default false
         */
        xml?: boolean;
        /**
         * Whether to show read-only/write-only properties. Otherwise all properties are shown.
         * @default undefined
         */
        mode?: 'read' | 'write';
        /**
         * Dynamic values to add to the example.
         */
        variables?: Record<string, any>;
        /**
         * Whether to omit empty and optional properties.
         * @default false
         */
        omitEmptyAndOptionalProperties?: boolean;
    },
    level = 0,
    parentSchema?: Record<string, any>,
    name?: string
): any => {
    // Check if the result is already cached
    if (resultCache.has(schema)) {
        return resultCache.get(schema);
    }

    // Check whether it’s a circular reference
    if (level === MAX_LEVELS_DEEP + 1) {
        try {
            // Fails if it contains a circular reference
            JSON.stringify(schema);
        } catch {
            return '[Circular Reference]';
        }
    }

    // Sometimes, we just want the structure and no values.
    // But if `emptyString` is  set, we do want to see some values.
    const makeUpRandomData = !!options?.emptyString;

    // Check if the property is read-only/write-only
    if (
        (options?.mode === 'write' && schema.readOnly) ||
        (options?.mode === 'read' && schema.writeOnly)
    ) {
        return undefined;
    }

    // Use given variables as values
    if (schema['x-variable']) {
        const value = options?.variables?.[schema['x-variable']];

        // Return the value if it’s defined
        if (value !== undefined) {
            // Type-casting
            if (schema.type === 'number' || schema.type === 'integer') {
                return Number.parseInt(value, 10);
            }

            return cache(schema, value);
        }
    }

    // Use the first example, if there’s an array
    if (Array.isArray(schema.examples) && schema.examples.length > 0) {
        return cache(schema, schema.examples[0]);
    }

    // Use an example, if there’s one
    if (schema.example !== undefined) {
        return cache(schema, schema.example);
    }

    // enum: [ 'available', 'pending', 'sold' ]
    if (Array.isArray(schema.enum) && schema.enum.length > 0) {
        return cache(schema, schema.enum[0]);
    }

    // Check if the property is required
    const isObjectOrArray =
        schema.type === 'object' ||
        schema.type === 'array' ||
        !!schema.allOf?.at?.(0) ||
        !!schema.anyOf?.at?.(0) ||
        !!schema.oneOf?.at?.(0);
    if (!isObjectOrArray && options?.omitEmptyAndOptionalProperties === true) {
        const isRequired =
            schema.required === true ||
            parentSchema?.required === true ||
            parentSchema?.required?.includes(name ?? schema.name);

        if (!isRequired) {
            return undefined;
        }
    }

    // Object
    if (schema.type === 'object' || schema.properties !== undefined) {
        const response: Record<string, any> = {};

        // Regular properties
        if (schema.properties !== undefined) {
            for (const propertyName in schema.properties) {
                if (Object.prototype.hasOwnProperty.call(schema.properties, propertyName)) {
                    const property = schema.properties[propertyName];
                    const propertyXmlTagName = options?.xml ? property.xml?.name : undefined;

                    response[propertyXmlTagName ?? propertyName] = getExampleFromSchema(
                        property,
                        options,
                        level + 1,
                        schema,
                        propertyName
                    );

                    if (typeof response[propertyXmlTagName ?? propertyName] === 'undefined') {
                        delete response[propertyXmlTagName ?? propertyName];
                    }
                }
            }
        }

        // Pattern properties (regex)
        if (schema.patternProperties !== undefined) {
            for (const pattern in schema.patternProperties) {
                if (Object.prototype.hasOwnProperty.call(schema.patternProperties, pattern)) {
                    const property = schema.patternProperties[pattern];

                    // Use the regex pattern as an example key
                    const exampleKey = pattern;

                    response[exampleKey] = getExampleFromSchema(
                        property,
                        options,
                        level + 1,
                        schema,
                        exampleKey
                    );
                }
            }
        }

        // Additional properties
        if (schema.additionalProperties !== undefined) {
            const anyTypeIsValid =
                // true
                schema.additionalProperties === true ||
                // or an empty object {}
                (typeof schema.additionalProperties === 'object' &&
                    !Object.keys(schema.additionalProperties).length);

            if (anyTypeIsValid) {
                response.ANY_ADDITIONAL_PROPERTY = 'anything';
            } else if (schema.additionalProperties !== false) {
                response.ANY_ADDITIONAL_PROPERTY = getExampleFromSchema(
                    schema.additionalProperties,
                    options,
                    level + 1
                );
            }
        }

        if (schema.anyOf !== undefined) {
            Object.assign(response, getExampleFromSchema(schema.anyOf[0], options, level + 1));
        } else if (schema.oneOf !== undefined) {
            Object.assign(response, getExampleFromSchema(schema.oneOf[0], options, level + 1));
        } else if (schema.allOf !== undefined) {
            Object.assign(
                response,
                ...schema.allOf
                    .map((item: Record<string, any>) =>
                        getExampleFromSchema(item, options, level + 1, schema)
                    )
                    .filter((item: any) => item !== undefined)
            );
        }

        return cache(schema, response);
    }

    // Array
    if (schema.type === 'array' || schema.items !== undefined) {
        const itemsXmlTagName = schema?.items?.xml?.name;
        const wrapItems = !!(options?.xml && schema.xml?.wrapped && itemsXmlTagName);

        if (schema.example !== undefined) {
            return cache(
                schema,
                wrapItems ? { [itemsXmlTagName]: schema.example } : schema.example
            );
        }

        // Check whether the array has a anyOf, oneOf, or allOf rule
        if (schema.items) {
            // First handle allOf separately since it needs special handling
            if (schema.items.allOf) {
                // If the first item is an object type, merge all schemas
                if (schema.items.allOf[0].type === 'object') {
                    const mergedExample = getExampleFromSchema(
                        { type: 'object', allOf: schema.items.allOf },
                        options,
                        level + 1,
                        schema
                    );

                    return cache(
                        schema,
                        wrapItems ? [{ [itemsXmlTagName]: mergedExample }] : [mergedExample]
                    );
                }
                // For non-objects (like strings), collect all examples
                const examples = schema.items.allOf
                    .map((item: Record<string, any>) =>
                        getExampleFromSchema(item, options, level + 1, schema)
                    )
                    .filter((item: any) => item !== undefined);

                return cache(
                    schema,
                    wrapItems
                        ? examples.map((example: any) => ({ [itemsXmlTagName]: example }))
                        : examples
                );
            }

            // Handle other rules (anyOf, oneOf)
            const rules = ['anyOf', 'oneOf'];
            for (const rule of rules) {
                if (!schema.items[rule]) {
                    continue;
                }

                const schemas = schema.items[rule].slice(0, 1);
                const exampleFromRule = schemas
                    .map((item: Record<string, any>) =>
                        getExampleFromSchema(item, options, level + 1, schema)
                    )
                    .filter((item: any) => item !== undefined);

                return cache(
                    schema,
                    wrapItems ? [{ [itemsXmlTagName]: exampleFromRule }] : exampleFromRule
                );
            }
        }

        if (schema.items?.type) {
            const exampleFromSchema = getExampleFromSchema(schema.items, options, level + 1);

            return wrapItems ? [{ [itemsXmlTagName]: exampleFromSchema }] : [exampleFromSchema];
        }

        return [];
    }

    const exampleValues: Record<any, any> = {
        string: makeUpRandomData ? guessFromFormat(schema, options?.emptyString) : '',
        boolean: true,
        integer: schema.min ?? 1,
        number: schema.min ?? 1,
        array: [],
    };

    if (schema.type !== undefined && exampleValues[schema.type] !== undefined) {
        return cache(schema, exampleValues[schema.type]);
    }

    const discriminateSchema = schema.oneOf || schema.anyOf;
    // Check if property has the `oneOf` | `anyOf` key
    if (Array.isArray(discriminateSchema) && discriminateSchema.length > 0) {
        // Get the first item from the `oneOf` | `anyOf` array
        const firstOneOfItem = discriminateSchema[0];

        // Return an example for the first item
        return getExampleFromSchema(firstOneOfItem, options, level + 1);
    }

    // Check if schema has the `allOf` key
    if (Array.isArray(schema.allOf)) {
        let example: any = null;

        // Loop through all `allOf` schemas
        schema.allOf.forEach((allOfItem: Record<string, any>) => {
            // Return an example from the schema
            const newExample = getExampleFromSchema(allOfItem, options, level + 1);

            // Merge or overwrite the example
            example =
                typeof newExample === 'object' && typeof example === 'object'
                    ? {
                          ...(example ?? {}),
                          ...newExample,
                      }
                    : Array.isArray(newExample) && Array.isArray(example)
                      ? [...(example ?? {}), ...newExample]
                      : newExample;
        });

        return cache(schema, example);
    }

    // Check if schema is a union type
    if (Array.isArray(schema.type)) {
        // Return null if the type is nullable
        if (schema.type.includes('null')) {
            return null;
        }
        // Return an example for the first type in the union
        const exampleValue = exampleValues[schema.type[0]];
        if (exampleValue !== undefined) {
            return cache(schema, exampleValue);
        }
    }

    // Warn if the type is unknown …
    // console.warn(`[getExampleFromSchema] Unknown property type "${schema.type}".`)

    // … and just return null for now.
    return null;
};