import * as fs from 'fs';
import * as minimatch from 'minimatch';
import fetch from 'node-fetch';
import * as pluralize from 'pluralize';

import { parseYaml } from './js-yaml';
import { HttpResolveConfig } from './config/config';
import { UserContext } from './walk';

export { parseYaml, stringifyYaml } from './js-yaml';

export type StackFrame<T> = {
  prev: StackFrame<T> | null;
  value: T;
};

export type Stack<T> = StackFrame<T> | null;
export type StackNonEmpty<T> = StackFrame<T>;
export function pushStack<T, P extends Stack<T> = Stack<T>>(head: P, value: T) {
  return { prev: head, value };
}

export function popStack<T, P extends Stack<T>>(head: P) {
  return head?.prev ?? null;
}

export type BundleOutputFormat = 'json' | 'yml' | 'yaml';

export async function loadYaml(filename: string) {
  const contents = await fs.promises.readFile(filename, 'utf-8');
  return parseYaml(contents);
}

export function notUndefined<T>(x: T | undefined): x is T {
  return x !== undefined;
}

export function isPlainObject(value: any): value is object {
  return value !== null && typeof value === 'object' && !Array.isArray(value);
}

export function isEmptyObject(value: any): value is object {
  return isPlainObject(value) && Object.keys(value).length === 0;
}

export function isEmptyArray(value: any) {
  return Array.isArray(value) && value.length === 0;
}

export async function readFileFromUrl(url: string, config: HttpResolveConfig) {
  const headers: Record<string, string> = {};
  for (const header of config.headers) {
    if (match(url, header.matches)) {
      headers[header.name] =
        header.envVariable !== undefined ? process.env[header.envVariable] || '' : header.value;
    }
  }

  const req = await (config.customFetch || fetch)(url, {
    headers: headers,
  });

  if (!req.ok) {
    throw new Error(`Failed to load ${url}: ${req.status} ${req.statusText}`);
  }

  return { body: await req.text(), mimeType: req.headers.get('content-type') };
}

export function match(url: string, pattern: string) {
  if (!pattern.match(/^https?:\/\//)) {
    // if pattern doesn't specify protocol directly, do not match against it
    url = url.replace(/^https?:\/\//, '');
  }
  return minimatch(url, pattern);
}

export function pickObjectProps<T extends Record<string, unknown>>(
  object: T,
  keys: Array<string>,
): T {
  return Object.fromEntries(
    keys.filter((key: string) => key in object).map((key: string) => [key, object[key]]),
  ) as T;
}

export function omitObjectProps<T extends Record<string, unknown>>(
  object: T,
  keys: Array<string>,
): T {
  return Object.fromEntries(Object.entries(object).filter(([key]) => !keys.includes(key))) as T;
}

export function splitCamelCaseIntoWords(str: string) {
  const camel = str
    .split(/(?:[-._])|([A-Z][a-z]+)/)
    .filter(Boolean)
    .map((item) => item.toLocaleLowerCase());
  const caps = str
    .split(/([A-Z]{2,})/)
    .filter((e: string) => e && e === e.toUpperCase())
    .map((item) => item.toLocaleLowerCase());
  return new Set([...camel, ...caps]);
}

export function validateMimeType(
  { type, value }: any,
  { report, location }: UserContext,
  allowedValues: string[],
) {
  const ruleType = type === 'consumes' ? 'request' : 'response';
  if (!allowedValues)
    throw new Error(`Parameter "allowedValues" is not provided for "${ruleType}-mime-type" rule`);
  if (!value[type]) return;

  for (const mime of value[type]) {
    if (!allowedValues.includes(mime)) {
      report({
        message: `Mime type "${mime}" is not allowed`,
        location: location.child(value[type].indexOf(mime)).key(),
      });
    }
  }
}

export function validateMimeTypeOAS3(
  { type, value }: any,
  { report, location }: UserContext,
  allowedValues: string[],
) {
  const ruleType = type === 'consumes' ? 'request' : 'response';
  if (!allowedValues)
    throw new Error(`Parameter "allowedValues" is not provided for "${ruleType}-mime-type" rule`);
  if (!value.content) return;

  for (const mime of Object.keys(value.content)) {
    if (!allowedValues.includes(mime)) {
      report({
        message: `Mime type "${mime}" is not allowed`,
        location: location.child('content').child(mime).key(),
      });
    }
  }
}

export function isSingular(path: string) {
  return pluralize.isSingular(path);
}

export function readFileAsStringSync(filePath: string) {
  return fs.readFileSync(filePath, 'utf-8');
}

export function isPathParameter(pathSegment: string) {
  return pathSegment.startsWith('{') && pathSegment.endsWith('}');
}


/**
 * Convert Windows backslash paths to slash paths: foo\\bar ➔ foo/bar
 */
 export function slash(path: string): string {
  const isExtendedLengthPath = /^\\\\\?\\/.test(path)
  if (isExtendedLengthPath) {
    return path
  }

  return path.replace(/\\/g, '/');
}

export function isNotEmptyObject(obj: any) {
  return !!obj && Object.keys(obj).length > 0;
}