import { AlephaError } from "alepha";

export abstract class RouterProvider<T extends Route = Route> {
  protected routePathRegex: RegExp = /^\/[A-Za-z0-9._~!$&%'()*+,;=:@{}?/-]*$/;

  protected tree: Tree<T> = { children: {} };
  protected cache = new Map<string, RouteMatch<T>>();
  protected maxCacheSize = 10_000;

  public match(path: string): RouteMatch<T> {
    const pathname = path.split("?", 1)[0];
    const hit = this.cache.get(pathname);
    if (hit) {
      return { route: hit.route, params: { ...hit.params } };
    }
    const result = this.mapParams(this.createRouteMatch(pathname));
    if (this.cache.size >= this.maxCacheSize) this.cache.clear();
    this.cache.set(pathname, result);
    return { route: result.route, params: { ...result.params } };
  }

  protected test(path: string): void {
    if (!this.routePathRegex.test(path)) {
      throw new AlephaError(`Route '${path}' is not valid`);
    }
  }

  protected push(route: T): void {
    const path = route.path.replaceAll("//", "/");

    this.test(path);
    this.cache.clear();

    const parts = this.createParts(path);

    let cursor = this.tree;
    for (let i = 0; i < parts.length; i++) {
      const isLast = i === parts.length - 1;
      let part = parts[i].toLowerCase(); // url is case-insensitive
      if (part === "*" && isLast) {
        cursor.wildcard = { route };
        break;
      }

      if (part.includes("*")) {
        throw new AlephaError(`Route '${path}' has an invalid wildcard syntax`);
      }

      if (part.includes("{") || part.includes("}")) {
        if (part.startsWith("{") && part.endsWith("}")) {
          part = `:${part.slice(1, -1)}`; // convert {param} to :param
        } else {
          throw new AlephaError(`Route '${path}' has an invalid param syntax`);
        }
      }

      if (part.startsWith(":")) {
        const name = parts[i].slice(1).replaceAll("}", "");
        if (!name) {
          throw new AlephaError(`Route '${path}' has an empty param name`);
        }
        if (!cursor.param) {
          cursor.param = { name, children: {} };
        } else if (cursor.param.name !== name) {
          // damn, 2 url params with different names
          // got this case with /customers/:id and /customers/:userId/payments
          route.mapParams ??= {};
          route.mapParams[cursor.param.name] = name;
        }

        if (isLast) {
          cursor.param.route = route;
        }

        cursor = cursor.param;
        continue;
      }

      if (!cursor.children[part]) {
        cursor.children[part] = { children: {} };
      }

      if (isLast) {
        cursor.children[part].route = route;
      }

      cursor = cursor.children[part];
    }
  }

  protected createRouteMatch(path: string): RouteMatch<T> {
    if (path[0] !== "/") {
      throw new AlephaError(`Path '${path}' must start with "/"`);
    }

    const parts = this.createParts(path);

    let cursor = this.tree;
    let wildcard: { route: T } | undefined;
    const params: Record<string, string> = {};

    for (let i = 0; i < parts.length; i++) {
      const part = parts[i].toLowerCase(); // url is case-insensitive
      if (cursor.children[part]) {
        if (cursor.wildcard) {
          wildcard = cursor.wildcard;
        }
        cursor = cursor.children[part];
      } else if (cursor.param) {
        if (cursor.wildcard) {
          wildcard = cursor.wildcard;
        }
        params[cursor.param.name] = parts[i];
        cursor = cursor.param;
      } else if (cursor.wildcard) {
        params["*"] = parts.slice(i).join("/");
        return { route: cursor.wildcard.route, params };
      } else {
        return { route: wildcard?.route, params };
      }
    }

    if (!cursor?.route) {
      // when "/a/*" - trigger if "/a"
      if (cursor.wildcard) {
        return { route: cursor.wildcard.route, params };
      }
      // return deep wildcard or nothing
      return { route: wildcard?.route, params };
    }

    return { route: cursor.route, params };
  }

  protected mapParams(match: RouteMatch<T>): RouteMatch<T> {
    if (match.route?.mapParams && match.params) {
      for (const [key, value] of Object.entries(match.route.mapParams)) {
        if (match.params[key]) {
          match.params[value] = match.params[key];
          delete match.params[key];
        }
      }
    }

    return match;
  }

  protected createParts(path: string): string[] {
    let pathname = path.split("?")[0].replaceAll("//", "/");

    // remove trailing slash
    if (pathname.endsWith("/") && pathname.length > 1) {
      pathname = pathname.slice(0, -1);
    }

    return pathname.split("/").slice(1);
  }
}

export interface RouteMatch<T extends Route> {
  route?: T;
  params?: Record<string, string>;
}

export interface Route {
  path: string;

  /**
   * Rename a param in the route.
   * This is automatically filled when you have scenarios like:
   * `/customers/:id` and `/customers/:userId/payments`
   *
   * In this case, `:id` will be renamed to `:userId` in the second route.
   */
  mapParams?: Record<string, string>;
}

export interface Tree<T extends Route> {
  route?: T;
  children: {
    [key: string]: Tree<T>;
  };
  param?: {
    route?: T;
    name: string;
    children: {
      [key: string]: Tree<T>;
    };
  };
  wildcard?: {
    route: T;
  };
}