/**
 * @file
 * @copyright 2020, Valentin Anger
 * @license ISC
 */

import { BufReader } from "https://deno.land/std@0.69.0/io/bufio.ts";

import IrcError from "./error.ts";
import Message from "./message.ts";
import { Replies } from "./replies.ts";

export interface ClientOptions {
  nickname: string;
  hostname: string;
  port?: number;
  use_tls?: boolean;
  join_channels?: string[];
  nickserv_password?: string;
}

export class Client {
  readonly nickname: string;
  readonly hostname: string;
  readonly port: number;
  readonly use_tls: boolean;
  readonly join_channels: string[];
  readonly nickserv_password?: string;

  private conn?: Deno.Conn;
  private buf_reader?: BufReader;
  private encoder = new TextEncoder();

  private message_buffer: Message[] = [];

  /** Creates a new IRC Client
      The default port is encrypted_port.
      TLS is used by default.
  */
  constructor(options: ClientOptions) {
    this.nickname = options.nickname;
    this.hostname = options.hostname;
    this.port = options.port ?? Client.encrypted_port;
    this.use_tls = options.use_tls ?? true;
    this.join_channels = options.join_channels ?? [];
    this.nickserv_password = options.nickserv_password;
  }

  async connect(): Promise<void> {
    const connectFun = this.use_tls ? Deno.connectTls : Deno.connect;
    const connection = await connectFun({
      hostname: this.hostname,
      port: this.port,
    });
    this.conn = connection;
    this.buf_reader = new BufReader(connection, 512);

    await this.sendMessage("NICK", [this.nickname]);
    await this.sendMessage("USER", [this.nickname, "0", "*", "DenoIrc"]);

    this.queueMessage(await this.getReply(Replies.RPL_WELCOME));

    if (this.nickserv_password != undefined) {
      this.nickserv(this.nickserv_password);
    }

    this.queueMessage(await this.getReply(Replies.RPL_ENDOFMOTD));

    for (const channel of this.join_channels) {
      await this.joinChannel(channel, true);
    }
  }

  connected(): boolean {
    return this.conn != undefined;
  }

  async disconnect(quit_message: string = ""): Promise<void> {
    if (this.conn != undefined) {
      await this.sendMessage("QUIT", [quit_message]);
    }

    await this.getReply("ERROR");

    this.drop();
  }

  drop(): void {
    if (this.conn != undefined) {
      this.conn.close();
      this.conn = undefined;
    }

    this.buf_reader = undefined;
  }

  async nickserv(password: string): Promise<void> {
    return await this.sendPrivmsg("NickServ", `IDENTIFY ${password}`);
  }

  /** Constructs and sends a message as defined in RFC2812
      Sections: 2.3
  */
  async sendMessage(command: string, parameters: string[]): Promise<void> {
    if (this.conn == undefined) {
      throw new IrcError("Client is not connected");
    }

    let message = command;

    let remaining = parameters.length;
    for (const param of parameters) {
      remaining -= 1;

      // TODO Check parameter for validity
      if (remaining > 0 || !message.match(/:| /)) {
        // BNF middle
        message += " " + param;
      } else {
        // BNF trailing
        message += " :" + param;
      }
    }

    // TODO Substitute all invalid chars with placeholders

    message += "\r\n";

    const encoded = this.encoder.encode(message);
    if (encoded.length > 512) {
      throw new IrcError("Resulting message is too long");
    }

    await this.conn.write(encoded).then((b) => {
      if (b != encoded.length) {
        throw new IrcError("Transmission failed");
      }
    });
  }

  /** Reads the next IRC message */
  async readMessage(): Promise<Message> {
    if (this.message_buffer.length > 0) {
      return this.message_buffer.shift() as Message;
    }

    return this.readMessageStream();
  }

  private async readMessageStream() {
    if (this.buf_reader == undefined) {
      throw new IrcError("Client is not connected");
    }

    const message = await this.buf_reader.readString("\n");

    if (message === null) {
      return Promise.reject(null);
    }

    return new Message(this, message);
  }

  private queueMessage(message: Message): void {
    this.message_buffer.push(message);
  }

  private async getReply(...replies: string[]): Promise<Message> {
    while (true) {
      const message = await this.readMessageStream();

      if (replies.includes(message.command)) {
        return message;
      } else if (message.command[0] == "4") {
        throw new IrcError("Received error code", message.command);
      } else {
        if (message.command == "PING") {
          // Keep connection alive
          await this.sendMessage("PONG", message.parameters);
        } else {
          this.queueMessage(message);
        }
      }
    }
  }

  async sendPrivmsg(target: string, message: string): Promise<void> {
    await this.sendMessage("PRIVMSG", [target, message]);
  }

  async sendNotice(target: string, message: string): Promise<void> {
    await this.sendMessage("NOTICE", [target, message]);
  }

  async joinChannel(
    name: string,
    keep_message: boolean = false,
  ): Promise<void> {
    await this.sendMessage("JOIN", [name]);
    while (true) {
      const join = await this.getReply("JOIN");

      if (join.parameters[0] == name) {
        if (keep_message) {
          this.queueMessage(join);
        }

        break;
      }

      this.queueMessage(join);
    }
  }

  async leaveChannel(name: string, part_message?: string): Promise<void> {
    let parameters = [name];
    if (part_message != undefined) {
      parameters.push(part_message);
    }

    await this.sendMessage("PART", parameters);
  }

  /** Generates a stream of incomming messages
      Pings and CTCP version requests are handled internally.
  */
  messages(): AsyncIterable<Message> {
    const client = this;

    return {
      async *[Symbol.asyncIterator](): AsyncIterator<Message> {
        while (true) {
          let message;
          try {
            message = await client.readMessage();
          } catch {
            return;
          }

          if (message.command[0] == "4") {
            throw new IrcError("Recieved error code", message.command);
          }

          switch (message.command) {
            case "ERROR":
              client.drop();
              yield message;
              return;
            case "PING":
              await client.sendMessage("PONG", message.parameters);
              break;
            case "PRIVMSG":
              // Respond to CTCP version requests
              if (
                message.sender != undefined &&
                message.parameters[1] == "\u{1}VERSION\u{1}"
              ) {
                await client.sendPrivmsg(
                  message.sender.nickname,
                  "\u{1}VERSION\u{1} " +
                    Client.client_name +
                    ":" +
                    Client.client_version +
                    ":" +
                    Client.client_environment,
                );
                break;
              }
            default:
              yield message;
          }
        }
      },
    };
  }
}

export namespace Client {
  export const unencrypted_port = 6667;
  export const encrypted_port = 6697;

  export const client_name = "DenoIrc";
  export const client_version = "0.1.0";
  export const client_environment = "undefined";
}