import type { FileHandle } from "node:fs/promises";
import type { Writable } from "node:stream";
import type { Charset, CharsetEncoder } from "./charset/charset.ts";
import { utf8 } from "./charset/utf8.ts";

export class CsvWriter {
  private writer: Promise<WritableStreamDefaultWriter<Uint8Array>>;
  private encoder: CharsetEncoder;

  private bom: boolean;
  private fieldSeparator: string;
  private lineSeparator: string;
  private quoteAll: boolean;

  private index = 0;

  constructor(
    dest: WritableStream<Uint8Array> | FileHandle | Writable,
    options?: {
      charset?: Charset;
      bom?: boolean;
      fieldSeparator?: string;
      lineSeparator?: string;
      quoteAll?: boolean;
      fatal?: boolean;
    },
  ) {
    const charset = options?.charset ?? utf8;
    this.fieldSeparator = options?.fieldSeparator ?? ",";
    this.lineSeparator = options?.lineSeparator ?? "\r\n";
    this.quoteAll = options?.quoteAll ?? false;
    this.bom = charset.isUnicode() ? (options?.bom ?? true) : false;
    this.encoder = charset.createEncoder({
      fatal: options?.fatal ?? true,
    });

    let stream: Promise<WritableStream<Uint8Array>>;
    if (dest instanceof WritableStream) {
      stream = Promise.resolve(dest);
    } else {
      const writable =
        "createWriteStream" in dest ? dest.createWriteStream() : dest;
      if (
        "constructor" in writable &&
        "toWeb" in writable.constructor &&
        typeof writable.constructor.toWeb === "function"
      ) {
        stream = Promise.resolve(writable.constructor.toWeb(writable));
      } else {
        throw new TypeError(`Unsuppoted destination: ${dest}`);
      }
    }

    this.writer = stream.then((value) => value.getWriter());
  }

  async write(
    record: unknown[],
    options?: {
      quoteAll?: boolean;
    },
  ) {
    const quoteAll = options?.quoteAll ?? this.quoteAll;

    let str = "";
    if (this.bom) {
      str = "\uFEFF";
      this.bom = false;
    }

    for (let i = 0; i < record.length; i++) {
      const item = `${record[i] ?? ""}`;
      if (i > 0) {
        str += this.fieldSeparator;
      }
      if (
        quoteAll ||
        item.includes(this.fieldSeparator) ||
        /[\r\n]/.test(item)
      ) {
        str += `"${item.replaceAll('"', '""')}"`;
      } else {
        str += item;
      }
    }
    str += this.lineSeparator;

    this.index++;
    const writer = await this.writer;
    await writer.write(this.encoder.encode(str));
  }

  get count() {
    return this.index;
  }

  async close() {
    const writer = await this.writer;
    if (this.bom) {
      await writer.write(this.encoder.encode("\uFEFF"));
      this.bom = false;
    }
    await writer.close();
  }
}