import { PackedMap } from "../util/PackedMap.ts";
import { JISEncodeMap } from "./JISEncodeMap.ts";
import {
  type Charset,
  type CharsetDecoderOptions,
  type CharsetEncodeOptions,
  type CharsetEncoder,
  type CharsetEncoderOptions,
  StandardDecoder,
} from "./charset.ts";

class Windows31jCharset implements Charset {
  get name() {
    return "windows-31j";
  }

  createDecoder(options?: CharsetDecoderOptions) {
    return new StandardDecoder("windows-31j");
  }

  createEncoder(options?: CharsetEncoderOptions) {
    return new Windows31jEncoder(options);
  }

  isUnicode() {
    return false;
  }

  isEbcdic() {
    return false;
  }
}

const Windows31jEncodeMap = new PackedMap((m) => {
  const decoder = new TextDecoder("windows-31j");

  // Shift-JIS additional mapping
  m.set(0xa5, 0x5c);
  m.set(0xab, 0x81e1);
  m.set(0xaf, 0x8150);
  m.set(0xb5, 0x83ca);
  m.set(0xb7, 0x8145);
  m.set(0xb8, 0x8143);
  m.set(0xbb, 0x81e2);
  m.set(0x203e, 0x7e);
  m.set(0x2212, 0x817c);
  m.set(0x3094, 0x8394);
  const buf = new Uint8Array(2);
  for (const hba of [
    [0xfa, 0xfc],
    [0xed, 0xee],
  ]) {
    for (let hb = hba[0]; hb <= hba[1]; hb++) {
      buf[0] = hb;
      for (const lba of [
        [0x40, 0x7e],
        [0x80, 0xfc],
      ]) {
        for (let lb = lba[0]; lb <= lba[1]; lb++) {
          buf[1] = lb;

          const decoded = decoder.decode(buf);
          if (decoded !== "\uFFFD") {
            m.set(decoded.charCodeAt(0), (hb << 8) | lb);
          }
        }
      }
    }
  }
});

class Windows31jEncoder implements CharsetEncoder {
  private fatal;

  constructor(options?: CharsetEncoderOptions) {
    this.fatal = options?.fatal ?? true;

    JISEncodeMap.initialize();
    Windows31jEncodeMap.initialize();
  }

  canEncode(str: string) {
    for (let i = 0; i < str.length; i++) {
      const cp = str.charCodeAt(i);
      if (cp <= 0x7f) {
        // ASCII
        // no handle
      } else if (cp >= 0xe000 && cp <= 0xe757) {
        // ユーザー外字
        // no handle
      } else if (cp >= 0xff61 && cp <= 0xff9f) {
        // 半角カナ
        // no handle
      } else {
        let enc = JISEncodeMap.get(cp);
        if (enc != null) {
          // no handle
        } else if ((enc = Windows31jEncodeMap.get(cp)) != null) {
          // no handle
        } else {
          return false;
        }
      }
    }
    return true;
  }

  encode(str: string, options?: CharsetEncodeOptions): Uint8Array {
    const out = new Array<number>();
    const limit = options?.limit ?? Number.POSITIVE_INFINITY;
    let prev = 0;
    for (let i = 0; i < str.length; i++) {
      prev = out.length;
      const cp = str.charCodeAt(i);
      if (cp <= 0x7f) {
        // ASCII
        out.push(cp);
      } else if (cp >= 0xe000 && cp <= 0xe757) {
        // ユーザー外字
        const sjis =
          cp >= 0xe6db
            ? cp - 0xe6db + 0xf980
            : cp >= 0xe69c
              ? cp - 0xe69c + 0xf940
              : cp >= 0xe61f
                ? cp - 0xe61f + 0xf880
                : cp >= 0xe5e0
                  ? cp - 0xe5e0 + 0xf840
                  : cp >= 0xe563
                    ? cp - 0xe563 + 0xf780
                    : cp >= 0xe524
                      ? cp - 0xe524 + 0xf740
                      : cp >= 0xe4a7
                        ? cp - 0xe4a7 + 0xf680
                        : cp >= 0xe468
                          ? cp - 0xe468 + 0xf640
                          : cp >= 0xe3eb
                            ? cp - 0xe3eb + 0xf580
                            : cp >= 0xe3ac
                              ? cp - 0xe3ac + 0xf540
                              : cp >= 0xe32f
                                ? cp - 0xe32f + 0xf480
                                : cp >= 0xe2f0
                                  ? cp - 0xe2f0 + 0xf440
                                  : cp >= 0xe273
                                    ? cp - 0xe273 + 0xf380
                                    : cp >= 0xe234
                                      ? cp - 0xe234 + 0xf340
                                      : cp >= 0xe1b7
                                        ? cp - 0xe1b7 + 0xf280
                                        : cp >= 0xe178
                                          ? cp - 0xe178 + 0xf240
                                          : cp >= 0xe0fb
                                            ? cp - 0xe0fb + 0xf180
                                            : cp >= 0xe0bc
                                              ? cp - 0xe0bc + 0xf140
                                              : cp >= 0xe03f
                                                ? cp - 0xe03f + 0xf080
                                                : cp - 0xe000 + 0xf040;
        out.push((sjis >>> 8) & 0xff);
        out.push(sjis & 0xff);
      } else if (cp >= 0xff61 && cp <= 0xff9f) {
        // 半角カナ
        out.push(cp - 0xff61 + 0xa1);
      } else {
        let enc = JISEncodeMap.get(cp);
        if (enc != null) {
          let hb = (enc >>> 8) & 0xff;
          let lb = enc & 0xff;
          lb += hb & 1 ? (lb < 0x60 ? 0x1f : 0x20) : 0x7e;
          hb = hb < 0x5f ? (hb + 0xe1) >>> 1 : (hb + 0x161) >>> 1;
          out.push(hb);
          out.push(lb);
        } else if ((enc = Windows31jEncodeMap.get(cp)) != null) {
          if (enc > 0xff) {
            out.push((enc >>> 8) & 0xff);
            out.push(enc & 0xff);
          } else {
            out.push(enc & 0xff);
          }
        } else if (this.fatal) {
          throw TypeError(
            `The code point ${cp.toString(16)} could not be encoded`,
          );
        } else {
          out.push(0x5f); // ?
        }
      }

      if (out.length > limit) {
        out.length = prev;
        break;
      }
    }

    return Uint8Array.from(out);
  }
}

export const windows31j = new Windows31jCharset();