import { Buffer } from "./util/index";

export class JSONEncoder {
  private _isFirstKey: i32[];
  private result: string[];

  constructor() {
    this._isFirstKey = new Array<i32>(10);
    this.result = new Array<string>();
    this._isFirstKey.push(1);
  }

  get isFirstKey(): bool {
    return <bool>this._isFirstKey[this._isFirstKey.length - 1];
  }

  serialize(): Uint8Array {
    // TODO: Write directly to UTF8 bytes
    return Buffer.fromString(this.toString());
  }

  toString(): string {
    return this.result.join("");
  }

  setString(name: string | null, value: string): void {
    this.writeKey(name);
    this.writeString(value);
  }

  setBoolean(name: string | null, value: bool): void {
    this.writeKey(name);
    this.writeBoolean(value);
  }

  setNull(name: string | null): void {
    this.writeKey(name);
    this.write("null");
  }

  setInteger(name: string | null, value: i64): void {
    this.writeKey(name);
    this.writeInteger(value);
  }

  setFloat(name: string | null, value: f64): void {
    this.writeKey(name);
    this.writeFloat(value);
  }

  pushArray(name: string | null): bool {
    this.writeKey(name);
    this.write("[");
    this._isFirstKey.push(1);
    return true;
  }

  popArray(): void {
    this.write("]");
    this._isFirstKey.pop();
  }

  pushObject(name: string | null): bool {
    this.writeKey(name);
    this.write("{");
    this._isFirstKey.push(1);
    return true;
  }

  popObject(): void {
    this.write("}");
    this._isFirstKey.pop();
  }

  private writeKey(str: string | null): void {
    if (!this.isFirstKey) {
      this.write(",");
    } else {
      this._isFirstKey[this._isFirstKey.length - 1] = 0;
    }
    if (str != null && (<string>str).length > 0) {
      this.writeString(str!);
      this.write(":");
    }
  }

  private writeString(str: string): void {
    this.write('"');
    let savedIndex = 0;
    for (let i = 0; i < str.length; i++) {
      let char = str.charCodeAt(i);
      let needsEscaping =
        char < 0x20 || char == '"'.charCodeAt(0) || char == "\\".charCodeAt(0);
      if (needsEscaping) {
        this.write(str.substring(savedIndex, i));
        savedIndex = i + 1;
        if (char == '"'.charCodeAt(0)) {
          this.write('\\"');
        } else if (char == "\\".charCodeAt(0)) {
          this.write("\\\\");
        } else if (char == "\b".charCodeAt(0)) {
          this.write("\\b");
        } else if (char == "\n".charCodeAt(0)) {
          this.write("\\n");
        } else if (char == "\r".charCodeAt(0)) {
          this.write("\\r");
        } else if (char == "\t".charCodeAt(0)) {
          this.write("\\t");
        } else {
          // TODO: Implement encoding for other contol characters
          // @ts-ignore integer does have toString
          assert(
            false,
            "Unsupported control character code: " + char.toString()
          );
        }
      }
    }
    this.write(str.substring(savedIndex, str.length));
    this.write('"');
  }

  private writeBoolean(value: bool): void {
    this.write(value ? "true" : "false");
  }

  private writeInteger(value: i64): void {
    this.write(value.toString());
  }

  private writeFloat(value: f64): void {
    this.write(value.toString());
  }

  private write(str: string): void {
    this.result.push(str);
  }
}