export type HistorySearchDirection = "backward" | "forward";

/** Deterministic prompt-history state kept separate from Pi editor internals. */
export class PiHistoryAdapter {
  readonly #entries: string[] = [];
  #index = -1;
  #draft = "";
  #query: string | undefined;
  #searchIndex = -1;
  #ignoreCase = false;

  get entries(): readonly string[] {
    return [...this.#entries];
  }

  setSearchIgnoreCase(enabled: boolean): void {
    this.#ignoreCase = enabled;
  }

  add(text: string): void {
    const value = text.trim();
    if (value.length === 0 || this.#entries[0] === value) return;
    this.#entries.unshift(value);
    if (this.#entries.length > 100) this.#entries.pop();
  }

  previous(current: string): string | undefined {
    if (this.#entries.length === 0 || this.#index + 1 >= this.#entries.length)
      return undefined;
    if (this.#index === -1) this.#draft = current;
    this.#index += 1;
    return this.#entries[this.#index];
  }

  next(): string | undefined {
    if (this.#index < 0) return undefined;
    this.#index -= 1;
    return this.#index < 0 ? this.#draft : this.#entries[this.#index];
  }

  fetchOldest(): string | undefined {
    if (this.#entries.length === 0) return undefined;
    this.#index = this.#entries.length - 1;
    return this.#entries[this.#index];
  }

  search(query: string, direction: HistorySearchDirection): string | undefined {
    this.#query = query;
    this.#searchIndex = direction === "backward" ? -1 : this.#entries.length;
    return this.repeatSearch(direction);
  }

  repeatSearch(direction: HistorySearchDirection): string | undefined {
    if (this.#query === undefined) return undefined;
    const step = direction === "backward" ? 1 : -1;
    for (
      let index = this.#searchIndex + step;
      index >= 0 && index < this.#entries.length;
      index += step
    ) {
      const entry = this.#entries[index];
      const query = this.#query;
      const matches =
        entry !== undefined &&
        (this.#ignoreCase
          ? entry.toLocaleLowerCase().includes(query.toLocaleLowerCase())
          : entry.includes(query));
      if (matches) {
        this.#searchIndex = index;
        return this.#entries[index];
      }
    }
    return undefined;
  }

  resetNavigation(): void {
    this.#index = -1;
    this.#draft = "";
  }
}