import crypto from 'node:crypto';
import fs from 'node:fs/promises';
import path from 'node:path';

import { defaultGameSaveName } from '../../shared/gameSave/buildSnapshot';
import { GAME_SAVE_SCHEMA_VERSION, type GameSaveBody, type GameSaveFile, type GameSaveListItem } from '../../shared/types/gameSave';

function safeSegment(raw: string): string {
  const cleaned = raw.replace(/[^a-zA-Z0-9_-]/g, '');
  if (!cleaned || cleaned === '.' || cleaned === '..') throw new Error('GAME_SAVE_BAD_ID');
  return cleaned;
}

export class GameSavesStore {
  private readonly rootDir: string;

  constructor(userData: string) {
    this.rootDir = path.join(userData, 'game-saves');
  }

  async list(projectId: string): Promise<GameSaveListItem[]> {
    const dir = this.projectDir(projectId);
    let names: string[] = [];
    try {
      names = await fs.readdir(dir);
    } catch {
      return [];
    }
    const items: GameSaveListItem[] = [];
    for (const name of names) {
      if (!name.endsWith('.json')) continue;
      try {
        const file = await this.readFile(path.join(dir, name));
        if (file.projectId !== projectId) continue;
        items.push({ id: file.id, name: file.name, savedAt: file.savedAt });
      } catch {
        continue;
      }
    }
    items.sort((a, b) => (a.savedAt < b.savedAt ? 1 : a.savedAt > b.savedAt ? -1 : 0));
    return items;
  }

  async read(projectId: string, id: string): Promise<GameSaveFile> {
    const filePath = this.filePath(projectId, id);
    try {
      const file = await this.readFile(filePath);
      if (file.projectId !== projectId || file.id !== id) throw new Error('GAME_SAVE_NOT_FOUND');
      return file;
    } catch (err) {
      if (err instanceof Error && err.message.startsWith('GAME_SAVE_')) throw err;
      throw new Error('GAME_SAVE_NOT_FOUND');
    }
  }

  async write(projectId: string, body: GameSaveBody, opts: { id: string | null; name: string }): Promise<GameSaveListItem> {
    if (body.projectId !== projectId) throw new Error('GAME_SAVE_PROJECT_MISMATCH');
    const id = opts.id ? safeSegment(opts.id) : `gs_${crypto.randomBytes(8).toString('hex')}`;
    const name = opts.name.trim() || defaultGameSaveName();
    const savedAt = new Date().toISOString();
    const file: GameSaveFile = { ...body, id, name, savedAt, schemaVersion: GAME_SAVE_SCHEMA_VERSION };
    const filePath = this.filePath(projectId, id);
    await fs.mkdir(path.dirname(filePath), { recursive: true });
    await fs.writeFile(filePath, JSON.stringify(file), 'utf8');
    return { id, name, savedAt };
  }

  private projectDir(projectId: string): string {
    return path.join(this.rootDir, safeSegment(projectId));
  }

  private filePath(projectId: string, id: string): string {
    return path.join(this.projectDir(projectId), `${safeSegment(id)}.json`);
  }

  private async readFile(filePath: string): Promise<GameSaveFile> {
    const raw = await fs.readFile(filePath, 'utf8');
    const parsed = JSON.parse(raw) as GameSaveFile;
    if (!parsed || parsed.schemaVersion !== GAME_SAVE_SCHEMA_VERSION || typeof parsed.id !== 'string') {
      throw new Error('GAME_SAVE_NOT_FOUND');
    }
    return parsed;
  }
}