const fs = require("fs");
const path = require("path");
const Database = require("better-sqlite3");
const { DATA_DIR, DB_PATH } = require("./config");

const SQLITE_EXTENSIONS = new Set([".sqlite", ".sqlite3", ".db"]);
const REQUIRED_SCHEMA_TABLES = ["packages", "regions"];

function isSqliteFile(fileName) {
  const extension = path.extname(fileName).toLowerCase();
  return SQLITE_EXTENSIONS.has(extension);
}

function listExistingSqliteFiles(directoryPath) {
  if (!fs.existsSync(directoryPath)) {
    return [];
  }

  return fs
    .readdirSync(directoryPath, { withFileTypes: true })
    .filter((entry) => entry.isFile() && isSqliteFile(entry.name))
    .map((entry) => path.resolve(directoryPath, entry.name))
    .sort((left, right) => left.localeCompare(right));
}

function hasApplicationSchema(filePath) {
  let db;

  try {
    db = new Database(filePath, { readonly: true, fileMustExist: true });

    return REQUIRED_SCHEMA_TABLES.every((tableName) =>
      db.prepare("SELECT 1 FROM sqlite_master WHERE type = 'table' AND name = ?").get(tableName)
    );
  } catch {
    return false;
  } finally {
    if (db) {
      db.close();
    }
  }
}

function resolveRuntimeDbPath() {
  const configuredPath = path.resolve(DB_PATH);
  const configuredFileName = path.basename(configuredPath).toLowerCase();
  const existingDatabases = listExistingSqliteFiles(DATA_DIR);

  if (!existingDatabases.length) {
    return configuredPath;
  }

  const schemaDatabases = existingDatabases.filter(hasApplicationSchema);
  const preferredDatabases = schemaDatabases.length ? schemaDatabases : existingDatabases;
  const configuredMatch = preferredDatabases.find(
    (filePath) => path.basename(filePath).toLowerCase() === configuredFileName
  );

  return configuredMatch || preferredDatabases[0];
}

function ensureDataDirectory() {
  fs.mkdirSync(DATA_DIR, { recursive: true });
}

function openDatabase() {
  ensureDataDirectory();
  const runtimeDbPath = resolveRuntimeDbPath();

  const db = new Database(runtimeDbPath);
  db.pragma("journal_mode = WAL");
  db.pragma("foreign_keys = ON");

  return db;
}

module.exports = {
  DB_PATH,
  hasApplicationSchema,
  listExistingSqliteFiles,
  openDatabase,
  resolveRuntimeDbPath,
};