import "sqlite" for Database
import "io" for File

// This class provides a hook back into the C host to terminate the application.
foreign class Host {
  foreign static signalDone()
}

// All database operations are asynchronous. We chain them together using
// callbacks to ensure they execute in the correct order.
var mainFiber = Fiber.new {
  var db = Database.new()
  var dbPath = "test.db"
  var isDone = false // Flag to keep the fiber alive.

  // Clean up database file from previous runs, if it exists.
  if (File.exists(dbPath)) {
    File.delete(dbPath)
  }

  System.print("--- Starting SQLite CRUD Example ---")

  // 1. Open the database connection.
  db.open(dbPath) { |err|
    if (err) {
      System.print("Error opening database: %(err)")
      isDone = true // Signal completion on error.
      return
    }
    System.print("Database opened successfully at '%(dbPath)'.")

    // 2. CREATE: Create a new table.
    var createSql = "CREATE TABLE users (id INTEGER PRIMARY KEY, name TEXT, email TEXT);"
    db.exec(createSql) { |err|
      if (err) {
        System.print("Error creating table: %(err)")
        isDone = true
        return
      }
      System.print("Table 'users' created.")

      // 3. CREATE: Insert a new user.
      var insertSql = "INSERT INTO users (name, email) VALUES ('Alice', 'alice@example.com');"
      db.exec(insertSql) { |err|
        if (err) {
          System.print("Error inserting user: %(err)")
          isDone = true
          return
        }
        System.print("Inserted user 'Alice'.")

        // 4. READ: Query all users.
        db.query("SELECT * FROM users;") { |err, rows|
          if (err) {
            System.print("Error querying users: %(err)")
            isDone = true
            return
          }
          System.print("\n--- Current Users (after insert): ---")
          for (row in rows) {
            System.print("  ID: %(row["id"]), Name: %(row["name"]), Email: %(row["email"])")
          }

          // 5. UPDATE: Change Alice's email.
          var updateSql = "UPDATE users SET email = 'alice.smith@example.com' WHERE name = 'Alice';"
          db.exec(updateSql) { |err|
            if (err) {
              System.print("Error updating user: %(err)")
              isDone = true
              return
            }
            System.print("\nUpdated Alice's email.")

            // 6. READ: Query again to see the update.
            db.query("SELECT * FROM users;") { |err, rows|
              if (err) {
                System.print("Error querying users: %(err)")
                isDone = true
                return
              }
              System.print("\n--- Current Users (after update): ---")
              for (row in rows) {
                System.print("  ID: %(row["id"]), Name: %(row["name"]), Email: %(row["email"])")
              }

              // 7. DELETE: Remove Alice from the database.
              var deleteSql = "DELETE FROM users WHERE name = 'Alice';"
              db.exec(deleteSql) { |err|
                if (err) {
                  System.print("Error deleting user: %(err)")
                  isDone = true
                  return
                }
                System.print("\nDeleted Alice.")

                // 8. READ: Query one last time to confirm deletion.
                db.query("SELECT * FROM users;") { |err, rows|
                  if (err) {
                    System.print("Error querying users: %(err)")
                    isDone = true
                    return
                  }
                  System.print("\n--- Current Users (after delete): ---")
                  if (rows.isEmpty) {
                    System.print("  (No users found)")
                  } else {
                    for (row in rows) {
                      System.print("  ID: %(row["id"]), Name: %(row["name"]), Email: %(row["email"])")
                    }
                  }

                  // 9. Close the database connection.
                  db.close() { |err|
                    if (err) {
                      System.print("Error closing database: %(err)")
                    } else {
                      System.print("\nDatabase closed successfully.")
                    }
                    System.print("\n--- SQLite CRUD Example Finished ---")
                    isDone = true // This is the final step, signal completion.
                  }
                }
              }
            }
          }
        }
      }
    }
  }

  // Keep the fiber alive by yielding until the 'isDone' flag is set.
  while (!isDone) {
    Fiber.yield()
  }

  // All asynchronous operations are complete, now we can safely exit.
  Host.signalDone()
}