use ruff_diagnostics::{Diagnostic, Violation};
use ruff_macros::{derive_message_formats, violation};
use ruff_python_ast::Stmt;
use ruff_text_size::Ranged;

use crate::checkers::ast::Checker;

/// ## What it does
/// Checks for `import` statements outside of a module's top-level scope, such
/// as within a function or class definition.
///
/// ## Why is this bad?
/// [PEP 8] recommends placing imports not only at the top-level of a module,
/// but at the very top of the file, "just after any module comments and
/// docstrings, and before module globals and constants."
///
/// `import` statements have effects that are global in scope; defining them at
/// the top level has a number of benefits. For example, it makes it easier to
/// identify the dependencies of a module, and ensures that any invalid imports
/// are caught regardless of whether a specific function is called or class is
/// instantiated.
///
/// An import statement would typically be placed within a function only to
/// avoid a circular dependency, to defer a costly module load, or to avoid
/// loading a dependency altogether in a certain runtime environment.
///
/// ## Example
/// ```python
/// def print_python_version():
///     import platform
///
///     print(python.python_version())
/// ```
///
/// Use instead:
/// ```python
/// import platform
///
///
/// def print_python_version():
///     print(python.python_version())
/// ```
///
/// [PEP 8]: https://peps.python.org/pep-0008/#imports
#[violation]
pub struct ImportOutsideTopLevel;

impl Violation for ImportOutsideTopLevel {
    #[derive_message_formats]
    fn message(&self) -> String {
        "`import` should be at the top-level of a file".to_string()
    }
}

/// C0415
pub(crate) fn import_outside_top_level(checker: &mut Checker, stmt: &Stmt) {
    if !checker.semantic().current_scope().kind.is_module() {
        checker
            .diagnostics
            .push(Diagnostic::new(ImportOutsideTopLevel, stmt.range()));
    }
}
