#![allow(non_camel_case_types)]

use std::ffi::{c_char, c_int, c_void};
use std::fmt;
use std::marker::{PhantomData, PhantomPinned};

/// A marker struct to make whatever it's in `!Sync`, `!Send`, and `!Unpin`.
#[derive(Default, PartialOrd, PartialEq, Ord, Eq)]
#[repr(C)]
struct ExtremelyUnsafe {
    _value: (),
    _marker: PhantomData<(PhantomPinned, *mut c_void)>,
}

impl fmt::Debug for ExtremelyUnsafe {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.write_str("ExtremelyUnsafe")
    }
}

/// An opaque structure that PAM uses to communicate.
///
/// This is only ever returned in pointer form and cannot be constructed.
#[repr(C)]
pub struct pam_handle(ExtremelyUnsafe);

impl fmt::Debug for pam_handle {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "PamHandle({self:p}")
    }
}

/// An opaque structure that is passed through PAM in a conversation.
#[repr(C)]
pub struct AppData(ExtremelyUnsafe);

impl fmt::Debug for AppData {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "AppData({self:p}")
    }
}

/// Just an alias for the type of [`pam_conv::conv`].
///
/// For important details about the format of `messages`,
/// see the [`helpers`](crate::helpers) module.
///
/// ```no_run
/// # use libpam_sys::{ConversationCallback, pam_conv};
/// fn convo() -> ConversationCallback {
///     // ...
/// #    unimplemented!()
/// }
/// let conv = pam_conv{conv: convo(), appdata_ptr: std::ptr::null_mut()};
/// ```
pub type ConversationCallback = unsafe extern "C" fn(
    num_msg: c_int,
    msg: *const *const pam_message,
    resp: *mut *mut pam_response,
    appdata: *mut AppData,
) -> c_int;

/// Alias for the callback to [`pam_set_data`](crate::pam_set_data).
///
/// ```no_run
/// # use std::ffi::CString;
/// use libpam_sys::{CleanupCallback, pam_set_data};
/// # use libpam_sys::pam_handle;
/// # let handle: *mut pam_handle = std::ptr::null_mut();
/// # let mut my_data = 100;
/// # let data_ptr = &mut my_data as *mut i32;
/// fn cleanup() -> CleanupCallback {
///     // ...
/// #    unimplemented!()
/// }
/// let name = CString::new("name").unwrap();
/// unsafe {
///     pam_set_data(handle, name.as_ptr().cast_mut(), data_ptr.cast(), cleanup());
/// }
/// ```
pub type CleanupCallback = unsafe extern "C" fn(
    pamh: *mut pam_handle,
    data: *mut c_void,
    pam_end_status: c_int,
);

/// Used by PAM to communicate between the module and the application.
#[repr(C)]
pub struct pam_conv {
    pub conv: unsafe extern "C" fn(
        num_msg: c_int,
        msg: *const *const pam_message,
        resp: *mut *mut pam_response,
        appdata: *mut AppData,
    ) -> c_int,
    pub appdata_ptr: *mut AppData,
}

/// A message sent into a PAM conversation.
#[repr(C)]
pub struct pam_message {
    pub msg_style: c_int,
    pub msg: *const c_char,
}

/// A response returned from a PAM conversation.
#[repr(C)]
pub struct pam_response {
    pub resp: *mut c_char,
    /// Completely unused.
    pub resp_retcode: c_int,
}


// These are the functions specified in X/SSO. Everybody exports them.
extern "C" {
    /// Account validation.
    pub fn pam_acct_mgmt(pamh: *mut pam_handle, flags: c_int) -> c_int;

    /// Authenticate a user.
    pub fn pam_authenticate(pamh: *mut pam_handle, flags: c_int) -> c_int;

    // Nobody implements pam_authenticate_secondary.

    /// Manage authentication tokens.
    pub fn pam_chauthtok(pamh: *mut pam_handle, flags: c_int) -> c_int;

    /// Close an opened user session.
    pub fn pam_close_session(pamh: *mut pam_handle, flags: c_int) -> c_int;

    /// Ends the PAM transaction.
    pub fn pam_end(pamh: *mut pam_handle, flags: c_int) -> c_int;

    /// Gets module-specific data. PAM still owns the data.
    pub fn pam_get_data(
        pamh: *mut pam_handle,
        module_data_name: *const c_char,
        data: *mut *const c_void,
    ) -> c_int;

    /// Gets an environment variable.  You own the return value.
    pub fn pam_getenv(pamh: *mut pam_handle, name: *const c_char) -> *mut c_char;

    /// Gets all the environment variables.  You own everything it points to.
    pub fn pam_getenvlist(pamh: *mut pam_handle) -> *mut *mut c_char;

    /// Get information about the transaction.
    ///
    /// The item is owned by PAM.
    pub fn pam_get_item(
        pamh: *mut pam_handle,
        item_type: c_int,
        item: *mut *const c_void,
    ) -> c_int;

    // Nobody implements pam_get_mapped_authtok.
    // Nobody implements pam_get_mapped_username.

    /// Get the username. PAM owns it.
    pub fn pam_get_user(
        pamh: *mut pam_handle,
        user: *mut *const c_char,
        prompt: *const c_char,
    ) -> c_int;

    /// Opens a user session.
    pub fn pam_open_session(pamh: *mut pam_handle, flags: c_int) -> c_int;

    /// Sets the value of an environment variable. `namevalue` is copied.
    pub fn pam_putenv(pamh: *mut pam_handle, namevalue: *const c_char) -> c_int;

    /// Update or delete user credentials.
    pub fn pam_setcred(pamh: *mut pam_handle, flags: c_int) -> c_int;

    /// Set module-specific data. PAM will call `cleanup` when completed.
    pub fn pam_set_data(
        pamh: *mut pam_handle,
        module_data_name: *const c_char,
        data: *mut c_void,
        cleanup: unsafe extern "C" fn(
            pamh: *mut pam_handle,
            data: *mut c_void,
            pam_end_status: c_int,
        ),
    ) -> c_int;

    /// Set information about the transaction.  The `item` is copied.
    pub fn pam_set_item(pamh: *mut pam_handle, item_type: c_int, item: *const c_void) -> c_int;

    // Nobody implements pam_set_mapped_authtok.
    // Nobody implements pam_set_mapped_username.

    // The pam_sm_whatever functions are prototypes for the functions that
    // a PAM module should implement, not symbols provided by PAM.

    // Nobody implements pam_authenticate_secondary.

    /// Starts a PAM transaction.  The `conv` may or may not be copied.
    pub fn pam_start(
        service: *const c_char,
        user: *const c_char,
        pam_conv: *mut pam_conv,
        pamh: *mut *mut pam_handle,
    ) -> c_int;

    /// Gets a statically-allocated error string.
    ///
    /// All implementations of PAM known to this library (Linux-PAM, OpenPAM,
    /// and Sun) ignore `pamh` and will accept a null pointer.
    pub fn pam_strerror(pamh: *const pam_handle, error_number: c_int) -> *mut c_char;
}

// We use `_private_pam_impl_hack` because ctest loses its mind
// when it comes across the `cfg_pam_impl` macro.
// This is a custom cfg variable set in our build.rs. Don't do this; just use
// cfg_pam_impl.
#[cfg(_private_pam_impl_hack = "LinuxPam")]
extern "C" {
    pub fn pam_get_authtok(pamh: *mut pam_handle, x: c_int, token: *mut *const c_char, prompt: *const c_char) -> c_int;
}


// int (*)(struct pam_handle *, char *, void *, void (*)(struct pam_handle *, void *, int))
// int (*)(struct pam_handle *, char *, void *, int (*)(struct pam_handle *, void *, int))