//! All values that can be sent to and returned from Keyforkd.
//!
//! All Error values are stored as enum unit values.

use keyfork_derive_util::request::{DerivationRequest, DerivationResponse};

use serde::{Deserialize, Serialize};

/// A request made to Keyforkd.
#[derive(Serialize, Deserialize, Clone, Debug)]
pub enum Request {
    /// A derivation request.
    Derivation(DerivationRequest),

    /// A derivation request, with a TTY provided for pinentry if necessary.
    DerivationWithTTY(DerivationRequest, String),
}

impl From<DerivationRequest> for Request {
    fn from(value: DerivationRequest) -> Self {
        Self::Derivation(value)
    }
}

impl From<(DerivationRequest, String)> for Request {
    fn from((request, tty): (DerivationRequest, String)) -> Self {
        Self::DerivationWithTTY(request, tty)
    }
}

/// Any error that could occur while deriving a key with Keyforkd.
#[derive(thiserror::Error, Clone, Debug, Serialize, Deserialize)]
pub enum DerivationError {
    /// The TTY used for pinentry or passphrase entry was invalid.
    #[error("The provided TTY was not valid")]
    InvalidTTY,

    /// No TTY was required for pinentry, but was not provided.
    #[error("A TTY was required by the pinentry program but was not provided")]
    NoTTY,

    /// The derivation length was invalid, must be at least 2 indexes long.
    #[error("Invalid derivation length: Expected at least 2, actual: {0}")]
    InvalidDerivationLength(usize),

    /// An error occurred while deriving data.
    #[error("Derivation error: {0}")]
    Derivation(String),
}

/// An error that could occur while interacting with Keyforkd.
#[derive(thiserror::Error, Clone, Debug, Serialize, Deserialize)]
pub enum Error {
    /// An error occurred while processing a derivation request.
    #[error(transparent)]
    Derivation(#[from] DerivationError),
}

/// Any response from a Keyforkd request.
///
/// Responses can be converted to their inner values without matching the Response type by
/// using a type annotation and [`TryInto::try_into`].
#[derive(Serialize, Deserialize, Clone, Debug)]
#[non_exhaustive]
pub enum Response {
    /// A derivation response.
    ///
    /// From:
    /// * [`Request::Derivation`]
    /// * [`Request::DerivationWithTTY`]
    Derivation(DerivationResponse),
}

/// Attempting to convert from a [`DerivationResponse`] to a [`Response`]
#[derive(thiserror::Error, Debug)]
#[error("Unable to downcast to {0}")]
pub struct Downcast(&'static str);

use std::any::type_name;

impl TryFrom<Response> for DerivationResponse {
    type Error = Downcast;

    fn try_from(value: Response) -> Result<Self, Self::Error> {
        #[allow(irrefutable_let_patterns)]
        if let Response::Derivation(response) = value {
            Ok(response)
        } else {
            Err(Downcast(type_name::<Self>()))
        }
    }
}