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//! Helper library for writing Cargo credential providers.
//!
//! A credential process should have a `struct` that implements the `Credential` trait.
//! The `main` function should be called with an instance of that struct, such as:
//!
//! ```rust,ignore
//! fn main() {
//!     cargo_credential::main(MyCredential);
//! }
//! ```
//!
//! While in the `perform` function, stdin and stdout will be re-attached to the
//! active console. This allows credential providers to be interactive if necessary.
//!
//! ## Error handling
//! ### [`Error::UrlNotSupported`]
//! A credential provider may only support some registry URLs. If this is the case
//! and an unsupported index URL is passed to the provider, it should respond with
//! [`Error::UrlNotSupported`]. Other credential providers may be attempted by Cargo.
//!
//! ### [`Error::NotFound`]
//! When attempting an [`Action::Get`] or [`Action::Logout`], if a credential can not
//! be found, the provider should respond with [`Error::NotFound`]. Other credential
//! providers may be attempted by Cargo.
//!
//! ### [`Error::OperationNotSupported`]
//! A credential provider might not support all operations. For example if the provider
//! only supports [`Action::Get`], [`Error::OperationNotSupported`] should be returned
//! for all other requests.
//!
//! ### [`Error::Other`]
//! All other errors go here. The error will be shown to the user in Cargo, including
//! the full error chain using [`std::error::Error::source`].
//!
//! ## Example
//! ```rust,ignore
#![doc = include_str!("../examples/file-provider.rs")]
//! ```

use serde::{Deserialize, Serialize};
use std::{fmt::Display, io};
use time::OffsetDateTime;

mod error;
mod secret;
mod stdio;

pub use error::Error;
pub use secret::Secret;
use stdio::stdin_stdout_to_console;

/// Message sent by the credential helper on startup
#[derive(Serialize, Deserialize, Clone, Debug)]
pub struct CredentialHello {
    // Protocol versions supported by the credential process.
    pub v: Vec<u32>,
}

/// Credential provider that doesn't support any registries.
pub struct UnsupportedCredential;
impl Credential for UnsupportedCredential {
    fn perform(
        &self,
        _registry: &RegistryInfo,
        _action: &Action,
        _args: &[&str],
    ) -> Result<CredentialResponse, Error> {
        Err(Error::UrlNotSupported)
    }
}

/// Message sent by Cargo to the credential helper after the hello
#[derive(Serialize, Deserialize, Clone, Debug)]
#[serde(rename_all = "kebab-case")]
pub struct CredentialRequest<'a> {
    // Cargo will respond with the highest common protocol supported by both.
    pub v: u32,
    #[serde(borrow)]
    pub registry: RegistryInfo<'a>,
    #[serde(borrow, flatten)]
    pub action: Action<'a>,
    /// Additional command-line arguments passed to the credential provider.
    pub args: Vec<&'a str>,
}

#[derive(Serialize, Deserialize, Clone, Debug)]
#[serde(rename_all = "kebab-case")]
pub struct RegistryInfo<'a> {
    /// Registry index url
    pub index_url: &'a str,
    /// Name of the registry in configuration. May not be available.
    /// The crates.io registry will be `crates-io` (`CRATES_IO_REGISTRY`).
    pub name: Option<&'a str>,
    /// Headers from attempting to access a registry that resulted in a HTTP 401.
    #[serde(skip_serializing_if = "Vec::is_empty", default)]
    pub headers: Vec<String>,
}

#[derive(Serialize, Deserialize, Clone, Debug)]
#[non_exhaustive]
#[serde(tag = "kind", rename_all = "kebab-case")]
pub enum Action<'a> {
    #[serde(borrow)]
    Get(Operation<'a>),
    Login(LoginOptions<'a>),
    Logout,
    #[serde(other)]
    Unknown,
}

impl<'a> Display for Action<'a> {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            Action::Get(_) => f.write_str("get"),
            Action::Login(_) => f.write_str("login"),
            Action::Logout => f.write_str("logout"),
            Action::Unknown => f.write_str("<unknown>"),
        }
    }
}

#[derive(Serialize, Deserialize, Clone, Debug)]
#[serde(rename_all = "kebab-case")]
pub struct LoginOptions<'a> {
    /// Token passed on the command line via --token or from stdin
    pub token: Option<Secret<&'a str>>,
    /// Optional URL that the user can visit to log in to the registry
    pub login_url: Option<&'a str>,
}

/// A record of what kind of operation is happening that we should generate a token for.
#[derive(Serialize, Deserialize, Clone, Debug)]
#[non_exhaustive]
#[serde(tag = "operation", rename_all = "kebab-case")]
pub enum Operation<'a> {
    /// The user is attempting to fetch a crate.
    Read,
    /// The user is attempting to publish a crate.
    Publish {
        /// The name of the crate
        name: &'a str,
        /// The version of the crate
        vers: &'a str,
        /// The checksum of the crate file being uploaded
        cksum: &'a str,
    },
    /// The user is attempting to yank a crate.
    Yank {
        /// The name of the crate
        name: &'a str,
        /// The version of the crate
        vers: &'a str,
    },
    /// The user is attempting to unyank a crate.
    Unyank {
        /// The name of the crate
        name: &'a str,
        /// The version of the crate
        vers: &'a str,
    },
    /// The user is attempting to modify the owners of a crate.
    Owners {
        /// The name of the crate
        name: &'a str,
    },
    #[serde(other)]
    Unknown,
}

/// Message sent by the credential helper
#[derive(Serialize, Deserialize, Clone, Debug)]
#[serde(tag = "kind", rename_all = "kebab-case")]
#[non_exhaustive]
pub enum CredentialResponse {
    Get {
        token: Secret<String>,
        cache: CacheControl,
        operation_independent: bool,
    },
    Login,
    Logout,
    #[serde(other)]
    Unknown,
}

#[derive(Serialize, Deserialize, Clone, Debug)]
#[serde(rename_all = "kebab-case")]
#[non_exhaustive]
pub enum CacheControl {
    /// Do not cache this result.
    Never,
    /// Cache this result and use it for subsequent requests in the current Cargo invocation until the specified time.
    Expires(#[serde(with = "time::serde::timestamp")] OffsetDateTime),
    /// Cache this result and use it for all subsequent requests in the current Cargo invocation.
    Session,
    #[serde(other)]
    Unknown,
}

/// Credential process JSON protocol version. Incrementing
/// this version will prevent new credential providers
/// from working with older versions of Cargo.
pub const PROTOCOL_VERSION_1: u32 = 1;
pub trait Credential {
    /// Retrieves a token for the given registry.
    fn perform(
        &self,
        registry: &RegistryInfo,
        action: &Action,
        args: &[&str],
    ) -> Result<CredentialResponse, Error>;
}

/// Runs the credential interaction
pub fn main(credential: impl Credential) {
    let result = doit(credential).map_err(|e| Error::Other(e));
    if result.is_err() {
        serde_json::to_writer(std::io::stdout(), &result)
            .expect("failed to serialize credential provider error");
        println!();
    }
}

fn doit(
    credential: impl Credential,
) -> Result<(), Box<dyn std::error::Error + Send + Sync + 'static>> {
    let hello = CredentialHello {
        v: vec![PROTOCOL_VERSION_1],
    };
    serde_json::to_writer(std::io::stdout(), &hello)?;
    println!();

    loop {
        let mut buffer = String::new();
        let len = std::io::stdin().read_line(&mut buffer)?;
        if len == 0 {
            return Ok(());
        }
        let request: CredentialRequest = serde_json::from_str(&buffer)?;
        if request.v != PROTOCOL_VERSION_1 {
            return Err(format!("unsupported protocol version {}", request.v).into());
        }

        let response = stdin_stdout_to_console(|| {
            credential.perform(&request.registry, &request.action, &request.args)
        })?;

        serde_json::to_writer(std::io::stdout(), &response)?;
        println!();
    }
}

/// Read a line of text from stdin.
pub fn read_line() -> Result<String, io::Error> {
    let mut buf = String::new();
    io::stdin().read_line(&mut buf)?;
    Ok(buf.trim().to_string())
}

/// Prompt the user for a token.
pub fn read_token(
    login_options: &LoginOptions,
    registry: &RegistryInfo,
) -> Result<Secret<String>, Error> {
    if let Some(token) = &login_options.token {
        return Ok(token.to_owned());
    }

    if let Some(url) = login_options.login_url {
        eprintln!("please paste the token found on {url} below");
    } else if let Some(name) = registry.name {
        eprintln!("please paste the token for {name} below");
    } else {
        eprintln!("please paste the token for {} below", registry.index_url);
    }

    Ok(Secret::from(read_line().map_err(Box::new)?))
}