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//! Kubernetes configuration objects from `~/.kube/config`, `$KUBECONFIG`, or the [cluster environment](https://kubernetes.io/docs/tasks/access-application-cluster/access-cluster/#accessing-the-api-from-a-pod).
//!
//! # Usage
//! The [`Config`] has several constructors plus logic to infer environment.
//!
//! Unless you have issues, prefer using [`Config::infer`], and pass it to a [`Client`][crate::Client].
use std::{path::PathBuf, time::Duration};

use thiserror::Error;

mod file_config;
mod file_loader;
mod incluster_config;

use file_loader::ConfigLoader;
pub use file_loader::KubeConfigOptions;
pub use incluster_config::Error as InClusterError;

/// Failed to infer config
#[derive(Error, Debug)]
#[error("failed to infer config: in-cluster: ({in_cluster}), kubeconfig: ({kubeconfig})")]
pub struct InferConfigError {
    in_cluster: InClusterError,
    // We can only pick one source, but the kubeconfig failure is more likely to be a user error
    #[source]
    kubeconfig: KubeconfigError,
}

/// Possible errors when loading kubeconfig
#[derive(Error, Debug)]
pub enum KubeconfigError {
    /// Failed to determine current context
    #[error("failed to determine current context")]
    CurrentContextNotSet,

    /// Kubeconfigs with mismatching kind cannot be merged
    #[error("kubeconfigs with mismatching kind cannot be merged")]
    KindMismatch,

    /// Kubeconfigs with mismatching api version cannot be merged
    #[error("kubeconfigs with mismatching api version cannot be merged")]
    ApiVersionMismatch,

    /// Failed to load current context
    #[error("failed to load current context: {0}")]
    LoadContext(String),

    /// Failed to load the cluster of context
    #[error("failed to load the cluster of context: {0}")]
    LoadClusterOfContext(String),

    /// Failed to find named user
    #[error("failed to find named user: {0}")]
    FindUser(String),

    /// Failed to find the path of kubeconfig
    #[error("failed to find the path of kubeconfig")]
    FindPath,

    /// Failed to read kubeconfig
    #[error("failed to read kubeconfig from '{1:?}': {0}")]
    ReadConfig(#[source] std::io::Error, PathBuf),

    /// Failed to parse kubeconfig YAML
    #[error("failed to parse kubeconfig YAML: {0}")]
    Parse(#[source] serde_yaml::Error),

    /// The structure of the parsed kubeconfig is invalid
    #[error("the structure of the parsed kubeconfig is invalid: {0}")]
    InvalidStructure(#[source] serde_yaml::Error),

    /// Cluster url is missing on selected cluster
    #[error("cluster url is missing on selected cluster")]
    MissingClusterUrl,

    /// Failed to parse cluster url
    #[error("failed to parse cluster url: {0}")]
    ParseClusterUrl(#[source] http::uri::InvalidUri),

    /// Failed to parse proxy url
    #[error("failed to parse proxy url: {0}")]
    ParseProxyUrl(#[source] http::uri::InvalidUri),

    /// Failed to load certificate authority
    #[error("failed to load certificate authority")]
    LoadCertificateAuthority(#[source] LoadDataError),

    /// Failed to load client certificate
    #[error("failed to load client certificate")]
    LoadClientCertificate(#[source] LoadDataError),

    /// Failed to load client key
    #[error("failed to load client key")]
    LoadClientKey(#[source] LoadDataError),

    /// Failed to parse PEM-encoded certificates
    #[error("failed to parse PEM-encoded certificates: {0}")]
    ParseCertificates(#[source] pem::PemError),
}

/// Errors from loading data from a base64 string or a file
#[derive(Debug, Error)]
pub enum LoadDataError {
    /// Failed to decode base64 data
    #[error("failed to decode base64 data: {0}")]
    DecodeBase64(#[source] base64::DecodeError),

    /// Failed to read file
    #[error("failed to read file '{1:?}': {0}")]
    ReadFile(#[source] std::io::Error, PathBuf),

    /// No base64 data or file path was provided
    #[error("no base64 data or file")]
    NoBase64DataOrFile,
}

/// Configuration object detailing things like cluster URL, default namespace, root certificates, and timeouts.
///
/// # Usage
/// Construct a [`Config`] instance by using one of the many constructors.
///
/// Prefer [`Config::infer`] unless you have particular issues, and avoid manually managing
/// the data in this struct unless you have particular needs. It exists to be consumed by the [`Client`][crate::Client].
///
/// If you are looking to parse the kubeconfig found in a user's home directory see [`Kubeconfig`](crate::config::Kubeconfig).
#[cfg_attr(docsrs, doc(cfg(feature = "config")))]
#[derive(Debug, Clone)]
pub struct Config {
    /// The configured cluster url
    pub cluster_url: http::Uri,
    /// The configured default namespace
    pub default_namespace: String,
    /// The configured root certificate
    pub root_cert: Option<Vec<Vec<u8>>>,
    /// Set the timeout for connecting to the Kubernetes API.
    ///
    /// A value of `None` means no timeout
    pub connect_timeout: Option<std::time::Duration>,
    /// Set the timeout for the Kubernetes API response.
    ///
    /// A value of `None` means no timeout
    pub read_timeout: Option<std::time::Duration>,
    /// Set the timeout for the Kubernetes API request.
    ///
    /// A value of `None` means no timeout
    pub write_timeout: Option<std::time::Duration>,
    /// Whether to accept invalid certificates
    pub accept_invalid_certs: bool,
    /// Stores information to tell the cluster who you are.
    pub auth_info: AuthInfo,
    // TODO Actually support proxy or create an example with custom client
    /// Optional proxy URL.
    pub proxy_url: Option<http::Uri>,
    /// If set, apiserver certificate will be validated to contain this string
    ///
    /// If not set, the `cluster_url` is used instead
    pub tls_server_name: Option<String>,
}

impl Config {
    /// Construct a new config where only the `cluster_url` is set by the user.
    /// and everything else receives a default value.
    ///
    /// Most likely you want to use [`Config::infer`] to infer the config from
    /// the environment.
    pub fn new(cluster_url: http::Uri) -> Self {
        Self {
            cluster_url,
            default_namespace: String::from("default"),
            root_cert: None,
            connect_timeout: Some(DEFAULT_CONNECT_TIMEOUT),
            read_timeout: Some(DEFAULT_READ_TIMEOUT),
            write_timeout: None,
            accept_invalid_certs: false,
            auth_info: AuthInfo::default(),
            proxy_url: None,
            tls_server_name: None,
        }
    }

    /// Infer a Kubernetes client configuration.
    ///
    /// First, a user's kubeconfig is loaded from `KUBECONFIG` or
    /// `~/.kube/config`. If that fails, an in-cluster config is loaded via
    /// [`Config::incluster`]. If inference from both sources fails, then an
    /// error is returned.
    ///
    /// [`Config::apply_debug_overrides`] is used to augment the loaded
    /// configuration based on the environment.
    pub async fn infer() -> Result<Self, InferConfigError> {
        let mut config = match Self::from_kubeconfig(&KubeConfigOptions::default()).await {
            Err(kubeconfig_err) => {
                tracing::trace!(
                    error = &kubeconfig_err as &dyn std::error::Error,
                    "no local config found, falling back to local in-cluster config"
                );

                Self::incluster().map_err(|in_cluster| InferConfigError {
                    in_cluster,
                    kubeconfig: kubeconfig_err,
                })?
            }
            Ok(success) => success,
        };
        config.apply_debug_overrides();
        Ok(config)
    }

    /// Load an in-cluster Kubernetes client configuration using
    /// [`Config::incluster_env`].
    pub fn incluster() -> Result<Self, InClusterError> {
        Self::incluster_env()
    }

    /// Load an in-cluster config using the `KUBERNETES_SERVICE_HOST` and
    /// `KUBERNETES_SERVICE_PORT` environment variables.
    ///
    /// A service account's token must be available in
    /// `/var/run/secrets/kubernetes.io/serviceaccount/`.
    ///
    /// This method matches the behavior of the official Kubernetes client
    /// libraries and is the default for both TLS stacks.
    pub fn incluster_env() -> Result<Self, InClusterError> {
        let uri = incluster_config::try_kube_from_env()?;
        Self::incluster_with_uri(uri)
    }

    /// Load an in-cluster config using the API server at
    /// `https://kubernetes.default.svc`.
    ///
    /// A service account's token must be available in
    /// `/var/run/secrets/kubernetes.io/serviceaccount/`.
    ///
    /// This behavior does not match that of the official Kubernetes clients,
    /// but this approach is compatible with the `rustls-tls` feature
    /// without setting `tls_server_name`.
    /// See <https://github.com/kube-rs/kube/issues/1003>.
    pub fn incluster_dns() -> Result<Self, InClusterError> {
        Self::incluster_with_uri(incluster_config::kube_dns())
    }

    fn incluster_with_uri(cluster_url: http::uri::Uri) -> Result<Self, InClusterError> {
        let default_namespace = incluster_config::load_default_ns()?;
        let root_cert = incluster_config::load_cert()?;

        Ok(Self {
            cluster_url,
            default_namespace,
            root_cert: Some(root_cert),
            connect_timeout: Some(DEFAULT_CONNECT_TIMEOUT),
            read_timeout: Some(DEFAULT_READ_TIMEOUT),
            write_timeout: None,
            accept_invalid_certs: false,
            auth_info: AuthInfo {
                token_file: Some(incluster_config::token_file()),
                ..Default::default()
            },
            proxy_url: None,
            tls_server_name: None,
        })
    }

    /// Create configuration from the default local config file
    ///
    /// This will respect the `$KUBECONFIG` evar, but otherwise default to `~/.kube/config`.
    /// You can also customize what context/cluster/user you want to use here,
    /// but it will default to the current-context.
    pub async fn from_kubeconfig(options: &KubeConfigOptions) -> Result<Self, KubeconfigError> {
        let loader = ConfigLoader::new_from_options(options).await?;
        Self::new_from_loader(loader).await
    }

    /// Create configuration from a [`Kubeconfig`] struct
    ///
    /// This bypasses kube's normal config parsing to obtain custom functionality.
    pub async fn from_custom_kubeconfig(
        kubeconfig: Kubeconfig,
        options: &KubeConfigOptions,
    ) -> Result<Self, KubeconfigError> {
        let loader = ConfigLoader::new_from_kubeconfig(kubeconfig, options).await?;
        Self::new_from_loader(loader).await
    }

    async fn new_from_loader(loader: ConfigLoader) -> Result<Self, KubeconfigError> {
        let cluster_url = loader
            .cluster
            .server
            .clone()
            .ok_or(KubeconfigError::MissingClusterUrl)?
            .parse::<http::Uri>()
            .map_err(KubeconfigError::ParseClusterUrl)?;

        let default_namespace = loader
            .current_context
            .namespace
            .clone()
            .unwrap_or_else(|| String::from("default"));

        let accept_invalid_certs = loader.cluster.insecure_skip_tls_verify.unwrap_or(false);
        let mut root_cert = None;

        if let Some(ca_bundle) = loader.ca_bundle()? {
            root_cert = Some(ca_bundle);
        }

        Ok(Self {
            cluster_url,
            default_namespace,
            root_cert,
            connect_timeout: Some(DEFAULT_CONNECT_TIMEOUT),
            read_timeout: Some(DEFAULT_READ_TIMEOUT),
            write_timeout: None,
            accept_invalid_certs,
            proxy_url: loader.proxy_url()?,
            auth_info: loader.user,
            tls_server_name: loader.cluster.tls_server_name,
        })
    }

    /// Override configuration based on environment variables
    ///
    /// This is only intended for use as a debugging aid, and the specific variables and their behaviour
    /// should **not** be considered stable across releases.
    ///
    /// Currently, the following overrides are supported:
    ///
    /// - `KUBE_RS_DEBUG_IMPERSONATE_USER`: A Kubernetes user to impersonate, for example: `system:serviceaccount:default:foo` will impersonate the `ServiceAccount` `foo` in the `Namespace` `default`
    /// - `KUBE_RS_DEBUG_IMPERSONATE_GROUP`: A Kubernetes group to impersonate, multiple groups may be specified by separating them with commas
    /// - `KUBE_RS_DEBUG_OVERRIDE_URL`: A Kubernetes cluster URL to use rather than the one specified in the config, useful for proxying traffic through `kubectl proxy`
    pub fn apply_debug_overrides(&mut self) {
        // Log these overrides loudly, to emphasize that this is only a debugging aid, and should not be relied upon in production
        if let Ok(impersonate_user) = std::env::var("KUBE_RS_DEBUG_IMPERSONATE_USER") {
            tracing::warn!(?impersonate_user, "impersonating user");
            self.auth_info.impersonate = Some(impersonate_user);
        }
        if let Ok(impersonate_groups) = std::env::var("KUBE_RS_DEBUG_IMPERSONATE_GROUP") {
            let impersonate_groups = impersonate_groups.split(',').map(str::to_string).collect();
            tracing::warn!(?impersonate_groups, "impersonating groups");
            self.auth_info.impersonate_groups = Some(impersonate_groups);
        }
        if let Ok(url) = std::env::var("KUBE_RS_DEBUG_OVERRIDE_URL") {
            tracing::warn!(?url, "overriding cluster URL");
            match url.parse() {
                Ok(uri) => {
                    self.cluster_url = uri;
                }
                Err(err) => {
                    tracing::warn!(
                        ?url,
                        error = &err as &dyn std::error::Error,
                        "failed to parse override cluster URL, ignoring"
                    );
                }
            }
        }
    }

    /// Client certificate and private key in PEM.
    pub(crate) fn identity_pem(&self) -> Option<Vec<u8>> {
        self.auth_info.identity_pem().ok()
    }
}

fn certs(data: &[u8]) -> Result<Vec<Vec<u8>>, pem::PemError> {
    Ok(pem::parse_many(data)?
        .into_iter()
        .filter_map(|p| {
            if p.tag() == "CERTIFICATE" {
                Some(p.into_contents())
            } else {
                None
            }
        })
        .collect::<Vec<_>>())
}

// https://github.com/kube-rs/kube/issues/146#issuecomment-590924397
const DEFAULT_CONNECT_TIMEOUT: Duration = Duration::from_secs(30);
const DEFAULT_READ_TIMEOUT: Duration = Duration::from_secs(295);

// Expose raw config structs
pub use file_config::{
    AuthInfo, AuthProviderConfig, Cluster, Context, ExecConfig, ExecInteractiveMode, Kubeconfig,
    NamedAuthInfo, NamedCluster, NamedContext, NamedExtension, Preferences,
};

#[cfg(test)]
mod tests {
    #[cfg(not(feature = "client"))] // want to ensure this works without client features
    #[tokio::test]
    async fn config_loading_on_small_feature_set() {
        use super::Config;
        let cfgraw = r#"
        apiVersion: v1
        clusters:
        - cluster:
            certificate-authority-data: aGVsbG8K
            server: https://0.0.0.0:6443
          name: k3d-test
        contexts:
        - context:
            cluster: k3d-test
            user: admin@k3d-test
          name: k3d-test
        current-context: k3d-test
        kind: Config
        preferences: {}
        users:
        - name: admin@k3d-test
          user:
            client-certificate-data: aGVsbG8K
            client-key-data: aGVsbG8K
        "#;
        let file = tempfile::NamedTempFile::new().expect("create config tempfile");
        std::fs::write(file.path(), cfgraw).unwrap();
        std::env::set_var("KUBECONFIG", file.path());
        let kubeconfig = Config::infer().await.unwrap();
        assert_eq!(kubeconfig.cluster_url, "https://0.0.0.0:6443/");
    }
}