/*
 * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
 * SPDX-License-Identifier: Apache-2.0
 */

use aws_smithy_types::date_time::Format;
use std::fmt;
use std::fmt::{Debug, Formatter};
use std::sync::Arc;
use std::time::{SystemTime, UNIX_EPOCH};
use zeroize::Zeroizing;

use aws_smithy_runtime_api::client::identity::Identity;

use crate::attributes::AccountId;

/// AWS SDK Credentials
///
/// An opaque struct representing credentials that may be used in an AWS SDK, modeled on
/// the [CRT credentials implementation](https://github.com/awslabs/aws-c-auth/blob/main/source/credentials.c).
///
/// When `Credentials` is dropped, its contents are zeroed in memory. Credentials uses an interior Arc to ensure
/// that even when cloned, credentials don't exist in multiple memory locations.
#[derive(Clone, Eq, PartialEq)]
pub struct Credentials(Arc<Inner>);

#[derive(Clone, Eq, PartialEq)]
struct Inner {
    access_key_id: Zeroizing<String>,
    secret_access_key: Zeroizing<String>,
    session_token: Zeroizing<Option<String>>,

    /// Credential Expiry
    ///
    /// A SystemTime at which the credentials should no longer be used because they have expired.
    /// The primary purpose of this value is to allow credentials to communicate to the caching
    /// provider when they need to be refreshed.
    ///
    /// If these credentials never expire, this value will be set to `None`
    expires_after: Option<SystemTime>,

    // Optional piece of data to support account-based endpoints.
    // https://docs.aws.amazon.com/sdkref/latest/guide/feature-account-endpoints.html
    account_id: Option<AccountId>,

    provider_name: &'static str,
}

impl Debug for Credentials {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        let mut creds = f.debug_struct("Credentials");
        creds
            .field("provider_name", &self.0.provider_name)
            .field("access_key_id", &self.0.access_key_id.as_str())
            .field("secret_access_key", &"** redacted **");
        if let Some(expiry) = self.expiry() {
            if let Some(formatted) = expiry.duration_since(UNIX_EPOCH).ok().and_then(|dur| {
                aws_smithy_types::DateTime::from_secs(dur.as_secs() as _)
                    .fmt(Format::DateTime)
                    .ok()
            }) {
                creds.field("expires_after", &formatted);
            } else {
                creds.field("expires_after", &expiry);
            }
        } else {
            creds.field("expires_after", &"never");
        }
        if let Some(account_id) = &self.0.account_id {
            creds.field("account_id", &account_id.as_str());
        }
        creds.finish()
    }
}

#[cfg(feature = "hardcoded-credentials")]
const STATIC_CREDENTIALS: &str = "Static";

impl Credentials {
    /// Returns builder for `Credentials`.
    pub fn builder() -> CredentialsBuilder {
        CredentialsBuilder::default()
    }

    /// Creates `Credentials`.
    ///
    /// This is intended to be used from a custom credentials provider implementation.
    /// It is __NOT__ secure to hardcode credentials into your application.
    pub fn new(
        access_key_id: impl Into<String>,
        secret_access_key: impl Into<String>,
        session_token: Option<String>,
        expires_after: Option<SystemTime>,
        provider_name: &'static str,
    ) -> Self {
        Credentials(Arc::new(Inner {
            access_key_id: Zeroizing::new(access_key_id.into()),
            secret_access_key: Zeroizing::new(secret_access_key.into()),
            session_token: Zeroizing::new(session_token),
            expires_after,
            account_id: None,
            provider_name,
        }))
    }

    /// Creates `Credentials` from hardcoded access key, secret key, and session token.
    ///
    /// _Note: In general, you should prefer to use the credential providers that come
    /// with the AWS SDK to get credentials. It is __NOT__ secure to hardcode credentials
    /// into your application. If you're writing a custom credentials provider, then
    /// use [`Credentials::new`] instead of this._
    ///
    /// This function requires the `hardcoded-credentials` feature to be enabled.
    ///
    /// [`Credentials`] implement
    /// [`ProvideCredentials`](crate::provider::ProvideCredentials) directly, so no custom provider
    /// implementation is required when wiring these up to a client:
    /// ```rust
    /// use aws_credential_types::Credentials;
    /// # mod service {
    /// #     use aws_credential_types::provider::ProvideCredentials;
    /// #     pub struct Config;
    /// #     impl Config {
    /// #        pub fn builder() -> Self {
    /// #            Config
    /// #        }
    /// #        pub fn credentials_provider(self, provider: impl ProvideCredentials + 'static) -> Self {
    /// #            self
    /// #        }
    /// #        pub fn build(self) -> Config { Config }
    /// #     }
    /// #     pub struct Client;
    /// #     impl Client {
    /// #        pub fn from_conf(config: Config) -> Self {
    /// #            Client
    /// #        }
    /// #     }
    /// # }
    /// # use service::{Config, Client};
    ///
    /// let creds = Credentials::from_keys("akid", "secret_key", None);
    /// let config = Config::builder()
    ///     .credentials_provider(creds)
    ///     .build();
    /// let client = Client::from_conf(config);
    /// ```
    #[cfg(feature = "hardcoded-credentials")]
    pub fn from_keys(
        access_key_id: impl Into<String>,
        secret_access_key: impl Into<String>,
        session_token: Option<String>,
    ) -> Self {
        Self::new(
            access_key_id,
            secret_access_key,
            session_token,
            None,
            STATIC_CREDENTIALS,
        )
    }

    /// Returns the access key ID.
    pub fn access_key_id(&self) -> &str {
        &self.0.access_key_id
    }

    /// Returns the secret access key.
    pub fn secret_access_key(&self) -> &str {
        &self.0.secret_access_key
    }

    /// Returns the time when the credentials will expire.
    pub fn expiry(&self) -> Option<SystemTime> {
        self.0.expires_after
    }

    /// Returns a mutable reference to the time when the credentials will expire.
    pub fn expiry_mut(&mut self) -> &mut Option<SystemTime> {
        &mut Arc::make_mut(&mut self.0).expires_after
    }

    /// Returns the account ID.
    pub fn account_id(&self) -> Option<&AccountId> {
        self.0.account_id.as_ref()
    }

    /// Returns the session token.
    pub fn session_token(&self) -> Option<&str> {
        self.0.session_token.as_deref()
    }
}

/// Builder for [`Credentials`]
///
/// Similar to [`Credentials::new`], the use of the builder is intended for a custom credentials provider implementation.
/// It is __NOT__ secure to hardcode credentials into your application.
#[derive(Default, Clone)]
#[allow(missing_debug_implementations)] // for security reasons, and we can add manual `impl Debug` just like `Credentials`, if needed.
pub struct CredentialsBuilder {
    access_key_id: Option<Zeroizing<String>>,
    secret_access_key: Option<Zeroizing<String>>,
    session_token: Zeroizing<Option<String>>,
    expires_after: Option<SystemTime>,
    account_id: Option<AccountId>,
    provider_name: Option<&'static str>,
}

impl CredentialsBuilder {
    /// Set access key id for the builder.
    pub fn access_key_id(mut self, access_key_id: impl Into<String>) -> Self {
        self.access_key_id = Some(Zeroizing::new(access_key_id.into()));
        self
    }

    /// Set secret access key for the builder.
    pub fn secret_access_key(mut self, secret_access_key: impl Into<String>) -> Self {
        self.secret_access_key = Some(Zeroizing::new(secret_access_key.into()));
        self
    }

    /// Set session token for the builder.
    pub fn session_token(mut self, session_token: impl Into<String>) -> Self {
        self.set_session_token(Some(session_token.into()));
        self
    }

    /// Set session token for the builder.
    pub fn set_session_token(&mut self, session_token: Option<String>) {
        self.session_token = Zeroizing::new(session_token);
    }

    /// Set expiry for the builder.
    pub fn expiry(mut self, expiry: SystemTime) -> Self {
        self.set_expiry(Some(expiry));
        self
    }

    /// Set expiry for the builder.
    pub fn set_expiry(&mut self, expiry: Option<SystemTime>) {
        self.expires_after = expiry;
    }

    /// Set account ID for the builder.
    pub fn account_id(mut self, account_id: impl Into<AccountId>) -> Self {
        self.set_account_id(Some(account_id.into()));
        self
    }

    /// Set account ID for the builder.
    pub fn set_account_id(&mut self, account_id: Option<AccountId>) {
        self.account_id = account_id;
    }

    /// Set provicer name for the builder.
    pub fn provider_name(mut self, provider_name: &'static str) -> Self {
        self.provider_name = Some(provider_name);
        self
    }

    /// Build [`Credentials`] from the builder.
    pub fn build(self) -> Credentials {
        Credentials(Arc::new(Inner {
            access_key_id: self
                .access_key_id
                .expect("required field `access_key_id` missing"),
            secret_access_key: self
                .secret_access_key
                .expect("required field `secret_access_key` missing"),
            session_token: self.session_token,
            expires_after: self.expires_after,
            account_id: self.account_id,
            provider_name: self
                .provider_name
                .expect("required field `provider_name` missing"),
        }))
    }
}

#[cfg(feature = "test-util")]
impl Credentials {
    /// Creates a test `Credentials` with no session token.
    pub fn for_tests() -> Self {
        Self::new(
            "ANOTREAL",
            "notrealrnrELgWzOk3IfjzDKtFBhDby",
            None,
            None,
            "test",
        )
    }

    /// Creates a test `Credentials` that include a session token.
    pub fn for_tests_with_session_token() -> Self {
        Self::new(
            "ANOTREAL",
            "notrealrnrELgWzOk3IfjzDKtFBhDby",
            Some("notarealsessiontoken".to_string()),
            None,
            "test",
        )
    }
}

#[cfg(feature = "test-util")]
impl CredentialsBuilder {
    /// Creates a test `CredentialsBuilder` with the required fields:
    /// `access_key_id`, `secret_access_key`, and `provider_name`.
    pub fn for_tests() -> Self {
        CredentialsBuilder::default()
            .access_key_id("ANOTREAL")
            .secret_access_key("notrealrnrELgWzOk3IfjzDKtFBhDby")
            .provider_name("test")
    }
}

impl From<Credentials> for Identity {
    fn from(val: Credentials) -> Self {
        let expiry = val.expiry();
        let mut builder = if let Some(account_id) = val.account_id() {
            Identity::builder().property(account_id.clone()).data(val)
        } else {
            Identity::builder().data(val)
        };
        builder.set_expiration(expiry);
        builder.build().expect("set required fields")
    }
}

#[cfg(test)]
mod test {
    use crate::Credentials;
    use std::time::{Duration, UNIX_EPOCH};

    #[test]
    fn debug_impl() {
        let creds = Credentials::new(
            "akid",
            "secret",
            Some("token".into()),
            Some(UNIX_EPOCH + Duration::from_secs(1234567890)),
            "debug tester",
        );
        assert_eq!(
            format!("{:?}", creds),
            r#"Credentials { provider_name: "debug tester", access_key_id: "akid", secret_access_key: "** redacted **", expires_after: "2009-02-13T23:31:30Z" }"#
        );

        // with account ID
        let creds = Credentials::builder()
            .access_key_id("akid")
            .secret_access_key("secret")
            .session_token("token")
            .expiry(UNIX_EPOCH + Duration::from_secs(1234567890))
            .account_id("012345678901")
            .provider_name("debug tester")
            .build();
        assert_eq!(
            format!("{:?}", creds),
            r#"Credentials { provider_name: "debug tester", access_key_id: "akid", secret_access_key: "** redacted **", expires_after: "2009-02-13T23:31:30Z", account_id: "012345678901" }"#
        );
    }
}