// Copyright 2020 Palantir Technologies, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//! An HTTP client for use with [Conjure] servers.
//!
//! This crate provides both asynchronous and blocking clients. The clients can either be used in Conjure-generated
//! wrapper types or standalone for use with non-Conjure servers.
//!
//! # Configuration
//!
//! While a `conjure_runtime` client's configuration can be built up programmatically, the more common approach is for
//! the configuration to be deserialized from a service's runtime-reloadable configuration file. The `ServicesConfig`
//! supports configuration for multiple downstream services, as well as allowing for both global and per-service
//! configuration overrides:
//!
//! ```yaml
//! services:
//!   auth-service:
//!     uris:
//!       - https://auth.my-network.com/auth-service
//!   cache-service:
//!     uris:
//!       - https://cache-1.my-network.com/cache-service
//!       - https://cache-2.my-network.com/cache-service
//!     request-timeout: 10s
//! # options set at this level will apply as defaults to all configured services
//! security:
//!   ca-file: var/security/ca.pem
//! ```
//!
//! Once a client is constructed, its configuration can be dynamically reloaded by calling `RefreshHandle::refresh`
//! on a handle obtained via `Client::refresh_handle`. Note that the refresh process will throw away the client's
//! TLS session cache and HTTP connection pool, so it should not be called needlessly often.
//!
//! # Usage
//!
//! First construct a raw `conjure_runtime::Client`:
//!
//! ```
//! use conjure_runtime::{UserAgent, Agent, HostMetricsRegistry, Client};
//! use conjure_runtime::config::{ServiceConfig, SecurityConfig};
//! use std::path::PathBuf;
//! use std::sync::Arc;
//! use witchcraft_metrics::MetricRegistry;
//!
//! # fn foo() -> Result<(), conjure_error::Error> {
//! let user_agent = UserAgent::new(Agent::new("my-user-agent", "1.0.0"));
//! let host_metrics = Arc::new(HostMetricsRegistry::new());
//! let metrics = Arc::new(MetricRegistry::new());
//! let config = ServiceConfig::builder()
//!     .uris(vec!["https://url-to-server:1234/test-service".parse().unwrap()])
//!     .security(
//!         SecurityConfig::builder()
//!             .ca_file(Some(PathBuf::from("path/to/ca_file.pem")))
//!             .build(),
//!     )
//!     .build();
//!
//! let client = Client::new(
//!     "test-service",
//!     user_agent,
//!     &host_metrics,
//!     &metrics,
//!     &config,
//! )?;
//! # Ok(()) }
//! ```
//!
//! The client can then be used with Conjure-generated service interfaces:
//!
//! ```
//! use conjure_codegen::example_types::another::TestServiceAsyncClient;
//! use conjure_object::BearerToken;
//!
//! # async fn foo(client: conjure_runtime::Client) -> Result<(), conjure_error::Error> {
//! let client = TestServiceAsyncClient::new(client);
//!
//! let auth = BearerToken::new("my_auth_token").unwrap();
//! let file_systems = client.get_file_systems(&auth).await?;
//! # Ok(()) }
//! ```
//!
//! Or manually if a service does not provide a Conjure API:
//!
//! ```
//! # async fn foo(client: conjure_runtime::Client) -> Result<(), conjure_error::Error> {
//! let response = client.delete("/widgets/{widgetId}")
//!     .param("widgetId", 12345)
//!     .send()
//!     .await?;
//! # Ok(()) }
//! ```
//!
//! The `blocking::Client`'s API is identical, with the exception that you don't `.await` on methods:
//!
//! ```
//! use conjure_codegen::example_types::another::TestServiceClient;
//! use conjure_object::BearerToken;
//!
//! # fn foo(client: conjure_runtime::blocking::Client) -> Result<(), conjure_error::Error> {
//! let client = TestServiceClient::new(client);
//!
//! let auth = BearerToken::new("my_auth_token").unwrap();
//! let file_systems = client.get_file_systems(&auth)?;
//! # Ok(()) }
//! ```
//!
//! ```
//! # fn foo(client: conjure_runtime::blocking::Client) -> Result<(), conjure_error::Error> {
//! let response = client.delete("/widgets/{widgetId}")
//!     .param("widgetId", 12345)
//!     .send()?;
//! # Ok(()) }
//! ```
//!
//! # Behavior
//!
//! `conjure_runtime` wraps the `hyper` HTTP library with opinionated behavior designed to more effectively communicate
//! between services in a distributed system. It is broadly designed to align with the [`conjure-java-runtime`] Java
//! library, though it does differ in various ways.
//!
//! ## Error Propagation
//!
//! Servers should use the standard Conjure error format to propagate application-specific errors to callers. Non-QoS
//! (see below) errors received from the server are treated as fatal. By default, `conjure_runtime` will return a
//! `conjure_error::Error` that will generate a generic 500 Internal Server Error response. Its cause will be a
//! `RemoteError` object that contains the serialized Conjure error information sent by the server. The
//! `Client::set_propagate_service_errors` method can be used to change that behavior to instead transparently propagate
//! the error received from the server. Rather than producing a generic 500 response, the returned
//! `conjure_error::Error` will produce the same response the client received from the server.
//!
//! ## Call Tracing
//!
//! The client propagates trace information via the [`zipkin`] crate using the traditional `X-B3-*` HTTP headers. It
//! also creates local spans covering various stages of request processing:
//!
//! * `conjure-runtime: get /widget-service/{widgetId}` - The name of this span is built from the request's method and
//!     path pattern.
//!     * `conjure-runtime: attempt 1`
//!         * `conjure-runtime: wait-for-headers` - This span is sent to the server, and lasts until the server sends
//!             the headers of the response.
//!         * `conjure-runtime: wait-for-body` - This span is tracked along with the response body, and lasts until the
//!             `ResponseBody` object is dropped. It is "detached" from the zipkin tracer so new spans created outside
//!             of `conjure-runtime` will not be parented to it, and can outlive the parent `conjure-runtime` spans. It
//!             will not be created if an IO error occurs before headers are received.
//!     * `conjure-runtime: backoff-with-jitter` - If the request encounters an IO error before receiving headers, this
//!         span covers the time spent waiting before the request is retried.
//!     * `conjure-runtime: attempt 2`
//!         * ...
//!
//! ## Quality of Service: Retry, Failover, Throttling, and Backpressure
//!
//! The client treats certain HTTP errors specially. Servers can advertise an overloaded state via the 429 Too Many
//! Requests or 503 Service Unavailable status codes. Unlike other 4xx and 5xx status codes, these responses do *not*
//! cause the request to fail. Instead, `conjure_runtime` will throttle itself and retry the request. Requests are
//! retried a fixed number of times, with an exponentially growing backoff in between attempts. If a 429 response
//! contains a `Retry-After` header, its backoff will be used rather than the default. IO errors also trigger a retry.
//!
//! A 503 response or IO error will also cause that host to be temporarily "blacklisted" so it will not be used by other
//! requests unless there is no other option.
//!
//! Only some requests can be retried. By default, `conjure_runtime` will only retry requests with HTTP methods
//! identified as idempotent - `GET`, `PUT`, `DELETE`, `HEAD`, `TRACE`, and `OPTIONS`. Non-idempotent requests cannot be
//! safely retried to avoid the risk of unexpected behavior if the request ends up being applied twice. The
//! `Client::set_assume_idempotent` method can be used to override this behavior and have the client assume all requests
//! are idempotent. In addition, requests with streaming request bodies can only be retried if the body had either not
//! started to be written when the error occurred or if it was successfully reset for another attempt.
//!
//! ## Metrics
//!
//! Clients record metrics to both a standard `MetricsRegistry` and a `conjure_runtime`-specific `HostMetricsRegistry`.
//!
//! ### Standard Metrics
//!
//! * `client.request (service: <service_name>)` - A `Timer` recording request durations, tagged by service. Note that
//!     the requests timed by this metric are the individual raw HTTP request attempts, *not* `conjure_runtime`-level
//!     requests with retries/backoffs/etc. It only records the time until response headers are received, not until the
//!     entire response body is read.
//! * `client.request.error (service: <service_name>, reason: IOException)` - A `Meter` tracking the rate of IO errors,
//!     tagged by service. Like the `client.request` metric, this tracks the raw HTTP requests. The `reason` tag has a
//!     value of `IOException` to align with [`conjure-java-runtime`]'s metric.
//!
//! ### Host Metrics
//!
//! The `HostMetricsRegistry` contains metrics for every host of every service being actively used by a
//! `conjure_runtime` client.
//!
//! [Conjure]: https://github.com/palantir/conjure
//! [`conjure-java-runtime`]: https://github.com/palantir/conjure-java-runtime
//! [`zipkin`]: https://docs.rs/zipkin
#![doc(html_root_url = "https://docs.rs/conjure-runtime/0.1")]
#![warn(missing_docs, clippy::all)]

pub use crate::body::*;
pub use crate::client::*;
pub use crate::metrics::*;
pub use crate::payload::*;
pub use crate::request::*;
pub use crate::response::*;
pub use crate::user_agent::*;
use hyper::header::HeaderValue;
use once_cell::sync::Lazy;

pub mod blocking;
mod body;
mod client;
mod conjure;
pub mod errors;
mod metrics;
mod node_selector;
mod payload;
mod proxy;
mod request;
mod response;
mod send;
#[cfg(test)]
mod test;
mod user_agent;

/// Client configuration.
///
/// This is just a reexport of the `conjure_runtime_config` crate for convenience.
pub mod config {
    #[doc(inline)]
    pub use conjure_runtime_config::*;
}

static APPLICATION_JSON: Lazy<HeaderValue> =
    Lazy::new(|| HeaderValue::from_static("application/json"));
static APPLICATION_OCTET_STREAM: Lazy<HeaderValue> =
    Lazy::new(|| HeaderValue::from_static("application/octet-stream"));