reasoninglayer 0.1.1

//! Internal HTTP client wrapping `reqwest` with auth header injection, retry-with-backoff, and
//! timeout enforcement. Not part of the public API.

use std::sync::Arc;
use std::time::Duration;

use reqwest::header::{HeaderName, HeaderValue, AUTHORIZATION, CONTENT_TYPE};
use reqwest::{Method, StatusCode};
use serde::de::DeserializeOwned;
use serde::Serialize;
use serde_json::Value;

use crate::config::{ResolvedConfig, SDK_LANGUAGE, SDK_VERSION};
use crate::error::{ApiError, ApiErrorKind, Error};
use crate::types::common::{ApiResponse, RateLimitInfo, RequestOptions};

const API_PREFIX: &str = "/api/v1";
const MAX_BACKOFF: Duration = Duration::from_secs(30);
const BASE_BACKOFF_MS: u64 = 1_000;

/// HTTP methods supported by the SDK.
#[derive(Debug, Clone, Copy)]
pub(crate) enum HttpMethod {
    Get,
    Post,
    Put,
    Delete,
    #[allow(dead_code)]
    Patch,
}

impl From<HttpMethod> for Method {
    fn from(m: HttpMethod) -> Self {
        match m {
            HttpMethod::Get => Method::GET,
            HttpMethod::Post => Method::POST,
            HttpMethod::Put => Method::PUT,
            HttpMethod::Delete => Method::DELETE,
            HttpMethod::Patch => Method::PATCH,
        }
    }
}

/// Internal HTTP client used by resource clients.
#[derive(Debug, Clone)]
pub(crate) struct HttpClient {
    pub(crate) inner: reqwest::Client,
    pub(crate) config: Arc<ResolvedConfig>,
}

impl HttpClient {
    /// Build a new client from resolved config.
    pub(crate) fn new(config: ResolvedConfig) -> Result<Self, Error> {
        let inner = reqwest::Client::builder()
            .build()
            .map_err(|err| Error::Network {
                message: err.to_string(),
                source: Some(Box::new(err)),
            })?;
        Ok(Self {
            inner,
            config: Arc::new(config),
        })
    }

    pub(crate) async fn get<Resp>(
        &self,
        path: &str,
        query: Option<&[(&str, &str)]>,
        opts: Option<&RequestOptions>,
    ) -> Result<Resp, Error>
    where
        Resp: DeserializeOwned,
    {
        let response = self
            .request_raw::<()>(HttpMethod::Get, path, query, None, opts)
            .await?;
        decode_value(response.data)
    }

    pub(crate) async fn post<Body, Resp>(
        &self,
        path: &str,
        body: &Body,
        opts: Option<&RequestOptions>,
    ) -> Result<Resp, Error>
    where
        Body: Serialize + ?Sized,
        Resp: DeserializeOwned,
    {
        let response = self
            .request_raw(HttpMethod::Post, path, None, Some(body), opts)
            .await?;
        decode_value(response.data)
    }

    pub(crate) async fn put<Body, Resp>(
        &self,
        path: &str,
        body: &Body,
        opts: Option<&RequestOptions>,
    ) -> Result<Resp, Error>
    where
        Body: Serialize + ?Sized,
        Resp: DeserializeOwned,
    {
        let response = self
            .request_raw(HttpMethod::Put, path, None, Some(body), opts)
            .await?;
        decode_value(response.data)
    }

    pub(crate) async fn delete<Resp>(
        &self,
        path: &str,
        query: Option<&[(&str, &str)]>,
        opts: Option<&RequestOptions>,
    ) -> Result<Resp, Error>
    where
        Resp: DeserializeOwned,
    {
        let response = self
            .request_raw::<()>(HttpMethod::Delete, path, query, None, opts)
            .await?;
        decode_value(response.data)
    }

    pub(crate) async fn patch<Body, Resp>(
        &self,
        path: &str,
        body: &Body,
        opts: Option<&RequestOptions>,
    ) -> Result<Resp, Error>
    where
        Body: Serialize + ?Sized,
        Resp: DeserializeOwned,
    {
        let response = self
            .request_raw(HttpMethod::Patch, path, None, Some(body), opts)
            .await?;
        decode_value(response.data)
    }

    pub(crate) async fn post_with_query<Body, Resp>(
        &self,
        path: &str,
        query: Option<&[(&str, &str)]>,
        body: &Body,
        opts: Option<&RequestOptions>,
    ) -> Result<Resp, Error>
    where
        Body: Serialize + ?Sized,
        Resp: DeserializeOwned,
    {
        let response = self
            .request_raw(HttpMethod::Post, path, query, Some(body), opts)
            .await?;
        decode_value(response.data)
    }

    /// Execute an HTTP request, handling auth, retries, and timeouts. Returns the parsed body plus
    /// response metadata.
    pub(crate) async fn request_raw<Body>(
        &self,
        method: HttpMethod,
        path: &str,
        query: Option<&[(&str, &str)]>,
        body: Option<&Body>,
        opts: Option<&RequestOptions>,
    ) -> Result<ApiResponse<Value>, Error>
    where
        Body: Serialize + ?Sized,
    {
        let max_retries = opts
            .and_then(|o| o.retries)
            .unwrap_or(self.config.max_retries);
        let timeout = opts.and_then(|o| o.timeout).unwrap_or(self.config.timeout);

        let resolved_path = resolve_path(path);
        let url = format!("{}{}", self.config.base_url, resolved_path);

        let serialized_body = match body {
            Some(b) => Some(serde_json::to_vec(b)?),
            None => None,
        };

        let mut attempt: u32 = 0;
        loop {
            let mut request = self
                .inner
                .request(method.into(), &url)
                .timeout(timeout)
                .header(CONTENT_TYPE, "application/json")
                .header(HeaderName::from_static("accept"), "application/json")
                .header(HeaderName::from_static("x-sdk-version"), SDK_VERSION)
                .header(HeaderName::from_static("x-sdk-language"), SDK_LANGUAGE)
                .header(
                    HeaderName::from_static("x-tenant-id"),
                    &self.config.tenant_id,
                );

            if let Some(user_id) = opts
                .and_then(|o| o.user_id.as_deref())
                .or(self.config.user_id.as_deref())
            {
                request = request.header(HeaderName::from_static("x-user-id"), user_id);
            }
            if let Some(namespace_id) = opts
                .and_then(|o| o.namespace_id.as_deref())
                .or(self.config.namespace_id.as_deref())
            {
                request = request.header(HeaderName::from_static("x-namespace-id"), namespace_id);
            }
            if let Some(user) = self.config.authenticated_user.as_deref() {
                request = request.header(HeaderName::from_static("x-authenticated-user"), user);
            }
            if let Some(token) = self.config.bearer_token.as_deref() {
                let value = HeaderValue::from_str(&format!("Bearer {token}")).map_err(|_| {
                    Error::validation("bearer_token", "invalid characters in bearer token")
                })?;
                request = request.header(AUTHORIZATION, value);
            }
            for (name, value) in &self.config.extra_headers {
                request = request.header(name.as_str(), value.as_str());
            }
            if let Some(q) = query {
                request = request.query(q);
            }
            if let Some(bytes) = &serialized_body {
                request = request.body(bytes.clone());
            }

            match request.send().await {
                Ok(response) => {
                    let status = response.status();
                    let headers = response.headers().clone();
                    let rate_limit = RateLimitInfo::from_headers(&headers);

                    if status.is_success() {
                        if status == StatusCode::NO_CONTENT {
                            return Ok(ApiResponse {
                                data: Value::Null,
                                status,
                                headers,
                                rate_limit,
                            });
                        }
                        let bytes = response
                            .bytes()
                            .await
                            .map_err(|err| map_runtime(err, timeout))?;
                        let data = if bytes.is_empty() {
                            Value::Null
                        } else {
                            serde_json::from_slice(&bytes)?
                        };
                        return Ok(ApiResponse {
                            data,
                            status,
                            headers,
                            rate_limit,
                        });
                    }

                    let body_bytes = response
                        .bytes()
                        .await
                        .map_err(|err| map_runtime(err, timeout))?;
                    let body_value: Option<Value> = if body_bytes.is_empty() {
                        None
                    } else {
                        serde_json::from_slice(&body_bytes).ok()
                    };
                    let api_error = ApiError::from_response(status, body_value, headers);

                    if should_retry_status(status, self.config.retry_on_503)
                        && attempt < max_retries
                    {
                        let delay = retry_delay_from_api_error(&api_error, attempt + 1);
                        attempt += 1;
                        tokio::time::sleep(delay).await;
                        continue;
                    }
                    return Err(Error::from(api_error));
                }
                Err(err) => {
                    if err.is_timeout() {
                        return Err(Error::Timeout { timeout });
                    }
                    if attempt < max_retries && is_retryable_network_error(&err) {
                        let delay = backoff_delay(attempt + 1);
                        attempt += 1;
                        tokio::time::sleep(delay).await;
                        continue;
                    }
                    return Err(map_runtime(err, timeout));
                }
            }
        }
    }
}

fn decode_value<T: DeserializeOwned>(v: Value) -> Result<T, Error> {
    serde_json::from_value(v).map_err(Error::Serde)
}

/// Paths that are rooted at the server (no `/api/v1` prefix).
const ABSOLUTE_PREFIXES: &[&str] = &[
    "/api/",
    "/health",
    "/ready",
    "/live",
    "/metrics",
    "/ws/",
    "/api-docs",
    "/swagger-ui",
];

/// Resolve a user-supplied path: prepend `/api/v1` unless the path is already absolute.
/// The caller is responsible for URL-encoding path parameters.
pub(crate) fn resolve_path_public(path: &str) -> String {
    resolve_path(path)
}

fn resolve_path(path: &str) -> String {
    if ABSOLUTE_PREFIXES
        .iter()
        .any(|p| path == *p || path.starts_with(p))
    {
        path.to_string()
    } else if path.starts_with('/') {
        format!("{API_PREFIX}{path}")
    } else {
        format!("{API_PREFIX}/{path}")
    }
}

fn should_retry_status(status: StatusCode, retry_on_503: bool) -> bool {
    if status == StatusCode::TOO_MANY_REQUESTS {
        return true;
    }
    if status == StatusCode::SERVICE_UNAVAILABLE && retry_on_503 {
        return true;
    }
    false
}

fn retry_delay_from_api_error(err: &ApiError, attempt: u32) -> Duration {
    if err.kind == ApiErrorKind::RateLimit {
        if let Some(rl) = err.rate_limit() {
            if let Some(secs) = rl.retry_after {
                return Duration::from_secs(secs);
            }
        }
    }
    backoff_delay(attempt)
}

/// Exponential backoff with jitter: `min(1000 * 2^(attempt-1) + random(0..=1000), 30_000)` ms.
fn backoff_delay(attempt: u32) -> Duration {
    use rand::Rng;
    let shift = attempt.saturating_sub(1).min(16);
    let exp = BASE_BACKOFF_MS.saturating_mul(1u64 << shift);
    let jitter: u64 = rand::thread_rng().gen_range(0..=1_000);
    let total = exp.saturating_add(jitter);
    let capped = total.min(MAX_BACKOFF.as_millis() as u64);
    Duration::from_millis(capped)
}

fn is_retryable_network_error(err: &reqwest::Error) -> bool {
    err.is_connect() || err.is_request() || err.is_body()
}

fn map_runtime(err: reqwest::Error, timeout: Duration) -> Error {
    if err.is_timeout() {
        return Error::Timeout { timeout };
    }
    Error::Network {
        message: err.to_string(),
        source: Some(Box::new(err)),
    }
}