cli-engine 0.1.0

use std::{
    collections::BTreeMap,
    io::Write,
    path::Path,
    sync::{Arc, OnceLock, RwLock},
    time::Duration,
};

use reqwest::{Method, StatusCode, header};
use serde::{Serialize, de::DeserializeOwned};
use serde_json::Value;
use tokio::time;

use super::{AuthInjector, Error};
use crate::{CliCoreError, Result};

const MAX_RETRIES: usize = 3;
const BASE_BACKOFF: Duration = Duration::from_millis(500);
const BUILTIN_DEFAULT_USER_AGENT: &str = "cli/dev";
static DEFAULT_USER_AGENT: OnceLock<RwLock<String>> = OnceLock::new();

/// Sets the user-agent used by subsequently created [`HttpClient`] values.
pub fn set_default_user_agent(user_agent: impl Into<String>) {
    let lock =
        DEFAULT_USER_AGENT.get_or_init(|| RwLock::new(BUILTIN_DEFAULT_USER_AGENT.to_owned()));
    if let Ok(mut current) = lock.write() {
        *current = user_agent.into();
    }
}

fn default_user_agent() -> String {
    DEFAULT_USER_AGENT
        .get_or_init(|| RwLock::new(BUILTIN_DEFAULT_USER_AGENT.to_owned()))
        .read()
        .map_or_else(
            |_| BUILTIN_DEFAULT_USER_AGENT.to_owned(),
            |value| value.clone(),
        )
}

#[derive(serde::Deserialize)]
struct GraphQlError {
    message: String,
}

#[derive(Default, serde::Deserialize)]
struct GraphQlEnvelope {
    data: Option<Value>,
    #[serde(default)]
    errors: Vec<GraphQlError>,
}

/// Structured debug event emitted by [`TransportLogger`].
#[derive(Clone, Debug)]
pub struct TransportLogEvent {
    /// Event name such as `http request` or `retrying request`.
    pub message: &'static str,
    /// Stable event fields.
    pub fields: BTreeMap<String, String>,
}

/// Debug logger interface for transport events.
pub trait TransportLogger: Send + Sync + std::fmt::Debug {
    /// Records one debug event.
    fn debug(&self, event: &TransportLogEvent);
}

/// Logger that intentionally drops transport events.
#[derive(Clone, Debug, Default)]
pub struct NoopTransportLogger;

impl TransportLogger for NoopTransportLogger {
    fn debug(&self, _event: &TransportLogEvent) {}
}

/// Authenticated HTTP client for CLI command implementations.
///
/// The client covers the transport behavior command authors usually need: auth
/// injection, JSON request/response helpers, structured HTTP errors,
/// idempotent retries, ETag helpers, raw streaming helpers, multipart helpers,
/// and GraphQL envelope decoding.
#[derive(Clone, Debug)]
pub struct HttpClient {
    base: reqwest::Client,
    base_url: String,
    auth: Arc<dyn AuthInjector>,
    user_agent: String,
    default_headers: BTreeMap<String, String>,
    logger: Arc<dyn TransportLogger>,
}

/// Builder for [`HttpClient`].
#[derive(Clone, Debug)]
pub struct HttpClientBuilder {
    base_url: String,
    auth: Arc<dyn AuthInjector>,
    user_agent: String,
    default_headers: BTreeMap<String, String>,
    logger: Arc<dyn TransportLogger>,
}

impl HttpClientBuilder {
    /// Creates a builder with a base URL and auth injector.
    #[must_use]
    pub fn new(base_url: impl Into<String>, auth: Arc<dyn AuthInjector>) -> Self {
        Self {
            base_url: base_url.into(),
            auth,
            user_agent: default_user_agent(),
            default_headers: BTreeMap::new(),
            logger: Arc::new(NoopTransportLogger),
        }
    }

    /// Sets the user-agent for this client.
    #[must_use]
    pub fn user_agent(mut self, user_agent: impl Into<String>) -> Self {
        self.user_agent = user_agent.into();
        self
    }

    /// Alias for [`HttpClientBuilder::user_agent`] for migration readability.
    #[must_use]
    pub fn with_user_agent(self, user_agent: impl Into<String>) -> Self {
        self.user_agent(user_agent)
    }

    /// Sets headers sent on every request.
    #[must_use]
    pub fn default_headers(mut self, headers: BTreeMap<String, String>) -> Self {
        self.default_headers = headers;
        self
    }

    /// Alias for [`HttpClientBuilder::default_headers`] for migration readability.
    #[must_use]
    pub fn with_default_headers(self, headers: BTreeMap<String, String>) -> Self {
        self.default_headers(headers)
    }

    /// Sets the transport debug logger.
    #[must_use]
    pub fn logger(mut self, logger: Arc<dyn TransportLogger>) -> Self {
        self.logger = logger;
        self
    }

    /// Alias for [`HttpClientBuilder::logger`] for migration readability.
    #[must_use]
    pub fn with_logger(self, logger: Arc<dyn TransportLogger>) -> Self {
        self.logger(logger)
    }

    /// Builds the client.
    #[must_use]
    pub fn build(self) -> HttpClient {
        HttpClient {
            base: reqwest::Client::new(),
            base_url: self.base_url,
            auth: self.auth,
            user_agent: self.user_agent,
            default_headers: self.default_headers,
            logger: self.logger,
        }
    }
}

impl HttpClient {
    /// Creates a client builder.
    #[must_use]
    pub fn builder(base_url: impl Into<String>, auth: Arc<dyn AuthInjector>) -> HttpClientBuilder {
        HttpClientBuilder::new(base_url, auth)
    }

    /// Creates a client with default settings.
    #[must_use]
    pub fn new(base_url: impl Into<String>, auth: Arc<dyn AuthInjector>) -> Self {
        HttpClientBuilder::new(base_url, auth).build()
    }

    /// Sends GET and decodes a JSON response.
    pub async fn get<T: Default + DeserializeOwned>(&self, path: &str) -> Result<T> {
        self.do_json(Method::GET, path, Option::<&()>::None).await
    }

    /// Sends GET and checks only for success.
    pub async fn get_without_response(&self, path: &str) -> Result<()> {
        self.do_empty(Method::GET, path, Option::<&()>::None).await
    }

    /// Sends POST with a JSON body and decodes a JSON response.
    pub async fn post<B: Serialize, T: Default + DeserializeOwned>(
        &self,
        path: &str,
        body: &B,
    ) -> Result<T> {
        self.do_json(Method::POST, path, Some(body)).await
    }

    /// Sends POST with a JSON body and checks only for success.
    pub async fn post_without_response<B: Serialize>(&self, path: &str, body: &B) -> Result<()> {
        self.do_empty(Method::POST, path, Some(body)).await
    }

    /// Sends PUT with a JSON body and decodes a JSON response.
    pub async fn put<B: Serialize, T: Default + DeserializeOwned>(
        &self,
        path: &str,
        body: &B,
    ) -> Result<T> {
        self.do_json(Method::PUT, path, Some(body)).await
    }

    /// Sends PUT with a JSON body and checks only for success.
    pub async fn put_without_response<B: Serialize>(&self, path: &str, body: &B) -> Result<()> {
        self.do_empty(Method::PUT, path, Some(body)).await
    }

    /// Sends PATCH with a JSON body and decodes a JSON response.
    pub async fn patch<B: Serialize, T: Default + DeserializeOwned>(
        &self,
        path: &str,
        body: &B,
    ) -> Result<T> {
        self.do_json(Method::PATCH, path, Some(body)).await
    }

    /// Sends PATCH with a JSON body and checks only for success.
    pub async fn patch_without_response<B: Serialize>(&self, path: &str, body: &B) -> Result<()> {
        self.do_empty(Method::PATCH, path, Some(body)).await
    }

    /// Sends DELETE and checks for success.
    pub async fn delete(&self, path: &str) -> Result<()> {
        self.do_empty(Method::DELETE, path, Option::<&()>::None)
            .await
    }

    /// Sends DELETE with a JSON body and checks for success.
    pub async fn delete_with_body<B: Serialize>(&self, path: &str, body: &B) -> Result<()> {
        self.do_empty(Method::DELETE, path, Some(body)).await
    }

    /// Sends GET and returns decoded JSON plus the ETag header.
    pub async fn get_etag<T: Default + DeserializeOwned>(&self, path: &str) -> Result<(T, String)> {
        let response = self.send_get_status_only_retry(path).await?;
        let etag = response
            .headers()
            .get(header::ETAG)
            .and_then(|value| value.to_str().ok())
            .unwrap_or_default()
            .to_owned();
        let value = decode_json_response(response, "GET", path).await?;
        Ok((value, etag))
    }

    /// Sends GET and returns only the ETag header after checking success.
    pub async fn get_etag_without_response(&self, path: &str) -> Result<String> {
        let response = self.send_get_status_only_retry(path).await?;
        let etag = response
            .headers()
            .get(header::ETAG)
            .and_then(|value| value.to_str().ok())
            .unwrap_or_default()
            .to_owned();
        ensure_success_response(response, "GET", path).await?;
        Ok(etag)
    }

    /// Sends PUT with `If-Match` and decodes a JSON response.
    pub async fn put_if_match<B: Serialize, T: Default + DeserializeOwned>(
        &self,
        path: &str,
        body: &B,
        etag: &str,
    ) -> Result<T> {
        let response = self.send_put_if_match(path, body, etag).await?;
        decode_json_response(response, "PUT", path).await
    }

    /// Sends PUT with `If-Match` and checks only for success.
    pub async fn put_if_match_without_response<B: Serialize>(
        &self,
        path: &str,
        body: &B,
        etag: &str,
    ) -> Result<()> {
        let response = self.send_put_if_match(path, body, etag).await?;
        ensure_success_response(response, "PUT", path).await
    }

    /// Streams a raw GET response body into a writer.
    pub async fn get_raw(&self, path: &str, writer: &mut dyn Write) -> Result<()> {
        let response = self.send_get_raw_status_only_retry(path).await?;
        if response.status().is_client_error() || response.status().is_server_error() {
            return Err(parse_error_response(response, "GET", path).await.into());
        }
        let bytes = response
            .bytes()
            .await
            .map_err(|err| CliCoreError::message(format!("transport: stream response: {err}")))?;
        writer.write_all(&bytes)?;
        Ok(())
    }

    /// Sends POST and streams the raw response body into a writer.
    pub async fn post_raw<B: Serialize>(
        &self,
        path: &str,
        body: Option<&B>,
        writer: &mut dyn Write,
    ) -> Result<()> {
        let response = self.send_post_raw_once(path, body).await?;
        if response.status().is_client_error() || response.status().is_server_error() {
            return Err(parse_error_response(response, "POST", path).await.into());
        }
        let bytes = response
            .bytes()
            .await
            .map_err(|err| CliCoreError::message(format!("transport: stream response: {err}")))?;
        writer.write_all(&bytes)?;
        Ok(())
    }

    /// Sends a raw-body request and decodes a JSON response.
    pub async fn do_raw<T: Default + DeserializeOwned>(
        &self,
        method: Method,
        path: &str,
        content_type: &str,
        body: impl Into<Vec<u8>>,
    ) -> Result<T> {
        self.do_raw_optional_body(method, path, content_type, Some(body.into()))
            .await
    }

    /// Sends an optional raw-body request and decodes a JSON response.
    pub async fn do_raw_optional_body<T: Default + DeserializeOwned>(
        &self,
        method: Method,
        path: &str,
        content_type: &str,
        body: Option<Vec<u8>>,
    ) -> Result<T> {
        let method_text = method.as_str().to_owned();
        let response = self.send_raw_once(method, path, content_type, body).await?;
        decode_json_response(response, &method_text, path).await
    }

    /// Sends a raw-body request and checks only for success.
    pub async fn do_raw_without_response(
        &self,
        method: Method,
        path: &str,
        content_type: &str,
        body: impl Into<Vec<u8>>,
    ) -> Result<()> {
        self.do_raw_optional_body_without_response(method, path, content_type, Some(body.into()))
            .await
    }

    /// Sends an optional raw-body request and checks only for success.
    pub async fn do_raw_optional_body_without_response(
        &self,
        method: Method,
        path: &str,
        content_type: &str,
        body: Option<Vec<u8>>,
    ) -> Result<()> {
        let method_text = method.as_str().to_owned();
        let response = self.send_raw_once(method, path, content_type, body).await?;
        ensure_success_response(response, &method_text, path).await
    }

    /// Sends a multipart file upload and decodes a JSON response.
    pub async fn post_multipart<T: Default + DeserializeOwned>(
        &self,
        path: &str,
        field_name: &str,
        file_path: &Path,
    ) -> Result<T> {
        self.post_multipart_with_fields(path, field_name, file_path, &BTreeMap::new())
            .await
    }

    /// Sends a multipart file upload and checks only for success.
    pub async fn post_multipart_without_response(
        &self,
        path: &str,
        field_name: &str,
        file_path: &Path,
    ) -> Result<()> {
        self.post_multipart_with_fields_without_response(
            path,
            field_name,
            file_path,
            &BTreeMap::new(),
        )
        .await
    }

    /// Sends a multipart file upload with fields and decodes a JSON response.
    pub async fn post_multipart_with_fields<T: Default + DeserializeOwned>(
        &self,
        path: &str,
        file_field: &str,
        file_path: &Path,
        fields: &BTreeMap<String, String>,
    ) -> Result<T> {
        let form = self.multipart_form(file_field, file_path, fields).await?;
        self.send_multipart(path, form).await
    }

    async fn multipart_form(
        &self,
        file_field: &str,
        file_path: &Path,
        fields: &BTreeMap<String, String>,
    ) -> Result<reqwest::multipart::Form> {
        let mut form = reqwest::multipart::Form::new();
        for (key, value) in fields {
            form = form.text(key.clone(), value.clone());
        }
        let file_name = file_path
            .file_name()
            .and_then(|name| name.to_str())
            .unwrap_or("file")
            .to_owned();
        let bytes = tokio::fs::read(file_path)
            .await
            .map_err(|err| CliCoreError::message(format!("transport: open file: {err}")))?;
        let part = reqwest::multipart::Part::bytes(bytes).file_name(file_name);
        form = form.part(file_field.to_owned(), part);
        Ok(form)
    }

    /// Sends a multipart file upload with fields and checks only for success.
    pub async fn post_multipart_with_fields_without_response(
        &self,
        path: &str,
        file_field: &str,
        file_path: &Path,
        fields: &BTreeMap<String, String>,
    ) -> Result<()> {
        let form = self.multipart_form(file_field, file_path, fields).await?;
        self.send_multipart_without_response(path, form).await
    }

    /// Sends multipart form fields without a file and decodes a JSON response.
    pub async fn post_multipart_fields<T: Default + DeserializeOwned>(
        &self,
        path: &str,
        fields: &BTreeMap<String, String>,
    ) -> Result<T> {
        let mut form = reqwest::multipart::Form::new();
        for (key, value) in fields {
            form = form.text(key.clone(), value.clone());
        }
        self.send_multipart(path, form).await
    }

    /// Sends multipart form fields without a file and checks only for success.
    pub async fn post_multipart_fields_without_response(
        &self,
        path: &str,
        fields: &BTreeMap<String, String>,
    ) -> Result<()> {
        let mut form = reqwest::multipart::Form::new();
        for (key, value) in fields {
            form = form.text(key.clone(), value.clone());
        }
        self.send_multipart_without_response(path, form).await
    }

    /// Sends a GraphQL request and decodes the `data` envelope into a value.
    pub async fn post_graphql<T: DeserializeOwned + Default>(
        &self,
        path: &str,
        query: &str,
        variables: BTreeMap<String, Value>,
    ) -> Result<T> {
        self.post_graphql_optional_variables(path, query, Some(variables))
            .await
    }

    /// Sends a GraphQL request with optional variables and decodes `data`.
    pub async fn post_graphql_optional_variables<T: DeserializeOwned + Default>(
        &self,
        path: &str,
        query: &str,
        variables: Option<BTreeMap<String, Value>>,
    ) -> Result<T> {
        let mut result = T::default();
        self.post_graphql_optional_variables_into(path, query, variables, &mut result)
            .await?;
        Ok(result)
    }

    /// Sends a GraphQL request and checks only for GraphQL/HTTP success.
    pub async fn post_graphql_without_response(
        &self,
        path: &str,
        query: &str,
        variables: BTreeMap<String, Value>,
    ) -> Result<()> {
        self.post_graphql_optional_variables_without_response(path, query, Some(variables))
            .await
    }

    /// Sends a GraphQL request with optional variables and checks only for success.
    pub async fn post_graphql_optional_variables_without_response(
        &self,
        path: &str,
        query: &str,
        variables: Option<BTreeMap<String, Value>>,
    ) -> Result<()> {
        self.post_graphql_response_envelope(path, query, variables)
            .await?;
        Ok(())
    }

    /// Sends a GraphQL request and decodes `data` into an existing value.
    pub async fn post_graphql_into<T: DeserializeOwned>(
        &self,
        path: &str,
        query: &str,
        variables: BTreeMap<String, Value>,
        result: &mut T,
    ) -> Result<()> {
        self.post_graphql_optional_variables_into(path, query, Some(variables), result)
            .await
    }

    /// Sends a GraphQL request with optional variables and decodes into an existing value.
    pub async fn post_graphql_optional_variables_into<T: DeserializeOwned>(
        &self,
        path: &str,
        query: &str,
        variables: Option<BTreeMap<String, Value>>,
        result: &mut T,
    ) -> Result<()> {
        let envelope = self
            .post_graphql_response_envelope(path, query, variables)
            .await?;
        if let Some(data) = envelope.data
            && !data.is_null()
        {
            *result = serde_json::from_value(data).map_err(|err| {
                CliCoreError::message(format!("transport: decode graphql data: {err}"))
            })?;
        }
        Ok(())
    }

    async fn do_json<B: Serialize, T: Default + DeserializeOwned>(
        &self,
        method: Method,
        path: &str,
        body: Option<&B>,
    ) -> Result<T> {
        let method_text = method.as_str().to_owned();
        let response = self.send_with_retry(method, path, body).await?;
        decode_json_response(response, &method_text, path).await
    }

    async fn post_graphql_response_envelope(
        &self,
        path: &str,
        query: &str,
        variables: Option<BTreeMap<String, Value>>,
    ) -> Result<GraphQlEnvelope> {
        #[derive(Serialize)]
        struct Request<'query> {
            query: &'query str,
            variables: Option<BTreeMap<String, Value>>,
        }

        let envelope: GraphQlEnvelope = self.post(path, &Request { query, variables }).await?;
        if !envelope.errors.is_empty() {
            let message = envelope
                .errors
                .iter()
                .map(|error| error.message.as_str())
                .collect::<Vec<_>>()
                .join("; ");
            return Err(CliCoreError::message(format!("graphql: {message}")));
        }
        Ok(envelope)
    }

    async fn send_put_if_match<B: Serialize>(
        &self,
        path: &str,
        body: &B,
        etag: &str,
    ) -> Result<reqwest::Response> {
        let mut request = self
            .build_request(Method::PUT, path, Some(body))?
            .header(header::IF_MATCH, etag)
            .build()
            .map_err(|err| CliCoreError::message(format!("transport: create request: {err}")))?;
        self.inject_auth(&mut request).await?;
        let url = format!("{}{}", self.base_url, path);
        self.log_debug(
            "http request",
            [("method", "PUT".to_owned()), ("url", url.clone())],
        );
        let response = self
            .base
            .execute(request)
            .await
            .map_err(|err| CliCoreError::message(format!("transport: PUT {path}: {err}")))?;
        self.log_debug(
            "http response",
            [
                ("status", response.status().as_u16().to_string()),
                ("method", "PUT".to_owned()),
                ("url", url),
            ],
        );
        Ok(response)
    }

    async fn send_multipart<T: Default + DeserializeOwned>(
        &self,
        path: &str,
        form: reqwest::multipart::Form,
    ) -> Result<T> {
        let response = self.send_multipart_response(path, form).await?;
        decode_json_response(response, "POST", path).await
    }

    async fn send_multipart_without_response(
        &self,
        path: &str,
        form: reqwest::multipart::Form,
    ) -> Result<()> {
        let response = self.send_multipart_response(path, form).await?;
        ensure_success_response(response, "POST", path).await
    }

    async fn send_multipart_response(
        &self,
        path: &str,
        form: reqwest::multipart::Form,
    ) -> Result<reqwest::Response> {
        let url = format!("{}{}", self.base_url, path);
        let mut builder = self
            .base
            .post(url.clone())
            .header(header::USER_AGENT, self.user_agent.clone())
            .multipart(form);
        for (key, value) in &self.default_headers {
            builder = builder.header(key, value);
        }
        let mut request = builder
            .build()
            .map_err(|err| CliCoreError::message(format!("transport: create request: {err}")))?;
        self.inject_auth(&mut request).await?;
        self.log_debug("http multipart request", [("url", url)]);
        self.base
            .execute(request)
            .await
            .map_err(|err| CliCoreError::message(format!("transport: POST {path}: {err}")))
    }

    async fn do_empty<B: Serialize>(
        &self,
        method: Method,
        path: &str,
        body: Option<&B>,
    ) -> Result<()> {
        let method_text = method.as_str().to_owned();
        let response = self.send_with_retry(method, path, body).await?;
        ensure_success_response(response, &method_text, path).await
    }

    async fn send_raw_once(
        &self,
        method: Method,
        path: &str,
        content_type: &str,
        body: Option<Vec<u8>>,
    ) -> Result<reqwest::Response> {
        let url = format!("{}{}", self.base_url, path);
        let method_text = method.as_str().to_owned();
        let mut builder = self
            .base
            .request(method, url)
            .header(header::USER_AGENT, self.user_agent.clone());
        if let Some(body) = body {
            builder = builder.body(body);
        }
        if !content_type.is_empty() {
            builder = builder.header(header::CONTENT_TYPE, content_type);
        }
        for (key, value) in &self.default_headers {
            builder = builder.header(key, value);
        }
        let mut request = builder
            .build()
            .map_err(|err| CliCoreError::message(format!("transport: create request: {err}")))?;
        self.inject_auth(&mut request).await?;
        self.log_debug(
            "http request",
            [
                ("method", method_text.clone()),
                ("url", format!("{}{}", self.base_url, path)),
            ],
        );
        self.base
            .execute(request)
            .await
            .map_err(|err| CliCoreError::message(format!("transport: {method_text} {path}: {err}")))
    }

    async fn send_get_raw_status_only_retry(&self, path: &str) -> Result<reqwest::Response> {
        let mut last_err = None;
        for attempt in 0..MAX_RETRIES {
            if attempt > 0 {
                let backoff = BASE_BACKOFF * 2_u32.pow(u32::try_from(attempt - 1).unwrap_or(0));
                time::sleep(backoff).await;
            }

            match self.send_get_raw_once(path).await {
                Ok(response) => {
                    if response.status() == StatusCode::TOO_MANY_REQUESTS
                        || response.status().is_server_error()
                    {
                        last_err = Some(CliCoreError::message(format!(
                            "transport: GET {}: status {}",
                            path,
                            response.status().as_u16()
                        )));
                        continue;
                    }
                    return Ok(response);
                }
                Err(err) => last_err = Some(err),
            }
        }
        Err(last_err.unwrap_or_else(|| CliCoreError::message("transport: retry failed")))
    }

    async fn send_get_raw_once(&self, path: &str) -> Result<reqwest::Response> {
        let url = format!("{}{}", self.base_url, path);
        let mut builder = self
            .base
            .get(url.clone())
            .header(header::USER_AGENT, self.user_agent.clone());
        for (key, value) in &self.default_headers {
            builder = builder.header(key, value);
        }
        let mut request = builder
            .build()
            .map_err(|err| CliCoreError::message(format!("transport: create request: {err}")))?;
        self.inject_auth(&mut request).await?;
        self.log_debug("http raw request", [("url", url)]);
        self.base
            .execute(request)
            .await
            .map_err(|err| CliCoreError::message(format!("transport: GET {path}: {err}")))
    }

    async fn send_post_raw_once<B: Serialize>(
        &self,
        path: &str,
        body: Option<&B>,
    ) -> Result<reqwest::Response> {
        let mut request = self
            .build_request(Method::POST, path, body)?
            .build()
            .map_err(|err| CliCoreError::message(format!("transport: create request: {err}")))?;
        self.inject_auth(&mut request).await?;
        self.log_debug(
            "http post raw request",
            [("url", format!("{}{}", self.base_url, path))],
        );
        self.base
            .execute(request)
            .await
            .map_err(|err| CliCoreError::message(format!("transport: POST {path}: {err}")))
    }

    async fn send_with_retry<B: Serialize>(
        &self,
        method: Method,
        path: &str,
        body: Option<&B>,
    ) -> Result<reqwest::Response> {
        let mut last_err = None;
        for attempt in 0..MAX_RETRIES {
            if attempt > 0 {
                let backoff = BASE_BACKOFF * 2_u32.pow(u32::try_from(attempt - 1).unwrap_or(0));
                self.log_debug(
                    "retrying request",
                    [
                        ("attempt", (attempt + 1).to_string()),
                        ("backoff", format!("{backoff:?}")),
                    ],
                );
                time::sleep(backoff).await;
            }

            match self.send_once(method.clone(), path, body).await {
                Ok(response) => {
                    if retryable_status(method.clone(), response.status()) {
                        last_err =
                            Some(retryable_status_error(response, method.as_str(), path).await);
                        continue;
                    }
                    return Ok(response);
                }
                Err(err) if is_idempotent(&method) => {
                    last_err = Some(err);
                }
                Err(err) => return Err(err),
            }
        }
        Err(last_err.unwrap_or_else(|| CliCoreError::message("transport: retry failed")))
    }

    async fn send_get_status_only_retry(&self, path: &str) -> Result<reqwest::Response> {
        let mut last_err = None;
        for attempt in 0..MAX_RETRIES {
            if attempt > 0 {
                let backoff = BASE_BACKOFF * 2_u32.pow(u32::try_from(attempt - 1).unwrap_or(0));
                self.log_debug(
                    "retrying request",
                    [
                        ("attempt", (attempt + 1).to_string()),
                        ("backoff", format!("{backoff:?}")),
                    ],
                );
                time::sleep(backoff).await;
            }

            match self.send_once(Method::GET, path, Option::<&()>::None).await {
                Ok(response) => {
                    if response.status() == StatusCode::TOO_MANY_REQUESTS
                        || response.status().is_server_error()
                    {
                        last_err = Some(CliCoreError::message(format!(
                            "transport: GET {}: status {}",
                            path,
                            response.status().as_u16()
                        )));
                        continue;
                    }
                    return Ok(response);
                }
                Err(err) => last_err = Some(err),
            }
        }
        Err(last_err.unwrap_or_else(|| CliCoreError::message("transport: retry failed")))
    }

    async fn send_once<B: Serialize>(
        &self,
        method: Method,
        path: &str,
        body: Option<&B>,
    ) -> Result<reqwest::Response> {
        let mut request = self
            .build_request(method.clone(), path, body)?
            .build()
            .map_err(|err| CliCoreError::message(format!("transport: create request: {err}")))?;
        self.inject_auth(&mut request).await?;
        let method_text = method.as_str().to_owned();
        self.log_debug(
            "http request",
            [
                ("method", method_text.clone()),
                ("url", format!("{}{}", self.base_url, path)),
            ],
        );
        let response = self.base.execute(request).await.map_err(|err| {
            CliCoreError::message(format!("transport: {method_text} {path}: {err}"))
        })?;
        self.log_debug(
            "http response",
            [
                ("status", response.status().as_u16().to_string()),
                ("method", method_text),
                ("url", format!("{}{}", self.base_url, path)),
            ],
        );
        Ok(response)
    }

    fn build_request<B: Serialize>(
        &self,
        method: Method,
        path: &str,
        body: Option<&B>,
    ) -> Result<reqwest::RequestBuilder> {
        let url = format!("{}{}", self.base_url, path);
        let mut builder = self
            .base
            .request(method, url)
            .header(header::USER_AGENT, self.user_agent.clone());
        if let Some(body) = body {
            let body = serde_json::to_vec(body)
                .map_err(|err| CliCoreError::message(format!("transport: marshal body: {err}")))?;
            builder = builder
                .header(header::CONTENT_TYPE, "application/json")
                .body(body);
        }
        for (key, value) in &self.default_headers {
            builder = builder.header(key, value);
        }
        Ok(builder)
    }

    fn log_debug(
        &self,
        message: &'static str,
        fields: impl IntoIterator<Item = (&'static str, String)>,
    ) {
        self.logger.debug(&TransportLogEvent {
            message,
            fields: fields
                .into_iter()
                .map(|(key, value)| (key.to_owned(), value))
                .collect(),
        });
    }

    async fn inject_auth(&self, request: &mut reqwest::Request) -> Result<()> {
        self.auth
            .inject(request)
            .await
            .map_err(|err| CliCoreError::message(format!("transport: auth inject: {err}")))
    }
}

async fn decode_json_response<T: Default + DeserializeOwned>(
    response: reqwest::Response,
    method: &str,
    path: &str,
) -> Result<T> {
    if response.status().is_client_error() || response.status().is_server_error() {
        return Err(parse_error_response(response, method, path).await.into());
    }
    if response.status() == StatusCode::NO_CONTENT {
        return Ok(T::default());
    }
    let body = response
        .bytes()
        .await
        .map_err(|err| CliCoreError::message(format!("transport: decode response: {err}")))?;
    if body.trim_ascii() == b"null" {
        return Ok(T::default());
    }
    serde_json::from_slice::<T>(&body)
        .map_err(|err| CliCoreError::message(format!("transport: decode response: {err}")))
}

async fn ensure_success_response(
    response: reqwest::Response,
    method: &str,
    path: &str,
) -> Result<()> {
    if response.status().is_client_error() || response.status().is_server_error() {
        return Err(parse_error_response(response, method, path).await.into());
    }
    Ok(())
}

/// Converts a non-success HTTP response into the shared transport error shape.
///
/// If the response body already contains an API-style error document, the
/// service message is preserved and the HTTP status is normalized into the
/// error code. Otherwise the method, path, status, and response body are folded
/// into a readable fallback message.
pub async fn parse_error_response(response: reqwest::Response, method: &str, path: &str) -> Error {
    let status = response.status();
    let body = response.text().await.unwrap_or_default();
    parse_error_body(status, &body, method, path)
}

fn parse_error_body(status: StatusCode, body: &str, method: &str, path: &str) -> Error {
    if let Ok(mut api_error) = serde_json::from_str::<Error>(body)
        && !api_error.message.is_empty()
    {
        api_error.code = format!("HTTP_{}", status.as_u16());
        return api_error;
    }
    Error {
        code: format!("HTTP_{}", status.as_u16()),
        message: format!("{} {}: {} {}", method, path, status.as_u16(), body),
        system: String::new(),
        request_id: String::new(),
    }
}

fn retryable_status(method: Method, status: StatusCode) -> bool {
    status == StatusCode::TOO_MANY_REQUESTS || (status.is_server_error() && is_idempotent(&method))
}

async fn retryable_status_error(
    response: reqwest::Response,
    method: &str,
    path: &str,
) -> CliCoreError {
    let status = response.status().as_u16();
    match response.text().await {
        Ok(body) => CliCoreError::message(format!(
            "transport: {method} {path}: status {status}: {body}"
        )),
        Err(err) => CliCoreError::message(format!(
            "transport: {method} {path}: status {status} (body read failed: {err})"
        )),
    }
}

fn is_idempotent(method: &Method) -> bool {
    matches!(*method, Method::GET | Method::HEAD | Method::DELETE)
}