//! HTTP client for clawdforge.

use std::path::Path;
use std::time::Duration;

use reqwest::header::{HeaderMap, HeaderValue};
use reqwest::multipart::{Form, Part};
use reqwest::{Body, Method, Response, StatusCode};
use serde::de::DeserializeOwned;
use tokio_util::io::ReaderStream;
use url::Url;

use crate::error::Error;
use crate::session::{
    Session, SessionCloseResponse, SessionCreateResponse, SessionList, SessionOptions,
    SessionState, TurnResult,
};
use crate::types::{
    AppToken, FileToken, Healthz, RunRequest, RunResult, TokenCreateRequest, TokenList,
};

/// Default request timeout if neither the builder nor the per-call helper sets
/// one. 120 s leaves headroom over the server's default 60 s `claude` timeout
/// without making `/healthz` callers wait forever on a dead host.
const DEFAULT_TIMEOUT: Duration = Duration::from_secs(120);

/// Async client for the clawdforge HTTP API.
///
/// Construct via [`Client::builder`]. `Client` is cheap to clone — internally
/// it wraps an `Arc`-backed `reqwest::Client`.
///
/// `Debug` is hand-written to redact bearer tokens — `format!("{:?}", client)`
/// will never expose `app_token` or `admin_token` plaintext.
#[derive(Clone)]
pub struct Client {
    inner: reqwest::Client,
    base: Url,
    /// App-level bearer (used for `/run`, `/files`, `/healthz`). Optional so
    /// admin-only callers don't have to mint a worthless app token.
    app_token: Option<String>,
    /// Admin bootstrap token (used for `/admin/*`). Optional.
    admin_token: Option<String>,
    /// Optional cap on `upload_file` size in bytes — `None` = no cap.
    max_upload_bytes: Option<u64>,
}

impl std::fmt::Debug for Client {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_struct("Client")
            .field("base_url", &self.base.as_str())
            .field("app_token", &self.app_token.as_ref().map(|_| "<redacted>"))
            .field(
                "admin_token",
                &self.admin_token.as_ref().map(|_| "<redacted>"),
            )
            .field("max_upload_bytes", &self.max_upload_bytes)
            .finish_non_exhaustive()
    }
}

/// Builder for [`Client`].
///
/// `Debug` is hand-written to redact bearer tokens.
#[derive(Default)]
pub struct ClientBuilder {
    base_url: Option<String>,
    app_token: Option<String>,
    admin_token: Option<String>,
    timeout: Option<Duration>,
    user_agent: Option<String>,
    danger_accept_invalid_certs: bool,
    max_upload_bytes: Option<u64>,
}

impl std::fmt::Debug for ClientBuilder {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_struct("ClientBuilder")
            .field("base_url", &self.base_url)
            .field("app_token", &self.app_token.as_ref().map(|_| "<redacted>"))
            .field(
                "admin_token",
                &self.admin_token.as_ref().map(|_| "<redacted>"),
            )
            .field("timeout", &self.timeout)
            .field("user_agent", &self.user_agent)
            .field(
                "danger_accept_invalid_certs",
                &self.danger_accept_invalid_certs,
            )
            .field("max_upload_bytes", &self.max_upload_bytes)
            .finish_non_exhaustive()
    }
}

impl Client {
    /// Start building a client.
    pub fn builder() -> ClientBuilder {
        ClientBuilder::default()
    }

    /// Base URL the client was configured with (trailing slash trimmed).
    pub fn base_url(&self) -> &str {
        self.base.as_str().trim_end_matches('/')
    }

    // ---- public API --------------------------------------------------------

    /// `GET /healthz`. Does not require an app token, but the server still
    /// enforces the global IP allowlist.
    pub async fn healthz(&self) -> Result<Healthz, Error> {
        let url = self.url("/healthz")?;
        let req = self.inner.request(Method::GET, url);
        // healthz works without a token, but if we have one, send it — the
        // server treats it as a no-op.
        let req = match &self.app_token {
            Some(t) => req.bearer_auth(t),
            None => req,
        };
        let resp = req.send().await?;
        json_or_error(resp).await
    }

    /// `POST /run`. Returns the parsed [`RunResult`] on success. On HTTP 502
    /// the body is surfaced as [`Error::Api`] with `status = 502` and the
    /// failure JSON in `body` — see [`crate::types::RunFailure`] for the
    /// structured form.
    pub async fn run(&self, body: RunRequest) -> Result<RunResult, Error> {
        let token = self
            .app_token
            .as_deref()
            .ok_or_else(|| Error::Auth("no app token configured".into()))?;
        let url = self.url("/run")?;
        let resp = self
            .inner
            .post(url)
            .bearer_auth(token)
            .json(&body)
            .send()
            .await?;
        json_or_error(resp).await
    }

    /// `POST /files`. Streams the file from disk via `tokio::fs::File`; large
    /// uploads do not buffer fully in memory.
    ///
    /// `ttl_secs` defaults to the server's 3600 if `None`. Server clamps to
    /// `60..=86400`.
    ///
    /// If [`ClientBuilder::max_upload_bytes`] was set and the file's size on
    /// disk exceeds it, returns [`Error::Config`] before opening any network
    /// connection.
    pub async fn upload_file(
        &self,
        path: impl AsRef<Path>,
        ttl_secs: Option<u32>,
    ) -> Result<FileToken, Error> {
        let token = self
            .app_token
            .as_deref()
            .ok_or_else(|| Error::Auth("no app token configured".into()))?;
        let path = path.as_ref();
        let file_name = path
            .file_name()
            .and_then(|n| n.to_str())
            .unwrap_or("upload")
            .to_string();

        let file = tokio::fs::File::open(path).await?;
        let len = file.metadata().await?.len();

        if let Some(max) = self.max_upload_bytes {
            if len > max {
                return Err(Error::Config(format!(
                    "file size {len} bytes exceeds max_upload_bytes={max}"
                )));
            }
        }

        let stream = ReaderStream::new(file);
        let body = Body::wrap_stream(stream);

        let part = Part::stream_with_length(body, len)
            .file_name(file_name)
            .mime_str("application/octet-stream")
            .map_err(|e| Error::Config(format!("invalid mime: {e}")))?;

        let mut form = Form::new().part("file", part);
        if let Some(t) = ttl_secs {
            form = form.text("ttl_secs", t.to_string());
        }

        let url = self.url("/files")?;
        let resp = self
            .inner
            .post(url)
            .bearer_auth(token)
            .multipart(form)
            .send()
            .await?;
        json_or_error(resp).await
    }

    /// `POST /admin/tokens`. Requires an admin token on the client.
    pub async fn create_token(&self, body: TokenCreateRequest) -> Result<AppToken, Error> {
        let token = self.require_admin()?;
        let url = self.url("/admin/tokens")?;
        let resp = self
            .inner
            .post(url)
            .bearer_auth(token)
            .json(&body)
            .send()
            .await?;
        json_or_error(resp).await
    }

    /// `GET /admin/tokens`. Requires an admin token on the client.
    pub async fn list_tokens(&self) -> Result<TokenList, Error> {
        let token = self.require_admin()?;
        let url = self.url("/admin/tokens")?;
        let resp = self.inner.get(url).bearer_auth(token).send().await?;
        json_or_error(resp).await
    }

    /// `DELETE /admin/tokens/{name}`. Requires an admin token on the client.
    /// Returns `Ok(())` on success, [`Error::Api`] with status 404 if the
    /// token does not exist.
    ///
    /// `name` is validated client-side to match the server's
    /// `[a-z0-9][a-z0-9_-]{0,63}` constraint — anything containing `/`, `?`,
    /// `#`, `..`, or empty short-circuits with [`Error::Config`] before a
    /// request is sent. This is defense-in-depth against path traversal via
    /// `Url::join` (which honors RFC 3986 `..` resolution).
    pub async fn revoke_token(&self, name: &str) -> Result<(), Error> {
        if name.is_empty()
            || name.contains('/')
            || name.contains('?')
            || name.contains('#')
            || name.contains("..")
        {
            return Err(Error::Config(format!("invalid token name: {name:?}")));
        }
        let token = self.require_admin()?;
        let url = self.url(&format!("/admin/tokens/{name}"))?;
        let resp = self.inner.delete(url).bearer_auth(token).send().await?;
        // 2xx is success regardless of body — RFC-correct DELETE may return
        // 204 No Content with no body.
        if resp.status().is_success() {
            return Ok(());
        }
        // Non-2xx: route through json_or_error to get Auth/Api mapping.
        // Discard the (already-non-success) deserialization slot.
        let _: serde_json::Value = json_or_error(resp).await?;
        Ok(())
    }

    // ---- v0.2 multi-turn / sessions ---------------------------------------

    /// `POST /sessions`. Create a new multi-turn session and return a
    /// [`Session`] handle bound to this client.
    ///
    /// The handle owns a clone of the client; dropping it without an explicit
    /// `Session::close().await?` triggers a best-effort async DELETE via
    /// `tokio::spawn`. See [`Session`] for the full lifecycle contract.
    pub async fn new_session(&self, opts: SessionOptions) -> Result<Session, Error> {
        let token = self.require_app()?;
        let url = self.url("/sessions")?;
        let resp = self
            .inner
            .post(url)
            .bearer_auth(token)
            .json(&opts)
            .send()
            .await?;
        let created: SessionCreateResponse = json_or_error(resp).await?;
        Ok(Session {
            client: self.clone(),
            session_id: created.session_id,
            agent: created.agent,
            created_at: created.created_at,
            closed: std::sync::atomic::AtomicBool::new(false),
        })
    }

    /// `GET /sessions`. List all sessions visible to the calling app token.
    pub async fn list_sessions(&self) -> Result<SessionList, Error> {
        let token = self.require_app()?;
        let url = self.url("/sessions")?;
        let resp = self.inner.get(url).bearer_auth(token).send().await?;
        json_or_error(resp).await
    }

    /// `GET /sessions/{id}`. Fetch the current state of a session.
    ///
    /// `id` is validated client-side against the same path-traversal guard as
    /// [`Self::revoke_token`] — anything containing `/`, `?`, `#`, `..`, or
    /// empty short-circuits with [`Error::Config`].
    pub async fn get_session(&self, id: &str) -> Result<SessionState, Error> {
        validate_session_id(id)?;
        let token = self.require_app()?;
        let url = self.url(&format!("/sessions/{id}"))?;
        let resp = self.inner.get(url).bearer_auth(token).send().await?;
        json_or_error(resp).await
    }

    /// Internal helper used by both [`Session::close`] and [`Session`]'s
    /// `Drop` impl to issue `DELETE /sessions/{id}`.
    pub(crate) async fn close_session_internal(&self, id: &str) -> Result<(), Error> {
        validate_session_id(id)?;
        let token = self.require_app()?;
        let url = self.url(&format!("/sessions/{id}"))?;
        let resp = self.inner.delete(url).bearer_auth(token).send().await?;
        if resp.status().is_success() {
            // Body is informational — `{ ok, already_closed? }`. Drain and
            // ignore decode failure (server may legitimately 204).
            let bytes = resp.bytes().await?;
            if !bytes.is_empty() {
                let _ = serde_json::from_slice::<SessionCloseResponse>(&bytes);
            }
            return Ok(());
        }
        // Funnel non-2xx through json_or_error for Auth/Api mapping.
        let _: serde_json::Value = json_or_error(resp).await?;
        Ok(())
    }

    /// Internal helper used by [`Session::turn`] /
    /// [`Session::turn_with_files`] to dispatch to
    /// `POST /sessions/{id}/turn`.
    pub(crate) async fn turn_internal<B: serde::Serialize>(
        &self,
        id: &str,
        body: &B,
    ) -> Result<TurnResult, Error> {
        validate_session_id(id)?;
        let token = self.require_app()?;
        let url = self.url(&format!("/sessions/{id}/turn"))?;
        let resp = self
            .inner
            .post(url)
            .bearer_auth(token)
            .json(body)
            .send()
            .await?;
        json_or_error(resp).await
    }

    // ---- internal ----------------------------------------------------------

    fn require_app(&self) -> Result<&str, Error> {
        self.app_token
            .as_deref()
            .ok_or_else(|| Error::Auth("no app token configured".into()))
    }

    fn require_admin(&self) -> Result<&str, Error> {
        self.admin_token
            .as_deref()
            .ok_or_else(|| Error::Auth("no admin token configured".into()))
    }

    fn url(&self, path: &str) -> Result<Url, Error> {
        let trimmed = path.strip_prefix('/').unwrap_or(path);
        self.base
            .join(trimmed)
            .map_err(|e| Error::Config(format!("bad path {path:?}: {e}")))
    }
}

impl ClientBuilder {
    /// Set the base URL (e.g. `http://localhost:8800`). Required.
    pub fn base_url(mut self, url: impl Into<String>) -> Self {
        self.base_url = Some(url.into());
        self
    }

    /// Set the app bearer token used for `/run`, `/files`, and `/healthz`.
    pub fn token(mut self, token: impl Into<String>) -> Self {
        self.app_token = Some(token.into());
        self
    }

    /// Set the admin bootstrap token used for `/admin/*`. May be set
    /// alongside [`Self::token`].
    pub fn admin_token(mut self, token: impl Into<String>) -> Self {
        self.admin_token = Some(token.into());
        self
    }

    /// Per-request timeout for the underlying `reqwest::Client`. Defaults to
    /// 120 s.
    pub fn timeout(mut self, timeout: Duration) -> Self {
        self.timeout = Some(timeout);
        self
    }

    /// Override the `User-Agent` header. Defaults to
    /// `clawdforge-rs/<crate-version>`.
    pub fn user_agent(mut self, ua: impl Into<String>) -> Self {
        self.user_agent = Some(ua.into());
        self
    }

    /// Skip TLS certificate verification. Off by default. Only useful against
    /// self-signed local deployments.
    pub fn danger_accept_invalid_certs(mut self, enable: bool) -> Self {
        self.danger_accept_invalid_certs = enable;
        self
    }

    /// Maximum file size (in bytes) accepted by [`Client::upload_file`].
    /// Files exceeding this cap fail with [`Error::Config`] before any
    /// network I/O. Default `None` = no client-side cap (the server's own
    /// limit still applies).
    pub fn max_upload_bytes(mut self, max: u64) -> Self {
        self.max_upload_bytes = Some(max);
        self
    }

    /// Finalize. Errors if `base_url` is missing or unparseable.
    pub fn build(self) -> Result<Client, Error> {
        let base_raw = self
            .base_url
            .ok_or_else(|| Error::Config("base_url is required".into()))?;
        // Ensure trailing slash so `Url::join` treats the base as a directory.
        let base_str = if base_raw.ends_with('/') {
            base_raw
        } else {
            format!("{base_raw}/")
        };
        let base =
            Url::parse(&base_str).map_err(|e| Error::Config(format!("invalid base_url: {e}")))?;
        if !matches!(base.scheme(), "http" | "https") {
            return Err(Error::Config(format!(
                "unsupported scheme: {}",
                base.scheme()
            )));
        }

        let ua = self
            .user_agent
            .unwrap_or_else(|| format!("clawdforge-rs/{}", env!("CARGO_PKG_VERSION")));

        let mut headers = HeaderMap::new();
        headers.insert(
            reqwest::header::ACCEPT,
            HeaderValue::from_static("application/json"),
        );
        // We don't preset Authorization here — per-call helpers do it because
        // the right token depends on which endpoint is being hit.

        let inner = reqwest::Client::builder()
            .timeout(self.timeout.unwrap_or(DEFAULT_TIMEOUT))
            .user_agent(ua)
            .default_headers(headers)
            .danger_accept_invalid_certs(self.danger_accept_invalid_certs)
            .build()?;

        Ok(Client {
            inner,
            base,
            app_token: self.app_token,
            admin_token: self.admin_token,
            max_upload_bytes: self.max_upload_bytes,
        })
    }
}

/// Decode `T` from a successful 2xx response, otherwise lift to [`Error`].
async fn json_or_error<T: DeserializeOwned>(resp: Response) -> Result<T, Error> {
    let status = resp.status();
    if status.is_success() {
        let bytes = resp.bytes().await?;
        return Ok(serde_json::from_slice::<T>(&bytes)?);
    }

    // Non-2xx: capture body lossily then translate.
    let body = resp.text().await.unwrap_or_default();
    match status {
        StatusCode::UNAUTHORIZED | StatusCode::FORBIDDEN => Err(Error::Auth(format!(
            "{}: {}",
            status.as_u16(),
            truncate(&body, 500)
        ))),
        _ => Err(Error::api(status.as_u16(), body)),
    }
}

/// Defense-in-depth path validator for session ids in `/sessions/{id}*`. Same
/// shape as [`Client::revoke_token`]'s name guard — RFC 3986 dot-segment
/// resolution inside `Url::join` is the threat model here.
fn validate_session_id(id: &str) -> Result<(), Error> {
    if id.is_empty()
        || id.contains('/')
        || id.contains('?')
        || id.contains('#')
        || id.contains("..")
    {
        return Err(Error::Config(format!("invalid session id: {id:?}")));
    }
    Ok(())
}

/// Truncate `s` to at most `max` bytes, snapping down to the nearest UTF-8
/// codepoint boundary so we never panic on multibyte sequences. Appends `…`
/// to the truncated form. `str::floor_char_boundary` (stable 1.80+) does the
/// boundary math.
fn truncate(s: &str, max: usize) -> String {
    if s.len() <= max {
        s.to_string()
    } else {
        let safe = s.floor_char_boundary(max);
        format!("{}…", &s[..safe])
    }
}