ai-usagebar 0.7.0

//! Stitches together: read creds → maybe-refresh → GET usage → cache result.
//!
//! Mirrors claudebar:402-491 — the lock + refresh + fetch state machine.

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

use chrono::Utc;

use crate::cache::{Cache, acquire_lock};
use crate::error::{AppError, Result};
use crate::usage::AnthropicSnapshot;

use super::creds::{self, OauthCreds};
use super::oauth;
use super::types::UsageResponse;

pub const USAGE_URL: &str = "https://api.anthropic.com/api/oauth/usage";
pub const USAGE_BETA_HEADER: &str = "oauth-2025-04-20";
const HTTP_TIMEOUT: Duration = Duration::from_secs(10);
const REFRESH_TIMEOUT: Duration = Duration::from_secs(25);
const LOCK_TIMEOUT: Duration = Duration::from_secs(45);

/// Endpoints (parameterized for tests).
#[derive(Debug, Clone)]
pub struct Endpoints {
    pub usage: String,
    pub token: String,
}

impl Default for Endpoints {
    fn default() -> Self {
        Self {
            usage: USAGE_URL.into(),
            token: oauth::TOKEN_URL.into(),
        }
    }
}

/// What we ultimately hand back to the renderer.
#[derive(Debug, Clone)]
pub struct FetchOutcome {
    pub snapshot: AnthropicSnapshot,
    /// True if this snapshot came from the on-disk cache because the live
    /// fetch failed — the widget shows a `⏸` indicator in this case.
    pub stale: bool,
    /// Last fetch error, if any — drives the `.last_error` tooltip line.
    pub last_error: Option<(u16, String)>,
    /// When the on-disk cache was written. Drives the "Updated HH:MM" line.
    pub cache_age: Option<Duration>,
}

/// High-level entry point. Reads creds, refreshes if needed, fetches usage,
/// writes back the cache, and returns the snapshot — falling back to cache on
/// failure. All under a flock so multi-monitor Waybar instances coexist.
pub async fn fetch_snapshot(
    client: &reqwest::Client,
    creds_path: &Path,
    cache: &Cache,
    endpoints: &Endpoints,
    cache_ttl: Duration,
) -> Result<FetchOutcome> {
    cache.ensure_dir()?;
    let _lock = acquire_lock(&cache.lock_path(), LOCK_TIMEOUT)?;

    // Fast path: cache is fresh, no work needed. We still need creds for the
    // plan label though, so read them either way.
    let mut creds = creds::read_from(creds_path)?;
    let plan_label = creds.claude_ai_oauth.plan_label();

    if let Some(bytes) = cache.fresh_payload(cache_ttl)? {
        return Ok(reuse_cache(bytes, plan_label, cache, false));
    }

    // Maybe refresh.
    let mut auth_ok = true;
    let mut refresh_transient = false;
    let now = Utc::now().timestamp();
    if oauth::needs_refresh(creds.claude_ai_oauth.expires_at_secs(), now) {
        match tokio::time::timeout(
            REFRESH_TIMEOUT,
            oauth::refresh(
                client,
                &endpoints.token,
                &creds.claude_ai_oauth.refresh_token,
            ),
        )
        .await
        {
            Ok(Ok(rr)) => {
                creds.claude_ai_oauth.access_token = rr.access_token;
                if let Some(new_rt) = rr.refresh_token {
                    creds.claude_ai_oauth.refresh_token = new_rt;
                }
                creds.claude_ai_oauth.expires_at_ms =
                    Utc::now().timestamp_millis() + (rr.expires_in as i64) * 1000;
                // Best-effort persist; the refresh worked, so callers should
                // still see fresh data even if writing the cred file failed.
                let _ = creds::write_back(creds_path, &creds.claude_ai_oauth);
            }
            Ok(Err(AppError::Http { status, body })) => {
                auth_ok = false;
                cache.write_last_error(status, &body);
            }
            Ok(Err(e)) if e.is_transient() => {
                auth_ok = false;
                refresh_transient = true;
            }
            Ok(Err(e)) => {
                auth_ok = false;
                cache.write_last_error(0, &e.to_string());
            }
            Err(_elapsed) => {
                auth_ok = false;
                refresh_transient = true;
            }
        }
    }

    if !auth_ok {
        return handle_auth_failure(cache, plan_label, refresh_transient);
    }

    // Fetch usage.
    match tokio::time::timeout(
        HTTP_TIMEOUT,
        fetch_usage(client, &endpoints.usage, &creds.claude_ai_oauth),
    )
    .await
    {
        Ok(Ok(bytes)) => {
            cache.write_payload(&bytes)?;
            let snap = parse_payload(&bytes, plan_label.clone())?;
            Ok(FetchOutcome {
                snapshot: snap,
                stale: false,
                last_error: None,
                cache_age: Some(Duration::ZERO),
            })
        }
        Ok(Err(AppError::Http { status, body })) => {
            cache.mark_stale();
            cache.write_last_error(status, &body);
            fallback_to_cache(cache, plan_label, Some((status, body)))
        }
        Ok(Err(e)) if e.is_transient() => {
            // Reuse cache silently; no last_error write.
            fallback_to_cache_silent(cache, plan_label)
        }
        Ok(Err(e)) => {
            cache.mark_stale();
            cache.write_last_error(0, &e.to_string());
            fallback_to_cache(cache, plan_label, Some((0, e.to_string())))
        }
        Err(_elapsed) => fallback_to_cache_silent(cache, plan_label),
    }
}

fn reuse_cache(bytes: Vec<u8>, plan_label: String, cache: &Cache, stale: bool) -> FetchOutcome {
    let snap =
        parse_payload(&bytes, plan_label).unwrap_or_else(|_| empty_snapshot("Unknown".into()));
    FetchOutcome {
        snapshot: snap,
        stale,
        last_error: cache.read_last_error(),
        cache_age: cache.payload_age(),
    }
}

fn fallback_to_cache(
    cache: &Cache,
    plan_label: String,
    last_error: Option<(u16, String)>,
) -> Result<FetchOutcome> {
    let Some(bytes) = cache.maybe_payload()? else {
        return Err(AppError::Other("no usable cache".into()));
    };
    let snap = parse_payload(&bytes, plan_label)?;
    Ok(FetchOutcome {
        snapshot: snap,
        stale: true,
        last_error,
        cache_age: cache.payload_age(),
    })
}

fn fallback_to_cache_silent(cache: &Cache, plan_label: String) -> Result<FetchOutcome> {
    let Some(bytes) = cache.maybe_payload()? else {
        return Err(AppError::Transport(
            "no cache and network unreachable".into(),
        ));
    };
    let snap = parse_payload(&bytes, plan_label)?;
    Ok(FetchOutcome {
        snapshot: snap,
        stale: true,
        last_error: cache.read_last_error(),
        cache_age: cache.payload_age(),
    })
}

fn handle_auth_failure(cache: &Cache, plan_label: String, transient: bool) -> Result<FetchOutcome> {
    let Some(bytes) = cache.maybe_payload()? else {
        return if transient {
            Err(AppError::Transport(
                "no cache and refresh failed transiently".into(),
            ))
        } else {
            Err(AppError::Credentials(
                "token refresh failed; run `claude` to re-auth".into(),
            ))
        };
    };
    let snap = parse_payload(&bytes, plan_label)?;
    Ok(FetchOutcome {
        snapshot: snap,
        stale: true,
        last_error: cache.read_last_error(),
        cache_age: cache.payload_age(),
    })
}

fn parse_payload(bytes: &[u8], plan_label: String) -> Result<AnthropicSnapshot> {
    let resp: UsageResponse = serde_json::from_slice(bytes)?;
    Ok(resp.into_snapshot(plan_label))
}

fn empty_snapshot(plan_label: String) -> AnthropicSnapshot {
    UsageResponse::default().into_snapshot(plan_label)
}

async fn fetch_usage(client: &reqwest::Client, url: &str, creds: &OauthCreds) -> Result<Vec<u8>> {
    let resp = client
        .get(url)
        .header("Authorization", format!("Bearer {}", creds.access_token))
        .header("anthropic-beta", USAGE_BETA_HEADER)
        .send()
        .await?;

    let status = resp.status();
    let bytes = resp.bytes().await?;

    if status.is_success() {
        // Validate it's a usage shape — keep claudebar's "must have five_hour"
        // sanity check (claudebar:385).
        let _: UsageResponse = serde_json::from_slice(&bytes)
            .map_err(|e| AppError::Schema(format!("usage response unparseable: {e}")))?;
        Ok(bytes.to_vec())
    } else {
        let body = String::from_utf8_lossy(&bytes).into_owned();
        let msg =
            oauth::parse_error_body(&body).unwrap_or_else(|| body.chars().take(200).collect());
        Err(AppError::Http {
            status: status.as_u16(),
            body: msg,
        })
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::io::Write;
    use tempfile::{NamedTempFile, TempDir};

    fn future_creds() -> NamedTempFile {
        let mut f = NamedTempFile::new().unwrap();
        // Expires 1 hour from now → no refresh needed in tests.
        let expires_ms = (Utc::now().timestamp_millis()) + 3_600_000;
        let s = format!(
            r#"{{"claudeAiOauth":{{
                "accessToken":"AT","refreshToken":"RT",
                "expiresAt": {expires_ms},
                "subscriptionType":"max","rateLimitTier":"default_claude_max_5x"
            }}}}"#
        );
        f.write_all(s.as_bytes()).unwrap();
        f.flush().unwrap();
        f
    }

    fn cache_fixture() -> (TempDir, Cache) {
        let td = TempDir::new().unwrap();
        let cache = Cache::at(td.path().join("anthropic"));
        cache.ensure_dir().unwrap();
        (td, cache)
    }

    #[tokio::test]
    async fn fresh_cache_skips_network() {
        let (_td, cache) = cache_fixture();
        cache
            .write_payload(
                br#"{"five_hour":{"utilization":42,"resets_at":"2026-05-23T17:30:00Z"},
                     "seven_day":{"utilization":15,"resets_at":"2026-05-30T12:00:00Z"}}"#,
            )
            .unwrap();

        let creds = future_creds();
        let client = reqwest::Client::new();
        let endpoints = Endpoints {
            usage: "http://localhost:1/should-not-be-called".into(),
            token: "http://localhost:1/should-not-be-called".into(),
        };
        let outcome = fetch_snapshot(
            &client,
            creds.path(),
            &cache,
            &endpoints,
            Duration::from_secs(60),
        )
        .await
        .unwrap();
        assert_eq!(outcome.snapshot.session.utilization_pct, 42);
        assert!(!outcome.stale);
    }

    #[tokio::test]
    async fn live_fetch_writes_cache_and_returns_snapshot() {
        let mut server = mockito::Server::new_async().await;
        let m = server
            .mock("GET", "/api/oauth/usage")
            .with_status(200)
            .with_body(
                r#"{"five_hour":{"utilization":50,"resets_at":"2026-05-23T17:30:00Z"},
                    "seven_day":{"utilization":25,"resets_at":"2026-05-30T12:00:00Z"}}"#,
            )
            .create_async()
            .await;

        let (_td, cache) = cache_fixture();
        let creds = future_creds();
        let client = reqwest::Client::new();
        let endpoints = Endpoints {
            usage: format!("{}/api/oauth/usage", server.url()),
            token: format!("{}/v1/oauth/token", server.url()),
        };
        let outcome = fetch_snapshot(
            &client,
            creds.path(),
            &cache,
            &endpoints,
            Duration::from_secs(0),
        )
        .await
        .unwrap();
        assert_eq!(outcome.snapshot.session.utilization_pct, 50);
        assert!(!outcome.stale);
        m.assert_async().await;
        // Cache should now exist.
        assert!(cache.maybe_payload().unwrap().is_some());
    }

    #[tokio::test]
    async fn http_429_falls_back_to_stale_cache() {
        let mut server = mockito::Server::new_async().await;
        server
            .mock("GET", "/api/oauth/usage")
            .with_status(429)
            .with_body(r#"{"error":{"type":"rate_limit_error","message":"slow down"}}"#)
            .create_async()
            .await;

        let (_td, cache) = cache_fixture();
        cache
            .write_payload(
                br#"{"five_hour":{"utilization":12,"resets_at":"2026-05-23T17:30:00Z"},
                     "seven_day":{"utilization":5,"resets_at":"2026-05-30T12:00:00Z"}}"#,
            )
            .unwrap();
        // Force the cache to be considered stale by setting TTL = 0.
        let creds = future_creds();
        let client = reqwest::Client::new();
        let endpoints = Endpoints {
            usage: format!("{}/api/oauth/usage", server.url()),
            token: format!("{}/v1/oauth/token", server.url()),
        };
        let outcome = fetch_snapshot(
            &client,
            creds.path(),
            &cache,
            &endpoints,
            Duration::from_secs(0),
        )
        .await
        .unwrap();
        assert!(outcome.stale);
        assert_eq!(outcome.snapshot.session.utilization_pct, 12);
        assert_eq!(outcome.last_error.as_ref().map(|(c, _)| *c), Some(429));
        assert_eq!(
            outcome.last_error.as_ref().map(|(_, m)| m.as_str()),
            Some("slow down")
        );
    }

    #[tokio::test]
    async fn no_cache_and_no_network_returns_error() {
        // Point at a closed port so we get a transport error.
        let (_td, cache) = cache_fixture();
        let creds = future_creds();
        let client = reqwest::Client::builder()
            .timeout(Duration::from_millis(200))
            .build()
            .unwrap();
        let endpoints = Endpoints {
            usage: "http://127.0.0.1:1/api/oauth/usage".into(),
            token: "http://127.0.0.1:1/v1/oauth/token".into(),
        };
        let err = fetch_snapshot(
            &client,
            creds.path(),
            &cache,
            &endpoints,
            Duration::from_secs(0),
        )
        .await
        .unwrap_err();
        assert!(err.is_transient(), "expected transient error, got {err:?}");
    }
}