gfeh-http 0.1.1

//! The suite this view must satisfy over every store it can be given.
//!
//! # Why this is a library module rather than a test target
//!
//! A view is written against [`ObjectStore`] and cannot tell which store it has. That
//! substitutability is the design, and it is the thing most likely to quietly stop being
//! true -- a header derived from a field one backend populates and another leaves empty
//! looks correct in every test written against the first.
//!
//! So the behaviour is asserted once, here, and every backend the crate can be driven
//! with runs the identical cases: the in-memory reference, a real filesystem partition,
//! and the composed namespace a daemon actually serves from. A backend that answers
//! differently fails the same case the reference passes.
//!
//! It is a library module for the same reason `gfeh-store`'s is: a test target can only
//! be run by this crate, and the point is that *other* crates -- a daemon, an
//! integration suite, a future backend -- can run the same cases against a store this
//! crate has never heard of.
//!
//! # It speaks HTTP
//!
//! Every case here issues a real request over a real socket against a real listener.
//! Calling the handlers directly would test the same code with the parts that have
//! actually been wrong -- header formats, status codes, the exact bytes of a
//! `Content-Range` -- removed from the loop.
//!
//! # Running it
//!
//! Implement [`Backend`] and hand it to [`run`]. Each case gets its own store, its own
//! listener, and its own exposure table.
//!
//! ```text
//! struct Mem;
//!
//! #[async_trait::async_trait]
//! impl Backend for Mem {
//!     fn name(&self) -> String { "MemStore".into() }
//!     async fn fresh(&self) -> Result<Target> {
//!         let store = gfeh_store::MemStore::new();
//!         Ok(Target { root: store.root(), partition: store.partition(), store: Arc::new(store) })
//!     }
//! }
//!
//! let report = conformance::run(&Mem).await;
//! assert!(report.is_conformant(), "{}", report.summary());
//! ```
//!
//! There is deliberately no built-in backend here. This crate depends on `gfeh-core` and
//! nothing else -- naming `MemStore` would mean depending on `gfeh-store`, which is the
//! one thing a protocol crate may not do, and a stub store written here to avoid that
//! would be a second in-memory implementation for the suite to quietly agree with.

use async_trait::async_trait;
use futures::future::BoxFuture;
use gfeh_core::{Disposition, Error, NodeKind, NodeRef, ObjectStore, OpCtx, PartitionId, Result};
use std::fmt::Debug;
use std::future::Future;
use std::sync::Arc;

use crate::{Exposed, Exposures, HttpView, StaticExposures};

// ---------------------------------------------------------------------------
// The backend under test
// ---------------------------------------------------------------------------

/// A store to run one case against.
pub struct Target {
    /// The store the view is served over.
    pub store: Arc<dyn ObjectStore>,
    /// A reference to the partition root.
    pub root: NodeRef,
    /// The partition the store serves.
    pub partition: PartitionId,
}

/// A factory for stores under test.
#[async_trait]
pub trait Backend: Send + Sync {
    /// The backend's name, used in the report.
    fn name(&self) -> String;

    /// A store containing nothing but an empty root directory.
    ///
    /// # Errors
    ///
    /// Returns whatever the backend's own provisioning fails with. A failure here is
    /// reported against the case that asked for it rather than aborting the run.
    async fn fresh(&self) -> Result<Target>;
}

// ---------------------------------------------------------------------------
// A served view, and the client that drives it
// ---------------------------------------------------------------------------

/// One case's view, its exposure table, and a client pointed at it.
pub struct Served {
    view: HttpView,
    exposures: Arc<StaticExposures>,
    target: Target,
    client: reqwest::Client,
}

impl Served {
    async fn start(target: Target) -> Result<Self> {
        let exposures = Arc::new(StaticExposures::new());
        let view = HttpView::builder(
            Arc::clone(&target.store),
            Arc::clone(&exposures) as Arc<dyn Exposures>,
        )
        .start()
        .await
        .map_err(|e| Error::Storage(format!("binding the view: {e}")))?;
        Ok(Self {
            view,
            exposures,
            target,
            client: reqwest::Client::new(),
        })
    }

    /// Write a file into the store and publish it under a token.
    async fn publish(&self, name: &str, body: &[u8], token: &str) -> Result<()> {
        let cx = OpCtx::system("conformance");
        let mut handle = self
            .target
            .store
            .create(
                &cx,
                &self.target.root,
                name,
                NodeKind::File,
                Disposition::CreateNew,
            )
            .await?;
        if !body.is_empty() {
            handle
                .write_at(0, bytes::Bytes::copy_from_slice(body))
                .await?;
        }
        let meta = handle.close().await?;

        self.exposures.publish(
            token,
            Exposed {
                node: NodeRef::Id(self.target.partition, meta.id),
                filename: None,
                enabled: true,
            },
        );
        Ok(())
    }

    /// One GET, with optional headers.
    async fn get(&self, token: &str, headers: &[(&str, &str)]) -> Result<reqwest::Response> {
        let mut request = self.client.get(self.view.url_for(token));
        for (name, value) in headers {
            request = request.header(*name, *value);
        }
        request
            .send()
            .await
            .map_err(|e| Error::Storage(format!("request: {e}")))
    }
}

// ---------------------------------------------------------------------------
// Cases and the runner
// ---------------------------------------------------------------------------

/// A single behaviour the view must exhibit.
pub struct Case {
    name: &'static str,
    body: Box<dyn Fn(Served) -> BoxFuture<'static, Result<()>> + Send + Sync>,
}

impl Case {
    fn new<F, Fut>(name: &'static str, body: F) -> Self
    where
        F: Fn(Served) -> Fut + Send + Sync + 'static,
        Fut: Future<Output = Result<()>> + Send + 'static,
    {
        Self {
            name,
            body: Box::new(move |served| Box::pin(body(served))),
        }
    }

    /// What this case is called. Stable, so a failure can be looked up.
    #[must_use]
    pub fn name(&self) -> &'static str {
        self.name
    }
}

impl Debug for Case {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_struct("Case").field("name", &self.name).finish()
    }
}

/// What one case did.
#[derive(Debug, Clone)]
pub struct Outcome {
    /// The case's name.
    pub case: &'static str,
    /// The failure, or `None` if it passed.
    pub failure: Option<String>,
}

/// The result of running the suite against one backend.
#[derive(Debug, Clone)]
pub struct Report {
    /// Which backend was tested.
    pub backend: String,
    /// One outcome per case, in suite order.
    pub outcomes: Vec<Outcome>,
}

impl Report {
    /// True when every case passed.
    #[must_use]
    pub fn is_conformant(&self) -> bool {
        self.outcomes.iter().all(|o| o.failure.is_none())
    }

    /// How many cases passed.
    #[must_use]
    pub fn passed(&self) -> usize {
        self.outcomes.iter().filter(|o| o.failure.is_none()).count()
    }

    /// The cases that failed.
    pub fn failures(&self) -> impl Iterator<Item = &Outcome> {
        self.outcomes.iter().filter(|o| o.failure.is_some())
    }

    /// A human-readable summary listing every failure.
    #[must_use]
    pub fn summary(&self) -> String {
        let mut out = format!(
            "{}: {}/{} conformance cases passed",
            self.backend,
            self.passed(),
            self.outcomes.len()
        );
        for outcome in self.failures() {
            let reason = outcome.failure.as_deref().unwrap_or("unknown");
            out.push_str(&format!("\n  FAIL {}: {reason}", outcome.case));
        }
        out
    }
}

/// Run every case against a backend, collecting all outcomes.
///
/// Never stops early: one broken assumption usually surfaces as several failing cases,
/// and the set of them is what identifies it.
pub async fn run<B: Backend>(backend: &B) -> Report {
    let mut outcomes = Vec::new();
    for case in cases() {
        let failure = match backend.fresh().await {
            Ok(target) => match Served::start(target).await {
                Ok(served) => (case.body)(served).await.err().map(|e| e.to_string()),
                Err(e) => Some(format!("the view could not be served: {e}")),
            },
            Err(e) => Some(format!("backend could not provide a fresh store: {e}")),
        };
        outcomes.push(Outcome {
            case: case.name(),
            failure,
        });
    }
    Report {
        backend: backend.name(),
        outcomes,
    }
}

/// Fail the case unless `condition` holds.
fn ensure(condition: bool, message: impl Into<String>) -> Result<()> {
    if condition {
        Ok(())
    } else {
        Err(Error::Other(message.into()))
    }
}

/// Fail the case unless two values are equal, reporting both.
fn ensure_eq<T: PartialEq + Debug>(actual: T, expected: T, what: &str) -> Result<()> {
    ensure(
        actual == expected,
        format!("{what}: expected {expected:?}, got {actual:?}"),
    )
}

/// One header, as a string.
fn header(response: &reqwest::Response, name: &str) -> Option<String> {
    response
        .headers()
        .get(name)
        .and_then(|v| v.to_str().ok())
        .map(str::to_string)
}

/// Every case in the suite.
#[must_use]
pub fn cases() -> Vec<Case> {
    vec![
        Case::new("a_published_file_is_served_whole", |s| async move {
            s.publish("report.pdf", b"%PDF-1.7 body", "tok").await?;
            let response = s.get("tok", &[]).await?;
            ensure_eq(response.status().as_u16(), 200, "status")?;
            ensure_eq(
                header(&response, "content-length"),
                Some("13".into()),
                "content-length",
            )?;
            let body = response.text().await.unwrap_or_default();
            ensure_eq(body, "%PDF-1.7 body".to_string(), "body")
        }),
        Case::new("an_unknown_token_is_not_found", |s| async move {
            ensure_eq(s.get("nope", &[]).await?.status().as_u16(), 404, "status")
        }),
        Case::new(
            "a_disabled_link_is_indistinguishable_from_an_unknown_one",
            |s| async move {
                // Telling the holder that the token is real but switched off is information
                // they should not have.
                s.publish("report.pdf", b"body", "tok").await?;
                s.exposures.publish(
                    "tok",
                    Exposed {
                        enabled: false,
                        ..s.exposures.resolve("tok").unwrap_or(Exposed {
                            node: s.target.root.clone(),
                            filename: None,
                            enabled: false,
                        })
                    },
                );
                let disabled = s.get("tok", &[]).await?;
                let unknown = s.get("nope", &[]).await?;
                ensure_eq(disabled.status(), unknown.status(), "status")
            },
        ),
        Case::new("last_modified_is_an_http_date", |s| async move {
            // ISO 8601 here made an S3 object visible in a listing and unreadable by the
            // AWS SDK for Go. An HTTP-date ends in `GMT` and has no `T` separator.
            s.publish("report.pdf", b"body", "tok").await?;
            let response = s.get("tok", &[]).await?;
            let value = header(&response, "last-modified")
                .ok_or_else(|| Error::Other("no Last-Modified header".into()))?;
            // `Thu, 01 Jan 1970 00:00:00 GMT`: a day name, a comma, and GMT at the end.
            // ISO 8601 is `1970-01-01T00:00:00Z`, so the hyphen is what tells them apart
            // -- checking for a `T` would reject `Thu` and `Tue`.
            ensure(value.ends_with(" GMT"), format!("Last-Modified: {value}"))?;
            ensure(value.contains(", "), format!("Last-Modified: {value}"))?;
            ensure(!value.contains('-'), format!("Last-Modified: {value}"))
        }),
        Case::new(
            "an_etag_answers_a_conditional_request_without_the_bytes",
            |s| async move {
                s.publish("report.pdf", b"body", "tok").await?;
                let first = s.get("tok", &[]).await?;
                let etag =
                    header(&first, "etag").ok_or_else(|| Error::Other("no ETag header".into()))?;

                let second = s.get("tok", &[("If-None-Match", &etag)]).await?;
                ensure_eq(second.status().as_u16(), 304, "status")?;
                ensure_eq(
                    second.text().await.unwrap_or_default(),
                    String::new(),
                    "a 304 carried a body",
                )
            },
        ),
        Case::new(
            "a_date_answers_a_conditional_request_without_the_bytes",
            |s| async move {
                // The weaker of the two validators and the one a browser sends without
                // being given anything: it echoes back the `Last-Modified` it was told.
                // A server that ignores it re-sends the whole object on every poll.
                s.publish("report.pdf", b"body", "tok").await?;
                let first = s.get("tok", &[]).await?;
                let modified = header(&first, "last-modified")
                    .ok_or_else(|| Error::Other("no Last-Modified header".into()))?;

                let second = s.get("tok", &[("If-Modified-Since", &modified)]).await?;
                ensure_eq(second.status().as_u16(), 304, "status")?;
                ensure_eq(
                    second.text().await.unwrap_or_default(),
                    String::new(),
                    "a 304 carried a body",
                )?;

                // A date before the object's own is not a match, and the object comes
                // back. This is the direction that matters: getting it wrong hands a
                // client a 304 for a file it has never seen.
                //
                // The date is before the epoch, which looks arbitrary and is not. An
                // HTTP-date has one-second resolution, and the in-memory reference dates
                // everything from a counter starting at zero -- deliberately, so a
                // protocol test can assert on a timestamp at all -- so every object it
                // holds falls in the same second as the epoch. The only date older than
                // every object on every backend is one before it. That the reference
                // cannot distinguish two of its own writes by date is the whole reason
                // an entity tag is the better validator.
                let stale = s
                    .get(
                        "tok",
                        &[("If-Modified-Since", "Wed, 31 Dec 1969 00:00:00 GMT")],
                    )
                    .await?;
                ensure_eq(stale.status().as_u16(), 200, "status for an older date")
            },
        ),
        Case::new(
            "an_unparseable_date_is_answered_with_the_object",
            |s| async move {
                // ISO 8601 is not an HTTP-date. A server that guessed at it would be
                // deciding whether to send a file on the strength of a string it did not
                // understand, and the failure mode is a client stuck on a stale copy --
                // where answering with the object costs one re-download.
                s.publish("report.pdf", b"body", "tok").await?;
                for value in ["2023-11-14T22:13:20Z", "yesterday", ""] {
                    let response = s.get("tok", &[("If-Modified-Since", value)]).await?;
                    ensure_eq(
                        response.status().as_u16(),
                        200,
                        &format!("status for {value:?}"),
                    )?;
                }
                Ok(())
            },
        ),
        Case::new(
            "an_entity_tag_is_believed_over_a_date_when_both_are_sent",
            |s| async move {
                // Required rather than preferred: a recipient that evaluates an entity
                // tag must ignore the date. The reason is the resolution -- two writes
                // inside one second share a `Last-Modified`, so a client holding the
                // first would be told it is current, where the tag knows better.
                s.publish("report.pdf", b"body", "tok").await?;
                let first = s.get("tok", &[]).await?;
                let modified = header(&first, "last-modified")
                    .ok_or_else(|| Error::Other("no Last-Modified header".into()))?;

                let response = s
                    .get(
                        "tok",
                        &[
                            ("If-None-Match", "\"not-the-tag\""),
                            ("If-Modified-Since", &modified),
                        ],
                    )
                    .await?;
                ensure_eq(
                    response.status().as_u16(),
                    200,
                    "a stale tag with a current date must send the object",
                )
            },
        ),
        Case::new("a_range_serves_the_bytes_it_asked_for", |s| async move {
            s.publish("report.pdf", b"0123456789", "tok").await?;
            let response = s.get("tok", &[("Range", "bytes=2-5")]).await?;
            ensure_eq(response.status().as_u16(), 206, "status")?;
            ensure_eq(
                header(&response, "content-range"),
                Some("bytes 2-5/10".into()),
                "content-range",
            )?;
            ensure_eq(
                response.text().await.unwrap_or_default(),
                "2345".to_string(),
                "body",
            )
        }),
        Case::new(
            "a_suffix_range_serves_the_end_of_the_file",
            |s| async move {
                // `bytes=-3` is the *last* three bytes. Reading it as "from byte 3" hands a
                // video player the opening credits when it asked for the index at the end.
                s.publish("report.pdf", b"0123456789", "tok").await?;
                let response = s.get("tok", &[("Range", "bytes=-3")]).await?;
                ensure_eq(response.status().as_u16(), 206, "status")?;
                ensure_eq(
                    response.text().await.unwrap_or_default(),
                    "789".to_string(),
                    "body",
                )
            },
        ),
        Case::new("an_open_ended_range_runs_to_the_end", |s| async move {
            s.publish("report.pdf", b"0123456789", "tok").await?;
            let response = s.get("tok", &[("Range", "bytes=7-")]).await?;
            ensure_eq(response.status().as_u16(), 206, "status")?;
            ensure_eq(
                response.text().await.unwrap_or_default(),
                "789".to_string(),
                "body",
            )
        }),
        Case::new(
            "a_range_past_the_end_says_how_much_there_is",
            |s| async move {
                // A 416 without `Content-Range: bytes */len` leaves a client with no way to
                // learn what it should have asked for.
                s.publish("report.pdf", b"0123456789", "tok").await?;
                let response = s.get("tok", &[("Range", "bytes=50-60")]).await?;
                ensure_eq(response.status().as_u16(), 416, "status")?;
                ensure_eq(
                    header(&response, "content-range"),
                    Some("bytes */10".into()),
                    "content-range",
                )
            },
        ),
        Case::new("an_empty_file_is_served_as_an_empty_body", |s| async move {
            s.publish("empty.txt", b"", "tok").await?;
            let response = s.get("tok", &[]).await?;
            ensure_eq(response.status().as_u16(), 200, "status")?;
            ensure_eq(
                header(&response, "content-length"),
                Some("0".into()),
                "content-length",
            )
        }),
        Case::new(
            "a_content_disposition_carries_the_advertised_name",
            |s| async move {
                s.publish("report.pdf", b"body", "tok").await?;
                let response = s.get("tok", &[]).await?;
                let value = header(&response, "content-disposition")
                    .ok_or_else(|| Error::Other("no Content-Disposition header".into()))?;
                ensure(
                    value.contains("report.pdf"),
                    format!("Content-Disposition: {value}"),
                )
            },
        ),
        Case::new("a_filename_cannot_inject_a_header", |s| async move {
            // A name is user-controlled, so an injection here would be one in every
            // response the view ever sends.
            s.publish("ordinary.txt", b"body", "tok").await?;
            let exposed = s
                .exposures
                .resolve("tok")
                .ok_or_else(|| Error::Other("the token vanished".into()))?;
            s.exposures.publish(
                "tok",
                Exposed {
                    filename: Some("a\r\nX-Injected: yes\r\n.txt".into()),
                    ..exposed
                },
            );

            let response = s.get("tok", &[]).await?;
            ensure(
                response.headers().get("x-injected").is_none(),
                "a filename injected a header",
            )
        }),
        Case::new(
            "a_link_survives_a_rename_of_the_file_it_names",
            |s| async move {
                // The token resolves an identity, not a path. A rename that broke a URL
                // already in circulation is the failure the whole design avoids.
                s.publish("before.pdf", b"body", "tok").await?;
                let exposed = s
                    .exposures
                    .resolve("tok")
                    .ok_or_else(|| Error::Other("the token vanished".into()))?;
                s.target
                    .store
                    .rename(
                        &OpCtx::system("conformance"),
                        &exposed.node,
                        &s.target.root,
                        "after.pdf",
                        false,
                    )
                    .await?;

                let response = s.get("tok", &[]).await?;
                ensure_eq(response.status().as_u16(), 200, "status after a rename")
            },
        ),
        Case::new(
            "a_head_answers_the_headers_without_the_body",
            |s| async move {
                s.publish("report.pdf", b"0123456789", "tok").await?;
                let response = s
                    .client
                    .head(s.view.url_for("tok"))
                    .send()
                    .await
                    .map_err(|e| Error::Storage(format!("request: {e}")))?;
                ensure_eq(response.status().as_u16(), 200, "status")?;
                ensure_eq(
                    header(&response, "content-length"),
                    Some("10".into()),
                    "content-length",
                )?;
                ensure_eq(
                    response.text().await.unwrap_or_default(),
                    String::new(),
                    "a HEAD carried a body",
                )
            },
        ),
        Case::new("nothing_but_a_token_names_a_file", |s| async move {
            // No directory listing, no path surface, and no way to name an object except
            // by a token somebody deliberately minted.
            s.publish("report.pdf", b"body", "tok").await?;
            // Traversal *inside* a token is not in this list: an HTTP client resolves
            // `..` before the request leaves it, so `/f/tok/../tok` never reaches the
            // server as anything but `/f/tok`. What is checked here is the surface --
            // that no path other than `/f/{token}` is served at all.
            for path in ["/", "/f/", "/f/../report.pdf", "/report.pdf", "/health"] {
                let response = s
                    .client
                    .get(format!("{}{path}", s.view.base_url()))
                    .send()
                    .await
                    .map_err(|e| Error::Storage(format!("request: {e}")))?;
                ensure(
                    !response.status().is_success(),
                    format!("{path} was served with {}", response.status()),
                )?;
            }
            Ok(())
        }),
    ]
}