onevcs-testing 0.10.0

//! The remote-host side: one implementation of [`RemoteHost`] and [`Hosting`] over
//! either store.
//!
//! What GitHub decides, this decides from what it was seeded with: which change
//! requests exist, what their checks say, and whether a merge lands. What it does
//! *not* do is move a commit — a merge here records an outcome and nothing reaches
//! any origin, which is exactly the boundary the real implementation delegates to
//! the host and the reason a journey about git drives real git.

use std::path::PathBuf;

use url::Url;

use onevcs::{
    ArtifactId, ChangeChecks, ChangeId, ChangeRequest, ChangeSpec, Check, CheckSource, CheckState,
    Description, Error, Hosting, MergeOutcome, MergePolicy, RemoteHost, RequiredChecks, Result,
    Sha,
};

use crate::events;
use crate::state::{Described, HostState};
use crate::store::{FileStore, MemoryStore, Store};

/// The host a change request's URL names, matching the one implementation the
/// crate next door speaks for.
pub const DEFAULT_HOST: &str = "github.com";

/// The repository a host answers for when it was not addressed at one — which is
/// the case only when a journey holds it directly rather than through
/// [`Hosting::for_repo`].
pub const DEFAULT_SLUG: &str = "onevcs/testing";

/// The remote-host side of a run, over whichever store holds its state.
///
/// It is both interfaces at once: a [`RemoteHost`] a journey can call directly, and
/// the [`Hosting`] factory a run is handed. A host taken from the factory shares
/// this one's state, so what a publication did is read back through the value the
/// journey created.
#[derive(Debug)]
pub struct Host<T> {
    store: T,
    // A slug arrives one way only — `Hosting::for_repo`, which takes the `&str` the
    // contract fixes — and `named_repository` refuses it there; every other
    // construction here is `DEFAULT_SLUG`. A newtype would have to be public to be
    // the parameter's type, and the seam is specified without one, which is the same
    // reason recorded on `Hosting::for_repo` in the crate next door.
    // llmlint: ignore[invalid_states_unrepresentable] see the note directly above.
    slug: String,
}

/// A host provider that keeps its state in this process.
pub type MemoryHost = Host<MemoryStore<HostState>>;

/// A host provider that keeps its state in one JSON document, so several `onevcs`
/// invocations see one another's change requests.
pub type FileHost = Host<FileStore<HostState>>;

impl MemoryHost {
    /// A host with nothing opened against it.
    pub fn new() -> Self {
        Self::seeded(HostState::default())
    }

    /// A host that starts from a scenario.
    pub fn seeded(state: HostState) -> Self {
        Self {
            store: MemoryStore::new(state),
            slug: DEFAULT_SLUG.to_owned(),
        }
    }

    /// Everything it knows.
    pub fn state(&self) -> HostState {
        self.store
            .snapshot()
            .expect("an in-memory store always answers")
    }
}

impl Default for MemoryHost {
    fn default() -> Self {
        Self::new()
    }
}

impl FileHost {
    /// A host keeping its state at `path`: whatever is already there, or nothing
    /// opened against it.
    ///
    /// Attaching rather than replacing, so a second host over the same path answers
    /// about the change requests the first one opened.
    pub fn create(path: impl Into<PathBuf>) -> Result<Self> {
        Ok(Self {
            store: FileStore::attach(path, &HostState::default())?,
            slug: DEFAULT_SLUG.to_owned(),
        })
    }

    /// A host that starts from a scenario, keeping its state at `path` and
    /// replacing whatever was there.
    pub fn seeded(path: impl Into<PathBuf>, state: HostState) -> Result<Self> {
        Ok(Self {
            store: FileStore::replace(path, &state)?,
            slug: DEFAULT_SLUG.to_owned(),
        })
    }

    /// Everything it knows, read back out of its document.
    pub fn state(&self) -> Result<HostState> {
        self.store.snapshot()
    }
}

impl<T: Store<HostState> + Clone + std::fmt::Debug + Send + Sync + 'static> Hosting for Host<T> {
    fn for_repo(&self, slug: &str) -> Result<Box<dyn RemoteHost>> {
        Ok(Box::new(Host {
            store: self.store.clone(),
            slug: named_repository(slug)?,
        }))
    }
}

impl<T: Store<HostState>> RemoteHost for Host<T> {
    fn authenticated_user(&self) -> Result<String> {
        let login = self.store.snapshot()?.authenticated_user;
        if login.trim().is_empty() {
            return Err(Error::Invalid {
                reason: "the host reported no authenticated user".to_owned(),
            });
        }
        Ok(login)
    }

    fn open_change(&self, req: ChangeSpec) -> Result<ChangeRequest> {
        addressable(&req.head, "the head branch")?;
        addressable(&req.base, "the base branch")?;
        // The same refusal the real host makes: a change request whose title names
        // nothing is one it will not open.
        crate::state::titled(&req.title)?;
        // The publication rule the crate next door states, applied rather than
        // restated — and applied *here* rather than only where a publication takes a
        // request in, because this trait is reachable directly: a journey that holds a
        // host and opens a change on it hands this the reason, and a reason nothing
        // could render is one the state must not go on to answer from.
        if let Some(reason) = &req.draft {
            reason.checked()?;
        }
        let slug = self.slug.clone();
        self.store.with(|state| {
            // The host numbers its change requests, consecutively from one, so a
            // journey can seed the checks of a change it has not opened yet.
            let id = ChangeId((state.changes.len() + 1).to_string());
            let url = format!("https://{DEFAULT_HOST}/{slug}/pull/{}", id.0);
            let change = ChangeRequest {
                head_sha: Sha(events::stable_sha(&[&slug, &req.head, &id.0])),
                url: Url::parse(&url).map_err(|e| Error::Invalid {
                    reason: format!("{url:?} is not a URL: {e}"),
                })?,
                base: req.base.clone(),
                id: id.clone(),
            };
            state.heads.insert(id.clone(), req.head.clone());
            state.titles.insert(id.clone(), req.title.clone());
            // Only when there is one: a change request opened with no body records
            // none, so a journey can tell "nobody drafted one" from "the body is
            // empty" — which is the distinction the real host draws too.
            if let Some(body) = req.body.clone() {
                state.bodies.insert(id.clone(), body);
            }
            // Beside the body and for its reason: a change request opened as a draft
            // records the reason it was drafted with, and one opened without a reason
            // records nothing — which is how a journey tells a draft from an ordinary
            // change request rather than from a flag nobody kept.
            if let Some(reason) = req.draft.clone() {
                state.drafts.insert(id, reason);
            } else if req.draft_awaiting_checks {
                // The lifecycle's own draft, which carries no reason: recorded apart
                // from the reasons a caller gave, so a journey can tell the two apart.
                state.awaiting_checks.insert(id);
            }
            state.changes.push(change.clone());
            Ok(change)
        })
    }

    fn find_changes(&self, head: &str, base: &str) -> Result<Vec<ChangeRequest>> {
        addressable(head, "the head branch")?;
        addressable(base, "the base branch")?;
        let state = self.store.snapshot()?;
        Ok(state
            .changes
            .iter()
            .filter(|change| {
                change.base == base
                    && state.heads.get(&change.id).is_some_and(|from| from == head)
                    // Only the open ones: a change the host has already merged is
                    // not one to adopt.
                    && !matches!(state.merges.get(&change.id), Some(MergeOutcome::Merged(_)))
            })
            .cloned()
            .collect())
    }

    fn change_checks(&self, cr: &ChangeRequest) -> Result<ChangeChecks> {
        let state = self.store.snapshot()?;
        let sources = state.check_sources.clone().unwrap_or_else(complete_sources);
        // The same refusal the real implementation makes when its credential can
        // read neither the host's check rollup nor its Actions API: what the checks
        // say is unknown, and answering "none" for "could not look" is what lets a
        // merge through unguarded.
        if sources.is_empty() {
            return Err(Error::Invalid {
                reason: format!(
                    "this host was seeded with no check source, so what the checks on {} say \
                     cannot be read rather than being empty",
                    cr.url
                ),
            });
        }
        Ok(ChangeChecks {
            checks: current_checks(&state, &cr.id),
            sources,
        })
    }

    fn check_log(&self, cr: &ChangeRequest, check: &Check) -> Result<ArtifactId> {
        let log = self
            .store
            .snapshot()?
            .check_logs
            .get(&cr.id)
            .and_then(|logs| logs.get(&check.name))
            .cloned()
            .unwrap_or_else(|| format!("the host log for check {}\n", check.name));
        events::store_artifact(&artifact_id(&cr.id, &check.name), &log)
    }

    fn merge(&self, cr: &ChangeRequest, policy: MergePolicy) -> Result<MergeOutcome> {
        self.store.with(|state| {
            // What GitHub answers: a draft can be neither merged nor armed to merge
            // itself (`Pull Request is still a draft`), so a publication that asked
            // before lifting it fails here rather than landing work nobody lifted.
            if matches!(policy, MergePolicy::ChangeAuto | MergePolicy::ChangeDirect)
                && drafted(state, &cr.id)
            {
                return Err(Error::Invalid {
                    reason: format!(
                        "{} is still a draft, and a draft can be neither merged nor armed to \
                         merge itself",
                        cr.url
                    ),
                });
            }
            // A seeded outcome is the host's decision and outranks the policy: it is
            // how a journey says "this one is queued behind something" or "this one
            // has already landed".
            if let Some(decided) = state.merges.get(&cr.id) {
                return Ok(decided.clone());
            }
            let landed = |state: &mut HostState| MergeOutcome::Merged(land(state, cr));
            Ok(match policy {
                // Nothing is asked of the host, so nothing is recorded — the same
                // answer the real implementation gives without a call.
                MergePolicy::LocalDirect | MergePolicy::ChangeOpen => MergeOutcome::Open,
                MergePolicy::ChangeAuto => {
                    if required_checks_green(state, &cr.id) {
                        landed(state)
                    } else {
                        // Native auto-merge: the host holds it and lands it when its
                        // own required checks pass, so nothing merges now.
                        state.merges.insert(cr.id.clone(), MergeOutcome::Queued);
                        MergeOutcome::Queued
                    }
                }
                MergePolicy::ChangeDirect => landed(state),
            })
        })
    }

    /// Take the change request out of its draft state.
    ///
    /// The call itself is what is recorded, rather than a flag that would read the
    /// same whether it was made once or twice: what a journey asks of this is whether
    /// a second publication over an already-lifted change asked the host for
    /// anything, and only the calls can answer that. A change already open for review
    /// is already what this asks for, so it succeeds — the caller wanted it ready,
    /// and it is.
    fn ready_for_review(&self, cr: &ChangeRequest) -> Result<()> {
        self.store.with(|state| {
            state.made_ready.push(cr.id.clone());
            Ok(())
        })
    }

    // llmlint: ignore[invalid_states_unrepresentable] the signature is the trait's, which
    // the approved amendment in `docs/contract.md` declares verbatim as `-> Result<bool>`;
    // an implementation cannot narrow it, and a named domain type would be a public item
    // the contract does not name. The third state a caller must not read as "not a draft"
    // — "this host would not say" — is the `Err` arm rather than a value inside it, and the
    // reason is recorded on the declaration in the crate next door.
    fn is_draft(&self, cr: &ChangeRequest) -> Result<bool> {
        Ok(drafted(&self.store.snapshot()?, &cr.id))
    }

    /// What the repository requires before a merge into `base`: the seeded answer,
    /// or — unset — exactly the checks seeded as required, completely.
    fn required_checks_on(&self, _base: &str) -> Result<RequiredChecks> {
        let state = self.store.snapshot()?;
        if let Some(seeded) = state.required_checks {
            return Ok(seeded);
        }
        Ok(RequiredChecks {
            checks: state
                .checks
                .values()
                .chain(state.checks_after_lift.values())
                .flatten()
                .filter(|check| check.required)
                .map(|check| check.name.clone())
                .collect(),
            unconsulted: std::collections::BTreeMap::new(),
        })
    }

    /// Replace the description, recording the call.
    ///
    /// The title and body go where `open_change` put the ones it was given, so what
    /// `change_description` reads back is the same record whichever call wrote it —
    /// and the call itself is kept, for the reason `ready_for_review`'s is: a journey
    /// about a closeout asks what was written and in what order, and the current
    /// description cannot say. A title that names nothing is refused as the real host
    /// refuses one; a body is prose, and an empty one is a description a caller may
    /// mean.
    fn describe_change(&self, cr: &ChangeRequest, title: Option<&str>, body: &str) -> Result<()> {
        if let Some(title) = title {
            crate::state::titled(title)?;
        }
        self.store.with(|state| {
            if !state.changes.iter().any(|change| change.id == cr.id) {
                return Err(Error::Invalid {
                    reason: format!(
                        "no change request {:?} was opened on this host, so there is nothing to \
                         describe",
                        cr.id.0
                    ),
                });
            }
            if let Some(title) = title {
                state.titles.insert(cr.id.clone(), title.to_owned());
            }
            state.bodies.insert(cr.id.clone(), body.to_owned());
            state.described.push(Described {
                id: cr.id.clone(),
                title: title.map(str::to_owned),
                body: body.to_owned(),
            });
            Ok(())
        })
    }

    /// The description as this host holds it: the title it was opened or last
    /// described with, and the body — empty where it was opened with none and never
    /// described since, which is what the real host answers for one.
    fn change_description(&self, cr: &ChangeRequest) -> Result<Description> {
        let state = self.store.snapshot()?;
        let title = state
            .titles
            .get(&cr.id)
            .cloned()
            .ok_or_else(|| Error::Invalid {
                reason: format!(
                    "no change request {:?} was opened on this host, so it has no description",
                    cr.id.0
                ),
            })?;
        Ok(Description {
            title,
            body: state.bodies.get(&cr.id).cloned().unwrap_or_default(),
        })
    }

    fn merged_at(&self, cr: &ChangeRequest) -> Result<Option<Sha>> {
        self.store.with(|state| {
            // Native auto-merge, modelled rather than skipped: a change this host is
            // holding lands the moment its own required checks are green, on the
            // host's clock and not on the caller's. Asking is what makes that
            // observable — which is exactly the shape a publication watching the
            // real GitHub meets, and the reason a journey can drive a change request
            // from queued to merged without a second process.
            if matches!(state.merges.get(&cr.id), Some(MergeOutcome::Queued))
                && required_checks_green(state, &cr.id)
            {
                return Ok(Some(land(state, cr)));
            }
            Ok(match state.merges.get(&cr.id) {
                Some(MergeOutcome::Merged(sha)) => Some(sha.clone()),
                _ => None,
            })
        })
    }
}

/// Record this change request as merged, and answer with the commit it merged at.
///
/// One place, so the merge a policy performs and the merge the host completes on
/// its own report the same commit for the same change.
fn land(state: &mut HostState, cr: &ChangeRequest) -> Sha {
    let sha = Sha(events::stable_sha(&["merge", &cr.id.0, cr.url.as_str()]));
    state
        .merges
        .insert(cr.id.clone(), MergeOutcome::Merged(sha.clone()));
    sha
}

/// What a host that was not told otherwise answers about where its checks came
/// from: the host's own rollup, which is every check anything posted on the change
/// request — the answer a credential allowed to read check runs gets.
fn complete_sources() -> std::collections::BTreeSet<CheckSource> {
    [CheckSource::StatusChecks].into_iter().collect()
}

/// Whether every required check on a change request lets the host merge it.
///
/// A change with no required checks is not green: nothing has vouched for it, which
/// is the state auto-merge waits in rather than lands from. A skipped required check
/// lets the merge through, as it does on GitHub's own merge path — which is why that
/// is a state of its own rather than a pass.
fn required_checks_green(state: &HostState, id: &ChangeId) -> bool {
    let checks = current_checks(state, id);
    let required: Vec<&Check> = checks.iter().filter(|check| check.required).collect();
    !required.is_empty()
        && required
            .iter()
            .all(|check| matches!(check.state(), CheckState::Passed | CheckState::Skipped))
}

/// Whether this host holds a change request as a draft: opened as one, for a reason
/// or while its checks run, and not lifted since.
fn drafted(state: &HostState, id: &ChangeId) -> bool {
    (state.drafts.contains_key(id) || state.awaiting_checks.contains(id))
        && !state.made_ready.contains(id)
}

/// The checks the host reports on a change request right now: the ones registered
/// after a lift, once it has been lifted and some are seeded, otherwise its own.
fn current_checks(state: &HostState, id: &ChangeId) -> Vec<Check> {
    if state.made_ready.contains(id) {
        if let Some(after) = state.checks_after_lift.get(id) {
            return after.clone();
        }
    }
    state.checks.get(id).cloned().unwrap_or_default()
}

/// The id one check's log is stored under.
///
/// Derived from what it is a log *of* rather than minted, so fetching the same
/// log twice does not leave two artifacts, and a journey can name the id it is
/// about to assert on.
fn artifact_id(change: &ChangeId, check: &str) -> String {
    let safe: String = check
        .chars()
        .map(|c| {
            if c.is_ascii_alphanumeric() || c == '-' || c == '_' || c == '.' {
                c
            } else {
                '-'
            }
        })
        .collect();
    let number: String = change
        .0
        .chars()
        .filter(|c| c.is_ascii_alphanumeric())
        .collect();
    format!("a-testing-{number}-{safe}")
}

/// One value bound for the host's argument vector, checked before it gets there.
///
/// The same refusal the real implementation makes, and for the same reason: a name
/// shaped like an option or an absent value addresses something other than what it
/// names, and a provider that accepted one would let a journey pass where the real
/// host rejects.
fn addressable(value: &str, what: &str) -> Result<()> {
    if value.is_empty() || value.starts_with('-') || value.contains(char::is_whitespace) {
        return Err(Error::Invalid {
            reason: format!(
                "{what} {value:?} cannot address anything on the host: it must be non-empty, \
                 must not begin with '-', and must carry no whitespace"
            ),
        });
    }
    Ok(())
}

/// A slug that names one repository, as `owner/name`.
fn named_repository(slug: &str) -> Result<String> {
    let mut parts = slug.split('/');
    let named = matches!(
        (parts.next(), parts.next(), parts.next()),
        (Some(owner), Some(name), None)
            if !owner.is_empty()
                && !name.is_empty()
                && !slug.starts_with('-')
                && !slug.contains(char::is_whitespace)
    );
    if !named {
        return Err(Error::Invalid {
            reason: format!("{slug:?} does not name one repository as owner/name"),
        });
    }
    Ok(slug.to_owned())
}