//! What a host (a hub) does to a repository without a workspace (hub spec
//! §6.9, §7.6): build a change from an edit set on any state, sign a
//! reference update with a key it holds, and apply both through the same
//! validation a received push gets. Nothing here bypasses policy.

use super::*;
use crate::identity::SecretKey;

/// One file of an edit set: new content, or `None` to remove the path.
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct FileEdit {
    pub path: String,
    pub content: Option<Vec<u8>>,
}

impl Repo {
    /// Build (but do not store or sign) a change that turns the state with
    /// `heads` into that state with `edits` applied, authored by `author`.
    /// Files the edits do not name keep their content, conflict markers
    /// included, so an edit that removes a file's markers resolves that
    /// file's conflict (a resolution change, spec §9.6).
    pub fn build_change(
        &self,
        heads: &[ChangeHash],
        edits: &[FileEdit],
        message: &str,
        author: KeyId,
    ) -> Result<Change> {
        if message.trim().is_empty() {
            return fail("a change message is required");
        }
        if edits.is_empty() {
            return fail("nothing to change");
        }
        let base = self.load_state(heads)?;
        let base_snapshot = base.materialize();
        let mut entries: BTreeMap<String, FsEntry> = BTreeMap::new();
        for (path, f) in &base_snapshot.files {
            let entry = match (&f.kind, &f.content) {
                (NodeKind::Dir, _) | (_, FileContent::Dir) => continue,
                (kind, FileContent::Text { bytes, .. }) => {
                    FsEntry::new(*kind, f.mode.exec, bytes.clone())
                }
                (kind, FileContent::Opaque { blobs }) => FsEntry {
                    blob: blobs.first().copied(),
                    ..FsEntry::new(*kind, f.mode.exec, vec![])
                },
            };
            entries.insert(path.clone(), entry);
        }
        for e in edits {
            let path = e.path.trim_matches('/');
            if path.is_empty()
                || path
                    .split('/')
                    .any(|c| c.is_empty() || c == "." || c == ".." || c == OXY_DIR)
            {
                return fail(format!("{:?} is not a valid path", e.path));
            }
            match &e.content {
                Some(bytes) => {
                    let exec = entries.get(path).map(|x| x.exec).unwrap_or(false);
                    // A file cannot sit where a directory is, or inside a file.
                    if base_snapshot
                        .files
                        .get(path)
                        .is_some_and(|f| f.kind == NodeKind::Dir)
                    {
                        return fail(format!("{path} is a directory"));
                    }
                    let mut parent = path;
                    while let Some((p, _)) = parent.rsplit_once('/') {
                        if base_snapshot
                            .files
                            .get(p)
                            .is_some_and(|f| f.kind != NodeKind::Dir)
                        {
                            return fail(format!("{p} is a file, not a directory"));
                        }
                        parent = p;
                    }
                    entries.insert(
                        path.to_string(),
                        FsEntry::new(NodeKind::File, exec, bytes.clone()),
                    );
                }
                None => {
                    if entries.remove(path).is_none() {
                        // Removing a directory removes everything below it.
                        let prefix = format!("{path}/");
                        let before = entries.len();
                        entries.retain(|p, _| !p.starts_with(&prefix));
                        if entries.len() == before {
                            return fail(format!("{path} does not exist"));
                        }
                    }
                }
            }
        }
        // A path the user writes settles its replace conflict, if any: they
        // chose that content (spec §9.3).
        let written: std::collections::HashSet<String> = edits
            .iter()
            .filter(|e| e.content.is_some())
            .map(|e| e.path.trim_matches('/').to_string())
            .collect();
        let built = self.build_from_entries_resolving(
            &base,
            &base_snapshot,
            HashMap::new(),
            &entries,
            &written,
        )?;
        if let Some(s) = built
            .statuses
            .iter()
            .find(|s| s.status == ChangeStatus::ConflictEdited)
        {
            return fail(format!("{} still contains conflict markers", s.path));
        }
        if built.tree_ops.is_empty() && built.edits.is_empty() {
            return fail("the edits change nothing");
        }
        let mut change = Change {
            change_id: ChangeId::random(),
            deps: vec![],
            author,
            hlc: Hlc::now(),
            message: message.trim_end().to_string(),
            tree_ops: built.tree_ops,
            edits: built.edits,
            kind: if built.resolves {
                ChangeKind::Resolution
            } else {
                ChangeKind::Normal
            },
        };
        let mut deps: BTreeSet<ChangeHash> = referenced_changes(&change, &base);
        deps.extend(built.contributors.iter().copied());
        change.deps = deps.into_iter().collect();
        change.normalize();
        Ok(change)
    }

    /// A reference update of `bookmark` to `heads`, attested by `signer`
    /// when given (the attestation a push would carry, spec §14.4).
    pub fn host_ref_update(
        &self,
        bookmark: &str,
        heads: &[ChangeHash],
        signer: Option<(&KeyId, &SecretKey)>,
    ) -> Result<RefUpdate> {
        let view = self.view()?;
        let empty = self.store.put_state(&StateObject::new(vec![]))?;
        let old_state = view.bookmarks.get(bookmark).copied().unwrap_or(empty);
        let new_state = self.store.put_state(&StateObject::new(heads.to_vec()))?;
        let attestation = match signer {
            Some((key, sk)) => {
                let serial = self
                    .latest_ref_attest(bookmark)?
                    .and_then(|(_, a)| match a.attest.body {
                        AttestBody::Ref { serial, .. } => Some(serial),
                        _ => None,
                    })
                    .map(|s| s + 1)
                    .unwrap_or(1);
                let attest = Attest {
                    repo: self.id()?,
                    hlc: Hlc::now(),
                    body: AttestBody::Ref {
                        name: bookmark.to_string(),
                        old_state,
                        new_state,
                        serial,
                    },
                };
                let r = attest.hash();
                let sig = sk.sign(Domain::Attest, key, &r);
                Some(SignedAttest {
                    attest,
                    sigs: vec![sig],
                })
            }
            None => None,
        };
        Ok(RefUpdate {
            name: bookmark.to_string(),
            old_state,
            new_state,
            force: false,
            attestation,
        })
    }

    /// Apply a host-made update as if it had been pushed: the new change
    /// (with its signatures) if any, the identities it needs, and the
    /// reference update, all through `receive_push_report`, so the same
    /// authentication, compare-and-swap and policy checks apply.
    pub fn apply_hosted(
        &self,
        change: Option<(Change, Vec<Signature>)>,
        identities: &[Identity],
        update: RefUpdate,
    ) -> Result<PushReport> {
        let mut bundle = Bundle::default();
        for id in identities {
            bundle.objects.push((ObjectType::Identity, id.encode()));
        }
        if let Ok(st) = self.store.get_state(&update.new_state) {
            bundle.objects.push((ObjectType::State, st.encode()));
        }
        if let Some((c, sigs)) = change {
            bundle.changes.push((c, sigs));
        }
        self.receive_push_report(bundle, vec![update], None, vec![])
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::identity::SecretKey;

    fn hermetic() {
        static ONCE: std::sync::Once = std::sync::Once::new();
        static DIR: std::sync::OnceLock<tempfile::TempDir> = std::sync::OnceLock::new();
        ONCE.call_once(|| {
            let d = tempfile::tempdir().unwrap();
            std::env::set_var("OXY_HOME", d.path());
            DIR.set(d).ok();
        });
    }

    fn write(root: &Path, rel: &str, content: &[u8]) {
        let p = root.join(rel);
        fs::create_dir_all(p.parent().unwrap()).unwrap();
        fs::write(p, content).unwrap();
    }

    /// A user repository pushed to a bare host, and a hub key the user
    /// has delegated to. Returns (host, user, hub key, hub secret).
    fn setup(
        root: &Path,
        with_policy: bool,
        delegate: bool,
    ) -> (Repo, Repo, KeyId, SecretKey, Identity) {
        hermetic();
        let host_dir = root.join("host");
        Repo::init_bare_unbound(&host_dir).unwrap();
        let work = root.join("work");
        let mut user = Repo::init(&work).unwrap();
        user.create_identity("Andy", "andy@example.com", IdentityScope::Repo)
            .unwrap();
        user.config.set("core.sign", "change").unwrap();
        user.config
            .set("remote.origin.url", host_dir.to_str().unwrap())
            .unwrap();
        user.save_config().unwrap();
        let hub_sk = SecretKey::generate();
        let hub_id = hub_sk.identity("Hub", "hub@example", 1);
        let hub_key = hub_id.hash();
        if with_policy {
            user.policy_init().unwrap();
        }
        if delegate {
            user.delegate_add(hub_id.clone()).unwrap();
        }
        write(&work, "a.txt", b"one\ntwo\n");
        user.snapshot("t").unwrap();
        user.commit("first", &[]).unwrap();
        let r = user.push("origin", false).unwrap();
        assert!(r.iter().all(|x| x.ok), "{r:?}");
        (
            Repo::open(&host_dir).unwrap(),
            user,
            hub_key,
            hub_sk,
            hub_id,
        )
    }

    #[test]
    fn a_host_edit_signed_by_a_delegate_lands() {
        let dir = tempfile::tempdir().unwrap();
        let (host, user, hub_key, hub_sk, hub_id) = setup(dir.path(), false, true);
        let author = user.config.author_key.unwrap();
        let heads = host.bookmark_heads().unwrap();
        let change = host
            .build_change(
                &heads,
                &[
                    FileEdit {
                        path: "a.txt".into(),
                        content: Some(b"one\ntwo\nthree\n".to_vec()),
                    },
                    FileEdit {
                        path: "docs/new.md".into(),
                        content: Some(b"# New\n".to_vec()),
                    },
                ],
                "Edit on the web",
                author,
            )
            .unwrap();
        assert_eq!(change.author, author);
        assert_eq!(change.kind, ChangeKind::Normal);
        let hash = change.hash();
        let sig = hub_sk.sign(Domain::Change, &hub_key, &hash);
        let mut new_heads = heads.clone();
        new_heads.push(hash);
        let update = host
            .host_ref_update("main", &[hash], Some((&hub_key, &hub_sk)))
            .unwrap();
        let ids = vec![hub_id, user.identity(&author).unwrap()];
        let report = host
            .apply_hosted(Some((change, vec![sig])), &ids, update)
            .unwrap();
        assert!(report.results.iter().all(|r| r.ok), "{:?}", report.results);
        assert_eq!(host.bookmark_heads().unwrap(), vec![hash]);
        assert_eq!(
            host.file_at("a.txt", Some(&[hash])).unwrap(),
            b"one\ntwo\nthree\n"
        );
        assert_eq!(
            host.file_at("docs/new.md", Some(&[hash])).unwrap(),
            b"# New\n"
        );
        // Authored by the user, authenticated by the hub key as delegate.
        assert!(
            matches!(host.authenticate_change(&hash).unwrap(), SignatureStatus::Valid { key, name, .. } if key == hub_key && name == "Hub")
        );
        let _ = new_heads;
        // Bad paths and empty edits are refused.
        assert!(host
            .build_change(
                &[hash],
                &[FileEdit {
                    path: "../x".into(),
                    content: Some(vec![])
                }],
                "m",
                author
            )
            .is_err());
        assert!(
            host.build_change(
                &[hash],
                &[FileEdit {
                    path: "a.txt".into(),
                    content: Some(b"one\ntwo\nthree\n".to_vec())
                }],
                "m",
                author
            )
            .is_err(),
            "no-op edits are refused"
        );
        assert!(
            host.build_change(
                &[hash],
                &[FileEdit {
                    path: "a.txt/b".into(),
                    content: Some(vec![])
                }],
                "m",
                author
            )
            .is_err(),
            "a file inside a file"
        );
        let rm = host
            .build_change(
                &[hash],
                &[FileEdit {
                    path: "docs".into(),
                    content: None,
                }],
                "Remove docs",
                author,
            )
            .unwrap();
        assert!(!rm.tree_ops.is_empty());
    }

    #[test]
    fn a_host_edit_by_a_key_that_is_not_a_delegate_is_refused() {
        let dir = tempfile::tempdir().unwrap();
        let (host, user, hub_key, hub_sk, hub_id) = setup(dir.path(), false, false);
        let author = user.config.author_key.unwrap();
        let heads = host.bookmark_heads().unwrap();
        let change = host
            .build_change(
                &heads,
                &[FileEdit {
                    path: "a.txt".into(),
                    content: Some(b"x\n".to_vec()),
                }],
                "Edit",
                author,
            )
            .unwrap();
        let hash = change.hash();
        let sig = hub_sk.sign(Domain::Change, &hub_key, &hash);
        let update = host
            .host_ref_update("main", &[hash], Some((&hub_key, &hub_sk)))
            .unwrap();
        let report = host
            .apply_hosted(
                Some((change, vec![sig])),
                &[hub_id, user.identity(&author).unwrap()],
                update,
            )
            .unwrap();
        // Without a policy the host accepts unauthenticated changes, but the
        // signature does not verify as the author's: it stays unauthenticated.
        assert!(report.results.iter().all(|r| r.ok));
        assert!(
            matches!(host.authenticate_change(&hash).unwrap(), SignatureStatus::Invalid(why) if why.contains("neither the author"))
        );
    }

    #[test]
    fn under_a_policy_a_delegate_may_update_the_reference_and_a_stranger_may_not() {
        let dir = tempfile::tempdir().unwrap();
        let (host, user, hub_key, hub_sk, hub_id) = setup(dir.path(), true, true);
        assert!(host.current_policy().unwrap().is_some());
        let author = user.config.author_key.unwrap();
        let heads = host.bookmark_heads().unwrap();
        let change = host
            .build_change(
                &heads,
                &[FileEdit {
                    path: "a.txt".into(),
                    content: Some(b"one\n".to_vec()),
                }],
                "Trim",
                author,
            )
            .unwrap();
        let hash = change.hash();
        let sig = hub_sk.sign(Domain::Change, &hub_key, &hash);
        let ids = vec![hub_id.clone(), user.identity(&author).unwrap()];
        let update = host
            .host_ref_update("main", &[hash], Some((&hub_key, &hub_sk)))
            .unwrap();
        let report = host
            .apply_hosted(Some((change, vec![sig])), &ids, update)
            .unwrap();
        assert!(report.results.iter().all(|r| r.ok), "{:?}", report.results);
        assert_eq!(host.bookmark_heads().unwrap(), vec![hash]);

        // A stranger's key cannot move the reference, even with the user as author.
        let stranger = SecretKey::generate();
        let sid = stranger.identity("Mallory", "m@example", 1);
        let skey = sid.hash();
        let change2 = host
            .build_change(
                &[hash],
                &[FileEdit {
                    path: "a.txt".into(),
                    content: Some(b"evil\n".to_vec()),
                }],
                "Evil",
                author,
            )
            .unwrap();
        let h2 = change2.hash();
        let sig2 = stranger.sign(Domain::Change, &skey, &h2);
        let update = host
            .host_ref_update("main", &[h2], Some((&skey, &stranger)))
            .unwrap();
        let report = host
            .apply_hosted(Some((change2, vec![sig2])), &[sid], update)
            .unwrap();
        assert!(report.results.iter().all(|r| !r.ok), "{:?}", report.results);
        assert_eq!(
            host.bookmark_heads().unwrap(),
            vec![hash],
            "the reference did not move"
        );
        // An unsigned update is refused under a policy too.
        let update = host.host_ref_update("main", &[hash], None).unwrap();
        let report = host.apply_hosted(None, &[], update).unwrap();
        assert!(report.results.iter().all(|r| !r.ok));
    }

    #[test]
    fn a_host_edit_that_removes_markers_resolves_the_conflict() {
        let dir = tempfile::tempdir().unwrap();
        let (host, mut user, hub_key, hub_sk, hub_id) = setup(dir.path(), false, true);
        let author = user.config.author_key.unwrap();
        let base = host.bookmark_heads().unwrap();
        // Two independent edits of the same line: a conflict in the union.
        let a = host
            .build_change(
                &base,
                &[FileEdit {
                    path: "a.txt".into(),
                    content: Some(b"ONE\ntwo\n".to_vec()),
                }],
                "A",
                author,
            )
            .unwrap();
        let b = host
            .build_change(
                &base,
                &[FileEdit {
                    path: "a.txt".into(),
                    content: Some(b"uno\ntwo\n".to_vec()),
                }],
                "B",
                author,
            )
            .unwrap();
        let (ha, hb) = (a.hash(), b.hash());
        let ids = vec![hub_id.clone(), user.identity(&author).unwrap()];
        for (c, h) in [(a, ha), (b, hb)] {
            let sig = hub_sk.sign(Domain::Change, &hub_key, &h);
            let mut heads = host.bookmark_heads().unwrap();
            heads.retain(|x| !base.contains(x));
            heads.push(h);
            let update = host
                .host_ref_update("main", &heads, Some((&hub_key, &hub_sk)))
                .unwrap();
            let r = host
                .apply_hosted(Some((c, vec![sig])), &ids, update)
                .unwrap();
            assert!(r.results.iter().all(|x| x.ok), "{:?}", r.results);
        }
        let heads = host.bookmark_heads().unwrap();
        assert_eq!(heads.len(), 2);
        let marked = String::from_utf8(host.file_at("a.txt", Some(&heads)).unwrap()).unwrap();
        assert!(marked.contains("<<<<<<< oxy conflict"), "{marked}");
        // Saving with markers left in is refused; saving without them resolves.
        assert!(host
            .build_change(
                &heads,
                &[FileEdit {
                    path: "a.txt".into(),
                    content: Some(format!("{marked}x\n").into_bytes())
                }],
                "half",
                author
            )
            .is_err());
        let res = host
            .build_change(
                &heads,
                &[FileEdit {
                    path: "a.txt".into(),
                    content: Some(b"One\ntwo\n".to_vec()),
                }],
                "Resolve",
                author,
            )
            .unwrap();
        assert_eq!(res.kind, ChangeKind::Resolution);
        assert!(
            res.deps.contains(&ha) && res.deps.contains(&hb),
            "a resolution depends on both sides"
        );
        let hr = res.hash();
        let sig = hub_sk.sign(Domain::Change, &hub_key, &hr);
        let update = host
            .host_ref_update("main", &[hr], Some((&hub_key, &hub_sk)))
            .unwrap();
        let r = host
            .apply_hosted(Some((res, vec![sig])), &ids, update)
            .unwrap();
        assert!(r.results.iter().all(|x| x.ok), "{:?}", r.results);
        assert_eq!(host.file_at("a.txt", Some(&[hr])).unwrap(), b"One\ntwo\n");
        assert!(!host
            .load_state(&[hr])
            .unwrap()
            .materialize()
            .is_conflicted());
        let _ = &mut user;
    }
}