1 files changed, 193 insertions, 0 deletions
diff --git a/ops/gerrit-autosubmit/src/main.rs b/ops/gerrit-autosubmit/src/main.rs
new file mode 100644
index 000000000000..9d7087d67deb
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+++ b/ops/gerrit-autosubmit/src/main.rs
@@ -0,0 +1,193 @@
+//! gerrit-autosubmit connects to a Gerrit instance and submits the
+//! longest chain of changes in which all ancestors are ready and
+//! marked for autosubmit.
+//!
+//! It works like this:
+//!
+//! * it fetches all changes the Gerrit query API considers
+//!   submittable (i.e. all requirements fulfilled), and that have the
+//!   `Autosubmit` label set
+//!
+//! * it filters these changes down to those that are _actually_
+//!   submittable (in Gerrit API terms: that have an active Submit button)
+//!
+//! * it filters out those that would submit ancestors that are *not*
+//!   marked with the `Autosubmit` label
+//!
+//! * it submits the longest chain
+//!
+//! After that it just loops.
+
+use anyhow::{Context, Result};
+use std::collections::{BTreeMap, HashMap, HashSet};
+
+mod gerrit {
+    use anyhow::{anyhow, Context, Result};
+    use serde::Deserialize;
+    use serde_json::Value;
+    use std::collections::HashMap;
+    use std::env;
+
+    pub struct Config {
+        gerrit_url: String,
+        username: String,
+        password: String,
+    }
+
+    impl Config {
+        pub fn from_env() -> Result<Self> {
+            Ok(Config {
+                gerrit_url: env::var("GERRIT_URL")
+                    .context("Gerrit base URL (no trailing slash) must be set in GERRIT_URL")?,
+                username: env::var("GERRIT_USERNAME")
+                    .context("Gerrit username must be set in GERRIT_USERNAME")?,
+                password: env::var("GERRIT_PASSWORD")
+                    .context("Gerrit password must be set in GERRIT_PASSWORD")?,
+            })
+        }
+    }
+
+    #[derive(Deserialize)]
+    pub struct ChangeInfo {
+        pub id: String,
+        pub revisions: HashMap<String, Value>,
+    }
+
+    #[derive(Deserialize)]
+    pub struct Action {
+        #[serde(default)]
+        pub enabled: bool,
+    }
+
+    const GERRIT_RESPONSE_PREFIX: &'static str = ")]}'";
+
+    pub fn get<T: serde::de::DeserializeOwned>(cfg: &Config, endpoint: &str) -> Result<T> {
+        let response = crimp::Request::get(&format!("{}/a{}", cfg.gerrit_url, endpoint))
+            .user_agent("gerrit-autosubmit")?
+            .basic_auth(&cfg.username, &cfg.password)?
+            .send()?
+            .error_for_status(|r| anyhow!("request failed with status {}", r.status))?;
+
+        let result: T = serde_json::from_slice(&response.body[GERRIT_RESPONSE_PREFIX.len()..])?;
+        Ok(result)
+    }
+
+    pub fn submit(cfg: &Config, change_id: &str) -> Result<()> {
+        let response = crimp::Request::post(&format!(
+            "{}/a/changes/{}/submit",
+            cfg.gerrit_url, change_id
+        ))
+        .user_agent("gerrit-autosubmit")?
+        .basic_auth(&cfg.username, &cfg.password)?
+        .send()?
+        .error_for_status(|r| anyhow!("submit failed with status {}", r.status))?;
+
+        Ok(())
+    }
+}
+
+#[derive(Debug)]
+struct SubmittableChange {
+    id: String,
+    revision: String,
+}
+
+fn list_submittable(cfg: &gerrit::Config) -> Result<Vec<SubmittableChange>> {
+    let mut out = Vec::new();
+
+    let changes: Vec<gerrit::ChangeInfo> = gerrit::get(
+        &cfg,
+        "/changes/?q=is:submittable+label:Autosubmit+-is:wip+is:open&o=SKIP_DIFFSTAT&o=CURRENT_REVISION",
+    )
+    .context("failed to list submittable changes")?;
+
+    for change in changes.into_iter() {
+        out.push(SubmittableChange {
+            id: change.id,
+            revision: change
+                .revisions
+                .into_keys()
+                .next()
+                .context("change had no current revision")?,
+        });
+    }
+
+    Ok(out)
+}
+
+fn is_submittable(cfg: &gerrit::Config, change: &SubmittableChange) -> Result<bool> {
+    let response: HashMap<String, gerrit::Action> = gerrit::get(
+        cfg,
+        &format!(
+            "/changes/{}/revisions/{}/actions",
+            change.id, change.revision
+        ),
+    )
+    .context("failed to fetch actions for change")?;
+
+    match response.get("submit") {
+        None => Ok(false),
+        Some(action) => Ok(action.enabled),
+    }
+}
+
+fn submitted_with(cfg: &gerrit::Config, change_id: &str) -> Result<HashSet<String>> {
+    let response: Vec<gerrit::ChangeInfo> =
+        gerrit::get(cfg, &format!("/changes/{}/submitted_together", change_id))
+            .context("failed to fetch related change list")?;
+
+    Ok(response.into_iter().map(|c| c.id).collect())
+}
+
+fn autosubmit(cfg: &gerrit::Config) -> Result<bool> {
+    let mut submittable_changes: HashSet<String> = Default::default();
+
+    for change in list_submittable(&cfg)? {
+        if !is_submittable(&cfg, &change)? {
+            continue;
+        }
+
+        submittable_changes.insert(change.id.clone());
+    }
+
+    let mut chains: BTreeMap<usize, String> = Default::default();
+    for change_id in &submittable_changes {
+        let ancestors = submitted_with(&cfg, &change_id)?;
+        if ancestors.is_subset(&submittable_changes) {
+            chains.insert(
+                if ancestors.is_empty() {
+                    1
+                } else {
+                    ancestors.len()
+                },
+                change_id.clone(),
+            );
+        }
+    }
+
+    // BTreeMap::last_key_value gives us the value associated with the
+    // largest key, i.e. with the longest submittable chain of changes.
+    if let Some((count, change_id)) = chains.last_key_value() {
+        println!(
+            "submitting change {} with chain length {}",
+            change_id, count
+        );
+
+        gerrit::submit(cfg, change_id);
+
+        Ok(true)
+    } else {
+        println!("nothing ready for autosubmit, waiting ...");
+        Ok(false)
+    }
+}
+
+fn main() -> Result<()> {
+    let cfg = gerrit::Config::from_env()?;
+
+    loop {
+        if !autosubmit(&cfg)? {
+            std::thread::sleep_ms(30000);
+        }
+    }
+}