1 files changed, 139 insertions, 0 deletions
diff --git a/src/github.rs b/src/github.rs
new file mode 100644
index 0000000..dc7c8e5
--- /dev/null
+++ b/src/github.rs
@@ -0,0 +1,139 @@
+// SPDX-License-Identifier: AGPL-3.0-or-later WITH GPL-3.0-linking-exception
+// SPDX-FileCopyrightText: 2021 Alyssa Ross <hi@alyssa.is>
+
+use std::ffi::OsStr;
+use std::fmt::{self, Display, Formatter};
+use std::os::unix::ffi::OsStrExt;
+
+use graphql_client::GraphQLQuery;
+use serde::Deserialize;
+use surf::http::headers::HeaderValue;
+use surf::StatusCode;
+
+type GitObjectID = String;
+
+#[derive(Debug)]
+pub enum Error {
+    NotFound,
+    Serialization(serde_json::Error),
+    Request(surf::Error),
+    Response(StatusCode),
+    Deserialization(http_types::Error),
+}
+
+impl Display for Error {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        use Error::*;
+        match self {
+            NotFound => write!(f, "Not found"),
+            Serialization(e) => write!(f, "Serialization error: {}", e),
+            Request(e) => write!(f, "Request error: {}", e),
+            Response(s) => write!(f, "Unexpected response status: {}", s),
+            Deserialization(e) => write!(f, "Deserialization error: {}", e),
+        }
+    }
+}
+
+impl std::error::Error for Error {}
+
+#[derive(GraphQLQuery)]
+#[graphql(
+    schema_path = "vendor/github_schema.graphql",
+    query_path = "src/merge_commit.graphql",
+    response_derives = "Debug"
+)]
+struct MergeCommitQuery;
+
+#[derive(Debug, Deserialize)]
+struct GitHubGraphQLResponse<D> {
+    data: D,
+}
+
+#[derive(Debug)]
+pub enum PullRequestStatus {
+    Open,
+    Closed,
+    Merged {
+        /// This field is optional because GitHub doesn't provide us with this information
+        /// for PRs merged before around March 2016.
+        merge_commit_oid: Option<String>,
+    },
+}
+
+#[derive(Debug)]
+pub struct MergeInfo {
+    pub branch: String,
+    pub status: PullRequestStatus,
+}
+
+pub struct GitHub<'a> {
+    token: &'a OsStr,
+    user_agent: &'a OsStr,
+}
+
+impl<'a> GitHub<'a> {
+    pub fn new(token: &'a OsStr, user_agent: &'a OsStr) -> Self {
+        Self { token, user_agent }
+    }
+
+    fn authorization_header(&self) -> Result<HeaderValue, surf::Error> {
+        let mut value = b"bearer ".to_vec();
+        value.extend_from_slice(self.token.as_bytes());
+        Ok(HeaderValue::from_bytes(value)?)
+    }
+
+    pub async fn merge_info_for_nixpkgs_pr(&self, pr: i64) -> Result<MergeInfo, Error> {
+        let query = MergeCommitQuery::build_query(merge_commit_query::Variables {
+            owner: "NixOS".to_string(),
+            repo: "nixpkgs".to_string(),
+            number: pr,
+        });
+
+        let response = surf::post("https://api.github.com/graphql")
+            .header("Accept", "application/vnd.github.merge-info-preview+json")
+            .header(
+                "User-Agent",
+                HeaderValue::from_bytes(self.user_agent.as_bytes().to_vec())
+                    .map_err(Error::Request)?,
+            )
+            .header(
+                "Authorization",
+                self.authorization_header().map_err(Error::Request)?,
+            )
+            .body(serde_json::to_vec(&query).map_err(Error::Serialization)?)
+            .send()
+            .await
+            .map_err(Error::Request)?;
+
+        let status = response.status();
+        if status == StatusCode::NotFound || status == StatusCode::Gone {
+            return Err(Error::NotFound);
+        } else if !status.is_success() {
+            return Err(Error::Response(status));
+        }
+
+        let data: GitHubGraphQLResponse<merge_commit_query::ResponseData> = dbg!(response)
+            .body_json()
+            .await
+            .map_err(Error::Deserialization)?;
+
+        let pr = data
+            .data
+            .repository
+            .and_then(|repo| repo.pull_request)
+            .ok_or(Error::NotFound)?;
+
+        Ok(MergeInfo {
+            branch: pr.base_ref_name,
+            status: if pr.merged {
+                PullRequestStatus::Merged {
+                    merge_commit_oid: pr.merge_commit.map(|commit| commit.oid),
+                }
+            } else if pr.closed {
+                PullRequestStatus::Closed
+            } else {
+                PullRequestStatus::Open
+            },
+        })
+    }
+}