thirdshift 0.10.0

//! Asking GitHub, through `gh`, about issues, pull requests and the signed-in
//! user.

use std::fmt;
use std::process::{Command, Output};

use anyhow::{Context, Result, bail};
use chrono::{DateTime, Utc};
use serde_json::Value;

use crate::issue::IssueUrl;
use crate::labels::{Label, Labels};
use crate::process::{self, Control, Interruption};

#[cfg(test)]
mod execution_tests;

/// GitHub CLI operations bound to an immutable interruption policy.
/// Ordinary views stop for Command interruption; completion views finish
/// independently without changing the recorded request or other views.
pub struct GitHub {
    interruption: Interruption,
}

impl GitHub {
    pub fn new() -> Self {
        Self {
            interruption: Interruption::Ordinary,
        }
    }

    pub fn completion(&self) -> Self {
        Self {
            interruption: Interruption::Completion,
        }
    }

    /// The `fields` of `issue`, as JSON.
    fn issue_view(&self, issue: &IssueUrl, fields: &str) -> Result<Value> {
        self.gh_json(&[
            "issue",
            "view",
            &issue.number.to_string(),
            "--repo",
            &issue.repo_slug(),
            "--json",
            fields,
        ])
    }

    /// Whether `issue` is open.
    pub fn issue_is_open(&self, issue: &IssueUrl) -> Result<bool> {
        state_is_open(&self.issue_view(issue, "state")?)
    }

    /// The title of `issue`.
    pub fn issue_title(&self, issue: &IssueUrl) -> Result<String> {
        let json = self.issue_view(issue, "title")?;
        Ok(json["title"]
            .as_str()
            .context("gh output has no title")?
            .to_string())
    }

    /// `issue`'s state, labels and when it was created.
    pub fn issue(&self, issue: &IssueUrl) -> Result<Issue> {
        let json = self.issue_view(issue, "state,labels,createdAt")?;
        let created = json["createdAt"]
            .as_str()
            .context("gh output has no createdAt")?;
        Ok(Issue {
            is_open: state_is_open(&json)?,
            labels: labels_of(&json)?,
            created: DateTime::parse_from_rfc3339(created)
                .with_context(|| format!("gh output has an unreadable createdAt {created}"))?
                .to_utc(),
        })
    }

    /// The labels of `issue`.
    pub fn issue_labels(&self, issue: &IssueUrl) -> Result<Labels> {
        labels_of(&self.issue_view(issue, "labels")?)
    }

    /// Set `issue`'s labels to exactly `labels`, in one request, so a swap of
    /// one label for another can't stop halfway. Through the REST API: `gh issue
    /// edit` fails on the GitHub Projects (classic) sunset in older `gh`.
    pub fn set_labels(&self, issue: &IssueUrl, labels: &Labels) -> Result<()> {
        let path = labels_path(issue);
        let fields: Vec<String> = labels
            .names()
            .map(|label| format!("labels[]={label}"))
            .collect();
        let mut args = vec!["api", "--method", "PUT", &path, "--silent"];
        for field in &fields {
            args.extend(["-f", field]);
        }
        self.gh(&args)
    }

    /// Take `label` off `issue`, in one request that keeps its other labels.
    /// Through the REST API, as [`GitHub::set_labels`] is. GitHub refuses it if the issue
    /// does not have the label.
    pub fn remove_label(&self, issue: &IssueUrl, label: &str) -> Result<()> {
        self.gh(&[
            "api",
            "--method",
            "DELETE",
            &label_path(issue, label),
            "--silent",
        ])
    }

    /// The sub-issues of `issue`, its Tickets if it has any, in one query.
    pub fn tickets(&self, issue: &IssueUrl) -> Result<Vec<Ticket>> {
        let json = self.issue_query(issue, TICKETS_QUERY)?;
        nodes(
            &json["data"]["repository"]["issue"]["subIssues"],
            "subIssues",
        )?
        .iter()
        .map(|node| {
            let mut blockers = Vec::new();
            let mut open_blockers = Vec::new();
            for blocker in nodes(&node["blockedBy"], "blockedBy")? {
                blockers.push(node_number(blocker)?);
                if node_is_open(blocker)? {
                    open_blockers.push(node_number(blocker)?);
                }
            }
            Ok(Ticket {
                number: node_number(node)?,
                is_open: node_is_open(node)?,
                labels: named(nodes(&node["labels"], "labels")?),
                has_sub_issues: sub_issue_count(node)? > 0,
                blockers,
                open_blockers,
            })
        })
        .collect()
    }

    /// The answer to `query`, a GraphQL query about `issue` that takes its
    /// `$owner`, `$repo` and `$number`.
    fn issue_query(&self, issue: &IssueUrl, query: &str) -> Result<Value> {
        self.gh_json(&[
            "api",
            "graphql",
            "-f",
            &format!("query={query}"),
            "-f",
            &format!("owner={}", issue.owner),
            "-f",
            &format!("repo={}", issue.repo),
            "-F",
            &format!("number={}", issue.number),
        ])
    }

    /// Close `issue` with `comment`.
    pub fn close_issue(&self, issue: &IssueUrl, comment: &str) -> Result<()> {
        self.gh(&[
            "issue",
            "close",
            &issue.number.to_string(),
            "--repo",
            &issue.repo_slug(),
            "--comment",
            comment,
        ])
    }

    /// Every open issue labelled `label` in the repository `repo`, an
    /// `owner/repo`, newest first. They come from GitHub's issue list, not its
    /// search, whose index can be a while behind an issue just opened.
    pub fn open_issues_labelled(&self, repo: &str, label: Label) -> Result<Vec<ListedIssue>> {
        self.issues_labelled(repo, label, "open")
    }

    /// Every closed issue labelled `label` in the repository `repo`, an
    /// `owner/repo`, newest first.
    pub fn closed_issues_labelled(&self, repo: &str, label: Label) -> Result<Vec<ListedIssue>> {
        self.issues_labelled(repo, label, "closed")
    }

    /// Every issue labelled `label` in the repository `repo` whose state is
    /// `state`, `open` or `closed`, newest first.
    fn issues_labelled(&self, repo: &str, label: Label, state: &str) -> Result<Vec<ListedIssue>> {
        let json = self.gh_json(&[
            "issue",
            "list",
            "--state",
            state,
            "--repo",
            repo,
            "--label",
            label.name(),
            "--json",
            "url,title,labels",
            "--limit",
            "1000",
        ])?;
        json.as_array()
            .context("gh issue list did not return a list")?
            .iter()
            .map(|listed| {
                let field = |name: &str| {
                    listed[name]
                        .as_str()
                        .with_context(|| format!("gh issue list output has no {name}"))
                };
                Ok(ListedIssue {
                    issue: IssueUrl::parse(field("url")?)?,
                    title: field("title")?.to_string(),
                    labels: labels_of(listed)?,
                })
            })
            .collect()
    }

    /// `issue` as a Pickup run that lists issues by `label` reads it, in one
    /// query.
    pub fn candidate(&self, issue: &IssueUrl, label: Label) -> Result<Candidate> {
        let json = self.issue_query(issue, CANDIDATE_QUERY)?;
        let issue = &json["data"]["repository"]["issue"];
        let parent = issue["parent"]["url"]
            .as_str()
            .map(IssueUrl::parse)
            .transpose()?;
        let mut open_blockers = Vec::new();
        for blocker in nodes(&issue["blockedBy"], "blockedBy")? {
            if node_is_open(blocker)? {
                open_blockers.push(node_number(blocker)?);
            }
        }
        let at = |event: &Value| -> Result<DateTime<Utc>> {
            let at = event["createdAt"]
                .as_str()
                .context("gh api graphql output has an event with no createdAt")?;
            Ok(DateTime::parse_from_rfc3339(at)
                .with_context(|| format!("gh api graphql output has an unreadable createdAt {at}"))?
                .to_utc())
        };
        let mut shaped = Vec::new();
        for event in nodes(&issue["labelled"], "labelled")? {
            let name = event["label"]["name"].as_str();
            if name.is_some_and(|name| label.is_named(name)) {
                shaped.push(Shaped {
                    by: Shaping::Labelled,
                    at: at(event)?,
                });
            }
        }
        for event in nodes(&issue["linked"], "linked")? {
            let by = match event["__typename"].as_str() {
                Some("SubIssueAddedEvent" | "SubIssueRemovedEvent") => Shaping::SubIssues,
                Some("BlockedByAddedEvent" | "BlockedByRemovedEvent") => Shaping::Blockers,
                other => bail!("gh api graphql output has an unknown event {other:?}"),
            };
            shaped.push(Shaped { by, at: at(event)? });
        }
        Ok(Candidate {
            parent,
            sub_issue_is_open: nodes(&issue["subIssues"], "subIssues")?
                .iter()
                .map(node_is_open)
                .collect::<Result<_>>()?,
            open_blockers,
            last_shaped: shaped.into_iter().max_by_key(|shaped| shaped.at),
        })
    }

    /// Add each of `labels` to the repository `repo`, an `owner/repo`, with its
    /// description, unless the repository has it already.
    pub fn ensure_labels(&self, repo: &str, labels: &[Label]) -> Result<()> {
        let known = self.gh_json(&[
            "label", "list", "--repo", repo, "--json", "name", "--limit", "1000",
        ])?;
        let known = named(
            known
                .as_array()
                .context("gh label list did not return a list")?,
        );
        for label in labels {
            if !known.has(*label) {
                self.gh(&[
                    "label",
                    "create",
                    label.name(),
                    "--repo",
                    repo,
                    "--description",
                    label.description(),
                ])?;
            }
        }
        Ok(())
    }

    /// Open an issue titled `title`, with `body` and `labels`, in the repository
    /// of `issue`, and return it. Each label is first added to the repository,
    /// with its description, if the repository lacks it: `gh` refuses a label it
    /// doesn't know.
    pub fn create_issue(
        &self,
        issue: &IssueUrl,
        title: &str,
        body: &str,
        labels: &[Label],
    ) -> Result<IssueUrl> {
        let repo = issue.repo_slug();
        self.ensure_labels(&repo, labels)?;
        let names: Vec<&str> = labels.iter().map(|label| label.name()).collect();
        let url = self.gh_stdout(&[
            "issue",
            "create",
            "--repo",
            &repo,
            "--title",
            title,
            "--body",
            body,
            "--label",
            &names.join(","),
        ])?;
        IssueUrl::parse(&url).context("gh issue create did not print the issue's URL")
    }

    /// The public email of the signed-in user's GitHub profile, or `None` if it
    /// is private. Private addresses need the `user` scope, which a default
    /// `gh auth login` token lacks, so thirdshift never asks for them.
    pub fn profile_email(&self) -> Result<Option<String>> {
        let json = self.gh_json(&["api", "user"])?;
        Ok(json["email"].as_str().map(str::to_string))
    }

    /// The `fields` of the pull request `pr`, its head branch or its number, as
    /// JSON.
    fn pr_view(&self, issue: &IssueUrl, pr: &str, fields: &str) -> Result<Value> {
        self.gh_json(&[
            "pr",
            "view",
            pr,
            "--repo",
            &issue.repo_slug(),
            "--json",
            fields,
        ])
    }

    /// The pull request whose head is `branch`, if `gh` finds one.
    pub fn pull_request_for(&self, issue: &IssueUrl, branch: &str) -> Result<Option<PullRequest>> {
        let json = match self.pr_view(issue, branch, PR_FIELDS) {
            Ok(json) => json,
            Err(error) if format!("{error:#}").contains("no pull requests found") => {
                return Ok(None);
            }
            Err(error) => return Err(error),
        };
        PullRequest::from_json(&json).map(Some)
    }

    /// Every pull request in this repository, in any state, whose head branch
    /// starts with `prefix`. PRs from forks are left out: their heads are not
    /// this repository's branches.
    pub fn pull_requests_with_head_prefix(
        &self,
        issue: &IssueUrl,
        prefix: &str,
    ) -> Result<Vec<PullRequest>> {
        let json = self.gh_json(&[
            "pr",
            "list",
            "--repo",
            &issue.repo_slug(),
            "--state",
            "all",
            "--search",
            &format!("head:{prefix}"),
            "--limit",
            "1000",
            "--json",
            &format!("{PR_FIELDS},isCrossRepository"),
        ])?;
        json.as_array()
            .context("gh pr list did not return a list")?
            .iter()
            .filter(|pr| pr["isCrossRepository"] != Value::Bool(true))
            .map(PullRequest::from_json)
            .collect()
    }

    /// Open a draft pull request from `head` into `base`, and return its URL.
    pub fn create_draft_pr(
        &self,
        issue: &IssueUrl,
        head: &str,
        base: &str,
        title: &str,
        body: &str,
    ) -> Result<String> {
        self.gh_stdout(&[
            "pr",
            "create",
            "--repo",
            &issue.repo_slug(),
            "--head",
            head,
            "--base",
            base,
            "--title",
            title,
            "--body",
            body,
            "--draft",
        ])
    }

    /// The body of pull request `number`.
    pub fn pr_body(&self, issue: &IssueUrl, number: u64) -> Result<String> {
        let json = self.pr_view(issue, &number.to_string(), "body")?;
        Ok(json["body"]
            .as_str()
            .context("gh output has no body")?
            .to_string())
    }

    /// Set the body of pull request `number` to `body`, through the REST API:
    /// `gh pr edit` fails on the GitHub Projects (classic) sunset in older `gh`.
    pub fn set_pr_body(&self, issue: &IssueUrl, number: u64, body: &str) -> Result<()> {
        self.gh(&[
            "api",
            "--method",
            "PATCH",
            &format!("repos/{}/pulls/{number}", issue.repo_slug()),
            "-f",
            &format!("body={body}"),
            "--silent",
        ])
    }

    /// Mark the pull request whose head is `branch` ready for review.
    pub fn mark_ready(&self, issue: &IssueUrl, branch: &str) -> Result<()> {
        self.gh(&["pr", "ready", branch, "--repo", &issue.repo_slug()])
    }

    /// Convert the pull request whose head is `branch` back to a draft.
    pub fn convert_to_draft(&self, issue: &IssueUrl, branch: &str) -> Result<()> {
        self.gh(&[
            "pr",
            "ready",
            branch,
            "--undo",
            "--repo",
            &issue.repo_slug(),
        ])
    }

    /// Merge the pull request whose head is `branch` into its base with a merge
    /// commit, but only if its head is still `head`. Never GitHub's auto-merge
    /// (ADR-0004), and never `--delete-branch`, whose local deletion would
    /// interfere with the worktree. If `gh` fails but the pull request merged at
    /// `head` anyway, e.g. because `gh` was interrupted once GitHub had merged,
    /// that is a merge.
    pub fn merge(&self, issue: &IssueUrl, branch: &str, head: &str) -> Result<()> {
        let Err(error) = self.gh(&[
            "pr",
            "merge",
            branch,
            "--repo",
            &issue.repo_slug(),
            "--merge",
            "--match-head-commit",
            head,
        ]) else {
            return Ok(());
        };
        match self.completion().merged_head(issue, branch) {
            Ok(Some(merged)) if merged == head => Ok(()),
            _ => Err(error),
        }
    }

    /// The head commit the pull request whose head is `branch` was merged at, if
    /// it is merged.
    fn merged_head(&self, issue: &IssueUrl, branch: &str) -> Result<Option<String>> {
        let json = self.pr_view(issue, branch, "state,headRefOid")?;
        if json["state"] != "MERGED" {
            return Ok(None);
        }
        let head = json["headRefOid"]
            .as_str()
            .context("gh output has no headRefOid")?;
        Ok(Some(head.to_string()))
    }

    /// Whether the pull request whose head is `branch` can be merged.
    pub fn mergeable(&self, issue: &IssueUrl, branch: &str) -> Result<Mergeable> {
        let json = self.pr_view(issue, branch, "mergeable")?;
        match json["mergeable"].as_str() {
            Some("MERGEABLE") => Ok(Mergeable::Yes),
            Some("CONFLICTING") => Ok(Mergeable::No),
            Some("UNKNOWN") => Ok(Mergeable::Unknown),
            other => bail!("gh output has an unknown mergeable state {other:?}"),
        }
    }

    /// Every check run and commit status on commit `sha`. Of the check runs
    /// sharing a name, as the attempts of a re-run job do, only the latest is
    /// here.
    pub fn checks_on(&self, issue: &IssueUrl, sha: &str) -> Result<Vec<Check>> {
        let commit = format!("repos/{}/commits/{sha}", issue.repo_slug());
        let runs = self.gh_api_items(&format!("{commit}/check-runs?per_page=100"), "check_runs")?;
        let statuses = self.gh_api_items(&format!("{commit}/status?per_page=100"), "statuses")?;
        let url = |value: &Value| {
            value
                .as_str()
                .filter(|url| !url.is_empty())
                .map(String::from)
        };

        let mut checks = Vec::new();
        for run in &runs {
            let state = match (run["status"].as_str(), run["conclusion"].as_str()) {
                (Some("completed"), Some("success" | "neutral" | "skipped")) => CheckState::Passed,
                (Some("completed"), _) => CheckState::Failed,
                _ => CheckState::Pending,
            };
            checks.push(Check {
                name: run["name"]
                    .as_str()
                    .context("a check run has no name")?
                    .to_string(),
                state,
                job: ActionsJob::of(run["id"].as_u64(), run["details_url"].as_str()),
                url: url(&run["details_url"]).or_else(|| url(&run["html_url"])),
            });
        }
        for status in &statuses {
            let state = match status["state"].as_str() {
                Some("success") => CheckState::Passed,
                Some("pending") => CheckState::Pending,
                _ => CheckState::Failed,
            };
            checks.push(Check {
                name: status["context"]
                    .as_str()
                    .context("a commit status has no context")?
                    .to_string(),
                state,
                url: url(&status["target_url"]),
                job: None,
            });
        }
        Ok(checks)
    }

    /// Ask GitHub to re-run the failed jobs of the GitHub Actions workflow run
    /// `workflow_run`, as a new attempt of it.
    pub fn rerun_failed_jobs(&self, issue: &IssueUrl, workflow_run: u64) -> Result<()> {
        self.gh(&[
            "run",
            "rerun",
            &workflow_run.to_string(),
            "--failed",
            "--repo",
            &issue.repo_slug(),
        ])
    }

    /// Run `gh <args>`, failing with its stderr if it exits non-zero.
    fn gh(&self, args: &[&str]) -> Result<()> {
        self.gh_stdout(args).map(drop)
    }

    /// Run `gh <args>` and return its trimmed stdout, failing with its stderr if
    /// it exits non-zero.
    fn gh_stdout(&self, args: &[&str]) -> Result<String> {
        let output = self.output(args)?;
        if !output.status.success() {
            bail!(
                "gh {} failed: {}",
                args.join(" "),
                String::from_utf8_lossy(&output.stderr).trim()
            );
        }
        Ok(String::from_utf8_lossy(&output.stdout).trim().to_string())
    }

    /// Every item of the `field` list of the GitHub API's `path`, across all its
    /// pages.
    fn gh_api_items(&self, path: &str, field: &str) -> Result<Vec<Value>> {
        let output = self.output(&["api", "--paginate", "--jq", &format!(".{field}[]"), path])?;
        if !output.status.success() {
            bail!(
                "gh api {path} failed: {}",
                String::from_utf8_lossy(&output.stderr).trim()
            );
        }
        serde_json::Deserializer::from_slice(&output.stdout)
            .into_iter()
            .collect::<Result<_, _>>()
            .with_context(|| format!("gh api {path} returned invalid JSON"))
    }

    /// Run `gh <args>` and parse its stdout as JSON, failing with gh's stderr if
    /// it exits non-zero.
    fn gh_json(&self, args: &[&str]) -> Result<Value> {
        let command = format!("gh {}", args[..2].join(" "));
        let output = self.output(args)?;
        if !output.status.success() {
            bail!(
                "{command} failed: {}",
                String::from_utf8_lossy(&output.stderr).trim()
            );
        }
        serde_json::from_slice(&output.stdout)
            .with_context(|| format!("{command} returned invalid JSON"))
    }
    fn output(&self, args: &[&str]) -> Result<Output> {
        process::output(
            Command::new("gh").args(args),
            None,
            Control {
                name: "gh",
                interruption: self.interruption,
                stop: &|child| process::stop(child, &[libc::SIGTERM]),
            },
        )
    }
}

/// Whether the issue `json` describes, with its `state`, is open.
fn state_is_open(json: &Value) -> Result<bool> {
    Ok(json["state"].as_str().context("gh output has no state")? == "OPEN")
}

/// An issue as an Architect run reads the issue its Architecture review
/// ended on, and as a Claim reads its issue after a Self-merge.
#[derive(Clone)]
pub struct Issue {
    pub is_open: bool,
    pub labels: Labels,
    pub created: DateTime<Utc>,
}

/// The labels of the issue `json` describes, with its `labels`.
fn labels_of(json: &Value) -> Result<Labels> {
    Ok(named(
        json["labels"]
            .as_array()
            .context("gh output has no labels")?,
    ))
}

/// The labels `labels` describe, each with its `name`.
fn named(labels: &[Value]) -> Labels {
    labels
        .iter()
        .filter_map(|label| label["name"].as_str())
        .collect()
}

/// The REST API's path for the labels of `issue`.
fn labels_path(issue: &IssueUrl) -> String {
    format!("repos/{}/issues/{}/labels", issue.repo_slug(), issue.number)
}

/// The REST API's path for `label` on `issue`.
fn label_path(issue: &IssueUrl, label: &str) -> String {
    format!("{}/{label}", labels_path(issue))
}

/// The command that does what [`GitHub::remove_label`] does, to run by hand.
pub fn remove_label_command(issue: &IssueUrl, label: Label) -> String {
    format!("gh api --method DELETE {}", label_path(issue, label.name()))
}

/// The command that adds `label` to `issue`, keeping its other labels, to
/// run by hand: unlike [`GitHub::set_labels`], it needs none of the others named.
pub fn add_label_command(issue: &IssueUrl, label: Label) -> String {
    format!(
        "gh api --method POST {} -f 'labels[]={label}'",
        labels_path(issue)
    )
}

/// A Spec's sub-issue, as a Spec run reads it.
pub struct Ticket {
    pub number: u64,
    pub is_open: bool,
    pub labels: Labels,
    /// It has sub-issues of its own.
    pub has_sub_issues: bool,
    /// The numbers of the issues it is blocked by, in the Spec or not.
    pub blockers: Vec<u64>,
    /// The numbers of those blockers that are open.
    pub open_blockers: Vec<u64>,
}

/// Every sub-issue of `issue`, open or closed, with its labels, whether it
/// has sub-issues of its own and the issues it is blocked by: its GitHub
/// "blocked by" links, never the text of its body.
const TICKETS_QUERY: &str = "\
query($owner: String!, $repo: String!, $number: Int!) {
  repository(owner: $owner, name: $repo) {
    issue(number: $number) {
      subIssues(first: 100) {
        nodes {
          number
          state
          labels(first: 100) { nodes { name } }
          subIssues { totalCount }
          blockedBy(first: 100) { nodes { number state } }
        }
      }
    }
  }
}";

/// The `nodes` of `connection`, the `what` of a GraphQL answer.
fn nodes<'a>(connection: &'a Value, what: &str) -> Result<&'a Vec<Value>> {
    connection["nodes"]
        .as_array()
        .with_context(|| format!("gh api graphql output has no {what}"))
}

/// Whether the issue a GraphQL answer's `node` describes is open.
fn node_is_open(node: &Value) -> Result<bool> {
    Ok(node["state"]
        .as_str()
        .context("gh api graphql output has an issue with no state")?
        == "OPEN")
}

/// The number of the issue a GraphQL answer's `node` describes.
fn node_number(node: &Value) -> Result<u64> {
    node["number"]
        .as_u64()
        .context("gh api graphql output has an issue with no number")
}

/// How many sub-issues the issue a GraphQL answer's `node` describes has.
fn sub_issue_count(node: &Value) -> Result<u64> {
    node["subIssues"]["totalCount"]
        .as_u64()
        .context("gh api graphql output has an issue with no subIssues count")
}

/// An issue as a listing of its repository's issues gives it.
#[derive(Debug, Clone)]
pub struct ListedIssue {
    pub issue: IssueUrl,
    pub title: String,
    pub labels: Labels,
}

/// An open issue labelled for a Pickup run to take, as the Pickup run reads
/// what its listing doesn't give.
pub struct Candidate {
    /// The issue it is a sub-issue of, if it is one.
    pub parent: Option<IssueUrl>,
    /// For each of its sub-issues, whether that one is open.
    pub sub_issue_is_open: Vec<bool>,
    /// The numbers of the open issues it is blocked by.
    pub open_blockers: Vec<u64>,
    /// The latest of the changes that shape it, if its timeline has one.
    pub last_shaped: Option<Shaped>,
}

impl Candidate {
    /// It has sub-issues of its own.
    pub fn has_sub_issues(&self) -> bool {
        !self.sub_issue_is_open.is_empty()
    }
}

/// A change that shapes an issue, and when it was made.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct Shaped {
    pub by: Shaping,
    pub at: DateTime<Utc>,
}

/// What shapes an issue for a Pickup run.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum Shaping {
    /// The label a Pickup run lists issues by was applied.
    Labelled,
    /// A sub-issue was added or removed.
    SubIssues,
    /// A "blocked by" link was added or removed.
    Blockers,
}

/// An issue's parent, the state of each of its sub-issues, the issues it is
/// blocked by, and the events of its timeline that shape it: each time a
/// label was applied, of which only the last hundred are read, and the last
/// sub-issue or "blocked by" link added or removed. They are read from the
/// timeline because adding a sub-issue does not change the issue's update
/// time. The sub-issues read are the first hundred, the ones
/// [`TICKETS_QUERY`] reads, so a Pickup run and a Spec run see the same
/// Tickets.
const CANDIDATE_QUERY: &str = "\
query($owner: String!, $repo: String!, $number: Int!) {
  repository(owner: $owner, name: $repo) {
    issue(number: $number) {
      parent { url }
      subIssues(first: 100) { nodes { state } }
      blockedBy(first: 100) { nodes { number state } }
      labelled: timelineItems(last: 100, itemTypes: [LABELED_EVENT]) {
        nodes { ... on LabeledEvent { createdAt label { name } } }
      }
      linked: timelineItems(
        last: 1
        itemTypes: [
          SUB_ISSUE_ADDED_EVENT
          SUB_ISSUE_REMOVED_EVENT
          BLOCKED_BY_ADDED_EVENT
          BLOCKED_BY_REMOVED_EVENT
        ]
      ) {
        nodes {
          __typename
          ... on SubIssueAddedEvent { createdAt }
          ... on SubIssueRemovedEvent { createdAt }
          ... on BlockedByAddedEvent { createdAt }
          ... on BlockedByRemovedEvent { createdAt }
        }
      }
    }
  }
}";

const PR_FIELDS: &str = "number,url,state,headRefName,baseRefName,isDraft";

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum PrState {
    Open,
    Closed,
    Merged,
}

impl fmt::Display for PrState {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.write_str(match self {
            PrState::Open => "open",
            PrState::Closed => "closed",
            PrState::Merged => "merged",
        })
    }
}

pub struct PullRequest {
    pub number: u64,
    pub url: String,
    pub state: PrState,
    pub head: String,
    pub base: String,
    pub is_draft: bool,
}

impl PullRequest {
    pub fn is_open(&self) -> bool {
        self.state == PrState::Open
    }

    fn from_json(json: &Value) -> Result<Self> {
        let field = |name: &str| -> Result<String> {
            json[name]
                .as_str()
                .map(String::from)
                .with_context(|| format!("gh output has no {name}"))
        };
        let state = match field("state")?.as_str() {
            "OPEN" => PrState::Open,
            "CLOSED" => PrState::Closed,
            "MERGED" => PrState::Merged,
            other => bail!("gh output has an unknown PR state {other}"),
        };
        Ok(PullRequest {
            number: json["number"].as_u64().context("gh output has no number")?,
            url: field("url")?,
            state,
            head: field("headRefName")?,
            base: field("baseRefName")?,
            is_draft: json["isDraft"]
                .as_bool()
                .context("gh output has no isDraft")?,
        })
    }
}

/// Whether a pull request can be merged into its base.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum Mergeable {
    Yes,
    /// It conflicts with its base.
    No,
    /// GitHub is still working it out.
    Unknown,
}

/// Where a check or status stands.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum CheckState {
    Pending,
    Passed,
    Failed,
}

/// A check run or a commit status.
#[derive(Clone)]
pub struct Check {
    pub name: String,
    pub state: CheckState,
    pub url: Option<String>,
    /// The GitHub Actions job it is, if it is one. No other check can be
    /// re-run: not a commit status, nor a check run of another app.
    pub job: Option<ActionsJob>,
}

/// A job of a GitHub Actions workflow run, as one of its attempts ran it.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct ActionsJob {
    /// Its check run's id, which a new attempt of the job does not keep.
    pub check_run: u64,
    /// The workflow run it belongs to.
    pub workflow_run: u64,
}

impl ActionsJob {
    /// The job whose check run is `check_run`, if `details_url`, the check
    /// run's, is a job's page: `…/actions/runs/<workflow run>/job/<job>`.
    fn of(check_run: Option<u64>, details_url: Option<&str>) -> Option<Self> {
        let (_, after) = details_url?.split_once("/actions/runs/")?;
        let (workflow_run, _) = after.split_once("/job/")?;
        Some(ActionsJob {
            check_run: check_run?,
            workflow_run: workflow_run.parse().ok()?,
        })
    }
}

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

    #[test]
    fn only_a_check_run_whose_details_are_a_jobs_page_is_an_actions_job() {
        let job = "https://github.com/acme/widgets/actions/runs/900/job/41";
        assert_eq!(
            ActionsJob::of(Some(41), Some(job)),
            Some(ActionsJob {
                check_run: 41,
                workflow_run: 900
            })
        );
        for not_a_job in [
            "https://ci.example/test",
            "https://github.com/acme/widgets/actions/runs/900",
            "https://github.com/acme/widgets/actions/runs/latest/job/41",
            "https://github.com/acme/widgets/runs/41",
        ] {
            assert_eq!(ActionsJob::of(Some(41), Some(not_a_job)), None);
        }
        assert_eq!(ActionsJob::of(Some(41), None), None);
        assert_eq!(ActionsJob::of(None, Some(job)), None);
    }
}