use super::*;

#[derive(Debug)]
pub(crate) struct CleanupPlan {
    pub path: String,
    remote: String,
    remote_url: String,
    source: String,
    target: String,
    source_sha: String,
    local_sha: Option<String>,
}

fn clean_worktree(repo: &Path) -> Result<(), String> {
    let status = status_for_repo(repo)?;
    if !status.clean
        || status.merge_in_progress
        || status.rebase_in_progress
        || status.cherry_pick_in_progress
    {
        return Err("Commit or stash local changes and finish pending Git operations before merging with branch cleanup.".into());
    }
    Ok(())
}

fn validate_branch(repo: &Path, branch: &str) -> Result<(), String> {
    if branch.is_empty() || branch.starts_with('-') {
        return Err("Invalid review branch.".into());
    }
    run_git(repo, ["check-ref-format", &format!("refs/heads/{branch}")])?;
    Ok(())
}

fn branch_sha(repo: &Path, branch: &str) -> Result<Option<String>, String> {
    let refs = run_git(
        repo,
        [
            "for-each-ref",
            "--format=%(refname) %(objectname)",
            &format!("refs/heads/{branch}"),
        ],
    )?;
    Ok(String::from_utf8_lossy(&refs).lines().find_map(|line| {
        let (reference, sha) = line.split_once(' ')?;
        (reference == format!("refs/heads/{branch}")).then(|| sha.to_string())
    }))
}

fn unused_in_other_worktrees(repo: &Path, branch: &str, allow_current: bool) -> Result<(), String> {
    let output = run_git(repo, ["worktree", "list", "--porcelain"])?;
    let current = fs::canonicalize(repo).map_err(|err| err.to_string())?;
    for entry in String::from_utf8_lossy(&output).split("\n\n") {
        if entry
            .lines()
            .any(|line| line == format!("branch refs/heads/{branch}"))
        {
            let path = entry
                .lines()
                .find_map(|line| line.strip_prefix("worktree "));
            if !allow_current
                || path.and_then(|path| fs::canonicalize(path).ok()).as_ref() != Some(&current)
            {
                return Err(format!(
                    "Branch '{branch}' is checked out in another worktree. No branch was deleted."
                ));
            }
        }
    }
    Ok(())
}

// Compare server-provided clone URLs exactly apart from trailing slash/.git.
// Never infer a destructive target from just a repository or branch name.
fn same_url(left: &str, right: &str) -> bool {
    fn clean(value: &str) -> &str {
        value.trim().trim_end_matches('/').trim_end_matches(".git")
    }
    clean(left) == clean(right)
}

fn check_remote(repo: &Path, remote: &str, urls: &[String]) -> Result<String, String> {
    let fetch = run_git(repo, ["remote", "get-url", "--all", remote])?;
    let push = run_git(repo, ["remote", "get-url", "--push", "--all", remote])?;
    let fetch = String::from_utf8_lossy(&fetch);
    let push = String::from_utf8_lossy(&push);
    if fetch.lines().count() != 1
        || push.lines().count() != 1
        || !fetch
            .lines()
            .chain(push.lines())
            .all(|url| urls.iter().any(|expected| same_url(url, expected)))
    {
        return Err(
            "The local remote's fetch and push URLs must both match the PR repository.".into(),
        );
    }
    Ok(fetch.trim().to_string())
}

fn ancestor(repo: &Path, older: &str, newer: &str) -> bool {
    run_git(repo, ["merge-base", "--is-ancestor", older, newer]).is_ok()
}

pub(crate) fn prepare(
    path: &str,
    source: &str,
    target: &str,
    source_sha: &str,
    urls: &[String],
    username: &str,
    token: &str,
) -> Result<CleanupPlan, String> {
    let repo = resolve_repo(path)?;
    validate_branch(&repo, source)?;
    validate_branch(&repo, target)?;
    if source == target {
        return Err("Source and target branch must differ.".into());
    }
    if !matches!(source_sha.len(), 40 | 64)
        || !source_sha.bytes().all(|byte| byte.is_ascii_hexdigit())
    {
        return Err("The provider did not return a valid PR source commit.".into());
    }
    clean_worktree(&repo)?;
    unused_in_other_worktrees(&repo, source, true)?;
    unused_in_other_worktrees(&repo, target, true)?;
    let remotes = run_git(&repo, ["remote"])?;
    let (remote, remote_url) = String::from_utf8_lossy(&remotes).lines()
        .find_map(|remote| check_remote(&repo, remote, urls).ok().map(|url| (remote.to_string(), url)))
        .ok_or("Open the local repository matching this PR, with a matching fetch and push remote, before enabling branch cleanup.")?;
    run_git_authenticated(
        &repo,
        [
            "fetch",
            "--no-tags",
            &remote_url,
            &format!("+refs/heads/{source}:refs/remotes/{remote}/{source}"),
            &format!("+refs/heads/{target}:refs/remotes/{remote}/{target}"),
        ],
        username,
        token,
    )?;
    if verify_commit(&repo, &format!("refs/remotes/{remote}/{source}"))? != source_sha {
        return Err("The PR source branch changed. Refresh the PR before merging.".into());
    }
    let local_sha = branch_sha(&repo, source)?;
    if local_sha
        .as_ref()
        .is_some_and(|sha| !ancestor(&repo, sha, source_sha))
    {
        return Err("The local source branch contains commits outside this PR. Push or preserve them before enabling cleanup.".into());
    }
    if branch_sha(&repo, target)?
        .as_ref()
        .is_some_and(|sha| !ancestor(&repo, sha, &format!("refs/remotes/{remote}/{target}")))
    {
        return Err("The local target branch has diverged or contains unpushed commits. Synchronize it before enabling cleanup.".into());
    }
    Ok(CleanupPlan {
        path: repo.to_string_lossy().into_owned(),
        remote,
        remote_url,
        source: source.into(),
        target: target.into(),
        source_sha: source_sha.into(),
        local_sha,
    })
}

pub(crate) fn finish(plan: &CleanupPlan, username: &str, token: &str) -> Result<(), String> {
    let repo = resolve_repo(&plan.path)?;
    clean_worktree(&repo)?;
    // A changed remote config must not redirect cleanup after the merge.
    let current_fetch = remote_url_for(&repo, &plan.remote).unwrap_or_default();
    if !same_url(&current_fetch, &plan.remote_url) {
        return Err("The local remote changed; branch cleanup was stopped.".into());
    }
    if branch_sha(&repo, &plan.source)? != plan.local_sha {
        return Err("The local source branch changed during the merge; it was preserved.".into());
    }
    unused_in_other_worktrees(&repo, &plan.source, true)?;
    unused_in_other_worktrees(&repo, &plan.target, true)?;
    let target_ref = format!("refs/remotes/{}/{}", plan.remote, plan.target);
    run_git_authenticated(
        &repo,
        [
            "fetch",
            "--no-tags",
            &plan.remote_url,
            &format!("+refs/heads/{}:{target_ref}", plan.target),
        ],
        username,
        token,
    )?;
    if let Some(local_target) = branch_sha(&repo, &plan.target)? {
        if !ancestor(&repo, &local_target, &target_ref) {
            return Err("The local target branch has diverged; branches were preserved.".into());
        }
        run_git(&repo, ["checkout", &plan.target])?;
        run_git(&repo, ["merge", "--ff-only", &target_ref])?;
    } else {
        run_git(
            &repo,
            ["checkout", "--track", "-b", &plan.target, &target_ref],
        )?;
    }
    clean_worktree(&repo)?;
    let source_ref = format!("refs/heads/{}", plan.source);
    let remote_heads = run_git_authenticated(
        &repo,
        ["ls-remote", "--heads", &plan.remote_url, &source_ref],
        username,
        token,
    )?;
    if let Some(sha) = String::from_utf8_lossy(&remote_heads)
        .lines()
        .find_map(|line| {
            let (sha, reference) = line.split_once('\t')?;
            (reference == source_ref).then_some(sha)
        })
    {
        if sha != plan.source_sha {
            return Err("The remote source branch has new commits; it was preserved.".into());
        }
        run_git_authenticated(
            &repo,
            [
                "push",
                &format!("--force-with-lease={source_ref}:{}", plan.source_sha),
                &plan.remote_url,
                &format!(":{source_ref}"),
            ],
            username,
            token,
        )?;
    }
    if let Some(local_sha) = &plan.local_sha {
        unused_in_other_worktrees(&repo, &plan.source, false)?;
        // Expected-old-value deletion is safe even after squash/rebase, and rejects concurrent updates.
        run_git(&repo, ["update-ref", "-d", &source_ref, local_sha])?;
        if git_config_value(&repo, &format!("branch.{}.remote", plan.source)).is_some() {
            run_git(
                &repo,
                [
                    "config",
                    "--remove-section",
                    &format!("branch.{}", plan.source),
                ],
            )?;
        }
    }
    let tracking_ref = format!("refs/remotes/{}/{}", plan.remote, plan.source);
    // Do not remove a tracking ref that was advanced concurrently.
    run_git(&repo, ["update-ref", "-d", &tracking_ref, &plan.source_sha])?;
    Ok(())
}

#[cfg(test)]
mod tests {
    use super::*;
    struct Fixture {
        root: PathBuf,
        local: PathBuf,
        server: PathBuf,
        remote: String,
    }
    impl Drop for Fixture {
        fn drop(&mut self) {
            let _ = fs::remove_dir_all(&self.root);
        }
    }
    impl Fixture {
        fn new() -> Self {
            static NEXT: AtomicU64 = AtomicU64::new(0);
            let root = env::temp_dir().join(format!(
                "gitty-review-cleanup-{}-{}",
                std::process::id(),
                NEXT.fetch_add(1, Ordering::Relaxed)
            ));
            fs::create_dir_all(&root).unwrap();
            let local = root.join("local");
            let server = root.join("server");
            let remote = root.join("remote.git").to_string_lossy().into_owned();
            run_git(&root, ["init", "--bare", &remote]).unwrap();
            run_git(&root, ["init", "-b", "release", local.to_str().unwrap()]).unwrap();
            run_git(&local, ["config", "user.name", "QA"]).unwrap();
            run_git(&local, ["config", "user.email", "qa@example.test"]).unwrap();
            run_git(&local, ["config", "commit.gpgsign", "false"]).unwrap();
            run_git(&local, ["commit", "--allow-empty", "-m", "base"]).unwrap();
            run_git(&local, ["remote", "add", "origin", &remote]).unwrap();
            run_git(&local, ["push", "-u", "origin", "release"]).unwrap();
            run_git(&local, ["checkout", "-b", "feature"]).unwrap();
            fs::write(local.join("feature.txt"), "feature").unwrap();
            run_git(&local, ["add", "."]).unwrap();
            run_git(&local, ["commit", "-m", "feature"]).unwrap();
            run_git(&local, ["push", "-u", "origin", "feature"]).unwrap();
            run_git(
                &root,
                ["clone", "-b", "release", &remote, server.to_str().unwrap()],
            )
            .unwrap();
            run_git(&server, ["config", "user.name", "QA"]).unwrap();
            run_git(&server, ["config", "user.email", "qa@example.test"]).unwrap();
            run_git(&server, ["config", "commit.gpgsign", "false"]).unwrap();
            Self {
                root,
                local,
                server,
                remote,
            }
        }
        fn plan(&self) -> Result<CleanupPlan, String> {
            let sha = verify_commit(&self.local, "refs/remotes/origin/feature")?;
            prepare(
                self.local.to_str().unwrap(),
                "feature",
                "release",
                &sha,
                &[self.remote.clone()],
                "",
                "",
            )
        }
        fn merge(&self, squash: bool) {
            if squash {
                run_git(&self.server, ["merge", "--squash", "origin/feature"]).unwrap();
                run_git(&self.server, ["commit", "-m", "squashed PR"]).unwrap();
            } else {
                run_git(
                    &self.server,
                    ["merge", "--no-ff", "-m", "merged PR", "origin/feature"],
                )
                .unwrap();
            }
            run_git(&self.server, ["push", "origin", "release"]).unwrap();
        }
        fn remote_source_exists(&self) -> bool {
            !run_git(
                &self.local,
                ["ls-remote", "--heads", "origin", "refs/heads/feature"],
            )
            .unwrap()
            .is_empty()
        }
    }
    #[test]
    fn review_cleanup_switches_to_actual_target_and_deletes_after_merge_and_squash() {
        for squash in [false, true] {
            let fixture = Fixture::new();
            let plan = fixture.plan().unwrap();
            fixture.merge(squash);
            finish(&plan, "", "").unwrap();
            assert_eq!(
                status_for_repo(&fixture.local)
                    .unwrap()
                    .current_branch
                    .as_deref(),
                Some("release")
            );
            assert_eq!(
                verify_commit(&fixture.local, "HEAD").unwrap(),
                verify_commit(&fixture.server, "HEAD").unwrap()
            );
            assert!(branch_sha(&fixture.local, "feature").unwrap().is_none());
            assert!(!fixture.remote_source_exists());
            assert!(git_config_value(&fixture.local, "branch.feature.remote").is_none());
        }
    }
    #[test]
    fn review_cleanup_accepts_server_auto_deletion_and_missing_local_target() {
        let fixture = Fixture::new();
        run_git(&fixture.local, ["branch", "-D", "release"]).unwrap();
        let plan = fixture.plan().unwrap();
        fixture.merge(true);
        run_git(&fixture.server, ["push", "origin", "--delete", "feature"]).unwrap();
        finish(&plan, "", "").unwrap();
        assert_eq!(
            status_for_repo(&fixture.local)
                .unwrap()
                .current_branch
                .as_deref(),
            Some("release")
        );
        assert!(branch_sha(&fixture.local, "feature").unwrap().is_none());
    }
    #[test]
    fn review_cleanup_preserves_dirty_and_unpushed_local_work() {
        let fixture = Fixture::new();
        fs::write(fixture.local.join("untracked.txt"), "keep").unwrap();
        assert!(fixture.plan().unwrap_err().contains("Commit or stash"));
        fs::remove_file(fixture.local.join("untracked.txt")).unwrap();
        run_git(
            &fixture.local,
            ["commit", "--allow-empty", "-m", "unpushed"],
        )
        .unwrap();
        assert!(fixture.plan().unwrap_err().contains("outside this PR"));
        assert!(fixture.remote_source_exists());
    }
    #[test]
    fn review_cleanup_preserves_concurrent_local_or_remote_commits() {
        for local in [false, true] {
            let fixture = Fixture::new();
            let plan = fixture.plan().unwrap();
            fixture.merge(true);
            if local {
                run_git(
                    &fixture.local,
                    ["commit", "--allow-empty", "-m", "new local work"],
                )
                .unwrap();
            } else {
                run_git(&fixture.server, ["checkout", "feature"]).unwrap();
                run_git(
                    &fixture.server,
                    ["commit", "--allow-empty", "-m", "new remote work"],
                )
                .unwrap();
                run_git(&fixture.server, ["push", "origin", "feature"]).unwrap();
            }
            assert!(finish(&plan, "", "").is_err());
            assert!(branch_sha(&fixture.local, "feature").unwrap().is_some());
            assert!(fixture.remote_source_exists());
        }
    }
    #[test]
    fn review_cleanup_rejects_other_push_repository_and_busy_worktrees() {
        let fixture = Fixture::new();
        run_git(
            &fixture.local,
            [
                "remote",
                "set-url",
                "--push",
                "origin",
                "/tmp/different-repository.git",
            ],
        )
        .unwrap();
        assert!(fixture.plan().is_err());
        run_git(
            &fixture.local,
            ["remote", "set-url", "--push", "origin", &fixture.remote],
        )
        .unwrap();
        let linked = fixture.root.join("linked");
        run_git(
            &fixture.local,
            ["worktree", "add", linked.to_str().unwrap(), "release"],
        )
        .unwrap();
        assert!(fixture.plan().unwrap_err().contains("another worktree"));
        assert!(fixture.remote_source_exists());
    }
}